Synthesis, structure and photophysical properties of a flavin-based platinum(II) complex

Modulating catalytic activity of a modified flavin analogue via judicially positioned metal ion toward aerobic sulphoxidation

This manuscript describes the synthesis, spectroscopic and crystallographic characterization of a cadmium complex of 10-propoylisoalloxazine-7-carboxylic acid (Flc-Cd). Catalytic activity of Flc-Cd towards aerobic sulphoxidation reaction was investigated in the presence of l-ascorbic acid as the reducing agent. Notably the neutral un-metalated flavin analogue did not show any significant catalytic activity. The design strategy for Flc provides a close proximity of the metal centre to the flavin core without compromising the catalytic site thereby assisting the product formation when compared to unmetallated Flc. Minor enantioselectivity is also observed in cases where unsymmetrical sulphides were used; indicative of the possible involvement of chiral l-ascorbic acid in the intermediate formation.

Design and synthesis of a catalytically efficient metal-flavin complex toward aerobic sulphoxidation was achieved via judicially positioning the metal ion near the catalytic site thereby assisting the intermediate formation.

Interaction of classical platinum agents with the monomeric and dimeric Atox1 proteins: a molecular dynamics simulation study

We carried out molecular dynamics simulations and free energy calculations for a series of binary and ternary models of the cisplatin, transplatin and oxaliplatin agents binding to a monomeric Atox1 protein and a dimeric Atox1 protein to investigate their interaction mechanisms. All three platinum agents could respectively combine with the monomeric Atox1 protein and the dimeric Atox1 protein to form a stable binary and ternary complex due to the covalent interaction of the platinum center with the Atox1 protein. The results suggested that the extra interaction from the oxaliplatin ligand-Atox1 protein interface increases its affinity only for the OxaliPt + Atox1 model. The binding of the oxaliplatin agent to the Atox1 protein might cause larger deformation of the protein than those of the cisplatin and transplatin agents due to the larger size of the oxaliplatin ligand. However, the extra interactions to facilitate the stabilities of the ternary CisPt + 2Atox1 and OxaliPt + 2Atox1 models come from the α1 helices and α2-β4 loops of the Atox1 protein-Atox1 protein interface due to the cis conformation of the platinum agents. The combinations of two Atox1 proteins in an asymmetric way in the three ternary models were analyzed. These investigations might provide detailed information for understanding the interaction mechanism of the platinum agents binding to the Atox1 protein in the cytoplasm.

Disturbance of DNA conformation by the binding of testosterone-based platinum drugs via groove-face and intercalative interactions: a molecular dynamics simulation study

BACKGROUND

To explore novel platinum-based anticancer agents that are distinct from the structure and interaction mode of the traditional cisplatin by forming the bifunctional intrastrand 1,2 GpG adduct, the monofunctional platinum+DNA adducts with extensive non-covalent interactions had been studied. It was reported that the monofunctional testosterone-based platinum(II) agents present the high anticancer activity. Moreover, it was also found that the testosterone-based platinum agents could cause the DNA helix to undergo significant unwinding and bending over the non-testosterone-based platinum agents. However, the interaction mechanisms of these platinum agents with DNA at the atomic level are not yet clear so far.

RESULTS

In the present work, we used molecular dynamics (MD) simulations and DNA conformational dynamics calculations to study the DNA distortion properties of the testosterone-based platinum+DNA, the improved testosterone-based platinum+DNA and the non-testosterone-based platinum+DNA adducts. The results show that the intercalative interaction of the improved flexible testosterone-based platinum agent with DNA molecule could cause larger DNA conformational distortion than the groove-face interaction of the rigid testosterone-based platinum agent with DNA molecule. Further investigations for the non-testosterone-based platinum agent reveal the occurrence of insignificant change of DNA conformation due to the absence of testosterone ligand in such agent. Based on the DNA dynamics analysis, the DNA base motions relating to DNA groove parameter changes and hydrogen bond destruction of DNA base pairs were also discussed in this work.

CONCLUSIONS

The flexible linker in the improved testosterone-based platinum agent causes an intercalative interaction with DNA in the improved testosterone-based platinum+DNA adduct, which is different from the groove-face interaction caused by a rigid linker in the testosterone-based platinum agent. The present investigations provide useful information of DNA conformation affected by a testosterone-based platinum complex at the atomic level.