干旱区研究2018，Vol.35Issue(1)：243-248,6.DOI:10.13866/j.azr.2018.01.30
新疆奎屯排碱渠生物膜胞外聚合物与As(Ⅲ)的络合作用
Complexation of As (Ⅲ) with Extracellular Polymeric Substance from Biofilm in the Salt-discharging Channel in Kuytun, Xinjiang
摘要
Abstract
There is a heavy arsenic pollution in the salt-discharging channel due to the geological background in Kuytun,Xinjiang.The complexation between extracellular polymeric substance of the algal biofilm and As (Ⅲ) influences the transportation and diffusion of arsenic and further affects the biological toxicity and the ecological risk of arsenic.At present,the effects of the widespread biofilm on the transport and fate of arsenic in channel are completely unknown.In this study,the interaction of extracellular polymeric substance of the algal biofilm and As (Ⅲ) was investigated by fluorescence quenching test and isothermal titration calorimetry.The results of fluorescence quenching test showed that the fluorescent components of extracellular polymeric substance were composed of three fluorescence peaks:Peak A belonged to aromatic protein Ⅱ,Peak B belonged to soluble microbial by-product-like,and Peak C belonged to humic acid-like.Peak A and B were collectively referred to protein-like substance,and peak B was further intended to be tryptophan-like substance.There was a strong complexation between the proteinlike substance and As (Ⅲ),while the interaction between As (Ⅲ) and the humic-like substance was ignorable.Both static quenching and dynamic collision were involved in fluorescence quenching of extracellular polymeric substance by As (Ⅲ).The binding constant,lgKb,for interaction of As (Ⅲ) with the aromatic protein-like substance and tryptophan-like substance were 3.82 and 2.22 respectively,indicating the binding affinity of As (Ⅲ) to the former is one order of magnitude greater than the latter.Multiple sites were involved in competition for binding As (Ⅲ) in the aromatic protein-like substance,and only one class of binding sites were taken part in tryptophan-like substance for their complexation with As (Ⅲ).The data obtained from isothermal titration calorimetry test were fitted by independent model,and the thermal dynamic parameters △H,△G and △S of complexation reaction were acquired.Negative enthalpy change △H and negative Gibbs free energy △G proved that the complexation between extracellular polymeric substance and the As (Ⅲ) is a spontaneous exothermic reaction.The degree of disorder in the complexing reaction increases,and the reaction is driven by entropy.The protein-like substance in the biofilm in salt-discharging channel may have significant effects on environmental fate and risk of arsenic,while the role of humic acid-like substance in extracellular polymeric substance is ignorable.关键词
排碱渠/砷污染/生物膜/胞外聚合物/荧光猝灭/等温量热滴定/奎屯/新疆Key words
salt-discharging channel/arsenic pollution/biofilm/EPS/fluorescence quenching/isothermal titration calorimetry/Kuytun/Xinjiang引用本文复制引用
林青华,张道勇..新疆奎屯排碱渠生物膜胞外聚合物与As(Ⅲ)的络合作用[J].干旱区研究,2018,35(1):243-248,6.基金项目
新疆维吾尔自治区重点实验室开放课题(2015KL025) （2015KL025）
国家自然科学基金项目(U1403181)资助 （U1403181）
