Leaves of many evergreen angiosperm species turn red under high light during winter due to the production of anthocyanin pigments, while leaves of other species remain green. There is currently no explanation for why some evergreen species exhibit winter reddening while others do not. Conditions associated with low leaf water potentials (Ψ) have been shown to induce reddening in many plant species. Because evergreen species differ in susceptibility to water stress during winter, it is hypothesized that species which undergo winter colour change correspond with those that experience/tolerate the most severe daily declines in leaf Ψ during winter. Six angiosperm evergreen species which synthesize anthocyanin in leaves under high light during winter and five species which do not were studied. Field Ψ, pressure/volume curves, and gas exchange measurements were derived in summer (before leaf colour change had occurred) and winter. Consistent with the hypothesis, red-leafed species as a group had significantly lower midday Ψ in winter than green-leafed species, but not during the summer when all the leaves were green. However, some red-leafed species showed midday declines similar to those of green-leafed species, suggesting that low Ψ alone may not induce reddening. Pressure–volume curves also provided some evidence of acclimation to more negative water potentials by red-leafed species during winter (e.g. greater osmotic adjustment and cell wall hardening on average). However, much overlap in these physiological parameters was observed as well between red and green-leafed species, and some of the least drought-acclimated species were red-leafed. No difference was observed in transpiration (E) during winter between red and green-leaved species. When data were combined, only three of the six red-leafed species examined appeared physiologically acclimated to prolonged drought stress, compared to one of the five green-leafed species. This suggests that drought stress alone is not sufficient to explain winter reddening in evergreen angiosperms.
A dicationic ion-pairing reagent, N,N'-dibutyl 1,1'-pentylenedipyrrolidinium, was used to form complexes with singly charged anions for their subsequent analysis by CE-ESI-MS in positive ion mode. This methodology offers the advantages of greater versatility and sensitivity relative to direct detection of the anions in negative ion mode, and it can be realized by a number of possible complexation strategies, including pre-column, on-column, and post-column modes. Four model anions, perfluorooctanoate, benzenesulfonate (BZSN), monochloroacetate (MCA), and trifluoromethanesulfonimide were amenable to complexation with the dicationic reagent, yielding singly charged cations with greater m/z. By optimizing various parameters, including the CE separation buffer composition and pH, the concentration of the dicationic reagent, the mode of complexation, the nebulizing gas pressure, and the sheath liquid composition, it was possible to develop a robust CE-ESI-MS method appropriate for the analysis of anions in a tap water sample. By this method, LODs were found to be 20.9 and 1.31 ng/mL for MCA and BZSN, respectively.
Mismatch repair proteins modulate the cytotoxicity of several chemotherapeutic agents. We have recently proposed a “death conformation” of the MutS homologous proteins that is distinguishable from their “repair conformation.” This conformation can be induced by a small molecule, reserpine, leading to DNA-independent cell death. We investigated the parameters for a small reserpine-like molecule that are required to interact with MSH2/MSH6 to induce MSH2/MSH6-dependent cytotoxic response. A multidisciplinary approach involving structural modeling, chemical synthesis, and cell biology analyzed reserpine analogs and modifications. We demonstrate that the parameters controlling the induction of MSH2/MSH6-dependent cytotoxicity for reserpine-analogous molecules reside in the specific requirements for methoxy groups, the size of the molecule, and the orientation of molecules within the protein-binding pocket. Reserpine analog rescinnamine showed improved MSH2-dependent cytotoxicity. These results have important implications for the identification of compounds that require functional MMR proteins to exhibit their full cytotoxicity, which will avoid resistance in MMR-deficient cells.
SUMMARYSeveral approaches were explored to develop a high throughput procedure for relative determination of 14 different carbon-centered free radicals, both acyl and alkylaminocarbonyl type, in cigarette smoke. Two trapping procedures using 3-cyano-2,2,5,5-tetramethyl-1-pyrrolidinyloxy, or 3-cyanoproxyl radical (3-CNP) were designed for this study: a) trapping in solution and b) trapping on a solid support which was a Cambridge filter pad. Fresh whole smoke and vapor phase smoke from mainstream cigarette smoke from Kentucky Reference Cigarettes 2R4F, as partitioned via an unadulterated Cambridge filter pad, were transferred into each trapping system in separate experiments. The 3-CNP coated Cambridge filter pad approach was shown to be superior to the impinger procedure as described in this study. Gas chromatography coupled with mass selective detection (GC-MS) was employed for the first time as an alternate means of detecting several relatively highly concentrated radical adducts. Liquid chromatography tandem mass spectrometry (LC-MS/MS) with precursor ion monitoring and selected ion monitoring (SIM) was used for detecting the large array of radicals, including several not previously reported: formyl, crotonyl, acrolein, aminocarbonyl, and anilinocarbonyl radicals. Relative quantitation was achieved using as external calibration standards of 4-(1-pyrrolidino)benzaldehyde and nicotine. It was determined that the yield of carbon-centered free radicals by reference cigarette 2R4F was approximately 265 nmoles/cigarette at 35 mL puff/60 sec interval/2 sec duration smoking conditions. [Beitr. Tabakforsch Experimenten in das jeweilige Auffangsystem geleitet. Bei den hier beschriebenen Verfahren, war der Ansatz mit 3 RESUMEPlusieurs approches ont été explorées pour développer une procédure à haute performance pour la détermination relative de 14 radicaux libres centrés sur le carbone, de type à la fois acyle et alkyle aminocarbonyle, dans la fumée de cigarette. Deux procédés de piégeage utilisant le 3-cyano-2,2,5,5-tétraméthyl-1-pyrrolidinyloxy, ou le radical 3-cyanoproxyl (3-CNP) ont été conçus pour cette étude: a) le piégeage dans une solution et b) le piégeage sur un support solide à savoir un tampon-filtre Cambridge. La totalité de la fumée fraîche et la fumée en phase vapeur de la fumée principale des cigarettes de référence Kentucky 2R4F, telles que séparées par un tampon-filtre Cambridge non modifié ont été transférées à un système de piégeage lors d'expériences distinctes. L'approche avec le filtre Cambridge enduit de 3-CNP s'est avérée supérieure à la procé-dure avec impacteur telle que décrite dans cette étude. La chromatographie en phase gazeuse avec détection sélective de masse (GC-MS) a été employée pour la première fois comme méthode alternative de détection de plusieurs adduits radicaux de concentration relativement élevée. La chromatologie phase liquide couplée à la spectrométrie de masse en tandem (LC-MS/MS) avec un contrôle des ions précurseurs et un contrôle des ions sélectionnés (SIM) a été utilisé...
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