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
The ongoing SARS-CoV-2 outbreak has rapidly increased the desire to manage bioaerosol exposures in indoor settings. Studies using chlorine dioxide gas (ClO<sub>2</sub>) at low concentrations have shown thi...The ongoing SARS-CoV-2 outbreak has rapidly increased the desire to manage bioaerosol exposures in indoor settings. Studies using chlorine dioxide gas (ClO<sub>2</sub>) at low concentrations have shown this intervention to be an effective mitigation strategy against viral, bacterial, and fungal elements in ambient air. There is an array of available products for generating ClO<sub>2</sub> gas however most involve the use of expensive or sophisticated technology that makes their applicability limited to specialized consumers. The purpose of this study was to determine the virucidal efficacy of three pragmatic and affordable, ClO<sub>2</sub> generating products using an aerosolized MS2 surrogate in a sealed chamber room under five different scenarios. The products tested included: Ultrashock—a ClO<sub>2</sub> releasing pod (30 ppmv), Filter Media—a ClO<sub>2</sub> impregnated zeolite media made to fit into an air blower housing (<0.01 ppmv) and Flow Stick—a smaller ClO<sub>2</sub> impregnated media filled air reactor tube (<0.01 ppmv). Testing scenarios included product deployment post MS2 bioaerosol introduction (Ultrashock and Filter Media), during MS2 bioaerosol introduction (Filter Media and Flow Stick) and prior to MS2 bioaerosol introduction (Filter Media). MS2 surface samples were collected using sterile petri-dishes and MS2 and ClO<sub>2</sub> air samples were collected from sampling ports on the outer chamber wall at 0, 90 and 180 minutes. The Ultrashock and Filter Media with air flow in the rapid sweep scenario showed the greatest reduction in air MS2 (T<sub>180</sub> = 99.992% and T<sub>180</sub> = 99.996% respectively) compared to the control (T<sub>180 </sub>= 99.6%). When compared to the control results, the filter media with air flow engaged prior to the introduction of MS2 yielded reductions of 99.87% and 99.93% in air and on surfaces respectively at T<sub>0</sub>, demonstrating the protective effect residual ClO2 has against air and surface contamination. These product formats have potential uses as remedial and preventative interventions against viral constituents in air and should undergo further evaluation to determine efficacy and human health risk.展开更多
A mixed oxidant of chlorine dioxide(ClO_(2))and NaClO was often used in water treatment.A novel UVA-LED(_(365) nm)-activated mixed ClO_(2)/NaClO process was proposed for the degradation of micropollutants in this stud...A mixed oxidant of chlorine dioxide(ClO_(2))and NaClO was often used in water treatment.A novel UVA-LED(_(365) nm)-activated mixed ClO_(2)/NaClO process was proposed for the degradation of micropollutants in this study.Carbamazepine(CBZ)was selected as the target pollutant.Compared with the UVA_(365)/ClO_(2) process,the UVA_(365)/ClO_(2)/NaClO process can improve the degradation of CBZ,with the rate constant increasing from 2.11×10^(−4) sec^(−1) to 2.74×10^(−4) sec^(−1).In addition,the consumption of oxidants in the UVA_(365)/ClO_(2)/NaClO process(73.67%)can also be lower than that of UVA_(365)/NaClO(86.42%).When the NaClO ratio increased,both the degradation efficiency of CBZ and the consumption of oxidants can increase in the UVA_(365)/ClO_(2)/NaClO process.The solution pH can affect the contribution of NaClO in the total oxidant ratio.When the pH range of 6.0-8.0,the combination process can generate more active species to promote the degradation of CBZ.The change of active species with oxidant molar ratio was investigated in the UVA_(365)/ClO_(2)/NaClO process.When ClO_(2) acted as the main oxidant,HO·and Cl·were the main active species,while when NaClO was the main oxidant,ClO·played a role in the system.Both chloride ion(Cl^(-)),bicarbonate ion(HCO_(3)^(-)),and nitrate ion(NO_(3)^(-))can promote the reaction system.As the concentration of NaClO in the reaction solution increased,the generation of chlorates will decrease.The UVA_(365)/ClO_(2)/NaClO process can effectively control the formation of volatile disinfection by-products(DBPs),and with the increase of ClO_(2) dosage,the formation of DBPs can also decrease.展开更多
In acidic medium, malonic used as masking agent, let the mixed aqueous of chlorine dioxide and chlorine react with Fe2+, then have the residual Fe2+ coloured with 1.10phenanthroline solution. The authors...In acidic medium, malonic used as masking agent, let the mixed aqueous of chlorine dioxide and chlorine react with Fe2+, then have the residual Fe2+ coloured with 1.10phenanthroline solution. The authors can quantify the content of chlorine dioxide and chlorine in the water by detecting the difference of absorbtivity of the coloured solution when it is no masking agent and it is added masking agent. The method is simple, innocuity, specific, quick, accurate and sensitive. The mini detect limitation are:Chlorine: 7.66×10-3mg/L,dioxide Chlorine: 2.91×10-3mg/L.R is 0.9997,CV is 2.55%.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.
文摘The ongoing SARS-CoV-2 outbreak has rapidly increased the desire to manage bioaerosol exposures in indoor settings. Studies using chlorine dioxide gas (ClO<sub>2</sub>) at low concentrations have shown this intervention to be an effective mitigation strategy against viral, bacterial, and fungal elements in ambient air. There is an array of available products for generating ClO<sub>2</sub> gas however most involve the use of expensive or sophisticated technology that makes their applicability limited to specialized consumers. The purpose of this study was to determine the virucidal efficacy of three pragmatic and affordable, ClO<sub>2</sub> generating products using an aerosolized MS2 surrogate in a sealed chamber room under five different scenarios. The products tested included: Ultrashock—a ClO<sub>2</sub> releasing pod (30 ppmv), Filter Media—a ClO<sub>2</sub> impregnated zeolite media made to fit into an air blower housing (<0.01 ppmv) and Flow Stick—a smaller ClO<sub>2</sub> impregnated media filled air reactor tube (<0.01 ppmv). Testing scenarios included product deployment post MS2 bioaerosol introduction (Ultrashock and Filter Media), during MS2 bioaerosol introduction (Filter Media and Flow Stick) and prior to MS2 bioaerosol introduction (Filter Media). MS2 surface samples were collected using sterile petri-dishes and MS2 and ClO<sub>2</sub> air samples were collected from sampling ports on the outer chamber wall at 0, 90 and 180 minutes. The Ultrashock and Filter Media with air flow in the rapid sweep scenario showed the greatest reduction in air MS2 (T<sub>180</sub> = 99.992% and T<sub>180</sub> = 99.996% respectively) compared to the control (T<sub>180 </sub>= 99.6%). When compared to the control results, the filter media with air flow engaged prior to the introduction of MS2 yielded reductions of 99.87% and 99.93% in air and on surfaces respectively at T<sub>0</sub>, demonstrating the protective effect residual ClO2 has against air and surface contamination. These product formats have potential uses as remedial and preventative interventions against viral constituents in air and should undergo further evaluation to determine efficacy and human health risk.
基金supported by the National Natural Science Foundation of China (No.52170006)。
文摘A mixed oxidant of chlorine dioxide(ClO_(2))and NaClO was often used in water treatment.A novel UVA-LED(_(365) nm)-activated mixed ClO_(2)/NaClO process was proposed for the degradation of micropollutants in this study.Carbamazepine(CBZ)was selected as the target pollutant.Compared with the UVA_(365)/ClO_(2) process,the UVA_(365)/ClO_(2)/NaClO process can improve the degradation of CBZ,with the rate constant increasing from 2.11×10^(−4) sec^(−1) to 2.74×10^(−4) sec^(−1).In addition,the consumption of oxidants in the UVA_(365)/ClO_(2)/NaClO process(73.67%)can also be lower than that of UVA_(365)/NaClO(86.42%).When the NaClO ratio increased,both the degradation efficiency of CBZ and the consumption of oxidants can increase in the UVA_(365)/ClO_(2)/NaClO process.The solution pH can affect the contribution of NaClO in the total oxidant ratio.When the pH range of 6.0-8.0,the combination process can generate more active species to promote the degradation of CBZ.The change of active species with oxidant molar ratio was investigated in the UVA_(365)/ClO_(2)/NaClO process.When ClO_(2) acted as the main oxidant,HO·and Cl·were the main active species,while when NaClO was the main oxidant,ClO·played a role in the system.Both chloride ion(Cl^(-)),bicarbonate ion(HCO_(3)^(-)),and nitrate ion(NO_(3)^(-))can promote the reaction system.As the concentration of NaClO in the reaction solution increased,the generation of chlorates will decrease.The UVA_(365)/ClO_(2)/NaClO process can effectively control the formation of volatile disinfection by-products(DBPs),and with the increase of ClO_(2) dosage,the formation of DBPs can also decrease.
文摘In acidic medium, malonic used as masking agent, let the mixed aqueous of chlorine dioxide and chlorine react with Fe2+, then have the residual Fe2+ coloured with 1.10phenanthroline solution. The authors can quantify the content of chlorine dioxide and chlorine in the water by detecting the difference of absorbtivity of the coloured solution when it is no masking agent and it is added masking agent. The method is simple, innocuity, specific, quick, accurate and sensitive. The mini detect limitation are:Chlorine: 7.66×10-3mg/L,dioxide Chlorine: 2.91×10-3mg/L.R is 0.9997,CV is 2.55%.
