posted on 2022-01-06, 18:33authored byMatthias Ruppert, Anne Creon, Henning Tidow, Nils Huse
We genetically incorporated
the unnatural amino acid p-azido-phenylalanine
(AzF) into the ubiquitous Ca2+ sensor protein calmodulin
(CaM) in complex with different peptides to explore the response of
the azido stretching line shape to varying binding motifs with femtosecond
infrared spectroscopy. The dynamic response of the azido stretching
mode varies in different CaM–peptide complexes. We model these
dynamics as coherent excitations of Fermi resonances and extract a
lifetime of the azido stretching vibration of about 1 ps. The resulting
model parameters are commensurate with the linear infrared absorption
lineshapes which suggests that the conformation-sensitive vibrational
lineshape could be composed of Fermi resonances that differ between
the protein–peptide complexes.