Study On Structure-Activity Relationships Of Antioxidant Peptide Through Enzymatic By Quantum Chemistry

The structure and function of protein and peptide research is the most widely and active areas in functional food research at home and abroad in recent years. In numerous functions active peptides, antioxidant peptides have great feature like widely source, easy absorption and combines a variety of physiological functions(such as hypotensive, improve immunity, etc.).Enzymatic with advantages like mild condition, high security, low price and specific functions active peptide can be obtained become the mainstream of antioxidant activity peptide preparation method,Thus, antioxidant peptides by enzymic preparation has become the hot spots about functional food, additives, and drug.This paper based on 2～7 amino acid residues antioxidant oligopeptide by enzymatic production as the research object, the structure and the energy parameters of highly active oligopeptide calculate by quantum chemistry,to extrapolate the activity sites of oligopeptide; According to the value of antioxidant activity of the peptides and quantum chemical calculation results, explore the relationship between structure and activity of antioxidant peptides, clarify its antioxidant mechanism, establish the relational model between structure and function of antioxidant oligopeptide, provide a theoretical basis for developing, changing, synthesizing antioxidant peptides about functional food, additives, and drug.From the o-phenanthroline chemiluminescence reaction mechanism, by single factor experiment and orthogonal analysis,we have worked out a new set of stable o-phenanthroline chemiluminescence system, to detect the activity of antioxidant oligopeptides scavenging·OH:25% of H2O2,1.50 mmol/L of o-phenanthroline,1.25 mmol/L of CuSO4,pH 7.50 borax-borate buffer,0.25 mmol/L of ascorbic acid. And analysis that:with the concentration of H2O2 and o-phenanthroline increasing the light of the system can be amplified effectively;compare with H2O2 and o-phenanthroline, Vc is not significant in luminous intensity and peak time and peak type of the light-emitting system;Increased concentration of CuSO4 can can effectively advance the peak time, the appropriate concentration range can also be effectively amplified light; the pH change of borate buffer solution on the system is relatively small impact at luminous intensity and the peak time, but bigger than Vc.Application quantum chemistry density functional theory at the B3LYP method of 6-311g(d,p) basis set optimize the geometric structure of 10 antioxidant oligopeptides,like GSH, REW, RVF, FM, VHHH, AQIPQQ, VIPAGYP, VIPAGY IPAGYP PAGY,obtain the structure and energy parameters of each peptide, such as the energies of frontier orbital and charge distribution and bond length, ect.According to the HOMO distribution of antioxidant oligopeptide, obtaining the active spots of the molecule,then according to the parameters such as charge distribution and the bond length, calculated out the minimum coulomb force bond in the active site,to analyze the avtive spot of the molecule.Combined with detection result in vitro about antioxidant peptide scavenging free radicals (O2-·、·OH) activity and chelating metal ions (Fe2+) activity, we found:Antioxidant activity of 7peptides in those oligopeptides scavenging O2-·(y)has good correlation with the minimum coulomb force (x)in the active spot; the mathematical model of the structure-activity relationships can be expressed with the equation:y=1.3994x-0.9106,R2=0.9317; antioxidant activity of 4 peptides in those oligopeptides scavenging-OH(y)has good correlation with the frontier orbital energy gap ΔEL-H(x):y=1.0641x-196.99,R2=0.9865; Antioxidant activity of 4 peptides in those oligopeptides chelating-OH(y)has good correlation with the energy of HOMO EHOMO(x):y =-2.1814x-0.4180,R2=0.9441.So we can use the minimum coulomb force in the active spot, the frontier orbital energy gap ΔEL-H and the energy of HOMO EHOMO to characterize the value of the antioxidant activity of oligopeptide, thereby to provide the theoretical basis for the screening of an oligopeptide having a high activity antioxidant and the guidance for develop-ing, changing, synthesizing antioxidant peptides about functional food, additives, and drug.Missing the amino-terminal of antioxidative oligopeptide VIPAGYP in order, obtaining three oligopeptide, like VIPAGY, IPAGYP,PAGY,the structure and energy parameters of four homogeneous series oligopeptide by quantum chemical calculations and antioxidant activity measured in vitro suggested:Pro located at the end of peptide is useful in promoting antioxidant activity;Tyr located at C-terminus is more beneficial for antioxidant peptides to scaveng free radical than Pro located at C-terminus;Hydrophobic amino acids can reinforce the antioxidant activity of pepides.