Eugene I. Rabinowitch: A prophet of photosynthesis and of peace in the world.

More than 45 years have passed since Eugene I. Rabinowitch died, on May 15, 1973, at the age of 75, but many still remember him as a photosynthesis giant, the author of a 2000-page "Bible" on photosynthesis, a great chemist and physicist, a discoverer of several basic photoreactions, one of the founders of modern biophysics, a peacemaker, a poet, an architect, an artist, a wonderful human being, and above all a great mentor. Sir John Rotblatt cited Eugene Rabinowitch, together with Bertrand Russell, for their key contributions that led to the Nobel Peace Prize awarded in 1995 jointly to Rotblatt and the Pugwash Conferences on Science and World Affairs "for their efforts to diminish the part played by nuclear arms in international politics and, in the longer run, to eliminate such arms.

Evidence for Reduced Fatigue Resistance of Contemporary Rotary Instruments Exposed to Body Temperature.

Introduction: The purpose of this study was to evaluate the effect of 2 different temperatures (20°C and 37°C) on the cyclic fatigue life of rotary instruments and correlate the results with martensitic transformation temperatures.

Methods: Contemporary nickel-titanium rotary instruments (n = 20 each and tip size #25, including Hyflex CM [Coltene, Cuyahoga Falls, OH], TRUShape [Dentsply Tulsa Dental Specialties, Tulsa, OK], Vortex Blue [Dentsply Tulsa Dental Specialties], and ProTaper Universal [Dentsply Tulsa Dental Specialties]) were tested for cyclic fatigue at room temperature (20°C ± 1°C) and at body temperature (37°C ± 1°C). Instruments were rotated until fracture occurred in a simulated canal with an angle curvature of about 60° and a radius curvature of 3 mm; the center of the curvature was 4.

Kinetics and pH dependence of light-induced deprotonation of the Schiff base of rhodopsin: possible coupling to proton uptake and formation of the active form of Meta II.

In this paper we first review what is known about the kinetics of Meta II formation, the role and stoichiometry of protons in Meta II formation, the kinetics of the light-induced changes of proton concentration, and the site of proton uptake. We then go on to compare the processes that lead to the deprotonation of the Schiff base in bacteriorhodopsin with rhodopsin. We point out that the similarity of the signs of the light-induced electrical signals from the two kinds of oriented pigment molecules could be explained by bacteriorhodopsin releasing a proton from its extracellular side while rhodopsin taking up a proton on its cytoplasmic side.

Studies on pyrylretinal analogues of bacteriorhodopsin.

The retinal analogues 3-methyl-5-(1-pyryl)-2E,4E-pentadienal (1) and 3,7-dimethyl-9-(1-pyryl)-2E,4E,6E,8E-nonatetr aenal (2), which contain the tetra aromatic pyryl system, have been synthesized and characterized in order to examine the effect of the extended ring system on the binding capabilities and the function of bacteriorhodopsin (bR). The two bR mutants, E194Q and E204Q, known to have distinct proton-pumping patterns, were also examined so that the effect of the bulky ring system on the proton-pumping mechanism could be studied. Both retinals formed pigments with all three bacterioopsins, and these pigments were found to have absorption maxima in the range 498-516 nm.

The proton release group of bacteriorhodopsin controls the rate of the final step of its photocycle at low pH.

The factors determining the pH dependence of the formation and decay of the O photointermediate of the bacteriorhodopsin (bR) photocycle were investigated in the wild-type (WT) pigment and in the mutants of Glu-194 and Glu-204, key residues of the proton release group (PRG) in bR. We have found that in the WT the rate constant of O --> bR transition decreases 30-fold upon decreasing the pH from 6 to 3 with a pKa of about 4.3.