State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Science, Beijing 10012, China.
Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.
Sci Total Environ. 2018 Mar;616-617:1279-1287. doi: 10.1016/j.scitotenv.2017.10.190. Epub 2017 Oct 21.
Heterogeneous distributions of proton binding sites within sub-fractions of fulvic acid (FA-FA) were investigated by use of synchronous fluorescence spectra (SFS), combined with principle component analysis (PCA) and two-dimensional correlation spectroscopy (2D-COS). Tryptophan-like, fulvic-like and humic-like materials were observed in SFS. Tyrosine-like materials were identified by use of SFS-PCA analysis. Combined information from synchronous-asynchronous maps and dissociation constants (pKa) was used to describe heterogeneity of binding sites for protons within each sub-fraction. Heterogeneous distributions of proton binding sites were observed in fulvic-like, humic-like, tryptophan-like, and tyrosine-like materials of five sub-fractions and even in the single fulvic-like materials in FA and tryptophan-like materials in FA and FA. Values of pKa of sub-fractions ranged from 2.20 to 5.29, depending on associated wavelengths in synchronous-asynchronous maps and use of the modified Stern-Volmer equation. The larger values of pKa (4.17-5.29) were established for protein-like materials (including tryptophan-like and tyrosine-like materials) in comparison to those (2.20-3.38) for humic-like and fulvic-like materials in sub-fractions. Sequential variations of 274nm (pKa 4.15-5.29)→360-460nm (pKa 2.78-2.39) for FA-FA revealed that binding of protons to tryptophan-like materials appeared prior to humic-like/fulvic-like materials. In FA, protons were preferentially binding to tryptophan-like materials than tyrosine-like materials. In FA, protons were preferentially binding to humic-like materials than fulvic-like materials. Relative differences of values of pKa for fluorescent materials within each sub-fraction were consistent with sequential orders derived from asynchronous maps. Such an integrated approach, SFS-PCA/2D-COS, has superior potential for further applications in exploring complex interactions between dissolved organic matter and contaminants in engineered and natural environments.
利用同步荧光光谱（SFS）、主成分分析（PCA）和二维相关光谱（2D-COS）研究了富里酸（FA）亚组分中质子结合位点的不均匀分布。SFS 中观察到色氨酸样、富里酸样和腐殖酸样物质。通过 SFS-PCA 分析鉴定了酪氨酸样物质。结合同步-异步图谱和离解常数（pKa）的信息，用于描述每个亚组分中质子结合位点的不均匀性。在五个亚组分的富里酸样、腐殖酸样、色氨酸样和酪氨酸样物质中，甚至在 FA 中的单一富里酸样物质和 FA 和 FA 中的色氨酸样物质中，都观察到了质子结合位点的不均匀分布。亚组分的 pKa 值范围为 2.20 至 5.29，具体取决于同步-异步图谱中的相关波长和使用修正的 Stern-Volmer 方程。与腐殖酸样和富里酸样物质（pKa 2.20-3.38）相比，蛋白样物质（包括色氨酸样和酪氨酸样物质）的 pKa 值较大（4.17-5.29）。FA-FA 的 274nm（pKa 4.15-5.29）→360-460nm（pKa 2.78-2.39）的顺序变化表明，质子与色氨酸样物质的结合先于腐殖酸样/富里酸样物质。在 FA 中，质子优先与色氨酸样物质结合，而不是与酪氨酸样物质结合。在 FA 中，质子优先与腐殖酸样物质结合，而不是与富里酸样物质结合。每个亚组分中荧光物质的 pKa 值的相对差异与异步图谱得出的顺序一致。这种综合方法，SFS-PCA/2D-COS，在探索工程和自然环境中溶解有机物与污染物之间的复杂相互作用方面具有更大的应用潜力。
