Comparative study of conformational behaviour of leucine and methionine enkephalinamides by1H-nuclear magnetic resonance spectroscopy |
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Authors: | M M Dhingra Anil Saran |
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Institution: | (1) Chemical Physics Group, Tata Institute of Fundamental Research, Homi Bhabha Road, 400 005 Bombay, India |
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Abstract: | The conformational proclivity of leucine and methionine enkephalinamides in deuterated dimethyl sulphoxide has been investigated
using proton magnetic resonance at 500 MHz. The resonances from the spin system of the various amino acid residues have been
assigned from the 2-dimensional correlated spectroscopy spectra. The temperature variation of the amide proton shifts indicates
that none of the amide proton is intramolecularly hydrogen-bonded or solvent-shielded. The analysis of vicinal coupling constants,3JHN.C
2H,along with temperature coefficients and the absence of characteristic nuclear Overhauser effect cross peaks between the
NH protons reveal that there is no evidence of the chain folding in these molecules. However, the observation of nuclear Overhauser
effect cross peaks between the NH and the CαH of the preceding residue indicates preference for extended backbone conformation with preferred side chain orientations
particularly of Tyr and Phe in both Leu5]- and Met5]-enkephalinamides. |
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Keywords: | Enkephalinamides nuclear magnetic resonance structure-activity relationship endogenous peptides temperature coefficients |
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