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991.
Cano A Moschou EA Daunert S Coello J Palet C 《Bioprocess and biosystems engineering》2006,29(4):261-268
The aim of this work was the development and optimization of enzymatic monolithic membranes with high catalytic activity for the degradation of xylan into xylooligosaccharides. The chemometric tool design of experiments has been utilized here for the first time for the optimization of the enzymatic activity of the monolithic membranes based on their constituents. The effect of three process variables, including the amount of various monomer contents and the porogenic solvents ratio, has been studied on the enzymatic activity of the resulted membranes. The experimental design chosen was a central face centred with six central points in order to obtain an orthogonal model, with the precision of the results being independent of the range of values considered for each parameter. The software Modde(c) 6.0 from Umetrics(c) was used to build and analyze the results of the experimental design using partial least squares regression. The optimization of the suggested model provided the best membrane composition to achieve maximum enzymatic activity, which can be related to the amount of enzyme immobilized on the monolithic membrane. The predictive capacity of the model was evaluated performing additional experiments. 相似文献
992.
Garcia-Fernàndez J 《International journal of biological sciences》2006,2(2):30-31
The cephalochordate amphioxus occupies a central place in evolutionary thoughts to the origin of Vertebrates. With a prototypical vertebrate-like body plan and a preduplicative genome, the friendly lancelet seems to be in morphological and genetic motionless since its separation from the major branch of evolution that eventually ended up in our corner in the Animal Kingdom. This makes it an ideal model system with which, with the current development of genomic and experimental tools, an Evo-Devo approach to the understanding of the origin of vertebrates looks proper, reliable, and excitingly promising. 相似文献
993.
Jiménez-Delgado S Crespo M Permanyer J Garcia-Fernàndez J Manzanares M 《International journal of biological sciences》2006,2(2):66-72
Amphioxus Hairy genes have gone through a number of lineage-specific duplications, resulting in eight members, some of which are differentially expressed in the embryo. In order to gain insights into the evolution and function of this gene family we have compared their genomic structure and searched for conserved non-coding sequence elements. We have found that introns have been lost independently from these genes at least twice and after the duplication events. By carrying out phylogenetic footprinting between paralogues expressed in the embryo, we have found a differential distribution of conserved elements that could explain the limited overlap in expression patterns of Hairy genes in the amphioxus embryo. Furthermore, clustering of RBP-Jk binding sites in these conserved elements suggests that amphioxus Hairy genes are downstream targets of the Notch signaling pathway, as occurs in vertebrates. All of this evidence suggests that amphioxus Hairy genes have gone through a process of subfunctionalization shortly after their duplication, representing an extreme and rapid case of the duplication-degeneration-complementation model. 相似文献
994.
Burrow decorations as antipredatory devices 总被引:1,自引:0,他引:1
Animal decorations are normally interpreted as signals of quality.In spiders, however, decorations may have different functions,including the attraction of prey to the web or making the spidercryptic to predators. To date, there is scant evidence for thelatter hypothesis. Here we use the burrow-decorating wolf spiderLycosa tarantula to test whether turrets around the burrow serveto prevent burrow invasion and predation from the Occitan scorpionButhus occitanus. We located spiders and scorpions in fieldenclosures and manipulated the presence or absence of decorationsor turrets. We found that the presence of the turret decreasesthe rate of burrow invasion and improves spider survival, possiblybecause the turret makes the burrow cryptic to scorpions. Inaddition, a field survey showed that burrows with larger decorationshad a lower chance of being invaded by scorpions. These resultsprovide evidence that the decoration has an antipredatory functionin nature. 相似文献
995.
The brine shrimp Artemia sp. as alternative prey for rearing the predatory bug Macrolophus caliginosus 总被引:1,自引:0,他引:1
The predatory bug Macrolophus caliginosus, which is widely used in greenhouse crops, is limited in its application by its high price. An important factor in the cost is the high price of Ephestia kuehniella eggs, the prey used in their mass rearing. In order to reduce their price, alternatives to moth eggs are currently being investigated. The brine shrimp Artemia sp. is produced in large quantities in saline lakes and is fed as live food source to the larvae of a variety of marine and freshwater organisms. In this study, we tested Artemia sp. as prey for rearing M. caliginosus from two strains. We evaluated developmental and reproduction parameters of the predator when fed nauplii, enriched nauplii with a fatty acid, dry cysts and hydrated cysts, and were compared with those obtained when the predator was fed with E. kuehniella eggs. Nauplii had a significant reduction in survivorship, a delay in development of nymphs and a low reproduction of adults. Nauplii enriched with docosahexaenoic acid (DHA, 22:6n − 3), a common practice for larviculture of some marine fish species, resulted toxic to M. caliginosus nymphs and survival was quite low. On the contrary, either dry or hydrated cysts from the two strains tested of the brine shrimp produced the same nymphal survivorship, nymphal development time and weight and fecundity of adults as those obtained with E. kuehniella eggs. Demographic parameters of the eighth generation of the predator reared with cysts of the two strains, either dry or hydrated, were as good as those of moth eggs. We concluded that Artemia sp. cysts were a good substitution prey for the mass rearing of M. caliginosus. 相似文献
996.
Alemán C Zanuy D Jiménez AI Cativiela C Haspel N Zheng J Casanovas J Wolfson H Nussinov R 《Physical biology》2006,3(1):S54-S62
Physically building complex multi-molecular structures from naturally occurring biological macromolecules has aroused a great deal of interest. Here we focus on nanostructures composed of re-engineered, natural 'foldamer' building blocks. Our aim is to provide some of the underlying concepts and schemes for crafting structures utilizing such conformationally relatively stable molecular components. We describe how, via chemical biology strategies, it is further possible to chemically manipulate the foldamer building blocks toward specific shape-driven structures, which in turn could be used toward potential-designed functions. We outline the criteria in choosing candidate foldamers from the vast biological repertoire, and how to enhance their stability through selected targeted replacements by non-proteinogenic conformationally constrained amino acids. These approaches combine bioinformatics, high performance computations and mathematics with synthetic organic chemistry. The resulting artificially engineered self-organizing molecular scale structures take advantage of nature's nanobiology toolkit and at the same time improve on it, since their new targeted function differs from that optimized by evolution. The major challenge facing nanobiology is to be able to exercise fine control over the performance of these target-specific molecular machines. 相似文献
997.
Monfort J Garcia-Giralt N López-Armada MJ Monllau JC Bonilla A Benito P Blanco FJ 《Arthritis research & therapy》2006,8(5):R149-11
Articular cartilage is optimised for bearing mechanical loads. Chondrocytes are the only cells present in mature cartilage
and are responsible for the synthesis and integrity of the extracellular matrix. Appropriate joint loads stimulate chondrocytes
to maintain healthy cartilage with a concrete protein composition according to loading demands. In contrast, inappropriate
loads alter the composition of cartilage, leading to osteoarthritis (OA). Matrix metalloproteinases (MMPs) are involved in
degradation of cartilage matrix components and have been implicated in OA, but their role in loading response is unclear.
With this study, we aimed to elucidate the role of MMP-1 and MMP-3 in cartilage composition in response to mechanical load
and to analyse the differences in aggrecan and type II collagen content in articular cartilage from maximum- and minimum-weight-bearing
regions of human healthy and OA hips. In parallel, we analyse the apoptosis of chondrocytes in maximal and minimal load areas.
Because human femoral heads are subjected to different loads at defined sites, both areas were obtained from the same hip
and subsequently evaluated for differences in aggrecan, type II collagen, MMP-1, and MMP-3 content (enzyme-linked immunosorbent
assay) and gene expression (real-time polymerase chain reaction) and for chondrocyte apoptosis (flow cytometry, bcl-2 Western
blot, and mitochondrial membrane potential analysis). The results showed that the load reduced the MMP-1 and MMP-3 synthesis
(p < 0.05) in healthy but not in OA cartilage. No significant differences between pressure areas were found for aggrecan and
type II collagen gene expression levels. However, a trend toward significance, in the aggrecan/collagen II ratio, was found
for healthy hips (p = 0.057) upon comparison of pressure areas (loaded areas > non-loaded areas). Moreover, compared with normal cartilage, OA
cartilage showed a 10- to 20-fold lower ratio of aggrecan to type II collagen, suggesting that the balance between the major
structural proteins is crucial to the integrity and function of the tissue. Alternatively, no differences in apoptosis levels
between loading areas were found – evidence that mechanical load regulates cartilage matrix composition but does not affect
chondrocyte viability. The results suggest that MMPs play a key role in regulating the balance of structural proteins of the
articular cartilage matrix according to local mechanical demands. 相似文献
998.
Diphenylamine (DPA), 2-hydroxybiphenyl (OHBP) and 9-fluorenone (9-F), known inhibitors of carotenoids (car) synthesis, altered
the pattern of incorporation of 2-14C-mevalonate into car in ripening fruits ofCapsicum annuum. OHBP was the most powerful inhibitor of the whole process of biosynthesis, followed by DPA and 9-F. The most sensitive step
was the dehydrogenation of phytofluene. Cyclization of β-carotene and isomerizations yielding the structure of hydroxy-cyclopentane
were also affected, although to a lesser extent. 相似文献
999.
Investigations on the insertion of the mitochondrial precursor protein apocytochrome c into model membranes 总被引:2,自引:0,他引:2
A Rietveld G A Ponjee P Schiffers W Jordi P J van de Coolwijk R A Demel D Marsh B de Kruijff 《Biochimica et biophysica acta》1985,818(3):398-409
Different aspects of the interaction of apocytochrome c and model membranes composed of negatively charged lipids, were studied in order to get insight into the nature of this interaction. The effect of the protein on the lipid packing properties are revealed by DSC, ESR and monolayer techniques. These experiments clearly demonstrate that upon electrostatic interaction with the negatively charged phospholipids, apocytochrome c is able to penetrate into the hydrophobic region of the model membrane. In the case of 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol, this results in a perturbation of 160 lipid molecules per apocytochrome c molecule. Most likely, apocytochrome c disrupts the formation of the gel phase and restricts the lipid chain motion above the gel to liquid-crystalline phase transition. Tryptophan fluorescence measurements confirm that at least a part of the protein penetrates into the bilayer, and suggest that after this penetration, the tryptophan (residue no. 59) is located in the glycerol backbone region of the phospholipids. Although the secondary structure of apocytochrome c is predicted to contain about 35% of alpha-helical structure, the CD pattern of an aqueous solution of the protein is featureless. However, negatively charged lipids are able to express this alpha-helical potency in the apocytochrome c, which might be important for the insertion of the protein into lipid membranes. 相似文献
1000.
Marek Mentel Jure Pi?kur Cécile Neuvéglise Adriana Ry?ovská Gabriela Cellengová 《Folia microbiologica》1999,44(2):219-240