Proteorhodopsin (pR) is a bacteriorhodopsin (bR) homologue, recently discovered in oceanic bacterioplankton, which functions as a light-driven proton pump. Resonance Raman spectra of pR excited with 532-nm light indicate that there are two subpopulations of pR within the sample solubilized in octylglucoside detergent and maintained in a light-adapted state in a spinning Raman cell. The subpopulations exhibit two distinct chromophore environments, as evidenced by two sets of split peaks, 1642/1655 cm -1 (corresponding to the Schiff base υ CdN vibration) and 1244/1252 cm -1 (corresponding to a retinylidene-lysine N-C-H rock). These populations most likely arise either from different post-translational modifications of the heterologously expressed protein or from a mixture of retinal isomers (all-trans and 13-cis) that was previously reported to be present in light-adapted pR in a 60:40 ratio. However, the latter possibility seems at odds with the resonance Raman fingerprint spectral patterns in both natural-abundance and 15-2 H-retinal-subsituted pR, which are consistent with an all-trans chromophore configuration similar to that of light-adapted bR.

The absolute configuration assignments of three antifungal agents, (+)-(2R,4S)-ketoconazole, (+)-(2R,4S)-itraconazole (with (S)-configuration at the sec-butyl group) and (+)-(S)-miconazole nitrate have been confirmed by using vibrational circular dichroism (VCD). For these three antifungal drugs, this study also provides evidence for the most abundant conformations of miconazole and for the relative conformations of the azole, dichlorophenyl, and methoxyphenyl groups in ketoconazole and itraconazole, in chloroform solution.

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