title: A salt-bridge structure in solution revealed by 2D-IR spectroscopy.
abstract: Salt bridges are important interactions for the stability of protein conformations, but up to now it has been difficult to determine salt-bridge geometries in solution. Here we characterize the spatial structure of a salt bridge between guanidinium (Gdm(+)) and acetate (Ac(-)) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridge formation there is a significant change in the infrared response of Gdm(+) and Ac(-), and cross peaks between them appear in the 2D-IR spectrum. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes of Gdm(+) and Ac(-), as well as the coupling between them.
authors.affiliation: Van't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, Amsterdam, The Netherlands. S.Woutersen@uva.nl.
authors.forename: Adriana
authors.initials: A
authors.lastname: Huerta-Viga
authors.forename: Sérgio R
authors.initials: SR
authors.lastname: Domingos
authors.forename: Saeed
authors.initials: S
authors.lastname: Amirjalayer
authors.forename: Sander
authors.initials: S
authors.lastname: Woutersen