The binding between indirubin and calf thymus DNA in vitro has been verified by meansof the isotope labelling method, spectrophotometric method and thermal denaturation meas-urements. The λ_max 207 nm of indirubin sh...The binding between indirubin and calf thymus DNA in vitro has been verified by meansof the isotope labelling method, spectrophotometric method and thermal denaturation meas-urements. The λ_max 207 nm of indirubin shifted toward longer wave length with decrease ofabsorbance after the incubation of indirubin with DNA. The escalation of Tm value of DNAinduced by indirubin was about 2.4°C and it was reproducible. The binding force between themwas rather weak, as indirubin molecules were easily released during the precipitation withalcohol or the gel filtration. The binding was not affected by sodium chloride even at high con-centration but greatly decreased (to 20-30% of the control) in the presence of 8 M urea.These results showed that the binding between indirubin and DNA might be of hydrogen bondrather than ionic. The amount of bound ~3H-indirubin was directly proportional to the con-centration of indirubin. However, it increased abruptly when the concentration of indirubinreached 1.5×10^(-4) M. This suggested another binding force in the latter instance. By using spectrophotometric analysis and Scatchard plot it was found that calf thymusDNA bound 46 indirubin molecules/1000 nucleotides. The association constant (K) was5.7×10~6.展开更多
文摘The binding between indirubin and calf thymus DNA in vitro has been verified by meansof the isotope labelling method, spectrophotometric method and thermal denaturation meas-urements. The λ_max 207 nm of indirubin shifted toward longer wave length with decrease ofabsorbance after the incubation of indirubin with DNA. The escalation of Tm value of DNAinduced by indirubin was about 2.4°C and it was reproducible. The binding force between themwas rather weak, as indirubin molecules were easily released during the precipitation withalcohol or the gel filtration. The binding was not affected by sodium chloride even at high con-centration but greatly decreased (to 20-30% of the control) in the presence of 8 M urea.These results showed that the binding between indirubin and DNA might be of hydrogen bondrather than ionic. The amount of bound ~3H-indirubin was directly proportional to the con-centration of indirubin. However, it increased abruptly when the concentration of indirubinreached 1.5×10^(-4) M. This suggested another binding force in the latter instance. By using spectrophotometric analysis and Scatchard plot it was found that calf thymusDNA bound 46 indirubin molecules/1000 nucleotides. The association constant (K) was5.7×10~6.
