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排序方式: 共有1007条查询结果,搜索用时 15 毫秒
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2.
G. A. Savin 《Russian Journal of Bioorganic Chemistry》2005,31(6):593-594
The first representatives of phospholipids of new types were synthesized on the basis of dipentaerythritol, 2,2′-[oxybis(methylen)]bis(hydroxymethyl))-1,3-propandiol. The starting polyol was phosphorylated with hexaethylphosphoric triamide to biphosphite, which was converted into thio- and selenophosphates by treatment with sulfur or selenium. The phosphoacetals were transformed into thio- and selenoanalogues of phospholipids by direct acylation with higher fatty acid chlorides. 相似文献
3.
Hanna ten Brink Renske E. Onstein André M. de Roos 《Evolution; international journal of organic evolution》2020,74(8):1826-1850
Although metamorphosis is widespread in the animal kingdom, several species have evolved life-cycle modifications to avoid complete metamorphosis. Some species, for example, many salamanders and newts, have deleted the adult stage via a process called paedomorphosis. Others, for example, some frog species and marine invertebrates, no longer have a distinct larval stage and reach maturation via direct development. Here we study which ecological conditions can lead to the loss of metamorphosis via the evolution of direct development. To do so, we use size-structured consumer-resource models in conjunction with the adaptive-dynamics approach. In case the larval habitat deteriorates, individuals will produce larger offspring and in concert accelerate metamorphosis. Although this leads to the evolutionary transition from metamorphosis to direct development when the adult habitat is highly favorable, the population will go extinct in case the adult habitat does not provide sufficient food to escape metamorphosis. With a phylogenetic approach we furthermore show that among amphibians the transition of metamorphosis to direct development is indeed, in line with model predictions, conditional on and preceded by the evolution of larger egg sizes. 相似文献
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DNA replication is a fundamental process of the cell that ensures accurate duplication of the genetic information and subsequent transfer to daughter cells. Various pertubations, originating from endogenous or exogenous sources, can interfere with proper progression and completion of the replication process, thus threatening genome integrity. Coordinated regulation of replication and the DNA damage response is therefore fundamental to counteract these challenges and ensure accurate synthesis of the genetic material under conditions of replication stress. In this review, we summarize the main sources of replication stress and the DNA damage signaling pathways that are activated in order to preserve genome integrity during DNA replication. We also discuss the association of replication stress and DNA damage in human disease and future perspectives in the field. 相似文献
7.
Jong Wan Park Ho Sub Jung Hea Yeon Lee Tomoji Kawai 《Biotechnology and Bioprocess Engineering》2005,10(6):505-509
For the purpose of developing a direct label-free electrochemical detection system, we have systematically investigated the
electrochemical signatures of each step in the preparation procedure, from a bare gold electrode to the hybridization of label-free
complementary DNA, for the streptavidin-modified electrode. For the purpose of this investigation, we obtained the following
pertinent data; cyclic voltammogram measurements, electrochemical impedance spectra and square wave voltammogram measurements,
in Fe(CN)6
3−/Fe(CN)6
4− solution (which was utilized as the electron transfer redox mediator). The oligonucleotide molecules on the streptavidin-modified
electrodes exhibited intrinsic redox activity in the ferrocyanide-mediated electrochemical measurements. Furthermore, the
investigation of electrochemical electron transfer, according to the sequence of oligonucleotide molecules, was also undertaken.
This work demonstrates that direct label-free oligonucleotide electrical recognition, based on biofunctional streptavidin-modified
gold electrodes, could lead to the development of a new biosensor protocol for the expansion of rapid, cost-effective detection
systems. 相似文献
8.
W. A. B. de Almeida F. de A. A. Mourao Filho B. M. J. Mendes A. P. M. Rodriguez 《Biologia Plantarum》2006,50(3):321-325
The adventitious bud development was induced in epicotyl segments of Valencia sweet orange (Citrus sinensis L. Osbeck). Seeds were cultured in vitro for three weeks in the dark, followed by one week at a 16-h photoperiod. Epicotyl segments were cultured horizontally for
the induction of organogenesis in Murashige and Tucker (1969, MT) culture medium supplemented with 1.0 mg dm−3 benzylaminopurine. Samples were observed by light and scanning electron microscopy from day zero to day 25, when buds were
well grown. It was shown that the adventitious buds originated directly from the cambial region on the cut ends of the explants. 相似文献
9.
Oncidium cultivars gave different embryogenic responses of leaf explants when affected by auxins (2,4-D, IAA, IBA and NAA), cytokinins
(2iP, BA, kinetin, TDZ and zeatin), sucrose, NaH2PO4, casein hydrolysate, peptone, and glutamine. The best embryogenic responses of cv. Sweet Sugar were at 20 g dm−3 sucrose, 85 mg dm−3 NaH2PO4 and 3 mg dm−3 kinetin, respectively. The development of somatic embryos on leaf explants of cv. Sweet Sugar was delayed for about 10 –
20 d in comparison with cv. Gower Ramsey. On growth regulator-free medium, about 40 % of leaf derived embryos of cv. Gower
Ramsey were fused together in their basal parts and so called multiple-state embryos. However, under the same condition, the
embryos of cv. Sweet Sugar were all in multiple-state form. 相似文献
10.
筛选了一株产纤溶酶能力较强的芽孢细菌,本文对其液体发酵条件进行了优化,结果表明菌株产酶最佳条件为:可溶性淀粉4%,蛋白胨2%,柠檬酸铁铵0.1%,磷酸钙0.4%,接种量2%,pH 7.5,发酵时间96 h,装瓶量75/500(mL/mL),摇床温度37℃,转速150 rpm,在该条件下产酶酶活可达581.81 IU/mL。 相似文献