title: Limited flexibility of lactose detected from residual dipolar couplings using molecular dynamics simulations and steric alignment methods.
abstract: The conformational flexibility of lactose in solution has been investigated by residual dipolar couplings (RDCs). One-bond carbon-proton and proton-proton coupling constants have been measured in two oriented media and interpreted in combination with molecular dynamics simulations (MD). Two different approaches, known as PALES (Zweckstetter et al., J. Am. Chem. Soc. 2000, 122, 3791-3792) and TRAMITE (Azurmendi et al., J. Am. Chem. Soc. 2002, 124, 2426-2427), have been used to determine the alignment tensor from a shape-induced alignment model with the oriented medium. The steric alignment of the structures from several MD trajectories has provided ensemble averaged RDCs that have been compared with the experimental ones. The obtained results reveal the almost exclusive presence of a major low energy region defined as syn-phi/syn-psi (> 97%), for which sampling occurs in a dynamic manner. This result satisfactorily agrees with that determined by standard NOE-based methods.
authors.affiliation: Unidad Asociada al CSIC de RMN de Biomoléculas Santiago de Compostela, Spain. mmartin@usc.es
authors.forename: Manuel
authors.initials: M
authors.lastname: Martín-Pastor
authors.forename: Angeles
authors.initials: A
authors.lastname: Canales
authors.forename: Francisco
authors.initials: F
authors.lastname: Corzana
authors.forename: Juan L
authors.initials: JL
authors.lastname: Asensio
authors.forename: Jesús
authors.initials: J
authors.lastname: Jiménez-Barbero
mesh_terms: D002236:Carbohydrate Conformation; D003198:Computer Simulation; D007785:Lactose / Q000737:chemistry*; D008958:Models, Molecular; D012996:Solutions; D013816:Thermodynamics
chemical_list: D012996:Solutions; D007785:Lactose