Bioassay guided fractionation of the EtOAc fraction of the sponge Callyspongia aerizusa yielded seven new cytotoxic cyclic peptides callyaerins A-F (1-6) and H (8). Their structures were determined using extensive 1D (1H, 13C and DEPT) and 2D (COSY, HMQC, HMBC, TOCSY, and ROESY) NMR and mass spectral (ESI and HRESI-TOF) data. All compounds were cyclic peptides containing ring systems of 5-9 amino acids and side chains of 2-5 amino acids in length.
View Article and Find Full Text PDFOf the aromatic 1H-NMR signals of oxidized bovine adrenodoxin only those of His56 showed intrinsic chemical shift changes upon replacement of Tyr82 by Ser or Leu, that must arise from a loss of a through-space ring-current effect of the tyrosine ring in these mutants. Thus, of the three His residues contained in adrenodoxin, His56 is closest to Tyr82, and hence to the highly acidic determinant region of adrenodoxin that is the interaction site for adrenodoxin reductase and P-450. The strong dependence of the fluorescence intensity of Tyr82 on the residue in position 56 supported this observation.
View Article and Find Full Text PDFBiomed Pept Proteins Nucleic Acids
December 1997
High quality PACAP-related peptide (PRP), a 29 amino-acid region of the PACAP precursor protein, has been synthesized in quantities sufficient for biological and structural studies. PRP has a distinct biological activity on the gallbladder that is similar to PACAP, but opposite to that of VIP and its related peptide, PHM. Its solution structure has been investigated by circular dichroism spectroscopy and 2D 1H nuclear magnetic resonance spectroscopy.
View Article and Find Full Text PDFThe solution structures of the recently discovered neuropeptides PACAP38 and PACAP27 have been investigated in aqueous solution containing varying amounts of trifluoroethanol (TFE) by circular dichroism (CD) spectroscopy and a combination of 2D 1H nuclear magnetic resonance (NMR) spectroscopy, distance geometry, and refined molecular dynamics and energy minimization calculations. In aqueous solution both peptides show only small transitory amounts of stable structure while in 50% TFE they adopt ordered structures. Qualitative NOE data and the use of the chemical shift index of the alpha-protons identified the positions of alpha-helical regions.
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