1D‐ and 2D‐NMR study of a nonapeptide, a fragment of collagen, in its free state and complexed with aluminium (III)

Abstract

'H NMR studies at 250 MHz and "C NMR studies at 62.8 MHz on the synthetic nonapeptide fragment of type 111 collagen, Gly-Lys-HypGly-Glu-Hyp-Gly-PrWLys (CD), have been carried out in aqueous solution andThe resonances are assigned with the help of 2D correlated spectroscopy, pH titrations by following the characteristic pK values exhibited by protons adjacent to ionization sites and one-dimensional (1D) spin decoupling techniques. Chemical shifts of the proline and hydroxylproline carbon atoms indicate that the trans configuration about the three X-Pro and X-Hyp peptide bonds is strongly favoured in all cases, although the minor cis resonances accounting for about 10% of the Pro and Hyp intensity can also be observed. In addition, there appears to be no significant pH sensitivity of the cis * trans equilibrium. Addition of aluminium causes changes in the spectra, indicating specific interactions with carboxylates of the glutamyl and lysyl residues, as well as a change for both hydroxylproline residues. These data are interpreted by the formation of a 1 : 2 stoichiometric complex (Al"'-CD).the implication of these results with respect to the effect of aluminium in the tanning process is discussed.

Determination of microscopic acid?base parameters from NMR?pH titrations

“…Changing one of the participating amino acids to a non-bridging one by site-directed mutagenesis restores the "normal" value of the remaining group constant. For a synthetic nonapeptide fragment of collagen, group constants from 1 H NMR titration have lead to postulation of salt bridges, supported also by 13 C protonation shifts of the corresponding residues [221]. In S-methylthio-papaine, the anomalous low basicity of His 159 (logk=3.45) indicated the existence of a His-Cys ion pair [222].…”

REFINED SOLUTION STRUCTURE OF Al3+-THYMULIN COMPLEXES BASED ON RESTRAINED MOLECULAR DYNAMICS CALCULATIONS

“…Curiously, only a few reports concern the determination of the secondary and tertiary structure of these biomolecular AI 3+ -complexes in solution (17)(18)(19)(20). This is due in part to the particular chemistry of aluminum cation in aqueous solution.…”