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1.
The desulfurization activity of the resting cells of Gordona sp. CYKS1 was strongly depended on harvest time and the highest value when the cells had been harvested in the early growth phase (0.12 mg sulfur g–1 cell–1 h–1). For the model oil, hexadecane containing dibenzothiophene, the specific desulfurization rate decreased as the reaction proceeded. Both the specific and the volumetric desulfurization rates were not significantly affected by the aqueous-to-oil phase ratio. The diesel oils, light gas oil and a middle distillate unit feed were desulfurized at higher rates (ca. 0.34 mg sulfur g–1 cell–1 h–1) than the model oil (0.12 mg sulfur g–1 cell–1 h–1). 相似文献
2.
Comparison of bone marrow extracellular matrices. 总被引:1,自引:0,他引:1
M Lee I P Christopherson J M Lehman C J Bennett H T Cheung 《Biochimica et biophysica acta》1999,1428(2-3):300-304
We have compared the structure and composition of adult and fetal bovine bone marrow extracellular matrices. In contrast to fetal bone marrow, adult bone marrow has more oval fenestration and accumulation of adipocytes as well as lower protein content. These differences could be due to remodeling of bone marrow tissue as it develops. Zymogram analysis of matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) activities showed that fetal, but not adult bone marrow extract contained a 96-kDa MMP and TIMP-1 and -2. These activities may contribute to the structural differences between adult and fetal bone marrow tissues. 相似文献
3.
Yen Sun 《Biophysical journal》2010,99(2):544-552
Recently we have studied thermodynamics of membrane-mediated β-amyloid formation in equilibrium experiments using penetratin-lipid mixtures. The results showed that penetratin bound to the membrane interface in the α-helical conformation when the peptide/lipid (P/L) ratios were below a lipid-dependent critical value P/L∗. When P/L reached P/L∗, small β-aggregates emerged, which served as the nuclei for large β-aggregates. Here we studied the corresponding kinetic process to understand the potential barriers for the membrane-mediated β-amyloid formation. We performed kinetic experiments using giant unilamellar vesicles made of 7:3 DOPC/DOPG. The observed time behavior of individual giant unilamellar vesicles, although complex, exhibited the physical effects seen in equilibrium experiments. Most interestingly, a potential barrier appeared to block penetratin from translocating across the bilayer. As a result, the kinetic value for the critical threshold P/L∗ is roughly one-half of the value measured in equilibrium where peptides bind symmetrically on both sides of lipid bilayers. We also investigated the similarity and differences between the charged and neutral lipids in their interactions with penetratin. We reached an important conclusion that the bound states of peptides in lipid bilayers are largely independent of the charge on the lipid headgroups. 相似文献
4.
Formation of rings from Drosophila DNA fragments 总被引:1,自引:0,他引:1
5.
Single-chamber microbial fuel cell (SMFC)-I consisted of 4 separator-electrode assemblies (SEAs) with two types of cation exchange membrane (CEM: Nafion and CMI 7000) and an anion exchange membrane (AEM: AMI 7001). SMFC-II consisted of 4 SEAs with Nafion and three types of nonwoven fabric. SMFC-I and -II were inoculated with anaerobic digested and activated sludge, respectively, and operated under fed-batch mode. In SMFC I, AEM-SEA showed a maximum power density (PDmax). Nafion-SEA showed a PDmax in SMFC II, which was similar to that of Nafion–SEA of SMFC I. Although different bacteria were developed in SMFC-I (Deltaproteobacteria and Firmicutes) and SMFC-II (Gammaproteobacteria, Betaproteobacteria and Bacteroidetes), the inoculum type little affects electricity generation. Variations of pH and oxygen in biofilm have influenced microbial community structure and electricity generation according to the electrode and separator material. Although the electricity generation of non-woven fabric-SEA was less than that of Nafion-SEA, the use of non-woven fabrics is expected to reduce the construction and operating costs of MFCs. 相似文献
6.
1. As trees age, they undergo significant physiological and morphological changes. Nevertheless, tree ontogeny and its impacts on herbivores are often overlooked as determinants of plant–herbivore population dynamics and the strength of plant–herbivore interactions. 2. Juniperus (Cupressaceae) is a dominant, long‐lived conifer that serves as the sole host to a specialised assemblage of caterpillars. Over the past 150 years, several juniper species in western North America have expanded their geographic occupancy at local and regional scales, which has resulted in an increase in the number of immature trees on the landscape. Using assays in the laboratory, the effects of tree ontogeny on caterpillar performance and oviposition preference for two juniper specialist caterpillars, Callophrys gryneus (Lycaenidae) and Glena quinquelinearia (Geometridae), were examined. The study considered whether responses to tree ontogeny were consistent across caterpillar species and juniper host species. 3. Tree age was found to be a reliable predictor of caterpillar performance, with caterpillars developing more quickly and growing larger when fed foliage from young trees. Differences in the phytochemical diversity between foliage from trees of different ages might help to explain observed differences in caterpillar performance. Interestingly, the specialist butterfly, C. gryneus, displayed an oviposition preference for foliage from old‐growth Juniperus osteosperma trees, despite the fact that larvae of this species performed poorly on older trees. 4. It is concluded that young juniper trees are an important resource for the specialised Lepidopteran community and that tree ontogeny is an important component of intraspecific variation, which contributes to the structure of plant–herbivore communities. 相似文献
7.
The Asian Tree Toad genus Pedostibes, as currently understood, exhibits a conspicuously disjunct distribution, posing several immediate questions relating to the biogeography and taxonomy of this poorly known group. The type species, P. tuberculosus and P. kempi, are known only from India, whereas P. hosii, P. rugosus, and P. everetti are restricted to Southeast Asia. Several studies have shown that these allopatric groups are polyphyletic, with the Indian Pedostibes embedded within a primarily South Asian clade of toads, containing the genera Adenomus, Xanthophryne, and Duttaphrynus. Southeast Asian Pedostibes on the other hand, are nested within a Southeast Asian clade, which is the sister lineage to the Southeast Asian river toad genus Phrynoidis. We demonstrate that Indian and Southeast Asian Pedostibes are not only allopatric and polyphyletic, but also exhibit significant differences in morphology and reproductive mode, indicating that the Southeast Asian species’ are not congeneric with the true Pedostibes of India. As a taxonomic solution, we describe a new genus, Rentapia
gen. nov. to accommodate the Southeast Asian species. 相似文献
8.
9.
State of aggregation of the (Ca2+ + Mg2+)-ATPase studied using saturation-transfer electron spin resonance 总被引:1,自引:0,他引:1
The state of aggregation of the (Ca2+ + Mg2+)-ATPase in the membrane of sarcoplasmic reticulum and in reconstituted membrane systems has been studied using saturation-transfer electron spin resonance (ST-ESR). Saturation-transfer ESR spectra show that in the sarcoplasmic reticulum, the ATPase is relatively free to rotate, with an effective rotational correlation time of approx. 33 microseconds at 4 degrees C, consistent with a monomeric or dimeric structure. The rate of rotation is observed to decrease with decreasing molar ratio of lipid to protein. In reconstituted systems, rotational motion of the ATPase on the millisecond time scale ceases when the lipids are in the gel phase. Addition of decavanadate, which causes the formation of crystalline arrays in negatively stained electron micrographs, results in only a small reduction in rotation rate for the ATPase in the membrane. The experiments are interpreted in terms of a short-lived (on the millisecond time scale) protein-protein interaction, with the formation of crystalline clusters of ATPase molecules which form and melt rapidly. 相似文献
10.