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A study analyzes the T cell receptor (TCR) recognition of a peptide bound and presented by a major histocompatibility complex (MHC) molecule, which normally comes about in two steps. The results of the analysis were of great help and will be definitely useful in understanding the nature of the TCR binding transition states, which makes it recognize the composite peptide/MHC surface.

[Super 31]P NMR was employed to establish that EDAC (1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide)-mediated reactions between primary amines and polyphosphate result in phosphoramidate linkages with the terminal phosphate groups. The findings from the study provide new pathways for the entire armamentarium of protein chemistry to modifying polyphosphate and conduct future studies to understand its biological roles.

Membranes play key regulatory roles in biological processes, with bilayer composition exerting marked effects on binding affinities and catalytic activities of a number of membrane-associated proteins. In particular, proteins involved in diverse processes such as vesicle fusion, intracellular signaling cascades, and blood coagulation interact specifically with anionic lipids such as phosphatidylserine (PS) in the presence of Ca2+ ions. While Ca2+ is suspected to induce PS clustering in mixed phospholipid bilayers, the detailed structural effects of this ion on anionic lipids are not established. In this study, combining magic angle spinning (MAS) solid-state NMR (SSNMR) measurements of isotopically labeled serine headgroups in mixed lipid bilayers with molecular dynamics (MD) simulations of PS lipid bilayers in the presence of different counterions, we provide site-resolved insights into the effects of Ca2+ on the structure and dynamics of lipid bilayers. Ca2+-induced conformational changes of PS in mixed bilayers are observed in both liposomes and Nanodiscs, a nanoscale membrane mimetic of bilayer patches. Site-resolved multidimensional correlation SSNMR spectra of bilayers containing 13C,15N-labeled PS demonstrate that Ca2+ ions promote two major PS headgroup conformations, which are well resolved in two-dimensional 13C-13C, 15N-13C, and 31P-13C spectra. The results of MD simulations performed on PS lipid bilayers in the presence or absence of Ca2+ provide an atomic view of the conformational effects underlying the observed spectra. [ABSTRACT FROM AUTHOR]