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Abstract: Folding of polytopic transmembrane proteins involves interactions of individual transmembrane helices, and multiple TM helix–helix interactions need to be controlled and aligned to result in the final TM protein structure. While defined interaction motifs, such as the GxxxG motif, might be critically involved in transmembrane helix–helix interactions, the sequence context as well as lipid bilayer properties significantly modulate the strength of a sequence specific transmembrane helix–helix interaction. Structures of 11 transmembrane helix dimers have been described today, and the influence of the sequence context as well as of the detergent and lipid environment on a sequence specific dimerization is discussed in light of the available structural information. This article is part of a Special Issue entitled: Protein Folding in Membranes. [Copyright &y& Elsevier]

Highlights: [•] In situ preparation of silver nanoparticles based on homologues series of amphiphilic N-acyl tyramines. [•] Size and shape of the AgNPs were not altered by varying the acyl chain length of NATA. [•] NATA-AgNPs show remarkable catalytic activity in the reduction of nitroaromatics. [•] Rate of the reduction reaction is directly related to the capping agent hydrophobicity. [Copyright &y& Elsevier]

Abstract A simple single-stage method, based on refluxing edible carrot with aqueous trisodium phosphate (TSP) has been reported to synthesize blue color luminescent carbon dots (CDs). Transmission electron microscopy (TEM) image showed that CDs are almost spherical in shape and the size is around 3–8 nm. Fourier-transform infrared (FTIR) and 1H NMR spectroscopy study revealed that the carbohydrates present in the carrot undergone carbonization to produce luminescent CDs. Optimization study indicate that refluxing 5 g of carrot in 80 mM TSP aqueous solution for 120 min is adequate to produce highly luminescent blue CDs. The CDs produced are used as luminophore to image bacteria through fluorescence microscopy. CDs have membrane good permeability and minimum toxicity against Gram-negative and Gram-positive bacteria. The CDs capability for direct reduction of silver ions to elemental silver (Ag0) and gold ions to elemental gold (Au0) without additional reducing and stabilizing agent was demonstrated. The resulting Ag and Au nanoparticles have a size of 8–22 nm and 5–15 nm, respectively. The catalytic activity of nanoparticles in the hydrogenation reaction was investigated. The results suggest that the nanoparticles had high catalytic activity in the sodium borohydride mediated hydrogenation of nitroaromatic compounds. Graphical abstract Unlabelled Image Highlights • Easily adaptable procedure to synthesis carbon dots was reported. • CDs has good membrane permeability to label live cells. • CDs reduces silver and gold ions into nanoparticles. • Silver and gold nanoparticles exhibit good catalytic activity. [ABSTRACT FROM AUTHOR]

Heavy metals released by anthropogenic activities are extremely toxic to animals and plants due to their bioaccumulative and persistent environmental presence. In the current study, silver nanoparticles (AgNPs) were synthesized utilizing eco-friendly processes, and their potential in colorimetric Hg2+ ion sensing in environmental samples was examined. An aqueous extract of Hemidesmus indicus root (Sarsaparilla Root, ISR) rapidly converts silver ions into AgNPs within 5 min of exposure to sunlight. Transmission electron microscopy confirms that ISR-AgNPs are spherical, ranging from 15 to 35 nm. Fourier-transform infrared spectroscopy revealed phytomolecules stabilized the NPs with hydroxyl and carbonyl substituents. The ISR-AgNPs detect Hg2+ ions by a colour change that can be seen with the naked eye within 1 min. The probe is interference-free and detects the presence of Hg2+ ions in sewage water. A method for fabricating ISR-AgNPs onto paper was disclosed, and this portable ISR-AgNPs embedded paper device was found to be good at sensing mercury present in the water. The findings show that environmentally friendly synthesized AgNPs can contribute to developing onsite colorimetric sensors. [Display omitted] • Rapid silver nanoparticles synthesis using sunlight and Hemidesmus indicus root extract. • Phytochemicals stabilize the AgNPs. • Paper fabricated with AgNPs sense mercury with good selectivity. • AgNPs disrupt bacterial membranes and kill them. [ABSTRACT FROM AUTHOR]

The organic transformations in water are considered a safe, non-toxic, economical, and eco-friendly alternative. A new series of amphiphile, N -acyl- N -(pyridin-2-ylmethyl)glycine (PyNAG) with variable hydrophobicity was successfully synthesized from glycine. The self-assembly properties were characterized by critical micellar concentration (CMC), aggregation number (N agg), and diameter (D H). The PyNAG with N - stearoyl moiety showed lower CMC, higher N agg , and larger D H compared to PyNAG with N - lauryl moiety. Molecular dynamics simulation reveals that the micelle structure is compact and non-bonded energy contribution arises from electrostatic, and van der Walls forces contribute to perfect packing and micelle formation. The ability of the PyNAG micelles to execute important organic transformations in water was demonstrated through synthesizing chromenoquinoline via the Povarov reaction. Micelles with varying diameters were used to conduct the Povarov reaction in order to better understand the functions of the hydrophobicity core of the micellar environment in organic reactions. The results reveal that the Povarov reaction produces a good yield in N -stearoyl- N -(pyridin-2-ylmethyl)glycine (PyN18G) micelles, better than organic solvent and commercial surfactant. Moreover, a linear correlation between the yield and the hydrophobicity of the PyNAG was observed. The findings demonstrate that the micellar interior significantly affects the reactivity of the substrate, which should be taken into consideration while creating new media for metal-catalyzed green synthesis. [Display omitted] • Reported micelle formation from pyridine tethered N-acyl glycine. • Electrostatic and van der Walls forces contributes for micelle packing. • Micelles serves as a medium for Povarov reaction on water. • Micelle hydrophobicity play significant role in chromenoquinoline synthesis. [ABSTRACT FROM AUTHOR]

A new pyrene-appended polypyridine ligand, wherein the 1,10-phenanthroline (phen) and the photoactive pyrene chromophore is connected via a C N bond; N-[1,10]phenanthrolin-5-yl-pyrenylmethanimine (ppym) and its complex [Ru(phen) 2 ( ppym ) ] 2+ was synthesized. Characterization of the ligand and the complex was investigated through elemental analysis, UV-vis, IR, 1 H NMR, MALDI-TOF mass and cyclic voltammetry techniques. The change in dipole moment of the ground and the excited state of the chromophores with the different solvent polarity was examined. The dual emission (Excimer) characteristics observed for ligand ppym has been probed by detailed photophysical studies involving variable concentration, excitation wavelength and solvent experiments and also transition metal ion induced quenching data. 3 MLCT emission was observed for [Ru(phen) 2 ( ppym ) ] 2+ . Absorption, emission, thermal melting and viscosity studies reveal that [Ru(phen) 2 ( ppym ) ] 2+ bind to CT DNA avidly and that ruthenium-bound ppym intercalate inside the base sets of the duplex. Also, the DNA photonicking activity (pBR 322 DNA, λ exc  = 450 nm) of [Ru(phen) 2 ( ppym ) ] 2+ is almost four times higher than [Ru(phen) 3 ] 2+ . Through inhibitor studies, we found that reactive oxygen species play a major role in the photo cleavage of [Ru(phen) 2 ( ppym ) ] 2+ . The cytotoxicity of the complex was tested in Human cancer cell line (ZR-75-30) by MTT assay. In addition, modeling studies scaffold the intercalative binding to the d(CGCAATTGCG) 2 sequence. [ABSTRACT FROM AUTHOR]

In any therapeutic modality the usage of drug in high doses often leads to serious side-effects. Herein, we demonstrated a method to enhance the antibacterial efficacy of CuS NPs at lower concentration through interacting with jackfruit seed lectin, jacalin. Fluorescence quenching studies revealed that jacalin form complex with CuS NPs and the association constant was 1.91 × 10 4  M −1 . Upon complex with jacalin, the bacterial minimum inhibitory concentration (MIC) of CuS NPs drastically decreases from 12.5 μM to 0.78 μM. The addition of jacalin specific sugar, galactose to jacalin-CuS NPs complex (JCuS NPs) reverses the MIC from 0.78 μM to 25 μM. Mechanistic study suggests that JCuS NPs kills bacteria in part by reactive oxygen species and membrane damage, but galactose prevents the action of JCuS NPs at 0.78 μM. JCuS NPs successfully reduce (14 fold) A. hydrophila colonization in an infected zerbra fish and rescue them completely from the infection, but galJCuS NPs and CuS NPs were ineffective at 0.78 μM. Collectively, our studies demonstrates that the enhance antibacterial activity of JCuS NPs is likely due to the interaction between the galactose binding site of jacalin and the bacterial strains, as a result NPs are targeted and delivered sufficiently. [ABSTRACT FROM AUTHOR]

N -acyltaurines (NATs) are biologically active amphiphilic lipids. They come under the group of compounds known as N -acyl amino acids. NATs were first detected in the brain and other tissues in mice lacking the enzyme fatty acid amide hydrolase FAAH (−/−). N -arachidonoyltaurine (20:4 NAT) acts as an excellent ligand for the subset of transient receptor potential (TRP) channels, especially vanilloid type channels TRPV1 and TRPV4. Also, hydrophobic and hydrophilic regions of NATs enable them to interact with membrane lipids. Here, we have investigated the interaction of NATs, N -myristoyltaurine (NMT), and N -palmitoyltaurine (NPT) with their corresponding diacyl phosphatidylcholines (PCs), dimyristoylphosphatidylcholine (DMPC), and dipalmitoylphosphatidylchoine (DPPC). The miscibility and phase behavior of the hydrated binary mixtures have been investigated by differential scanning calorimetry (DSC). Studies on the interaction of NMT/NPT with DMPC/DPPC revealed that the two amphiphiles mix well up to 50 mol% of NAT and phase separation is observed at higher contents of the NAT. The phase transition of the equimolar mixtures of NAT:PC (50:50) studied by fluorescence, also supported the DSC results. PXRD and FTIR analysis show that the NAT:PC equimolar mixture (50:50) forms different supramolecular structures when compared to that of individual NATs and PCs. From transmission electron microscopic studies it is observed that the equimolar mixtures of NMT and NPT with their corresponding diacylphosphatidylcholines (50:50, mol/mol) forms unilamellar vesicles whose diameter range between 30 and 50 nm. [Display omitted] • N -acyltaurines (NATs) are structurally related to endocannabinoids, that contain taurine moiety as their polar head group • In DSC Studies of NATs with PCs, two lipids mix well up to 50 mol% and phase separation is noticed at higher NAT content • PXRD and FTIR analysis revealed that the supramolecular structure of equimolar mixtures of NATs and PCs are altered • TEM result shows that the equimolar mixtures of NATs with PCs (50:50, mol/mol) form spherical unilamellar vesicles • These interesting properties of NATs hint at their potential in drug delivery and drug formulation applications. [ABSTRACT FROM AUTHOR]

In this paper, the application of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) synthesized using a biomimetic lipid, N-myristoyltaurine (N14T) was evaluated in common fields. The catalytic effectiveness of AgNPs and AuNPs was studied in the popular nanocatalyst reaction, nitroaromatic reduction, and dye degradation. Both NPs display catalytic activity in the nitroaromatic compound and organic dyes reduction reaction involving sodium borohydride and the rate constant is estimated as 10−3 s−1. Strikingly, the reaction initiation time (t 0) and completion time (t c) differ significantly between AgNPs and AuNPs. Analyzing the reaction kinetic profile revealed that the reaction carried out with AuNPs showed a shorter t 0 and t c , suggesting a better catalyst than AgNPs. In addition, the efficiency of the NPs was examined in Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli , Pseudomonas aeruginosa). In difference to the catalytic study, AuNPs display poor antibacterial activity. Whereas AgNPs kill the tested bacteria at 250 μM via disturbing bacterial membrane integrity and produce excess reactive oxygen species. The toxicology study carried out with zebrafish animal model reveals that both AgNPs and AuNPs are non-toxic. The findings suggest that each nanomaterial possesses unique physicochemical properties irrespective of stabilization with the same molecules. •Both NPs display catalytic activity in the nitroaromatic compound and organic dyes reduction •the reaction initiation time (t0) and completion time (tc) differ significantly between AgNPs and AuNPs. • the reaction carried out with AuNPs showed a shorter t0 and tc, suggesting a better catalyst than AgNPs. •The toxicology study carried out with zebrafish animal model reveals that both AgNPs and AuNPs are non-toxic. [ABSTRACT FROM AUTHOR]

The rising threat to antibiotic armamentarium demand innovative methods to use standard antibiotics against multidrug-resistant (MDR) pathogens. Herein, we demonstrated phytolectin-cationic lipid complex have the ability to renew the ciprofloxacin (CIP) activity against MDR uropathogenic Escherichia coli (R4UPEC). The minimum inhibitory concentrations (MIC) obtained for CIP against R4UPEC studied were very high (MIC = 1000 µM) which may not be suitable for clinical testing. Strikingly, CIP in combination with Butea monosperma seed lectin (BMSL) and cationic lipid, 2-((N-(2-hydroxyethyl)palmitamido)methyl)− 1-methylpyridin-1-ium iodide (cN16E) showed 64-fold lower MIC (15.63 µM). Checkerboard assay revealed that the BMSL-cN16E (BcN16E) complex and CIP work synergistically against R4UPEC. The complex, BcN16E-CIP exerts antimicrobial activity through outer membrane permeabilization, inner membrane disruption, proton motive force dissipation and enhancing the generation of reactive oxygen species. The therapeutic efficacy evaluated in a zebrafish, intramuscular infection model using R4UPEC, the BcN16E-CIP reduce the bacterial load and decrease neutrophil infiltration in muscles and low down the liver cell necrosis. The results demonstrate significantly lower MIC for CIP when complex with BcN16E and showed exceptional in vivo efficacy against infectious MDR bacteria. [Display omitted] • Phytolectin-lipid conjugates enhance ciprofloxacin activity. • Antimicrobial mechanism attributed to modulation in outer and inner membrane. • The conjugate inhibits the efflux pumps. • Treatment with conjugate rescue the multidrug-resistant infected zebrafish. [ABSTRACT FROM AUTHOR]

6-azauridine (AzU), a pyrimidine nucleoside antimetabolite, was known to inhibit the growth of microorganism and transplantable tumors. The binding affinity of AzU to blood serum proteins might influence the effectiveness of the drug. Herein, we investigated the interaction of AzU with bovine serum albumin (BSA) under near physiological conditions. Fluorescence spectroscopy analysis revealed that AzU strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and a non-radiation energy transfer occurred within the molecules. Thermodynamic parameter determined from the temperature dependent binding constant suggests that the interaction of AzU with BSA is governed by enthalpic forces with a negative entropic contribution. Displacement studies and protein/drug docking studies suggest that AzU binds non-competitively to both sub-domain IIA and sub-domain IIIA of BSA. The obtained results reveal that AzU can bind to BSA with considerable affinity even in the presence of coexisting drug and can be used along with other drugs. [ABSTRACT FROM AUTHOR]

γ-Secretase is critically involved in the Notch pathway and in Alzheimer's disease. The four subunits of γ-secretase assemble in the endoplasmic reticulum (ER) and unassembled subunits are retained/retrieved to the ER by specific signals. We here describe a novel ER-retention/retrieval signal in the transmembrane domain (TMD) 4 of presenilin 1, a subunit of γ-secretase. TMD4 also is essential for complex formation, conferring a dual role for this domain. Likewise, TMD1 of Pen2 is bifunctional as well. It carries an ER-retention/retrieval signal and is important for complex assembly by binding to TMD4. The two TMDs directly interact with each other and mask their respective ER-retention/retrieval signals, allowing surface transport of reporter proteins. Our data suggest a model how assembly of Pen2 into the nascent γ-secretase complex could mask TMD-based ER-retention/retrieval signals to allow plasma membrane transport of fully assembled γ-secretase. [ABSTRACT FROM AUTHOR]

Functionalizing the nanoparticles to target the bacteria surface is an effective approach to curb drug resistance pathogens. The present study describes the synthesis of N-myristoyltaurine capped silver nanoparticles (AgNPs) and functionalization of AgNPs with jacalin (JAgNPs), a lectin from the seeds of Artocarpus integrifolia. JAgNPs has fourfold lower minimum inhibitory concentration than AgNPs and kills the S. aureus in less than 30 min through inducing oxidative stress and membrane damage. JAgNPs (31.25 µM) was found to have excellent biofilm inhibitory activity at lower concentration than AgNPs (62.5 µM). This was judged by crystal violet assay, light microscopy imaging and confocal laser scanning microscopy (CLSM) method. CLSM analysis reveals that JAgNPs is highly effective as compared to AgNPs in reducing the bio-volume and average biofilm thickness to 18.3 ± 2.5 µm3/µm2 and 14.0 ± 2.6 µm, respectively. Scanning electron microscopy (SEM) study reveals that JAgNPs prevents the colony formation and inhibited exopolysaccharide synthesis, thereby reducing the formation of biofilm. At minimum biofilm inhibitory concentrations, SEM and double staining technique using CLSM provides evidence that cells are intact and live, suggesting that NPs exhibit true biofilm activity. The findings indicate that jacalin functionalization may offer a unique way to use nanosilver at lower concentrations for treating infection associated with S. aureus biofilm. [Display omitted] • Jacalin functionalized AgNPs kills S. aureus in less than 30 min. • NPs exert antibacterial activity through inducing oxidative stress and membrane damage. • Jacalin-AgNPs exhibit antibiofilm activity at 0.5X MIC. • NPs inhibits exopolysaccharide biosynthesis. [ABSTRACT FROM AUTHOR]