Synthesis, characterization, DFT studies and DNA binding of mixed platinum (II) complexes containing quinoxaline and 1,2-dithiolate ligands

The complexes Pt(pq)Cl2(1) and Pt(pq)(bdt) (2) (where pq = 2-(2'pyridyl)quinoxaline and bdt=benzene-1,2-dithiolate) have been synthesized and fully characterized by UV-visible (UV-Vis), Fourier Transformer Infrared Spectra (FTIR), 1 and 2D NMR and cyclic voltammetry (CV). Interactions of the tested systems (the aforementioned complexes 1 and 2) and the free ligands pq and bdt with double stranded calf thymus DNA (CT-DNA) were studied by UV-spectrophotometric (melting curves) and circular dichroism (CD) measurements. The results suggest that both complexes 1 and 2, are able to form adducts with DNA and to distort the double helix by changing the base stacking. Complex 2 forms stronger adducts to CT-DNA than complex 1 and this is probably due to the substitution of the chlorine atoms of 1 by the 1,2-dithiolate ligand (bdt) in 2. The latter induces an extensive distortion in the planarity of 2 as density functional theory (DFT) calculations reveal. Besides, the light absorbing complex 2 possess intense mixed metal ligand to ligand charge transfer (MM'LLCT) transition in the visible region of the spectrum and could act as photoluminescent metal-based probe for the study of DNA binding. Thus, the photocleavage of DNA by 2 has been studied by UV-Vis and CD spectra and monitored by agarose gel electrophoresis. Under our experimental conditions, it is unclear that complex 2 can photocleave DNA. Furthermore, the ability of 2 to inhibit proliferation of human tumor cell lines was tested and the results indicate some cytoxytic effect on the SF-286 cells.     

St. John's wort (Hypericum perforatum) counteracts cytokine-induced tryptophan catabolism in vitro

St. John's wort (Hypericum perforatum) is an ancient folk remedy that has antiviral and antibacterial properties. Anti-inflammatory effects of the plant have been described and the application of H. perforatum extract as an effective antidepressant is well established. In this study we assayed the effect of H. perforatum extract on cytokine-induced tryptophan degradation in human peripheral blood mononuclear cells. Simultaneously, changes in the production of the immune activation marker neopterin were monitored. Both these biochemical pathways are triggered by interferon-gamma. Our results show that extracts of H. perforatum strongly down-regulate mitogen-mediated tryptophan degradation in a dose-dependent manner. This effect seems to be based on a suppressive activity of H. perforatum on activated immunocompetent cells, resulting in a diminished production of interferon-gamma. In line with this finding, neopterin synthesis was strongly down-regulated by the plant extract. Our results suggest that the reduction of tryptophan degradation by H. perforatum might be important in the action of the plant as an antidepressant.     

Kinetic analysis of the binding of hemopexin-like domain of gelatinase B cloned and expressed in Pichia pastoris to tissue inhibitor of metalloproteinases-1

The gelatinases are a subgroup of the matrix metalloproteinase family. The interaction of their C-terminal hemopexin-like domain with a tissue inhibitor of metalloproteinases (TIMP) is a major part of the regulatory mechanisms of gelatinases. To investigate the interaction of the hemopexin-like domain of gelatinase B (92-Pex) and TIMP-1, we expressed the individual domain in Pichia pastoris. The active refolded domain was purified by ion exchange chromatography and gel filtration. We investigated the formation of the 92-Pex/TIMP-1 complex by surface plasmon resonance (SPR). The dissociation constant Kd was calculated to be 0.86 nM. Analogous to the complex of the hemopexin-like domain of gelatinase A and TIMP-2 (Olson, M. W. et al., 1997), the binding curves of the 92-Pex/TIMP-1 complex were best fitted with a monophasic model.     

4,5-Disubstituted cis-pyrrolidinones as inhibitors of type II 17beta-hydroxysteroid dehydrogenase. Part 2. SAR

4,5-Disubstituted cis-pyrrolidinones were investigated as inhibitors of type II 17beta-hydroxysteroid dehydrogenase (17beta-HSD). Early structure-activity relationship patterns for this class of compounds are discussed.     

Modular flexibility of dystrophin: implications for gene therapy of Duchenne muscular dystrophy

Attempts to develop gene therapy for Duchenne muscular dystrophy (DMD) have been complicated by the enormous size of the dystrophin gene. We have performed a detailed functional analysis of dystrophin structural domains and show that multiple regions of the protein can be deleted in various combinations to generate highly functional mini- and micro-dystrophins. Studies in transgenic mdx mice, a model for DMD, reveal that a wide variety of functional characteristics of dystrophy are prevented by some of these truncated dystrophins. Muscles expressing the smallest dystrophins are fully protected against damage caused by muscle activity and are not morphologically different from normal muscle. Moreover, injection of adeno-associated viruses carrying micro-dystrophins into dystrophic muscles of immunocompetent mdx mice results in a striking reversal of histopathological features of this disease. These results demonstrate that the dystrophic pathology can be both prevented and reversed by gene therapy using micro-dystrophins.     

Rapid microwave fixation--a comparative morphometric study

Summary Tissue blocks taken from healthy human lung tisues, from primary bronchial carcinoma and from mediastinal and hilar lymph nodes were placed in the following solutions. Tris buffer; buffered formalin (0.5%, 1%, 7%); 0.1 mol NaCl; distilled water; DMSO (1%, 10%, 20%); acetone (10%); methanol (50%, 80%, 100%); glutaraldehyde (2.5%), and fixed by use of a commercial microwave oven.Tissue blocks obtained from the same surgical specimens were fixed in 7% buffered formalin for 24 h for comparison. Conventional and microwave-fixed tissue was embedded in paraffin, and stained with haematoxylin and eosin. Fifteen specimens of each group and each solution were examined by light microscopy. Minimum diameter and area of 100 nuclei of each specimen were measured interactively.Histomorphological sections fixed with Tris buffer in a microwave oven revealed best morphological results showing more contrast in chromatin distribution of nuclei and opening of interstitial lung capillaries in comparison to conventional formalin-fixed specimens. No statistically significant differences in area and minimum diameter of nuclei between the different groups were found. Microwave fixation using Tris buffer is a time-saving fixation method at least comparable to conventional formalin fixation. It is not accompanied by hazards to the environment that are unavoidable by formalin fixation.