Bacteriorhodopsin (BR) and halorhodopsin (HR) are light-driven outward proton and inward chloride pumps, respectively. They have similar protein architecture, being composed of seven-transmembrane helices that bind an all-trans-retinal. BR can be converted into a chloride pump by a single amino acid replacement at position 85, suggesting that BR and HR share a common transport mechanism, and the ionic specificity is determined by the amino acid at that position. However, HR cannot be converted into a proton pump by the corresponding reverse mutation. Here we mutated 6 and 10 amino acids of HR into BR-like, whereas such multiple HR mutants never pump protons. Light-induced Fourier transform infrared spectroscopy revealed that hydrogen bonds of the retinal Schiff base and water are both strong for BR and both weak for HR. Multiple HR mutants exhibit strong hydrogen bonds of the Schiff base, but the hydrogen bond of water is still weak. We concluded that the cause of nonfunctional conversion of HR is the lac...
The two enantiomers of 2-(2-hydroxybiphenyl-4-yl)propanoic acid ((S)- and (R)-BPOH) have been selected as probes for human serum albumin (HSA). Photophysical characterization in the absence of protein led to emission maxima, singlet energies, quantum yields, and fluorescence lifetime values ... more
The photodissociation of H2O in its B band is a prototype for nonadiabatic reaction dynamics. In addition to dissociation via the adiabatic pathway to the OH(Ã2Σ+) + H fragments, it also produces the OH(X̃2Π) + H fragments through two nonadiabatic pathways: the B̃ → X̃ transition via two co ... more
Due to the widespread occurrence in the environment and potential risk toward organisms of fluoroquinolones (FQs), it is of importance to develop high efficient methods for assessing their occurrence and environmental risk. A monoclonal antibody (Mab) with broad cross-reactivity to FQs was ... more
Rohm and Haas Powder Coatings is delighted to announce that its Reading, Pennsylvania, facility is the first site in the world to receive the RCMS® Site Certification awarded by the American Chemical Council (ACC).
When Raj Gupta, Chairman and CEO of Rohm and Haas Company, became Chairman ... more