Amide proton temperature coefficients as hydrogen bond indicators in proteins.
J Biomol NMR
; 21(3): 249-61, 2001 Nov.
Article
em En
| MEDLINE
| ID: mdl-11775741
ABSTRACT
Correlations between amide proton temperature coefficients (deltasigmaHN/deltaT) and hydrogen bonds were investigated for a data set of 793 amides derived from 14 proteins. For amide protons showing temperature gradients more positive than -4.6 ppb/K there is a hydrogen bond predictivity value exceeding 85%. It increases to over 93% for amides within the range between -4 and -1 ppb/K. Detailed analysis shows an inverse proportionality between amide proton temperature coefficients and hydrogen bond lengths. Furthermore, for hydrogen bonds of similar bond lengths, values of temperature gradients in alpha-helices are on average I ppb/K more negative than in beta-sheets. In consequence. a number of amide protons in alpha-helices involved in hydrogen bonds shorter than 2 A show deltasigmaHN/deltaT < -4.6 ppb/K. Due to longer hydrogen bonds, 90% of amides in 3(10) helices and 98% in beta-turns have temperature coefficients more positive than -4.6ppb/K. Ring current effect also significantly influences temperature coefficients of amide protons. In seven out of eight cases non-hydrogen bonded amides strongly deshielded by neighboring aromatic rings show temperature coefficients more positive than -2 ppb/K. In general, amide proton temperature gradients do not change with pH unless they correspond to conformational changes. Three examples of pH dependent equilibrium showing hydrogen bond formation at higher pH were found. In conclusion, amide proton temperature coefficients offer an attractive and simple way to confirm existence of hydrogen bonds in NMR determined structures.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Prótons
/
Proteínas
/
Amidas
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
J Biomol NMR
Ano de publicação:
2001
Tipo de documento:
Article