Open AccessThe Interactions of 2‐Thiopyrimidine Bases with Hydroxymercurybenzene Sulfonate
Author(s) -
Scheit KarlHeinz,
Faerber Peter
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb02714.x
Subject(s) - sulfonate , titration , scatchard plot , dissociation constant , chemistry , titration curve , dissociation (chemistry) , absorption spectroscopy , stereochemistry , crystallography , equilibrium constant , binding site , organic chemistry , sodium , receptor , biochemistry , physics , quantum mechanics
The interaction of hydroxymercurybenzene sulfonate (HOHgBzS) with 2‐thiouridine (s 2 Urd) and 2‐thiocytidine (s 2 Cyd) by means of absorption‐difference spectroscopy and spectrophotometric titration was investigated. The absorption spectra of the reaction mixtures displayed isosbestic points indicating uniform reactions. Scatchard plots of the titration data revealed the formation of 1:1 complexes with a dissociation constant for s 2 Urd · HOHgBzS and s 2 Cyd · HOHgBzS of K d = 0.55 μM and K d = 0.54 μM, respectively. The interactions of poly(s 2 U) and poly(s 2 c) with hydroxymercurybenzene sulfonate were established by their corresponding absorption difference spectra. The binding of hydroxymercurybenzoate (HOHgBz) to poly(s 2 C) and poly(s 2 U) was investigated by means of equilibrium dialysis. The association of HOHgBz to 2‐thiocytosine bases in poly(s 2 C) follows a simple hyperbolic binding isotherm. The Scatchard plot of the binding data disclosed that only a fraction ( n = 0.32) of the s 2 CMP residues in poly(s 2 C) was accessible to the interaction with HOHgBz. The dissociation constant of this interaction was found to be K d = 4.3 μM. The binding of HOHgBz to the helical poly(s 2 U) is a cooperative process as indicated by the sigmoidal binding cuve. Under saturating conditions all s 2 UMP residues in poly(s 2 U) interact with the ligand.