墨兰花朵发育和衰老生理的初步研究

目的：了解墨兰花朵的发育和衰老生理,为控制黑兰花期提供科学依据。方法：测定不同发育期的墨兰花瓣的干重／鲜重、呼吸速率、过氧化物酶活性及可溶性糖含量。结果：黑兰花朵在由花蕾发育到衰老的过程中,上述指标呈现出一定的变化规律。     

Regulation of cell death in flower petals

The often rapid and synchronous programmed death of petal cells provides a model system to study molecular aspects of organ senescence. The death of petal cells is preceded by a loss of membrane permeability, due in part to increases in reactive oxygen species that are in turn related to up-regulation of oxidative enzymes and to a decrease in activity of certain protective enzymes. The senescence process also consists of a loss of proteins caused by activation of various proteinases, a loss of nucleic acids as nucleases are activated, and enzyme-mediated alterations of carbohydrate polymers. Many of the genes for these senescence-associated enzymes have been cloned. In some flowers, the degradative changes of petal cells are initiated by ethylene; in others, abscisic acid may play a role. External factors such as pollination, drought and temperature stress also affect senescence, perhaps by interacting with hormones normally produced by the flowers. Signal transduction may involve G-proteins, calcium activity changes and the regulation of protein phosphorylation and dephosphorylation. The efficacy of the floral system as well as the research tools now available make it likely that important information will soon be added to our knowledge of the molecular mechanisms involved in petal cell death.     

Determination of levetiracetam in human plasma with minimal sample pretreatment

We here present a method for the routine quantification of the novel antiepileptic drug levetiracetam in human serum by HPLC-UV. The procedure is very easy, quick, inexpensive and rugged. The sample preparation consists only in the precipitation of serum proteins by perchloric acid and extraction of unpolar components by cyclohexane. The aqueous phase containing the analyte levetiracetam is injected onto a porous graphitic carbon analytical HPLC-column and separated by gradient elution with diluted phosphoric acid/acetonitrile. Detection is carried out at a wavelength of 205 nm. The calibration function is linear in the range of 1-75 microg/ml. The detection limit is 0.1 microg/ml. Using four quality control sample concentrations, the inter-day relative standard deviations (R.S.D.) are lower than 3% and the accuracies are better than 6%. The respective inter-day values are: R.S.D. < 4% and accuracies better than 2%. Frequently co-administered antiepileptic drugs do not interfere with the assay. The method has been successfully applied to patient samples.     

Suppression of cell expansion by ectopic expression of the Arabidopsis SUPERMAN gene in transgenic petunia and tobacco

Molecular and genetic analyses have shown that the Arabidopsis thaliana gene SUPERMAN (SUP) has at least two functions in Arabidopsis flower development. SUP is necessary to control the correct distribution of cells with either a stamen or carpel fate, and is essential for proper outgrowth of the ovule outer integument. Both these functions indicate a role for SUP in cell proliferation. To study the function of the Arabidopsis SUP gene in more detail, we over-expressed the SUP gene in petunia and tobacco in a tissue-specific manner. The petunia FLORAL BINDING PROTEIN 1 (FBP1) gene promoter was used to restrict the expression of SUP to petals and stamens. The development of petals and stamens was severely affected in both petunia and tobacco plants over-expressing SUP. Petals remained small and did not unfold, resulting in closed flowers. Stamen filaments were thin and very short. Detailed analysis of these floral organs from the petunia transformants showed that cell expansion was dramatically reduced without affecting cell division. These results reveal a novel activity for SUP as a regulator of cell expansion.     

Spontaneous and enzymic rearrangement of naringenin chalcone to flavanone

The isomerisation of 2′,4,4′,6′-tetrahydroxychalcone by the enzyme chalcone isomerase is difficult to assay accurately in view of the spontaneous cyclisation of this chalcone at the alkaline pH optimum of the enzyme. We report here that self-cyclisation of naringenin chalcone is dramatically reduced at pH-values ? 6.5 and in the presence of high concentrations of serum albumin (5–10 mg ml ^?1). We have critically evaluated existing assay procedures of chalcone isomerase, utilizing the effects of a monospecific anti-(chalcone isomerase) serum to distinguish between spontaneous and enzymic cyclisation of chalcone. We conclude that the modifications listed above considerably facilitate the measurement of chalcone isomerase kinetics.     

莲瓣王捧瓣与舌瓣SSH文库构建及EST序列分析

为了探索兰花舌瓣形成的分子机制,本研究利用消减抑制杂交技术构建了莲瓣王（Cymbidium lianpan Tang et Wang）捧瓣与舌瓣间的cDNA文库。对正向文库中随机挑选的147个阳性克隆测序,组装、拼接,找到37个唯一序列,其中包含25个单一序列和12个拼接序列。经同源性比对,这些EST分别归类于蛋白质折叠,结合、未知功能、应激反应、光合作用、转录调控、信号传导、生物合成、新陈代谢、MADS等10类。通过对MADS-box基因的系统进化树分析,可初步推测MADS-Contig1和MADS-Contig2属于A类基因中的SQUA-like亚家族基因。     

Invertase inhibitor-control of sucrose transport from carnation petals to other flower parts

An investigation was made of the distribution of metabolites in the receptacles and ovaries, and the activity of an invertase inhibitor after feeding the petals with ¹⁴C-sucrose and cycloheximide during the natural aging of cut carnation flower. The cycloheximide treatment blocked the synthesis of the invertase inhibitor in petals and maintained a relatively high level of invertase activity during flower senscence. Treatment with cycloheximide decreased the movement of radioactivity from petals to receptacles and ovaries from 7 to 10 times, compared to non-treated control flowers. IAA applied on the stigma had no influence on synthesis of the inhibitor and distribution of the radioactivity.     

Invertase and sucrose synthase in flowers

Sucrose and reducing sugar concentrations in petals of cut carnation flowers, whose life was prolonged up to 7 days by bathing stalks in sucrose solutions, were respectively 3-fold and 2-fold higher than those bathed in water. Reducing sugar concentrations were about 7-fold higher than sucrose concentrations. A study of invertase and sucrose synthase activities in flower petals of carnation and four other species of flowers revealed that both enzymes may be involved in hydrolysis of translocated sucrose. Invertase activity, while being up to 20-fold higher than sucrose synthase activity in some species was approximately comparable in others. More detailed studies on invertase from petals of 3 flower species demonstrated the presence of only the acid form of the enzyme with a K_m value for sucrose of about 2.5 mM.     

Highly Efficient Oxygen Reduction Reaction Activity of Graphitic Tube Encapsulating Nitrided CoxFey Alloy

Nonprecious metals are promising catalysts to avoid the sluggish oxygen reduction reaction (ORR) in next‐generation regenerative fuel cells or metal–air batteries. Therefore, development of nonprecious metal catalysts for ORR is highly desirable. Herein, precise tuning of the atomic ratio of Fe and Co encapsulated in melamine‐derived nitrogen‐rich graphitic tube (NGT) is reported. The Co_1.08Fe_3.34 hybrid with metal? nitrogen bonds ( 1 : Co_1.08Fe_3.34@NGT) shows remarkable ORR catalytic activities (80 mV higher in onset potential and 50 mV higher in half‐wave potential than those of state‐of‐the‐art commercial Pt/C catalysts), high current density, and stability. In acidic solution, 1 also shows compatible performance to commercial Pt/C in terms of ORR activity, current density, stability, and methanol tolerance. The high ORR activity is ascribed to the co‐existence of Fe? N, Co? N, and sufficient metallic FeCo alloys which favor faster electron movement and better adsorption of oxygen molecules on the catalyst surface. In the alkaline anion exchange membrane fuel cell setup, this cell delivers the power density of 117 mW cm^?2, demonstrating its potential use for energy conversion and storage applications.