Binding of cationic surfactants to DNA, protein and DNA-protein mixtures.

Extent of binding (gamma 2(1)) of cationic surfactants cetyltrimethyl ammonium bromide (CTAB), myristyltrimethyl ammonium bromide (MTAB) and dodecyl trimethyl ammonium bromide (DTAB) to calf-thymus DNA, bovine serum albumin (BSA) and to their binary mixture respectively have been measured as function of bulk concentration of the surfactant by using equilibrium dialysis technique. Binding of CTAB has been studied at different pH, ionic strength (mu), temperature and biopolymer composition and with native and denatured states of the biopolymers. The chain-length of different long chain amines plays a significant role in the extent of binding under identical solution condition. The binding ratios for CTAB to collagen, gelatin, DNA-collagen and DNA-gelatin mixtures respectively have also been determined. The conformational structures of different biopolymers are observed to play significant role in macromolecular interactions between protein and DNA in the presence of CTAB. From the experimental values of the maximum binding ratio (gamma 2m) at the saturation level for each individual biopolymer, ideal values (gamma 2m)id have been theoretically calculated for binary mixtures of biopolymers using additivity rule. The protein-DNA-CTAB interaction in mixture has been explained in terms of the deviation (delta) of (gamma 2m) from (gamma 2m)id in the presence of a surfactant in bulk. The binding of surfactants to biopolymers and to their binary mixtures are compared more precisely in terms of the Gibbs' free energy decrease (-delta G degree) for the saturation of the binding sites in the biopolymers or biopolymer mixtures with the change of the bulk surfactant activity from zero to unity in the rational mole fraction scale.

Solubilization and binding of DNA-CTAB complex with SDS in aqueous media.

Extent of binding (gamma 2(1)) of sodium dodecyl sulphate (SDS) to the binary complex formed between calfthymus DNA and cetyltrimethylammonium bromide (CTAB) has been measured in mole per mole of nucleotide in the complex as function of concentration of SDS by using equilibrium dialysis technique at different temperatures and pH. Binding of SDS to thermally denatured DNA-CTAB complex has also been studied. The most interesting aspect to be noted in this experiment is that the water insoluble DNA-CTAB binary complex gets solubilized in the ternary mixture in presence of SDS but when DNA is thermally denatured, the ternary system DNA-CTAB-SDS remains insoluble. Significant change in the extent of binding has been noted with the variation of the relative composition of DNA and CTAB in their binary mixture. The data of binding of SDS to DNA-CTAB complex are compared more precisely in terms of the standard Gibbs' free energy decrease (-delta G degree) for the saturation of the binding sites in the complex with the change of SDS activity from zero to unity in the rational mole fraction scale.

Potential roles of osteopontin and alphaVbeta3 integrin in the development of coronary artery restenosis after angioplasty.

Angioplasty procedures are increasingly used to reestablish blood flow in blocked atherosclerotic coronary arteries. A serious complication of these procedures is reocclusion (restenosis), which occurs in 30-50% of patients. Migration of coronary artery smooth muscle cells (CASMCs) to the site of injury caused by angioplasty and subsequent proliferation are suggested mechanisms of reocclusion. Using both cultured human CASMCs and coronary atherectomy tissues, we studied the roles of osteopontin (OPN) and one of its receptors, alphavbeta3 integrin, in the pathogenesis of coronary restenosis. We also measured the plasma levels of OPN before and after angioplasty and determined the effect of exogenous OPN on CASMC migration, extracellular matrix invasion, and proliferation. We found that cultured CASMCs during log phase of growth and smooth muscle cell layer of the coronary atherosclerotic tissues of patients express both OPN mRNA and protein at a significantly elevated level compared with controls. Interestingly, whereas the baseline plasma OPN levels in control samples were virtually undetectable, those in patient plasma were remarkably high. We also found that interaction of OPN with alphavbeta3 integrin, expressed on CASMCs, causes migration, extracellular matrix invasion, and proliferation. These effects were abolished when OPN or alphavbeta3 integrin gene expression in CASMCs was inhibited by specific antisense S-oligonucleotide treatment or OPN-alphavbeta3 interaction was blocked by treatment of CASMCs with antibodies against OPN or alphavbeta3 integrin. Our results demonstrate that OPN and alphavbeta3 integrin play critical roles in regulating cellular functions deemed essential for restenosis. In addition, these results raise the possibility that transient inhibition of OPN gene expression or blocking of OPN-alphavbeta3 interaction may provide a therapeutic approach to preventing restenosis.

Suppression of epididymal sperm antigenicity in the rabbit by uteroglobin and transglutaminase in vitro.

There is evidence that the mammalian female genital tract is capable of responding immunologically when challenged with alloantigens. The antigenic properties of male gametes have been well delineated. However, it is only rarely that a female mammal ever responds immunologically to the male gametic antigens as a result of coitus. When a proposed mechanism of suppression of antigenicity of epididymal spermatozoa was tested experimentally, the results indicated that two proteins (uteroglobin and transglutaminase) present in the prostate may be responsible for suppressing sperm antigenicity in the rabbit.