J. Douglas Ashbrook

The binding of six physiologically important long chain fatty acids to defatted human plasma albumin was measured at 37 degrees in a calcium-free Krebs-Ringer phosphate buffer, pH 7.4. The data were analyzed in terms of multiple stepwise equilibria. With the saturated acids, the magnitude of the equilibrium (association) constants, Ki, increased as the chain length increased: laurate smaller than myristate smaller than palmitate smaller than stearate. Oleate was bound more tightly than stearate; by contrast, linoleate was bound less tightly than stearate. The equilibrium constants, K1 through K12, ranged from 2.4 times 10-6 - 3.5 times 10-3 m-1 for laurate to 2.6 times 10-8 - 3.5 times 10-5 m-1 for oleate. Successive values of Ki decrease for each of the acids, indicating that major cooperative binding effects do not occur over the physiological range of fatty acid concentrations. In no case could the Ki be segregated into distinct classes, suggesting that any grouping of albumin binding sites is somewhat arbitrary. The results were inconclusive concerning whether premicellar association of unbound fatty acid occurs. Although corrections for premicellar association produced very little change in the Ki values for myristate, they raised the Ki for palmitate and stearate by 300 to 700 per cent. A sigmoidal relationship was obtained when the logarithm of Ki was plotted against chain length for the saturated fatty acids containing 6 to 18 carbon atoms, indicating that the binding energy is not simply a statistical process dependent only on the fatty acid chain length. This selectivity that albumin contributes to the binding process may be due to varying degrees of configurational adaptability of its binding sites as the fatty acid increases in length.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnalysis of long-chain free fatty acid binding to bovine serum albumin by determination of stepwise equilibrium constantsJohn E. Fletcher, Arthur A. Spector, and J. Douglas AshbrookCite this: Biochemistry 1971, 10, 17, 3229–3232Publication Date (Print):August 1, 1971Publication History Published online1 May 2002Published inissue 1 August 1971https://pubs.acs.org/doi/10.1021/bi00793a011https://doi.org/10.1021/bi00793a011research-articleACS PublicationsRequest reuse permissionsArticle Views1162Altmetric-Citations203LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnalysis of macromolecule-ligand binding by determination of stepwise equilibrium constantsJohn E. Fletcher, Arthur A. Spector, and J. Douglas AshbrookCite this: Biochemistry 1970, 9, 23, 4580–4587Publication Date (Print):November 1, 1970Publication History Published online1 May 2002Published inissue 1 November 1970https://pubs.acs.org/doi/10.1021/bi00825a018https://doi.org/10.1021/bi00825a018research-articleACS PublicationsRequest reuse permissionsArticle Views348Altmetric-Citations146LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Abstract The binding of hexanoic, octanoic, and decanoic acids to defatted human plasma albumin was measured by equilibrium dialysis at 37° in a calcium-free Krebs-Ringer phosphate buffer, pH 7.4. The results were analyzed in terms of multiple stepwise equilibria. For each of the albumin binding sites, the magnitude of the equilibrium constants increased as the chain length of the acid increased: decanoate g octanoate g hexanoate. The first six equilibrium constants ranged from 1.5 x 104 to 4.7 x 10 for hexanoate, from 3.4 x 104 to 1.2 x 103 for octanoate, and from 105 to 3.4 x 103 for decanoate. In each case, the equilibrium constants occurred in a generally descending order, suggesting that major cooperative binding effects do not occur over the physiologically important range of fatty acid-albumin molar ratios. The equilibrium constants calculated for each of the three acids could not be grouped in a common way in terms of classes of binding sites, indicating that a single, uniform class-site binding model cannot be applied to these medium chain fatty acids. Octanoate binding was relatively insensitive to pH changes over the range of 6.0 to 8.2. Decanoate binding also was similar at pH 6.5 and 7.4. A decrease in octanoate binding occurred when the albumin was acetylated or when the medium contained 6 m urea. Octanoate binding also was decreased when either palmitate or oleate was added to albumin, suggesting that medium chain fatty acid transport may be influenced by changes in the plasma long chain free fatty acid concentration.