Deuteration of Water Enables Self‐Organization of Phospholipid‐Based Reverse Micelles

Phospholipid‐based reverse micelles are composed of branched cylinders. Their branching points are known to attract themselves and to slide along branches. The rate of this sliding is governed by the lifetime of H(D)‐bonded water bridges between phospholipid molecules. This lifetime is increased when the water is deuterated. On condition that the water contains at least 40 D atoms %, water/dipalmitoylphosphatidylcholine (DPPC)/deuterated pyridine reverse micelles with the composition 1.1:1:250 (v/v) have been shown to self‐organize into a liquid crystal in the 310–316 K temperature range. The mechanism of this self‐organization is unraveled by following the FTIR and ¹H NMR spectra of more concentrated micelles upon heating. During the preparation of micelles, pyridine‐(D⁺)H⁺ ions are formed. They give rise to hydron transfers, under the influence of the DPPC electric charges, evidenced by two broad FTIR absorptions above (BB1) and below (BB2) the ν(C? O) stretch. These hydron transfers occur along strong (D⁺)H⁺ bonds of pyridinium ions with pyridine (BB1) and DPPC C?O groups (BB2). The proton transfers at the interface of micelles, relayed in the continuous pyridine medium, create a tenuous link between separated micelles, thus facilitating their organization. Upon heating, DPPC heads shrink and DPPC chains expand to make wedge‐shaped DPPC molecules. The micelles then change in shape: cylinders constrict and enclosed water drifts towards branching points, which swell. Branching points of neighboring micelles come into contact. Due to the deuteration of water these contacts are prolonged and H bonds are formed between DPPC molecules located in each branching point. Upon storage at 39 °C, these branching points fuse. The lateral diffusion of DPPC molecules becomes free, as evidenced by a narrowing of all ¹H NMR resonances. Upon further heating, reorganization into a liquid crystal occurs.     

Étude structurale de britholite au césium Sr7La2Cs(PO4)5(SiO4)F2

Several studies demonstrated the ability of britholites to retain radionuclides such as the caesium and actinides. Therefore, three compounds with formulas Sr₈LaCs(PO₄)₆F₂, Sr₇La₂Cs(PO₄)₅(SiO₄)F₂ and Sr₂La₇Cs(SiO₄)₆F₂, were prepared by solid state reaction. However, it seems that only the mono-silicated composition was obtained in a pure state. In this present work, the X-ray diffraction and magnetic nuclear resonance have been used to investigate the structure for this composition. The results showed that in fact this phase was not pure, but it was mixed with a secondary phase, SrLaCs(PO₄)₂. The refinement by the Rietveld method allowed also to precise the distribution of La³⁺ and Cs⁺ ions between the two cationic sites of the apatite.     

Snail Hepatopancreatic Lipase: A New Member of Invertebrates Lipases' Group

Higher animal's lipases are well characterized; however, much less is known about lipases from mollusks. A lipolytic activity was located in the land snail (Eobania vermiculata) digestive glands (hepatopancreas), from which a snail digestive lipase (SnDL) was purified. Pure SnDL has a molecular mass of 60 kDa; it does not present the interfacial activation phenomenon. It was found to be more active on short-chain triacylglycerols than on long-chain triacylglycerols. The NH₂-terminal sequence of the SnDL shows 66% of identity with the 17 NH₂-terminal amino acids of a putative lipase from sea urchin (Strongylocentrotus purpuratus). No sequence identity was found with known lipases. Interestingly, neither colipase nor bile salts were detected in the snail hepatopancreas. This suggests that colipase evolved in vertebrates simultaneously with the appearance of an exocrine pancreas and a true liver which produces bile salts. Altogether, these results suggest that SnDL is a member of a new group of digestive lipases belonging to invertebrates.     

Recent developments in microbial inulinases

Microbial inulinases are an important class of industrial enzymes that have gained much attention recently. Inulinases can be produced by a host of microorganisms, including fungi, yeast, and bacteria. Among them, however, Aspergillus sp. (filamentous fungus) and Kluyveromyces sp. (diploid yeast) are apparently the preferred choices for commercial applications. Among various substrates (carbon source) employed for their production, inulin-containing plant materials offer advantages in comparison to pure substrates. Although submerged fermentation has been universally used as the technique of fermentation, attempts are being made to develop solidstate fermentation technology also. Inulinases catalyze the hydrolysis of inulin to d-fructose (fructose syrup), which has gained an important place in human diets today. In addition, inulinases are finding other newer applications. This article reviews more recent developments, especially those made in the past decade, on microbial inulinases—its production using various microorganisms and substrates. It also describes the characteristics of various forms of inulinases produced as well as their applications.     

(2‐Hydroxy isobutyric) acid containing poly(glycolic acid): Structure–properties relationship

Poly(glycolic acid) (PGA) and a series of novel random copolymers of PGA containing 2‐hydroxyisobutyrric acid (PGAPHIB) (HIB unit content from 1.5 to 7.4 mol %) were synthesized and characterized in terms of chemical structure and molecular weight. Afterward, the polyesters were examined by thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction techniques. The copolymers, which displayed a better thermal stability than PGA, at room temperature appeared as semicrystalline materials: the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of the melting temperature with respect to homopolymer PGA. Baur's equation described well the T_m‐composition data. X‐ray diffraction measurements allowed the identification of the PGA crystalline structure in all cases. After melt quenching, semicrystalline samples were obtained with the exception of PGAPHIB7.4 copolymer. The introduction of HIB units decreased the crystallization rate compared with pure PGA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1901–1910, 2010     

Determination of starane (fluroxypyr) herbicide using flow injection spectrophotometry.

The starane herbicide was spectrophotometrically determined by the diazotization method in a flow injection assembly. Since starane is a substituted pyridyl compound the NH2 group at the p-position was exploited for diazotization. Starane was diazotized with nitrite and the diazotized product is coupled with beta-naphthol. The absorbance of the resulting azo dye was measured at 395 nm with a molar absorptivity of 1.5 x 10(4) L mol(-1) cm(-1). The calibration graph was linear over the range of 0.6 to 10 microg/mL, with a relative standard deviation (RSD) of 1.67% and a sampling through put of 60 samples h(-1). The % recovery for the determination of starane was found to be 96%. The method was successfully applied to the determination of the active ingredient of starane herbicide in its formulation as well as in food samples.     

A new proof of the integrability of the subdifferential of a convex function on a Banach space

We provide a simple proof of the Moreau-Rockafellar theorem that a proper lower semicontinuous convex function on a Banach space is determined up to a constant by its subdifferential.