Tracing hotspots of soil erosion in high mountain environments: how forensic science based on plant eDNA can lead the way. An opinion

Plant and Soil - High mountain environments are among the most fragile on Earth. Due to anthropogenic disturbances and the exposure to extreme weather events, the rates of soil erosion have...     

Discovery of a novel styrene monooxygenase originating from the metagenome

Oxygenases form an interesting class of biocatalysts, as they typically perform oxygenations with exquisite chemo-, regio-, and/or enantioselectivity. It has been observed that, once heterologously expressed in Escherichia coli, some oxygenases are able to form the blue pigment indigo. We have exploited this characteristic to screen a metagenomic library derived from loam soil and identified a novel oxygenase. This oxygenase shows 50% sequence identity with styrene monooxygenases from pseudomonads (StyA). Only a limited number of homologs can be found in the genome sequence database, indicating that this biocatalyst is a member of a relatively small family of bacterial monooxygenases. The newly identified monooxygenase catalyzes the epoxidation of styrene and styrene derivatives and forms the corresponding (S)-epoxides with excellent enantiomeric excess [e.g., (S)-styrene oxide is formed with >99% enantiomeric excess, ee] and therefore is named styrene monooxgenase subunit A (SmoA). SmoA shows high enantioselectivity towards aromatic sulfides [e.g., (R)-ethyl phenyl sulfoxide is formed with 92% ee]. This excellent enantioselectivity in combination with the moderate sequence identity forms a clear indication that SmoA from a metagenomic origin represents a new enzyme within the small family of styrene monooxygenases.     

Mutants for photosystem I subunit D of Arabidopsis thaliana: effects on photosynthesis, photosystem I stability and expression of nuclear genes for chloroplast functions

In Arabidopsis thaliana, the D-subunit of photosystem I (PSI-D) is encoded by two functional genes, PsaD1 and PsaD2, which are highly homologous. Knock-out alleles for each of the loci have been identified by a combination of forward and reverse genetics. The double mutant psad1-1 psad2-1 is seedling-lethal, high-chlorophyll-fluorescent and deficient for all tested PSI subunits, indicating that PSI-D is essential for photosynthesis. In addition, psad1-1 psad2-1 plants show a defect in the accumulation of thylakoid multiprotein complexes other than PSI. Of the single-gene mutations, psad2 plants behave like wild-type (WT) plants, whereas psad1-1 markedly affects the accumulation of PsaD mRNA and protein, and photosynthetic electron flow. Additional effects of the psad1-1 mutation include a decrease in growth rate under greenhouse conditions and downregulation of the mRNA expression of most genes involved in the light phase of photosynthesis. In the same mutant, a marked decrease in the levels of PSI and PSII polypeptides is evident, as well as a light-green leaf coloration and increased photosensitivity. Increased dosage of PsaD2 in the psad1-1 background restores the WT phenotype, indicating that PSI-D1 and PSI-D2 have redundant functions.     

Synthesis of novel hydroxymethyl substituted analogues related to carbovir and neplanocin A

Two enantiomerically pure hydroxymethyl substituted cyclopentene nucleoside analogues (42 and 53) related to carbovir and neplanocin A, respectively, were prepared from the chiral pool of iridoid glucosides. In addition two saturated hydroxymethylated analogues (44 and 45) were obtained from a protected intermediate.     

Protein instability during HIC: describing the effects of mobile phase conditions on instability and chromatographic retention

Hydrophobic interaction chromatography (HIC) is known to be potentially denaturing to proteins, but the effects of mobile phase conditions on chromatographic behavior are not well understood. In this study, we apply a model describing the effects of secondary protein unfolding equilibrium on chromatographic behavior, including the effects of salt concentration on both stability and adsorption. We use alpha-lactalbumin as a model protein that in the presence and absence of calcium, allows evaluation of adsorption parameters for folded and unfolded species independently. The HIC adsorption equilibrium under linear binding conditions and solution phase protein stability have been obtained from a combination of literature and new experiments. The effect of salt concentration on protein stability and the rate constant for unfolding on the chromatographic surface have been determined by fitting the model to isocratic chromatography data under marginally stable conditions. The model successfully describes the effects of added calcium and ammonium sulfate. The results demonstrate the importance of considering the effects on stability of mobile phase modifiers when applying HIC to marginally stable