ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The purpose of this investigation was to find new and more potent charge-transfer probes for the study of certain aspects of polypeptide and protein conformation, especially of solvent-exposure of aromatic amino-acid side chains. N,N′-dimethyl-4,4′-dipyridylium ion (paraquat) was shown by NMR. to complex specifically with tryptophan, tyrosine, and phenylalanine. The long-wavelength absorption (electronic transitions) typical of charge-transfer complexes was detectable with tryptophan and tyrosine, not with phenylalanine. Paraquat forms slightly stronger complexes than N(1)-methyl-nicotinamidium ion, and appears to have different steric requirements. Im human calcitonin and human calcitonin-(11-32)-dokosipeptide all the aromatic amino-acid side-chains (Phe, Tyr) are accessible to paraquat in solution. This is true also for at least one of the two tyrosines and the tryptopha of ACTH-(1-24)-tetrakosipeptide, and for Trp (62) of chicken egg-white lysozyme. Paraquat is of special interest, because it generates a CT.-absorption band not only with tryptophan, but also with tyrosine, and because of its strong diamagnetic shielding effect.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19740570823
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