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Titration and fluorometric studies of the tyrosine side chain of angiotensin II and related peptides
Author(s) -
Juliano Luiz,
Laluce Cecilia,
Oliveira Maria C. F.,
Paiva Antonio C. M.
Publication year - 1979
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1979.360180716
Subject(s) - chemistry , side chain , titration , fluorescence , histidine , tyrosine , angiotensin ii , peptide , stereochemistry , organic chemistry , biochemistry , amino acid , polymer , receptor , quantum mechanics , physics
The effect of charged side chains on the ionization and fluorescence of the Tyr 4 phenolic group in angiotensin (Asp‐Arg‐Val‐Tyr‐Ile‐His‐Pro‐Phe) was investigated. Several synthetic peptides related to angiotensin were titrated spectrophotometrically and quantum yields of tyrosine fluorescence were also determined. The electrostatic interactions were interpreted according to the Kirkwood‐Tanford theory, and the results were related to a recently proposed model [J. L. De Coen and E. Ralston (1977) Biopolymers 16 , 1929] for angiotensin conformation in solution. The titration and fluorescence results are in good agreement with the folded conformations of this model, with the exception that the data indicate a weaker interaction between the histidine side chain and the C‐terminal carboxyl groups than that proposed in the model.