Pro stabilization in prolyl carbamates influenced by tetrel bonding interactions.

NMR spectral and theoretical analyses of homologous prolyl carbamates reveal subtle charge transfer tetrel bonding interactions (TBIs), selectively stabilizing their Pro rotamers. These TBIs involve C-terminal-amide to N-terminal carbamate carbonyl-carbonyl (n → π* type) followed by intra-carbamate (n → σ* type) charge transfer interactions exclusively in the Pro motif. The number of TBIs and hence the Pro stability increase with increasing number of C groups at the carbamate alcohol.

Understanding the anomaly of cis-trans isomerism in Pro-His sequence.

The anomalous absence of cisPro stabilizing CH···π interactions at Xaa-Pro-Aro exclusively when Aro is His, is understood by NMR structural analyses of model peptides, as due to i → i backbone-side chain C H-bond that forms uniquely when Aro is His, which significantly decreases its χ-g population essential for CH···π formation.

α-Helices propagating from stable nucleators exhibit unconventional thermal folding.

Although the effect of thermal perturbations on protein structure has long been modeled in helical peptides, several details, such as the relation between the thermal stabilities of the propagating and nucleating segments of helices, remain elusive. We had earlier reported on the helix-nucleating propensities of covalent H-bond surrogate-constrained α-turns. Here, we analyze the thermal stabilities of helices that propagate along peptides appended to these α-helix nucleators using their NMR and far-UV CD spectra.

Hydrogen Bond Surrogate-Constrained Dynamic Antiparallel β-Sheets.

Antiparallel β-sheets are important secondary structures within proteins that equilibrate with random-coil states; however, little is known about the exact dynamics of this process. Here, the first dynamic β-sheet models that mimic this equilibrium have been designed by using an H-bond surrogate that introduces constraint and torque into a tertiary amide bond. 2D NMR data sufficiently reveal the structure, kinetics, and thermodynamics of the folding process, thereby leading the way to similar analysis in isolated biologically relevant β-sheets.