X-ray absorption fine structure of artificial antigens for cadmium |
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Authors: | Lu Liang Liu Aiping Chen Fusheng Wang Xiaohong |
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Affiliation: | aKey Laboratory of Food Safety Evaluation of Ministry of Agriculture, Huazhong Agricultural University, Wuhan 430070, Hubei Province, PR China;bCollege of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, Hubei Province, PR China |
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Abstract: | Immunoassay technology as a quick and large-scale screening method to detect metal ions in foods and environmental samples has rapidly been developed due to several advantages over conventional instrument-intensive methods. Unlike biomacromolecule, metal ions are haptens without immunogenicity, so successful preparation of artificial antigens is the first critical step for establishing immunoassay methods for them. In the current paper, cadmium ions were conjugated to BSA and OVA, respectively, using bifunctional chelator, p-SCN-Bn-DTPA. The ultraviolet analysis indicated that the maximum absorption peak of Cd–p-SCN-DTPA–BSA and Cd–p-SCN-DTPA–OVA had a small peak shift and an apparent absorbance increase compared to that of BSA and OVA, and the extents of substitution of ?-amino in both conjugates were 51.2% and 58.6%, respectively. In addition, the EXAFS of conjugates implied that Cd2+ coordinated with N and O atoms of DTPA in artificial antigens, the coordination type and number of Cd–DTPA, Cd–p-SCN-Bn-DTPA–BSA, Cd–p-SCN-Bn-DTPA–OVA were the same. XANES region and geometries of the three compounds were also same. These results implied that the three antigens had the similar local structure and atomic geometry.This was the first time that the XAFS was attempted for the identification of artificial heavy metal ion antigens. |
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Keywords: | Abbreviations: BSA, bovine serum albumin OVA, ovalbumin p-SCN-Bn-DTPA, 2-(4-isothiocyanatobenzyl)-diethylenetriaminepentaacetic acid XAFS, X-ray absorption fine structure EXAFS, extended X-ray absorption fine structure XANES, X-ray absorption near edge structure SDS&ndash PAGE, sodium dodecyl sulfate&ndash polyacrylamide gel electrophoresis ICP-AES, inductively coupled plasma atomic emission spectroscopy ICP-MS, inductively coupled plasma mass spectrometry ELISA, enzyme-linked immunosorbent assay ITCBE, 1-(4-isothiocyanatobenzyl)-ethylenediamine-N,N,N&prime ,N&prime -tetraacetic acid HEPES, N-[2-hydroxyethyl]piperazine-N&prime -[2-ethane-sulfonic acid] TNBS, 2,4,6-trinitrobenzene-1-sulfonic acid AAS, atomic absorbance spectroscopy AFS, atomic fluorescence spectrometry HPCE, high-performance capillary electrophoresis MALDI-TOF MS, matrix assisted laser desorption ionization-time of flight mass spectrometry EDTA, ethylenediamine-N,N,N&prime ,N&prime -tetraacetic acid DTPA, diethylenetriaminepentaacetic acid |
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