Key result
1H NMR spectroscopy of [Sar1]angiotensin II and its analogues in water at neutral pH revealed a characteristic folded conformation previously observed in non-polar solvents, though to a lesser degree.
NMR studies suggest that a characteristic folded conformation for Angiotensin II, previously observed in non-polar solvents, can also be detected in water at neutral pH.
Extends Ang II analog structural data to aqueous solution; leaves open in vivo receptor relevance.
The conformation of [Sar1]angiotensin II in water at neutral pH has been examined by proton magnetic resonance spectroscopy at 400 MHz and in particular by comparing its 1H NMR spectral data with those of analogues modified at positions 1,4 and 6, namely [Sar1,Cha8]ANGII, [Des Asp1,Cha8]ANGII, [Aib1,Tyr(Me)4]ANGII, [Aib1,Tyr(Me)4,Ile8]ANGII, [N-MeAib1,Tyr(Me)4]ANGII, [N-MeAib1,Tyr(Me)4,Ile8]ANGII, ANGIII and [Sar1,Ile8]ANGII. Assignment of all proton resonances in these analogues was made possible by 2D COSY NMR experiments. The H-2 and H-4 protons for the histidine ring in [Sar1]ANGII, ANGII and ANGIII were shielded compared with the same protons in [Sar1,Ile8]ANGII, [Sar1,Cha8]ANGII and [Des Asp1,Cha8]ANGII; this shielding effect was not disturbed upon methylation of the tyrosine hydroxyl and/or replacement of residue 1 (sarcosine or aspartic acid) with aminoisobutyric acid (Aib) or N-methyl aminoisobutyric acid (N-MeAib). These data are consistent with our previous suggestion based on NMR studies in neutral DMSO that a characteristic folded conformation for ANGII previously observed in non-polar solvents can also be detected in water at neutral pH, but to a lesser degree.
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Hondrelis et al. (1994) studied this question. Angiotensin II analogues was evaluated on Conformation in water at neutral pH. 1H NMR spectroscopy of [Sar1]angiotensin II and its analogues in water at neutral pH revealed a characteristic folded conformation previously observed in non-polar solvents, though to a lesser degree.
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