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61.
Membrane filters prepared from porous aluminum oxide (Anopore) were investigated for their potential use as a durable support for enzymes. Alliinase (EC 4.4.1.4) was chosen as a model enzyme for immobilization experiments. To allow for smooth fixation, the enzyme was immobilized indirectly by sugar-lectin binding. Monomolecular layers of the lectin concanavalin A and alliinase were applied by self-assembling processes. As an anchor for these layers, the sugar, mannan, was covalently coupled to the membrane surface. This procedure exhibits several advantages: (i) enzyme immobilization can be carried out under smooth conditions; (ii) immobilization needs little time; and (iii) protein layers may be renewed. 相似文献
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64.
Filipović B Sosić-Jurjević B Ajdzanović V Trifunović S Manojlović-Stojanoski M Ristić N Nestorović N Milosević V Sekulić M 《Histochemistry and cell biology》2007,128(2):153-159
This study was to evaluate the effect of androgen deficiency on thyroid immunoreactive C-cells and bone structure and function
in a male orchidectomized middle-aged rat model. Fifteen-month-old male Wistar rats were divided into orchidectomized (Orx)
and the sham-operated control (Sham) group. In the Orx group significant decreases (P < 0.05) were found in the volume of C cells (by 14%), their relative volume density (by 13%) and serum calcitonin concentration
(by 54%) compared to the controls. Analyses of trabecular microarchitecture of the proximal tibia metaphysis showed that Orx
induced marked decreases of cancellous bone area, trabecular thickness and trabecular number (by 52, 20 and 19% respectively;
P < 0.05), whereas trabecular separation was increased by 27% (P < 0.05). In Orx rats, serum osteocalcin concentration was increased by 119% (P < 0.05), while serum calcium and phosphorus were 6 and 14% (P < 0.05) lower, respectively, compared to the levels in the Sham. In addition, urine calcium content was considerably higher
(by 129%; P < 0.05) in Orx animals. These findings indicate that the androgen deficiency caused by Orx in middle-aged rats modulated
the structure of C cells and diminished secretion of calcitonin. Histomorphometrical and biochemical analyses demonstrated
a decrease of cancellous bone mass and increased bone turnover. 相似文献
65.
Judith A. Briggs Milka M. Montiel Robert C. Briggs Lubomir S. Hnilica 《Molecular and cellular biochemistry》1987,74(1):29-42
Chicken erythroid nuclei were prepared using four published methods. Our findings indicate that nuclei prepared by nitrogen cavitation are less likely to be contaminated with plasma membrane fragments than those made by procedures involving cell disruption by hypotonic lysis. However, globin gene sequences were much less sensitive to DNase I digestion in nuclei prepared by nitrogen cavitation. This suggests that the conformation of chromatin was altered by the cavitation procedure. Analysis of the proteins solubilized during limited DNase I digestion of nuclei prepared by both hypotonic lysis and cavitation revealed no appreciable differences in HMG proteins but a notable difference in the RNP-associated proteins and core histones.Abbreviations HMG
high mobility group nonhistone chromosomal protein
- RNP
ribonucleoprotein
- SSC
14 mM sodium citrate buffered saline pH 7.0
- PMSF
phenylmethanesulfonyl fluoride
- EDTA
ethylenediaminetetraacetic acid
- DTT
dithiothreitol
- PBS
10 mM sodium phosphate buffered saline pH 7.2
- NP-40
Nonidet P-40 (octylphenoxypolyethoxyethanol)
- SS-DNA
single-stranded DNA
- RSB
reticulocyte standard buffer, 0.01 M NaCl, 0.003 M MgCl2, 0.01 M Tris-HCI, pH 7.4. 相似文献
66.
67.
Trendafilova-Savkova AB Todorova MN Gussev CV 《Zeitschrift für Naturforschung. C, Journal of biosciences》2003,58(11-12):817-819
The aerial parts of Artemisia chamaemelifolia Vill. afforded, in addition to five known sesquiterpene acids, a new 5-epi-cantabrenolic acid (6). 相似文献
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Milka Doktorova Michael V. LeVine George Khelashvili Harel Weinstein 《Biophysical journal》2019,116(3):487-502
Because lipid bilayers can bend and stretch in ways similar to thin elastic sheets, physical models of bilayer deformation have utilized mechanical constants such as the moduli for bending rigidity and area compressibility (KA). However, the use of these models to quantify the energetics of membrane deformation associated with protein-membrane interactions, and the membrane response to stress is often hampered by the shortage of experimental data suitable for the estimation of the mechanical constants of various lipid mixtures. Although computational tools such as molecular dynamics simulations can provide alternative means to estimate KA values, current approaches suffer significant technical limitations. Here, we present a novel, to our knowledge, computational framework that allows for a direct estimation of KA values for individual bilayer leaflets. The theory is based on the concept of elasticity and derives KA from real-space analysis of local thickness fluctuations sampled in molecular dynamics simulations. We explore and validate the model on a large set of single and multicomponent bilayers of different lipid compositions and sizes, simulated at different temperatures. The calculated bilayer compressibility moduli agree with values estimated previously from experiments and those obtained from a standard computational method based on a series of constrained tension simulations. We further validate our framework in a comparison with an existing polymer brush model and confirm the polymer brush model’s predicted linear relationship with proportionality coefficient of 24, using elastic parameters calculated from the simulation trajectories. The robustness of the results that emerge from the method allows us to revisit the origins of the bilayer mechanical (compressible) thickness and in particular its dependence on acyl-chain unsaturation and the presence of cholesterol. 相似文献
70.
Kubale V Abramović Z Pogacnik A Heding A Sentjurc M Vrecl M 《Cell and tissue research》2007,330(2):231-245
This study was focused on the relationship between the plasma-membrane localization of neurokinin-1 receptor (NK1-R) and its
endocytic and signaling properties. First, we employed electron paramagnetic resonance (EPR) to study the domain structure
of HEK-293 cells and NK1-R microlocalization. EPR spectra and the GHOST condensation routine demonstrated that NK1-R was distributed
in a well-ordered domain of HEK-293 cells possibly representing lipid raft/caveolae microdomains, whereas the impairment of
caveolae changed the NK1-R plasma-membrane distribution. Internalization and second messenger assays combined with bioluminescence
resonance energy transfer were employed subsequently to evaluate the functional importance of the NK1-R microlocalization
in lipid raft/caveolae microdomains. The internalization pattern was delineated through the use of dominant-negative mutants
(DNM) of caveolin-1 S80E (Cav1 S80E), dynamin-1 K44A (Dyn K44A), and β-arrestin (β-arr 319–418) and by means of cell lines
that expressed various endogenous levels of β-arrestins. NK1-R displayed rapid internalization that was substantially reduced
by DNMs of dynamin-1 and β-arrestin and even more profoundly in cells lacking both β-arrestin1 and β-arrestin2. These internalization
data were highly suggestive of the predominant use of the clathrin-mediated pathway by NK1-R, even though NK1-R tended to
reside constitutively in lipid raft/caveolae microdomains. Evidence was also obtained that the proper clustering of the receptor
in these microdomains was important for effective agonist-induced NK1-R signaling and for its interaction with β-arrestin2.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This work was supported by the Slovenian Ministry of Higher Education, Science, and Technology (grant number 0406-007) and
a Slovenian-Danish collaboration grant (BI-DK/06-07-007). 相似文献