A New Alkaliphilic Cold-Active Esterase from the Psychrophilic Marine Bacterium Rhodococcus sp.: Functional and Structural Studies and Biotechnological Potential

The special features of cold-adapted lipolytic biocatalysts have made their use possible in several industrial applications. In fact, cold-active enzymes are known to be able to catalyze reactions at low temperatures, avoiding side reactions taking place at higher temperatures and preserving the integrity of products. A lipolytic gene was isolated from the Arctic marine bacterium Rhodococcus sp. AW25M09 and expressed in Escherichia coli as inclusion bodies. The recombinant enzyme (hereafter called RhLip) showed interesting cold-active esterase activity. The refolded purified enzyme displayed optimal activity at 30 °C and was cold-active with retention of 50 % activity at 10 °C. It is worth noting that the optimal pH was 11, and the low relative activity below pH 10 revealed that RhLip was an alkaliphilic esterase. The enzyme was active toward short-chain p-nitrophenyl esters (C2–C6), displaying optimal activity with the butyrate (C4) ester. In addition, the enzyme revealed a good organic solvent and salt tolerance. These features make this an interesting enzyme for exploitation in some industrial applications.     

Large spontaneous polarization and clear hysteresis loop of a room-temperature hybrid ferroelectric based on mixed-halide [BiI3Cl2] polar chains and methylviologen dication

The search for hybrid organic-inorganic materials, which have the great advantage that they can be synthesized at moderate temperature (T < 200 °C), remains a great challenge in the field of ferroelectrics. Here, a room-temperature ferroelectric material with interesting characteristics, (MV)[BiI(3)Cl(2)] (MV(2+) = methylviologen), is reported. Its structure is based on polar inorganic chains resulting from a remarkable Cl/I segregation induced by methylviologen entities, which coincide with the fourfold polar axis of the tetragonal structure. Of great importance is that this room-temperature hybrid ferroelectric displays a clear electrical hysteresis loop with a large spontaneous polarization (>15 μC·cm(-2)).     

A Diiron(III,IV) Imido Species Very Active in Nitrene‐Transfer Reactions

Metal‐catalyzed nitrene transfer reactions arouse intense interest as clean and efficient procedures for amine synthesis. Efficient Rh‐ and Ru‐based catalysts exist but Fe alternatives are actively pursued. However, reactive iron imido species can be very short‐lived and getting evidence of their occurrence in efficient nitrene‐transfer reactions is an important challenge. We recently reported that a diiron(III,II) complex is a very efficient nitrene‐transfer catalyst to various substrates. We describe herein how, by combining desorption electrospray ionization mass spectrometry, quantitative chemical quench experiments, and DFT calculations, we obtained conclusive evidence for the occurrence of an {Fe^IIIFe^IV?NTosyl} intermediate that is very active in H‐abstraction and nitrene‐transfer reactions. DFT calculations revealed a strong radical character of the tosyl nitrogen atom in very low‐lying electronic configurations of the Fe^IV ion which are likely to confer its high reactivity.     

Coating characterization in controlled surface temperature laser heat treating

An evaluation of coating performances in feedback controlled surface temperature laser heat treating has been made in terms of a simple energy balance model, by using a 500 W c.w. CO₂ laser system able to perform such a kind of heat treating. Three different types of coating (manganese phosphate, titanium dioxide and colloidal graphite) have been investigated. The experimental results show that very different maximum processing speeds are ensured by each coating, in spite of their quite similar percentage of absorbed laser power. This more complete characterisation can be used to improve the performances of the aforesaid technique, avoiding any failure in controlled surface temperature laser heat treating.     

Use of 111In–L–LDL radiotracers to detect human pancreatic and mice melanoma tumors

The present study was designed to evaluate the potential of labeled low‐density lipoprotein with ¹¹¹In using a lipid chelating agent (bis(stearylamide) of diethylenetriaminepentaacetic acid: L) to detect pancreatic tumors and melanoma in mice by gamma‐scintigraphy. We compare the biodistribution of radioactivity and scintigraphic images in nude mice heterotransplanted with human cancerous pancreatic duct cells (Capan‐1) and in mice transplanted with murine tumor cells (B16 melanoma). Biodistribution studies showed that radioactivity was twice as high in the Capan‐1 xenograft after injection of the radiolabel than after injection of radiometal alone, and 34‐fold higher in the B16 tumor. On gamma‐scintigraphic imaging, the Capan‐1 tumor was just visible, whereas the B16 melanoma was clearly imaged. The lack of contrast of the Capan‐1 tumor compared with the B16 melanoma could be due to a poor vascularization. Copyright © 2003 John Wiley & Sons, Ltd.     

Phase transitions of long chain esters of meso-tetrakis(para-carboxyphenyl)porphyrin

Several long chain esters of meso-tetrakis(para-carboxyphenyl)porphyrin, and two of their metal complexes (Cu, Zn) have been prepared and characterized. Each of them exhibits at least one thermotropic phase transition below the clearing point to the isotropic liquid, but no definitive evidence of liquid crystallinity has been found by differential scanning calorimetry, optical microscopy, or X-ray diffraction.     

Carbon-to-metal bonds: Electrochemical reduction of 2-butenenitrile

2-Butenenitrile belongs to the large family of electron deficient vinylic monomers that usually form 100 to 500 nm thick grafted polymer films by electroreduction. However, 2-butenenitrile exhibits a slightly acidic hydrogen atom on its CH₃ group that inhibits the anionic polymerization usually observed with ‘classical’ organic monomers such as its isomer methacrylonitrile. 2-Butenenitrile thus gives nanometer thick grafted film by electroreduction, essentially composed of a mixture of monomers, dimers and trimers and in the same way, allows an easy observation by XPS of the chemical signature of the grafting, i.e. the carbon-to-nickel bond, observed at 283.6 eV.     

Regularity properties for Monge transport density and for solutions of some shape optimization problem

In this paper we study the dimension of some measures which are related to the classical Monge's optimal mass transport problem and are solutions of a scalar shape optimization problem. Moreover in the case of maximal dimension we will study the summability of the associate densities. Received: 16 November 2000 / Accepted: 4 December 2000 / Published online: 18 January 2002     

Evidence that the (6-4) photolyase mechanism can proceed through an oxetane intermediate

Using the analogue of TpT methylated at the 3'-end N3 position (Tpm3T), we demonstrate that when the oxetane/(6-4) pathway is precluded, water addition occurs at the 3'-end C6 position of the oxetane intermediate to provide its opening. Photoreversal of this (6-4) photoproduct C6 hydrate brings the first experimental evidence that the (6-4) photolyase repair can proceed through an oxetane intermediate.     

Interactions of poly(amidoamine) dendrimers with Survanta lung surfactant: the importance of lipid domains

The interaction of generation 5 (G5) and 7 (G7) poly(amidoamine) (PAMAM) dendrimers with mica-supported Survanta bilayers is studied with atomic force microscopy (AFM). In these experiments, Survanta forms distinct gel and fluid domains with differing lipid composition. Nanoscale defects are induced by the PAMAM dendrimers. The positively charged dendrimers remove lipid from the fluid domains at a significantly greater rate than for the gel domains. Dendrimer accumulation on lipid edges and terraces preceding lipid removal has been directly imaged. Immediately following lipid removal, the mica surface is clean, indicating that lipid defects are not induced by dendrimers binding to the mica substrate and displacing the lipid.