Detection of hypophosphite, phosphite, and orthophosphate in natural geothermal water by ion chromatography

Current doctrine states that phosphorus is incorporated into cells in the pentavalent(V) oxidation state as orthophosphate. However, recent studies show that microorganisms contain enzymes used to metabolize reduced forms of phosphorous, including phosphite(III) and hypophosphite(I), which suggests that there is a natural source for these chemical species. This paper will discuss suppressed conductivity ion chromatography methods developed to detect hypophosphite, phosphite, and orthophosphate in a geothermal water matrix containing fluoride, chloride, bromide, nitrate, hydrogen carbonate and sulfate. All peaks were clearly resolved, and calibrations were linear with estimated 3sigma detection limits of 0.83, 0.39, and 0.35 microM for hypophosphite, phosphite, and orthophosphate, respectively.     

A Process to Produce Penicillin G Acylase by Surface-Adhesion Fermentation Using <Emphasis Type="Italic">Mucor griseocyanus</Emphasis> to Obtain 6-Aminopenicillanic Acid by Penicillin G Hydrolysis

The production of extracellular and mycelia-associated penicillin G acylase (maPGA) with Mucor griseocyanus H/55.1.1 by surface-adhesion fermentation using Opuntia imbricata, a cactus, as a natural immobilization support was studied. Enzyme activity to form 6-aminopencillanic acid (6-APA) from penicillin G was assayed spectrophotometrically. The penicillin G hydrolysis to 6-APA was evaluated at six different times using PGA samples recovered from the skim milk medium at five different incubation times. Additionally, the effect of varying the penicillin G substrate concentration level on the PGA enzyme activity was also studied. The maximum reaction rate, V _max, and the Michaelis constant, K _M, were determined using the Michaelis–Menten model. The maximum levels for maPGA and extracellular activity were found to be 2,126.50 international unit per liter (IU/l; equal to 997.83 IU/g of support) at 48 h and 755.33 IU/l at 60 h, respectively. Kinetics of biomass production for total biomass showed a maximum growth at 60 h of 3.36 and 2.55 g/l (equal to 0.012 g of biomass per gram of support) for the immobilized M. griseocyanus biomass. The maPGA was employed for the hydrolysis of penicillin G to obtain 6-APA in a batch reactor. The highest quantity of 6-APA obtained was 226.16 mg/l after 40-min reaction. The effect of substrate concentration on maPGA activity was evaluated at different concentrations of penicillin G (0–10 mM). K _M and V _max were determined to be 3.0 × 10⁻³ M and 4.4 × 10⁻³ mM/min, respectively.     

Extraction and analysis of ellagic acid from novel complex sources

Ellagic acid (EA) was quantified by reversed-phase high-performance liquid chromatography (RPHPLC) coupled with photodiode array detection (DAD) in five fine-powdered plants collected from the semiarid region of Mexico. Samples analysed included Jatropha dioica branches (Dragon’s blood), Euphorbia antisyphyllitica branches (Candelilla), Turnera diffusa Willd leaves (Damiana), Flourensia cernua leaves (hojasén) and Punica granatum husk (pomegranate) at two maturity stages (“turning” or intermediate and maturated fruit, considered as positive controls). The results demonstrated high EA concentrations in all tested samples which are novel sources of this natural antioxidant. The method developed for the EA analysis is fast and it showed an excellent linearity range, repeatability, intra-and inter-day precision and accuracy with respect to the methods reported for the EA analysis.     

Engineering Homochiral Metal–Organic Frameworks by Spatially Separating 1D Chiral Metal–Peptide Ladders: Tuning the Pore Size for Enantioselective Adsorption

The reaction of the chiral dipeptide glycyl‐L(S)‐glutamate with Co^II ions produces chiral ladders that can be used as rigid 1D building units. Spatial separation of these building units with linkers of different lengths allows the engineering of homochiral porous MOFs with enhanced pore sizes, pore volumes, and surface areas. This strategy enables the synthesis of a family of isoreticular MOFs, in which the pore size dictates the enantioselective adsorption of chiral molecules (in terms of their size and enantiomeric excess).     

Catalytic and Thermodynamic Properties of a Tannase Produced by Aspergillus niger GH1 Grown on Polyurethane Foam

Tannase is an inducible enzyme with important applications in the food and pharmaceutical industries. This enzyme was produced by the fungus Aspergillus niger GH1 under solid-state fermentation using polyurethane foam as solid support and tannic acid as sole carbon source and tannase inducer. Physicochemical properties of A. niger tannase were characterized, and the kinetic and thermodynamics parameters on methyl gallate hydrolysis were evaluated. The enzyme was stable in a pH range of 2-8 and a functional temperature range of 25-65 °C. The highest k(cat) value was 2,611.10 s(-1) at 65 °C. Tannase had more affinity for methyl gallate at 45 °C with a K(M) value of 1.82 mM and an efficiency of hydrolysis (k(cat)/K(M)) of 330.01 s(-1) mM(-1). The lowest E(a) value was found to be 21.38 kJ/mol at 4.4 mM of methyl gallate. The lowest free energy of Gibbs (ΔG) and enthalpy (ΔH) were found to be 64.86 and 18.56 kJ/mol, respectively. Entropy (ΔS) was -0.22 kJ/mol K. Results suggest that the A. niger GH1 tannase is an attractive enzyme for industrial applications due its catalytic and thermodynamical properties.     

Homochirality beyond grinding: deracemizing chiral crystals by temperature gradient under boiling

A single-chirality solid phase can be obtained in boiling solutions containing a racemic mixture of left- and right-handed enantiomorphous crystals due to dissolution-crystallization cycles induced by a temperature gradient. This phenomenon provides further insights into asymmetric amplification mechanisms under presumably prebiotic conditions.     

Structural aspects of the product from glyoxal and tetrakis(ethoxycarbonylamino)ethane

The base-promoted addition of glyoxal to 1,1,2,2-tetrakis(ethoxycarbonylamino)ethane in DMF gives a product mixture containing mostly 1,1′,3,3′-tetrakis(ethoxycarbonyl)-4,4′,5,5,'-tetrahydroxy-2,2′-biimidazolidyl. An alternate structure containing a tetraazadecalin system was considered less likely, since the most significant peak in the mass spectrum of this product and a tetraacetate derivative corresponded to half the mass of the parent ion. Two-dimensional nmr spectra on the major hplc fraction are more consistent with the biimidazolidinyl structure (very low J_vic and lack of NOE enhancement). A HETCOSY spectrum on the mixture allowed assignment of ¹H nmr shifts.     

On Groups with Finitely Many Conradian Orderings

We study the space of left-orderings on groups with (only) finitely many Conradian orderings. We show that, within this class of groups, having an isolated left-ordering is equivalent to having finitely many left-orderings.