Temperature as an enantioselective parameter in enzymatic resolutions of racemic mixtures

Summary In the field of enhancement of the enantiomeric excess, the effect of temperature on the enantiomeric ratio, E, was investigated in lipase catalysed hydrolysis and transesterification. It was found that the equation (E₁)^T1=(E₂)^T2 correlated well with the experimental data obtained.     

Hydrolysis and Esterification with Lipase from Candida Cylindracea. Influence of the Reaction Conditions and Acid Moiety on the Enantiomeric Excess

The enantiomeric ratio for hydrolysis and synthesis of 1-phenyl ethanol esters of straight chain aliphatic carboxylic acids catalyzed by Candida cylindracea lipase was determined. A distinct maximum in enantiomeric ratio was observed for valeric and caproic acid in the hydrolytic direction. No significant maximum could be determined in the esterification reaction. Even though the enzyme provided larger enantiomeric ratios in the synthetic direction the enantiomeric excess of the alcohol was not higher. The enantiomeric excess was depressed by racemization reactions in the esterification as the reaction approached thermodynamic equilibrium at an insufficient conversion. While choosing the optimal chain length of the acyl donor is important in hydrolytic reactions it seems to be of greater value to raise the equilibrium conversion in the esterification reactions.     

Clinical impact of atrial fibrillation in patients with pulmonary hypertension

Background

Pulmonary hypertension (PH) is associated with progressive impairment of right ventricular function, reduced exercise capacity and a poor prognosis. Little is known about the prevalence, clinical manifestation and impact of atrial fibrillation (AF) on cardiac function in PH.

Methods

In a four year single-centre retrospective analysis 225 patients with confirmed PH of various origins were enrolled to investigate the prevalence of AF, and to assess the clinical manifestation, 6-minute walk distance, NT-proBNP levels, echocardiographic parameters and hemodynamics obtained by right heart catheterization in PH with AF.

Results

AF was prevalent in 31.1%. In patients with PH and AF, parameters of clinical deterioration (NYHA/WHO functional class, 6-minute walk distance, NT-proBNP levels) and renal function were significantly compromised compared to patients with PH and sinus rhythm (SR). In the total PH cohort and in PH not related to left heart disease occurrence of AF was associated with an increase of right atrial pressure (RAP) and right atrial dilatation. While no direct association was found between pulmonary artery pressure (PAP) and AF in these patients, right ventricular function was reduced in AF, indicating more advanced disease. In PH due to left heart failure the prevalence of AF was particularly high (57.7% vs. 23.1% in other forms of PH). In this subgroup, left atrial dilatation, increase of pulmonary capillary wedge pressure, PAP and RAP were more pronounced in AF than in SR, suggesting that more marked backward failure led to AF in this setting.

Conclusion

PH is associated with increased prevalence of AF. Occurrence of AF in PH indicates clinical deterioration and more advanced disease.     

Functional analysis and localisation of a delta-class glutathione S-transferase from Sarcoptes scabiei

The mite Sarcoptes scabiei causes sarcoptic mange, or scabies, a disease that affects both animals and humans worldwide. Our interest in S. scabiei led us to further characterise a glutathione S-transferase. This multifunctional enzyme is a target for vaccine and drug development in several parasitic diseases. The S. scabiei glutathione S-transferase open reading frame reported here is 684 nucleotides long and yields a protein with a predicted molecular mass of 26 kDa. Through phylogenetic analysis the enzyme was classified as a delta-class glutathione S-transferase, and our paper is the first to report that delta-class glutathione S-transferases occur in organisms other than insects. The recombinant S. scabiei glutathione S-transferase was expressed in Escherichia coli via three different constructs and purified for biochemical analysis. The S. scabiei glutathione S-transferase was active towards the substrate 1-chloro-2,4-dinitrobenzene, though the positioning of fusion partners influenced the kinetic activity of the enzyme. Polyclonal antibodies raised against S. scabiei glutathione S-transferase specifically localised the enzyme to the integument of the epidermis and cavities surrounding internal organs in adult parasites. However, some minor staining of parasite intestines was observed. No staining was seen in host tissues, nor could we detect any antibody response against S. scabiei glutathione S-transferase in sera from naturally S. scabiei infected dogs or pigs. Additionally, the polyclonal sera raised against recombinant S. scabiei glutathione S-transferase readily detected a protein from mites, corresponding to the predicted size of native glutathione S-transferase.     

Insect-like olfactory adaptations in the terrestrial giant robber crab

The robber crab (Birgus latro), also known as the coconut crab, is the world's largest land-living arthropod, with a weight reaching 4 kg and a length of over half a meter [1]. Apart from the marine larval stage 2, 3, this crab is fully terrestrial, and will actually drown if submerged in water [4]. A transition from sea to land raises dramatically new demands on the sensory equipment of an animal. In olfaction, the stimulus changes from hydrophilic molecules in aqueous solution to mainly hydrophobic in the gaseous phase [5]. The olfactory system of land crabs thus represents an excellent opportunity for investigating the effects of the transition from sea to land. Have land crabs come to the same solutions as other terrestrial animals, or is their olfactory sense characterized by unique innovations? Here, we show that the robber crab has evolved an olfactory sense with a high degree of resemblance to the insect system. The similarities extend to physiological, behavioral, and morphological characters. The insect nose of the robber crab is a striking example of convergent evolution and nicely illustrates how similar selection pressures result in similar adaptation     

Trace-element determination in individual peripheral blood cells and possible diagnostic applications

Trace elements are indispensable for the effective and proper functioning of biological systems. Recent years have demonstrated the conspicuous lack of knowledge about trace-element physiology. Establishment of reference values is a very difficult task, requiring the consideration of and compensation for a number of possible simultaneous phenomena. Peripheral blood has been used in medical diagnosis for a very long time, because, among other things, it is easily accessible. In the search for signs of lack or excess of minerals and trace elements in disease, the interest has been focused mainly on blood plasma or serum. The utilization of blood cells as a marker model is proposed here. The advent of the nuclear microprobe made possible the determination of elemental profiles of individual cells. The techniques of blood cell separation and preparation for microprobe analysis are presented and discussed. As an example of a possible diagnostic application, a set of reference data from a control group is compared to corresponding data from a group of patients suffering from acute myeloid leukemia.     

Intact salicylic acid signalling is required for potato defence against the necrotrophic fungus Alternaria solani

Plant Molecular Biology - HbMBF1a was isolated and characterized in H. brevisubulatum, and overexpressed HbMBF1a could enhance the salt tolerance and ABA insensitivity in Arabidopsis thaliana. The...     

Fungal and bacterial growth responses to N fertilization and pH in the 150-year 'Park Grass' UK grassland experiment

The effects of nitrogen (N) fertilization (0-150 kg N ha?1 year?1 since 1865) and pH (3.3-7.4) on fungal and bacterial growth, biomass and phospholipid fatty acid (PLFA) composition were investigated in grassland soils from the 'Park Grass Experiment', Rothamsted Research, UK. Bacterial growth decreased and fungal growth increased with lower pH, resulting in a 50-fold increase in the relative importance of fungi between pH 7.4 and 3.3. The PLFA-based fungal:bacterial biomass ratio was unchanged between pH 4.5 and 7.4, and decreased only below pH 4.5. Respiration and substrate-induced respiration biomass both decreased three- to fourfold with lower pH, but biomass concentrations estimated using PLFAs were unaffected by pH. N fertilization did not affect bacterial growth and marginally affected fungal growth while PLFA biomass marker concentrations were all reduced by higher N additions. Respiration decreased with higher N application, suggesting a reduced quality of the soil organic carbon. The PLFA composition was strongly affected by both pH and N. A comparison with a pH gradient in arable soil allowed us to generalize the pH effect between systems. There are 30-50-fold increases in the relative importance of fungi between high (7.4-8.3) and low (3.3-4.5) pH with concomitant reductions of respiration by 30-70%.     

Powdery mildew resistance in 155 Nordic bread wheat cultivars and landraces

The occurrence and distribution of seedling resistance genes and the presence of adult plant resistance to powdery mildew, was investigated in a collection of 155 Nordic bread wheat landraces and cultivars by inoculation with 11 powdery mildew isolates. Eighty-nine accessions were susceptible in the seedling stage, while 66 accessions showed some resistance. Comparisons of response patterns allowed postulation of combinations of genes Pm1a, Pm2, Pm4b, Pm5, Pm6, Pm8 and Pm9 in 21 lines. Seedling resistance was three times more frequent in spring wheat than in winter wheat. The most commonly postulated genes were Pm1a+Pm2+Pm9 in Sweden, Pm5 in Denmark and Norway, and Pm4b in Finland. Forty-five accessions were postulated to carry only unidentified genes or a combination of identified and unidentified genes that could not be resolved by the 11 isolates. Complete resistance to all 11 isolates was present in 18 cultivars. Adult plant resistance was assessed for 109 accessions after natural infection with a mixture of races. In all, 92% of the accessions developed less than 3-5% pathogen coverage while nine lines showed 10-15% infected leaf surface. The characterization of powdery mildew resistance in Nordic wheat germplasm could facilitate the combination of resistance genes in plant breeding programmes to promote durability of resistance and disease management.