Ash content modulation of torsionally derived effective material properties in cortical mouse bone

The purpose of this study was to evaluate the effects of isolated alterations in mineral content on mouse bone torsional properties. The femora and tibiae from 25 eight-week-old male A/J strain mice were divided into five groups and selectively decalcified from 5% to 20%. The right femora were then tested to failure in torsion while the tibiae were ashed to determine final mineral content of the decalcified bones. Contralateral femora were serially cross-sectioned to determine geometric properties, and effective material properties were then calculated from the geometric and structural properties of each femoral pair. We found that the relationship between ash content and effective shear modulus or maximum effective shear stress could best be characterized through a power law, with an exponential factor of 6.79 (R2 = 0.85) and 4.04 (R2 = 0.67), respectively. This indicates that in a murine model, as with other species, small changes in ash content significantly influence effective material properties. Furthermore, it appears that (in adolescent A/J strain mice) effective shear modulus is more heavily affected by changes in mineralization than is maximum effective shear stress when these properties are derived from whole bone torsional tests to failure.     

Naphthalene degradation and biosurfactant activity by Bacillus cereus 28BN

Biosurfactant activity and naphthalene degradation by a new strain identified as Bacillus cereus 28BN were studied. The strain grew well and produced effective biosurfactants in the presence of n-alkanes, naphthalene, crude oil and vegetable oils. The biosurfactants were detected by the surface tension lowering of the medium, thin layer chromatography and infrared spectra analysis. With (2%) naphthalene as the sole carbon source, high levels of rhamnolipids at a concentration of 2.3 g 1(-1) were determined in the stationary growth. After 20 d of incubation 72 +/- 4% of the initial naphthalene was degraded. This is the first report for a Bacillus cereus rhamnolipid producing strain that utilized naphthalene under aerobic conditions. The strain looks promising for application in environmental technologies.     

A specific alkaline phosphatase from Saccharomyces cerevisiae with protein phosphatase activity

In this paper, specific PHO13 alkaline phosphatase from Saccharomyces cerevisiae was demonstrated to possess phosphoprotein phosphatase activity on the phosphoseryl proteins histone II-A and casein. The enzyme is a monomeric protein with molecular mass of 60 kDa and hydrolyzes p-nitrophenyl phosphate with maximal activity at pH 8.2 with strong dependence on Mg²⁺ ions and an apparent K_m of 3.6×10⁻⁵ M. No other substrates tested except phosphorylated histone II-A and casein were hydrolyzed at any significant rate. These data suggest that the physiological role of the p-nitrophenyl phosphate-specific phosphatase may involve participation in reversible protein phosphorylation.     

Dependence of yeast permeabilization with Triton X-100 on the cell age

Summary Acid phosphatase activity and protein release were determined in cell suspensions ofYarrowia lipolytica andTorulospora delbrueckii at different stages of their growth by permeabilization with Triton X-100. The effect of the surfactant on the cell permeability did not depend on the cell age.     

Soluble CuA domain of cyanobacterial cytochrome c oxidase

The genomes of several cyanobacteria show the existence of gene clusters encoding subunits I, II, and III of aa(3)-type cytochrome c oxidase. The enzyme occurs on both plasma and thylakoid membranes of these oxygenic phototrophic prokaryotes. Here we report the expression and purification of a truncated subunit II copper A (Cu(A)) domain (i.e. the electron entry and donor binding site) of cytochrome c oxidase from the cyanobacterium Synechocystis PCC 6803 in high yield. The water-soluble purple redox-active bimetallic center displays a relatively low standard reduction potential of 216 mV. Its absorption spectrum at pH 7 is similar to that of other soluble fragments from aa(3)-type oxidases, but the insensitivity of both absorbance and circular dichroism spectra to pH suggests that it is less exposed to the aqueous milieu compared with other Cu(A) domains. Oxidation of horse heart cytochrome c by the bimetallic center follows monophasic kinetics. At pH 7 and low ionic strength the bimolecular rate constant is (2.1 +/- 0.3) x 10(4) m-1 s(-1), and the rates decrease upon the increase of ionic strength. Sequence alignment and modeling of cyanobacterial Cu(A) domains show several peculiarities such as: (i) a large insertion located between the second transmembrane region and the putative hydrophobic cytochrome c docking site, (ii) the lack of acidic residues shown to be important in the interaction between cytochrome c and Paracoccus Cu(A) domain, and (iii) an extended C terminus similar to Escherichia coli ubiquinol oxidase.     

Alkaloid diversity in Galanthus elwesii and Galanthus nivalis

Seventy alkaloids of galanthamine, lycorine, homolycorine, tazettine, haemanthamine, narciclasine, and tyramine types were detected by GC/MS in 25 Galanthus elwesii and seven Galanthus nivalis populations, collected from different locations in Bulgaria. Intraspecies diversity in the alkaloid profiles regarding the main alkaloid types (chemotypes) was observed. Tyramine-type protoalkaloids (namely, hordenine and its derivatives) were dominant in 19 populations of G. elwesii. In other populations of G. elwesii, the plants accumulated mainly homolycorine-, lycorine-, and galanthamine-type alkaloids. The alkaloid profiles of G. nivalis were dominated by narciclasine-, galanthamine-, lycorine-, haemanthamine-, or tazettine-type compounds. Geographical distribution of chemotypes indicated a relationship between populations, since adjacent populations often displayed similar alkaloid profiles. The results from year-to-year sampling and transplantation experiments imply genetic determination of alkaloid synthesis in the two studied species of Galanthus.     

Production and structural elucidation of trehalose tetraesters (biosurfactants) from a novel alkanothrophic Rhodococcus wratislaviensis strain

Aims:  To isolate a biosurfactant-producing bacterial strain and to identify and characterize the chemical structure and properties of its biosurfactants.
Methods and Results:  The bacterium Rhodococcus wratislaviensis BN38, isolated from soil, was found to produce glycolipid biosurfactants when grown on 2% n -hexadecane. The glycolipids were isolated by chromatography on silica gel columns and their structures elucidated using a combination of multidimensional NMR and ESI-MS/MS techniques. The main product was identified as 2,3,4,2'-trehalose tetraester with molecular mass of 876 g mol⁻¹. It was also noted that the biosurfactant was produced under nitrogen-limiting conditions and could not be synthesized from water-soluble substrates. The purified product showed extremely high surface-active properties.
Conclusions:  The glycolipid biosurfactant produced by the alkanothrophic strain R. wratislaviensis BN38 was characterized to be 2,3,4,2'-trehalose tetraester which exhibited high surfactant activities.
Significance and Impact of the Study:  Strain BN38 of R. wratislaviensis is a potential candidate for use in bioremediation applications or in biosurfactant exploration.     

Precision, Proteome Coverage, and Dynamic Range of Arabidopsis Proteome Profiling Using 15N Metabolic Labeling and Label-free Approaches

This study reports the comprehensive comparison of (15)N metabolic labeling and label free proteomic strategies for quantitation, with particular focus on plant proteomics. Our investigation of proteome coverage, dynamic range and quantitative precision for a wide range of mixing ratios and protein loadings aim to aid the investigators in the decision making process during experimental design. One of the main characteristics of the label free strategy is the applicability to all starting material, which is a limitation to the metabolic labeling. However, particularly at mixing ratios up to 10-fold the (15)N metabolic labeling proved to be more precise. Contrary to usual practice based on the results from this study, we suggest that nonequal mixing ratios in metabolic labeling could further increase the proteome coverage for quantitation. On the other hand, the label free strategy, in combination with low protein loading allows the extension of the dynamic range for quantitation and it is more precise at very high ratios, which could be important for certain types of experiments.     

Biosurfactant production by a new Pseudomonas putida strain

Observation of both tensio-active and emulsifying activities indicated that biosurfactants were produced by the newly isolated and promising strain Pseudomonas putida 21BN. The biosurfactants were identified as rhamnolipids, the amphiphilic surface-active glycolipids usually secreted by Pseudomonas spp. Their production was observed when the strain was grown on soluble substrates, such as glucose or on poorly soluble substrates, such as hexadecane, reaching values of 1.2 g l(-1). When grown on hexadecane as the sole carbon source the biosurfactant lowered the surface tension of the medium to 29 mN m(-1) and formed stable and compact emulsions with emulsifying activity of 69%.