Stabilization of Neutral NH2-R-COOH Form of the Antihypertensive Peptides L-Valyl-L-Prolyl-L-Proline and L-Isoleucyl-L-Prolyl-L-Proline
Spectroscopic and structural elucidation of the peptides L-Valyl-L-Prolyl-L-Proline (1) and L-Isoleucyl-L-Prolyl- L-Proline (2) are reported on the basis of experimental linear-polarized IR-spectroscopy in solid-state, 1H-NMR data and DFT. Curiously, the experimental data shown that both peptides stabilized in solution and in solid-state neutral H2N-RCOOH form. Conformational analysis made, shown two strong intramolecular NH2…O=C-N(Amide) and O=C-OH…NH2 hydrogen bonds with lengths of 2.979 Å and 2.475 Å in (1) and 2.599 Å and 2.507 Å in (2) respectively. The presence of the Pro-Pro fold resulted to strong steric effect leading to the stabilization of free COOH and NH2 groups. The Erel values of zwitterion form are significant higher than the neutral forms with a difference of 1.2 and 0.9 kJ/mol. The manner of interaction of the peptides with angiotensin-I converting enzyme is proposed.
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Document Type: Research Article
Publication date: 01 February 2009
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- Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.