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I.e. N (i.e + n)
Selected AbstractsOxidation of phenols by laccase and laccase-mediator systemsFEBS JOURNAL, Issue 21 2002Solubility, steric issues To investigate how solubility and steric issues affect the laccase-catalysed oxidation of phenols, a series of oligomeric polyphenol compounds, having increasing size and decreasing solubility in water, was incubated with laccase. The extent of substrate conversion, and the nature of the products formed in buffered aqueous solutions, were compared to those obtained in the presence of an organic cosolvent, and also in the presence of two mediating species, i.e. N -hydroxyphthalimide (HPI) and 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO). This approach showed not only an obvious role of solubility, but also a significant role of the dimension of the substrate upon the enzymatic reactivity. In fact, reactivity decreases as substrate size increases even when solubility is enhanced by a cosolvent. This effect may be ascribed to limited accessibility of encumbered substrates to the enzyme active site, and can be compensated through the use of the appropriate mediator. While TEMPO was highly efficient at enhancing the reactivity of large, less soluble substrates, HPI proved less effective. In addition, whereas the laccase/HPI system afforded the same products as laccase alone, the use of TEMPO provided a different product with high specificity. These results offer the first evidence of the role of ,oxidation shuttles' that the mediators of laccase may have, but also suggest two promising routes towards an environmentally friendly process for kraft pulp bleaching: (a) the identification of mediators which, once oxidized by laccase, are able to target strategic functional groups present in lignin, and (b) the introduction of those strategic functional groups in an appropriate pretreatment. [source] Products of tryptophan catabolism induce Ca2+ release and modulate the cell cycle of Plasmodium falciparum malaria parasitesJOURNAL OF PINEAL RESEARCH, Issue 3 2005Flávio H. Beraldo Abstract:, Intraerythrocytic malaria parasites develop in a highly synchronous manner. We have previously shown that the host hormone melatonin regulates the circadian rhythm of the rodent malaria parasite, Plasmodium chabaudi, through a Ca2+ -based mechanism. Here we show that melatonin and other molecules derived from tryptophan, i.e. N -acetylserotonin, serotonin and tryptamine, also modulate the cell cycle of human malaria parasite P. falciparum by inducing an increase in cytosolic free Ca2+. This occurs independently of the extracellular Ca2+ concentration, indicating that these molecules induce Ca2+ mobilization from intracellular stores in the trophozoite. This in turn leads to an increase in the proportion of schizonts. The effects of the indolamines in increasing cytosolic free Ca2+ and modulating the parasite cell cycle are both abrogated by an antagonist of the melatonin receptor, luzindole, and by the phospholipase inhibitor, U73122. [source] Screening for mild cognitive impairment: a systematic reviewINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 9 2009Jane A. Lonie Abstract Objective Patients with mild cognitive impairment account for a significant number of referrals to old age psychiatry services and specialist memory clinics. The cognitive evaluation of such patients is commonly restricted to brief dementia screens, with no consideration to their suitability for assessing MCI. Here, we review the utility of such cognitive screens for MCI and provide an overview of validated instruments. Methods We identified papers published after Petersen and colleagues 1999 MCI criteria (Petersen et al., 1999) and examining face-to-face cognitive screening for MCI from publication databases using combinations of the search terms ,mild cognitive impairment' and ,cognitive screening'. We also combined the former search with the names of 39 screening tests recently identified in a relevant review (Cullen et al., 2007). Results Fifteen cognitive screening instruments were identified, 11 cover a restricted range of cognitive domains. High sensitivity and specificity for MCI relative to healthy controls were reported for two comprehensive and two noncomprehensive screening instruments, adequate test-retest and inter-rater reliability for only one of these. With the exception of three studies, sample sizes were universally small (i.e. n,,,100), and prognostic values were reported for only two of the identified 15 screening measures. Sensitivities of the full domain measures were universally high, but information about their specificity against psychiatric and non-progressive neurological conditions and predictive validity is lacking. Conclusion Several cognitive screening instruments afford the clinician the ability to detect MCI, early AD, and in some cases non-AD dementia, but they cannot currently be used to make reliable inferences about the course and eventual outcome of MCI. Copyright © 2009 John Wiley & Sons, Ltd. [source] Suppression of Root Rotting Fungi and Root Knot Nematode of Chili by Seaweed and Pseudomonas aeruginosaJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2008V. Sultana Abstract Solvent fractions (i.e. n -hexane, chloroform and methanol) of the ethanol extracts of the seaweeds Codium iyengarii, Jania capillacea, Stokeyia indica and Solieria robusta caused more than 50% mortality of Meloidogyne javanica juveniles within 24 h at 10 mg/ml. Nematode mortality increased with an increase in fraction concentration or exposure time. The n -hexane fractions from S. indica, J. capillacea and C. iyengarii and the chloroform fraction from S. robusta also resulted in more than 50% mortality within 48 h at 1.0 mg/ml. In a screen-house experiment application of S. indica and S. robusta as soil amendments alone or with Pseudomonas aeruginosa, a plant growth promoting rhizobacterium (PGPR), significantly suppressed infection of chili roots by root-infecting fungi Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and the root knot nematode Meloidogyne javanica. Seaweed alone or with PGPR also increased plant growth. Suppressive effect on root pathogens and growth enhancement potential of seaweeds and P. aeruginosa were also effective in field plots. [source] Block copolymer preparation by atom transfer radical polymerization under emulsion conditions using a nanoprecipitation techniqueJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008Delphine Chan-Seng Abstract Living-radical polymerization of acrylates were performed under emulsion atom transfer radical polymerization (ATRP) conditions using latexes prepared by a nanoprecipitation technique previously employed and optimized for the polymerization of styrene. A macroinitiator of poly(n -butyl acrylate) prepared under bulk ATRP was dissolved in acetone and precipitated in an aqueous solution of Brij 98 to preform latex particles, which were then swollen with monomer and heated. Various monomers (i.e. n -butyl acrylate, styrene, and tert -butyl acrylate) were used to swell the particles to prepare homo- and block copolymers from the poly(n -butyl acrylate) macroinitiator. Under these conditions latexes with a relatively good colloidal stability were obtained. Furthermore, amphiphilic block copolymers were prepared by hydrolysis of the tert -butyl groups and the resulting block copolymers were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The bulk morphologies of the polystyrene- b -poly(n -butyl acrylate) and poly(n -butyl acrylate)- b -poly(acrylic acid) copolymers were investigated by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 625,635, 2008 [source] | ||||||||||