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Plants growing in heavy-metal-rich soils can accumulate metals into their nectar. Nectar chemical composition can alter foraging behavior of floral visitors (including pollinators and floral antagonists) and further affect plant reproductive fitness. The role of nectar heavy metals in deterring pollinators (e.g., shortening foraging time) has been recently studied, but their effects on plant reproduction via changes in behaviors of both pollinators and floral antagonists (e.g., nectar robbers) are less understood. We experimentally manipulated four nectar heavy metals (Zn, Cu, Ni, and Pb) in a native ornamental plant, Hosta ensata F. Maekawa, to investigate the effect of nectar metals on plant reproductive success. We also recorded nectar robbing as well as foraging time and visitation rate of pollinators to assess whether nectar metals could alter the behavior of antagonists and mutualists. Although metals in nectar had no significant direct effects on plant reproduction via hand-pollination, we detected their positive indirect effects on components of female fitness mediated by pollinators and nectar robbers. Matching effects on female plant fitness, nectar robbers responded negatively to the presence of metals in nectar, robbing metal-treated flowers less often. Pollinators spent less time foraging on metal-treated flowers, but their visitation rate to metal-treated flowers was significantly higher than to control flowers. Moreover, pollinators removed less nectar from flowers treated with metals. Our results provide the first direct evidence to date that heavy metals in nectar are capable of deterring nectar robbers and modifying pollinator foraging behavior to enhance plant reproductive fitness.

Metals and metalloids in soil could be transferred into reproductive organs and floral rewards of hyperaccumulator plants and influence their reproductive success, yet little is known whether non-hyperaccumulator plants can translocate heavy metals from soil into their floral organs and rewards (i.e., nectar and pollen) and, if so, whether plant reproduction will be affected. In our studies, summer squash (Cucurbita pepo L. cv. Golden Apple) was exposed to heavy-metal treatments during bud stage to investigate the translocation of soil-supplemented zinc, copper, nickel and lead into its floral organs (pistil, anther and nectary) and rewards (nectar and pollen) as well as floral metal accumulation effects on its reproduction. The results showed that metals taken up by squash did translocate into its floral organs and rewards, although metal accumulation varied depending on different metal types and concentrations as well as floral organ/reward types. Mean foraging time of honey bees to each male and female flower of squash grown in metal-supplemented soils was shorter relative to that of plants grown in control soils, although the visitation rate of honeybees to both male and female flowers was not affected by metal treatments. Pollen viability, pollen removal and deposition as well as mean mass per seed produced by metal-treated squash that received pollen from plants grown in control soils decreased with elevated soil-supplemented metal concentrations. The fact that squash could translocate soil-supplemented heavy metals into floral organs and rewards indicated possible reproductive consequences caused either directly (i.e., decreasing pollen viability or seed mass) or indirectly (i.e., affecting pollinators' visitation behavior to flowers) to plant fitness.

BACKGROUND (S)-2-(2-chloro-1-hydroxyethyl) thiophene is one of the most important intermediates for the synthesis of (S)-duloxetine. The preparation of (S)-2-(2-chloro-1-hydroxyethyl) thiophene could be realized from its racemate via enzymatic resolution. This study aimed to prepare an easy-recycling immobilized lipase with excellent performance and use it to obtain (S)-2-(2-chloro-1-hydroxyethyl) thiophene with high enantiometric purity through enzymatic enantioselective transesterificaion in organic media. To achieve this, immobilization of the lipase and the effects of different reaction conditions (e.g. organic solvent, water activity, substrate ratio and temperature) on the activity and enantioselectivity of the lipase were investigated. RESULTS Lipase from Alcaligenes sp. (lipase QL) was successfully immobilized onto the prepared magnetic Fe3O4 nanoparticles through hydrophobic interaction, and the enzyme loading (97.4 ± 2.3 mg g−1) as well as immobilization yield (48.7 ± 1.4%) was obtained. Under optimum reaction conditions, the higher enzyme activity (0.225 ± 0.01 µmol mg−1 min−1) and enantioselectivity (E-value: 59.7 ± 1.8) for the immobilized lipase QL than those (enzyme activity: 0.034 ± 0.002 µmol mg−1 min−1, E-value: 57.9 ± 2.0) for aggregated lipase was observed. The results also showed that (S)-2-(2-chloro-1-hydroxyethyl) thiophene with optical purity ≥99% was obtained. In addition, the immobilized lipase QL was easily separated from the reaction media by magnetic steel, and maintained 90% of its initial activity with nearly unchanged enantioselectivity after five consecutive cycles. CONCLUSION The results obtained demonstrated good potential for practical application of magnetic nanoparticle-immobilized lipase for the resolution of 2-(2-chloro-1-hydroxyethyl) thiophene through enantioselective transesterification. © 2014 Society of Chemical Industry

BACKGROUND: The enantiomers of N-hydroxymethyl vince lactam are important intermediates during the synthesis of chiral drugs. The preparation of its single enantiomer can be performed through enzymatic resolution. The aim of this work is to obtain (1S ,4 R)-N-hydroxymethyl vince lactam with high enantiomeric purity via lipase-catalyzed enantioselective transesterification in organic solvents. To achieve this, effects of various reaction conditions (including lipase sources, acyl donor, substrate molar ratio, organic solvent, temperature, and water activity) on the enzyme activity as well as enantioselectivity were investigated. RESULTS: The results of the study showed that the enantiopreference for all the selected enzymes was (4S ,1 R)-N-hydroxymethyl vince lactam in enantioselective transesterification of racemic N-hydroxymethyl vince lactam. Under the selected optimum conditions, the highest enantioselectivity (E = 33.8) was obtained with a higher enzyme activity (20.3 µmol g −1 min −1 )f or Mucor miehei lipase (MML) when vinyl valerate was used as the acyl donor. Besides, the remained (1S ,4 R)-N-hydroxymethyl vince lactam with high enantiomeric purity (ee > 99%) was obtained when the conversion was about 60%. CONCLUSION: The results obtained clearly demonstrated potential for industrial application of lipase in resolution of N-hydroxymethyl vince lactam through enantioselective transesterification. c � 2012 Society of Chemical Industry

Aeropyrum pernix esterase (APE1547) was successfully used to catalyze the enantioselective transesterification of (R/S)-2-methyl-1-butanol in an ionic liquid (IL). Effects of various reaction conditions on the synthetic activity of the enzyme as well as enantioselectivity, including the type of IL, acyl donor, temperature, water activity, and substrate molar ratio were inverstigated. APE1547 showed good catalytic performance (activity > 0.8 μmol/min/mg, E > 25), and the enzyme-IL mixture was recycled five times with only a slight decrease in catalytic performance.

The lipase from Pseudomonas fluorescens (Lipase AK, AKL) was immobilized onto the magnetic Fe3O4 nanoparticles via hydrophobic interaction. Enzyme loading and immobilization yield were determined as 21.4 ± 0.5 mg/g and 49.2 ± 1.8 %, respectively. The immobilized AKL was successfully used for resolution of 2-octanol with vinyl acetate used as acyl donor. Effects of organic solvent, water activity, substrate ratio, and temperature were investigated. Under the optimum conditions, the preferred isomer for AKL is the (R)-2-octanol and the highest enantioselectivity (E = 71.5 ± 2.2) was obtained with a higher enzyme activity (0.197 ± 0.01 μmol/mg/min). The results also showed that the immobilized lipase could be easily separated from reaction media by the magnetic steel and remained 89 % of its initial activity as well as the nearly unchanged enantioselectivity after five consecutive cycles, indicating a high stability in practical operation.