Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers

Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.     

Evidence of a critical content in Fe(0) on FoCa7 bentonite reactivity at 80 °C

In order to assess the evolution of the confinement properties of clay engineered barriers (EBS) when in contact with metallic canisters containing radioactive wastes, Fe(0)-bentonite interactions need to be assessed. “45 days–80 °C” tests were performed using powdered FoCa7 bentonite and metallic iron. Since one fundamental parameter may be the available quantity of Fe(0), a wide range of Iron/Clay mass ratios (I/C) from 0 to 1/3 is used. The confinement power of clay material results from the swelling properties and the retention capacity. Thus, the major criterion which is chosen to assess the evolution of the confinement properties in this study is the variation of Cation Exchange Capacity (CEC). In parallel, the physico-chemical evolution of bentonite is studied using XRD and EDS-TEM microanalyses. The evolution of the distribution of iron environments is obtained by ⁵⁷Fe Mössbauer spectroscopy.This study evidences that both kaolinite and smectite from the bentonite are altered into SiAlFe gels when in contact with Fe(0). These gels maturates into Fe-rich di-trioctahedral phyllosilicates, whose composition is bounded by the one of odinite and greenalite in a Fe–M⁺–4Si diagram when I/C = 1/3. Most of all, it is evidenced that the reaction depends on the available quantity of Fe(0). When the I/C ratio is between 1/30 and 1/7.5, the exchange capacity of FoCa7 bentonite starts decreasing, the consumption of Fe(0) becomes significant, the alteration of smectites occurs and secondary oxides are formed. The crystallization of Fe-rich phyllosilicates is observable when I/C ratio is higher, from a threshold between 1/7.5 and 1/5. Above I/C = 1/3.75, initial iron oxides are strongly consumed and participate in the incorporation of Fe²⁺ and Fe³⁺ in gels or new phyllosilicates octahedra.These experimental results were used as input data for the prediction of the long-term evolution of the EBS using Crunch reaction-transport model.     

Carbon nanotubes for interconnects in future integrated circuits: The challenge of the density

A CVD process with a high density of CNTs has been developed on doped silicon material thanks to plasma pre-treatment of the catalyst. With this process small diameter double and triple wall CNTs with an average diameter of 3.8 nm have been grown. The density of the best materials on blanket substrate is larger than 10¹² cm^? 2. These materials have been successfully integrated in via holes with a diameter ranging between 1 µm and 0.3 µm with an equivalent density. In 140 nm hole diameter large 70 nm bundle formations have been observed. In these bundles a density of CNT walls close to 10¹³ cm^? 2 has been estimated.     

Self-help treatment for insomnia: Bibliotherapy with and without professional guidance.

Fifty-four adults with primary insomnia were randomly assigned to a self-help treatment (cognitive-behavioral bibliotherapy [BT]), BT with weekly phone consultations, or a waiting-list control (WL) group. Treated participants were mailed 6 treatment booklets at the rate of 1 booklet per week; 1/2 of them also received minimal professional guidance through a 15-min weekly phone consultation. The WL group members continued to monitor their sleep during this period. Participants in both treatment conditions improved significantly on the main outcome variables (total wake time and sleep efficiency) at posttreatment, whereas WL participants remained unchanged. The addition of weekly phone calls slightly enhanced improvements at posttreatment. However, both treatment conditions were comparable at follow-up. These results suggest that BT, with or without minimal professional guidance, is an effective approach for treating primary insomnia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lipase-based quantitation of triacylglycerols in cellular lipid extracts: Requirement for presence of detergent and prior separation by thin-layer chromatography

A protocol, based on the use of Pseudomonas lipase, is presented to measure quantitatively the amount of triacylglycerols in extracts from cultured cells or tissues. Since the lipase also acts on di- and monoacylglycerols, separation of the extracts by thin-layer chromatography is recommended. In order to allow the lipase-catalyzed hydrolysis to proceed efficiently, lipid extracts or eluates from silica scraping were mixed with the detergent Thesit [dodecylpoly(ethylene glycol ether)], prior to drying. After dissolution of the dried residues in water, the amount of triacylglycerols was quantified using Pseudomonas sp. lipase, glycerol kinase, glycerol-phosphate oxidase, and peroxidase. The activity of the latter enzyme was followed either colorimetrically in the presence of 4-aminoantipyrine and 2,4,6-tribromo-3-hydroxybenzoic acid or fluorimetrically in the presence of homovanillic acid.     

Structural and Functional Characterization of 4-Hydroxyphenylacetate 3-Hydroxylase from Escherichia coli

The hydroxylation of phenols into polyphenols, which are valuable chemicals and pharmaceutical products, is a challenging reaction. The search for green synthetic processes has led to considering microorganisms and pure hydroxylases as catalysts for phenol hydroxylation. Herein, we report the structural and functional characterization of the flavin adenine dinucleotide (FAD)-dependent 4-hydroxyphenylacetate 3-monooxygenase from Escherichia coli, named HpaB. It is shown that this enzyme enjoys a relatively broad substrate specificity, which allows the conversion of a number of non-natural phenolic compounds, such as tyrosol, hydroxymandelic acid, coumaric acid, hydroxybenzoic acid and its methyl ester, and phenol, into the corresponding catechols. The reaction can be performed by using a simple chemical assay based on formate as the electron donor and the organometallic complex [Rh(bpy)Cp*(H₂O)]²⁺ (Cp*: 1,2,3,4,5-pentamethylcyclopentadiene, bpy: 2,2′-bipyridyl) as the catalyst for FAD reduction. The availability of a crystal structure of HpaB in complex with FAD at 1.8 Å resolution opens up the possibility of the rational tuning of the substrate specificity and activity of this interesting class of phenol hydroxylases.     

Limiting flux in skimmed milk ultrafiltration: impact of electrostatic repulsion due to casein micelles

The variations of the limiting flux during skimmed milk ultrafiltration were studied under various physicochemical environments (pH, ionic strength, chemical nature of added salts). The evolutions were explained taking into account the physicochemical characteristics (size distribution, zeta potential) of the casein micelles, that is the main components of the fouling layer formed at the membrane surface. It was shown than in the pH range from 5.6 to 6.7, the limiting flux was linearly related to the zeta potential of the casein micelles regardless of the way used to obtain the zeta potential variation (addition of HCl, CaCl₂ or NaH₂PO₄): the higher the zeta potential of casein micelles (neutral pH), the greater the limiting flux. Under these operating conditions, the variations of hydrophobic interactions were negligible. The variation of the permeability of the deposit layer, composed of retained casein micelles, was therefore mainly governed by electrostatic interactions due to the casein micelles.