Hydrophysical correlation and water mass indication of optical physiological parameters of picophytoplankton in Prydz Bay during autumn 2008

Flow cytometry (FCM) is efficient in detecting both abundance and optical physiological parameters including cell size and cellular carbon content—side scatter (SSC), carotenoids—green and orange fluorescence (FL1 and FL2), and red fluorescence—chlorophylls (FL3) can be obtained by FCM. The utilization of these physiological parameters in indicating water masses in Prydz Bay was investigated for the first time. Picophytoplankton were very sensitive to hydrophysical changes and present distinct characteristics of water masses: Picophytoplankton in water closer to the Amery Ice Shelf were more affected by salinity than by temperature, while temperature became more important than salinity the nearer the picophytoplankton were to the deep sea. The picophytoplankton dealt with declines in light by increasing the size of cells, which increase the fixation of carbon. This can also be increased by high temperature and salinity. Pure water masses can increase the content of chlorophylls and cellular carbon. Generally, the distributions of all the five parameters at upper water depths were less affected by temperature and salinity than by water masses; and these parameters can be as indicators to Summer Surface Water (SSW), Winter Water (WW) and Continental Shelf Water (CSW).     

Reproductive function of Selenoprotein M in Chinese mitten crabs (Eriocheir sinesis)

Selenoproteins are present in all major forms of life, including eukaryotes, bacteria and archaea. In eukaryotic animals, selenoproteins often function as antioxidants, but rare or absent in other phyla, such as plants and fungi (except for the green alga Chlamydomonas). Selenoprotein M (SelM) is a selenocysteine containing protein with redox activity, which is involved in the antioxidant response. However, information remains limited about SelM physiology and function in marine invertebrates, particularly in crustaceans. Hence, we investigated the reproductive functionality of SelM in the Chinese mitten crab (Eriocheir sinensis), which is a commercially important yet disease vulnerable aquaculture species. The full-length SelM cDNA (928bp) strand was cloned by using PCR, based on an initial expressed sequence tag (EST) that was isolated from a hepatopancreatic cDNA library. The SelM cDNA contained a 390bp open reading frame (ORF) that encoded a putative 129 amino acid (aa) protein. SelM mRNA expression in E. sinensis was (a) tissue-specific, with the highest expression observed in the hepatopancreas, testis, ovaries and intestines. Based on this information, we then detected the different stages of tissue expression for SelM in the testis, ovary, and male crab hepatopancreas and hemolymph, and the enzyme activity of SelM in the testis. Overall, SelM was isolated successfully from the Chinese mitten crab, and its involvement in the regulation of reproduction during the period of rapid development in E. sinensis was confirmed.     

Role of myosin Va in purinergic vesicular neurotransmission in the gut

We examined the hypothesis that myosin Va, by transporting purinergic vesicles to the varicosity membrane for exocytosis, plays a key role in purinergic vesicular neurotransmission. Studies were performed in wild-type (WT) and myosin Va-deficient dilute, brown, nonagouti (DBA) mice. Intracellular microelectrode recordings were made in mouse antral muscle strips. Purinergic inhibitory junction potential (pIJP) was recorded under nonadrenergic noncholinergic conditions after masking the nitrergic junction potentials. DBA mice showed reduced pIJP but normal hyperpolarizing response to P2Y1 receptor agonist MRS-2365. To investigate the mechanism of reduced purinergic transmission in DBA mice, studies were performed in isolated varicosities obtained from homogenates of whole gut tissues by ultracentrifugation and sucrose cushion purification. Purinergic varicosities were identified in tissue sections and in isolated varicosities by immunostaining for the vesicular ATP transporter, the solute carrier protein SLC17A9. The varicosities were similar in WT and DBA mice. Myosin Va was markedly reduced in DBA varicosities compared with the WT varicosities. Proximity ligation assay showed that myosin Va was closely associated with SLC17A9. Vesicular exoendocytosis was examined by FM1-43 staining of varicosities, which showed that exoendocytosis after KCl stimulation was impaired in DBA varicosities compared with WT varicosities. These studies show that SLC17A9 identifies ATP-containing purinergic varicosities. Myosin Va associates with SLC17A9-stained vesicles and possibly transports them to varicosity membrane for exocytosis. In myosin Va-deficient mice, purinergic inhibitory neurotransmission is impaired.     

Improved efficiency in cryo-em secondary structure topology determination from inaccurate data

The determination of the secondary structure topology is a critical step in deriving the atomic structure from the protein density map obtained from electron cryo-microscopy technique. This step often relies on the matching of two sources of information. One source comes from the secondary structures detected from the protein density map at the medium resolution, such as 5-10 ?. The other source comes from the predicted secondary structures from the amino acid sequence. Due to the inaccuracy in either source of information, a pool of possible secondary structure positions needs to be sampled. This paper studies the question, that is, how to reduce the computation of the mapping when the inaccuracy of the secondary structure predictions is considered. We present a method that combines the concept of dynamic graph with our previous work of using constrained shortest path to identify the topology of the secondary structures. We show a reduction of 34.55% of run-time as comparison to the na?ve way of handling the inaccuracies. We also show an improved accuracy when the potential secondary structure errors are explicitly sampled verses the use of one consensus prediction. Our framework demonstrated the potential of developing computationally effective exact algorithms to identify the optimal topology of the secondary structures when the inaccuracy of the predicted data is considered.     

SulE, a sulfonylurea herbicide de-esterification esterase from Hansschlegelia zhihuaiae S113

De-esterification is an important degradation or detoxification mechanism of sulfonylurea herbicide in microbes and plants. However, the biochemical and molecular mechanisms of sulfonylurea herbicide de-esterification are still unknown. In this study, a novel esterase gene, sulE, responsible for sulfonylurea herbicide de-esterification, was cloned from Hansschlegelia zhihuaiae S113. The gene contained an open reading frame of 1,194 bp, and a putative signal peptide at the N terminal was identified with a predicted cleavage site between Ala37 and Glu38, resulting in a 361-residue mature protein. SulE minus the signal peptide was synthesized in Escherichia coli BL21 and purified to homogeneity. SulE catalyzed the de-esterification of a variety of sulfonylurea herbicides that gave rise to the corresponding herbicidally inactive parent acid and exhibited the highest catalytic efficiency toward thifensulfuron-methyl. SulE was a dimer without the requirement of a cofactor. The activity of the enzyme was completely inhibited by Ag(+), Cd(2+), Zn(2+), methamidophos, and sodium dodecyl sulfate. A sulE-disrupted mutant strain, ΔsulE, was constructed by insertion mutation. ΔsulE lost the de-esterification ability and was more sensitive to the herbicides than the wild type of strain S113, suggesting that sulE played a vital role in the sulfonylurea herbicide resistance of the strain. The transfer of sulE into Saccharomyces cerevisiae BY4741 conferred on it the ability to de-esterify sulfonylurea herbicides and increased its resistance to the herbicides. This study has provided an excellent candidate for the mechanistic study of sulfonylurea herbicide metabolism and detoxification through de-esterification, construction of sulfonylurea herbicide-resistant transgenic crops, and bioremediation of sulfonylurea herbicide-contaminated environments.     

Protective role of mucilage against Al toxicity to root apex of pea (Pisum sativum)

Mucilage can strongly bind Al in the rhizosphere. Although there are still debates about the role of mucilage in protection of the root apex from Al toxicity, we considered that it might be associated with the characteristics of Al adsorption in mucilage. When the mucilage was kept intact, the accumulation of Al and induction of callose in root tips of pea (Pisum sativum) remained lower; thus root elongation was less inhibited than when mucilage was removed under Al exposure in mist culture. Size exclusion chromatography showed both a high and a low molecular weight polysaccharide fraction from root mucilage. Aluminum was predominately detected in high molecular weight polysaccharides, which strongly bound cations. The results indicate that the persistence of mucilage does protect the root apex from Al toxicity by immobilizing Al in high molecular weight polysaccharides.     

Modification of hydroxypropyl guar gum with ethanolamine

A new guar gum derivative containing amino group was synthesized through nucleophilic substitution of p-toluenesulfonate activated hydroxypropyl guar gum with ethanolamine. For the preparation of p-toluenesulfonate esters hydroxypropyl guar gum, the results showed that the reaction rate was optimal at 25°C and the reaction could reach equilibrium state when it was carried out for 10h at 25°C. For the nucleophilic substitution of tosyl group with ethanolamine, the reaction was completed after 10h reaction at 50°C. The structures of products were characterized by NMR and FT-IR spectroscopy. The results showed that the p-toluenesulfonate esters can be effectively substituted by ethanolamine to form the hydroxyethyl amino hydroxypropyl guar gum (EAHPG). The content of nitrogen of EAHPG was determined by acid-base titration and element analysis.