10.1021/acs.jpcb.9b05118.s002
Anup Ghosh
Anup
Ghosh
Vibrational Coupling on Stepwise Hydrogen Bond Formation
of Amide I
American Chemical Society
2019
Stepwise Hydrogen Bond Formation
hydrogen bond interaction
amide hydrogen bond interactions
H-bond donor phenol molecules
hydrogen-bonded conformer
hydrogen bond conformation
IR absorbance
hydrogen bond interactions
hydrogen bond-assisted vibrational
phenol derivatives
IR absorption spectroscopy
phenol ring transition
hydrogen bond
2019-09-09 14:49:05
Media
https://acs.figshare.com/articles/media/Vibrational_Coupling_on_Stepwise_Hydrogen_Bond_Formation_of_Amide_I/9785888
Despite the key roles
of proteins and nucleic acids in biology,
understanding their labile structures and hydrogen bond interactions
with guest molecules has posed a critical challenge to the scientific
community. In this report, I have used dimethylformamide as a model
amide to account for amide hydrogen bond interactions of protein.
To quantify hydrogen bond conformation and the structural change,
I have monitored the amide I infrared (IR) stretching frequencies
while varying the p<i>K</i><sub>a</sub> of phenol derivatives.
For all phenol derivatives, amide I has formed one hydrogen bond and
two hydrogen bond conformation. It has been observed that the formation
constant for one hydrogen bond is higher than that of two hydrogen
bonds for all phenol derivatives. During the formation of hydrogen
bond with amide I, IR absorbance of CC transition is enhanced
for all phenol derivatives. Enhancement of the IR absorbance of the
CC transition indicates hydrogen bond-assisted vibrational
coupling between the amide I and phenol ring transition. The relative
coupling constant is estimated to be higher for single hydrogen-bonded
conformer than the double hydrogen-bonded conformer. This is an intriguing
result as the frequency difference between the two coupled transitions
predicts otherwise. Using IR absorption spectroscopy, a delicate interplay
between hydrogen bonding conformations and intermolecular vibrational
coupling between amide I and H-bond donor phenol molecules has been
shown. This study can be used as a point of reference for understanding
the structural information of proteins, peptides, and nucleosides
having hydrogen bond interaction with any drug or ligand molecules.
My results as well provide an insight into the vibrational coupling
of carbonyl and CC transition of nucleobases.