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R Korenstein

Publications and source records attributed to R Korenstein.

44 records · Page 3Linked to original sources
PubMed1977

Electric field effects in bacteriorhodopsin.

Exposure of aqueous suspensions of fragments of the purple membrane of Halobacterium halobium to electric field pulses leads to transient linear dichroism phenomena. The effects are interpreted in terms of field-induced alignments of the bacteriorhodopsin chromophore. Two observed relaxation times (tau) are attributed to rotation of the whole membrane fragments (tau s approximately 100 ms), and to a much faster reorientation of the chromophore within membrane (tau f approximately 260 microns).

Bacteriorhodopsins↗
PubMed1976

Kinetic isotope effects in the photochemical cycle of bacteriorhodopsin.

Kinetics were determined for the four transients K590, L540, M410, O660 of the photochemical cycle of bacteriorhodopsin (BR570) both in 1H2O and in 2H2O over a wide temperature range. Breaks in the Arrhenius plots, observed at 25 degrees-32 degrees for the longest-lived transients coincide with a transition point in the microviscosity of the membrane as measured by depolarization of an added fluorescent probe. The earliest isotope effect occurs in the decay of L540, and is present in the subsequent formation and decay of M410 and O660. Thus in the light-driven proton pump of BR570, proton ejection from the Schiff base correlates with decay of L540 and reprotonation occurs with the decay of both M410 and O660 back to BR570.

Bacteriorhodopsins↗
PubMed1976

Energetics and chronology of phototransients in the light response of the purple membrane of Halobacterium halobium.

Arrhenius parameters for formation and decay of phototransients in suspensions of purple membrane fragments in H2O and 2H2O have been determined in the temperature range 0-60 degree C. Kinetic isotope effects are found which show that proton transfer steps are involved in both formation and decay of the two longest-lived transients absorbing at 410 nm and 660 nm, respectively. The results also suggest that these transients do not occupy a single pathway in the spontaneous deexcitation of bacteriorhodopsin within the purple membrane. Purple membrane undergoes a phase transition at 25-30 degrees C in both H2O and 2H2O.

Bacteriorhodopsins↗
PubMed1976

On the primary quantum yields in the bacteriorhodopsin photocycle.

Pulsed Nd laser experiments in suspensions of the purple membrane of Halobacterium halobium are carried out at room temperature. At sufficiently high laser intensities, a photostationary mixture of bacteriorhodopsin (BR) and its red-shifted (batho) photoproduct (K) is obtained. The spectra of the first three intermediates in the photocycle are reported. The data yield a value of phi1/phi2=0.40 +/- 0.05 for the ratio of the quantum yields of the forward (phi1) and reverse (phi2) processes, setting an upper limit of approximately 0.4 for the quantum efficiency of the cycle at room temperature. This method is generally available for the determination of phi2 in the case of a photoequilibrium: A in equilibrium B, where B is a short-lived transient and phi1 is known from low intensity measurements. Its potential application is of importance for the study of the photophysics of visual pigments at physiological temperatures.

Bacteriorhodopsins↗