Changes in the retinal transition dipole moment in bacteriorhodopsin of the purple membrane of Halobacterium Salinarium at the so-called PH(rev)

• Published in: Journal of biochemistry, molecular biology and biophysics Vol. 6; no. 1; p. 59
• Main Author: Mostafa, Hamdy I A
• Format: Journal Article
• Language: English
• Published: England 01.02.2002
• Subjects: Bacteriorhodopsins - physiology; Halobacterium salinarum - physiology; Hydrogen-Ion Concentration; Mathematics; Photochemistry; Purple Membrane - physiology; Retinaldehyde - chemistry; Spectrophotometry
• ISSN: 1025-8140

The chromophore transition dipole moment of light-adapted wild-type bacteriorhodopsin (WT-bR) in suspension is evaluated for pH range of 2.8-12. Significant variations in the transition dipole moment are observed at the so-called pH(rev). The results have reported a value of 11 and 8.5 Debye for chromophore transition dipole moment of the neutral purple and acid blue form of bacteriorhodopsin, respectively. There may be a correlation with the process of reversing the direction of the permanent electric dipole moment, due to the reversal of the surface charge asymmetry, of the purple membrane to its opposite side at that pH(rev).