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In this report, we describe the methodology for 96 parallel organic syntheses of peptides on Teflon-patterned paper assisted by heating with an infra-red lamp. SPOT synthesis is an important technology for production of peptide arrays on a paper-based support for rapid identification of peptide ligands, epitope mapping, and identification of bio-conjugation reactions. The major drawback of the SPOT synthesis methodology published to-date is suboptimal reaction conversion due to mass transport limitations in the unmixed reaction spot. The technology developed in this report overcomes these problems by changing the environment of the reaction from static to dynamic (flow-through), and further accelerating the reaction by selective heating of the reaction support in contact with activated amino acids. Patterning paper with Teflon allows for droplets of organic solvents to be confined in a zone on the paper array and flow through the paper at a well-defined rate and provide a convenient, power-free setup for flow-through solid-phase synthesis and efficient assembly of peptide arrays. We employed an infra-red (IR) lamp to locally heat the cellulosic support during the flow-through delivery of the reagents to each zone of the paper-based array. We demonstrate that IR-heating in solid phase peptide synthesis shortened the reaction time necessary for amide bond formation down to 3 minutes; in some couplings of alpha amino acids, conversion rates increased up to fifteen folds. The IR-heating improved the assembly of difficult sequences, such as homo-oligomers of all 20 natural amino acids.

Tannery solid waste (TSW) contains 70–90% collagen by weight. The rapid extraction of collagen while preserving its original and unique triple-helical conformation has proved challenging. In this paper, an ionic liquid-synergistic dissolution and regeneration (IL-SDR) method was developed based on a TBAH/DMSO/H2O ternary (TDH) solvent for the rapid recovery of collagen from TSW under mild conditions. A solubility of 10.25% TSW and a collagen recovery yield of 51.2% were achieved in 30 minutes at room temperature. The original triplet helical conformation and the molecular weight of the collagen product were retained, confirmed via FT-IR, circular dichroism, and matrix-assisted laser desorption/ionization time-of-flight analysis. SEM was used to verify that dense and uniform pores could be formed within collagen by adjusting the DMSO content, and cytotoxicity and moisture retention tests demonstrated that the collagen produced via the IL-SDR process is comparable to natural collagen used in cosmetic and skincare applications. Moreover, the TDH solvent demonstrated excellent reproducibility across five cycles, achieving consistent solubility varying from 9.71% to 11.04%. EPR and 1H NMR showed that the OH– in TBAH induced the generation of DMSO˙ free radicals in the TDH solvent, and these radicals were indispensable for the dissolution of TSW. The DMSO content was positively correlated with the concentration of free radicals. A synergistic dissolution mechanism was proposed: DMSO˙ free radicals preferentially cleaved the terminal peptide chains, causing the collagen molecules to be exposed to DMSO. Subsequently, DMSO disrupted the original hydrogen bond network within the collagen molecules. Then, TBAH and DMSO formed hydrogen bonds with the collagen molecules, stabilizing the dissolved collagen and preventing the reformation of the hydrogen bond network between collagen molecules. This work provides an avenue for low-temperature and rapid dissolution of TSW, and reveals an in-depth, atypical dissolution mechanism for collagen-based materials during the IL-SDR process. [ABSTRACT FROM AUTHOR]

By establishing both a highly efficient phosphonamidate formation and a RuCp-catalyzed cleavage of an allyl linker, the solid-phase synthesis of Fmoc-(GlyP(OBn))6-OH/DIEA, a protected form of a new type of unnatural peptide α-amino phosphonic acid oligomer (APO), has been realized. [ABSTRACT FROM AUTHOR]

Substitution of disulfide bonds with a diselenide bonds in peptides and proteins is an often-used strategy to increase the stability of naturally occurring peptides and proteins. In this paper, diselenide metathesis between model diselenide dimer peptides, as well as that in diselenide(s)-substituted biologically active peptides, were analyzed. Surprisingly, depending on the tertiary structure of the peptides, we observed that the metathesis reaction occurs under physiological conditions even in the absence of reducing agents, light and heating.

A selected ion monitoring (SIM) approach combined with high resolution mass spectrometry is employed to identify and distinguish common SARS-CoV2 omicron and recombinant variants in clinical specimens. Mutations within the receptor binding domain (RBD) within the surface spike protein of the virus result in a combination of peptide segments of unique sequence and mass that were monitored to detect BA.2.75 (including CH.1.1) and XBB (including 1.5) variants prevalent in the state's population in early 2023. SIM detection of pairs of peptides unique to each variant were confidently detected and differentiated in 57.3% of the specimens, with a further 10 or 17.5% (for a total of 74.8%) detected based on a single peptide biomarker. The BA.2.75 sub-variant was detected in 18.7%, while recombinant variants XBB and XBB.1.5 were detected in 13.3% and 25.3% of the specimens respectively, consistent with circulating levels in the population characterised by RT-PCR. Virus was detected in 75 SARS-CoV2 positive specimens by mass spectrometry down to the low or mid 104 copy level, with a single false positive and no false negative identified. This article is the first paper to characterise recombinant strains of the SARS-CoV2 virus by this, or any other, MS method. [ABSTRACT FROM AUTHOR]

Angiotensin and kinin metabolic pathways are reported to be altered by many diseases, including COVID-19. Monitoring levels of these peptide metabolites is important for understanding mechanisms of disease processes. In this paper, we report dimethyl labeling of amines in peptides by addition of formal-dehyde to samples and deutero-formaldehyde to internal standards to generate nearly identical isotopic standards with 4 m/z units larger per amine group than the corresponding analyte. We apply this approach to rapid, multiplexed, absolute LC-MS/MS quantitation of renin angiotensin system (RAS) and kallikrein-kinin system (KKS) peptides in human blood serum. Limits of detection (LODs) were obtained in the low pg mL−1 range with 3 orders of magnitude dynamic ranges, appropriate for determinations of normal and elevated levels of the target peptides in blood serum and plasma. Accuracy is within ±15% at concentrations above the limit of quantitation, as validated by spike-recovery in serum samples. Applicability was demonstrated by measuring RAS and KKS peptides in serum from COVID-19 patients, but is extendable to any class of peptides or other small molecules bearing reactive –NH2 groups. [ABSTRACT FROM AUTHOR]

Murepavadin (POL7080) in phase III clinical trials, a backbone-cyclized polypeptide composed of 14 amino acids, has a novel mode of action and shows a specific and efficient bactericidal effect against multidrug-resistant Pseudomonas aeruginosa . It is a potential candidate to treat severe P. aeruginosa infections in the future and still has significant commercial value for further research and development. In this paper, we report a liquid-phase peptide synthetic route for this valuable candidate polypeptide assisted by hydrophobic-support materials (tags), which overcomes the difficulties of high cost and poor yield in the traditional solid-phase synthesis of macrocyclic peptides. Through the careful optimization of reaction conditions and the innovative strategy of synthetic post-treatment, we established a simple and efficient liquid-phase synthetic route suitable for POL7080 and other similar structures, with satisfactory yield, high purity and a production process not being controlled by scale.

Sequential peptide coupling plays a central role in chemical protein synthesis. This paper describes a new peptide derivative, peptide-aminothiazoline (At), whereof the C-terminus is functionalized with 2-aminothiazoline. Peptide-At streamlined the sequential peptide ligation in a one-pot manner and demonstrated the convergent synthesis of a circular protein and homogeneous glycoproteins.

NJC New Journal of Chemistry A journal for new directions in chemistryrsc. li/ njc ISSN 1144- 0546 PAPER Hae Sook Park and Young Kee Kang Helix preferences of cyclopentane- containing  /  - hybrid peptides Volume 48 Number 35 21 September 2024 Pages 15251– 15706 [Extracted from the article]

Fluorescence indicators capable of binding to human immunodeficiency virus-1 (HIV-1) trans-activation responsive (TAR) RNA are powerful tools for the exploratory studies of the identification of anti-HIV drug candidates. This work presents a new design strategy for fluorogenic indicators with a transactivator of transcription (Tat)-derived peptide based on the forced intercalation of thiazole orange (TO) dyes (FIT). The developed 9-mer FIT peptide (RKKRR-TO-RRR: named FiLuP) features the TO unit integrated onto a Dap (2,3-diaminopropionic acid) residue in the middle of the Tat peptide sequence; the Q (glutamic acid) residue in the Tat peptide (RKKRR-Q-RRR) is replaced with TO as if it were an amino acid surrogate. This facilitates a significant light-up response (450-fold at λem = 541 nm, Φfree = 0.0057, and Φbound = 0.61) upon binding to TAR RNA. The response of FiLuP is highly selective to TAR RNA over other non-cognate RNAs, and FiLuP maintains strong binding affinity (Kd = 1.0 ± 0.6 nM). Significantly, in contrast to previously developed Tat peptide-based FRET probes, FiLuP is able to discriminate between "competitive" and "noncompetitive" inhibitors when used in the fluorescence indicator displacement (FID) assay. The FID assay under stringent screening conditions is also possible, enabling super-strong competitive binders toward TAR RNA to be sieved out. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides are promising alternatives to classical antibiotics. Their microbicidal activity can arise from different mechanisms, one of which is known as nutritional immunity and has metal micronutrients and metal-binding biomolecules as its main players. Calcitermin is an antimicrobial peptide and an effective metal chelator. Its properties as an antibacterial and anti-Candida agent have been recently studied both as a free peptide and in the presence of zinc and copper ions, with which it forms stable complexes. Calcitermin derivatives have also gained attention thanks to the possibility of improving their properties, like metal-binding affinity and/or stability in biological fluids, through ad hoc modifications of the native peptide sequence. In this work, the Ala-to-Ser substitutions close to the coordination site of calcitermin have been introduced to study the impact on the biological activity and metal-binding properties. Our results show that metal coordination has a clear impact on the bioactivity of the studied compounds, to the point that the truncated fragment of calcitermin, solely containing the main metal-binding residues, also shows antimicrobial activity. [ABSTRACT FROM AUTHOR]

The discovery of systems capable of recognizing amyloid-β protein (Aβ) oligomeric species with high sensitivity and specificity, also producing detectable signals, could represent an attractive approach for the early diagnosis of Alzheimer's disease (AD). In this regard, peptide-based inhibitors of Aβ aggregation have been extensively studied with particular attention to those derived from original amyloid sequences, such as the hydrophobic Aβ16–20 core (KLVFF). In this study we combined the antifibrillogenic action of the KLVFF peptide motif with the spectroscopic features of the porphyrin macrocycle. Specifically, we describe the synthesis of a new water-soluble zinc metallated porphyrin–peptide conjugate, in which the porphyrin macrocycle is linked via 1,2,3-triazole linkage to the hydrophobic Aβ16–20 sequence. The zinc–porphyrin–peptide conjugate was obtained by copper-catalyzed azide–alkyne cycloaddition (CuAAC) in the presence of Cu(I) as a catalyst. The "click" reaction was carried out between the azido-KLVFF peptide and the alkyne-porphyrin. The ability of the porphyrin–peptide conjugate to interact with Aβ was investigated. The zinc-metallated porphyrin–peptide conjugate was studied by biophysical techniques, including UV-vis, circular dichroism (CD), and Bis-Ans fluorescence. Finally, cell viability studies were performed on differentiated neuroblastoma cells. [ABSTRACT FROM AUTHOR]

Safety problems caused by organophosphorus pesticide (OP) residues are constantly occurring, so the development of new methods for the degradation and detection of OPs is of great scientific significance. In the present study, β-sheet peptides and β-hairpin peptides for catalyzing the hydrolysis of OPs were designed and synthesized. The peptide sequences with the highest hydrolytic activity (EHSGGVTVDPPLTVEHSAG) were screened by investigating the effect of the location of the active sites of the peptide and the peptide's structure on the degradation of OPs. In addition, the relationship between the peptides' conformation and hydrolytic activity was further analyzed based on density functional theory calculations. The noncovalent interactions of the peptides with the OPs and the electrostatic potential on the molecular surface and molecular docking properties were also investigated. It was found that peptides with approximate active amino acids consisting of the catalytic triad and with the hairpin structure had enhanced hydrolytic activity toward the hydrolysis of OPs. To develop an electrochemical sensor technique to detect OPs, the conductive MXene (Ti3C2) material was first immobilized with a caffeic acid monolayer via enediol–metal complex chemistry and then bound with the β-hairpin peptide (EHSGGVTVDPPLTVEHSAG) via carboxy–amine condensation chemistry between the –COOH of caffeic acid and the –NH2 of the peptide to prepare a MXene–peptide composite. Then, the prepared composite was modified on the surface of a glassy carbon electrode to construct an electrochemical sensor for the detection of OPs. The developed technique could be used to monitor OPs within 15 min with a two orders of linear working range and with a detection limit of 0.15 μM. Meanwhile, the sensor showed good reliability for the detection of OPs in real vegetables. [ABSTRACT FROM AUTHOR]

The spontaneous aggregation of infectious or misfolded forms of prion protein is known to be responsible for neurotoxicity in brain cells, which ultimately leads to the progression of prion disorders. Bovine spongiform encephalopathy (BSE) in animals and Creutzfeldt–Jakob disease (CJD) in humans are glaring examples in this regard. Square-planar complexes with labile ligands and indole-based compounds are found to be efficiently inhibitory against protein aggregation. Herein, we report the synthesis of an indole-based cyclometallated palladium complex. The ligand and complex were characterized by various spectroscopic techniques such as UV-visible, NMR, IR, and HRMS. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with PrP106–126 was studied using UV-visible spectroscopy, CD spectroscopy, MALDI-TOF MS, and molecular docking. The inhibition effects of the complex on the PrP106–126 aggregation, fibrillization and amyloid formation phenomena were analysed through the ThT assay, CD, TEM and AFM. The effect of the complex on the aggregation process of PrP106–126 was determined kinetically through the ThT assay. The complex presented high binding affinity with the peptide and influenced the peptide's conformation and aggregation in different modes of binding. Furthermore, the MTT assay on neuronal HT-22 cells showed considerable protective properties of the complex against PrP106–126-mediated cytotoxicity. These findings suggest that the compound influences peptide aggregation in different ways, and the anti-aggregation action is primarily associated with the metal's physicochemical properties and the reactivity rather than the ligand. As a result, we propose that this compound be investigated as a potential therapeutic molecule in metallopharmaceutical research to treat prion disease (PD). [ABSTRACT FROM AUTHOR]

Abrin toxin, highly dangerous with an estimated human lethal dose of 0.1–1 μg per kg body weight, has attracted much attention regarding criminal and terroristic misuse over the past decade. Therefore, developing a rapid detection method for abrin toxin is of great significance in the field of biosecurity. In this study, based on the specific dissociation method of an immobilized enzyme reactor, the trypsin immobilized reactor Fe3O4@CTS–GA–Try was prepared to replace free trypsin, and the immobilized enzyme digestion process was systematically investigated and optimized by using bovine serum albumin as the simulant of abrin. After 5 min one-step denaturation and reduction, a satisfactory peptide number and coverage were yielded with only 15 s assisted by an ultrasound probe to identify model proteins. Subsequently, abrin was rapidly digested using the established method, resulting in a stable and highly reproducible characteristic peptide number of 39, which can be analyzed by nanoelectrospray ionization coupled with high-resolution mass spectrometry. With the acquisition mode of full MS scan coupled with PRM, not only MS spectroscopy of total abrin peptides but also the corresponding MS/MS spectroscopy of specific abrin peptides can achieve the characteristic detection of abrin toxin and its different isoforms in less than 10 minutes, with high repeatability. This assay provides a universal platform and has great potential for the development of on-site detection and rapid mass spectrometric analysis techniques for macromolecular protein toxins and can further be applied to the integrated detection of chemical and biological agents. [ABSTRACT FROM AUTHOR]

Herein, we describe the synthesis and characterisation of four new supramolecular cobalt conjugates of antimicrobial peptides functionalised with terpyridine ligands (L). Peptides were chosen based on the well-established arginine-tryptophan (RW)3 motif, with terpyridine-derivatized lysine (Lys(tpy)) added to the sequence, or replacing tryptophan residues. Self-assembly of the antimicrobial peptides with Co(BF4)2·6H2O formed exclusively CoL2 dimers (for peptides with one tpy ligand each) and Co2L4 metallo-macrocycles (for peptides with two tpy ligands for each peptide), which could be 'locked' by oxidation of Co(+II) to Co(+III) with ammonium ceric nitrate. The Co-peptide complexes were characterised by mass spectrometry and in solution by NMR spectroscopy, including 2D diffusion ordered NMR spectroscopy (DOSY) which confirmed the proposed stoichiometries. The antimicrobial activity of the novel peptides and their metallo-supramolecular assemblies was investigated by determination of their minimal inhibitory concentration (MIC) against a panel of Gram-positive and Gram-negative bacteria. Complexation with cobalt increases the activity of the peptides in almost every case. Most of the new metal–peptide conjugates showed good activity against Gram-positive bacteria, including a multi-resistant S. aureus strain and the opportunistic pathogenic yeast C. albicans (down to 7 μmol l−1 for the most active Co2L4 derivate), a value that is increased five-fold compared to the lysine-derivatized peptide ligand alone. Interestingly, conjugates of the CoL2 type also showed decent activity against Gram-negative bacteria including the WHO-flagged problematic A. baumannii strain (down to 18 μmol l−1 for the most active derivative). [ABSTRACT FROM AUTHOR]

Enzyme-instructed self-assembly (EISA) has been explored for many applications in the life sciences including imaging and therapeutics. To date, use of the strategy is limited by the relatively high concentration – often in the mM regime – required for assembly. Here, a porphyrin–peptide conjugate (1) was designed as a water-soluble, EISA substrate. Compound 1 is built around a trans-AB porphyrin chassis that is equipped with a monodisperse 1 kDa polyethylene glycol (PEG) linker (a surrogate for a potential targeting agent) and an enzymatically triggerable self-assembly motif. The latter is comprised of two identical self-assembly peptides (also known as hydrogelators) attached to the 2,6-positions of an aryl group. The peptides have sequence GffY and in protected form contain tyrosine as an O-phosphoester GffY(p). Treatment of 1 with alkaline phosphatase (ALP) gave rise to the self-assembly (or aggregation) process as characterized by absorption spectroscopy. A control compound without the phosphoester trigger was synthesized and examined for the self-assembly process using fluorescence and absorption spectroscopy. A concentration-dependent study showed that at 10 nM approximately 50% of porphyrin–peptide conjugate was in the aggregated form. The nanomolar assembly suggests possible applications of EISA substrates in chemotherapy, although a further decrease in concentration to the picomolar regime may be required for use in targeted molecular radiotherapy, where very low mass dosing is typical. [ABSTRACT FROM AUTHOR]

In this paper, we show that a hierarchical approach for the construction of nanofibrils based on α,β-peptide foldamers is a rational method for the design of novel self-assembled nanomaterials based on peptides. Incorporation of a trans -(1 S ,2 S )-2-aminocyclopentanecarboxylic acid residue into the outer positions of the model coiled-coil peptide led to the formation of helical foldamers, which was determined by circular dichroism (CD) and vibrational spectroscopy. The oligomerization state of the obtained peptides in water was established by analytical ultracentrifugation (AUC). The thioflavin T assay and Congo red methods showed that the obtained α,β-peptides possess a strong tendency to aggregate, leading to the formation of self-assembled nanostructures, which were assessed by microscopic techniques. The location of the β-amino acid in the heptad repeat of the coiled-coil structure proved to have an influence on the secondary structure of the obtained peptides and on the morphology of the self-assembled nanostructures.

This paper is the first report of a non-competitive fluorescence polarization immunoassay (NC-FPIA) using a peptide as a tracer. The NC-FPIA can easily and quickly quantify the target after simply mixing them together. This feature is desirable for point-of-need applications such as clinical diagnostics, infectious disease screening, on-site analysis for food safety, etc. In this study, the NC-FPIA was applied to detect CD9, which is one of the exosome markers. We succeeded in detecting not only CD9 but also CD9 expressing exosomes derived from HeLa cells. This method can be applied to various targets if a tracer for the target can be prepared, and expectations are high for its future uses. [ABSTRACT FROM AUTHOR]

The human cationic antimicrobial protein (hCAP) corresponding to the overlapping sequences of 151–162 of hCAP named KR-12 peptide is the smallest portion of the only type of human Cathelicidin, which has been shown to be modifiable into a more effective antimicrobial. In this study, an in silico analysis, supported by potentiometric titration and isothermal titration calorimetry techniques, was performed to identify potential Cu(II) binding sites of KR-12. The analysis of the presented data at the given theoretical level (GFN2-xTB/ALPB) revealed which peptide chain fragments are involved in the most favourable KR-12–Cu(II) binding mode. Based on a quantum chemical approach, the most favourable coordination modes of Cu(II) to peptides are proposed together with the discussion of the chemical nature of the interactions. The presented results demonstrated that KR-12 interacts with metal ions mostly via the main chain's oxygen atoms; however, the two types of amino acids that are expected to be vital for the interaction of Cu(II) are D (aspartic acid) and R29 (arginine). It was demonstrated that in order to explain the complexity of the interaction process in peptide–metal ion systems, the use of theoretical methods is sometimes necessary to explain the details of the experimental results and provide an in-depth understanding of these dynamic systems. [ABSTRACT FROM AUTHOR]

A green strategy for the selective alkylation of cysteine-containing peptides in a continuous flow reactor has been developed, providing an efficient pathway to alkylated cysteine-containing peptides under mild conditions. This process does not need light, metal catalysts, or oxidative reagents. It provides a useful method for the modification of amino acids and peptides. As one of the low cost and synthetic versatile raw materials, the alkyl thianthenium salt can be used as an alkylation source in the preparation of alkylated cysteine-containing peptides. In addition, the microfluidics technology can shorten the reaction time and improve the efficiency, thus reducing the costs and energy consumption of the synthesis process. A series of alkylated cysteine-containing peptides (41 examples) has been synthesized here with a short residence time (14.0 min), and with good to excellent yields. [ABSTRACT FROM AUTHOR]

The absence of better biomarkers currently limits early diagnosis and treatment of triple-negative breast cancer (TNBC). Our previously published study reported that the cyclic-peptide SD01 exhibited specific binding to EphA2 (Ephrin type-A receptor 2) on TNBC. To develop a novel PET imaging agent, we prepared gallium-68 (68Ga) labeled-DOTA-SD01 and evaluated its specificity and effectiveness through micro PET/CT imaging in a TNBC-bearing mouse model. SD01 and a control linear peptide YSA were conjugated to DOTA and subsequently labeled with 68Ga, obtaining 68Ga-DOTA-SD01 and 68Ga-DOTA-YSA. Both showed high radiochemical purity, stability, good hydrophilicity, and high binding affinity to 4T1 cells. Micro PET/CT imaging showed high radioactivity accumulation in tumors; SUVmean (mean standardized uptake value) of tumors in the group of 68Ga-DOTA-SD01 was 3.34 ± 0.25 and 2.65 ± 0.32 in the group of 68Ga-DOTA-YSA; T/NT ratios (target to non-target, SUVmean ratios of tumor to muscle) were 3.12 ± 0.06 and 2.77 ± 0.11 at 30 min, respectively (p < 0.05). The biodistribution study showed that tumor uptake % ID per g (percentage of injected dose per gram of tissue) in the group of 68Ga-DOTA-SD01 was 2.73 ± 0.34, and 1.77 ± 0.38 in the group of 68Ga-DOTA-YSA; T/NT ratios (radioactivity of tumor to muscle) were 3.55 ± 0.12 and 3.05 ± 0.10 for both groups at 30 min, respectively (p < 0.05). All these suggest that 68Ga-DOTA-SD01 may act as a better novel PET imaging agent for EphA2 positive tumors, such as TNBC. [ABSTRACT FROM AUTHOR]

Phytosulfokine (PSK) is a highly conserved plant peptide hormone (PPH) containing two sulfated tyrosine residues. PSK acts as a growth factor in Arabidopsis thaliana plant species and significantly improves the efficiency of cellular proliferation in plant cell culture, a process known as regeneration. However, many important plant species are recalcitrant under exposure to PSK and require e.g., artificially generated PPHs to boost regeneration. Here, we report the design, chemical synthesis, and biological evaluation of the regeneration capacity of a PSK-like peptide library. Our set of thirteen PSK analogues included N-terminal modifications, amino acid substitutions, incorporation of diastereomers, and backbone N-methylation. Insertion of the latter required solution-phase synthesis of the proper building block prior to solid-phase peptide synthesis. The biological activity of the PSK analogues was assessed in the regeneration capacity of Brassica oleracea cells (protoplasts). Most PSK analogues did not affect the regeneration capacity as compared to PSK. For example, when an alanine substitution was introduced and replaced either 2-Ile or 4-Thr, the bio-activity was fully abolished. However, 2-allo-Ile PSK and 4-Nme-Thr PSK showed increased activity in protoplast regeneration when compared with that of the native peptide. These findings indicated that introducing small chemical modifications in the PPH PSK provides opportunities for inducing protoplast regeneration in recalcitrant species. [ABSTRACT FROM AUTHOR]

Self-assembled peptide hydrogels possess remarkable biological activity and biocompatibility. When utilized for local drug delivery, they require enhanced mechanical properties and the ability to facilitate controlled release of drugs. Herein, we present the design and synthesis of a supramolecular hydrogel (Fmoc-GFFG/SBE-β-CD). The hydrogel incorporates host–guest interactions between a self-assembling peptide (Fmoc-GFFG) and cyclodextrin molecules (SBE-β-CD) to improve the viscoelastic strength of the hydrogel while maintaining biocompatibility. With remarkable shear-thinning properties, the Fmoc-GFFG/SBE-β-CD hydrogel exhibits enhanced in vivo retention time, thereby facilitating the development of an injectable drug delivery system. Using 10-hydroxycamptothecin (HCPT) as a model drug, we develop a hydrogel system (Fmoc-GFFG/SBE-β-CD@HCPT) that capitalizes on the inclusion complex formation between SBE-β-CD and HCPT. The resulting composite hydrogels effectively prevent the agglomeration of drug molecules, ensuring the sustained release of HCPT while preserving its anticancer efficacy. The findings presented in this work establish a foundation for the broadening of peptide-based biomaterials and offer a promising avenue for the development of sophisticated drug delivery systems. [ABSTRACT FROM AUTHOR]

Pseudo-allergic reactions are non-IgE-mediated immediate allergic reactions, and MRGPRX2 is a potential important target for pseudo-allergic reactions. Currently, numerous reports focus on the induction of pseudo-allergic reactions by small molecule drugs and endogenous peptides. However, insufficient attention has been paid to the pseudo-allergic reactions induced by exogenous peptides through MRGPRX2. Therefore, this study selected immunogenic peptide composition HL-9-5, which has a structure and properties similar to substance P, and its analogue HL-9-4. We conducted experiments through LAD2 cell β-hexosaminidase release, histamine release, cytokine release and MRGPRX2-HEK293 cell calcium mobilization assay in vitro, and mice paw swelling, serum histamine detection, hindpaw skin H&E and TB staining in vivo demonstrated that HL-9-4 and HL-9-5 can trigger pseudo-allergic reactions via MRGPRX2. Molecular docking further showed that SP, HL-9-4 and HL-9-5 can act on the same cavity in MRGPRX2, and ASP-174 was identified as the conserved site of interaction for all three compounds. Therefore, HL-9-4 and HL-9-5 are exogenous analogues of substance P that can induce pseudo-allergic reactions. This study laid the foundation for research on the mechanism of pseudo-allergic reactions induced by exogenous peptide compounds and was also of great significance for subsequent research on the interaction between various ligands and MRGPRX2 and for the development of peptide antagonists. [ABSTRACT FROM AUTHOR]

Peptides respresent intriguing materials to achieve sustainable catalytic reactivity that mimic the natural functions of enzymes, but without the limitations of temperature/solvent sensitivity. They could also be applicable to a wide variety of substrates, thus expanding their potential use at different reaction levels ranging from the benchtop to industrial. Unfortunately, significant use of catalytic peptides remains limited due to the general lack of understanding of the fundamental basis of their inherent reactivity. In this contribution, we examine the reactivity of a peptide (termed CPN3) previously isolated with ester hydrolysis reactivity. It is demonstrated that the system is most reactive under slightly basic conditions. While the system is slower than comparable enzymes, it demonstrates significant reactivity across multiple substrates and different reaction conditions that could likely lead to enzymatic denaturation. In addition, key active site residues were identified to begin to elucidate the fundamental basis of the reactivity. Such results could be used to design new sequences with enhanced reactivity under sustainable conditions. [ABSTRACT FROM AUTHOR]

Water soluble, cationic charge, peptide appended perylenebisimide (PBI-CFK) has been designed, synthesized, purified, and fully characterized. A hybrid system has been composed with PBI-CFK and oppositely charged deprotonated ferrocenedicarboxylic acid (Fc). In this case, PBI-CFK acts as an acceptor and Fc as a donor. The UV-visible study reveals the blue shift of PBI-CFK absorption and its photoluminescence intensity is gradually quenched upon the addition of Fc upto 1 equivalent. HR-TEM (high-resolution transmission electron microscopy) studies exhibit highly ordered and more condensed structures of the hybrid system than those of each of these components. The current–voltage (I–V) study clearly shows that the hybrid provides better semiconducting properties compared to PBI-CFK, which appears to be due to the electronic and ionic interaction of these two components. Here, PBI-CFK exhibits photoswitching properties with a photocurrent gain (Ion/Ioff) of 2.04, whereas the hybrid shows a significant improvement of the photoswitching properties with the photocurrent gain (Ion/Ioff) of 4.04 and this is about twice that of the individual one. Thus, the formation of a donor–acceptor conjugate between Fc and PBI-CFK results in modulation of the optoelectronic and photoswitching properties. [ABSTRACT FROM AUTHOR]

Recently, we have studied the coordination chemistry of the Cu(II)–histidine-rich C-terminal tail (HRCT) complex of the mycobacterial GroEL1 protein. The structure of this domain differs significantly compared to the well-known methionine-glycine-rich GroEL chaperonin – it was predicted that mycobacterial GroEL1 could play a significant role in the metal homeostasis of Mycobacteria, especially copper. However, we found that this particular domain's pattern also repeats in a number of Ni(II)-binding proteins. Here, we present the studies concerning the properties of GroEL1 HRCT as a ligand for Ni(II) ions. For this purpose, we chose eight model peptides: L1 – Ac-DHDHHHGHAH, L2 – Ac-DKPAKAEDHDHHHGHAH, and 6 mutants of the latter in the pH range of 2–11. We examined the stoichiometry, stability, and spectroscopic features of copper complexes. We noticed that similar to the Cu(II)-complex, the presence of a Lys5 residue significantly increases the stability of the system. The impact of His mutations was also examined and carefully studied using NMR spectroscopy. His9 and His13 are the crucial residues for Ni(II) binding, whereas His12 has minimal relevance in complex formation. [ABSTRACT FROM AUTHOR]

Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a versatile bioanalytical technique for protein analysis. Since the reliability of HDX-MS analysis considerably depends on the retention of deuterium labels in the post-labeling workflow, deuterium/hydrogen (D/H) back exchange prevention strategies, including decreasing the pH, temperature, and exposure time to protic sources of the deuterated samples, are widely adopted in the conventional HDX-MS protocol. Herein, an alternative and effective back exchange prevention strategy based on the encapsulation of a millimeter droplet of a labeled peptide solution in a water-immiscible organic solvent (cyclohexane) is proposed. Cyclohexane was used to prevent the undesirable uptake of water by the droplet from the atmospheric vapor through the air–water interface. Using the pepsin digest of deuterated myoglobin, our results show that back exchange kinetics of deuterated peptides is retarded in a millimeter droplet as compared to that in the bulk solution. Performing pepsin digestion directly in a water-in-oil droplet at room temperature (18–21 °C) was found to preserve more deuterium labels than that in the bulk digestion with an ice-water bath. Based on the present findings, it is proposed that keeping deuterated peptides in the form of water-in-oil droplets during the post-labelling workflow will facilitate the preservation of deuterium labels on the peptide backbone and thereby enhance the reliability of the H/D exchange data. [ABSTRACT FROM AUTHOR]

This paper focused on the mechanism of Ser-Ala-Gly-Pro-Ala-Phe (SAGPAF) treatment to improve gastric mucosal injury in mice. A gastric mucosa injury model induced by ethanol was established, and the superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, nitric oxide (NO) content and myeloperoxidase (MPO) level were determined. We performed macroscopic and histopathological evaluation of the gastric organs. Moreover, we analyzed the mechanism of SAGPAF treatment by western blotting. Compared with the model group, the SOD activity and NO content in the medium-dose and high-dose SAGPAF groups of treated with 10 kV cm -1 field intensity were significantly increased. The MDA content and MPO level were decreased significantly. They significantly reduced the gastric mucosal injury induced by ethanol (21.17 ± 3.51% and 13.99 ± 2.00%) and the histopathological scores (3.83 ± 0.40 and 4.33 ± 0.37) ( P < 0.05). Western blotting analysis showed that SAGPAF after pulsed electric field (PEF) treatment improved gastric injury by reducing protein phosphorylation. These findings provided strong evidence that PEF-treated SAGPAF enhanced the gastric mucosal barrier function by inhibiting the activation of the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathways, reducing the ethanol-induced inflammatory response and oxidative stress.

The detection of copper ions and hydrogen sulfide with high sensitivity and selectivity has become a research priority as they play a crucial role in physiopathological processes both in the human body and in the environment. Herein, a fluorescent chemosensor named FGP1 (FITC-Ahx-Ser-Ser-His-Thr-Glu-Phe-NH2) was developed using novel peptides. This chemosensor solely recognizes Cu2+ without any disruption by other metal ions that may compete. The binding of FGP1–Cu leads to the quenching of the FGP1 probe fluorescence with great sensitivity and rapid response time, resulting in a noticeable change of color observable to the naked eye. The association constant of FGP1–Cu is 7.34 × 105 M−1, and thus when S2− is added to the FGP1–Cu complexes, Cu2+ is removed and fluorescence is restored, resulting in an "off–on" process. The fluorescence titration measurements' detection limits, computed utilizing the 3σ/k equation, were 38.2 nM (Cu2+) and 37.9 nM (S2−). These values are considerably lower than the safe levels designated by the US EPA. Furthermore, on account of its favorable water solubility, high biocompatibility and low toxicity, the FGP1 probe proved effective in tracking Cu2+ and S2− in HeLa living cells using the fluorescence imaging technique. [ABSTRACT FROM AUTHOR]

Mycobacterial histidine-rich GroEL1 protein significantly differs from the well-known methionine-glycine-rich GroEL chaperonin and most preferably participates in Cu(II) homeostasis. Some GroEL1 proteins, however, do not possess six but only three histidine residues and more acidic residues that can function as binding sites for metal ions. To evaluate the importance of this difference, we examined and compared the properties of GroEL1 His-rich or Glu/His-rich C-terminal domains as ligands for Cu(II), Ni(II), and Zn(II) ions. We studied the stoichiometry, stability, and binding sites of Cu(II)/Ni(II)/Zn(II) complexes of two model peptides: XEN = Ac-DKPEEEEDGHGHAH (M. xenopi) and ABS = Ac-DKPAEEADHGHGHHGHAH (M. abscessus) in the pH range 2–11. In the case of Cu(II), Ni(II), and Zn(II) complexes of XEN and ABS, ABS always formed more stable complexes. For XEN, there seemed to be no preference for Ni(II) or Zn(II) ions. In contrast, for ABS, Zn(II) formed a complex that was slightly more stable than the one formed by Ni(II). This may be due to the 6 His residues, which preferentially interact with Zn(II) rather than Ni(II). The study identified that an equilibrium of complexes—known as polymorphism—may occur in ABS complexes. Therefore, distinct sets of histidine residues may be involved in metal binding. [ABSTRACT FROM AUTHOR]

Protein S-acylation is an important lipid modification characteristic for heterogeneity in the acyl chain and dynamicity in the acylation/deacylation cycle. Most S-acylproteomic research has been limited by indirect identification of modified proteins/peptides without attached fatty acids, resulting in the failure to precisely characterize S-acylated sites with attached fatty acids. The study of S-acylation turnover is still limited at the protein level. Herein, aiming to site-specifically profile both the heterogeneity and the turnover of S-acylation, we first developed a site-specific strategy for intact S-acylated peptide analysis by introducing an acid cleavable bioorthogonal tag into a metabolic labelling method (ssMLCC). The cleavable bioorthogonal tag allowed for the selective enrichment and efficient MS analysis of intact S-acylated peptides so that S-acylated sites and their attached fatty acids could be directly analysed, enabling the precise mapping of S-acylated sites, as well as circumventing false positives from previous studies. Moreover, 606 S-palmitoylated (C16:0) sites of 441 proteins in HeLa cells were identified. All types of S-acylated peptides were further characterized by an open search, providing site-specific profiling of acyl chain heterogeneity, including S-myristoylation, S-palmitoylation, S-palmitoleylation, and S-oleylation. Furthermore, site-specific monitoring of S-palmitoylation turnover was achieved by coupling with pulse-chase methods, facilitating the detailed observation of the dynamic event at each site in multi-palmitoylated proteins, and 85 rapidly cycling palmitoylated sites in 79 proteins were identified. This study provided a strategy for the precise and comprehensive analysis of protein S-acylation based on intact S-acylated peptide analysis, contributing to the further understanding of its complexity and biological functions. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides show promise in combating microbial infections in the age of rapidly growing resistance against antibiotics. The salt sensitivity of their activity, protease susceptibility, and cytotoxicity are some of the disadvantages that limit the commercial success of AMPs. In this study, the hydrophobic–hydrophilic balance of lipopeptides was tuned to generate a highly potent AMP, P18, which overcomes the limitations of the existing AMPs. P18 is a non-cytotoxic, salt-tolerant, and protease-resistant AMP, with no development of resistance over 16 generations in MRSA, which is highly potent against ESKAPE pathogens such as P. aeruginosa, K. pneumoniae, S. aureus, and methicillin-resistant S. aureus (MRSA). This study explores and establishes the direct effect of the hydrophobic–hydrophilic balance of peptides on their various properties such as secondary structure, self-assembly (morphology and kinetics), antimicrobial potency (salt-tolerance, kinetics, etc.), and protease-resistance ability. Thus, peptides with tailor-made properties and functions can be designed in the future by being able to control and tune their overall hydrophobic–hydrophilic balance. [ABSTRACT FROM AUTHOR]

Superoxide dismutase (SOD) enzymes are pivotal in regulating oxidative stress. In order to model Ni containing SOD enzymes, the results of the thermodynamic, spectroscopic and SOD activity studies on the complexes formed between nickel(II) and a NiSOD related peptide, CysCysAspLeuProCysGlyValTyr–NH2 (wtCC), are reported. Cysteine was introduced to replace the first histidine residue in the amino acid sequence of the active site of the NiSOD enzyme. The novel peptide exhibits 3 times higher metal binding affinity compared to the native NiSOD fragment. This is due to the presence of the first cysteine in the coordination sphere of nickel(II). At physiological pH, the (NH2,S–,S–,S–) coordinated complex is the major species. This coordination mode is altered when one thiolate group is replaced by an amide nitrogen of the peptide backbone above pH 7.5. The nickel complexes of wtCC exhibit similar SOD activity to that of the complex formed with the active site fragment of the native NiSOD. The reaction between the complexes and the superoxide anion was studied by the sequential stopped-flow method. These studies revealed that the nickel(II) complex is always in excess over the nickel(III) complex during the dismutation process. However, the nickel(III) species is also involved in a relatively fast degradation process. This unambiguously proves that a protective mechanism must be operative in the NiSOD enzyme which prevents the oxidation of the sulfur atom of cysteine in the presence of O2−. The results provide new possibilities for the use of NiSOD mimics in bio- and industrial catalytic processes. [ABSTRACT FROM AUTHOR]

Caspase-3 is an important biomarker for the process of apoptosis, which is a key target for cancer treatment. Due to its low concentration in single cells and the structural similarity of caspase family proteins, it is exceedingly challenging to accurately determine the intracellular caspase-3 during apoptosis in situ. Herein, a biosensing strategy based on the target-induced SERS "hot spot" formation has been developed for the simultaneous highly sensitive and selective detection of intracellular caspase-3 level. The nanosensor is composed of gold nanoparticles modified with the probe molecule 4-mercaptophenylboronic acid (4-MPBA) and a peptide chain. The well-designed peptide chain contains two distinct functional domains, one with a sulfhydryl group for bonding to the gold nanoparticles and the other a fragment specifically recognized by caspase-3. When caspase-3 is present, the negatively charged segment (NH2–Asp–Asp–Asp–Glu–Val–Asp–OH) of the peptide chain is specifically hydrolyzed, leaving a positively charged fragment coated on the surface of the gold nanoparticles. At this time, the golden nanoparticles undergo significant coupling aggregation due to the electrostatic interaction, resulting in a large number of SERS "hot spot" formation. The SERS signal of the 4-MPBA located at the nano-gap is significantly boosted because of the local plasma enhancement effect. The highly sensitive determination of caspase-3 can be achieved according to the altered SERS signal intensity of 4-MPBA. The turn-on of the SERS signal-induced target contributes to the excellent selectivity and the formation of the SERS "hot spot" effect that further improves the sensitivity of caspase-3 detection. The advantages of this biosensing technique allow for the precise in situ monitoring of the dynamic changes in caspase-3 levels during apoptosis. In addition, the differences in caspase-3 levels during the apoptosis of various cell types were compared. Monitoring the caspase-3 levels can be used to track the cellular apoptosis process, evaluate the effect of drugs on cancer cells in real time, and provide guidance for the selection of the appropriate drug dosage. [ABSTRACT FROM AUTHOR]

Marine cyclic peptides have become an important source for drug development. In this work, two novel cyclic peptide zygosporamide analogs with the isoindolinone fragment were prepared, which have broad-spectrum antitumor activity. We have tried to compare their bioactivities by changing the amino acid (R-3Leu and S-4Leu) configuration. Notably, compound 8, with R-3Leu and S-4Leu residues, showed better inhibiting ability than that of compound 9, which contains S-3Leu and R-4Leu residues. Furthermore, careful molecular docking indicated that compound 8 presented stronger binding with the EGFR protein of liver cancer cells, providing an explanation for the difference in bioactivity. This research has provided a useful guide for peptide-based drug-target design. [ABSTRACT FROM AUTHOR]

This paper presents compression molding of peptide assemblies with low-density polyethylene (LDPE) for the robust production of antimicrobial polymeric films. These films show a significant reduction of colony-forming units and plaque-forming units. Moreover, they significantly inhibited the growth of three different fungi. These innovative active polymeric films can potentially be applied for medical device wrapping, food packaging, and agriculture applications. [ABSTRACT FROM AUTHOR]

A novel point-of-care testing (POCT) method for the determination of proteases was developed for the first time using a designed disposable capillary-fill device based on the cleavage of electrogenerated chemiluminescence (ECL)-label-tagged peptide probes and enabling elimination of the light-shielding from the magnetic beads (MBs). As a proof-of-principle, prostate-specific antigen (PSA) was taken as a model analyte, and streptavidin-coated magnetic beads bound with ruthenium-complex-tagged specific peptide (biotin-HSSKLQK) were utilized as MB ECL probes. The capillary-fill device was designed to be divided into a reaction zone and detection zone. In the reaction zone, the bio-cleavage reaction between the PSA analyte with the peptide on the surface of the MB ECL probes occurred, while in the detection zone, ECL emission was produced by a screen-printed carbon electrode, Ag/AgCl reference electrode and carbon counter electrode. When the analyte PSA was introduced into the suspension of MB ECL probes in the reaction zone of the device, biocleavage of the peptide occurred, and the cleaved Ru1 part was released from the surface of the MB ECL probes. The capillary-filled device was tilted 90°, and with the aid of gravity, the solution containing the released Ru1 part flowed to the surface of the working electrode in the detection region of the device, while the MB ECL probes were fixed in the reaction zone by an external magnet. PSA can be determined by the ECL emission from the released Ru1 part in the presence of the co-reactant tri-n-propylamine at the detection zone. Under the optimal conditions, the developed ECL method showed a low detection limit of 0.12 ng mL−1 for PSA. This work demonstrates that the developed ECL biosensing approach can eliminate the MB light-shielding effect and quantify proteases with high sensitivity and selectivity, which could be easily extended to POCT-based ECL biosensing for other proteases. [ABSTRACT FROM AUTHOR]

The default choice of mobile phase acidifier for bottom-up LC-MS proteomic analyses is 0.10% formic acid because of its decent acidity, decent ion pairing ability, and low suppression of electrospray ionization. In recent years, state-of-the-art columns have been designed specifically to provide efficient separation even when using an MS-friendly mobile phase of low ionic strength. Despite this, no attempts have been made to improve the sensitivity of the MS-based analytical methods by reducing the amount of formic acid in the mobile phase. In this study, we evaluated the effect of reduced formic acid concentration in the mobile phase on the chromatographic behavior and MS response of peptides when separated using columns packed with a C18 stationary phase with a positively charged surface. Using 0.01% formic acid in the mobile phase maintained excellent chromatographic performance and increased MS signal response compared to the standard of 0.10%. The enhanced MS response translated to about 50% improved peptide identifications depending on the complexity and amount of sample injected. The increased retention of peptides at a reduced formic acid concentration was directly proportional to the number of acidic residues in the peptide sequence. The study was carried out by covering a spectrum of protein samples with varied complexity using analytical flow, micro-, and nanoflow regimes to expand the applicability in routine practice. [ABSTRACT FROM AUTHOR]

The exploitation of available self-assembled systems for the effective uptake and release of hydrophobic antitumor or antiviral drugs in cells remains a great challenge. Oligopeptides are highly promising candidates among the multitudinous self-assembled biomaterial systems, owing to their unique properties of sequence adjustability, self-assembly, good biocompatibility, etc. Here, an amphiphilic peptide (Pep1) was designed and synthesized, and can self-assemble into nanoblocks with a size of 100–150 nm and a height of 34 nm upon crosslinking with PO43−. The assembly mechanism of the nanoblocks was elucidated, and the assembly was found to be driven by synergistic interactions, including the hydrophobic effect, electrostatic interactions, directional H-bonds and polar zippers derived from hydrophilic residues. Moreover, the Pep1/PO43− nanoblocks can not only encase drug molecules with a favourable loading rate and rapid release in the presence of trypsin, but also show good biocompatibility. This work may promote the development of self-assembled systems based on peptides for prominent future biomedical applications. [ABSTRACT FROM AUTHOR]

Particular interest has been focused on the modulation of solid state charge transport in proteins via π–π interactions. Nevertheless, molecular design with the π–π interaction mode for electronic applications remains a challenge in light of the complexity of protein structures. Here, we investigate the pattern of regulating peptide charge transport via different types of π–π interactions in peptide-based frameworks. We applied aromatic amino acid containing peptides labelled with a 1-methyl-1′-aminoethyl-4,4′-bipyridinium salt (MV2+) to construct well-defined self-assembled monolayers as the model. When the π–π interactions are improved by the size of aromatic amino acid side chains, the peptide charge transport can be promoted mainly by the reduced energy barrier and not by the weakened peptide−electrode coupling. When the π–π interactions are attenuated rapidly by increasing the distance between aromatic groups, the molecule–electrode coupling is enhanced sharply, which becomes the main factor to facilitate the charge transport. [ABSTRACT FROM AUTHOR]

Photorelease complexes represent a class of agents for which UV-visible light triggers the expulsion of a specfic molecule that is intrinsically part of the inner coordination sphere or held in close proximity to the metal centre. The reaction does not occur in the ground-state complex and requires a photon, but an additional agent may be present that facilitates the release process. In this context, the perspective article covers recent papers from the past five years (2017–2021) on metal-based complexes containing ligands that are expelled under light activation. In addition, the examples primarily focus on ligands with potential biological activity and have specfic therapeutic applications. Some examples include NO, CO, Cl−, peptides, pharmacophores and redox-active compounds. [ABSTRACT FROM AUTHOR]

The structure of biomolecules play an important role in biomineral formation and studies about the regulation behavior of biominerals by changing biomolecular structures are of great help in understanding biomineralization phenomena. In this study, using the N-terminal of amelogenin as a model molecule, we studied its secondary structure change in H2O and 30% acetonitrile–H2O (30% Ace–H2O), and the regulation of calcite growth by phosphorylated amelogenin N-terminal (P) and non-phosphorylated amelogenin N-terminal (NP) with different secondary structures. We found that both peptides show a random coil conformation in H2O, which changes into an α-helix and β-sheet mixed conformation in 30% Ace–H2O, and a random coil and α-helix mixed conformation after adding Ca2+. Addition of the P peptide to the H2O crystallization system can yield calcite with occluded peptides while the NP peptide shows little effect on calcite growth. However, the P peptide can promote the dimers, helix trimers or helix crystal clusters formation while the growth habits of calcite can be hardly influenced by NP peptides in 30% Ace–H2O. Besides, the α-helix structure of the P peptide can provide more nucleation sites for calcium carbonate and promote the helical growth of the calcite crystal in 30% Ace–H2O, while the random coil conformation in H2O leads to electrostatic adsorption on the calcite surface and occlusion inside calcite crystals. This work demonstrated that the function of phosphorylated organic additives can be enhanced by changing the secondary structure of the organic matrix and may provide a new strategy for novel crystal synthesis. [ABSTRACT FROM AUTHOR]

Noroviruses are highly contagious and are one of the leading causes of acute gastroenteritis worldwide. Due to a lack of effective antiviral therapies, there is a need to diagnose and surveil norovirus infections to implement quarantine protocols and prevent large outbreaks. Currently, the gold standard of diagnosis uses reverse transcription polymerase chain reaction (RT-PCR), but PCR can have limited availability. Here, we propose a combination of a tunable peptide substrate and gold nanoparticles (AuNPs) to colorimetrically detect the Southampton norovirus 3C-like protease (SV3CP), a key protease in viral replication. Careful design of the substrate employs a zwitterionic peptide with opposite charged moieties on the C- and N- termini to induce a rapid color change visible to the naked eye; thus, this color change is indicative of SV3CP activity. This work expands on existing zwitterionic peptide strategies for protease detection by systematically evaluating the effects of lysine and arginine on nanoparticle charge screening. We also determine a limit of detection for SV3CP of 28.0 nM with comparable results in external breath condensate, urine, and fecal matter for 100 nM of SV3CP. The key advantage of this system is its simplicity and accessibility, thus making it an attractive tool for qualitative point-of-care diagnostics. [ABSTRACT FROM AUTHOR]

The effects of replacement with aza groups in the proline ring on the conformational preference and prolyl cis–trans isomerization were investigated for Ac-X-OMe (X = α-azPro, β-azPro, γ-azPro, and δ-azPro) using DFT methods with an implicit solvation model in water. In addition, we studied the propensity to form the PPII structure for Ac-(Pro)5-NMe2 and Ac-(Hyp-Gly-Pro)2-NMe2 as the polyproline model peptide (PMP) and the single-strand collagen model peptide (CMP), respectively, with the incorporation of azPro residues in the middle of each model peptide in water. The calculated results indicated that the incorporation of the aza group in the proline ring induced different conformational preferences of the Pro residue depending on the substitution position. In particular, the α-azPro residue was expected to provide conformational adaptability of the α-azPro residue in the various Pro-containing peptides. Compared to the cis population of Ac-Pro-OMe, there was an increase in cis population for the α-azPro, β-azPro, and γ-azPro peptides, whereas a greater decrease was found for Ac-δ-azPro-OMe. The ΔG ‡tc barrier to trans-to-cis isomerization decreased by 2.5–7.2 kcal mol−1 due to the incorporation of azPro and the greatest decrease was found for Ac-α-azPro-OMe, which was ascribed to the weakened C–N bond of the trans and ts conformers. The substitution with all azPro residues enhanced the propensity to form the PPII structure of PMP. In the case of CMP1, the replacement of Pro with γ-azPro(d) and δ-azPro(d) enhanced the stability of the PPII structure more by 2.47 and 2.24 kcal mol−1 than the canonical CMP. However, the relative propensity to form the PPII structure was diminished by 1–4 kcal mol−1 for all CMP2 with the replacement of Hyp compared to the canonical CMP. Hence, we deduced that the replacement of Pro with γ-azPro(d) or δ-azPro(d) in the single strand of (Hyp-Gly-Pro)n can enhance the preorganization of the PPII structure and may lead to an increase in triple helix stability. [ABSTRACT FROM AUTHOR]

Self-assembling peptides are of huge interest for biological, medical and nanotechnological applications. The enormous chemical variety that is available from the 20 amino acids offers potentially unlimited peptide sequences, but it is currently an issue to predict their supramolecular behavior in a reliable and cheap way. Herein we report a computational method to screen and forecast the aqueous self-assembly propensity of amyloidogenic pentapeptides. This method was found also as an interesting tool to predict peptide crystallinity, which may be of interest for the development of peptide based drugs. [ABSTRACT FROM AUTHOR]

Among various exosomal proteins, matrix metalloproteinases (MMPs) are a family of membrane associated endopeptidases and have been considered as potential biomarkers in liquid biopsy owing to their multiple roles in pathological processes. However, the potential of MMP14 expression (MMP14-E) and MMP14 proteolytic activity (MMP14-A) in clinical diagnosis is still not clear due to the lack of sensitive and simultaneous detection techniques. Herein, we propose a fluorescent nanosensor for the simultaneous detection of MMP14-E and MMP14-A using a spherical aptamer/peptide dual-probe strategy. The aptamer and peptide probes were sequentially immobilized on Fe3O4 magnetic nanoparticles coated with gold nanoparticles (m-AuNPs) using a disulfide linker. MMP14 can be specifically recognized by the aptamer, while the proteolytic-active MMP14 can cleave the peptide probe. While achieving simultaneous detection, the proposed sensor provides better analytical performances than traditional MMP14 sensors owing to the m-AuNP-based spherical dual-probe strategy. This sensor has been successfully applied for the detection of exosomal MMP14 from cell culture media and real serum samples. Levels of both MMP14-E and MMP14-A increase in serum from cancer patients, indicating their potential applications as biomarkers in liquid biopsy for disease diagnosis and real-time surveillance. [ABSTRACT FROM AUTHOR]