Two-dimensional IR Spectroscopy Study Of Biological Model Systems And The Optimization Of Site-specific Infrared Probe

Time-resolved two-dimensional infrared spectroscopy measures vibration-related correlations and couplings and is a powerful tool for studying vibration coupling,chem-ical exchange and spectral diffusion processes.Although this technology has shown its advantages in reflecting the dynamics processes and couplings,it has not been widely applied to biology due to the difficulties in constructing and operating the system.An-other factor limiting its application is the drawbacks and deficiencies in existing specific infrared probes.The complex absorption profiles of 4-azido-L-phenyalanine(pN3Phe)hindered its application in multi-dimensional spectroscopy.The development and im-provement of non-natural amino acid infrared probes,which can be used for the site-specific detection of protein structure and dynamics,is of great significance to under-stand the working mechanism of proteinsThis dissertation introduces a home-built two-dimensional infrared spectroscopy system based on pulse shaping and up-conversion method.Through the modulation of frequency and phase by acousto-optic modulator,noise is reduced by phase cycle,sampling interval is reduced by frequency shift,and chirp is corrected.Based on the principle of up-conversion,mid-infrared laser is converted into visible and collected by a complementary metal oxide semiconductor array detector.The two-dimensional infrared spectroscopy system based on the above technology has great advantages in practical application because of its low cost,phase locking,high signal-to-noise ratio and fast acquisition speed.Using this system,we do some researches as follows(1)Based on azide ions,the hydrogen bond dynamics of confined water system under the influence of different interface charges is detected.The confinement effect cause the water dynamics to slow down.We conclude that the charged interface affects the water distribution near the interface layer,affecting the vibration energy transfer and the hydrogen bond network arrangement,inducing a more obvious heterogeneous distribution of the hydrogen bond network inside the confined water(2)Using W(CO)a as IR probe,we study the interaction between SiO2 nanopar-ticles and planar phospholipid multibilayer model cell membranes.It was found that the vibrational relaxzation of W(CO)6 in membranes is slower with the increase of nanoparticle size in our research window(?20nm).Spectral diffusion process is rela-tively insensitive to the size of nanoparticles.High concentration of nanoparticles leads to relatively obvious global fluctuation of the membrane,which is characterized by a slower spectral diffusion dynamics.Under low concentration,the SiO2 nanoparticles affect the function of model cell membranes mainly by destroying the local structure and dynamics.(3)The origin of the accidental Fermi resonance of the 4-azido-L-phenylalanine IR probe is systematically studied by the two-dimensional infrared spectroscopy,first principles calculations,and a three-state perturbation model analysis.Based on the obtained information,a new method for suppressing Fermi resonance by changing the substitution site of azide is proposed.We identify changing the substitution position of the azide group from para to meta is effective in modulating the Fermi resonances by the first principles calculations and spectroscopy experiments.