Spectroscopic Study On Interaction Of Fullerene-ethylenediamine Derivatives With Biomacromolecule And The Mass Spectrometric Research Of High Fullerene C₉₆

Two water-soluble fullerene ethylenediamine?EDA?derivatives C₆₀-?EDA?₃ and Gd@C₈₂-?EDA?₈ were synthesized according to literature methods,their interaction mechanisms with bovine serum albumin?BSA?and human serum albumin?HSA?were studied by UV-Vis absorption spectra and fluorescence spectroscopy.It is found that the maximal absorption peak of serum albumin at 280 nm is blue shifted by 1² nm after interaction with fullerene ethylenediamine derivatives,probably due to the change of amino acid residue microenvironment by fullerene ethylenediamine derivatives.It shows that the drug may interact with BSA and HSA.Fluorescence spectrum analysis shows that both C₆₀-?EDA?₃ and Gd@C₈₂-?EDA?₈ have significant fluorescence quenching effect on BSA and HSA,and the quenching effect is stronger with increasing concentration.The results show that the fluorescence quenching mechanism is static quenching,and the static quenching constants are all greater than 10⁴ L/mol.The calculated binding constants are all greater than 10⁵ L/mol,and the number of binding sites is approximately 1.The results of three-dimensional fluorescence spectroscopy show that when C₆₀-?EDA?₃ and Gd@C₈₂-?EDA?₈ are combined with serum albumin,the microenvironment resulting in optically active amino acid residues such as tryptophan,tyrosine and phenylalanine in BSA and HSA has changed.This article also simulates the human physiological environment,and the interaction of C₆₀-?EDA?₃ and Gd@C₈₂-?EDA?₈ with EB-DNA system was probed with ethidium bromide?EB?as fluorescent probe in pH=7.4 Tris-HCl buffer.UV-Vis absorption and fluorescence spectroscopy studies showed that the binding of C₆₀-?EDA?₃ and Gd@C₈₂-?EDA?₈ to EB-DNA system is intercalation,which can destroy the secondary structure of DNA and change the double helix structure of DNA,and Gd@C₈₂-?EDA?₈ has more severe structural damage to EB-DNA.Both C₆₀-?EDA?₃ and Gd@C₈₂-?EDA?₈ quench the fluorescence of EB-DNA system,it is a static quenching mechanism,using the Stern-Volmer equation to analyze the experimental data,the quenching constant of DNA for C₆₀-?EDA?₃ is 0.659×10⁴ L·mol^-1,and the binding constant is 1.401×10³ L·mol^-1,the number of binding sites was 1.517;the quenching constant of DNA for Gd@C₈₂-?EDA?₈ was 11.551×10⁴ L·mol^-1,the binding constant was 22.653×10³ L·mol^-1,and the number of binding sites was0.766.MALD-MS,LDI-MS and CID-MS/MS methods were successively adopted to study ionization feature,molecular ion fragmentation and encasing addition of the higher fullerene D_3d?3?-C₉₆,which was synthesized,isolated and structure confirmed in recent years.The results show that MALDI and LDI are soft and hard ionization style for the higher fullerene D_3d?3?-C₉₆,respectively,and,with the laser intensity increasing,some special fragments present“magic number”effects.In CID-MS/MS experiments,,not only series of C₂ loss from D_3d?3?-C₉₆⁺ion but also the encasing addition of He atom into the collided carbon cage were observed,and then split into the relative fragment ions.