
%0 Journal Article
%A Woods, EF 
%A Lilley, GG 
%A Jermyn, MA 
%T The self-association of glycosyl phenylazo dyes (Yariv antigens)
%J Australian Journal of Chemistry
%D 1978/10/01
%V 31
%N 10
%P 2225-2238
%K 
%R https://doi.org/10.1071/CH9782225
%U https://www.publish.csiro.au/paper/CH9782225 
%X The aggregation of tris(4-glycosyloxyphenylazo)phloroglucinol compounds (Yariv antigens) where glyco = &#946;-D-gluco, &#946;-D-manno, &#946;-D-galacto and &#945;- D-galacto has been investigated by equilibrium sedimentation, the photoelectric scanning absorption optical system being utilized. The compounds have been shown to undergo a strong self-association in water and an analysis procedure employing Laplace transforms indicated a very wide distribution of species in the ultracentrifuge cell at equilibrium. To determine the type of association the concentration of monomer as a function of total weight concentration was calculated by using the recently developed &#937; function. When the concentration of monomer is very low, as in the present case, the analysis is difficult because very slight curvature in the &#937;-function plot has a large effect on the extrapolation to zero concentration.     The results are best described by an isodesmic indefinite self- association. The &#946;-glucoside Yariv antigen was the most extensively investigated and the most highly purified sample was shown to have an association constant of 2.5 x 107 l. mol-1. The order of the association constants of the Yariv compounds was found to be &#946;-glucoside > &#946;- galactoside > &#945;-galactoside > &#946;-mannoside. For the &#946;-glucoside compound an increase in temperature favours species of lower molecular weight, and from the enthalpy change a positive entropy change for the association is indicated. The compounds are disaggregated by concentrated solutions of urea and guanidine hydrochloride. Spectral measurements on the &#946;-glucoside compound indicate disaggregation by sodium dodecyl sulfate above the critical micelle concentration. 
