| 摘要: |
| 以菲律宾蛤仔(Ruditapes philippinarum)为受试生物，研究了全氟辛酸(PFOA)及其醚羧酸替代品(HFPO-DA、HFPO-TA、HFPO-TeA)的生物富集、组织分布与消除规律以及机体蛋白质对目标物蓄积的影响。通过计算动力学参数，解析菲律宾蛤仔对PFOA及其醚羧酸替代品的富集、分布与消除行为。此外，通过提取菲律宾蛤仔体内水溶性蛋白，进行了体外蛋白质孵育实验，分析不同目标物与蛤仔机体蛋白质的结合率差异，并进一步通过分子对接技术，探讨了目标物分子–蛋白质之间的结合作用力及其与富集特征的相关性。结果表明，PFOA及其醚羧酸替代品在菲律宾蛤仔体内快速富集，富集速率按照HFPO-DA、PFOA、HFPO-TA、HFPO-TeA的顺序依次升高，在不同组织中的富集作用由强到弱依次为内脏团、鳃、外套膜、闭壳肌，并在净化21 d后趋于空白组水平。PFOA及其醚羧酸替代品在菲律宾蛤仔体内的蓄积能力、不同目标物分子–蛤仔机体蛋白质的结合率均与目标物浓度密切相关，浓度越低，吸收速率常数(Ku)和生物浓缩系数(BCF)越大，蛋白质结合率越低，其分子结构也是富集能力强弱和蛋白质结合力强弱的关键影响因素，C-O键和碳氟链的增加有助于目标物分子与蛋白质残基的碱基结合，目标物在各组织中的含量和蛋白结合率由低到高依次为HFPO-DA、PFOA、HFPO-TA、HFPO-TeA。使用分子对接技术进一步验证了4个目标物与脂肪酸结合蛋白FABP1-A之间的结合作用力，其结合能由低到高依次为HFPO-TeA、HFPO-TA、PFOA、HFPO-DA，结合能越低，越容易与蛋白质结合。目标物的极性端与FABP1-A氨基酸残基直接形成氢键，疏水端则与非极性残基有疏水相互作用，氢键作用与疏水相互作用共同促进了PFOA及其醚羧酸替代品与蛋白质的相互结合，氢键数量的多少是导致目标物与蛋白结合亲和力差异的重要原因。本研究结果有助于阐释双壳贝类中PFOA及其醚羧酸替代品的差异化生物富集行为及富集机制，为新污染物的防控和治理奠定科学基础。 |
| 关键词: 全氟辛酸(PFOA) 醚羧酸替代品 菲律宾蛤仔 生物富集 蛋白质结合模式 |
| DOI：10.19663/j.issn2095-9869.20240520001 |
| 分类号: |
| 基金项目:现代农业产业技术体系专项资金(CARS-49)和中国水产科学研究院基本科研业务费(2023TD76)共同资助 |
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| Accumulation differences in perfluorooctanoic acid and its ether carboxylic acid alternatives in the Manila clam (Ruditapes philippinarum) |
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QIN Hanlin1,2, BI Yujie2, JIANG Shuqi3, WU Chengchen1,2, TAN Zhijun2, GENG Qianqian3, GUO Mengmeng4
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1.College of Food Sciences & Technology, Shanghai Ocean University, Shanghai 201306, China;2.State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China;3.State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266072, China;4.State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266073, China
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| Abstract: |
| Perfluorooctanoic acid (PFOA) is a synthetic organic chemical with unique hydrophobic and oleophobic properties. It is extensively used in the production of a wide range of essential industrial and consumer products including aqueous film-forming foams, medical devices, and textiles. PFOA is widespread in aquatic environments and has attracted global attention due to the serious ecological risks it poses. Consequently, several countries and organizations have implemented strict restrictions or controls on its use. In 2019, PFOA and its salts were included as Annex A of the Stockholm Convention on Persistent Organic Pollutants, and in 2023, the Ministry of Ecology and Environment of the People's Republic of China and six other departments issued the "Key Regulated New Pollutant List 2023", which proposed environmental risk control measures for PFOA, its salts, and related compounds. With an increase in regulatory measures, the production and use of PFOA have declined, resulting in the rapid development and use of alternatives. Hexafluoropropylene oxide dimer acid (HFPO-DA), trimer acid (HFPO-TA), and tetramer acid (HFPO-TeA)—composed of CF2 or CF2O repeating units—have emerged as principal alternatives that maintain chemical properties similar to those of PFOA and are predominantly used in the manufacture of fluoropolymers and their processing aids.
As filter-feeding organisms, bivalves are prolific and have a broad geographic distribution. They possess a marked capacity for accumulating organic contaminants, making them ideal indicators for monitoring pollution in marine environments and assessing the status of various marine ecosystems. Therefore, Manila clams (Ruditapes philippinarum) were used as the test organism in this study and exposed to two concentrations (2 ng/mL and 200 ng/mL) of PFOA and its alternatives—HFPO-DA, HFPO-TA, HFPO-TeA—within a mariculture setting.
The purpose of this study was to analyze the tissue distribution, accumulation, and elimination patterns of these compounds in clams, and to evaluate differences in the accumulation ability of organisms to enrich PFOA and its ether carboxylic acid alternatives in clams by calculating kinetic parameters. Additionally, water-soluble proteins were extracted from the visceral masses and gills of the clams and incubated in vitro to explore the differences in binding rates between the target compounds and clam proteins. The binding modes between the target molecules and proteins were investigated using molecular docking techniques to further elucidate the relationship between molecular and protein interactions and the bioaccumulation properties of clams.
It was found that that PFOA and its ether carboxylic acid alternatives were rapidly enriched in Manila clams. The enrichment rate of targets increased as HFPO-DA < PFOA < HFPO-TA < HFPO-TeA, and the enrichment effects in different tissues were visceral mass > gill > mantle > adductor muscle. After a 21-day depuration period, the contaminant levels in Manila clams approached those in the control group. Furthermore, in Manila clams, the accumulation capacity of PFOA and its alternatives, and the binding rates of different target molecules to body proteins were strongly correlated with the target concentrations. Lower target concentrations led to greater absorption rate constants and bioconcentration factors and lower binding rates of the targets to the protein. The target content and protein binding in each tissue were HFPO-DA < PFOA < HFPO-TA < HFPO-TeA. Additionally, the molecular structure of PFOA and its alternatives—particularly the increase in C-O bonds and C-F chains—enhanced their binding affinities with protein residues. The binding forces between PFOA, its alternatives, and the fatty acid-binding protein FABP1-A were further validated by molecular docking studies. The magnitude of the binding energy was HFPO-TeA < HFPO-TA < PFOA < HFPO-DA, and the lower the binding energy, the easier it was to bind to the protein. The polar ends of the targets formed hydrogen bonds with the amino acid residues of FABP1-A, whereas their hydrophobic ends engaged in hydrophobic interactions with nonpolar residues, collectively enhancing the protein binding of PFOA and its alternatives. The number of hydrogen bonds is also an important cause of binding affinity differences in the target proteins.
This study elucidates the bioaccumulation behavior of PFOA and its alternatives in bivalves and provides a scientific basis for the control and management of emerging contaminants. Although the levels of PFOA and its alternatives in aquatic environments are currently traceable, the ecological risks associated with their persistence in the environment should not be underestimated. Moreover, the findings on their binding rates to clam proteins offer a scientific basis for the reasonable selection of alternatives. Additionally, the molecular docking data furnish a theoretical basis for investigating the specific binding of PFOA and its alternatives to proteins with different carbon chain lengths and structures. |
| Key words: Perfluorooctanoic acid (PFOA) Ether carboxylic acid alternatives Manila clams (Ruditapes philippinarum) Bioaccumulation Protein binding modes |
