Browsing by Subject "chromatography"

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Circular Dichroism of Multi-Component Assemblies for Chiral Amine Recognition and Rapid ee Determination
(2011-08) Metola, Pedro; Anslyn, Eric V.; James, Tony D.; Bull, Steven D.; Metola, Pedro; Anslyn, Eric V.
Upon mixing a chiral amine, enantiopure BINOL, and o-formyl phenyl boronic acid, the three components assemble efficiently and rapidly into chiral host-guest structures that produce distinct circular dichroism signals for each enantiomer of the amine. Employing BINOL and two derivatives to create an array of receptors, the CD signals resulting from several a-chiral primary amines were processed by principal component analysis and linear discriminant analysis to give satisfactory discrimination of the amines studied. Not only was the system able to differentiate the analytes chemoselectively and enantioselectively, but it also allowed for the rapid determination of chiral amine
Nitrogen nutrition of Alexandrium tamarense : using δ¹⁵N to track nitrogen source used for growth
(2009-05) Smith, Christa Belle; Erdner, Deana L.; Pease, Tamara Kaye; McClelland, James W.
Alexandrium tamarense is a harmful algal species that can produce saxitoxins, a suite of powerful neurotoxins that bioaccumulate up the food chain and can have severe economic and health impacts. With harmful algal blooms increasing temporally and spatially, it is important for us to understand the relationship between harmful algal blooms and nutrients, particularly nitrogen from anthropogenic sources. To this end, the stable nitrogen isotopic composition (δ¹⁵N) of medium nitrate, algal cells and toxin in both nitrogen-replete and nitrogen-limited batch cultures of A. tamarense were measured in order to assess the potential for using the δ¹⁵N of the toxin as a tracer of the nitrogen source used for growth. A. tamarense cells grown under nitrate-replete conditions were depleted by 1.5‰ relative to the growth medium, and saxitoxin was depleted by 1.5‰ relative to the whole cells. Under nitrate-limiting conditions, the isotopic difference between cells and saxitoxin changed as nitrate in the growth medium was depleted, indicating uncoupling of toxin synthesis and cell growth rates under changing external nutrient conditions. Determination of the absolute magnitude of the isotopic differences between the medium nitrate and either the cells or the saxitoxin was confounded by 1) using two different nitrate sources – one nitrate source was used to grow the inoculum and a different nitrate source was used for the experimental medium - with different ‰ values and 2) the presence of an unidentified, isotopically-light, nitrogen blank in the low-nitrate medium samples. I conclude that STX nitrogen isotope values have the potential to be used as nitrogen source indicators. However, overall fractionation between whole cells and STX is unknown due to the uncoupling between cell growth and STX synthesis observed during my nitrogen-limited experiment. Based on previous research on cell growth and toxin production dynamics under different nutrient regimes, it is also reasonable to assume that the observed results here may differ if a different nitrogen source was utilized by the cells for STX production. Further research could include isotope analysis of cultures grown on different nitrogen sources, such as ammonium and urea; isotopic analysis of additional compounds, such as amino acids; or use of additional stable isotopes, such as C or O.
A Selective and Sensitive Chromogenic and Fluorogenic Detection of a Sulfur Mustard Simulant
(2013-08) Kumar, Vinod; Anslyn, Eric V.; Kumar, Vinod; Anslyn, Eric V.
A simple and highly selective chromogenic and fluorogenic detection of sulfur mustard (SM) simulants is reported. Dithiol 1, in the presence and absence of a mustard simulant behaves differently toward a squaraine dye (SQ), and thus provides a visual and spectroscopic signal for mustard gas. The sensor responds to the SM simulant, but not to the O-analog of mustard stimulant or nerve agent mimics and other electrophilic agents. The visual and fluorescent detection with less than 50 mu M of SM simulant shows good sensitivity. The utility of the sensor was demonstrated by analysis of SM simulant on surfaces, in soil, and in the gas phase.