A Spectroscopic Study of Rhodopsin Alpha-Helix Orientation

Polarized Fourier transform infrared spectroscopy and far ultraviolet circular dichroism of oriented multilamellar films of photoreceptor membranes indicate rhodopsin alpha-helices are predominantly oriented perpendicular to the bilayer plane

Fourier transform infrared evidence for a predominantly alpha-helical structure of the membrane bound channel forming COOH-terminal peptide of colicin E1

The structure of the membrane bound state of the 178-residue thermolytic COOH-terminal channel forming peptide of colicin E1 was studied by polarized Fourier transform infrared (FTIR) spectroscopy. This fragment was reconstituted into DMPC liposomes at varying peptide/lipid ratios ranging from 1/25–1/500. The amide I band frequency of the protein indicated a dominant alpha-helical secondary structure with limited beta- and random structures. The amide I and II frequencies are at 1,656 and 1,546 cm-1, close to the frequency of the amide I and II bands of rhodopsin, bacteriorhodopsin and other alpha-helical proteins. Polarized FTIR of oriented membranes revealed that the alpha-helices have an average orientation less than the magic angle, 54.6 degrees, relative to the membrane normal. Almost all of the peptide groups in the membrane-bound channel protein undergo rapid hydrogen/deuterium (H/D) exchange. These results are contrasted to the alpha-helical membrane proteins, bacteriorhodopsin, and rhodopsin

Tyrosine protonation changes in bacteriorhodopsin: a Fourier transform infrared study of BR548 and its primary photoproduct

Bio-organic Synthesi

Lognormal Properties of SGR 1806-20 and Implications for Other SGR Sources

The time interval between successive bursts from SGR 1806-20 and the intensity of these bursts are both consistent with lognormal distributions. Monte Carlo simulations of lognormal burst models with a range of distribution parameters have been investigated. The main conclusions are that while most sources like SGR 1806-20 should be detected in a time interval of 25 years, sources with means about 100 times longer have a probability of about 5\% of being detected in the same interval. A new breed of experiments that operate for long periods are required to search for sources with mean recurrence intervals much longer than SGR 1806-20.Comment: 4 pages, latex with seperate file containing 2 uuencoded, gzip'ed, tarred, .eps figures. Replaced with file that does not use kluwer.sty to allow automatic postscript generation. To appear in proceedings of ESLAB 2

Optical switching between long-lived states of opsin transmembrane voltage sensors

Opsin-based transmembrane voltage sensors (OTVSs) are membrane proteins increasingly used in optogenetic applications to measure voltage changes across cellular membranes. In order to better understand the photophysical properties of OTVSs, we used a combination of UV-Vis absorption, fluorescence and FT-Raman spectroscopy to characterize QuasAr2 and NovArch, two closely related mutants derived from the proton pump archaerhodopsin-3 (AR3). We find both QuasAr2 and NovArch can be optically cycled repeatedly between O-like and M-like states using 5-min exposure to red (660 nm) and near-UV (405 nm) light. Longer red-light exposure resulted in the formation of a long-lived photoproduct similar to pink membrane, previously found to be a photoproduct of the BR O intermediate with a 9-cis retinylidene chromophore configuration. However, unlike QuasAr2 whose O-like state is stable in the dark, NovArch exhibits an O-like state which slowly partially decays in the dark to a stable M-like form with a deprotonated Schiff base and a 13-cis,15-anti retinylidene chromophore configuration. These results reveal a previously unknown complexity in the photochemistry of OTVSs including the ability to optically switch between different long-lived states. The possible molecular basis of these newly discovered properties along with potential optogenetic and biotechnological applications are discussed.Solid state NMR/Biophysical Organic Chemistr

Expression and Spectroscopic Characterization of Melanopsin and Squid Rhodopsin

FWN – Publicaties zonder aanstelling Universiteit Leide

Redshifted and Near-infrared Active Analog Pigments Based upon Archaerhodopsin-3

Contains fulltext : 206251.pdf (publisher's version ) (Open Access

Effect of caboxyl mutations on functional properties of bovine rhodopsin

Contains fulltext : 21888___.PDF (publisher's version ) (Open Access