Search

Reactive N-hydroxy-9-azabicyclo[3.3.1]nonane (ABNOH) linked 2'-deoxyuridine 5'-O-mono- and triphosphates were synthesized through a CuAAC reaction of ABNOH-PEG 4 -N 3 with 5-ethynyl-dUMP or -dUTP. The modified triphosphate was used as substrate for enzymatic synthesis of modified DNA probes with KOD XL DNA polymerase. The keto-ABNO radical reacted with tryptophan (Trp) and Trp-containing peptides to form a stable tricyclic fused hexahydropyrrolo-indole conjugates. Similarly modified ABNOH-linked nucleotides reacted with Trp-containing peptides to form a stable conjugate in the presence but surprisingly even in the absence of NaNO 2 (presumably through activation by O 2 ). The reactive ABNOH-modified DNA probe was used for bioconjugations and crosslinking with Trp-containing peptides or proteins., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

A 5-day test duration makes BOD 5 measurement unsatisfactory and hinders the development of a quick technique. Protein-like fluorescence peaks show a strong correlation between the BOD characteristics and the fluorescence intensities. For identifying and measuring BOD in surface water, a simultaneous absorbance-transmittance and fluorescence excitation-emission matrices (A-TEEM) method combined with PARAFAC (parallel factor) and PLS (partial least squares) analyses was developed using a tyrosine and tryptophan (tyr-trpt) mix as a surrogate analyte for BOD. The use of a surrogate analyte was decided upon due to lack of fluorescent BOD standards. Tyr-trpt mix standard solutions were added to surface water samples to prepare calibration and validation samples. PARAFAC analysis of excitation-emission matrices detected the tyr-trpt mix in surface water. PLS modelling demonstrated significant linearity (R 2  = 0.991) between the predicted and measured tyr-trypt mix concentrations, and accuracy and robustness were all acceptable per the ICH Q2 (R2) and ASTM multivariate calibration/validation procedures guidelines. Based on a suitable and workable surrogate analyte method, these results imply that BOD can be detected and quantified using the A-TEEM-PARAFAC-PLS method. Very positive comparability between tyr-trypt mix concentrations was found, suggesting that tyr-trypt mix might eventually take the place of a BOD-based sampling protocol. Overall, this approach offers a novel tool that can be quickly applied in water treatment plant settings and is a step in supporting the trend toward rapid BOD determination in waters. Further studies should demonstrate the wide application of the method using real wastewater samples from various water treatment facilities., (© 2024. The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry.)

The effectiveness of ozonation, one of the techniques known for destroying organic contaminants from wastewater, depends on the composition of the wastewater matrix. The required ozone (O 3 ) dose is determined based on the target compounds during ozonation. Hydroxyl radicals are quantified using a probe compound. The para-chlorobenzoic acid (pCBA) is typically used as a probe compound to measure hydroxyl radicals. However, real-time measurement is impossible, as the analysis process consumes time and resources. This study aimed to evaluate the spectroscopic characteristics of various organic substances in wastewater ozonation through fluorescence excitation-emission matrix and parallel factor analysis. The study also demonstrated that real-time analyzable tryptophan-like fluorescence (TLF) can be used as a hydroxyl radical index. Importantly, the correlation between para-chlorobenzoic acid and TLF was derived, and the results showed a high correlation (R 2  = 0.91), confirming the reliability of our findings. Seven trace organic compounds, classified based on their reactivity with O 3 and hydroxyl radicals, were selected as target compounds and treated with O 3 . The TLF index was used as a model factor for the removal rate of the target compounds. The experimental and model values matched when the O 3 dose was below 1.0 g O 3 /g DOC (RMSE: 0.0445-0.0895)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

It is a fluorescence-based study to examine the interaction between L-tryptophan and a selection of aldehydes, namely furfural (furan-2-carbaldehyde), 3-hydroxybenzaldehyde, salicylaldehyde (2-hydroxybenzaldehyde), 3-nitrobenzaldehyde, and 4-bromobenzaldehyde. The investigation took place in an aqueous environment, revealing that all five aldehydes induced quenching of the fluorescence intensity of L-tryptophan. By employing the Stern-Volmer equation to describe the quenching process, we constructed Stern-Volmer plots and derived Stern-Volmer constants. These constants (K SV ) ranged from 2.87 × 10 4  mol L - 1 to 5.75 × 10 4  mol L - 1 . Notably, the values of the Stern-Volmer constants varied among the different aldehydes, with the following order: 3-hydroxybenzaldehyde(3-HBA) > 4-bromobenzaldehyde (4-BBA) > 3-nitrobenzaldehyde > furan-2-carbaldehyde > salicylaldehyde. Consequently, our findings highlighted 3-hydroxybenzaldehyde as the most potent quencher, while 2-hydroxybenzaldehyde displayed the least sensitivity to quenching. Additionally, we determined the detection and quantification limits for the investigated aldehydes, resulting in ranges of 3.87 × 10 - 12 to 8.25 × 10 - 6 and 1.29 × 10 - 11 to 2.75 × 10 - 5 , respectively. This research paves the way for the development of novel fluorescence probe-based sensors and offers valuable techniques for analyzing aldehydes within environmental and biological samples., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Microorganisms are known to be a promising source of biopigments because they are easy to obtain, can be produced on a commercial scale, and are environmentally friendly. Therefore, the aim of this work was to characterize a brown pigment (BP) produced by HM053 in NFbHPN-lactate medium. The BP was extracted from the pellet (BPP) or supernatant (BPS), in the presence (BPPTrp, BPSTrp) or absence (BPPw, BPSw) of tryptophan (Trp). The UV-vis results were similar among all BP samples and compared with commercial melanin used as a standard, and the maximum absorption was observed around 200-220 nm. FTIR spectra showed that BP and commercial melanin had slight differences, with a small band between 3000-2840 cm - 1 , related to C-H in the CH 2 and CH 3 aliphatic groups, which is not observed in the commercial melanin. Between BPP and BPS showed a different structure with bands in the region 1230-1070 cm - 1 related to groups C-O. The thermogravimetric curves for BPSw and BPSTrp showed similar behavior, with 4 stages of mass loss. The similarity between BPPw and BPPTrp with 2 stages of mass loss was also observed. Scanning electron microscopy results showed morphological differences between BPP and BPS, where BPP had a physical structure more homogeneous and a regular flat surface, while the BPS physical structure did not seem homogeneous and the surface was uneven with some spherical structures as commercial melanin., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

In NMR spectroscopy of biomolecular systems, the use of fluorine-19 probes benefits from a clean background and high sensitivity. Therefore, 19 F-labeling procedures are of wide-spread interest. Here, we use 5-fluoroindole as a precursor for cost-effective residue-specific introduction of 5-fluorotryptophan (5F-Trp) into G protein-coupled receptors (GPCRs) expressed in Pichia pastoris. The method was successfully implemented with the neurokinin 1 receptor (NK1R). The 19 F-NMR spectra of 5F-Trp-labeled NK1R showed one well-separated high field-shifted resonance, which was assigned by mutational studies to the "toggle switch tryptophan". Residue-selective labeling thus enables site-specific investigations of this functionally important residue. The method described here is inexpensive, requires minimal genetic manipulation and can be expected to be applicable for yeast expression of GPCRs at large., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

A potential source of novel biomarkers for mTBI is the kynurenine pathway (KP), a metabolic pathway of tryptophan (Trp), that is up-regulated by neuroinflammation and stress. Considering that metabolites of the KP (kynurenines) are implicated in various neuropsychiatric diseases, exploration of this pathway could potentially bridge the gap between physiological and psychological factors in the recovery process after mTBI. This study, therefore, set out to characterize the KP after mTBI and to examine associations with long-term outcome. Patients were prospectively recruited at the emergency department (ED), and blood samples were obtained in the acute phase (<24 h; N = 256) and at 1-month follow-up (N = 146). A comparison group of healthy controls (HC; N = 32) was studied at both timepoints. Trp, kynurenines, and interleukin (IL)-6 and IL-10 were quantified in plasma. Clinical outcome was measured at six months post-injury. Trp, xanthurenic acid (XA), and picolinic acid (PA) were significantly reduced in patients with mTBI relative to HC, corrected for age and sex. For Trp (d = -0.57 vs. d = -0.29) and XA (d = -0.98 vs. d = -0.32), larger effects sizes were observed during the acute phase compared to one-month follow-up, while for PA (d = -0.49 vs. d = -0.52) effect sizes remained consistent. Findings for other kynurenines (e.g., kynurenine, kynurenic acid, and quinolinic acid) were non-significant after correction for multiple testing. Within the mTBI group, lower acute Trp levels were significantly related to incomplete functional recovery and higher depression scores at 6 months post-injury. No significant relationships were found for Trp, XA, and PA with IL-6 or IL-10 concentrations. In conclusion, our findings indicate that perturbations of the plasma KP in the hyperacute phase of mTBI and 1 month later are limited to the precursor Trp, and glutamate system modulating kynurenines XA and PA. Correlations between acute reductions of Trp and unfavorable outcomes may suggest a potential substrate for pharmacological intervention., (© 2024 The Author(s). Journal of Neurochemistry published by John Wiley & Sons Ltd on behalf of International Society for Neurochemistry.)

Tryptophan (Trp) metabolism plays a vital role in cancer immunity. Indoleamine 2.3-dioxygenase 1 (IDO1), is a crucial enzyme in the metabolic pathway by which Trp is degraded to kynurenine (Kyn). IDO1-mediated Trp metabolites can inhibit tumor immunity and facilitate immune evasion by cancer cells; thus, targeting IDO1 is a potential tumor immunotherapy strategy. Recently, numerous IDO1 inhibitors have been introduced into clinical trials as immunotherapeutic agents for cancer treatment. However, drawbacks such as low oral bioavailability, slow onset of action, and high toxicity are associated with these drugs. With the continuous development of nanotechnology, medicine is gradually entering an era of precision healthcare. Nanodrugs carried by inorganic, lipid, and polymer nanoparticles (NPs) have shown great potential for tumor therapy, providing new ways to overcome tumor diversity and improve therapeutic efficacy. Compared to traditional drugs, nanomedicines offer numerous significant advantages, including a prolonged half-life, low toxicity, targeted delivery, and responsive release. Moreover, based on the physicochemical properties of these nanomaterials (eg, photothermal, ultrasonic response, and chemocatalytic properties), various combination therapeutic strategies have been developed to synergize the effects of IDO1 inhibitors and enhance their anticancer efficacy. This review is an overview of the mechanism by which the Trp-IDO1-Kyn pathway acts in tumor immune escape. The classification of IDO1 inhibitors, their clinical applications, and barriers for translational development are discussed, the use of IDO1 inhibitor-based nanodrug delivery systems as combination therapy strategies is summarized, and the issues faced in their clinical application are elucidated. We expect that this review will provide guidance for the development of IDO1 inhibitor-based nanoparticle nanomedicines that can overcome the limitations of current treatments, improve the efficacy of cancer immunotherapy, and lead to new breakthroughs in the field of cancer immunotherapy., Competing Interests: The authors report no conflicts of interest in this work., (© 2024 Jiang et al.)

Human tryptophan dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) are two important targets in cancer immunotherapy. Extensive research has led to a large number of potent IDO inhibitors; in addition, 52 structures of IDO in complex with inhibitors with a wide array of chemical scaffolds have been documented. In contrast, progress in the development of TDO inhibitors has been limited. Only four structures of TDO in complex with competitive inhibitors that compete with the substrate L-tryptophan for binding to the active site have been reported to date. Here we systematically evaluated the structures of TDO in complex with competitive inhibitors with three types of pharmacophores, imidazo-isoindole, indole-tetrazole, and indole-benzotriazole. The comparative assessment of the protein-inhibitor interactions sheds new light into the structure-based design of enzyme-selective inhibitors.

Background: A successful immune response against tumors depends on various cellular processes. Hence, there is an urgent need to construct a proficient nanoplatform for immunotherapy that can concurrently regulate the activities of various cells participating in the immune process. We have developed zeolitic imidazolate framework-8 (ZIF-8) formula, with good pH sensitivity, which is conducive to the release of drugs in the tumor site (acidic environment) and significantly improves immunotherapy. This is achieved through the coordinated action of different therapeutic agents, such as the photothermal agent polydopamine (PDA), the chemodrug camptothecin (CPT), and the immunomodulator 1-methyl-D-tryptophan (1-MT)., Materials and Methods: In this study, we evaluated the antitumor effect of PDA/(CPT + 1-MT) @ZIF-8 (PCMZ) nanoparticles (NPs) in vitro and in vivo and investigated the molecular mechanism of PCMZ NPs in tumor suppression via photothermal-chemo-immunotherapy., Results: MTT and Annexin V-FITC/PI double staining apoptosis test showed that PCMZ NPs could induce apoptosis of 4T1 cell, and PCMZ NPs could cause 4T1 cell necrosis under 808 nm laser irradiation. The objective is to establish a unilateral breast cancer model in mice and investigate the effect of PCMZ NPs on tumor growth and tumor suppression in tumor bearing mice. The results showed that PCMZ NPs showed good heating effect in vivo and effectively inhibited tumor growth under 808 nm laser irradiation. In addition, PCMZ NPs could induce the immunogenic death of tumor cells, promote the maturation of DCs, inhibit IDO pathway, and finally differentiate T cells into cytotoxic T cells and helper T cells, so as to effectively activate the anti-tumor immune response., Conclusion: The PCMZ NPs, possessing good photothermal conversion capabilities due to join of PDA, effectively overcome two main challenges in immunotherapy: insufficient stimulation of the immune response and evasion of the immune system. This provides a robust platform against invasive cancer and recurrent tumors., Competing Interests: The authors report no conflicts of interest in this work., (© 2024 Su et al.)

Viscosin is a membrane-permeabilizing, cyclic lipopeptide (CLiP) produced by Pseudomonas species. Here, we have studied four synthetic analogs (L1W, V4W, L5W, and L7W), each with one leucine (Leu; L) or valine residue exchanged for tryptophan (Trp; W) by means of time-resolved fluorescence spectroscopy of Trp. To this end, we recorded the average fluorescence lifetime, rotational correlation time and limiting anisotropy, dipolar relaxation time and limiting extent of relaxation, rate constant of acrylamide quenching, effect of H 2 O-D 2 O exchange, and time-resolved half-width of the spectrum in the absence and presence of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) liposomes. Structure, localization, and hydration of the peptides were described by molecular dynamics simulations. The combination of the parameters provides a good description of the molecular environments of the Trp positions and the behavior of viscosin as a whole. Of particular value for characterizing the impact of viscosin on the membrane is the dipolar relaxation of Trp4 in V4W, which is deeply embedded in the hydrophobic core. The limiting relaxation level represents the membrane perturbation-unlike typical membrane probes-at the site of the perturbant. Fractions of Trp4 relax at different rates; the one not in contact with water upon excitation relaxes via recruitment of a water molecule on the 10-ns timescale. This rate is sensitive to the concerted membrane perturbation by more than one lipopeptide, which appears at high lipopeptide concentration and is assumed a prerequisite for the final formation of a membrane-permeabilizing defect. Trp7 relaxes primarily with respect to neighboring Ser residues. Trp5 flips between a membrane-inserted and surface-exposed orientation., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

This Concept short review offers an insightful analysis of pivotal research papers and explores the key synthetic ideas behind the intersection of two realms in peptide chemistry: using tryptophan and Petasis multicomponent reactions for macrocyclisation and labelling of peptides. The recently published tryptophan-mediated Petasis reaction (TMPR) concept represents a critical junction between these two worlds, highlighting how combining such methodologies leads to more effective and versatile synthetic strategies, setting a potentially new direction for future research in the field of peptide-drug conjugates., (© 2024 The Authors. ChemMedChem published by Wiley-VCH GmbH.)

Tryptophan(Trp) is being explored as a potential biomarker for various diseases associated with decreased tryptophan levels; however, metabolomic methods are expensive and time-consuming and require extensive sample analysis, making them urgently needed for trace detection. To exploit the properties of Ti 3 C 2 MXenes a rational porous methyl orange (MO)-delaminated Ti 3 C 2 MXene was prepared via a facile mixing process for the electrocatalytic oxidation of Trp. The hollow-like 3D structure with a more open structure and the synergistic effect of MO and conductive Ti 3 C 2 MXene enhanced its electrochemical catalytic capability toward Trp biosensing. More importantly, MO can stabilize Ti 3 C 2 MXene nanosheets through noncovalent π-π interactions and hydrogen bonding. Compared with covalent attachment, these non-covalent interactions preserve the electronic conductivity of the Ti 3 C 2 MXene nanosheets. Finally, the addition of MO-derived nitrogen (N) and sulfur (S) atoms to Ti 3 C 2 MXene enhanced the electronegativity and improved its affinity for specific molecules, resulting in high-performance electrocatalytic activity. The proposed biosensor exhibited a wide linear response in concentration ranges of 0.01-0.3 µM and 0.5-120 µM, with a low detection limit of 15 nM for tryptophan detection, and high anti-interference ability in complex media of human urine and egg white matrices. The exceptional abilities of the MO/Ti 3 C 2 nanocatalyst make it a promising electrode material for the detection of important biomolecules., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

L-Tryptophan (L-Trp) is essential for the human body and can only be obtained externally. It is important to develop a method to efficiently detect L-Trp in food. In this work, ionic liquid (IL) modified poly(3,4-ethylendioxythiophene)/ Titanium carbide (PEDOT/Ti 3 C 2 T X ) was used as a substrate material to improve detection sensitivity. Molecular imprinted polymers (MIP) film for specific recognition of L-Trp was fabricated on the surface of modified electrodes using electrochemical polymerization. The monitoring results showed that the molecularly imprinted electrochemical sensors (MIECS) exhibited good linearity ranges (10 -6 - 0.1 μM and 0.1-100 μM) with a low detection limit (LOD) of 2.09 × 10 -7  μM. In addition, the MIECS exhibited remarkable stability, reproducibility, and immunity to interference. A good recovery (93.54-99.59%) was demonstrated in the detection of milk. The sensor was expected to be developed as a highly selective and sensitive portable assay, and applied to the detection of L-Trp in food., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Assessing membrane protein stability is among the major challenges in protein science due to their inherent complexity, which complicates the application of conventional biophysical tools. In this work, sodium dodecyl sulfate-induced denaturation of AfCopA, a Cu(I)-transport ATPase from Archaeoglobus fulgidus, was explored using a combined model-free spectral phasor analysis and a model-dependent thermodynamic analysis. Decrease in tryptophan and 1-anilino-naphthalene-8-sulfonate fluorescence intensity, displacements in the spectral phasor space, and the loss of ATPase activity were reversibly induced by this detergent. Refolding from the SDS-induced denatured state yields an active enzyme that is functionally and spectroscopically indistinguishable from the native state of the protein. Phasor analysis of Trp spectra allowed us to identify two intermediate states in the SDS-induced denaturation of AfCopA, a result further supported by principal component analysis. In contrast, traditional thermodynamic analysis detected only one intermediate state, and including the second one led to overparameterization. Additionally, ANS fluorescence spectral analysis detected one more intermediate and a gradual change at the level of the hydrophobic transmembrane surface of the protein. Based on this evidence, a model for acquiring the native structure of AfCopA in a membrane-like environment is proposed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The simple (self-)coacervation of the minimal tryptophan/arginine peptide sequences W 2 R 2 and W 3 R 3 was observed in salt-free aqueous solution. The phase diagrams were mapped using turbidimetry and optical microscopy, and the coacervate droplets were imaged using confocal microscopy complemented by cryo-TEM to image smaller droplets. The droplet size distribution and stability were probed using dynamic light scattering, and the droplet surface potential was obtained from zeta potential measurements. SAXS was used to elucidate the structure within the coacervate droplets, and circular dichroism spectroscopy was used to probe the conformation of the peptides, a characteristic signature for cation-π interactions being present under conditions of coacervation. These observations were rationalized using a simple model for the Rayleigh stability of charged coacervate droplets, along with atomistic molecular dynamics simulations which provide insight into stabilizing π-π stacking interactions of tryptophan as well as arginine-tryptophan cation-π interactions (which modulate the charge of the tryptophan π-electron system). Remarkably, the dipeptide WR did not show simple coacervation under the conditions examined, but complex coacervation was observed in mixtures with ATP (adenosine triphosphate). The electrostatically stabilized coacervation in this case provides a minimal model for peptide/nucleotide membraneless organelle formation. These are among the simplest model peptide systems observed to date able to undergo either simple or complex coacervation and are of future interest as protocell systems.

Tryptophan (an essential amino acid) and its clinically important metabolite-kynurenine contribute to several fundamental biological processes and methods that allow their determination in biological samples are in demand. The novelty of the work was a demonstration of the utility of two polymers: 4-vinylpyridine crosslinked with trimethylolpropane trimethacrylate (poly(4VP-co-TRIM)) or 1,4-dimethacryloyloxybenzene (poly(4VP-co-14DMB))-in terms of human serum clean-up for simultaneous LC-MS determination of tryptophan and kynurenine. The goal was to achieve a reduction of the matrix effect, which is responsible for signal suppression, with minimal capture of analytes. The adsorption properties of the polymeric beads were studied by evaluating the adsorption kinetics and isotherms in model matrices. Therefore, the adsorption capacities of both molecules were not efficient, the tested 4-vinylpyridine-based copolymers have shown great promise (especially poly(4VP-co-TRIM)) as sorbents for serum clean-up. In the model human serum matrix, poly(4VP-co-TRIM) provided good recoveries of tryptophan and kynurenine (76% and 87%, respectively) and allowed for the reduction of the matrix effect. Performances of both copolymers were compared to those of commercially available sorbents (octadecylsilane, activated charcoal, and primary secondary amine)., (© 2024. The Author(s).)

Monitoring the levels of L-Tryptophan (L-Trp) in body fluids is crucial due to its significant role in metabolism and protein synthesis, which ultimately affects neurological health. Herein, we have developed a novel magneto-responsive electrochemical enantioselective sensor for the recognition of L-Trp based on oriented biochar derived from Loofah, Fe 3 O 4 nanoparticles, and molecularly imprinted polydopamine (MIPDA) in xanthan hydrogel. The successful synthesis of these materials has been confirmed through physicochemical and electrochemical characterization. Various operational factors such as pH, response time, loading sample volume, and loading of active materials were optimized. As a result, the sensor exhibited an affordable linear range of 1.0-60.0 μM, with a desirable limit of detection of 0.44 μM. Furthermore, the proposed electrochemical sensor demonstrated good reproducibility and desirable selectivity for the determination of L-Trp, making it suitable for analyzing L-Trp levels in human plasma and serum samples. The development presented offers an appealing, easily accessible, and efficient strategy. It utilizes xanthan hydrogel to improve mass transfer and adhesion, biochar-stabilized Fe 3 O 4 to facilitate magnetic orientation and accelerate mass transfer and sensitivity, and polydopamine MIP to enhance selectivity. This approach enables on-site evaluation of L-Trp levels, which holds significant value for healthcare monitoring and early detection of related conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Chirality is a ubiquitous phenomenon in nature, but enantiomers exhibit different pharmacological activities and toxicological effects. Therefore, Chiral recognition plays a pivotal role in various fields such as life sciences, chemical synthesis, drug development, and materials science. The synthesis of novel chiral composites with well-defined loading capabilities and ordered structures holds significant potential for electrochemical chiral recognition applications. However, the design of selective and stable electrochemical chiral recognition materials remains a challenging task., Result: In this work, we construct a simple and rapid electrochemical sensing platform for tryptophan (Trp) enantiomer recognition using cyclodextrin-modified microporous organic network as chiral recognition agent. CD-MON with chiral microenvironment was prepared by Sonogashira-Hagihara coupling reaction of the chiral molecule heptyl-6-iodo-6-deoxyβ-cyclodextrin and 1, 4-Diethynylbenzene. The adhesion of BSA makes CD-MON firmly fixed on the electrode surface, and as a chiral protein, it can improve the chiral recognition ability through synergistic effect. Chiral amino acids are in full contact with the chiral microenvironment during pore conduction of MON, and L-Trp is more stably bound to CD-MON/BSA due to steric hindrance, host-guest recognition and hydrogen bonding. Therefore, the electrochemical sensor can effectively identify tryptophan enantiomers (I L-Trp /I D-Trp  = 2.02), and it exhibits a detection limit of 2.6 μM for L-Trp. UV-Vis spectroscopy confirmed the adsorption capacity of CD-MON towards tryptophan enantiomers in agreement with electrochemistry results., Significance: The prepared chiral sensor has excellent stability, reproducibility (RSD = 3.7%) and selectivity, realizes the quantitative detection of single isomer in tryptophan racemic and quantitative analysis in real samples with 94.0%-101.0% recovery. This work represents the first application of MON in chiral electrochemistry which expands the application scope of chiral sensors and holds great significance in separation science and electrochemical sensing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: Asthma, a chronic respiratory disease closely associated with inflammation, presents ongoing treatment challenges. IALLIPF (le-Ala-Leu-Leu-Ile-Pro-Phe) is one of millet prolamins peptides (MPP) which shows anti-oxidant bioactivity by reducing the production of reactive oxygen species (ROS). Tryptophan (Trp, W) is an amino acid that has been demonstrated to possess anti-inflammatory effects. We introduce a novel cathepsin B-activatable bioactive peptides nanocarrier, PEG-IALLIPF-GFLG-W (MPP-Trp), designed for immunotherapy of asthma., Methods: MPP-Trp is synthesized, purified, and its characteristics are investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The yield of nitric oxide (NO) and pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) are examined to evaluate anti-inflammatory effects of IALLIPF, Trp and MPP-Trp. The immunomodulatory effects of IALLIPF, Trp and MPP-Trp on Th1/Th2 cell populations and cytokines are investigated by flow cytometry, qRT-PCR and ELISA assays. We explore the therapeutic effect of MPP-Trp in the mouse model of asthma by the analysis of lung histology and ELISA. It is necessary to study the biocompatibility of MPP-Trp by CCK8 assay and histopathologic analysis using hematoxylin and eosin (HE) staining., Results: In asthmatic peripheral blood mononuclear cells (PBMCs), IALLIPF, Trp and MPP-Trp are able to significantly alleviate inflammation by inhibiting the yield of nitric oxide (NO) and pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β), especially MPP-Trp. MPP-Trp significantly upregulates Th1 cell levels while notably reducing Th2 cell levels. Furthermore, MPP-Trp effectively elevates the expression and production of interferon-gamma (IFN-γ), an essential cytokine from Th1 cells. Additionally, MPP-Trp markedly diminishes the mRNA expression and levels of key asthma pathogenesis cytokines, such as interleukin-4 (IL-4), interleukin-13 (IL-13), and interleukin-5 (IL-5), in asthma PBMCs. MPP-Trp ameliorates pulmonary pathological alterations and significantly inhibits OVA-induced inflammation in mice with asthma. It has little influence on the cell viability in Asthma-PBMCs treated with various concentrations or durations of MPP-Trp. No pathological changes, including in the heart, liver, spleen, lung, and kidney tissues, are observed in non-sensitized and non-challenged mice treated with MPP-Trp (20 mg/kg)., Discussion: Our research demonstrates that MPP-Trp has immunomodulatory effects on Th1/Th2 cell populations, essential in managing asthma. It considerably alleviates OVA-induced asthma by shifting the immune response towards a Th1-dominant profile, thereby reducing Th2-driven inflammation. Therefore, this novel bioactive peptide nanocarrier, MPP-Trp, holds promise as a candidate for asthma immunotherapy., Competing Interests: The authors report no conflicts of interest in this work., (© 2024 Song et al.)

Tryptophan (Trp) residue provides characteristic vibrational markers to the middle wavenumber spectral region of the Raman spectra recorded from peptides and proteins. In this report, we were particularly interested in eight Trp Raman markers, referred to as W i (i = 1,…,8). All responsible for pronounced Raman lines, these markers originate from indole moiety, a bicyclic conjugated segment involved in the Trp structure. Numerous investigations have previously attempted to relate the variations observed in the spectral features of these markers to the environmental changes of Trp residues. To emphasize the most important points we can mention (i) the variations in the Raman profile of W 4 (∼1360 cm -1 ) and W 5 (∼1340 cm -1 ), frequently observed as a doublet with variable intensity ratio. These two markers were thought to result from a Fermi-resonance effect between certain planar and nonplanar modes; (ii) the changes observed in the wavenumbers and relative intensities of W 4 , W 7 (∼880 cm -1 ) and W 8 (∼760 cm -1 ) were supposed to be related to the accessibility of Trp to surrounding water molecules; and (iii) the wavenumber fluctuations of W 3 (∼1550 cm -1 ), taken as a Trp side chain orientational marker. However, some ambiguities still exist regarding the interpretation of these markers, needing further clarification. Herein, upon a joint experimental and theoretical analysis based on a multiconformational approach, attention was paid to the relationships between structural and vibrational features of three indole-containing compounds with increasing structural complexity, i.e., skatole (3-methylindole), tryptophan, and tripeptide Gly-Trp-Gly. This study clearly shows that the existing assignments given to certain Trp Raman markers should be reconsidered, especially those based on the Fermi-resonance origin of W 4 -W 5 (∼1360-1340 cm -1 ) doublet, as well as the purely environmental dependence of W 7 and W 8 markers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Some amino acids are known to mediate immune responses through gut microbiota metabolism in both humans and monogastric animals. However, through the diet, most free amino acids are absorbed in the small intestine and only a small quantity reaches the microbiota-rich colon. To enhance microbial metabolism of amino acids and their potential health benefits, encapsulation strategies are developed for their protection and delivery to the colon. So far, the main encapsulation systems for amino acids are based on solid lipid particles, but their fate within the digestive tract has never been fully clarified. In this study, we investigated the release of various amino acids (branched-chain amino acid mixture, or lysine, or tryptophan) loaded in solid lipid particles during in vitro oro-gastrointestinal digestion mimicking the piglet. The loaded solid lipid particles were fully characterized for their composition, thermal behavior, molecular structure, crystalline state, surface morphology, and particle size distribution. Moreover, we investigated the effect of particle size by sieving solid lipid particles into two non-overlapping size fractions. We found that amino acid release was high during the gastric phase of digestion, mainly controlled by physical parameters, namely particle size and crystalline state including surface morphology. Large particle size and/or smooth ordered particle indeed led to slower and lower release. Although lipid hydrolysis was significant during the intestinal phase of digestion, the impact of the crystalline state and surface morphology was also observed in the absence of enzymes, pointing to a dominant water/solute diffusion mechanism through these porous solid lipid particles., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Linusorbs (LOs), significantly influence oil quality and sensory properties of flaxseed oil. Trp-containing LOs exhibit distinct oxidative behavior when γ-tocopherol (γ-T) is present. Polar fractions of crude flaxseed oil were stripped via silica absorption, and reintroduced (LO and γ-T) separately into the oil matrix to investigate their interaction during storage. Compared with crude oil, LOs account for 18.49% reduction of p-anisidine value, while LOs with γ-T contributed to most of the endogenous antioxidant effect in crude oil. γ-T was found to suppress oxidation of Trp-containing LO at early stage (Met form), while facilitate oxidation while at their mid-stage (MetO form, Methionine sulfoxide). In vitro oxidation shows that CLD more likely cleaved into peptide fragments, while few products retain intact ring structures. LC-MS/MS analysis and silicon simulation revealed proximity between MetO and Trp residues, facilitating inter- or intra-molecular reactions and ring structure rupture. Remarkably, the presence of γ-T facilitate these phenomena., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Cytosine-rich DNA sequences can fold into intercalated motifs known as i-motifs, through noncanonical hydrogen bonding interactions. Molecular probes can provide valuable insights into the conformational stability and potential cellular functions of i-motifs. W 5 K 5 , a decapeptide composed of alternating tryptophan (W) and lysine (K) units, has been identified as a lead candidate to modulate the structural dynamics of the hypoxia-inducible factor 1-alpha (HIF-1α) DNA i-motif. This finding is expected to facilitate the rational design of peptide-based probes for studying the structure and functional dynamics of i-motifs., (© 2024 European Peptide Society and John Wiley & Sons Ltd.)

This work reports about the conjugation of glycine C-terminal ethyl and methyl ester peptides and L-tryptophan methyl ester with sodium hyaluronate in aqueous solutions using the peptide coupling agent DMTMM (or short DMT, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride). Detailed infrared (IR) absorbance and 1 H and 13 C (2D) NMR studies (heteronuclear multi-bond correlation spectroscopy, HMBC) confirmed covalent and regioselective amide bonds with the D-glucuronate, but also proves the presence of DMT traces in all conjugates. The ethyl ester`s methyl protons on the peptides` C-terminal could be used to quantify the degree of substitution of the peptide on the hyaluronate scaffold by NMR. The ester group also proved stable during conjugation and work-up, and could in some cases be selectively cleaved in water whilst leaving the amide bond intact as shown by potentiometric charge titration, NMR and IR. The conjugates did not influence the capability of human umbilical vein endothelial cells (HUVECs) to reduce MTS (5-[3-(carboxymethoxy)phenyl]-3-(4,5-dimethyl-2-thiazolyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) to a formazan dye, which points towards a low cytotoxicity for the obtained products. The conjugation method and products could be tested for tissue engineering gels or drug delivery purposes with alternative, biologically active peptides., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The electronic and vibrational cryogenic ion spectroscopy of protonated tryptophan (TrpH + ) and dopamine (DAH + ) complexed with methanol has been recorded. These two biological chromophores exhibit ultrafast photochemistry due to excited-state proton transfer (ESPT). We have established the relationship between the structure of the complexes and their photodynamics and compared them with recent results obtained in hydrated complexes. For TrpH + , there is no substantial change between methanol and water complexes; ESPT is hindered by a single solvent molecule. In the DAH + (MeOH) 1 complex, the most stable conformer adopts a structure that prevents the direct interaction of the ammonium group of the side chain with the catechol ring, thus blocking the ESPT reaction. Such a ring structure is indeed a very minor populated conformer in the single-hydrated complex. The change in conformal stability between water and methanol clusters is due to a weak CH-π attractive interaction of the methyl group of methanol with the catechol.

The identification of readers, an important class of proteins that recognize modified residues at specific sites, is essential to uncover the biological roles of post-translational modifications. Photoreactive crosslinkers are powerful tools for investigating readers. However, existing methods usually employ synthetically challenging photoreactive warheads, and their high-energy intermediates generated upon irradiation, such as nitrene and carbene, may cause substantial non-specific crosslinking. Here we report dimethylsulfonium as a methyllysine mimic that binds to specific readers and subsequently crosslinks to a conserved tryptophan inside the binding pocket through single-electron transfer under ultraviolet irradiation. The crosslinking relies on a protein-templated σ-π electron donor-acceptor interaction between sulfonium and indole, ensuring excellent site selectivity for tryptophan in the active site and orthogonality to other methyllysine readers. This method could escalate the discovery of methyllysine readers from complex cell samples. Furthermore, this photo crosslinking strategy could be extended to develop other types of microenvironment-dependent conjugations to site-specific tryptophan., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

The indole ring of tryptophan can form NH/π hydrogen bonds, acting both as a hydrogen donor at the NH group in the pyrrole subring and as a hydrogen acceptor at the benzene subring. In the structural core of the trimeric stable protein Pholiota squarrosa lectin (PhoSL), three indoles are symmetrically arranged and form NH/π hydrogen bonds among each other. Here, we conducted quantum chemical calculations on this indole triad by using various methods and basis sets. The analyses revealed cooperativity in triad formation, with the many-body effect contributing approximately -2 kcal mol -1 , which significantly stabilizes this protein. Symmetry-adapted perturbation theory ascribed this effect to the induced polarization. The electrostatic potential and atomic charges indeed revealed a charge redistribution through the NH/π hydrogen bond, which was favorable for triad formation.

Drug product development of therapeutic antibody formulations is still dictated by the risk of protein particle formation during processing or storage, which can lead to loss of potency and potential immunogenic reactions. Since structural perturbations are the main driver for irreversible protein aggregation, the conformational integrity of antibodies should be closely monitored. The present study evaluated the applicability of a plate reader-based high throughput method for Intrinsic Tryptophan Fluorescence Emission (ITFE) spectroscopy to detect protein aggregation due to protein unfolding in high-concentrated therapeutic antibody samples. The impact of fluorophore concentration on the ITFE signal in microplate readers was investigated by analysis of dilution series of two therapeutic antibodies and pure tryptophan. At low antibody concentrations (< 5 mg/mL, equivalent to 0.8 mM tryptophan), the low inner filter effect suggests a quasi-linear relationship between antibody concentration and ITFE intensity. In contrast, the constant ITFE intensity at high protein concentrations (> 40 mg/mL, equivalent to 6.1 mM tryptophan) indicate that ITFE spectroscopy measurements of IgG1 antibodies are feasible in therapeutically relevant concentrations (up to 223 mg/mL). Furthermore, the capability of the method to detect low levels of unfolding (around 1 %) was confirmed by limit of detection (LOD) determination with temperature-stressed antibody samples as degradation standards. Change of fluorescence intensity at the maximum (ΔIaM) was identified as sensitive descriptor for protein degradation, providing the lowest LOD values. The results demonstrate that ITFE spectroscopy performed in a microplate reader is a valuable tool for high-throughput monitoring of protein degradation in therapeutic antibody formulations., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Aromatic amino acids and their derivatives are diverse primary and secondary metabolites with critical roles in protein synthesis, cell structure and integrity, defense and signaling. All de novo aromatic amino acid production relies on a set of ancient and highly conserved chemistries. Here we introduce a new enzymatic transformation for L-tyrosine synthesis by demonstrating that the β-subunit of tryptophan synthase-which natively couples indole and L-serine to form L-tryptophan-can act as a latent 'tyrosine synthase'. A single substitution of a near-universally conserved catalytic residue unlocks activity toward simple phenol analogs and yields exclusive para carbon-carbon bond formation to furnish L-tyrosines. Structural and mechanistic studies show how a new active-site water molecule orients phenols for a nonnative mechanism of alkylation, with additional directed evolution resulting in a net >30,000-fold rate enhancement. This new biocatalyst can be used to efficiently prepare valuable L-tyrosine analogs at gram scales and provides the missing chemistry for a conceptually different pathway to L-tyrosine., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

The M2 proteins of influenza A and B viruses form acid-activated proton channels that are essential for the virus lifecycle. Proton selectivity is achieved by a transmembrane (TM) histidine whereas gating is achieved by a tryptophan residue. Although this functional apparatus is conserved between AM2 and BM2 channels, AM2 conducts protons exclusively inward whereas BM2 conducts protons in either direction depending on the pH gradient. Previous studies showed that in AM2, mutations of D44 abolished inward rectification of AM2, suggesting that the tryptophan gate is destabilized. To elucidate how charged residues C-terminal to the tryptophan regulates channel gating, here we investigate the structure and dynamics of H19 and W23 in a BM2 mutant, GDR-BM2, in which three BM2 residues are mutated to the corresponding AM2 residues, S16G, G26D and H27R. Whole-cell electrophysiological data show that GDR-BM2 conducts protons with inward rectification, identical to wild-type (WT) AM2 but different from WT-BM2. Solid-state NMR 15 N and 13 C spectra of H19 indicate that the mutant BM2 channel contains higher populations of cationic histidine and neutral τ tautomers compared to WT-BM2 at acidic pH. Moreover, 19 F NMR spectra of 5- 19 F-labeled W23 resolve three peaks at acidic pH, suggesting three tryptophan sidechain conformations. Comparison of these spectra with the tryptophan spectra of other M2 peptides suggests that these indole sidechain conformations arise from interactions with the C-terminal charged residues and with the N-terminal cationic histidine. Taken together, these solid-state NMR data show that inward rectification in M2 proton channels is accomplished by tryptophan interactions with charged residues on both its C-terminal and N-terminal sides. Gating of these M2 proton channels is thus accomplished by a multi-residue complex with finely tuned electrostatic and aromatic interactions.

Fungal secondary metabolite (SM) biosynthetic gene clusters (BGCs) containing dimethylallyltryptophan synthases (DMATSs) produce structurally diverse prenylated indole alkaloids with wide-ranging activities that have vast potential as human therapeutics. To discover new natural products produced by DMATSs, we mined the Department of Energy Joint Genome Institute's MycoCosm database for DMATS-containing BGCs. We found a DMATS BGC in Aspergillus homomorphus CBS 101889, which also contains a nonribosomal peptide synthetase (NRPS). This BGC appeared to have a previously unreported combination of genes, which suggested the cluster might make novel SMs. We refactored this BGC with highly inducible promoters into the model fungus Aspergillus nidulans . The expression of this refactored BGC in A . nidulans resulted in the production of eight tryptophan-containing diketopiperazines, six of which are new to science. We have named them homomorphins A-F ( 2 , 4 - 8 ). Perhaps even more intriguingly, to our knowledge, this is the first discovery of C4-prenylated tryptophan-containing diketopiperazines and their derivatives. In addition, the NRPS from this BGC is the first described that has the ability to promiscuously combine tryptophan with either of two different amino acids, in this case, l-valine or l- allo -isoleucine.

Hydrophobic peptide models derived from the α-helical transmembrane segment of the epidermal growth factor receptor were synthetically modified with a flavin amino acid as a photo-inducible charge donor and decorated with tryptophans along the helix as charge acceptors. The helical conformation of the peptides was conserved despite the modifications, notably also in lipid vesicles and multibilayers. Their ability to facilitate photo-induced transmembrane charge transport was examined by means of steady-state and time-resolved optical spectroscopy. The first tryptophan next to the flavin donor plays a major role in initiating the charge transport near the N-terminus, while the other tryptophans might promote charge transport along the transmembrane helix. These artificially modified, but still naturally derived helical peptides are important models for studying transmembrane electron transfer and the principles of photosynthesis.

As the least abundant residue in proteins, tryptophan widely exists in peptide drugs and bioactive natural products and contributes to drug-target interactions in multiple ways. We report here a clickable tryptophan modification for late-stage diversification of native peptides, via catalyst-free C 2-sulfenylation with 8-quinoline thiosulfonate reagents in trifluoroacetic acid (TFA). A wide range of groups including trifluoromethylthio (SCF 3 ), difluoromethylthio (SCF 2 H), (ethoxycarbonyl)difluoromethylthio (SCF 2 CO 2 Et), alkylthio, and arylthio were readily incorporated. The rapid reaction kinetics of Trp modification and full tolerance with other 19 proteinogenic amino acids, as well as the super dissolving capability of TFA, render this method suitable for all kinds of Trp-containing peptides without limitations from sequences, hydrophobicity, and aggregation propensity. The late-stage modification of 15 therapeutic peptides (1.0 to 7.6 kilodaltons) and the improved bioactivity and serum stability of SCF 3 - and SCF 2 H-modified melittin analogs illustrated the effectiveness of this method and its potential in pharmacokinetic property improvement.

Enteric virus concentration in large-volume water samples is crucial for detection and essential for assessing water safety. Certain dissolution and suspension components can affect the enrichment process. In this study, tangential flow ultrafiltration (TFUF) was used as an enrichment method for recovering enteric virus in water samples. Interestingly, the bacteriophage MS2 recovery in reclaimed water and the reclaimed water without particles were higher than that in ultrapure water. The simulated reclaimed water experiments showed that humic acid (HA) (92.16% ± 4.32%) and tryptophan (Try) (81.50 ± 7.71%) enhanced MS2 recovery, while the presence of kaolin (Kaolin) inhibited MS2 recovery with an efficiency of 63.13% ± 11.17%. Furthermore, Atomic force microscopy (AFM) revealed that the MS2-HA cluster and the MS2-Try cluster had larger roughness values on the membrane surface, making it difficult to be eluted, whereas MS2-Kaolin cluster had compact surfaces making it difficult to be eluted. Additionally, the MS2-HA cluster is bound to the membrane by single hydrogen bond with SO, whereas both the MS2-Try cluster and the MS2-Kaolin cluster are bound to the membrane by two hydrogen bonds, making eluting MS2 challenging. These findings have potential implications for validating standardized methods for virus enrichment in water samples., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Interest in electrocatalytic bioconjugation reactions has surged, particularly for modifying tryptophan and tyrosine residues in proteins. We used a cost-effective graphite felt electrode and low-current methodology to achieve selective bioconjugation of tryptophan with thiophenols, yielding up to 92%. This method exclusively labeled tryptophan residues and incorporated fluorinated tryptophan for NMR analysis. Eight polypeptides, including lanreotide and leuprorelin, were effectively coupled, demonstrating the method's versatility and potential for novel diagnostic and therapeutic agents.

The structure of the sidechain crosslinked Tyr-Leu-Trp peptide produced by the biarylitide crosslinking cytochrome P450 Blt from Micromonospora sp. MW-13 has been reanalysed by a series of NMR, computational and isotope labelling experiments and shown to contain a C-N rather than a C-O bond. Additional in vivo experiments using such a modified peptide show there is a general tolerance of biarylitide crosslinking P450 enzymes for histidine to tryptophan mutations within their minimal peptide substrate sequences despite the lack of such residues noted in natural biarylitide gene clusters. This work further highlights the impressive ability of P450s from biarylitide biosynthesis pathways to act as biocatalysts for the formation of a range of sidechain crosslinked tripeptides., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Two new cyclic dipeptides, paranazzamides A (1) and B (2) containing a C7-prenylated tryptophan, were isolated from a culture broth of snake fungal disease-isolate Paranannizziopsis sp. UH-21. This is the first report on the new secondary metabolites from Paranannizziopsis sp. The planar structures of 1 and 2 were elucidated using various spectroscopic techniques including MS and 1D/2D NMR. The absolute configuration of 1 was assigned by comparison with the synthesized compound. Compounds 1 and 2 exhibited no antifungal activity, no antibacterial activity, and no cytotoxic activity even at a concentration of 128 µg ml -1 , whereas 1 and 2 exhibited amphotericin B potentiating activity against Candida auris in combination treatment., (© 2024. The Author(s), under exclusive licence to the Japan Antibiotics Research Association.)

In the current investigation, we have reported on the preparation of Na-Mordenite (MOR) modified by tryptophan (MOR-NH 2 ) nanocomposite was synthesized and characterized using FT-IR, XRD, SEM, XPS, and BET that represented that the MOR-NH 2 has high surface area 288 m 2 /g and pore volume 0.38 cm 3 /g. This composite represented high efficiency in removal of food dye Azorubine (E122) was 1043 mg/g. Study all the factors that affected on the adsorption such as pH, dose, salinity, E122 dye concentration as well as study the adsorption isotherm models that represented that was fitted to Langmuir. Moreover, study the effect of time according to it the adsorption process was fitted to Pseudo-second-order, and the effect of temperature that approved that the reaction was endothermic, spontaneous, and chemisorption process. The MOR-NH 2 nanocomposite was tested and proven to effectively inhibit the growth of Escherichia coli ATCC® 25922™ and Staphylococcus aureus ATCC® 25923™ at low concentrations. To the best of our knowledge, this work is the first to report the usage of MOR-NH2 adsorbents for the removal of E122 dye in wastewater samples. The mechanism of interaction between MOR-NH 2 and E122 dye was determining as it could be through Hydrogen bonding, pore filling, or through π-π interaction. This research offers a promising solution for purifying water sources that are contaminated with a variety of chemicals, microorganisms, and other contaminants.

Tryptophan is the most prominent amino acid found in proteins, with multiple functional roles. Its side chain is made up of the hydrophobic indole moiety, with two groups that act as donors in hydrogen bonds: the N ϵ -H group, which is a potent donor in canonical hydrogen bonds, and a polarized C δ1 -H group, which is capable of forming weaker, noncanonical hydrogen bonds. Due to adjacent electron-withdrawing moieties, C-H...O hydrogen bonds are ubiquitous in macromolecules, albeit contingent on the polarization of the donor C-H group. Consequently, C α -H groups (adjacent to the carbonyl and amino groups of flanking peptide bonds), as well as the C ϵ1 -H and C δ2 -H groups of histidines (adjacent to imidazole N atoms), are known to serve as donors in hydrogen bonds, for example stabilizing parallel and antiparallel β-sheets. However, the nature and the functional role of interactions involving the C δ1 -H group of the indole ring of tryptophan are not well characterized. Here, data mining of high-resolution (r ≤ 1.5 Å) crystal structures from the Protein Data Bank was performed and ubiquitous close contacts between the C δ1 -H groups of tryptophan and a range of electronegative acceptors were identified, specifically main-chain carbonyl O atoms immediately upstream and downstream in the polypeptide chain. The stereochemical analysis shows that most of the interactions bear all of the hallmarks of proper hydrogen bonds. At the same time, their cohesive nature is confirmed by quantum-chemical calculations, which reveal interaction energies of 1.5-3.0 kcal mol -1 , depending on the specific stereochemistry., (open access.)

Functionalized calix[4]pyrroles are at forefront of host-guest aided molecular sensors. They offer unique platform for flexible functionalization to develop receptors suitable for different applications. In this context, calix[4]pyrrole derivative (TACP) was functionalized with an acidic group to investigate its binding behavior with different amino acids. The acid functionalization facilitated host-guest interactions through hydrogen bonding and increase the solubility of ligand in 90% aqueous media. The results indicated that TACP exhibited significant fluorescence enhancement in the presence of tryptophan while no considerable changes were observed with other amino acids. The other complexation properties such as LOD and LOQ were determined to be 25 µM and 22 µM respectively with 1:1 stoichiometry. In addition, the proposed binding phenomena were further confirmed through computational docking studies and NMR complexation study. Overall, this work highlights the potential of acid functionalization in developing molecular sensors for amino acid detection using calix[4]pyrrole derivatives.Communicated by Ramaswamy H. Sarma.

Conserved tryptophan residues are critical for the structure and the stability of β/γ-crystallin in the lenses of vertebrates. During aging, in which the lenses are continuously exposed to ultraviolet irradiation and other environmental stresses, oxidation of tryptophan residues in β/γ-crystallin is triggered and impacts the lens proteins to varying degrees. Kynurenine derivatives, formed by oxidation of tryptophan, accumulate, resulting in destabilization and insolubilization of β/γ-crystallin, which correlates with age-related cataract formation. To understand the contribution of tryptophan modification on the structure and stability of human βB2-crystallin, five tryptophan residues were mutated to phenylalanine considering its similarity in structure and hydrophilicity to kynurenine. Among all mutants, W59F and W151F altered the stability and homo-oligomerization of βB2-crystallin-W59F promoted tetramerization whereas W151F blocked oligomerization. Most W59F dimers transformed into tetramer in a month, and the separated dimer and tetramer of W59F demonstrated different structures and hydrophobicity, implying that the biochemical properties of βB2-crystallin vary over time. By using SAXS, we found that the dimer of βB2-crystallin in solution resembled the lattice βB1-crystallin dimer (face-en-face), whereas the tetramer of βB2-crystallin in solution resembled its lattice tetramer (domain-swapped). Our results suggest that homo-oligomerization of βB2-crystallin includes potential inter-subunit reactions, such as dissociation, unfolding, and re-formation of the dimers into a tetramer in solution. The W>F mutants are useful in studying different folding states of βB2-crystallin in lens., (© 2024 The Author(s). Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)

In recent years, there has been a growing realization of intricate interactions between the nervous and immune systems, characterized by shared humoral factors and receptors. This interplay forms the basis of the neuroimmune system, the understanding of which will provide insights into the pathogenesis of neurological diseases, in which the involvement of the immune system has been overlooked. Kynurenine and its derivatives derived from tryptophan have long been implicated in the pathogenesis of various neurological diseases. Recent studies have revealed their close association not only with neurological disorders but also with sepsis-related deaths. This review provides an overview of the biochemistry of kynurenine and its derivatives, followed by a discussion of their role via the modulation of the neuroimmune system in various diseases.

Antimicrobial peptides (AMPs) have raised significant interest, forming a potential new class of antibiotics in the fight against multi-drug-resistant bacteria. Various AMPs are ribosomally synthesized and post-translationally modified peptides (RiPPs). One post-translational modification found in AMPs is the halogenation of Trp residues. This modification has, for example, been shown to be critical for the activity of the potent AMP NAI-107 from Actinoallomurus . Due to the importance of organohalogens, establishing methods for facile and selective halogen atom installation into AMPs is highly desirable. In this study, we introduce an expression system utilizing the food-grade strain Lactococcus lactis , facilitating the efficient incorporation of bromo-Trp (BrTrp) into (modified) peptides, exemplified by the lantibiotic nisin with a single Trp residue or analogue incorporated at position 1. This provides an alternative to the challenges posed by halogenase enzymes, such as poor substrate selectivity. Our method yields expression levels comparable to that of wild-type nisin, while BrTrp incorporation does not interfere with the post-translational modifications of nisin (dehydration and cyclization). One brominated nisin variant exhibits a 2-fold improvement in antimicrobial activity against two tested pathogens, including a WHO priority pathogen, while maintaining the same lipid II binding and bactericidal activity as wild-type nisin. The work presented here demonstrates the potential of this methodology for peptide halogenation, offering a new avenue for the development of diverse antimicrobial products labeled with BrTrp.

Amphiphilic peptides show great potential for exfoliating graphite and functionalizing graphene. However, the variety of amino acids complicates our understanding of the underlying mechanisms. In this study, we designed four peptides (C6W1, C6W2, C6W4, and C6W6) with different amounts of aromatic tryptophan amino acids and two additional peptides (C6F4 and C6Y4) by substituting tryptophan with aromatic phenylalanine or tyrosine. This allowed us to investigate the processes and mechanisms of graphite exfoliation and graphene functionalization. Using experimental and computational methods, we discovered that peptides containing tryptophan demonstrated higher exfoliation efficiency and increased tryptophan content further improved this efficiency, resulting in more peptide-functionalized graphene layers. Significantly, the primary driving force for the surface-assisted assembly of peptides on graphite is the π-π stacking interaction between the aromatic ring contributed by aromatic amino acids and the hexagonal rings of the graphite surface. This interaction leads to a layer-by-layer exfoliation mechanism. Our research offers valuable insights into peptide design strategies for one-step graphite exfoliation and graphene functionalization in aqueous environments.

Tryptophan, commonly regarded as buried within the interior cores of proteins to maintain secondary structures, is now being recognized for its significant contributions to protein functionality. However, investigating functional tryptophan-involved interactions across the proteome and manipulating these interactions in live cells are considerable challenges. In this In Focus article, we summarize emerging advances in the field, describing innovative chemistries that leverage distinctive biochemical properties of the indole moiety for targeting and functionally manipulating tryptophan interactions.

Tryptophan (Trp) and tyrosine (Tyr) are the primary precursors of protein-like components in dissolved organic matter. Phenolic compounds are ubiquitous in aquatic environments and are considered the main electron donor in chromophoric dissolved organic matter (CDOM). Our results showed that Trp and Tyr (50 μM) enhanced the transformation of six monophenols (20 μM) with varying numbers of -CH 3 and -OCH 3 substituent groups by a factor of 1.0-1.8. The enhancement factor increased with the ratio of Trp (Tyr) to monophenols. In four different CDOM solutions (5 mg C/L, pH 8.0), a maximum enhancement factor of 3.2-6.7 was observed at a Trp/monophenol concentration ratio of 50. Conversely, monophenols greatly inhibited the transformation of Trp or Tyr. The enhancement factor decreased as the initial pH increased from 3.0 to 10.0. Additionally, the enhancement factor was not directly proportional to the oxidation potential of monophenol. We propose that the promotion effects are generated through the direct oxidation of monophenols by Trp (Tyr) radicals as well as through the reaction between Trp (Tyr) radicals and the one-electron reductant of CDOM.

The tumor immunosuppressive microenvironment (TIME) and uncontrollable release of antigens can lower the efficacy of nanovaccine-based immunotherapy (NBI). Therefore, it is necessary to develop a new strategy for TIME reshaping and controllable release of antigens to improve the NBI efficacy. Herein, an acidity-responsive Schiff base-conjugated polyphenol-coordinated nanovaccine was constructed for the first time to realize bidirectional TIME reshaping and controllable release of antigens for activating T cells. In particular, an acidity-responsive tannic acid-ovalbumin (TA-OVA) nanoconjugate was prepared via a Schiff base reaction. Fe III was coordinated with TA-OVA to produce a Fe III -TA-OVA nanosystem, and 1-methyltryptophan (1-MT) as an indoleamine 2,3-dioxygenase inhibitor was loaded to form a polyphenol-coordinated nanovaccine. The coordination between Fe III and TA could cause photothermal ablation of primary tumors, and the acidity-triggered Schiff base dissociation of TA-OVA could controllably release OVA to realize lysosome escape, initiating the body's immune response. More importantly, oxidative stress generated by a tumor-specific Fenton reaction of Fe ions could promote the polarization of tumor-associated macrophages from the M2 to M1 phenotype, resulting in the upregulation of cytotoxic T cells and helper T cells. Meanwhile, 1-MT could downregulate immunosuppressive regulatory T cells. Overall, such skillful combination of bidirectional TIME reshaping and controllable antigen release into one coordination nanosystem could effectively enhance the NBI efficacy of tumors.

Cp 2 Fe-mediated electrochemical synthesis of phosphorylated indoles and Trp-containing oligopeptides has been developed, which eliminates the need for external oxidants and yields the desired products in moderate to excellent yields under mild conditions. Importantly, the synthetic applicability was further demonstrated through its easy scalability and the anticancer activity of the product. Remarkably, it presents the first electrochemical protocol to access the phosphorylation of indoles and Trp-containing oligopeptides.

L-tryptophan is an amino acid that is essential to the metabolism of humans. Therefore, there is a high interest for its detection in biological fluids including blood, urine, and saliva for medical studies, but also in food products. Towards this goal, we report on a new electrochemiluminescence (ECL) method for L-tryptophan detection involving the in situ production of hydrogen peroxide at the surface of boron-doped diamond (BDD) electrodes. We demonstrate that the ECL response efficiency is directly related to H 2 O 2 production at the electrode surface and propose a mechanism for the ECL emission of L-tryptophan. After optimizing the analytical conditions, we show that the ECL response to L-tryptophan is directly linear with concentration in the range of 0.005 to 1 µM. We achieved a limit of detection of 0.4 nM and limit of quantification of 1.4 nM in phosphate buffer saline (PBS, pH 7.4). Good selectivity against other indolic compounds (serotonin, 3-methylindole, tryptamine, indole) potentially found in biological fluids was observed, thus making this approach highly promising for quantifying L-tryptophan in a broad range of aqueous matrices of interest.