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Hot compressed liquid water was used to treat switchgrass in a method called hydrothermolysis to disrupt lignin, dissolve hemicellulose, and increase accessibility of cellulose to cellulase. Three temperatures (190, 200, and 210 °C) and hold times (10, 15, and 20 min) were tested. Switchgrass treated at 190 °C for 10 min had the greatest xylan recovery in the prehydrolyzate. Less than 0.65 g/L glucose were released into the prehydrolyzate for all pretreatment conditions, indicating most glucose was retained as cellulose in the solid substrate. 5-Hydroxymethylfurfural (HMF) and furfural formation in the prehydrolyzate were found to be less than 1 g/L for all treatments. The highest concentration of ethanol, 16.8 g/L (72% of theoretical), was produced from switchgrass pretreated at 210 °C and 15 min using simultaneous saccharification and fermentation (SSF) at 45 °C with the thermotolerant yeast Kluyveromyces marxianus IMB4 and 15 FPU cellulase/g glucan.  相似文献   
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alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serineproteinase inhibitor superfamily, has a primary role in controllingneutrophil elastase activity within the mammalian circulation. Severalstudies have indicated that the reactive center region of alpha 1-PI, theamino acid sequence of which is critical to recognition of and binding totarget proteinases, is highly divergent within and among species. Thisappears to be a consequence of accelerated rates of evolution that may havebeen driven by positive Darwinian selection. In order to examine this andother features of alpha 1-PI evolution in more detail, we have isolated andsequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mussaxicola and Mus minutoides and have compared these with a number of othermammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extentof nonsynonymous substitution is generally high throughout the alpha 1-PImRNA molecule, indicating greater overall rates of amino acid substitution.Within and among mouse species, the 5'-half of the mRNA, but not the3'-half, has been homogenized by concerted evolution. Finally, the reactivecenter is under diversifying or positive Darwinian selection in muridrodents (rats, mice) and guinea pigs yet is under purifying selection inprimates and artiodactyls. The significance of these findings to alpha 1-PIfunction and the possible selective forces driving evolution of serpins ingeneral are discussed.  相似文献   
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Betchen  SA; Doty  RL 《Chemical senses》1998,23(4):453-457
Several fundamental questions remain enigmatic concerning human olfactorysensitivity, including (i) whether detection threshold differences existbetween the two sides of the nose (and, if so, whether such differences areinfluenced by handedness) and (ii) whether bilateral (i.e. binasal)stimulation leads to lower thresholds than unilateral stimulation (and, ifso, whether the degree of facilitation is inversely related to generalolfactory ability). In this study, and well-validated single staircaseprocedure was used to establish bilateral and unilateral detectionthresholds for the cranial nerve I stimulant phenyl ethyl alcohol in 130right- and 33 left-handed subjects. No differences in sensitivity betweenthe left and right sides of the nose were observed in either group.Bilateral thresholds were lower, on average, than unilateral thresholdswhen the latter were categorized in terms of left and right nares. However,the bilateral thresholds did not differ significantly from those of theside of the nose with the lower threshold. Overall smell ability, asmeasured by the University of Pennsylvania Smell Identification Test, didnot interact with any of the test measures. These data imply that (i) theleft and right sides of the nose do not systematically differ in detectionthreshold sensitivity for either dextrals or sinistrals and (ii) if centralintegration of left:right olfactory threshold sensitivity occurs, itseffects do not exceed the function of the better side of the nose.  相似文献   
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The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features.  相似文献   
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  总被引:3,自引:0,他引:3  
The development of low-cost, sustainable, and renewable energy sources has been a major focus since the 1970s. Fuel-grade ethanol is one energy source that has great potential for being generated from biomass. The demonstration of the fermentation of biomass-generated producer gas to ethanol is the major focus of this article in addition to assessing the effects of producer gas on the fermentation process. In this work, producer gas (primarily CO, CO(2), CH(4), H(2), and N(2)) was generated from switchgrass via gasification. The fluidized-bed gasifier generated gas with a composition of 56.8% N(2), 14.7% CO, 16.5% CO(2), 4.4% H(2), and 4.2% CH(4). The producer gas was utilized in a 4-L bioreactor to generate ethanol and other products via fermentation using a novel clostridial bacterium. The effects of biomass-generated producer gas on cell concentration, hydrogen uptake, and acid/alcohol production are shown in comparison with \"clean\" bottled gases of similar compositions for CO, CO(2), and H(2). The successful implementation of generating producer gas from biomass and then fermenting the producer gas to ethanol was demonstrated. Several key findings following the introduction of producer gas included: (1) the cells stopped growing but were still viable, (2) ethanol was primarily produced once the cells stopped growing (ethanol is nongrowth associated), (3) H(2) utilization stopped, and (4) cells began growing again if \"clean\" bottled gases were introduced following exposure to the producer gas.  相似文献   
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  总被引:2,自引:0,他引:2  
Hsu  L; Prentice  RL; Zhao  LP; Fan  JJ 《Biometrika》1999,86(4):743-753
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