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1.
The fully enclosed Taiaro lagoon is hypersaline (42.5 psu) and non-tidal; constant salinity and water level result from strong
evaporation balanced by low percolation through the lagoon floor. Seawater can flow over the atoll rim during exceptionally
high seas and may then replenish lagoonal communities with propagules of oceanic origin. The distinctive water chemistry of
the lagoon suggests a possible way of identifying these immigrants. We established this potential by analysing stable isotopes
of carbon and oxygen in the recent growth layers of otoliths of two adult reef fishes, Chaetodon ulietensis and Acanthurus triostegus, collected from both sides of the atoll rim. Fish from the two locations were discriminated by their isotopic signatures,
suggesting that analysis of the microchemical signatures deposited during the larval development could be used in future work
to determine which individuals and species complete their life-cycles in this unusual lagoon.
Accepted: 28 August 1997 相似文献
2.
The proteolytic specificity of chicken cathepsin L was studied using bovine -casein as substrate. The peptide mixtures obtained after various times of hydrolysis were separated by RP-HPLC and ten peptides were identified. Chicken cathepsin L accepts proline residues in all positions except P
1
. Looking at the amino acid residues on the amino side of the scissile bond we found three times the Tyr-Pro pair at P
1
–P
2
positions and that the S
1
subsite can interact with modified amino acids such as phosphoserine.Abbreviations RP-HPLC
reverse phase high performance liquid chromatography
- NMec
N-methyl coumarylamide
- TEA
triethylamine
- TFA
trifluoroacetic acid 相似文献
3.
A. Touati C. Creuzenet J. M. Chobert E. Dufour T. Haertlé 《Journal of Protein Chemistry》1992,11(6):613-621
The study of the solubility of unstructured proteins (S1-, -, and -casein) and well-structured globulin (-lactoglobulin) in low water binary solvent systems demonstrated the crucial importance of solvent polarity and neutralization of protein polar functions on the final outcome of solubility experiments. The solubilities up to 38, 56, and 96% in CHCl3/CH3OH (1/1, v/v) acidified with HCl and up to 5, 10, and 25% in CHCl3/CH3OH (1/1, v/v) in the presence of triethylamine (TEA) were obtained for -, S1-, and -casein, respectively. The importance of protein charge neutralization was apparent when the solubilization was performed in basified CHCl3/CH3OH media, giving the optimal results when the studied proteins were brought before to their isoionic point. The maximum solubility of -casein at its pI in 30–70% methanol in CHCl3 was reaching 50–60% with triethylamine (TEA) added. -lactoglobulin could be solubilized up to 70% in CHCl3/CH3OH (7/3, v/v) acidified with HCl and up to 40% in CHCl3/CH3OH (3/7, v/v) in the presence of TEA. The observed yield of reductive alkylation of -lactoglobulin was much higher (98%) when performed in studied solvent system than in aqueous conditions (75%). Apparently, steric hindrance of the well-folded -barrel (in aqueous conditions) structure masks the portion of -NH2 groups. In the case of unstructured aqueous media -casein, 90% alkylation yields were obained in organic and aqueous conditions. 相似文献
4.
Sabine Lhernould Yannis Karamanos Sylvain Bourgerie Gerard Strecker Raymond Julien Henri Morvan 《Glycoconjugate journal》1992,9(4):191-197
We have previously isolated mannoside and xylomannoside oligosaccharides with one or two terminal reducingN-acetylglucosamine residues from the extracellular medium of white campion (Silene alba) suspension culture. We have now demonstrated the presence of peptide-N
4-(N-acetylglucosaminyl)asparagine amidase (PNGase) activity in cell extracts as well in the culture medium that could explain the production of those compounds. An additional xylomannoside, (GlcNAc)Man3(Xyl)GlcNAc(Fuc)GlcNAc, was characterized, and1H- and13C-NMR assignments for the oligosaccharide Man3(Xyl)GlcNAc(Fuc)GlcNAc were obtained using homonuclear and heteronuclear spectroscopy (COSY).Abbreviations Endo
endo--N-acetylglucosaminidase
- Fuc
fucose
- GlcNAc
N-acetylglucosamine
- Man
mannose
- NMR
nuclear magnetic resonance
- PNGase
peptide-N
4-(N-acetylglucosaminyl)asparagine amidase
- Xyl
xylose 相似文献
5.
Influence of maize root mucilage on soil aggregate stability 总被引:9,自引:0,他引:9
This study was undertaken to determine the effects of root exudates on soil aggregate stability. Root mucilage was collected
from two-month old maize plants (Zea mays L.) Mucilage and glucose solutions were added at a rate of 2.45 g C kg−1 dry soil to silty clay and silt loam soils. Amended soils, placed in serum flasks, were incubated for 42 d with a drying-wetting
cycle after 21 d. Evolved CO2 was measured periodically as well as the water-stable aggregates and soluble sugar and polysaccharide content of the soil.
In mucilage-amended soils CO2 evolution started with a lag phase of 2–3 days, which was not observed in glucose-amended soils. There was then a sharp increase
in evolved CO2 up to day 7. During the second incubation period there were only small differences in evolved C between treatments. Incorporation
of mucilage in both soils resulted in a spectacular and immediate increase in soil aggregate stability. Thereafter, the percent
of water-stable aggregates quickly decreased parallel to microbial degradation. On completion of the incubation, aggregate
stability in the silty clay soil was still significantly higher in the presence of mucilage than in the control. This work
supports the assumption that freshly released mucilage is able to stick very rapidly to soil particles and may protect the
newly formed aggregates against water destruction. On the silty clay, microbial activity contributes to a stabilization of
these established organo-mineral bounds. 相似文献
6.
Remy B Baril G Vallet JC Dufour R Chouvet C Saumande J Chupin D Beckers JF 《Theriogenology》1991,36(3):389-399
Repeated administration of xenogenic gonadotropins in human or animal species may be responsible for antibody production and refractoriness. An experiment was conducted in which goats were treated with porcine FSH (p-FSH) at 6-week intervals for a period of 7 months. A sensitive radioimmunoassay (RIA) was used to detect antibodies to p-FSH in plasma samples taken at short-term intervals during a 7-month period. Antibodies appeared after the first injection, and levels increased following booster injections. A high correlation rate existed between antibody level and superovulatory response. Refractoriness in goats was associated with a high level of antibodies. 相似文献
7.
An endogenous ligand for the central sulfonylurea receptor 总被引:2,自引:0,他引:2
An endogenous ligand for the rat central sulfonylurea receptor has been evidenced in the rat central nervous system. The characteristics of this ligand (extractibility, non-dialysability, chromatographic behaviour on different media, sensitivity to proteases) indicate that it is a neutral to slightly basic peptide. 相似文献
8.
9.
Generation and amplification of the cytosolic calcium signal during secretory responses to gonadotropin-releasing hormone 总被引:2,自引:0,他引:2
S S Stojilkovi? A Stutzin S Izumi S Dufour A Torsello M A Virmani E Rojas K J Catt 《The New biologist》1990,2(3):272-283
Gonadotropin-releasing hormone (GnRH) stimulates characteristic biphasic increases in cytosolic calcium concentration ([Ca2+]i) and in luteinizing hormone (LH) release in cultured gonadotrophs, with an early peak followed by a prolonged plateau in both responses. Analysis of [Ca2+]i by dual-wavelength fluorimetric assay and of LH release at 5-sec intervals in perifused pituitary cells revealed increases in both responses within a few seconds of exposure to GnRH. The maximum elevation of [Ca2+]i occurred within 20 sec, and the peak gonadotropin release in 35 sec; the total duration of the spike phase for both [Ca2+]i and LH release was 2.5 min. Under extracellular Ca2(+)-deficient conditions, the GnRH-induced peak in [Ca2+]i was reduced by about 20% and the plateau phase was abolished. Concomitantly, the magnitude of the acute phase of LH release was reduced by 40% and that of the second phase by about 90%. Recovery of the plateau phase of LH release occurred within 25 sec after addition of 1.25 mM Ca2+ to Ca2(+)-deficient medium. In a dose-dependent manner, the non-selective Ca2+ channel blockers Co2+ and Cd2+ reduced the Ca2+ current measured by whole-cell recording in pituitary gonadotrophs and abolished the extracellular Ca2(+)-dependent component of LH release. The selective calcium channel blocker, nifedipine, decreased the magnitude of the Ca2+ current and reduced the plateau phase of LH release by 50%; conversely, the dihydropyridine agonist methyl, 1,4,dihydro-2,6-dimethyl 3-nitro-4-(2-trifluorome) (Bay K 8644) consistently enhanced the amplitudes of both Ca2+ current and GnRH-induced LH release. These data reveal a close temporal correlation between changes in [Ca2+]i and LH release during GnRH action, with Ca2+ mobilization during the spike phase and Ca2+ influx through dihydropyridine-sensitive and insensitive sets of receptor-operated calcium channels during the spike and plateau phases. In addition, analysis of the magnitudes of the [Ca2+]i and LH responses to a wide range of GnRH concentrations in the presence and absence of extracellular Ca2+ is consistent with amplification of the [Ca2+]i signal in agonist-stimulated gonadotrops. 相似文献
10.
Integrated cultivation of salmonids and seaweeds in open systems 总被引:2,自引:2,他引:0
Bacterial abundance and production in a vertical profile in Lake Kariba (17dgS), Zimbabwe, were affected by solar irradiance. At the surface, 1.87 × 109 bacteria 1–1 were found and abundance peaked at 10 m (2.5 × 109 bacteria l-1), then decreasing with depth. Bacterial reproduction at the surface(0.145 µg C1–1 h–1) was nearly four times less than the production at 10 m although bacterial numbers were only 26% less. Thus, bacterial production per cell was lower at the surface than deeper down, suggesting that bacterial production is inhibited at the surface.Bacterial production in GF/F filtered lake water in Whirl Pack bags showed an exponential decrease down to 3 m depth. The inhibition was well in accordance with light extinction in the UV region. Phosphatase activity was low in light exposed bags compared to dark, indicating photolysis of extracellular enzymes, or phototransformation of recalcitrant DOM, which substitutes enzyme activity. Hypolimnetic enzyme activity was less affected by solar light than epilimnetic. 相似文献