Artificial bacteriorhodopsin pigments based on synthetic retinal analogues carrying an electron-withdrawing CF3 substituent group were prepared. The effects of CF3 on the spectra, photocycles, and Schiff base pKa values of the pigments were analyzed. A reduction of 5 units in the pKa of the Schiff base is observed when the CF3 substituent is located at the C-13 polyene position, in the vicinity...

Structural models of membrane proteins can be refined with sets of multiple orientation constraints derived from structural NMR studies of specifically labeled amino acids. The magic angle oriented sample spinning (MAOSS) NMR approach was used to determine a set of orientational constraints in bacteriorhodopsin (bR) in the purple membrane (PM). This method combines the benefits of magic angle s...

Proteins are flexible systems and commonly populate several functionally important states. To understand protein function, these states and their energies have to be identified. We introduce an algorithm that allows the determination of a gap-free list of the low energy states. This algorithm is based on the dead-end elimination (DEE) theorem and is termed X-DEE (extended DEE). X-DEE is applica...

Bacteriorhodopsin and epsilon 15 bacteriophage were used as biological test specimens to evaluate the potential structural resolution with images captured from a 4k x 4k charge-coupled device (CCD) camera in a 300-kV electron cryomicroscope. The phase residuals computed from the bacteriorhodopsin CCD images taken at 84,000x effective magnification averaged 15.7 degrees out to 5.8-A resolution r...

We present a detailed mechanism for the proton transfer from a protein-bound protonated water cluster to the bulk water directed by protein side chains in the membrane protein bacteriorhodopsin. We use a combined approach of time-resolved Fourier transform infrared spectroscopy, molecular dynamics simulations, and X-ray structure analysis to elucidate the functional role of a hydrogen bond betw...

Halobacteria are extremely specialized organisms. They live exclusively in saturated solutions of common salt. The cell membrane of these bacteria exhibit insular regions which can be isolated by membrane fractionation. These regions consist of a lipid matrix containing bateriorhodopsin molecules in a hexagonal crystalline arrangement. Bacteriorhodopsin is a deep purple retinal-protein complex ...

Ab initio complete active space SCF calculations have been carried out to investigate the first excited electronic state of a retinal protonated Schiff base analog: all-trans-3,7-dimethylnona-2,4,6,8-tetraenmethylimminium cation. This model of the retinal chromophore in bacteriorhodopsin includes five conjugated double bonds as well as both pertinent backbone methyl groups. The excited state mi...

where TR (v) is the radiation temperature introduced by Planck2 in order to describe the nonequilibrium radiaHon, and T is the working system temperature. The kinetic arrangements for free energy storage are completely ignored in (1). The simplest known photosynthetic mechanism developed by nature is based on the action of protein bacteriorhodopsin, which was isolated from purple membrane patch...

Ffulohucreriuttt hulohiuttt swims by rotating its pohtrly inserted fiagcllar bundle. The cells arc attracted by green-to-orange light which they can use for photophosphorylation but Ret damaging blue or ultraviolet light. It is petterally believed that this kind of ‘colour vision’ is achieved by the combined action of two photoreceptor proteins. sensory rhodopsins-I and -II, that switch in the ...

An introductory review of visual transduction is followed by an account of external point charge models which were proposed to explain the red—shifted maxima in visual pigments and bacteriorhodopsin. 13—Ethylretinal, 13—propylretinal, and a retinal analog with an 8—membered ring in the side—chain yield bovine rhodopsin analogs which are bleachable but spontaneously regrow. This is a phenomenon ...