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1.
Klausner has hypothesized that female-headed households are less efficient in the use of energy than male-headed households because they are less disciplined and ordered. The present study used multivariate analyses to determine whether female-headed households were less efficient in the use of electrical energy than male-headed households in a representative sample of 4638 Anglo, Spanish-speaking, and black homeowning Texas households. The results indicated that, after controlling for the effects of other variables known to affect the use of electricity, sex of household head had nostatistically significant independent effect on electricity consumption in any ethnic or marital status group. The authors compare their results to those obtained by Klausner and discuss implications for social organizational theory of household energy consumption.  相似文献   

2.
The on-line calculated specific rates of growth, substrate consumption and product formation were used to diagnose microbial activities during a lactic acid fermentation. The specific rates were calculated from on-line measured cell mass, and substrate and product concentrations. The specific rates were more sensitive indicators of slight changes in fermentation conditions than such monitored data as cell mass or product concentrations.List of Symbols 1/h specific rate of cell growth - 1/h specific rate of substrate consumption - 1/h specific rate of product formation - * dimensionless specific rate of cell growth - * dimensionless specific rate of substrate consumption - * dimensionless specific rate of product formation - max 1/h maximum specific rate of cell growth - max 1/h maximum specific rate of substrate consumption - max 1/h maximum specific rate of product formation - X g/l cell mass concentration - S g/l substrate concentration - S * dimensionless substrate concentration - S 0 g/l initial substrate concentration - P g/l product concentration  相似文献   

3.
We have investigated the substrate subsite recognition requirement of the xyloglucan endo-transglycosylase/xyloglucan-specific endo-(14)--d-glucanase (NXET) from the cotyledons of nasturtium seedlings. Seed xyloglucans are composed almost entirely of the Glc4 subunits XXXG, XLXG, XXLG and XLLG, where G represents an unsubstituted glucose residue, X a xylose-substituted glucose residue and L a galactosyl-xylose-substituted glucose residue. Thus in the xyloglucan sequence shown below, the xylose (Xyl) residues at the backbone glucose (Glc) residues numbered — 3,— 2, + 2 and + 3 may be galactose-substituted, and NXET cleaves between the unsubstituted glucose at — 1 and the xylose-substituted glucose at + 1, which never carries a galactosyl substituent. We have isolated the xyloglucan oligosaccharides XXXGXXXG and XLLGXLLG from NXET digests of tamarind seed xyloglucan, have modified them enzymatically using a pure xyloglucan oligosaccharide-specific -xylosidase from nasturtium seeds to give GXXGXXXG and GLLGXLLG, and have identified and compared the products of NXET action on XXXGXXXG, GXXGXXXG, XLLGXLLG and GLLGXLLG. We have also compared the molar proportions of XXXG, XLXG, XXLG and XLLG in native tamarind and nasturtium seed xyloglucans with those in NXET digests of these polysaccharides. Using these and existing data we have demonstrated that NXET action does not require xylosesubstitution at glucose residues — 4, — 2, + 1 and + 3 and that xylose substitution at + 2, is a requirement. There may also be a requirement for xylose substitution at — 3. We have demonstrated also that galactosyl substitution of a xylose residue at + 1 prevents, and at — 2 modifies, chain-cleavage. A partial model for the minimum substrate binding requirement of NXET is proposed.Abbreviations G unsubstituted glucose residue - X xylose-substituted glucose residue - L galactosylxylose-substituted glucose residue - F fucosyl-galactosylxylose-substituted glucose residue - Gal galactose - Glc glucose - HPAE high-performance anion-exchange chromatography - NXET nasturtium xyloglucan endo-transglycosylase or xyloglucan-specific endo-(14)--d-glucanase - Xyl xylose This work was funded jointly by Unilever UK and the Department of Trade and Industry (UK) via the LINK initiative Agro-Food Quality.  相似文献   

4.
Transitions in the growth limiting factor from light (I) to nitrogen (N) and vice versa caused changes in geosmin production, protein and carbohydrate content, and the synthesis of pigments such as chlorophyll a (Chl a), phycobiliproteins (PBPs), and -carotene of the cyanobacterium Oscillatoria brevis. Following IN transition the first 150h, the decrease in protein content was compensated for by an increase of carbohydrates, and thereby, a constant biomass level was maintained in this period. Thereafter, biimass dropped to 15% of its initial level. A decrease in geosmin and pigment content was observed during transition from IN-limited growth. However, geosmin increased relative to phytol (Chl a) and -carotene which may indicate that a lowered demand for phytol and -carotene during N-limited growth allows isoprenoid precursors to be directed to geosmin rather than to pigment synthesis. Synthesis of Chl a and -carotene at the expense of geosmin was suggested for the observed start of increase in geosmin production only at the time that Chl a and -carotene had reached their I-limited steady state. Transition from nitrogen to light limited growth caused an acceleration of metabolism shown by a rapid decrease in carbohydrate content accompanied by an increase in protein content. The growth rate of the organisms temporarily exceeded the dilution rate of the culture and the biomass level increased 6-fold. Due to the only modest changes in geosmin production (2-fold) compared to changes in biomass level (6-fold) during I-or N-limited growth, environmental factors seem to have limited effect on geosmin production.Abbreviations Chl a chlorophyll a - dry wt dry weight; - I-limited light-limited - N-limited nitrogen-limited - PBP phycobiliprotein This research was performed at the Department of Microbiology, University of Amsterdam, with finacial support provided by the Royal Norwegian Ministry of Foreign Affairs and the Royal Norwegian Council for Scientific and Industrial Research  相似文献   

5.
The stoichiometric oxidation of uranous-to uranyl-uranium byThiobacllus ferrooxidans is demonstrated. Fixation of14CO2 and the effect of inhibitors demonstrate that energy is conserved during the oxidation and used for energy-dependent reverse electron flow and carbon dioxide fixation.Abbreviations HOQNO 2-heptyl-4-hydroxyquinoline-N-oxide - 8-HQ 8-hydroxyquinoline - TTFA thenoyltrifluoroacetone  相似文献   

6.
Phytochrome from leaves of light-grown oat (Avena sativa L. cv. Garry) plants is characterized with newly generated monoclonal antibodies (MAbs) directed to it. The results indicate that there are at least two phytochromes in green oat leaves, each of which differs from the phytochrome that is most abundant in etiolated oat tissue. When analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with reference to 124-kilodalton (kDa) phytochrome from etiolated oats, the two phytochromes from green oats have monomer sizes of 123 of 125 kDa. Immunoblot analysis of SDS, sample buffer extracts of lyophilized, green oat leaves indicates that neither the 125-kDa nor the 123-kDa polypeptide is a degradation product arising after tissue homogenization. Of the two, the 123-kDa phytochrome appears to be the predominant species in light-grown oat leaves. During SDS-PAGE in the presence of 1 mM Zn2+, 123-kDa phytochrome undergoes a mobility shift corresponding to an apparent mass increase of 2 kDa. In contrast, the electrophoretic mobility of 125-kDa phytochrome is unaffected by added Zn2+. Some MAbs that recognize 123-kDa phytochrome fail to recognize 125-kDa phytochrome and vice versa, indicating that these two phytochromes are not only immunochemically distinct from 124-kDa phytochrome, but also from each other. It is evident, therefore, that there are at least three phytochromes in an oat plant: 124-kDa phytochrome, which is most abundant in etiolated tissue, plus 123-and 125-kDa phytochromes, which predominate in light-grown tissue.Abbreviations Da Dalton - HA hydroxyapatite - MAb monoclonal antibody - PAb polyclonal antibody preparation - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate This research was supported by the U.S. Department of Energy (contract DE-AC-09-81SR10925 to L.H.P.). We thank Dr. Alan Jones, Department of Biology, University of North Carolina, Chapel Hill, USA, for kindly providing rabbit antiserum 4032, and Mrs. Donna Tucker and Mrs. Danielle Neal for their technical assistance.  相似文献   

7.
In potassium-limited chemostat cultures of Paracoccus denitrificans the maximum specific growth rate (µmax) was found to depend on the input potassium concentration: At 0.21mM µmax was 0.10–0.11 h-1; at 0.44 mM 0.15–0.16 h-1 and at 0.66 mM 0.20–0.21 h-1. The plots of the specific rates of oxygen-, succinate-and potassium consumption against gave straight lines. The intracellular potassium concentration was a linear function of and varied from 1% (0.13 M) at a value of 0.034 h-1 to 2.2% (0.29 M) at =0.26 h-1; the potassium concentration gradient and the potassium concentration in the culture fluid in the steady state were dependent on the input potassium concentration. The potassium concentration gradient varied from 8,900-1,200. At all values 20–25% of the total energy production was used for potassium transport. 350,100 and 30 ATP molecules were calculated to be required to maintain one potassium ion intracellular during 1 h at values of 0.034, 0.197 and 0.257 h-1 respectively. It is concluded that the amount of circulation of potassium is dependent on the potassium concentration gradient or on the potassium concentration in the culture in the steady state. The dependency of µmax on the input potassium concentration was explained by the assumption that at low input potassium concentrations the net uptake of potassium (influx-efflux) is not rapidly enough to maintain the high potassium gradient in the existing cells and to establish it in the newly formed cells. At high values and at high input potassium concentrations µmax is limited by the specific rate of oxygen consumption, which was found to be 11–12 mmol O2 g dry weight-1 h-1 at µmax for potassium-, succinate-and sulphate-limited chemostat cultures.  相似文献   

8.
TheN-linked carbohydrate chains of the-subunit of highly purified urinary human chorionic gonadotropin have been re-investigated. The oligosaccharides were released enzymatically by peptide-N 4-(N-acetyl--glucosaminyl)asparagine amidase-F, and fractionated by a combination of FPLC and HPLC. As a result of the application of improved fractionation methods, apart from the earlier reported carbohydrate chains, also small amounts of trisialo tri- and tri-antennary oligosaccharides were found. The primary structures of the latter carbohydrate chains have been determined by 500-MHz1H-NMR spectroscopy to beAbbreviations hCG human chorionic gonadotropin - hCG- -subunit - hCG- -subunit - PNGase-F peptide-N 4-(N-acetyl--glucosaminyl)asparagine amidase-F (E.C. 3.5.1.52) - endo-F endo--N-acetylglucosaminidase-F (E.C. 3.2.1.96) - SDS sodium dodecyl sulphate - PAGE polyacrylamide gel electrophoresis - CBB coomassie brilliant blue R 250 - GlcNAc N-acetylglucosamine - NeuAc N-acetylneuraminic acid - Man mannose - Gal galactose - Fuc fucose  相似文献   

9.
Carbon metabolism in photosynthesizing and respiring cells of Botryococcus braunii was radically changed by the presence of 1 mM NH4Cl in the medium, when the so-called resting state previously had been subjected to a nitrogen-deficient medium. Ammonia addition to the algae photosynthesizing with 14C-labelled HCO 3 - almost completely inhibited the synthesis of 14C-labelled botryococcenes and other hexane-extractable compounds, and also inhibited the formation of insoluble compounds; however, it resulted in a large increase in the synthesis of alanine, glutamine, other amino acids, and especially of 5-aminolevulinic acid. Total CO2 fixation decreased about 60% and O2 evolution decreased more than 50%.CO2 fixation in the dark with ammonia present led to labelled products derived from phosphoenolpyruvate carboxylation, such as glutamine, glutamate, and malate. Respiratory uptake of O2 increased by about 70%.The inhibition of terpenoid synthesis and increased synthesis of C5 amino acids by Botryococcus upon ammonia addition indicates 1) a diversion of acetyl coenzyme A from synthetic pathways leading to terpenoids and 2) increased operation of pathways leading to the synthesis of amino acids, especially 5-aminolevulinic acid, a precursor to chlorophyll biosynthesis.This work was supported in part by the Office of Energy Research, Office of Basic Energy Sciences, Biological Energy Research Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098, in part by a grant from SOHIO, and, in part, by a grant from the Japan-U.S. Cooperative Science Program (The Japan Society for the Promotion of Science, National Science Foundation, Division of International Programs)  相似文献   

10.
Starting from the conceptual premises of Garrod, who as long ago as 1902 spoke of chemical individuality, and of Burnet (1949), who recognized as self one's own molecular antigenic structures (as opposed to the antigenic alien: the non- self), the discovery and understanding of HLA antigens and of their extraordinarily individual and differentiated polymorphisms have gained universal recognition. Transplant medicine has now dramatically stressed, within man's knowledge of himself, the characteristic of his biological uniqueness. Today man, having become aware of being a biological antigenic-molecular individuality which is unique and different from that of all of his fellow men (except for monozygotic twins), can therefore easily consider himself a true biological Ego.Abbreviations BMT bone marrow transplantation - GVHD graft versus host disease - HLA human leukocyte antigens - MHC major histocompatibility complex - MLC mixed lymphocyte culture - MLR mixed lymphocyte reaction  相似文献   

11.
Transmannosylation from mannotriose (Man1-4Man1-4Man) to the 4-position at the nonreducing end N-acetylglucosaminyl residue ofN,N-diacetylchitobiose was regioselectively induced through the use of -d-mannanase fromAspergillus niger. The enzyme formed the trisaccharide Man1-4GlcNAc1-4GlcNAc (3.7% of the enzyme-catalysed net decrease ofN,N-diacetylchitobiose) from mannotriose as a donor andN,N-diacetylchitobiose as an acceptor. Mannobiose (Man1-4Man) was also shown to be useful as a donor substrate for the desired trisaccharide synthesis.Abbreviations Man d-mannose - (M n) (n=1–5) -linkedn-mer of mannose - GlcNAc2 2-acetamido-2-deoxy--d-glucopyranosyl-(1–4)-2-acetamido-2-deoxy-d-glucose  相似文献   

12.
Summary We have examined the effect of crude cardiac tissue extracts as well as that of several growth factors and triiodothyronin (T3) on DNA synthesis of cardiac myocytes in culture. Extracts from embryonic and adult cardiac tissue stimulated DNA synthesis of myocytes. Atrial myocytes exhibited overall higher degree of stimulation than their ventricular counterparts and extracts from adult atrial tissue had the highest apparent mitogenic activity for atrial myocytes. We have shown that adult heart contains basic fibroblast growth factor (bFGF), especially in the atria [1]. Transforming growth factor (TGF) and insulin-like growth factors (IGFs) are also accumulated in cardiac tissues [2, 3]. We found that bFGF and the IGFs stimulate myocyte cell proliferation and DNA synthesis. These factors also stimulate cardiac non-muscle proliferation, especially in the presence of serum. TGF inhibited proliferation and DNA synthesis and cancelled the effect of bFGF or IGFs on the myocytes. T3 also diminished the bFGF-induced mitogenic stimulation of cardiomyocytes. Our data suggest that these factors may be involved in the regulation of cardiomyocyte proliferation in vivo.Abbreviations bFGF basic Fibroblast Growth Factor - BSA Bovine Serum Albumin - DM Defined Medium - Fes Fetal calf serum - FITC Fluorescein - IGF Insulin-like Growth Factor - IgG Immunoglobulin - LI Labeling Index - PBS Phosphate Buffered Saline - T3 Triiodothyronine - TGF Transforming Growth Factor   相似文献   

13.
Summary To test the hypothesis that nocturnal body temperature (Tb) and metabolic rate (MR) in the pigeon are regulated during sleep at levels proportional to energy reserves, continuous recordings of Tb, oxygen consumption ( O2), carbon dioxide production, and electrophysiological measures were taken from five pigeons subjected to two separate 4-day fasts. Energy reserves were depleted differentially during the fasts by 12-h diurnal infusions of either saline or isosmotic glucose solutions. Although Tb and O2 were closely correlated, O2 declined throughout the fast during diurnal and nocturnal phases of the 12:12 light-dark cycle whereas significant declines in Tb were restricted to the night. Diurnal thermal conductance declined over days of fasting, especially during saline infusions, and was reduced to minimal levels each night. The durations and distributions of arousal states did not change during the fast or differ between conditions. The results were consistent with the hypothesis of a nocturnal regulation of Tb and metabolic rate proportional to energy reserves.Abbreviations C 1 thermal conductance - EEG electroencephalogram - EMG electromyogram - EOG electrooculogram - LD light-dark - MHP metabolic heat production - MR metabolic rate - REM rapid eye movement sleep - RQ respiratory quotient - SWS slow wave sleep - T a ambient temperature - T b body temperature - TRT total recording time - TST total sleep time - O2 oxygen consumption  相似文献   

14.
The present study was conducted to evaluate a statement in ancient yoga texts that suggests that a combination of both calming and stimulating measures may be especially helpful in reaching a state of mental equilibrium. Two yoga practices, one combining calming and stimulating measures (cyclic meditation) and the other, a calming technique (shavasan), were compared. The oxygen consumption, breath rate, and breath volume of 40 male volunteers (group mean ± SD, 27.0 ± 5.7 years) were assessed before and after sessions of cyclic meditation (CM) and before and after sessions of shavasan (SH). The 2 sessions (CM, SH) were 1 day apart. Cyclic meditation includes the practice of yoga postures interspersed with periods of supine relaxation. During SH the subject lies in a supine position throughout the practice. There was a significant decrease in the amount of oxygen consumed and in breath rate and an increase in breath volume after both types of sessions (2-factor ANOVA, paired t test). However, the magnitude of change on all 3 measures was greater after CM: (1) Oxygen consumption decreased 32.1% after CM compared with 10.1% after SH; (2) breath rate decreased 18.0% after CM and 15.2% after SH; and (3) breath volume increased 28.8% after CM and 15.9% after SH. These results support the idea that a combination of yoga postures interspersed with relaxation reduces arousal more than relaxation alone does.  相似文献   

15.
Summary The peroxidase-antiperoxidase immunocytochemical technique was used to identify the ACTH/endorphin cells in the porcine pituitary at the ultrastructural level and to determine the precise subcellular localization of the pro-ACTH/endorphin fragments. The cells display different aspects: 1) large, regular shapes with numerous and large secretory granules; 2) small, irregular and angular shapes with small granules aligned along the periphery of the cell; and 3) intermediate forms. The presence of and -endorphin not only in the same cells but also in the same secretory granules that contain ACTH and -LPH clearly indicates that both the precursor or its fragments and the abovementioned peptides are stored in the same granules and released simultaneously by the corticotropic cells. The presence of FSH in some corticotropic cells is also discussed.Abbreviations used in this Article ACTH corticotropin - -MSH -melanotropin (ACTH I–I3) - CLIP corticotropin-like intermediate lobe peptide (ACTH 18–39) - -LPH -lipotropin - -MSH -melanotropin (-LPH 41–58); -endorphin (-LPH 61–91); -endorphin (-LPH 61–76)  相似文献   

16.
The ion channel of the nicotinic acetylcholine receptor (nAChR) is believed to be lined by transmembrane M2 helices. A 4-8-12 sequence motif, comprising serine (S) or threonine (T) residues at positions 4, 8 and 12 of M2, is conserved between different members, anion and cation selective, of the nAChR superfamily. Parallel bundles of 4-8-12 motif-containing helices are considered as simplified models of ion channels. The relationship between S and T sidechain conformations and channelion interactions is explored via evaluation of interaction energies of K+ and of Cl ions with channel models. Energy calculations are used to determine optimal 2 (C-C\-O-H) values in the presence of K+ or Cl ions. 4-8-12 motif-containing bundles may form favourable interactions with either cations or anions, dependent upon the 2 values adopted. Parallel-helix and tilted-helix bundles are considered, as are heteromeric models designed to mimic the Torpedo nAChR. The main conclusion of the study is that conformational flexibility at 2 enables both S and T residues to form favourable interactions with anions or cations. Consequently, there is apparently no difference between S and T residues in their interactions with permeant ions, which suggests that the presence of T vs. S residues within the 4-8-12 motif is not a major mechanism whereby anion/cation selectivity may be generated. The implications of these studies with respect to more elaborate models of nAChR and related receptors are considered.Abbreviations nAChR, GluR, NMDA-R, 5HT3-R, GABAAR, GlyR nicotinic acetylcholine, glutamate, NMDA, 5HT3, GABAA and glycine receptors, respectively - PhTx philanthotoxin - M2 second membrane-spanning helix of receptor-channel subunits  相似文献   

17.
Hydrodynamic characteristics of two-phase inverse fluidized bed   总被引:1,自引:0,他引:1  
Hydrodynamic characteristics of a new mode of liquid-solid fluidization, termed as inverse fluidization in which low density floating particles are fluidized with downward flow of liquid, are experimentally investigated. The experiments are carried out with low density particles (<534 kg/m3) which allow high liquid throughputs in the system. During the operation, three regimes, namely, packed, semi-fluidization and fully fluidization are encountered. Empirical correlations are proposed to predict the pressure drop in each regime. A computational procedure is developed to simulate the variation of pressure drop with liquid velocity.List of Symbols Ar modified Archimedes number, d p 3 (– s)g/2 - d p particle diameter, mm - f friction factor (eq. 2) - g acceleration due to gravity, m/s2 - H total bed height, m - H c height of the column, m - Hf height of fluidized bed, m - H0 height of initial bed, m - Hp height of the packed bed, m - (p) pressure drop across the bed, N/m2 - (p) f pressure drop across fluidized bed section, N/m2 - (p) p pressure drop across the packed bed section, N/m2 - (p) sf total pressure drop in semifluidization regime, N/m2 - Re Reynolds number, d pU 1/ - Rem modified Reynolds number, d pU 1/(1– p) - U 1 superficial liquid velocity, m/s - Umf minimum fluidization velocity, m/s - Uosf onset fluidization velocity, m/s Greek Letters f voidage of fluidized bed - p voidage of packed bed - liquid viscosity, kg/ms - liquid density, kg/m3 - s particle density, kg/m3  相似文献   

18.
Imidazole fungicides such as imazalil, prochloraz, and triflurnizole and the triazole growth retardant paclobutrazol promote the shoot-inducing effect of exogenous cytokinins in Araceae, such as Spathiphyllum floribundum Schott and Anthurium andreanum Schott. The mechanism of their action could partially be based on the inhibition of gibberellic acid (GA) biosynthesis, because administration of GA3 inhibits the phenomenon completely in S. floribundum. Not only is the suppression of GA biosynthesis involved, but also the metabolism of endogenous cytokinins is significantly altered. Although the balance between isopentenyladenine, zeatin, dihydrozeatin, and their derivatives was shifted to distinguished directions by administration of BA and/or imazalil and/or GA3, no correlation between these changes in metabolic pathways and the number of shoots could be found. The metabolism of BA was not significantly altered by adding imazalil to the micropropagation medium of S. floribundum.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - [9R-5P]DHZ 9--d-ribofuranosyl-dihydrozeatin-monophosphate - [9R-5P]iP 6-isopentenyl-9--d-ribofuranosyladenine-monophosphate - [9R-5P]Z 9--d-ribofuranosyl-zeatin-monophosphate - [9G]BA 6-benzyl-9--d-glucopyranosyladenine - [9G]DHZ 9--d-glucopyranosyl-dihydrozeatin - [9G]iP 6-isopentenyl-9--d-glucopyranosyladenine - [9G]Z 9--d-glucopyranosyl-zeatin - [9R]BA 6-benzyl-9--d-ribofuranosyladenine - [9R]DHZ 9--d-ribofuranosyl-dihydrozeatin - [9R]iP 6-isopentenyl-9--d-ribofuranosyladenine - [9R]Z 9--d-ribofuranosyl-zeatin - BA 6-benzyladenine - DHZ dihydrozeatin - ES+ LC-MS/MS HPLC coupled Electrospray Tandem Mass Spectrometry - f.m. fresh mass - mT 6-(3-hydroxybenzyl)adenine - IMA imazalil - iP isopentenyladenine - NAA 1-naphthalene acetic acid - NFT Nutrient Film Technique - (OG)[9R]DHZ O--glucopyranosyl-9--d-ribofuranosyl-dihydrozeatin - (OG)[9R]Z O--d-glucopyranosyl-9--d-ribofuranosyl-zeatin - (OG)DHZ O--d-glucopyranosyl-dihydrozeatin - (OG)Z O--d-glucopyranosyl-zeatin - PAR Photosynthetic Active Radiation - PBZ paclobutrazol - PRO prochloraz - TDZ thidiazuron - TRI triflurnizole - Z zeatin  相似文献   

19.
Various techniques were used to develop a method for the growth ofTrichophyton mentagrophytes on fabrics. Air Force sock samples composed of wool, nylon and cotton mixtures were used as test materials. Growth of the organism on sock samples was obtained at 23°C and 70% relative humidity after seeding with horsehair spraying with yeast extract.Contribution no. 162. Department of Infectious Diseases, College of Veterinary Medicine, Kansas Agricultural Experiment Station, Manhattan, 66502.This study was supported under the Project Themis Program (USAFORSR Contract F 44620-68-C-0020 sponsored by the United States Air Force).  相似文献   

20.
Summary Candida wickerhamii growing on cellobiose produced -glucosidase with high activity against -nitrophenyl glucoside (PNPG) but low activity against cellobiose. -glucosidase production was constitutive, and was repressed by -glucosides and glucose. -glucosides containing an aromatic moiety in the aglycon were the best substrates for -glucosidase indicating that the enzyme is an aryl--glucosidase. A -glucosidase from C. wickerhamii cells was purified by (NH4)2SO4 precipitation, dialysis, ion-exchange chromatography and gel filtration. The purified enzyme was homogeneous as shown by sodium-dodecyl-sulphate polyacrylamide gel electrophoresis and discontinuous gel electrophoresis. The purified enzyme hydrolysed PNPG but not cellobiose. The Km of the enzyme was 0.185 mM. Glucose inhibited the enzyme competitively and the Ki was 7.5 mM. The apparent molecular mass was 97,000. The optimum pH and temperature for enzyme activity were between pH 7 and 7.4 and 40°C respectively. At temperatures of 45°C and greater the enzyme was inactivated. The activation energy of the enzyme was 29.4 kJ · mol-1.  相似文献   

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