Spectroscopic studies of amphotericin B–Cu<Superscript>2+</Superscript> complexes

The aim of this research is to investigate amphotericin B (AmB)–Cu²⁺ complexes in aqueous solution at different pH values. Electronic absorption, circular dichroism (CD), Raman and FTIR spectroscopies were used in this study. We found that different concentrations of AmB and Cu²⁺ ions in solution leads to formation of complexes with stoichiometry of 2:1 and 1:1. The formation of AmB–Cu²⁺ complexes at physiological pH values is accompanied by changes of the molecular organization of AmB especially disaggregation. These observed effects might be significant from a medical point of view.     

Do secondary sexual dimorphism and female intolerance to drought influence the sex ratio and extinction risk of <Emphasis Type="Italic">Taxus baccata</Emphasis>?

Sex ratio and sexual dimorphism were studied in the dioecious tree Taxus baccata. We examined five populations of T. baccata in Poland and Ukraine to identify the differences between male and female individuals. The sex of all individuals, height and diameter, needle length and area, specific leaf area (SLA), the number of stomata rows, stomatal density, and content of carbon and nitrogen were measured to identify the differences between male and female individuals. The relationship between sex ratio and climatic conditions, age and population size were analysed using data collected from the field and the literature. Female trees were shorter than males, but needles of females were longer and had larger area. Although there were no differences among sexes in SLA, nitrogen and carbon concentration, we found a positive correlation between nitrogen concentration and SLA among females. The sex ratio changed with tree height within populations, and taller height classes were biased in favour of males. Regardless of population age, the percentage of females within populations was positively correlated with precipitation. Probably high reproductive effort caused female trees to lose in competition with males, and this loss may also be enhanced by lower drought tolerance in females and could contribute to risk of extinction for T. baccata. The continental geographic range of T. baccata may be restricted by limited occurrence of females, which demand higher water resources than males.     

A benzimidazole-based ruthenium(IV) complex inhibits Pseudomonas aeruginosa biofilm formation by interacting with siderophores and the cell envelope,and inducing oxidative stress

Pseudomonas aeruginosa biofilm-associated infections are a serious medical problem, and new compounds and therapies acting through novel mechanisms are much needed. Herein, the authors report a ruthenium(IV) complex that reduces P. aeruginosa PAO1 biofilm formation by 84%, and alters biofilm morphology and the living-to-dead cell ratio at 1?mM concentration. Including the compound in the culture medium altered the pigments secreted by PAO1, and fluorescence spectra revealed a decrease in pyoverdine. Scanning electron microscopy showed that the ruthenium complex did not penetrate the bacterial cell wall, but accumulated on external cell structures. Fluorescence quenching experiments indicated strong binding of the ruthenium complex to both plasmid DNA and bovine serum albumin. Formamidopyrimidine DNA N-glycosylase (Fpg) protein digestion of plasmid DNA isolated after ruthenium(IV) complex treatment revealed the generation of oxidative stress, which was further proved by the observed upregulation of catalase and superoxide dismutase gene expression.     

Oxidation of excited-state NADH and NAD dimer in aqueous medium involvement of O2− as a mediator in the presence of oxygen

It has been shown that direct excitation of NADH (or NADPH) in aqueous medium at 254 nm, or at wavelengths longer than 320 nm (where only the reduced nicotinamide moiety absorbs), leads to generation of NAD⁺ (or NADP⁺). The reaction proceeds both in the presence and absence of oxygen. Under aerobic conditions the reaction is accompanied by formation of H₂O₂ at a level equimolar with that of the NADH present in solution. On irradiation at wavelengths longer than 320 nm, conversion of NADH to enzymatically active NAD⁺ is about 75%. Under analogous irradiation conditions, the dimers (NAD)₂ and (NADP)₂ undergo disproportionation to NAD⁺ and NADP⁺, respectively, to the extent of 90%. Both physicochemical and enzymatic criteria were employed to formulate mechanisms for the photooxidation of NADH and the photodisproportionation of the dimer (NAD)₂.