<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Zhang, K</style></author><author><style face="normal" font="default" size="100%">Song, Li</style></author><author><style face="normal" font="default" size="100%">Dong, J</style></author><author><style face="normal" font="default" size="100%">El-Sayed, Mostafa A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Studies of cation binding in ZnCl2-regenerated bacteriorhodopsin by x-ray absorption fine structures: effects of removing water molecules and adding Cl- ions.</style></title><secondary-title><style face="normal" font="default" size="100%">Biophysical journal</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Biophys. J.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Bacteriorhodopsins</style></keyword><keyword><style  face="normal" font="default" size="100%">Binding Sites</style></keyword><keyword><style  face="normal" font="default" size="100%">Biophysical Phenomena</style></keyword><keyword><style  face="normal" font="default" size="100%">Biophysics</style></keyword><keyword><style  face="normal" font="default" size="100%">Cations</style></keyword><keyword><style  face="normal" font="default" size="100%">Chlorides</style></keyword><keyword><style  face="normal" font="default" size="100%">Kinetics</style></keyword><keyword><style  face="normal" font="default" size="100%">Ligands</style></keyword><keyword><style  face="normal" font="default" size="100%">Spectrum Analysis</style></keyword><keyword><style  face="normal" font="default" size="100%">Water</style></keyword><keyword><style  face="normal" font="default" size="100%">X-Rays</style></keyword><keyword><style  face="normal" font="default" size="100%">Zinc</style></keyword><keyword><style  face="normal" font="default" size="100%">Zinc Compounds</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1997 Oct</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">2097-105</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The binding of Zn2+ in Zn2+-regenerated bacteriorhodopsin (bR) was studied under various conditions by x-ray absorption fine structures (XAFS). The 0.9:1 and 2:1 Zn2+:bR samples gave similar XAFS spectra, suggesting that Zn2+ might have only one strong binding site in bR. It was found that in aqueous bR solution, Zn2+ has an average of six oxygen or nitrogen ligands. Upon drying, two ligands are lost, suggesting the existence of two weakly bound water ligands near the cation-binding site in bacteriorhodopsin. When excess Cl- ions were present before drying in the Zn2+-regenerated bR samples, it was found that two of the ligands were replaced by Cl- ions in the dried film, whereas two remain unchanged. The above observations suggest that Zn2+ has three types of ligands in regenerated bR (referred to as types I, II, and III). Type I ligands are strongly bound. These ligands cannot be removed by drying or by exchanging with Cl- ions. Type II ligands cannot be removed by drying, but can be replaced by Cl- ligands. Type III ligands are weakly bound to the metal cation and are most likely water molecules that can be removed by evaporation under vacuum or by drying with anhydrous CaSO4. The results are discussed in terms of the possible structure of the strongly binding site of Zn2+ in bR.</style></abstract><issue><style face="normal" font="default" size="100%">4</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/9336205?dopt=Abstract</style></custom1><electronic-resource-num><style face="normal" font="default" size="100%">10.1016/S0006-3495(97)78240-7</style></electronic-resource-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Song, Li</style></author><author><style face="normal" font="default" size="100%">Logunov, Stephan L.</style></author><author><style face="normal" font="default" size="100%">Yang, Difei</style></author><author><style face="normal" font="default" size="100%">El-Sayed, Mostafa A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The pH dependence of the subpicosecond retinal photoisomerization process in bacteriorhodopsin: evidence for parallel photocycles.</style></title><secondary-title><style face="normal" font="default" size="100%">Biophysical journal</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Biophys. J.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Bacteriorhodopsins</style></keyword><keyword><style  face="normal" font="default" size="100%">Biophysical Phenomena</style></keyword><keyword><style  face="normal" font="default" size="100%">Biophysics</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrogen-Ion Concentration</style></keyword><keyword><style  face="normal" font="default" size="100%">Isomerism</style></keyword><keyword><style  face="normal" font="default" size="100%">Kinetics</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Structure</style></keyword><keyword><style  face="normal" font="default" size="100%">Photochemistry</style></keyword><keyword><style  face="normal" font="default" size="100%">Retinaldehyde</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1994 Nov</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">67</style></volume><pages><style face="normal" font="default" size="100%">2008-12</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The pH dependence of the subpicosecond decay of the retinal photoexcited state in bacteriorhodopsin (bR) is determined in the pH range 6.8-11.3. A rapid change in the decay rate of the retinal photoexcited state is observed in the pH range 9-10, the same pH range in which a rapid change in the M412 formation kinetics was observed. This observation supports the previously proposed heterogeneity model in which parallel photocycles contribute to the observed pH dependence of the M412 formation kinetics in bR.</style></abstract><issue><style face="normal" font="default" size="100%">5</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/7858138?dopt=Abstract</style></custom1><electronic-resource-num><style face="normal" font="default" size="100%">10.1016/S0006-3495(94)80684-8</style></electronic-resource-num></record></records></xml>