Similar positive LD signals were observed for the Zn(bpy)2 and Cd(bpy)2 complexes at the time of mixing (Fig. S3). Therefore, the possibility of ligand intercalation between the DNA base-pairs can be rejected. With
time, the magnitude of the LD spectrum decreased gradually and the signal was almost diminished 20 min after mixing, suggesting that dsDNA became so flexible and shortened that it could not be oriented in the flow. Fig. 5 shows the decrease in LD intensity at 260 nm as a function of time. Although the LD intensity at 260 nm of the dsDNA-Cu(bpy)2 Sunitinib mw adduct decreased gradually with time, reaching a zero magnitude within 20 min, that of the dsDNA-Zn(bpy)2 and dsDNA-Cd(Bpy)2 adduct remained almost constant (curves b and c), indicating that the flexibility and length of DNA are unaffected by the presence of either Zn(bpy)2 or Cd(bpy)2. This suggests that, in addition to the cleavage of scDNA probed by electrophoresis, the latter two metal complexes were unable to cleave the DNA. The decrease in LD intensity at 260 nm in the presence of the Cu(bpy)2 complex cannot be explained by simple first or second order kinetics as it was evaluated by the residuals. The residual from single component exponential decay is shown in the lower panel as an example. The sum of the two first order kinetics which corresponds to the sum of two exponential curves, LD(t)=a1exp(−t/τ1)+a2exp(−t/τ2)LDt=a1exp−t/τ1+a2exp−t/τ2were
this website the best to elucidate the decay of the LD signal. The decay curve analysis for the dsDNA-Cu(bpy)2 adduct is shown in Fig. 5. The goodness of fit was evaluated by the residuals. As observed from the residuals (Fig. 5, low panel), the decay curve of the dsDNA-Cu(bpy)2 adduct consisted of two exponential
components, i.e., τ1 = 1.42 and τ2 = 7.16 min, the mean of the three measurements, with their relative amplitude of a1 = 0.324 and a2 = 0.676, respectively. The relevant reaction times τ1 and τ2 correspond to the rate constant of the first order reactions k1 = 0.71 min− 1 and k2 = 0.14 min− 1, respectively. As observed for scDNA, various ROS may affect the efficiency of the cleavage of dsDNA. Fig. 6 shows the effect of ROS scavengers on the decreasing profile of the LD signal of the dsDNA-Cu(bpy)2 adduct. At a glance, it is clear that the presence of tiron drastically suppresses the Vasopressin Receptor cleavage (curve e, Fig. 6). The catalase also had a large inhibition effect (curve d, Fig. 6). The two component curve fitting resulted in τ1 = 1.22 and τ2 = 16.66 min with their relative amplitude of a1 = 0.298 and a2 = 0.702, respectively. The two reaction time correspond to the two first order reaction constants, k1 = 0.82 min− 1 and k2 = 0.060 min− 1, respectively. Sodium azide had an intermediate inhibitory effect on dsDNA cleavage. The reaction times, τ1 = 1.45 (a1 = 0.231) and τ2 = 10.59 min (a2 = 0.769), were obtained from that fit. The inhibitory effect of DMSO was the weakest.