Chlorine dioxide(ClO2),an alternative disinfectant to chlorine,has a superior ability to inactivate microorganisms,in which protein damage has been considered as the main inactivation mechanism.However,the reactivity ...Chlorine dioxide(ClO2),an alternative disinfectant to chlorine,has a superior ability to inactivate microorganisms,in which protein damage has been considered as the main inactivation mechanism.However,the reactivity of ClO2 with amino acid residues in oligopeptides and proteins remains poorly investigated.In this research,we studied the reaction rate constants of ClO2 with tryptophan residues in five heptapeptides and four proteins using stopped-flow or competition kinetic method.Each heptapeptide and protein contain only one tryptophan residue and the reactivity of tryptophan residue with ClO2 was lower than that of free tryptophan(3.88×10^4(mol/L)^-1 sec^-1 at pH 7.0).The neighboring amino acid residues affected the reaction rates through promoting inter-peptide aggregation,changing electron density,shifting pKa values or inducing electron transfer via redox reactions.A single amino acid residue difference in oligopeptides can make the reaction rate constants differ by over 60%(e.g.3.01×10^4(mol/L)^-1 sec^-1 for DDDWNDD and 1.85×10^4(mol/L)^-1 sec^-1 for DDDWDDD at pH 7.0(D:aspartic acid,W:tryptophan,N:asparagine)).The reaction rates of tryptophan-containing oligopeptides were also highly pH-dependent with higher reactivity for deprotonated tryptophan than the neutral specie.Tryptophan residues in proteins spanned a 4-fold range reactivity toward ClO2(i.e.0.84×10^4(mol/L)^-1 sec^-1 for ribonuclease T1 and 3.21×10^4(mol/L)^-1 sec^-1 for melittin at pH 7.0)with accessibility to the oxidant as the determinating factor.The local environment surrounding the tryptophan residue in proteins can also accelerate the reaction rates by increasing the electron density of the indole ring of tryptophan or inhibit the reaction rates by inducing electron transfer reactions.The results are of significance in advancing understanding of ClO2 oxidative reactions with proteins and microbial inactivation mechanisms.展开更多
基金supported by the National Key Research and Development Program of China(No.2017YFE0133200)the National Natural Science Foundation of China(Nos.21622706 and 21876210)the Guangdong Provincial Science and Technology Planning Project(No.2019A050503006)。
文摘Chlorine dioxide(ClO2),an alternative disinfectant to chlorine,has a superior ability to inactivate microorganisms,in which protein damage has been considered as the main inactivation mechanism.However,the reactivity of ClO2 with amino acid residues in oligopeptides and proteins remains poorly investigated.In this research,we studied the reaction rate constants of ClO2 with tryptophan residues in five heptapeptides and four proteins using stopped-flow or competition kinetic method.Each heptapeptide and protein contain only one tryptophan residue and the reactivity of tryptophan residue with ClO2 was lower than that of free tryptophan(3.88×10^4(mol/L)^-1 sec^-1 at pH 7.0).The neighboring amino acid residues affected the reaction rates through promoting inter-peptide aggregation,changing electron density,shifting pKa values or inducing electron transfer via redox reactions.A single amino acid residue difference in oligopeptides can make the reaction rate constants differ by over 60%(e.g.3.01×10^4(mol/L)^-1 sec^-1 for DDDWNDD and 1.85×10^4(mol/L)^-1 sec^-1 for DDDWDDD at pH 7.0(D:aspartic acid,W:tryptophan,N:asparagine)).The reaction rates of tryptophan-containing oligopeptides were also highly pH-dependent with higher reactivity for deprotonated tryptophan than the neutral specie.Tryptophan residues in proteins spanned a 4-fold range reactivity toward ClO2(i.e.0.84×10^4(mol/L)^-1 sec^-1 for ribonuclease T1 and 3.21×10^4(mol/L)^-1 sec^-1 for melittin at pH 7.0)with accessibility to the oxidant as the determinating factor.The local environment surrounding the tryptophan residue in proteins can also accelerate the reaction rates by increasing the electron density of the indole ring of tryptophan or inhibit the reaction rates by inducing electron transfer reactions.The results are of significance in advancing understanding of ClO2 oxidative reactions with proteins and microbial inactivation mechanisms.
