Anharmonic Vibrational Spectra Of Polypeptides And Design Of Infrafed Associated Devices

The infrared spectra for the amide units of protein backbone were known to be structural sensitive,and have long been used as an important tool for of the determination of protein 3D structure.Recently developed femtosecond two-dimensional infrared(2D IR)spectroscopy is capable of revealing the dynamical structure of protein with ultrafast time resolution.The improvements of infrared technology is helpful for our understanding of protein structure,and the molecular simulations can decipher the structural information out of the vibrational spectra of the backbone amide units of protein.The three-dimensional structure of protein is vital for its physiological functions.The investigation of protein's secondary structure preference on the surface of carbon nano materials would be conducive for drug design and for preventing protein misfolding.The results are important for our understandings about the diseases caused by conformational changes of protein,such as Alzheimer's disease.In this paper,we designed a solid sample grinder and liquid sample cells for the improvements of efficiency and accuracy of infrared spectrum detection.At the same time,we performed quantum chemical calculations and MD simulations for glycine dipeptide,alanine dipeptide and A?(37-42)in D2O solution.The dynamical structure and the anharmonic vibrational spectra were calculated,the anhamonic parameters of amide-I modes were obtained for the simulation of 2D IR dot spectra.Results show that of the amide-? vibrations are delocalized,and their anharnonic vibrational characters vary with the number of residues,and the coupling between vibrational modes can not be ignored for polypeptides.Molecular dynamics simulations were carried out to investigate the secondary structure changes of Ab?(25-35)on the surface of graphene or graphene oxide.It showed that AP(25-35)was quickly adsorbed onto graphene or graphene oxide,and the helix conformer of A?(25-35)became less populated due to the existence of oxygen group of graphene oxide.It is hard to get close to graphene oxide for A?(25-35)and the relaxing of helix conformation was slower.The-C=C-group was introduced into the sidechain of alanine dipetide as a structural probe.All atom molecular dynamics simulations were performed for dipeptide in water.The electrostatic frequency map of-C?C-stretching motion was constructed to achieve the fast prediction of its vibrational spectrum,and therefore build the correlation between the vibrational spectrum of-C?C-stretching motion and the secondary structure of polypeptide.The vibration frequency of-C=C-stretching motion obtained by this method is close to the experimental results,which is helpful to establish the correlation between the-C?C-infrared spectrum and the secondary structure of polypeptide.The result provided a basis for the research on polypeptide conformation at specific sites.