Dimerization of single-pass membrane receptors is essential for activation. In the human thrombopoietin receptor (TpoR), a unique amphipathic RWQFP motif separates the transmembrane (TM) and intracellular domains. Using a combination of mutagenesis, spectroscopy, and biochemical assays, we show that W515 of this motif impairs dimerization of the upstream TpoR TM helix. TpoR is unusual in that a...

The pressure drop of single phase was studied experimentally with non-Newtonian fluids of Carboxy Methyl Cellulose (CMC). Single helical coil with five different helix angles were used in this study to identify the effect of helix angle on pressure drop. The effect of helix angle is significant in moderate and high generalized Dean’s number of laminar region. The effect is insignificant in low ...

This paper presents a statistical analysis of helix-helix packing in 1290 high-resolution globular protein structures with less than 20 percent homology. Orientational preferences in helix packing are shown to be dominated by interactions between helices that are proximal in sequence. Such sequentially proximal interactions have a higher frequency of occurrence than sequentially distal interact...

Using a chemical cross-linking procedure, surface-grafted polyglutamate films with a permanently perpendicular helix orientation were prepared. A surface-grafted alpha-helical polyglutamate film containing polymerizable side groups was synthesized by ring-opening terpolymerization of 50 molar% gamma-methyl-L-glutamate N-carboxyanhydride (NCA), 30% gamma-stearyl-L-glutamate NCA and 20% gamma-4-v...

The dependence of local left ventricular (LV) mechanics on myocardial muscle fiber orientation was investigated using a finite element model. In the model we have considered anisotropy of the active and passive components of myocardial tissue, dependence of active stress on time, strain and strain rate, activation sequence of the LV wall and aortic afterload. Muscle fiber orientation in the LV ...

Introduction The integration of primary eigenvectors in a diffusion field yields continuous tracts, to which it is useful to assign a single helix angle. However, the optimal approach to derive the helix angle of a continuous tract in the myocardium remains unclear. Strategies used in the brain and in prior tractographic studies in the heart (Circ Cardiovasc Imaging. 2009; 2(3): 206-12) may not...

Protein-lipid interaction and bilayer regulation of membrane protein functions are largely controlled by the hydrophobic match between the transmembrane (TM) domain of membrane proteins and the surrounding lipid bilayer. To systematically characterize responses of a TM helix and lipid adaptations to a hydrophobic mismatch, we have performed a total of 5.8-mus umbrella sampling simulations and c...

UV resonance Raman spectroscopy has been used to determine the conformational energy landscape of poly-L-lysine (PLL) in the presence of NaClO4 as a function of temperature. At 1 degree C, in the presence of 0.83 M NaClO4, PLL shows an approximately 86% alpha-helix-like content, which contains alpha-helix and pi-bulge/helix conformations. The high alpha-helix-like content of PLL occurs because ...

We demonstrate a calculated alpha-helix peptide folding energy landscape which accurately simulates the first experimentally measured alpha-helix melting energy landscape. We examine a 21-amino acid, mainly polyalanine peptide and calculate the free energy along the Psi Ramachandran angle secondary folding coordinate. The experimental free energy landscape was determined using UV resonance Rama...

The relaxation of helical structures very close to equilibrium is observed via transient 2D IR spectroscopy. An initial distribution of synthetically distorted helices having an unnatural bridge linking the 10th and 12th residues of an alanine-rich α-helix is released to evolve into the equilibrium distribution of α-helix conformations. The bridge constrains the structure to be slightly displac...