{"title":"巯基阻断β-乳球蛋白a、-B和-C与碘酸盐的结合","authors":"William L. Stone*, Arnold Wishnia","doi":"10.1016/0006-3061(78)80005-2","DOIUrl":null,"url":null,"abstract":"<div><p>Sulfhydryl-blocked β-lactoglobulins (β-LG-S-SCH<sub>2</sub>CH<sub>2</sub>OH)-<em>A</em>, -<em>B</em>, and -<em>C</em> bind only one iodomercurate species, HgI<sub>3−</sub>, at only one site, with a dissociation constant of 4.0 x 10<sub>−5</sub>M at 25°, pH 5.0, 0.10 ionic strength. (Binding to native β-LG-SH-<em>A</em>, -<em>B</em>, and -<em>C</em> is more complex, involving the sulfhydryl and two other sites and several iodomercurates). Ther red shift of the HgI<sub>3−</sub> spectrum on binding would ordinarily suggest a hydrophobic site, but the HgI<sub>3−</sub> site is distinct from, and independent of, the alkane-binding site of native and blocked β-LG:HgI<sub>3−</sub> may bind a group that shifts its trigonal planar structure toward the tetrahedron of HgI<sub>4</sub><sup>2−</sup>. Binding of HgI<sub>3−</sub> to blocked β-LG interferes with the well-known association of β-LG-<em>A</em> to octamers at pH 4.6 and low temperature. The relation of the HgI<sub>3−</sub> site to the crystallographic iodomercurate-binding sites of β-LG-SH is examined.</p><p>To facilitate these and future studies if iodomercurate binding, the 200-400 nm spectra of HgI<sub>2</sub>. HgI<sub>3−</sub>, and HgI<sub>4</sub><sup>2−</sup> in aqueous solutions and the thermodynamic formation constants at 25° for the equilibria HgI<sub>2</sub> + I−=HgI<sub>3−</sub> (4.9 x 10<sup>3</sup> M−<sup>1</sup> and HgI<sub>3−</sub> + I−=HgI<sub>4</sub><sup>2−</sup> (0.118 x 10<sup>3</sup> M−<sup>1</sup>) were obtained.</p></div>","PeriodicalId":9177,"journal":{"name":"Bioinorganic chemistry","volume":"8 6","pages":"Pages 517-529"},"PeriodicalIF":0.0000,"publicationDate":"1978-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0006-3061(78)80005-2","citationCount":"5","resultStr":"{\"title\":\"Binding of Iodomercurates to Sulfhydryl-blocked β-Lactoglobulin-A,-B, and -C\",\"authors\":\"William L. Stone*, Arnold Wishnia\",\"doi\":\"10.1016/0006-3061(78)80005-2\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Sulfhydryl-blocked β-lactoglobulins (β-LG-S-SCH<sub>2</sub>CH<sub>2</sub>OH)-<em>A</em>, -<em>B</em>, and -<em>C</em> bind only one iodomercurate species, HgI<sub>3−</sub>, at only one site, with a dissociation constant of 4.0 x 10<sub>−5</sub>M at 25°, pH 5.0, 0.10 ionic strength. (Binding to native β-LG-SH-<em>A</em>, -<em>B</em>, and -<em>C</em> is more complex, involving the sulfhydryl and two other sites and several iodomercurates). Ther red shift of the HgI<sub>3−</sub> spectrum on binding would ordinarily suggest a hydrophobic site, but the HgI<sub>3−</sub> site is distinct from, and independent of, the alkane-binding site of native and blocked β-LG:HgI<sub>3−</sub> may bind a group that shifts its trigonal planar structure toward the tetrahedron of HgI<sub>4</sub><sup>2−</sup>. Binding of HgI<sub>3−</sub> to blocked β-LG interferes with the well-known association of β-LG-<em>A</em> to octamers at pH 4.6 and low temperature. The relation of the HgI<sub>3−</sub> site to the crystallographic iodomercurate-binding sites of β-LG-SH is examined.</p><p>To facilitate these and future studies if iodomercurate binding, the 200-400 nm spectra of HgI<sub>2</sub>. HgI<sub>3−</sub>, and HgI<sub>4</sub><sup>2−</sup> in aqueous solutions and the thermodynamic formation constants at 25° for the equilibria HgI<sub>2</sub> + I−=HgI<sub>3−</sub> (4.9 x 10<sup>3</sup> M−<sup>1</sup> and HgI<sub>3−</sub> + I−=HgI<sub>4</sub><sup>2−</sup> (0.118 x 10<sup>3</sup> M−<sup>1</sup>) were obtained.</p></div>\",\"PeriodicalId\":9177,\"journal\":{\"name\":\"Bioinorganic chemistry\",\"volume\":\"8 6\",\"pages\":\"Pages 517-529\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"1978-06-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1016/0006-3061(78)80005-2\",\"citationCount\":\"5\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Bioinorganic chemistry\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/0006306178800052\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Bioinorganic chemistry","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0006306178800052","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Binding of Iodomercurates to Sulfhydryl-blocked β-Lactoglobulin-A,-B, and -C
Sulfhydryl-blocked β-lactoglobulins (β-LG-S-SCH2CH2OH)-A, -B, and -C bind only one iodomercurate species, HgI3−, at only one site, with a dissociation constant of 4.0 x 10−5M at 25°, pH 5.0, 0.10 ionic strength. (Binding to native β-LG-SH-A, -B, and -C is more complex, involving the sulfhydryl and two other sites and several iodomercurates). Ther red shift of the HgI3− spectrum on binding would ordinarily suggest a hydrophobic site, but the HgI3− site is distinct from, and independent of, the alkane-binding site of native and blocked β-LG:HgI3− may bind a group that shifts its trigonal planar structure toward the tetrahedron of HgI42−. Binding of HgI3− to blocked β-LG interferes with the well-known association of β-LG-A to octamers at pH 4.6 and low temperature. The relation of the HgI3− site to the crystallographic iodomercurate-binding sites of β-LG-SH is examined.
To facilitate these and future studies if iodomercurate binding, the 200-400 nm spectra of HgI2. HgI3−, and HgI42− in aqueous solutions and the thermodynamic formation constants at 25° for the equilibria HgI2 + I−=HgI3− (4.9 x 103 M−1 and HgI3− + I−=HgI42− (0.118 x 103 M−1) were obtained.