|
|
|
|
|
|
Disposition and Metabolic Profiles of [14C]Viramidine and [14C]Ribavirin in Rat and Monkey Red Blood Cells and Liver. Chin-Chung Lin, 2004.The disposition and metabolic profiles of [14C]viramidine and [14C]ribavirin were compared in rat and monkey red blood cells and liver . Our data reveal that the total ribavirin-related components (ribavirin plus its mono-, di-, and triphosphate metabolites) may account for most of the drug in monkey liver following prolonged oral administration of viramidine . Construction of a Xylan-Fermenting Yeast Strain through Codisplay of Xylanolytic Enzymes on the Surface of Xylose-Utilizing Saccharomyces cerevisiae Cells. Satoshi Katahira, 2004.Hemicellulose is one of the major forms of biomass in lignocellulose, and its essential component is xylan . We used a cell surface engineering system based on  -agglutinin to construct a Saccharomyces cerevisiae yeast strain codisplaying two types of xylan-degrading enzymes, namely, xylanase II (XYNII) from Trichoderma reesei QM9414 and ß-xylosidase (XylA) from Aspergillus oryzae NiaD300, on the cell surface . In a high-performance liquid chromatography analysis, xylose was detected as the main product of the yeast strain codisplaying XYNII and XylA, while xylobiose and xylotriose were detected as the main products of a yeast strain displaying XYNII on the cell surface . These results indicate that xylan is sequentially hydrolyzed to xylose by the codisplayed XYNII and XylA . In a further step toward achieving the simultaneous saccharification and fermentation of xylan, a xylan-utilizing S . cerevisiae strain was constructed by codisplaying XYNII and XylA and introducing genes for xylose utilization, namely, those encoding xylose reductase and xylitol dehydrogenase from Pichia stipitis and xylulokinase from S . cerevisiae . After 62 h of fermentation, 7.1 g of ethanol per liter was directly produced from birchwood xylan, and the yield in terms of grams of ethanol per gram of carbohydrate consumed was 0.30 g/g . These results demonstrate that the direct conversion of xylan to ethanol is accomplished by the xylan-utilizing S . cerevisiae strain .
YqfS from Bacillus subtilis Is a Spore Protein and a New Functional Member of the Type IV Apurinic/Apyrimidinic-Endonuclease Family. José M. Salas-Pacheco, 2003.The enzymatic properties and the physiological function of the type IV apurinic/apyrimidinic (AP)-endonuclease homolog of Bacillus subtilis, encoded by yqfS, a gene specifically expressed in spores, were studied here . To this end, a recombinant YqfS protein containing an N-terminal His6 tag was synthesized in Escherichia coli and purified to homogeneity . An anti-His6-YqfS polyclonal antibody exclusively localized YqfS in cell extracts prepared from B . subtilis spores . The His6-YqfS protein demonstrated enzymatic properties characteristic of the type IV family of DNA repair enzymes, such as AP-endonucleases and 3'-phosphatases . However, the purified protein lacked both 5'-phosphatase and exonuclease III activities . YqfS showed not only a high level of amino acid identity with E . coli Nfo but also a high resistance to inactivation by EDTA, in the presence of DNA containing AP sites (AP-DNA) . These results suggest that YqfS possesses a trinuclear Zn center in which the three metal atoms are intimately coordinated by nine conserved basic residues and two water molecules . Electrophoretic mobility shift assays demonstrated that YqfS possesses structural properties that permit it to bind and scan undamaged DNA as well as to strongly interact with AP-DNA . The ability of yqfS to genetically complement the DNA repair deficiency of an E . coli mutant lacking the major AP-endonucleases Nfo and exonuclease III strongly suggests that its product confers protection to cells against the deleterious effects of oxidative promoters and alkylating agents . Thus, we conclude that YqfS of B . subtilis is a spore-specific protein that has structural and enzymatic properties required to participate in the repair of AP sites and 3' blocking groups of DNA generated during both spore dormancy and germination . P15 and P3, the Tail Completion Proteins of Bacteriophage T4, Both Form Hexameric Rings. Li Zhao, 2003.Two proteins, gp15 and gp3 (gp for gene product), are required to complete the assembly of the T4 tail . gp15 forms the connector which enables the tail to bind to the head, whereas gp3 is involved in terminating the elongation of the tail tube . In this work, genes 15 and 3 were cloned and overexpressed, and the purified gene products were studied by analytical ultracentrifugation, electron microscopy, and circular dichroism . Determination of oligomerization state by sedimentation equilibrium revealed that both gp15 and gp3 are hexamers of the respective polypeptide chains . Electron microscopy of the negatively stained P15 and P3 (P denotes the oligomeric state of the gene product) revealed that both proteins form hexameric rings, the diameter of which is close to that of the tail tube . The differential roles between gp15 and gp3 upon completion of the tail are discussed . Contrasting Patterns of Phytoplankton Community Pigment Composition in Two Salt Marsh Estuaries in Southeastern United States. Peter A. Noble, 2003.Phytoplankton community pigment composition and water quality were measured seasonally along salinity gradients in two minimally urbanized salt marsh estuaries in South Carolina in order to examine their spatial and temporal distributions . The North Inlet estuary has a relatively small watershed with minimal fresh water input, while the Ashepoo, Combahee, and Edisto (ACE) Basin is characterized by a relatively greater influence of riverine drainage . Sampling stations were located in regions of the estuaries experiencing frequent diurnal tidal mixing and had similar salinity and temperature regimens . Phytoplankton community pigment composition was assessed by using high-performance liquid chromatography (HPLC) and multivariate statistical analyses . Shannon diversity index, principal-component, and cluster analyses revealed that phytoplankton community pigments in both estuaries were seasonally variable, with similar diversities but different compositions . The temporal pigment patterns indicated that there was a relatively weak correlation between the pigments in ACE Basin and the relative persistence of photopigment groups in North Inlet . The differences were presumably a consequence of the unpredictability and relatively greater influence of river discharge in the ACE Basin, in contrast to the greater environmental predictability of the more tidally influenced North Inlet . Furthermore, the timing, magnitude, and pigment composition of the annual phytoplankton bloom were different in the two estuaries . The bloom properties in North Inlet reflected the predominance of autochthonous ecological control (e.g., regenerated nutrients, grazing), and those in ACE Basin suggested that there was greater influence of allochthonous environmental factors (e.g., nutrient loading, changes in turbidity) . These interestuarine differences in phytoplankton community structure and control provide insight into the organization of phytoplankton in estuaries .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
