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21.
Synthesis and biochemical inhibition studies of a novel transition state analog inhibitor of guanase bearing the ring structure of azepinomycin have been reported. The compound was synthesized in five-steps from a known compound and biochemically screened against the rabbit liver guanase. The compound exhibited competitive inhibition profile with a Ki of 16.7 ± 0.5 μM.  相似文献   
22.
The incorporation of radioactive aminolevulinic acid (ALA) into chlorophyll (Chl) a and b , as well as protochlorophyllide (Pchlide) in light-grown barley seedlings ( Hordeum vulgare L. cv. Clipper) transferred to darkness is demonstrated.
In the experiments described, 6-day-old, glasshouse-grown seedlings were transferred to darkness and incubated in [14C]- or [3H]- ALA for 18 h.
Chl a and b were extracted and purified to constant specific radioactivity by HPLC and TLC of their magnesium-free derivatives, pheophytin a and b . The presence of label in the tetrapyrrole ring of the Chls was established by removal of the phytol chain by alkaline hydrolysis and determination of the specific radioactivity of the chlorin e 6 and rhodin g 7 derivatives.
Barley seedlings that had been grown in darkness for 5 days, transferred to light for 20 h, and then returned to darkness in the presence of radioactive ALA also incorporated label into Chl. However, this was only apparent in intact seedlings. Excised leaves from greened etiolated plants did not incorporate ALA into Chl in darkness. This was consistent with the finding of Apel et al. (K. Apel, M. Motzkus and K. Dehesh, 1984. Planta 161: 550–554) and may account for their failure to obtain evidence for a light-independent protochlorophyllide reductase in greening barley.
Although the incorporation of ALA into Chl compared to Pchlide was slight (5%), the presence of label in the tetrapyrrole nucleus of Chl a and b is unequivocal evidence of a light-independent pathway of Chl biosynthesis in barley that has been exposed to light during development. Limited entry of exogenous labelled ALA into the precursor pools leading to the dark reduction of Pchlide is postulated.  相似文献   
23.
Criconemella xenoplax, Fusarium solani, and F. oxysporum caused necrosis of Nemaguard peach feeder roots in greenhouse tests. Root necrosis was more extensive in the presence of either fungus than wtih C. xenoplax alone. Shoot growth and plant height were less for plants inoculated with F. oxysporum or F. solani than for plants inoculated with the fungi plus C. xenoplax. Neither synergistic nor additive effects on root necrosis or plant growth occurred between C. xenoplax and the fungal pathogens.  相似文献   
24.
树线交错带是具有强烈生物交互作用的高寒生态过渡带,生物互作与树线生态过程密切相关。本研究系统综述了气候变化下植物间、动植物间和微生物与植物间互作因子对树线生态过程的影响。植物间互利或竞争作用的强度调控变暖背景下树线生态过程的变化,目前尚缺少树轮生态学证据,且亟待检验高阶互作的适用性;动物采食活动、微生物与植物间互作可通过影响土壤状况、改变树木生长和更新等生态过程动态,增强或削弱树线与气候间耦合关系。迄今为止,地下与地上过程联系如何影响气候变暖下的树线动态尚不明晰,而营养级间互作可能调制树线生态过程对气候响应。青藏高原等高寒区具有开展此类研究的优势与潜力。  相似文献   
25.
2-,3-,4-Pyridylphosphonates and their phosphonothioate congeners were analyzed by electrospray ionization multistage tandem mass spectrometry (ESI-MSn). It was found that the fragmentation pathways of these compounds were not influenced to any detectable extent by the stereochemistry at the phosphorus centers but were sensitive to the position of a nitrogen atom in the pyridine ring of these compounds. Possible mechanisms for fragmentations of the investigated compounds are discussed in detail.

  相似文献   
26.
The genus Buergenerula in driftwoods and culms of Spartina alterniflora in intertidal zone is newly recorded from China seas. Taxonomy and morphology of Buergenerula spartinae and the comparison between the species and similar species were discussed in this paper. The specimens were deposited in Mycology Herbarium at Qingdao Agricultural University (MHQAU).  相似文献   
27.
28.
本研究以体外微血管培养模型为基础,用鼠尾胶原包埋大鼠动脉环,并将包埋的动脉环转移到种有人肺癌A549细胞单层的培养皿中,用MCDB 131无血清培养液对动脉环和肿瘤细胞进行共培养,从而建立肿瘤微血管体外生成模型。大鼠动脉环于培养后第3天从血管壁长出微血管芽,第6至10天长成微血管丛,两周后新生微血管开始萎缩;没有肿瘤细胞刺激的条件下,大鼠动脉环新生微血管数量明显减少。结果表明人肺癌A549细胞能够促进血管生成。体外大鼠动脉环肿瘤微血管培养模型操作简单、灵敏度高,适合研究肿瘤血管新生及其机制。  相似文献   
29.
F(o)F(1)-ATP synthase mediates coupling of proton flow in F(o) and ATP synthesis/hydrolysis in F(1) through rotation of central rotor subunits. A ring structure of F(o)c subunits is widely believed to be a part of the rotor. Using an attached actin filament as a probe, we have observed the rotation of the F(o)c subunit ring in detergent-solubilized F(o)F(1)-ATP synthase purified from Escherichia coli. Similar studies have been performed and reported recently [Sambongi et al. (1999) Science 286, 1722-1724]. However, in our hands this rotation has been observed only for the preparations which show poor sensitivity to dicyclohexylcarbodiimde, an F(o) inhibitor. We have found that detergents which adequately disperse the enzyme for the rotation assay also tend to transform F(o)F(1)-ATP synthase into an F(o) inhibitor-insensitive state in which F(1) can hydrolyze ATP regardless of the state of the F(o). Our results raise the important issue of whether rotation of the F(o)c ring in isolated F(o)F(1)-ATP synthase can be demonstrated unequivocally with the approach adopted here and also used by Sambongi et al.  相似文献   
30.
We present a pregnant woman with mental retardation and mosaic for ring 18 referred for prenatal diagnosis. Major clinical features included short stature with clinodactyly in feet, foot deformity and club feet, hypotonia, kyphosis, and absence of breast development, low set ears, high arched palate, dental decay and speech disorder. Prenatal diagnosis was carried. Using amniocentesis. The fetus had a normal karyotype described as 46,XX. The fetus was evaluated for clinical features after delivery; she was healthy with no abnormal clinical characterizations.  相似文献   
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