Performance of slotted pores in particle manufacture using rotating membrane emulsification

This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.     

Reinforcing Isotope and Atomic-Weight Concepts in General Chemistry Using Internet-Based Mass-Spectral Data

This paper describes how isotope and atomic-weight concepts are enhanced for students using mass-spectral data from interactive Internet sites. The class considers mass spectra for compounds containing only monoisotopic elements and later for polyisotopic elements. Students calculate molecular weights based on data they acquire from mass spectra on the Internet.     

Amberlyst-15 Catalyzed Addition of Phenols to α,β-Unsaturated Ketones

Amberlyst-15 has been used to catalyze regioselective additions of phenols to α,β-unsaturated ketones in yields of 20–90%. The reaction is superior to the analogous reaction employing concentrated sulfuric acid in affording greater yields and purer products with a minimum of laboratory operations.     

Differential effects of FR900482 and FK317 on apoptosis, IL-2 gene expression, and induction of vascular leak syndrome

Vascular leak syndrome (VLS) is a harmful side effect that resulted in withdrawal of the antitumor drug FR900482, but not FK317, from clinical trials. Here we present chromatin immunoprecipitation data showing that FK317, like FR900482, crosslinks minor-groove binding proteins to DNA in vivo. However, these drugs differ in how they induce cell death. We demonstrate that, whereas FR900482 induces necrosis, FK317 induces a necrosis-to-apoptosis switch that is drug concentration dependent. Northern blot analyses of drug-treated cells suggest that this "switch" is mediated, at least in part, by modulation of the expression levels of Bcl-2. Additionally, FR900482, in contrast to FK317, induces the expression of known elicitors of both Bcl-2 gene expression and VLS. These findings provide plausible explanations for why these structurally similar drugs have different biological effects, especially with respect to VLS.     

Closed loop folding units from structural alignments: Experimental foldons revisited

Nonoverlapping closed loops of around 25–35 amino acids formed via nonlocal interactions at the loop ends have been proposed as an important unit of protein structure. This hypothesis is significant as such short loops can fold quickly and so would not be bound by the Leventhal paradox, giving insight into the possible nature of the funnel in protein folding. Previously, these closed loops have been identified either by sequence analysis (conservation and autocorrelation) or studies of the geometry of individual proteins. Given the potential significance of the closed loop hypothesis, we have explored a new strategy for determining closed loops from the insertions identified by the structural alignment of proteins sharing the same overall fold. We determined the locations of the closed loops in 37 pairs of proteins and obtained excellent agreement with previously published closed loops. The relevance of NMR structures to closed loop determination is briefly discussed. For cytochrome c, cytochrome b₅₆₂ and triosephophate isomerase, independent folding units have been determined on the basis of hydrogen exchange experiments and misincorporation proton‐alkyl exchange experiments. The correspondence between these experimentally derived foldons and the theoretically derived closed loops indicates that the closed loop hypothesis may provide a useful framework for analyzing such experimental data. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Directed Evolution of a Thermophilic β-glucosidase for Cellulosic Bioethanol Production

Characteristics that would make enzymes more desirable for industrial applications can be improved using directed evolution. We developed a directed evolution technique called random drift mutagenesis (RNDM). Mutant populations are screened and all functional mutants are collected and put forward into the next round of mutagenesis and screening. The goal of this technique is to evolve enzymes by rapidly accumulating mutations and exploring a greater sequence space by providing minimal selection pressure and high-throughput screening. The target enzyme was a β-glucosidase isolated from the thermophilic bacterium, Caldicellulosiruptor saccharolyticus that cleaves cellobiose resulting from endoglucanase hydrolysis of cellulose. Our screening method was fluorescence-activated cell sorting (FACS), an attractive method for assaying mutant enzyme libraries because individual cells can be screened, sorted into distinct populations and collected very rapidly. However, FACS screening poses several challenges, in particular, maintaining the link between genotype and phenotype because most enzyme substrates do not remain associated with the cells. We employed a technique where whole cells were encapsulated in cell-like structures along with the enzyme substrate. We used RNDM, in combination with whole cell encapsulation, to create and screen mutant β-glucosidase libraries. A mutant was isolated that, compared to the wild type, had higher specific and catalytic efficiencies (k _cat/K _M) with p-nitrophenol-glucopyranoside and -galactopyranoside, an increased catalytic turnover rate (k _cat) with cellobiose, an improvement in catalytic efficiency with lactose and reduced inhibition (K _i) with galactose and lactose. This mutant had three amino acid substitutions and one was located near the active site.     

The preparation of certified calibration solutions for azaspiracid-1, -2, and -3, potent marine biotoxins found in shellfish

The production and certification of a series of azaspiracid (AZA) calibration solution reference materials is described. Azaspiracids were isolated from contaminated mussels, purified by preparative liquid chromatography and dried under vacuum to the anhydrous form. The purity was assessed by liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The final concentration of each AZA in a CD₃OH stock solution was determined by quantitative NMR spectroscopy. This solution was then diluted very accurately in degassed, high purity methanol to a concentration of 1.47?±?0.08 μmol/L for CRM-AZA1, 1.52?±?0.05 μmol/L for CRM-AZA2, and 1.37?±?0.13 μmol/L for CRM-AZA3. Aliquots were dispensed into argon-filled glass ampoules, which were immediately flame-sealed. The calibration solutions are suitable for method development, method validation, calibration of liquid chromatography or mass spectrometry instrumentation and quality control of shellfish monitoring programs.     

Device quality ZnO grown using a Filtered Cathodic Vacuum Arc

In this paper we report on the structural, electrical and optical characteristics of unintentionally doped ZnO films grown on a-plane sapphire substrates using the Filtered Cathodic Vacuum Arc (FCVA) technique. The resulting films showed considerable promise for device applications with properties including high transparency, moderate intrinsic carrier concentrations (10¹⁷–10¹⁹ cm⁻³), electron mobilities up to 30 cm²/Vs, low surface roughness (typically <2% of film thickness) and well-structured photoluminescence. Post-annealing in oxygen at temperatures up to 800 °C produced significant improvements in the properties of these films. Silver oxide Schottky diodes fabricated on FCVA ZnO showed ideality factors as low as 1.20 and good sensitivity to ultraviolet light.     

Anthocyanins and their variation in red wines I. Monomeric anthocyanins and their color expression

Originating in the grapes, monomeric anthocyanins in young red wines contribute the majority of color and the supposed beneficial health effects related to their consumption, and as such they are recognized as one of the most important groups of phenolic metabolites in red wines. In recent years, our increasing knowledge of the chemical complexity of the monomeric anthocyanins, their stability, together with the phenomena such as self-association and copigmentation that can stabilize and enhance their color has helped to explain their color representation in red wine making and aging. A series of new enological practices were developed to improve the anthocyanin extraction, as well as their color expression and maintenance. This paper summarizes the most recent advances in the studies of the monomeric anthocyanins in red wines, emphasizing their origin, occurrence, color enhancing effects, their degradation and the effect of various enological practices on them.