posted on 2024-03-15, 05:30authored byJunjun Tan, Mengmeng Wang, Zijian Ni, Ruoqi Pei, Fangwen Shi, Shuji Ye
The coupling between different vibrational
modes in proteins is
essential for chemical dynamics and biological functions and is linked
to the propagation of conformational changes and pathways of allosteric
communication. However, little is known about the influence of intermolecular
protein–H2O coupling on the vibrational coupling
between amide A (NH) and amide I (CO) bands. Here, we investigate
the NH/CO coupling strength in various peptides with different secondary
structures at the lipid cell membrane/H2O interface using
femtosecond time-resolved sum frequency generation vibrational spectroscopy
(SFG-VS) in which a femtosecond infrared pump is used to excite the
amide A band, and SFG-VS is used to probe transient spectral evolution
in the amide A and amide I bands. Our results reveal that the NH/CO
coupling strength strongly depends on the bandwidth of the amide I
mode and the coupling of proteins with water molecules. A large extent
of protein–water coupling significantly reduces the delocalization
of the amide I mode along the peptide chain and impedes the NH/CO
coupling strength. A large NH/CO coupling strength is found to show
a strong correlation with the high energy transfer rate found in the
light-harvesting proteins of green sulfur bacteria, which may understand
the mechanism of energy transfer through a molecular system and assist
in controlling vibrational energy transfer by engineering the molecular
structures to achieve high energy transfer efficiency.