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141.
Two field experiments were carried out totest whether effects of intraspecific competition ina Littorina littorea population can be detectedin a short-term investigation. Different size classesof L. littorea showed no significant differencein preferences when offered four kinds of eitherpossible food or substrata (Fucus vesiculosus,Ulva lactuca, Carcinus maenas, brick).Large and medium winkles preferred Fucusvesiculosus, followed by Ulva lactuca. Deadshore crabs (Carcinus maenas) were the leastpreferred objects for all size classes. On the firstday of the experiment bricks were more attractive tosmall littorines than to larger ones. Considering allfour days, the same ranking occurred for all sizeclasses: Fucus vesiculosus > Ulvalactuca > brick > Carcinus maenas. The reactionofjuveniles to increased densities was examined using anin situ caging experiment on a mussel bed. Meshsize of the cages allowed adult densities to beincreased while juveniles could escape by passingthrough the meshes. However, there was no significantemigration of small winkles even from cages with 10 to20 times natural density of large individuals. Ofgreater importance was the original number of winklesat the site. The available resources on the musselbeds appear to be sufficient to maintain a highpopulation density. Intraspecific competition does notseem to play a major role in this L. littorea-population. 相似文献
142.
The effects of different seed sizes, planting densities and planting patterns on the transmission of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes were examined in five field experiments with cv. Estima in 1991–93.
In all experiments, silver scurf was more severe with increase in seed size and planting density. At high planting density, silver scurf was less severe from a square planting pattern than from planting in wide rows. The incidence of black scurf also tended to increase with increase in seed size and was increased markedly high planting density. 相似文献
In all experiments, silver scurf was more severe with increase in seed size and planting density. At high planting density, silver scurf was less severe from a square planting pattern than from planting in wide rows. The incidence of black scurf also tended to increase with increase in seed size and was increased markedly high planting density. 相似文献
143.
Lemaster DM 《Journal of biomolecular NMR》1995,6(4):366-374
Summary The Lipari-Szabo dynamical formalism is extended by setting the time constants of the Lorentzian terms to
and
. This analysis is compared to the earlier proposed three-parameter
extended model free formalism with regard to the range of equivalence and the advantages of the simplified two-parameter (S
inff
sup2
,S
infH
sup2
) and (S
inff
sup2
,S
infN
sup2
) representations. Spectral density components are calculated and compared to those obtained from the spectral density analysis formalism. Protein relaxation data, commonly analyzed in terms of the two-parameter
representation, may correspond to a dynamically heterogeneous behaviour that is more appropriately represented in terms of a fast limit order parameter and a second, lower frequency order parameter. 相似文献
144.
HPLC-analysis of algal pigments: comparison of columns,column properties and eluents 总被引:1,自引:0,他引:1
The effects of columns (Nucleosil C18ODS, MZ-PAH, YMC-PACK C30), column properties (inner diameters of 4 mm, 3 mm and 2 mm, pore-width 10 nm and 30 nm) and eluents (methanol, acetonitrile,
acetone, water) were tested on the separation of algal pigments. The length of columns was 250 mm and particle size was 5
μm. Flow rates and gradients were adjusted to optimize peak separation; remaining chromatographic conditions were kept constant.
The resolution of chromatographic systems was tested with pigment standards and various algal cultures. Total flow rate and
retention times decreased with decreasing inner diameter, whereas pressure, sensitivity and peak-width increased. Pore width
had negligible effects on the chromatographic separation of pigments under the test conditions. Only with acetonitrile as
eluent were all the taxonomically important pigments resolved adequately: zeaxanthin (Cyanophyceae), lutein (Chlorophyceae),
fucoxanthin (Bacillariopyceae), alloxanthin (Cryptophyceae), peridinin (Dinophyceae). 相似文献
145.
Peter Allard Jüri Jarvet Anders Ehrenberg Astrid Gräslund 《Journal of biomolecular NMR》1995,5(2):133-146
Summary The peptide hormone motilin was synthesised with a 13C-enriched -carbon in the leucine at position 10. In aqueous solution, six different relaxation rates were measured for the 13C–H fragment as a function of temperature and with and without the addition of 30% (v/v) of the cosolvent d
2-1,1,1,3,3,3-hexafluoro-2-propanol (HFP). The relaxation rates were analysed employing the spectral density mapping technique introduced by Peng and Wagner [(1992) J. Magn. Reson., 98, 308–322] and using the model-free approach by Lipari and Szabo [(1982) J. Am. Chem. Soc., 104, 4546–4570]. The fit to various models of dynamics was also considered. Different procedures to evaluate the overall rotational correlation time were compared. A single exponential time correlation function was found to give a good fit to the measured spectral densities only for motilin in 30% (v/v) HFP at low temperatures, whereas at high temperatures in this solvent, and in D2O at all temperatures, none of the considered models gave an acceptable fit. A new empirical spectral density function was tested and found to accurately fit the experimental spectral density mapping points. The application of spectral density mapping based on NMR relaxation data for specific 13C–1H vector is shown to be a highly useful method to study biomolecular dynamics. Advantages are high sensitivity, high precision and uniform sampling of the spectral density function over the frequency range.Abbreviations CD
circular dichroism
- NOE
nuclear Overhauser enhancement
- NOESY
two-dimensional NOE spectroscopy
- INEPT
insensitive nuclei enhanced by polarisation transfer
- DANTE
delays alternating with nutations for tailored excitation
- WALTZ-16
wideband, alternating phase, low-power technique for zero residual splitting
- FID
Free induction decay
- ppm
parts per million
- TSPA
3-trimethylsilyl-(3,3,2,2-d)-propionic acid
- HFP
d
2-1,1,1,3,3,3-hexafluoro-2-propanol
- CPMG
Carr-Purcell-Meiboom-Gill
- TFD
time-resolved fluorescence depolarisation
- CSA
chemical shift anisotropy
Partly presented at the symposium Dynamics and Function of Biomolecules, Szeged, Hungary, July 31–August 2, 1993. 相似文献
146.
Shu’a Yagev Michael Heller Arié Pinson 《In vitro cellular & developmental biology. Plant》1984,20(12):893-898
Summary Postnatal rat heart cells in culture enriched with respect to muscle cells were obtained by either high density seeding or
by the replating technique. [3H]Thymidine incorporation to DNA and the enzymatic pattern of cytoplasmic and lysosomal enzymes have been studied as a function
of the culture’s age, of seeding density, and replating. It was shown that (a) replating maintains predominance of myocyte
population for at least 2 wk in culture; (b) heavy seeding density allows homogeneous myocyte population for the 1st wk in
culture; and (c) the enzyme profile of the culture may serve as an indicator for the type of cell population in culture and
its state of differentiation.
This study was done as partial fulfilment of the M.Sc. thesis in Biochemistry (SY). Supported by grants from The Chief Scientist,
Ministry of Health, State of Israel; The Ministry of Education and Sciences, State of Niedersachssen (FRG); and The Foundation
for Heart Research from Mr. and Mrs. D. Vidal-Madjar, Paris, France. 相似文献
147.
James S. Clegg 《Cell biochemistry and biophysics》1984,6(3):153-169
Cysts of the crustaceanArtemia are a useful model for studies on intracellular water because they are capable of essentially complete and reversible desiccation.
We have used a variety of techniques on this system, the present work being an attempt to estimate the density of intracellular
water (ρw). The density of individual cysts was evaluated from sedimentation velocity. Heptane displacement methods were used to determine
the volume of a known mass of cysts, from which the density was calculated. The two methods produce comparable results. It
was shown that the densities and water contents of large masses of cysts accurately reflect those of individual cysts. Cyst
densities (ρc) were determined over the entire range of water content from 0 to 0.63 weight fraction of water (W
f), and temperature dependence was measured for 0.61W
f over 2–41°C. The following refer to 25°C. No marked change was detected in ρc until the water content exceeded 0.15W
f, at which ρc decreased as a linear function of Wf to maximum water content. However, the cyst does not behave ideally in the sense that
the densities of the nonaqueous components and added water are not additive as a function ofW
f. The partial specific volume of water in cysts at maximum hydration was estimated to be 3% larger than that of pure water.
These observations are compared with density measurements on other systems, and with previous findings on the physical properties
of water in this system. 相似文献
148.
S P Verma J R Philippot B Bonnet J Sainte-Marie Y Moschetto D F Wallach 《Biochemical and biophysical research communications》1984,122(2):867-875
Low-density lipoproteins isolated between density 1.02 and 1.063 g/cm3 from normal fasting human plasma, show strong resonance Raman spectra due to the presence of beta-carotene. Three intense bands, at 1010, 1160 and 1530 cm-1, are assigned to the stretching vibrations of -C-CH3, = C-C = and -C = C- bonds, respectively, of beta-carotene. High-resolution spectra of the 1500-1600 cm-1 region reveal multiple features, suggesting the coexistence of several structural populations of beta-carotene. The modifications of lipoproteins with pH and temperature (30 degrees-42 degrees) change the resonance Raman spectra of beta-carotene. The specific binding of LDL at pH 7.0 by fibroblast cells is suppressed. Our experiments thus suggest that physical and chemical perturbations of plasma lipoproteins modify the lipid-protein interactions and thereby alter the configurational distribution of beta-carotene molecules within these particles. 相似文献
149.
Dispersal of adult Viburnum whitefly,Aleurotrachelus jelinekii (Frauenf.) was assessed over a period of 6 years, both in the field and in the laboratory. Flight activity did not appear to be strongly affected by normal variation in either temperature or windspeed. The aerial density of flying adults decreased rapidly with distance from the host plant. Movement up to 5 m from the host plant was found to be density dependent, although there is no suggestion that longer flights become more frequent at higher population densities. More males were caught at the beginning of the season and the number of males flying increased as the population density rose. Insects were flight mature after about 3 h, but flew readily only after 2 days. Longer flights were observed from younger females at a time when they would move from old to young leaves. Landing site preference was not recorded, which contrasts with the behaviour of the cabbage whitefly. Flight in the Viburnum whitefly appears to redistribute the population within the immediate habitat, but migration did not appear to be a significant demographic factor in the isolated populations studied.
Etude de l'activité de vold d'Aleurotrachelus jelinekii peu enclin au vol
Résumé La dispersion des adultes d'Aleurotrachelus jelinekii Frauenf, tant dans la nature qu'au laboratoire, a été estimée sur une période de 6 ans. L'activité de vol n'a pas paru être fortement modifiée par les variations de la température et de la vitesse du vent. Le nombre d'adultes en vol a diminué rapidement jusqu'à 5 m de la plante hôte, et il était density-dependent, bien que rien ne prouve que les vols les plus longs deviennent plus fréquents à des densités de population plus élevées. Plus de mâles ont été capturés au début de la saison et le nombre de mâles en vol s'est accru avec la densité de la population. Les insectes étaient aptes au vol 3 heures après la mue imaginale, mais ne volaient normalement que 2 jours après. Les vols les plus longs ont été observés chez les plus jeunes femelles au moment où elles devaient migrer de feuilles âgées à des feuilles jeunes. Les lieux d'atterrissage préférés n'ont pas été décelés. Le vol chezA. jelinekii semble redistribuer la population dans l'habitat immédiat et la migration n'apparaît pas être un paramètre démographique significantif dans les populations isolées étudiées.相似文献
150.
A complete synthesis of 1-O-hexadecyl-2-O-N-(heptadec-8-cis-enyl)carbamyl-sn-glycero-3-Phosphocholine, a novel analog of phosphatidylcholine, has been described. Each step is simple to perform and gives the desired products in high yield. Also, some of the intermediates formed during the synthesis have been efficiently utilized to prepare 1-O-hexadecyl-2-O-oleyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-2-oleoyl-sn-glycero-3-phosphochloine and 3-O-hexadecyl-2-oeloyl-sn-glycero-1-phosphocholine. These phosphatidylcholine (PC) analogs are useful for studying the possible role of phospholipases in the capture and lyses of liposomes in vivo. 相似文献