ACTIVE-SITE OF BACTERIORHODOPSIN - FTIR AND H-1-NMR STUDIES USING A MODEL MOLECULE

被引:9
作者
BRZEZINSKI, B
OLEJNIK, J
ZUNDEL, G
机构
[1] UNIV MUNICH,INST PHYS CHEM,THERESIENSTR 41,D-80333 MUNICH,GERMANY
[2] ADAM MICKIEWICZ UNIV POZNAN,FAC CHEM,PL-60780 POZNAN,POLAND
来源
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS | 1994年 / 90卷 / 08期
关键词
D O I
10.1039/ft9949001095
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We obtained the 2-N-methylaminoethylguanidine amide, 4, of Kemp's triacid(all-cis-1,3,5-trimethylcyclohexane 1,3,5-tricarboxylic acid) as a model substance for the active site of bacteriorhodopsin. Compound 4 was synthesised from Kemp's triacid triethyl ester, 1, in three reactions. Compound 4 and its complex with tetrabutylammonium 4-methylphenolate were studied by FTIR and H-1 NMR spectroscopy in acetonitrile solutions. In the case of compound 4, two types of hydrogen bond are formed: one is the CO2H ... N half arrow left over half arrow right CO2- ... H+N bond. In this case, the donor is one of the two carboxylic acid groups, and the acceptor, the guanidine group. A double-minimum proton potential is present in this bond and therefore it exhibits large proton polarizability. The second NH ... O=C hydrogen bond formed between the protonated guanidine (proton donor group) and the carbonyl O atom of the other carboxylic group is asymmetrical. The proton is localised at the guanidine residue. If a phenolate molecule is added to the solution of compound 4, the situation changes dramatically. A PhOH ... N half arrow left over half arrow left PhO- ... H+N bond with large proton polarizability is formed between the phenolate and guanidine groups. The polarizable carboxylic acid-guanidine hydrogen bond is broken and the asymmetrical NH ... O bond between guanidine and the O atoms of carboxylic acid becomes much stronger. The results obtained with the model are compared with those obtained earlier with bacteriorhodopsin.
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收藏
页码:1095 / 1098
页数:4
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