Randi M A, Mello M L
Federal University of Paraná, Department of Cell Biology-SCB, Curitiba, PR, Brazil.
Acta Histochem. 1994 Mar;96(1):81-5. doi: 10.1016/S0065-1281(11)80012-7.
Binding of toluidine blue molecules to DNA phosphates under Mg2+ competitive staining conditions and dispersion of birefringence were studied in heterochromatin and euchromatin of Malpighian tubule cells of the hemipteran, Triatoma infestans; 24 h after treatment with copper sulfate. The objective was to detect whether copper binds to chromatin DNA, affecting the critical electrolyte concentration (CEC) value and the chromatin anisotropy in these chromatin types. A decrease in CEC values as measured by metachromasy abolition, and in the concentration of Mg2+ leading to a change from anomalous dispersion of birefringence to normal dispersion of birefringence was found for the heterochromatin and euchromatin of two different nuclear types in the copper-treated material. Protein dissociation from DNA, leading to increased numbers of DNA phosphates available for dye binding, promoted by Mg2+ concentrations above that corresponding to the CEC point is suggested. Based on anisotropy findings, the binding of copper to DNA was assumed not to affect the usual molecular orientation of the DNA.
在半翅目昆虫大劣按蚊马氏管细胞的异染色质和常染色质中，研究了在Mg2+竞争染色条件下甲苯胺蓝分子与DNA磷酸盐的结合以及双折射的分散情况；在硫酸铜处理24小时后进行研究。目的是检测铜是否与染色质DNA结合，影响这些染色质类型中的临界电解质浓度（CEC）值和染色质各向异性。在经铜处理的材料中，两种不同核类型的异染色质和常染色质的CEC值（通过变色消失测量）以及Mg2+浓度降低，导致双折射从异常分散变为正常分散。提示高于对应于CEC点的Mg2+浓度会促进蛋白质与DNA解离，从而增加可用于染料结合的DNA磷酸盐数量。基于各向异性研究结果，推测铜与DNA的结合不会影响DNA通常的分子取向。
