A study of hydrogen-bonding of amino acids, peptides and polypeptides in the solid state as a function of temperature by static 2 HNMR method

H-2 NMR spectra of H-2-labeled amino acids, peptides, and polypeptides, as prepared in this work, were measured in the solid state over a wide range of temperatures. From spectral simulations based on the 2H dynamic NMR theory, NMR parameters such as quadrupolar coupling constant (e(2)qQ/h) and electric field gradient asymmetric parameter (eta) were determined, and the relationship between these NMR parameters and the hydrogen-bond length (R-N...(O)) was elucidated. From the observed H-2 NMR spectra of amide (NH)-H-2 deuteron of peptides and polypeptides in the solid state, it was found that the e(2)qQ/h values decrease with a decrease in R-N...(O). This shows that the hydrogen-bond length of peptides and polypeptides can be evaluated through the observation of the e(2)qQ/h value of the amide deuteron. Further, the observed H-2 NMR spectra of the (NH3)-H-2 deuterons of H-2-labeled Gly and GlyGly in the solid state, as a function of temperature, were analyzed with spectral simulations. From this result, the rotational barrier around the C-alpha-(NH3)-H-2 bond was determined. On the other hand, from the observation of H-2 NMR spectra of H-2-labeled GlyGly.HNO3 and GlyGly.H2O.HCl in the solid state, it was found that the rate of the C-3nu rotation around the C-alpha-NH3 of these compounds is several MHz above in the temperature range 215-340 K, and is higher than that observed for H-2-labeled GlyGly. (C) 2002 Elsevier Science B.V. All rights reserved.