Conformational stability and dynamics of cytochrome <Emphasis Type="Italic">c</Emphasis> affect its alkaline isomerization

The alkaline isomerization of horse heart ferricytochrome c (cyt c) has been studied by electronic absorption spectroscopy in the presence of the Hofmeister series of anions: chloride, bromide, rhodanide and perchlorate. The anions significantly affect the apparent pK _a value of the transition in a concentration-dependent manner according to their position in the Hofmeister series. The Soret region of the absorption spectra is not affected by the presence of the salts and shows no significant structural perturbation of the heme crevice. In the presence of perchlorate and rhodanide anions, the cyanide exchange rate between the bulk solvent and the binding site is increased. These results imply higher flexibility of the protein structure in the presence of chaotropic salts. The thermal and isothermal denaturations monitored by differential scanning calorimetry and circular dichroism, respectively, showed a decrease in the conformational stability of cyt c in the presence of the chaotropic salts. A positive correlation between the stability, ΔG, of cyt c and the apparent pK _a values that characterize the alkaline transition indicates the presence of a thermodynamic linkage between these conformational transitions. In addition, the rate constant of the cyanide binding and the partial molar entropies of anions negatively correlate with the pK _a values. This indicates the important role of anion-induced solvent reorganization on the structural flexibility of cyt c in the alkaline transitions. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Growth and biomass allocation of sweet flag (Acorus calamus L.) under different nutrient conditions

Hydrobiologia - The antropogenically-induced process of eutrophication is accompanied by changes in the structure and function of the whole wetland ecosystem. Since the shift in a species ability...     

Germination and seedling establishment inAlisma gramineum, A. plantago-aquatica andA. lanceolatum under different environmental conditions

The seed germination and seedling establishment ofAlisma gramineum, A. lanceolatum andA. plantago-aquatica were investigated to find differences in the reproductive strategy of these species and to explain their ecological and distributional differentiation. The influences of stratification, temperature and flooding on seed germination, winter survival of seedlings and their further development were tested in the laboratory and in the experimental garden. Seeds of the all species studied were dormant immediately after harvesting. Cold stratification was necessary for successful germination. Seeds germinated best under shallow water in temperatures of 25 °C and 25/10 °C and did not need fluctuating day/night temperatures to break dormancy. Seedlings established best under the limosal-terrestrial conditions in summer, and overwintered successfully only when flooded. The main interspecific differences found were in the percentage of germinative and dormant seeds, in the germination rates after individual treatments, in the course of ontogenetic development and in the longevity as well as in the resistance of vegetative organs to environmental conditions. Possible effects of the above-listed facts on the ecological amplitude and distribution of the studied species are discussed.     

Chemical potential of Aphelandra sp. cell cultures

Six different callus lines and three different suspension culture lines were established from plants of two Aphelandra species (Acanthaceae). All established lines were analyzed for secondary metabolite accumulation. A discrepancy between secondary metabolites accumulated in the plants and in the cell cultures could be observed. All established Aphelandrasp. cell cultures produced verbascoside (acteoside) as the major extractable metabolite. Time course experiments were carried out to investigate the relationship between cell growth and verbascoside production. In the present study it was shown that verbascoside accumulation was growth dependent and positively related to the presence of 2,4-D in the medium. The conditions in which verbascoside represents ca. 18% of cell culture weight have been defined. Free polyamines were detected in the cell culture lines cultivated in MS liquid medium (cysteine 10 mg l^-1, thiamine 1 mg l^-1, 2,4-D 1 mg l^-1, kinetin 0.2 mg l^-1 and sucrose 30 g l^-1). Putrescine and spermidine accumulated within 8 days to a maximum of 8.4 μmol g^-1 of dry wt and 2.6 μmol g^-1 of dry wt respectively and thereafter their concentration decreased rapidly. There was no evidence for the presence of spermine or any other type of free or conjugated polyamines in the tested cell culture lines. This revised version was published online in June 2006 with corrections to the Cover Date.     

Confirmation of the presence of a Cu(II)/topa quinone active site in the amine oxidase from fenugreek seedlings

Amine oxidase from etiolated seedlings of fenugreek (Trigonellafoenum—graecum) has been isolated by a purification procedureinvolving three chromato—graphic steps. The homogeneousenzyme is of pink colour with a visible absorption maximum at500 nm. The dimeric enzyme (2 75 kDa) is a slightly acidicprotein (pl 6.8) containing 8% neutral sugars. N—ter—minalamino acid sequence of the enzyme shows a high degree of similarityto other plant and microbial copper—containing amine oxidases.The best substrates of the enzyme are aliphatic diamines andsome polyamines, whereas inhibitors are substrate analogues,copper complexing agents, some alkaloids and several other compounds.Spectrophotometric titra—tions with phenylhydrazines demonstratedone reactive carbonyl group per subunit of the enzyme and redox—cyclicquinone staining after native electrophor—esis indicatedthe presence of a quinone cofactor. Differential pulse polarographyshowed the existence of a copper/quinone—containing activesite. The resonance Raman spectroscopy and the pH—dependentshift of the absorption spectrum of the enzyme p—nitrophenylhydrazoneconfirm unambiguously the identity of the cofactor with topaquinone. EPR spectra of the enzyme are in accordance with thoseof tetragonal cupric complexes as known for other copper—containingamine oxidases. Besides the copper, Mn(II)ions were detectedthat partially occupy another metal site in the enzyme, buttheir catalytical importance is unlikely. Key words: Fenugreek, Trigonella foenum—graceum, amine oxidase, topa quinone     

Differentiating smokers and nonsmokers based on Raman spectroscopy of oral fluid and advanced statistics for forensic applications

Raman spectroscopy has proven to be a valuable tool for analyzing various types of forensic evidence such as traces of body fluids. In this work, Raman spectroscopy was employed as a nondestructive technique for the analysis of dry traces of oral fluid to differentiate between smoker and nonsmoker donors with the aid of advanced statistical tools. A total of 32 oral fluid samples were collected from donors of differing gender, age and race and were subjected to Raman spectroscopic analysis. A genetic algorithm was used to determine eight spectral regions that contribute the most to the differentiation of smokers and nonsmokers. Thereafter, a classification model was developed based on the artificial neural network that showed 100% accuracy after external validation. The developed approach demonstrates great potential for the differentiation of smokers and nonsmokers based on the analysis of dry traces of oral fluid.