Affinity of two novel five-coordinated anticancer Pt(II) complexes to human and bovine serum albumins: a spectroscopic approach

The interactions of two organoplatinum complexes, [Pt(C^N)Cl(dppa)], 1, and [Pt(C^N)Cl(dppm)], 2 (C^N = N(1), C(2')-chelated, deprotonated 2-phenylpyridine, dppa = bis(diphenylphosphino)amine, dppm = bis(diphenylphosphino)methane), as antitumor agents, with bovine serum albumin (BSA) and human serum albumin (HSA) have been studied by fluorescence and UV-vis absorption spectroscopic techniques at pH 7.40. The quenching constants and binding parameters (binding constants and number of binding sites) were determined by fluorescence quenching method. The obtained results revealed that there is a strong binding interaction between the ligands and proteins. The calculated thermodynamic parameters (ΔG, ΔH, and ΔS) confirmed that the binding reaction is mainly entropy-driven, and hydrophobic forces played a major role in the reaction. The displacement experiment shows that these Pt complexes can bind to the subdomain IIA (site I) of albumin. Moreover, synchronous fluorescence spectroscopy studies revealed some changes in the local polarity around the tryptophan residues. Finally, the distance, r, between donor (serum albumin) and acceptor (Pt complexes) was obtained according to F?rster theory of nonradiation energy transfer.     

The synthesis,characterization and reactions of a binuclear tetramethylplatinum(IV) complex

Reaction of excess MeLi and MeI with [PtCl₂SMe₂)₂] gives the first binuclear tetramethylplatinum(IV) complex [Pt₂Me₈(μ-SMe₂)₂]. The characterization of this complex, and its reactions with donor ligands to give cis-[PtMe₄L₂] (L₂ = Ph₂PCH₂PPh₂, Ph₂PCH₂CH₂PPh₂, 2,2′-bipyridyl, 1,10-phenanthroline or L = PMe₂Ph, PMePh₂) are described.     

Simulation of conjugate radiation–forced convection heat transfer in a porous medium using the lattice Boltzmann method

In this paper, a lattice Boltzmann method is employed to simulate the conjugate radiation–forced convection heat transfer in a porous medium. The absorbing, emitting, and scattering phenomena are fully included in the model. The effects of different parameters of a silicon carbide porous medium including porosity, pore size, conduction–radiation ratio, extinction coefficient and kinematic viscosity ratio on the temperature and velocity distributions are investigated. The convergence times of modified and regular LBMs for this problem are 15 s and 94 s, respectively, indicating a considerable reduction in the solution time through using the modified LBM. Further, the thermal plume formed behind the porous cylinder elongates as the porosity and pore size increase. This result reveals that the thermal penetration of the porous cylinder increases with increasing the porosity and pore size. Finally, the mean temperature at the channel output increases by about 22% as the extinction coefficient of fluid increases in the range of 0–0.03.

     

Series solutions for unsteady laminar MHD flow near forward stagnation point of an impulsively rotating and translating sphere in presence of buoyancy forces

The similarity solution for the unsteady laminar incompressible boundary layer flow of a viscous electrically conducting fluid in stagnation point region of an impulsively rotating and translating sphere with a magnetic field and a buoyancy force gives a system of non-linear partial differential equations. These non-linear differential equations are analytically solved by applying a newly developed method, namely the homotopy analysis method (HAM). The analytic solutions of the system of non-linear differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. Graphical results are presented to investigate the influence of the magnetic parameter, buoyancy parameter and rotation parameter on the surface shear stresses and surface heat transfer. It is noted that the behavior of the HAM solution for the surface shear stresses and surface heat transfer is in good agreement with the numerical solution given in reference [H. S. Takhar, A. J. Chamkha, G. Nath, Unsteady laminar MHD flow and heat transfer in the stagnation region of an impulsively spinning and translating sphere in the presence of buoyancy forces, Heat Mass Transfer 37 (2001) 397].     

Analytical solution of three-dimensional Navier–Stokes equations for the flow near an infinite rotating disk

In this letter, we will consider variational iteration method (VIM) and Padé approximant, for finding analytical solutions of three-dimensional viscous flow near an infinite rotating disk. The solutions is compared with the numerical (fourth-order Runge–Kutta) solution. The results illustrate that VIM–Padé is an appropriate method in solving the systems of nonlinear equations. It is predicted that VIM–Padé can have wide application in engineering problems (especially for boundary-layer and natural convection problems).     

Distance in stratified graphs

A graph G is stratified if its vertex set is partitioned into classes, called strata. If there are k strata, then G is k-stratified. These graphs were introduced to study problems in VLSI design. The strata in a stratified graph are also referred to as color classes. For a color X in a stratified graph G, the X-eccentricity e _X(v) of a vertex v of G is the distance between v and an X-colored vertex furthest from v. The minimum X-eccentricity among the vertices of G is the X-radius rad_X G of G and the maximum X-eccentricity is the X-diameter diam_X G. It is shown that for every three positive integers a, b and k with ab, there exist a k-stratified graph G with rad_X G = a and diam_X G = b. The number s _X denotes the minimum X-eccetricity among the X-colored vertices of G. It is shown that for every integer t with rad_X G t diam_X G, there exist at least one vertex v with e _X(v) = t; while if rad_X G t s _X, then there are at least two such vertices. The X-center C _X(G) is the subgraph induced by those vertices v with e _X(v) = rad_X G and the X-periphery P _X (G) is the subgraph induced by those vertices v with e _X(G) = diam_X G. It is shown that for k-stratified graphs H ₁, H ₂,..., H _k with colors X ₁, X ₂,..., X _k and a positive integer n, there exists a k-stratified graph G such that C X _i(G) H _i (1 ; i ; k1) and for i j. Those k-stratified graphs that are peripheries of k-stratified graphs are characterized. Other distance-related topics in stratified graphs are also discussed.     

Purely analytic approximate solutions for steady three-dimensional problem of condensation film on inclined rotating disk by homotopy analysis method

The similarity transform for the steady three-dimensional problem of a condensation film on an inclined rotating disk gives a system of nonlinear ordinary differential equations which are analytically solved by applying a newly developed method namely the homotopy analysis method (HAM). The analytic solutions of the system of nonlinear ordinary differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. The velocity and temperature profiles are shown and the influence of the Prandtl number on the heat transfer and the Nusselt number is discussed in detail. The validity of our results is verified by numerical results.     

Oxidative addition of methyl iodide to a new type of binuclear platinum(II) complex: a kinetic study

A new organodiplatinum(II) complex cis,cis-[Me2Pt(mu-NN)(mu-dppm)PtMe2] (1), in which NN = phthalazine and dppm = bis(diphenylphosphino)methane, is synthesized by the reaction of cis,cis-[Me2Pt(mu-SMe2)(mu-dppm)PtMe2] with 1 equiv of NN. Complex 1 has a 5d(pi)(Pt) --> pi(imine) metal-to-ligand charge-transfer band in the visible region, which was used to easily follow the kinetics of its reaction with MeI. Meanwhile, the complex contains a robust bridging dppm ligand that holds the binuclear integrity during the reaction. A double MeI oxidative addition was observed, as shown by spectrophotometry and confirmed by a low-temperature 31P NMR study. The classical S(N)2 mechanism was suggested for both steps, and the involved intermediates were suggested. Consistent with the proposed mechanism, the rates of the reactions at different temperatures were slower in benzene than in acetone and large negative deltaS values were found in each step. However, some abnormalities were observed in the related rate constants and deltaS values, which were demonstrated to be due to the associative involvement of the polar acetone molecules in the reactions. The rates are almost 6 times slower in the second step as compared to the first step because of the electronic effects transmitted through the ligands and the steric effects.     

Synthesis of Novel 2‐Oxoquinoline Derivatives via Ugi‐Four‐Component‐Heck Reaction

The present study provides an efficient strategy for the preparation of novel N‐substituted‐4‐methyl‐quinolin‐1(2H)‐one derivatives via two‐step Ugi/Heck reaction. The procedure is based on the Ugi coupling between 2‐bromoanilines, various aromatic aldehydes, vinylacetic acid, and isocyanides, and then intramolecular Heck reaction, which leads to the formation of the title compounds in good yields.