Conformational Study of the Jet-Cooled Diketopiperazine Peptide Cyclo Tyrosyl-Prolyl.
J Phys Chem B
; 123(28): 6023-6033, 2019 07 18.
Article
en En
| MEDLINE
| ID: mdl-31268717
ABSTRACT
The conformational landscape of the diketopiperazine (DKP) dipeptide built on tyrosine and proline, namely, cyclo Tyr-Pro, is studied by combining resonance-enhanced multiphoton ionization, double resonance infrared ultraviolet (IR-UV) spectroscopy, and quantum chemical calculations. Despite the geometrical constraints due the two aliphatic rings, DKP and proline, cyclo Tyr-Pro is a flexible molecule. For both diastereoisomers, cyclo LTyr-LPro and cyclo LTyr-DPro, two structural families coexist under supersonic jet conditions. In the most stable conformation, the aromatic tyrosine substituent is folded over the DKP ring (g+ geometry of the aromatic ring) as it is in the solid state. The other structure is completely extended (g- geometry of the aromatic ring) and resembles that proposed for the vapor phase. IR-UV results are not sufficient for unambiguous assignment of the observed spectra to either folded or extended conformations and the simulation of the vibronic pattern of the S0-S1 transition is necessary. Still, the comparison between IR-UV results and anharmonic calculations allows explanation of the minor structural differences between cyclo LTyr-LPro and cyclo LTyr-DPro in terms of different NH···π and CH···π interactions.
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Modelos Moleculares
/
Dipéptidos
/
Dicetopiperazinas
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Conformación Molecular
Idioma:
En
Revista:
J Phys Chem B
Asunto de la revista:
QUIMICA
Año:
2019
Tipo del documento:
Article