@article {866, title = {Detection of a Yb3+ binding site in regenerated bacteriorhodopsin that is coordinated with the protein and phospholipid head groups.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {93}, year = {1996}, month = {1996 Dec 10}, pages = {14333-7}, abstract = {Near infrared Yb3+ vibronic sideband spectroscopy was used to characterize specific lanthanide binding sites in bacteriorhodopsin (bR) and retinal free bacteriorhodopsin (bO). The VSB spectra for deionized bO regenerated with a ratio of 1:1 and 2:1 ion to bO are identical. Application of a two-dimensional anti-correlation technique suggests that only a single Yb3+ site is observed. The Yb3+ binding site in bO is observed to consist of PO2- groups and carboxylic acid groups, both of which are bound in a bidentate manner. An additional contribution most likely arising from a phenolic group is also observed. This implies that the ligands for the observed single binding site are the lipid head groups and amino acid residues. The vibronic sidebands of Yb3+ in deionized bR regenerated at a ratio of 2:1 ion to bR are essentially identical to those in bO. The other high-affinity binding site is thus either not evident or its fluorescence is quenched. A discussion is given on the difference in binding of Ca2+ (or Mg2+) and lanthanides in phospholipid membrane proteins.}, keywords = {Bacteriorhodopsins, Binding Sites, Metals, Rare Earth, Phospholipids, Retinaldehyde, Spectroscopy, Near-Infrared}, issn = {0027-8424}, author = {Roselli, Cecile and Boussac, A and Mattioli, T A and Griffiths, Jennifer A. and El-Sayed, Mostafa A} }