Deciphering the Conformations of Glutathione Oxidized Peptide: A Comparative NMR Study in Solution and Solid-State Environments.

Glutathione (GSH) and its oxidized dimer (GSSG) play an important role in living systems as an antioxidant, balancing the presence of reactive oxygen species (ROS). The central thiol (-S-S-) bond in GSSG can undergo free rotation, providing multiple conformations with respect to the S-S bridge. The six titratable sites of GSSG, which are influenced by pH variations, affect these conformations in solution, whereas in solids, additionally crystal packing effects come into play.

Proteolytically Stable ααγ-Hybrid Peptides Inhibit the Aggregation and Cytotoxicity of Aβ.

The recent approval of antibody-based therapy for targeting the clearance of amyloid plaques fuels the research in designing small molecules and peptide inhibitors to target the aggregation of Aβ-peptides. Here, we report that the 15-residue ααγ-hybrid peptide not only inhibits the aggregation of soluble Aβ into fibrils but also disintegrates the aggregated Aβ fibrils into smaller assemblies. Further, the hybrid peptide completely rescues neuronal cells from the toxicity of Aβ at equimolar concentrations.

Structural analysis of the AICD central 12 residue peptide stretch and its interactions with metals and polyphenols, as a potential drug target for AD.

Structural analysis of the central 12 residue stretch of Amyloid precursor protein Intracellular Domain (AICD: T-S-I-H-H-G-V-V-E-V-D-A) was carried out by NMR and homology modeling. Further, metal and polyphenol interactions were also carried out for these 12 residues stretch, as it contains two critical Histidine residues, which were observed to be perturbed NMR. A full length 57 residues AICD model was generated computational methods, to ascertain its overall conformation, as the entire structure was unavailable.

A cationic amphiphilic peptide chaperone rescues Aβ aggregation and cytotoxicity.

Directing Aβ to adopt a conformation that is free from aggregation and cell toxicity is an attractive and viable strategy to design therapeutics for Alzheimer's disease. Over the years, extensive efforts have been made to disrupt the aggregation of Aβ using various types of inhibitors but with limited success. Herein, we report the inhibition of aggregation of Aβ and disintegration of matured fibrils of Aβ into smaller assemblies by a 15-mer cationic amphiphilic peptide.

Characterization of (Boc-Cys/Sec-NHMe) and (Boc-Cys/Sec-OMe) : Evidence of local conformational difference between disulfide and diselenide.

Conformations of disulfide and diselenide were compared in (Boc-Cys/Sec-NHMe) and (Boc-Cys/Sec-OMe) using X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, density functional theory (DFT), and circular dichroism (CD) spectroscopy. Conformations of disulfide/diselenide in polypeptides are defined based on the sign of side chain torsion angle χ (-CH -S/Se-S/Se-CH -); negative indicates left-handed and positive indicates right-handed orientation. In the crystals of (Boc-Cys-OMe) and (Boc-Sec-OMe) , the disulfide exhibits a left-handed and the diselenide a right-handed orientation.

Conformational heterogeneity in tails of DNA-binding proteins is augmented by proline containing repeats.

A cationic terminal extension or tail is a common feature of many DNA-binding proteins. We show that a particular type of tail rich in proline, alanine and lysine belongs to the class of 'flexible disorder' and consists of characteristic pentapeptide repeats. Our designed peptides, (AAKKA) and (PAKKA), represent the tails of several bacterial DNA-binding proteins.