189 research outputs found
Structure of a model salt bridge in solution investigated with 2D-IR spectroscopy
Salt bridges are known to be important for the stability of protein
conformation, but up to now it has been difficult to study their geometry in
solution. Here we characterize the spatial structure of a model salt bridge
between guanidinium (Gdm+) and acetate (Ac-) using two-dimensional vibrational
(2D-IR) spectroscopy. We find that as a result of salt bridging the infrared
response of Gdm+ and Ac- change significantly, and in the 2D-IR spectrum, salt
bridging of the molecules appears as cross peaks. From the 2D-IR spectrum we
determine the relative orientation of the transition-dipole moments of the
vibrational modes involved in the salt bridge, as well as the coupling between
them. In this manner we reconstruct the geometry of the solvated salt bridge
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