Reduction Process of Tetraplatin in the Presence of Deoxyguanosine Monophosphate (dGMP): A Computational DFT Study

In-vitro cytotoxicity and in-vivo antitumor activity of two platinum complexes with 1,3-dimethyl pentyl glycine ligand against breast cancer

Platinum (Pt) derivatives are good candidates for discovering new anti-tumor agents. The present research aims to explore the in-vivo and in-vitro anticancer activity of two platinum complexes with 1,3-dimethyl pentyl glycine ligand (DMPG), [Pt(bpy)(13DMPG)]NO₃ and [Pt(dach)(13DMPG)]NO₃, against breast cancer cells. The present study was conducted to investigate the cytotoxic potential of these compounds (2-400 μM) compared to standard drugs (cisplatin, oxaliplatin, and carboplatin) on SKBR3 cells using the methyl thiazol-tetrazolium (MTT) assay. Furthermore, the gene expression changes of Bak, Bim, Bcl-2, Caspase-3, and Caspase-9 were carried out by real-time polymerase chain reaction (PCR), and flow cytometric analysis was performed to confirm the cell apoptosis in the presence of the compounds. For more validation, in-vivo anticancer activities of both compounds were investigated against breast transplanted tumors in the BALB/c mice model. The cytotoxic studies by MTT assay revealed the anti-proliferative potential of both derivatives. [Pt(dach)(13DMPG)]NO₃ with an IC₅₀ value of 15 μM, exhibited higher cytotoxicity against SKBR3 cells as compared to [Pt(bpy)(13DMPG)]NO₃, oxaliplatin, and carboplatin. Based on the flow cytometry analysis, both derivatives demonstrated apoptotic effects. Also, real-time PCR analysis revealed an up-regulation of Bak, Bim, Bax, Caspases-3, and Caspase-9 genes and a significant reduction in Bcl-2 gene expression in treated cells with both compounds compared to the control group. In-vivo results validated in-vitro analysis and showed the anticancer activity of compounds against breast transplanted tumors in the BALB/c mice model. According to the results, [Pt(dach)(13DMPG)]NO₃ displayed a significant anticancer activity.

QM and QM/MM umbrella sampling MD study of the formation of Hg(II)-thymine bond: Model for evaluation of the reaction energy profiles in solutions with constant pH

The formation of the Hg-N3(T) bond between the 1-methylthymine (T) molecule and the hydrated Hg²⁺ cation was explored with the combined quantum mechanics/molecular mechanics (QM/MM) method including Free Energy Perturbation corrections. The thermodynamic properties were determined in the whole pH range, when these systems were explicitly investigated and considered as the QM part: (1) T + [Hg(H₂ O)₆ ]²⁺ , (2) T + [Hg(H₂ O)₅ (OH)]⁺ , (3) T + Hg(H₂ O)₄ (OH)₂ , and (4) N3-deprotonated T + Hg(H₂ O)₄ (OH)₂ . The MM part contained only solvent molecules and counterions. As a result, the dependence of Gibbs-Alberty reaction free energy on pH was obtained along the reaction coordinate. We found that an endoergic reaction in acidic condition up to pH < 4-5 becomes exoergic for a higher pH corresponding to neutral and basic solutions. The migration of the Hg²⁺ cation between N3 and O4/2 positions in dependence on pH is discussed as well. For the verification, DFT calculations of stationary points were performed confirming the qualitative trends of QM/MM MD simulations and NMR parameters were determined for them.

Exploring the Hydrolytic Behavior of the Platinum(IV) Complexes with Axial Acetato Ligands

Platinum(IV) complexes are generally thought to be kinetically inert, and are expected to be stable enough to resist premature aquation before entering the cancer cells. Nevertheless, in this work, complex 2 with axial acetato ligands can hydrolyze relatively quickly under biologically relevant conditions with a half-life of 91.7 min, resulting in the loss of the equatorial chlorido ligand. Further study indicated that the fast hydrolysis of complex 2 may be attributed to the strong σ-donor ability of N-isopropyl-1R,2R-diaminocyclohexane, and an increasing σ-donor ability of the amine group can promote the hydrolysis rate of the corresponding platinum(IV) complex. The experiment results were proven by the corresponding DFT calculation. Our study can help to re-evaluate the aqueous properties of the platinum(IV) complexes with axial acetate, which may be less inert to hydrolysis than expected under biologically relevant conditions.

Side Reactions with an Equilibrium Constraint: Detailed Mechanism of the Substitution Reaction of Tetraplatin with dGMP as a Starting Step of the Platinum(IV) Reduction Process

Two possible pathways of the substitution reaction within the reduction process of the Pt^IV(DACH)Cl₄ by dGMP are compared: associative reaction course and autocatalytic Basolo-Pearson mechanisms. Since two forms: single-protonated and fully deprotonated phosphate group of dGMP are present in equilibrium at neutral and mildly acidic solutions, consideration of a side reactions scheme with acido-basic equilibrium-constraint is a very important model for obtaining reliable results. The examined complexes are optimized at the B3LYP-GD3BJ/6-31G(d) level with the COSMO implicit solvation model and Klamt's radii used for cavity construction. Energy characteristics and thermodynamics for all reaction branches are determined using the B3LYP-GD3BJ/6-311++G(2df,2pd)/IEF-PCM/scaled-UAKS level with Wertz's entropy corrections. Rate constants are estimated for each individual branch according to Eyring's transition state theory (TST), averaged according to equilibrium constraint and compared with available experimental data. The determined reaction barriers of the autocatalytic pathway fairly correspond with experimental values. Furthermore, autocatalytic reaction of tetraplatin and its two analogues complexes [Pt^IV(en)Cl₄ and Pt^IV(NH₃)₂Cl₄] are explored and compared with measured data in order to examined general reaction descriptors.

Reduction of ormaplatin and cis-diamminetetrachloroplatinum(iv) by ascorbic acid and dominant thiols in human plasma: kinetic and mechanistic analyses

The reductions of Pt(iv) anticancer prodrugs [Pt(dach)Cl₄] (ormaplatin/tetraplatin) and cis-[Pt(NH₃)₂Cl₄] by several dominant reductants in human plasma have been characterized and analyzed kinetically and mechanistically.