RESUMO
The interaction of bisbenzimide (Hoechst 33258) with DNA has been studied by microcalorimetry, fluorimetry and fluorescence polarization measurements. The binding does not involve intercalation, takes place in at least two modes and occurs in the major groove at low dye/DNA molar ratio (first mode of binding), in agreement with previous proposals by other Authors. Furthermore it has been shown that i) at high dye/DNA molar ratio the binding (second mode) occurs in both grooves; ii) at pH 7.0 the protonation of a dye nitrogen accompanies the binding in both modes; iii) the quantum yield of the dye-DNA complex is sensitive to the DNA conformation change caused by an increase in ionic strength. Basically the same type of binding takes place on chromatin, as detected by calorimetry. However, at high dye/DNA molar ratio about 30% of DNA is not accessible to the dye. The decreased accessibility appears to be mainly related to the nucleosomal structure of chromatin.
Assuntos
Benzimidazóis , Bisbenzimidazol , DNA , Animais , Cromatina/análise , Etídio , Técnicas In Vitro , Fígado/ultraestrutura , SuínosAssuntos
Química Encefálica/efeitos dos fármacos , Indóis/farmacologia , Triptofano Oxigenase/antagonistas & inibidores , Tirosina Transaminase/antagonistas & inibidores , Animais , Hipertensão/genética , Hipertensão/fisiopatologia , Ratos , Ratos Endogâmicos SHR/metabolismo , Serotonina/metabolismo , Triptofano/metabolismoRESUMO
XI 20.4 monoclonal antibody belongs to the IgM class. It precipitates two polypeptide chains characteristic of HLA Class I antigens. At the highest dilutions it is cytotoxic against lymphocytes carrying antigens of the HLA-A3 crossreacting group. Lysostrip experiments show that, at the lowest dilutions, the antibody reacts either with HLA-A, or B antigens.