Circular dichroism of corticotropin, fragment 1–24, and model compounds. An assessment of the contributions of the peptide chromophore and aromatic residues
作者:
Leslie A. Holladay,
David Puett,
期刊:
Biopolymers
(WILEY Available online 1976)
卷期:
Volume 15,
issue 1
页码: 43-59
ISSN:0006-3525
年代: 1976
DOI:10.1002/bip.1976.360150106
出版商: Wiley Subscription Services, Inc., A Wiley Company
数据来源: WILEY
摘要:
AbstractThe far‐ultraviolet circular dichroic spectrum of the 39‐residue peptide hormone porcine corticotropin and the biologically active fragment corticotropin 1–24 is negative from 250 nm to 195 nm in water, but in 6Mguanidinium chloride a positive band appears at about 225 nm. The temperature and guanidinium chloride dependence of this spectral transition indicates the absence of any stable ordered secondary structure in corticotropin and the spectrum is seen to be in only partial agreement with results using the model peptide chromophore, Ala‐Ala‐Ala. Using oligopeptides containing aromatic amino acid residues sandwiched between glycyl residues, it is shown that the shape and intensity of the corticotropin 225 nm positive band which appears in 6Mguanidinium chloride is in agreement with the far‐ultraviolet transitions of the aromatic chromophores in the hormone. Curve resolution of the near‐ultraviolet circular dichroic spectrum of corticotropin and comparison of the rotational strengths of the phenylalanyl and tyrosyl bands reveals no evidence for increased rotational freedom in 6Mguanidinium hydrochloride. Spectral changes are observed, however, in the transitions arising from the single tryptophan. This study suggests that corticotropin in aqueous solution may serve as a better model for the circular dichroic spectrum of the aperiodic regions in globular proteins than either synthetic homopolypeptides or reference proteins for which spectral and X‐ray diffraction dat
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