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1.
Masaaki Yoshikawa Makoto Tamaki Etsuro Sugimoto Hideo Chiba 《Bioscience, biotechnology, and biochemistry》2013,77(10):2051-2052
The pyrolyzate of the nondialyzable melanoidin prepared from glucose-ammonia reaction system (kept in pH 5.3~6.0 during the reaction) was fractionated to volatile fraction and nonvolatile fraction. Among the volatile components, two pyridines and four alkylpyrazines were identified. On the other hand, one imidazole compound and two β-hydroxypyridines isolated from the nonvolatile fraction were identified as 4(5)-methylimidazole, 3-hydroxypyridine and 2-methyl-5-hydroxypyridine, respectively. It is inferred that these compounds are not produced by the fission of the main skeleton in the melanoidin molecule, but formed by pyrolysis of the heterocyclic compounds present as a small moiety in the melanoidin. 相似文献
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Klein MP Nunes MR Rodrigues RC Benvenutti EV Costa TM Hertz PF Ninow JL 《Biomacromolecules》2012,13(8):2456-2464
The effect of the support size on the properties of enzyme immobilization was investigated by using chitosan macroparticles and nanoparticles. They were prepared by precipitation and ionotropic gelation, respectively, and were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), light scattering analysis (LSA), and N(2) adsorption-desorption isotherms. β-Galactosidase was used as a model enzyme. It was found that the different sizes and porosities of the particles modify the enzymatic load, activity, and thermal stability of the immobilized biocatalysts. The highest activity was shown by the enzyme immobilized on nanoparticles when 204.2 mg protein·(g dry support)(-1) were attached. On the other hand, the same biocatalysts presented lower thermal stability than macroparticles. β-Galactosidase immobilized on chitosan macro and nanoparticles exhibited excellent operational stability at 37 °C, because it was still able to hydrolyze 83.2 and 75.93% of lactose, respectively, after 50 cycles of reuse. 相似文献
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The objective of this study is to understand the influence of pH and effect of cosolvent (glucose) on the stabilization of bovine α-lactalbumin by using ultrasonic techniques. Values of density, ultrasonic velocity and viscosity were measured for bovine α-lactalbumin (5 mg/ml) dissolved in phosphate buffer (pH 2, 5, 7, 9 and 12) solutions mixed with and without the cosolvent at 30 °C. These measurements were used to calculate few thermo-acoustical parameters such as adiabatic compressibility, intermolecular free length, acoustic impedance, relaxation time, relative association constant, the partial apparent specific volume and the partial apparent specific adiabatic compressibility for the said systems. The obtained results revealed a strong comparison between the effects of acidic and alkaline pH values on protein denaturation, i.e., the acidic pH are instantaneous and are of less magnitude whereas alkaline pH are slower but sharper. Further the present study supports the fact that the presence of glucose stabilizes α-lactalbumin against denaturation due to pH variation, which may be due to the strengthening of non-covalent interactions and the steric exclusion effect. 相似文献
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Effect of cortisone on the developmental pattern of the neutral and the acid β-galactosidases of the small intestine of the rat
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1. The developmental pattern and effect of cortisone on acid beta-galactosidase and neutral beta-galactosidase were studied in postnatal rats by a recently proposed method for their independent determination. 2. After birth the acid beta-galactosidase activity increases in the ileum, whereas it decreases slightly in the jejunum. On day 16 after birth the activity in the ileum decreases and in 20-day-old rats activity in both parts of the intestine decreases to adult values. In suckling animals the activity in the ileum exceeds the jejunal activity severalfold and in adult animals the activity in the jejunum is slightly higher than that in the ileum. 3. Neutral beta-galactosidase activity is high after birth and decreases in both jejunum and ileum after day 20 after birth. In 12-20-day-old rats activity in both parts is essentially the same, but in adult animals jejunal activity exceeds ileal activity four-to five-fold. 4. Cortisone (0.5, 2.0 or 5.0mg/100g body wt. daily for 4 days) does not influence the activity of either enzyme in 60-day-old rats. Acid beta-galactosidase activity is decreased after cortisone treatment in 8-, 12-, 16-and 18-day-old rats, with sensitivity to cortisone increasing with the approach of weaning. No effect of cortisone on acid beta-galactosidase is seen in 8-day-old rats. Neutral beta-galactosidase activity is increased in the ileum of 8-, 12-, 16- and 18-day old rats, but only in the jejunum of 8-and 12-day-old rats. 相似文献
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Experimental evidence has suggested that the high endogenous levels of taurine found in the rat heart and retina are maintained to a large extent by transport processes out of the blood, rather than by endogenous biosynthesis. When these high levels are depleted, dysfunction ensues. In vitro studies have shown that -alanine is a good antagonist of these transport processes. The current studies were done to evaluate the feasibility of depleting heart and retinal taurine levels in vivo through treatment of adult rats either orally or with injections of -alanine. None of the treatments had significant effects on retinal taurine content; ventricular taurine was reduced in some situations, but the effects were not maintained, nor as large as with another transport antagonist. No functional changes were observed. Oral treatment with -alanine had fewer obvious side effects than injections, but all treated rats had body weights less than age-matched controls. 相似文献
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Jana Klose Angelika Ehrlich Michael Bienert 《International journal of peptide research and therapeutics》1998,5(2-3):129-131
Summary Proline and Pro-derived peptidomimetics, such as meoxPro-Oic (4-methoxy-proline-octahydro indolic acid), and DBF (2-aminoethyl-6-dibenzofuran
propionic acid) were introduced into thymopentin-derived penta-[SP5-] and hexa-[SP6-] peptides and penta-, hexa- and hepta-alanine.
Surprisingly, we found that cyclomonomer formation in the investigated penta- and hexapeptides was drastically hindered by
the presence of proline regardless of position. 相似文献
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Xavier Deupi Mireia Olivella Arantxa Sanz Nicole Dölker Mercedes Campillo Leonardo Pardo 《Journal of structural biology》2010,169(1):116-123
In order to study the influence of Ser and Thr on the structure of transmembrane helices we have analyzed a database of helix stretches extracted from crystal structures of membrane proteins and an ensemble of model helices generated by molecular dynamics simulations. Both complementary analyses show that Ser and Thr in the g? conformation induce and/or stabilize a structural distortion in the helix backbone. Using quantum mechanical calculations, we have attributed this effect to the electrostatic repulsion between the side chain Oγ atom of Ser and Thr and the backbone carbonyl oxygen at position i ? 3. In order to minimize the repulsive force between these negatively charged oxygens, there is a modest increase of the helix bend angle as well as a local opening of the helix turn preceding Ser/Thr. This small distortion can be amplified through the helix, resulting in a significant displacement of the residues located at the other side of the helix. The crystal structures of aquaporin Z and the β2-adrenergic receptor are used to illustrate these effects. Ser/Thr-induced structural distortions can be implicated in processes as diverse as ligand recognition, protein function and protein folding. 相似文献
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Summary Female freshwater eels injected with estradiol-17 (E2) for 15–78 days appear paler and secrete more mucus than controls. The resulting strongly opalescent blood plasma indicates that vitellogenin synthesis occurs in the liver, which shows a significant hypertrophy, an increased vacuolization (lipid material) and glycogen depletion. Plasma sodium is lowered, but calcium levels are considerably increased. The gonosomatic index increases (0.92±0.1 to a maximum of 2.21). Oocytes are enlarged, but the incorporation of vitellogenin remains discrete. Gonadotrophs (GTH cells), small and scarcely visible in the pituitary of control eels, are hypertrophied and contain numerous glycoprotein granules after E2-administration. E2 may act on the pituitary and/or hypothalamus via a positive feedback to induce gonadotrophin (GTH) synthesis; GTH release seems to be very limited as indicated by the ovarian response. The differentiation of GTH cells in eels treated with fish pituitary extracts is most probably due to secretion of E2 by the ovary, which reacts on the pituitary. Various hypotheses are considered to explain the low GTH release.Thyrotrophs, somatotrophs and prolactin cells of the pituitary are stimulated. In the pars intermedia, MSH and PAS-positive cells appear less active. A possible antidopaminergic effect of E2 is discussed.E2 administration constitutes a simple and economic technique to induce the synthesis of GTH and will facilitate the biochemical and biological study of the latter hormone in eels. 相似文献
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Environmental gradients often lead to the parallel evolution of populations and species. To what extent do such gradients also lead to parallel evolution of the sexes? We used guppies (Poecilia reticulata) to examine the parallel and independent (sex‐specific) aspects of population divergence in response to predation and habitat features. Geometric morphometrics was used to analyse size and shape variation for 1335 guppies from 27 to 31 sites sampled in each of 2 years. Body size showed strong parallel population divergence; both sexes were larger at sites with a more open canopy and with higher flow. Body shape showed a mixture of parallel and independent population divergence. The strongest and most consistent effects were (1) high‐predation sites had males with smaller heads and deeper caudal peduncles, (2) open‐canopy sites had females with smaller heads and more distended abdomens and (3) high‐flow sites had males and females with smaller heads and deeper caudal peduncles. 相似文献
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Does the impact of nutrients on the biological structure and function of brackish and freshwater lakes differ? 总被引:6,自引:6,他引:0
Jeppesen E. Søndergaard M. Kanstrup E. Petersen B. Eriksen R. B. Hammershøj M. Mortensen E. Jensen J. P. Have A. 《Hydrobiologia》1994,275(1):15-30
The effects of nutrients on the biological structure of brackish and freshwater lakes were compared. Quantitative analysis of late summer fish, zooplankton, mysid and macrophyte populations was undertaken in 20–36 shallow brackish lakes of various trophic states and the findings compared with a similar analysis of shallow freshwater lakes based on either sampling (fish) or existing data (zooplankton, mysids and macrophytes). Special emphasis was placed on differences in pelagic top-down control. Whereas the fish biomass (CPUE, multiple mesh-size gill nets) rose with increasing P-concentration in freshwater lakes, that of brackish lakes was markedly reduced at P-concentrations above ca. 0.4 mg P l-1 and there was a concomitant shift to exclusive dominance by the small sticklebacks (Gasterosteus aculeatus and Pungitius pungitius); as a result, fish density remained relatively high. Mysids (Neomysis integer) were found at a salinity greater than 0.5 and increased substantially with increasing P-concentration, reaching levels as high as 13 ind. l-1. This is in contrast to the carnivorous zooplankton of freshwater lakes, which are most abundant at intermediate P levels. The efficient algal controller, Daphnia was only found at a salinity below 2 and N. integer in lakes with a salinity above 0.5. Above 2 the filter-feeding zooplankton were usually dominated by the less efficient algal controllers Eurytemora and Acartia. In contrast to freshwater lakes, no shift to a clearwater state was found in eutrophic brackish lakes when submerged macrophytes became abundant. We conclude that predation pressure on zooplankton is higher and algal grazing capacity lower in brackish eutrophic-hypertrophic lakes than in comparable freshwater lakes, and that the differences in trophic structure of brackish and freshwater lakes have major implications for the measures available to reduce the recovery period following a reduction in nutrient loading. From the point of view of top-down control, the salinity threshold dividing freshwater and brackish lakes is much lower than the conventionally defined 5. 相似文献
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Summary The results of studies on 49 families with 107 children and various populations of Caucasoid, Negroid and Mongoloid origin concerning the genetics and population genetics of the 2-glycoprotein I polymorphism are reported. In general the genetical model proposed by Cleve (1968) is confirmed: two autosomal alleles BgN and BgD controlling the phenotypes Bg N-N, Bg N-D and Bg D-D. However, divergences from this model were found in two families. They indicate the assumption of non-genetic factors influencing the phenotype expression rather than more complicated genetical control mechanisms. Within Caucasoid populations phenotype and gene frequencies show almost a homogeneous distribution. This racial stock is striking due to a significant higher 2-glycoprotein I concentration in serum as compared to Negroids and Mongoloids. In connection with this, these racial stocks differ obviously in the gene frequencies: Caucasoids BgN=0.937, Negroids=0.742, Mongoloids =0.780; resp. BgD=0.063, 0.258, 0.220.Supported by the Deutsche Forschungsgemeinschaft.D 77. 相似文献
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Gallová J Uhríková D Kučerka N Svorková M Funari SS Murugova TN Almásy L Mazúr M Balgavý P 《The Journal of membrane biology》2011,243(1-3):1-13
The influence of cholesterol and β-sitosterol on egg yolk phosphatidylcholine (EYPC) bilayers is compared. Different interactions of these sterols with EYPC bilayers were observed using X-ray diffraction. Cholesterol was miscible with EYPC in the studied concentration range (0-50 mol%), but crystallization of β-sitosterol in EYPC bilayers was observed at X ≥ 41 mol% as detected by X-ray diffraction. Moreover, the repeat distance (d) of the lamellar phase was similar upon addition of the two sterols up to mole fraction 17%, while for X ≥ 17 mol% it became higher in the presence of β-sitosterol compared to cholesterol. SANS data on suspensions of unilamellar vesicles showed that both cholesterol and β-sitosterol similarly increase the EYPC bilayer thickness. Cholesterol in amounts above 33 mol% decreased the interlamellar water layer thickness, probably due to "stiffening" of the bilayer. This effect was not manifested by β-sitosterol, in particular due to the lower solubility of β-sitosterol in EYPC bilayers. Applying the formalism of partial molecular areas, it is shown that the condensing effect of both sterols on the EYPC area at the lipid-water interface is small, if any. The parameters of ESR spectra of spin labels localized in different regions of the EYPC bilayer did not reveal any differences between the effects of cholesterol and β-sitosterol in the range of full miscibility. 相似文献
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Alpha crystallin is an eye lens protein with a molecular weight of approximately 800 kDa. It belongs to the class of small heat shock proteins. Besides its structural role, it is known to prevent the aggregation of β- and γ-crystallins and several other proteins under denaturing conditions and is thus believed to play an important role in maintaining lens transparency. In this communication, we have investigated the effect of 2,2,2-trifluoroethanol (TFE) on the structural and functional features of the native α-crystallin and its two constituent subunits. A conformational change occurs from the characteristic β-sheet to the α-helix structure in both native α-crystallin and its subunits with the increase in TFE levels. Among the two subunits, αA-crystallin is relatively stable and upon preincubation prevents the characteristic aggregation of αB-crystallin at 20% and 30% (v/v) TFE. The hydrophobicity and chaperone-like activity of the crystallin subunits decrease on TFE treatment. The ability of αA-crystallin to bind and prevent the aggregation of αB-crystallin, despite a conformational change, could be important in protecting the lens from external stress. The loss in chaperone activity of αA-crystallin exposed to TFE and the inability of peptide chaperone—the functional site of αA-crystallin—to stabilize αB-crystallin at 20–30% TFE suggest that the site(s) involved in subunit interaction and chaperone-like function are quite distinct. 相似文献
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Niel T CONSTANTINE William KABAT Richard Y ZHAO 《Cell research》2005,15(11):870-876
In China, the estimated number of HIV infected cases is approaching one million. Although public education has been initiated for awareness and behavioral modification for this devastating infection, better diagnostic methods are needed to identify infected persons and manage infection. Simple and more accurate diagnostic tools have become available, particularly for early detection and to monitor treatment in those who receive anti-retroviral treatment. In this short review, we summarize some of the common and new methodologies that can be used in clinical laboratories, in the field, or in private laboratories. These range from simple antibody tests to more sophistical methods that are used to monitor disease progression and identify drug resistance. These tools can assist physicians, medical practitioners, and laboratory personnel to select suitable diagnostic tools for the diagnosis, blood screening, monitoring of disease progression, and for detection of drug resistance to anti-retroviral therapies. 相似文献
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J. H. van Voorthuysen 《Pal?ontologische Zeitschrift》1952,26(1-2):30-48
The modern principles of marine biostratigraphy ask for more exact fossil determinations. In view of the increased activity in nearly all countries concerning this modern trend in geology more uniformity in the methods used for the determination of fossils and especially of microfossils, is needed. In this way a better understanding of the stratigraphical range of important species and their natural relations to other species in all parts of the world would be obtained. For this purpose the study of the internal structures is also important: siphuncular structures of the ammonite shell—heterostrophical oldest volutions of gastropods—canal systems of foraminifers. A few examples are given and figured. A few remarks on biostratigraphy, paleo-ecology, facies and guide fossils serve as an introduction. 相似文献