Study On The Cleavage Mediated By Ni(Ⅱ), Cu(Ⅱ) Complexes Towards Macrobiomolecules

Site specific cleavage of peptides and proteins is of great significance in biochemistry and bioengineering. For example, the selective hydrolytic cleavage of peptide bonds is the essential step in protein sequencing and proteomics.Transition metal complexes have been exploited as artificial metalloprotease for their selective cleavage of certain peptide bonds. Among those artificial metalloprotease, palladium (II) complexes have been frequently studied due to their ability to promote the hydrolysis of peptide bonds near specific amino acid residues. They could anchor to the imidazole nitrogen on the sidechain of Histidine or the sulfur atom on the sidechain of Methionine, thus promote the hydrolysis of upstream amide bond from the anchor site. However, these complexes usually work in weakly acidic media, which limits their application in neutral microenvironmen. Therefore, the development of artificial metalloprotease which works in neutral condition is attractive and challenging. The protein cleavage behavior of Ni(en) (en: 1,2-diaminoethane) was studied with myoglobin as substrates. Therefore, different methods have been utilized to determine the cleavage sites. It was found that Ni(en) is able to cleave myoglobin in neutral condition, and the higher cleavage efficiency was observed in a weak alkaline condition. Compared with the cleavage promoted by Pd(en), the cleavage promoted by Ni(en) displayed limited cleavage sites and produce less fragments. All the results indicate that Ni(en) could promote protein hydrolysis in neutral solution with high selectivity, suggesting the potential application of nickel complexes in protein engineering.Cu complexes as potential artificial metallonuclease have been widely studied in biochemistry and molecular biology. Large numbers of copper complexes with novel structures and appealing nuclease activities exhibit potential application values in DNA sequencing, footprint reagents, identification and cleavage of abnormal DNA. Improving the cleavage efficiency is one of the most important aspects in the field of artificial nucleases.In this thesis, we studied the ability of DNA binding and cleavage of a novel copper complex, in which a Glycine moiety is introduced as an auxiliary ligand to improve the water-solubility. The ability of DNA binding and cleavage of an analogue without the Glycine moiety is also studied. The results show that Glycine helps improving the water-solubility of complex, thus enhances its ability of DNA binding and cleavage.