Vibrational spectroscopy and conformational structure of protonated polyalanine peptides isolated in the gas phase.
J Phys Chem A
; 112(20): 4608-16, 2008 May 22.
Article
en En
| MEDLINE
| ID: mdl-18444632
ABSTRACT
The conformational structures of protonated polyalanine peptides, Ala(n)H(+), have been investigated in the gas phase for n = 3, 4, 5, and 7 using a combination of resonant-infrared multiphoton dissociation (R-IRMPD) spectroscopy in the NH and OH stretch regions and quantum chemical calculations. Agreement between theoretical IR and experimental R-IRMPD spectral features has enabled the assignment of specific hydrogen-bonded conformational motifs in the short protonated peptides and revealed their conformational evolution under elevated-temperature conditions, as a function of increasing chain length. The shortest peptide, Ala(3)H(+), adopts a mixture of extended and cyclic chain conformations, protonated, respectively, at a backbone carbonyl or the N-terminus. The longer peptides adopt folded, cyclic, and globular charge-solvated conformations protonated at the N-terminus, consistent with previous ion-mobility studies. The longest peptide, Ala(7)H(+), adopts a globular conformation with the N-terminus completely charge-solvated, demonstrating the emergence of "physiologically relevant" intramolecular interactions in the peptide backbone. The computed conformational relative free energies highlight the importance of entropic contributions in these peptides.
Buscar en Google
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Péptidos
/
Análisis Espectral
/
Vibración
/
Gases
Idioma:
En
Revista:
J Phys Chem A
Asunto de la revista:
QUIMICA
Año:
2008
Tipo del documento:
Article
País de afiliación:
Reino Unido