The Influence Of External Factors On The Conformation Of Pepsin By Infrared Spectroscopy

Pepsin is a very important proteolytic enzyme in the digestive system.By cutting off the connection between specific types of amino acids,the protein in food is broken down.This biological function of pepsin is built on its structure.When external factors such as temperature and pH value change,its structure will also change accordingly and affect the activity of the enzyme.Compared with NMR,circular dichroism and other methods,infrared spectroscopy has the advantages of simple sample preparation,no destruction of protein activity,accuracy and rapidity,etc.Therefore,it has become a widely used analytical test method in protein research.In this paper,the infrared spectrum is used to study the conformational changes of pepsin under various external factors,so as to provide the structural basis behind the changes in its biological function and provide theoretical support for the inference of the corresponding mechanism.Firstly,the effect of temperature on pepsin dry powder was explored.It was found that in the temperature range of 20-85?,the frequency of the amide A,amide B,amide I and II bands of pepsin shifted slightly,and the secondary structure content did not occur significantly.Two-dimensional correlation analysis shows that the order of secondary structure changes is:intermolecular?-sheet conformation>?-turn conformation>intramolecular?-sheet conformation.Then explored the influence of pH and temperature on the aqueous solution of pepsin.It was found that with the increase of pH,the content of?-sheet in the pepsin solution increased and the content of helix decreased.The amount of adsorption on the surface increased first and then decreased.The potential changes from positive to negative.On the surface of Ti O₂,the proportion of?-sheet structure in the secondary structure remains high.As the pH value increases,the ratio of other secondary structures decreases slowly,and the change trend increases slowly.At the same time,the presence of Ti O₂ is conducive to the adsorption of pepsin in solution.The frequency of the amide I and amide II bands on the surface of Ti O₂ changes more.Finally,the effect of sodium alginate concentration on the aqueous solution of pepsin was found.It was found that?-sheet and random coil structure always dominated pepsin.When the concentration of sodium alginate was 0.125 mg/ml,the content of?-sheet structure was the highest.As the concentration of sodium alginate continues to increase,the content of loose and disordered secondary structures greatly increases.At the same time,the adsorption of pepsin on Zn Se crystals increased first and then decreased.The adsorption capacity reached the maximum when the concentration of sodium alginate was 0.25 mg/ml.