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William M. Fogarty Marian P. Brosnan Evelyn M. Doyle Catherine T. Kelly 《Applied microbiology and biotechnology》1992,37(2):191-196
Summary Two strains (NCIB 11412 and NCIB 10814) of the thermophilic organism Bacillus stearothermophilus were found to produce complex carbohydrase systems. The enzyme activities in each system include -amylase as the major component, maltase, pullulanase, a minor amylase and cyclodextrinase. The latter three activities are produced in low yield in both strains. A crude enzyme preparation from each strain possessed maltogenic properties on hydrolysis of soluble starch. Following rigorous purification procedures, the purified major -amylase from either strain did not produce maltose as a major end-product of starch hydrolysis. However, a partially purified mixture of pullulanase, minor amylase and cyclodextrinase activities from NCIB 11412 and NCIB 10814 produced 56.4% and 62.0% maltose, respectively, from soluble starch. 相似文献
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Temperate zone insect species have evolved three general strategies for synchronizing the end of hibernation with the return of favorable conditions. Recent eco-physiological studies of insect dormancy and development indicate that the prevailing concepts of the adaptations regulating hibernation and the resumption of spring activity, need revision. In particular, experimental evidence shows that despite implications in the term, dormancy is a dynamic state; the organism, by constantly monitoring the constantly-changing environmental parameters, is kept in phase with the seasons at its particular locality. Furthermore, the insect's ability to respond to environmental factors generally changes as the season progresses. Therefore, the construction of realistic predictive models of insect seasonality should be based on investigations of natural populations undergoing hibernation in the field, combined with ecologically and physiologically meaningful laboratory studies.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA. 相似文献
37.
Hillary A. Raab Careen Foord Romain Ligneul Catherine A. Hartley 《PLoS computational biology》2022,18(6)
Accurate assessment of environmental controllability enables individuals to adaptively adjust their behavior—exploiting rewards when desirable outcomes are contingent upon their actions and minimizing costly deliberation when their actions are inconsequential. However, it remains unclear how estimation of environmental controllability changes from childhood to adulthood. Ninety participants (ages 8–25) completed a task that covertly alternated between controllable and uncontrollable conditions, requiring them to explore different actions to discover the current degree of environmental controllability. We found that while children were able to distinguish controllable and uncontrollable conditions, accuracy of controllability assessments improved with age. Computational modeling revealed that whereas younger participants’ controllability assessments relied on evidence gleaned through random exploration, older participants more effectively recruited their task structure knowledge to make highly informative interventions. Age-related improvements in working memory mediated this qualitative shift toward increased use of an inferential strategy. Collectively, these findings reveal an age-related shift in the cognitive processes engaged to assess environmental controllability. Improved detection of environmental controllability may foster increasingly adaptive behavior over development by revealing when actions can be leveraged for one’s benefit. 相似文献
38.
Ren X Zhao L Sivashanmugam A Miao Y Korando L Yang Z Reardon CA Getz GS Brouillette CG Jerome WG Wang J 《Biochemistry》2005,44(45):14907-14919
Apolipoprotein AI (apoAI), the major protein component of HDL, is one of the best predictors of coronary artery disease (CAD), with high apoAI and HDL levels being correlated with low occurrences of CAD. The primary function of apoAI is to recruit phospholipid and cholesterol for assembly of HDL particles. Like other exchangeable apolipoproteins, lipid-free apoAI forms a mixture of different oligomers even at 1.0 mg/mL. This self-association property of the exchangeable apolipoproteins is closely associated with the lipoprotein-binding activity of this protein family. It is unclear if the self-association property of apolipoprotein is required for its lipoprotein-binding activity. We developed a novel method for engineering an oligomeric protein to a monomeric, biologically active protein. Using this method, we generated a monomeric mouse apoAI mutant that is active. This mutant contains the first 216 residues of mouse apoAI and replaces six hydrophobic residues with either polar or smaller hydrophobic residues at the defined positions (V118A/A119S/L121Q/T191S/T195S/T199S). Cross-linking results show that this mutant is greater than 90% monomeric at 8 mg/mL. CD, DSC, and NMR results indicate that the mutant maintains an identical secondary, tertiary structure and stability as those of the wild-type mouse apoAI. Lipid-binding assays suggest that the mutant shares an equal lipoprotein-binding activity as that of the wild-type apoAI. In addition, both the monomeric mutant and the wild-type protein make nearly identical rHDL particles. With this monomeric mouse apoAI, high-quality NMR data has been collected, allowing for the NMR structural determination of lipid-free apoAI. On the basis of these results, we conclude that this apoAI mutant is a monomeric, active apoAI useful for structural determination. 相似文献
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Method for the isolation of high-quality RNA from grape berry tissues without contaminating tannins or carbohydrates 总被引:20,自引:1,他引:20
Grape berries contain compounds that aggregate with and precipitate RNA in the presence of chaotropic agents or phenol. The
procedure described here extracts RNA from finely ground tissues using mild denaturants, and selectively precipitates the
aggregate-forming material with 30% ethanol. The resulting RNA is suitable for northern blot analysis and translationin vitro. 相似文献
40.
Jean-Baptiste Boulé Emmett Johnson François Rougeon Catherine Papanicolaou 《Molecular biotechnology》1998,10(3):199-208
Terminal deoxynucleotidyl transferase (TdT) is a highly conserved vertebrate enzyme that possesses the unique ability to catalyze
the random addition of deoxynucleoside 5′-triphosphates onto the 3′-hydroxyl group of a single-stranded DNA. It plays an important
role in the generation of immunoglobin and T-cell receptor diversity. TdT is usually obtained from animal thymus gland or
produced in a baculovirus system, but both procedures are rather tedious, and proteolysis occurs during purification. Attempts
to overexpress TdT in bacteria have been unsuccessful or have yielded an enzyme with a lower specific activity. A dearth of
TdT has thus hampered detailed structural and functional studies. In the present study, we report that by lowering growth
temperature and overexpressing a rare arginyl tRNA, it is possible to boost the production inEscherichia coli of murine TdT with minimal proteolysis and high specific activity. 相似文献