The immobilization of biological molecules onto polymeric membranes to produce biofunctional membranes is used for selective catalysis, separation, analysis, and artificial organs. Normally, random immobilization of enzymes onto polymeric membranes leads to dramatic reduction in activity due to chemical reactions involved in enzyme immobilization, multiple-point binding, etc., and the extent of...

Profiles of polarity across biological membranes are essential determinants of the cellular permeability barrier and of the stability of transmembrane proteins. High-field electron paramagnetic resonance of systematically spin-labeled lipid chains is used here to determine the polarity profiles of cholesterol-containing phospholipid membranes. The polarity dependence of the g(xx)-tensor element...

A single-cysteine mutant of the lactose transport protein LacS(C320A/W399C) from Streptococcus thermophilus was selectively labeled with a nitroxide spin label, and its mobility in lipid membranes was studied as a function of its concentration in the membrane by saturation-transfer electron spin resonance. Bovine rhodopsin was also selectively spin-labeled and studied to aid the interpretation ...

A single-cysteine mutant of the lactose transport protein LacS(C320A/W399C) from Streptococcus thermophilus was selectively labeled with a nitroxide spin label, and its mobility in lipid membranes was studied as a function of its concentration in the membrane by saturation-transfer electron spin resonance. Bovine rhodopsin was also selectively spin-labeled and studied to aid the interpretation ...

A new spin-labeled derivative of ADP, 2-(4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl)thioadenosine-5'-diphosphate, has been synthesized. The compound causes both the reversible and irreversible phases of aggregation of human blood platelets at concentrations similar to those required for similar phases of aggregation by ADP itself. The spin-labeled ADP also rivals ADP as a substrate for py...

We have developed a computational molecular dynamics technique to simulate the motions of spin labels bound to the regulatory domain of scallop myosin. These calculations were then directly compared with site-directed spin labeling experimental results obtained by preparing seven single-cysteine mutants of the smooth muscle (chicken gizzard) myosin regulatory light chain and performing electron...

Continuous-wave (CW) EPR measurements of enhancements in spin-lattice (T(1)-) relaxation rate find wide application for determining spin-label locations in biological systems. Often, especially in membranes, the spin-label rotational motion is anisotropic and subject to an orientational potential. We investigate here the effects of anisotropic diffusion and ordering on non-linear CW-EPR methods...

Channelrhodopsin is a cation channel with the unique property of being activated by light. To address structural changes of the open state of the channel, two variants, which contain either 1 or 2 wild-type cysteines, were derivatised with nitroxide spin label and subjected to electron paramagnetic resonance spectroscopy. Both variants contained the C128T mutation to trap the long-lived P3(520)...

Nuclear-resonance spectra of phosphatidylcholine (PC) vesicles are broadened by spin-labeled PC. The broadening of the N-methyl proton line is proportional to spin-labeled PC concentration; the broadening by 1 molecule in 100 of spin-labeled PC is 9.7 Hz at 35 degrees C; the broadening is not due to collisions between vesicles, exchange of spin label between vesicles, or fusion of vesicles. The...