A model molecule of the hydrogen-bonded chain in the active site of bacteriorhodopsin.
We synthesized a 2-N-methylaminoethyl-tetramethylquanidine amide of Kemp's triacid (CP2). Furthermore, we added to CP2 tetrabutylammonium 4-tert-butylphenolate. The pKa value of 4-tert-butylphenol is comparable to that of tyrosine. We studied by FT-IR spectroscopy CP2 and the complex of CP2 with 4-tert-butylphenolate. This complex is a model for the hydrogen-bonded chain in the active centre of the bacteriorhodopsin molecule. An intense continuum in the FT-IR spectra demonstrates that this hydrogen-bonded chain shows large proton polarizability due to collective proton motion. As earlier demonstrated also Schiff base carboxylic acid bonds show large proton polarizability. Thus, in all these hydrogen bonds protons can easily be shifted by collective proton motion due to changes of the local electrical fields and by changes of specific interactions arising from conformational changes.
Brzezinski
B
B
Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland.
Urjasz
H
H
Zundel
G
G
D000595:Amino Acid Sequence; D001120:Arginine; D001224:Aspartic Acid; D001436:Bacteriorhodopsins / Q000737:chemistry*; D001665:Binding Sites; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D008958:Models, Molecular; D010636:Phenols; D011487:Protein Conformation; D012545:Schiff Bases; D017550:Spectroscopy, Fourier Transform Infrared; D014443:Tyrosine
D007202:Indicators and Reagents; D010636:Phenols; D012545:Schiff Bases; D001224:Aspartic Acid; D014443:Tyrosine; D001436:Bacteriorhodopsins; D001120:Arginine; C006862:butylphen