Electrospray Ionization Mass Spectrometry Peptide Molecular Interactions

Protein is very important to biological life. It is the major component of life and major life activities actor. The physiological functions of protein are determined by the proteins'structure. Protein is composed of polypeptide chains that are formed by 20 different amino acids. It is useful to learn the three-dimensional structure of protein through studying the non-covalent interaction between the peptides. This thesis consists of three phases work:The first stage of the study is that use the ESI-MS to study the non-covalent interaction between peptides. The 16 pairs 5-peptides in my study is based on the X-ray diffraction data of the protein which distance between the peptides is less than the threshold value, and we assume that two peptides interact each other. To check this hypothesis, we find the company to synthetic these peptides and study if they can form complex by mass spectrometry method.The second step based on the results of the first stage experiment. We select eight peptides and studied the interaction of the peptides, then calculated the equilibrium constant to compare the interaction strength.Based on the first and second steps, we tried to change the length of the peptide and the amino acid sequence of the peptides to study the effect of peptide length, hydrogen bond, hydrophobic interactions and sulfhydryl group to the interaction of peptides.The results support that peptides can interact each other when distant between the two peptides is less than the threshold value. Lengthened the 5-peptide to 9-peptide, the interactions between 5-peptide and 9-peptide were no significant change. It is mainly because the synergies between non-covalent interactions. Changed the sequence peptide, the non-covalent interaction had significant changes. Hydrogen bond and hydrophobic play important roles in non-covalent interaction between peptides,which strengthen the interaction. And also thiol side chain substitution had significantly effected the interactions between peptides, thiol side chain impede the non-covalent interaction.