Hydration process as an activation of trans- and cisplatin complexes in anticancer treatment. DFT and ab initio computational study of thermodynamic and kinetic parameters

The thermodynamic and kinetic aspects of hydration reactions of cis-/transplatin were explored. The polarizable continuum model was used for estimation of solvent effects. Using the B3LYP/6-31+G(d) method, the structures were optimized and vibrational frequencies estimated. Interaction energies and activation barriers were determined at the CCSD(T)/6-31++G(d,p) level within the COSMO approach. An associative mechanism was assumed with a trigonal-bipyramidal structure of the transition state. Within the applied model, all the hydration reactions are slightly endothermic. The Gibbs energies of cisplatin hydration amount to 7.0 and 14.2 kcal/mol for the chloride and ammonium replacement, respectively. Analogous values for the transplatin reactions are 6.8 and 11.9 kcal/mol. The determined rate constants are by several (three to four) orders of magnitude larger for the dechlorination process than for deammination. The cisplatin dechlorination rate constant was established as 1.3 x 10(-4) s(-1) in excellent accord with the experiment.     

One-electron reduction of an "extended viologen" p-phenylene-bis-4,4'-(1-aryl-2,6-diphenylpyridinium) dication

One-electron reduction of the "extended viologen" dication 1 yields the red cation radical 2, characterized by strong near-IR absorption. It has been generated and studied by pulse radiolytic, electrochemical, redox titration, UV-visible, and electron paramagnetic resonance spectroscopic methods. All results are in agreement with a fully delocalized electronic structure for 2.     

Cooperative h-bonds of macromolecules. 1. Binding of low-molecular-weight ligands to polymers

Equilibrium bindings of two low-molecular-weight hydrogen bond acceptor ligands, tetrahydrofuran (THF) and pyridine (PH), and their fully deuterated analogues (TDF, PD) with poly(4-vinylphenol) (PVF) and its low-molecular-weight model, a hydrogen bond donor 4-isopropylphenol (IPP), were studied using spectroscopic (NMR) and theoretical (ab initio SCF-DFT B3LYP/6-31G(d)) methods as a first step of a general study of cooperative hydrogen bonding of H-bond-donating and -accepting macromolecules. Two reliable experimental methods of measuring the fraction of H-bonded or free ligands, which can be used as an indirect tool in further studies of macromolecular cooperative binding, were devised and examined in this study. The methods are complementary and independent. They are based on one hand on (2)H quadrupolar or (1)H longitudinal NMR relaxation and, on the other hand, on (2)H or (1)H PFG NMR self-diffusion measurement, using the pulsed-field-gradient spin-echo (PGSE) and pulsed-field-gradient stimulated echo (PGSTE) methods. It was shown that both the relaxation and PFG methods need viscosity correction using as an internal standard a relatively inert compound of a relaxation/diffusion rate similar to that of the internal standard (CDCl(3) or HMDSO in the present case). After such normalization, the reliability of both methods was checked by calculating the equilibrium constants K of binding under a variety of ligand/donor ratios beta. Excepting the rather impractical region of low beta values, where cooperative self-association of the H-donating polymer takes place, both methods were found to be reasonably reliable. A slight anomaly in the relaxation behavior of pyridine and its stronger-than-expected binding to PVF was plausibly explained (using high-precision quantum mechanical calculations) by additional formation of weak C-H...O bonds to the neighboring units.     

Growth and characterization of pulsed laser deposited ZnO thin films

One of the most important and promising materials from metal oxides is ZnO with specific properties for near UV emission and absorption optical devices. The properties of ZnO thin films strongly depend on the deposition method. Among them, pulsed laser deposition (PLD) plays an important role for preparing various kinds of ZnO films, e.g. doped, undoped, monocrystalline, and polycrystalline. Different approaches — ablation of sintered ZnO pellets or pure metallic Zn as target material are described. This contribution is comparing properties of ZnO thin films deposited from pure Zn target in oxygen atmosphere and those deposited from sintered ZnO target. There is a close connection between final thin film properties and PLD conditions. The surface properties of differently grown ZnO thin films are measured by secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Furthermore, different approaches — ablation of sintered ZnO pellet or pure metallic Zn as target materials are described. The main results characterize typical properties of ZnO films versus technological parameters are presented. Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia     

A Note on Maxflow-Mincut and Homomorphic Equivalence in Matroids

Graph homomorphisms are used to study good characterizations for coloring problems Trans. Amer. Math. Soc. 384 (1996), 1281–1297; Discrete Math. 22 (1978), 287–300). Particularly, the following concept arises in this context: A pair of graphs (A, B) is called a homomorphism duality if for any graph G either there exists a homomorphism : A G or there exists a homomorphism : G B but not both. In this paper we show that maxflow-mincut duality for matroids can be put into this framework using strong maps as homomorphisms. More precisely, we show that, if C _k denotes the circuit of length k + 1, the pairs (C _k , C _{k + 1}) are the only homomorphism dualities in the class of duals of matroids with the strong integer maxflow-mincut property (Jour. Comb. Theor. Ser.B 23 (1977), 189–222). Furthermore, we prove that for general matroids there is only a trivial homomorphism duality.     

Zur Bestimmung von 4-Butyl-1,2-diphenylpyrazolidin-3,5-dion

Ohne Zusammenfassung     

Die chelatometrische Bestimmung von Natriumglutamat in Injektions-l?sungen

Ohne Zusammenfassung     

N-substituierte Phenothiazinderivate

Ohne Zusammenfassung