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231.
The structure of the predicted amino acid sequence in the FX domain of Photosystem 1 was studied by molecular modeling and a working hypothesis was developed for the functional interaction of PsaC with the core heterodimer. We propose that the intervening sequences between homologous cysteines in the FX cluster form two flexible loops and participate in the binding of PsaC, and that the arginine residues in the two surface-exposed loops may promote the interaction between the P700–FX core and the subunit. The model was tested experimentally; chemical modification of arginine residues in the P700–FX core using phenylglyoxal prevented reconstitution of the core with PsaC and PsaD after insertion of FeS clusters in vitro. Treatment of the P700–FX core with trypsin also prevented reconstitution of terminal electron transfer to FAFB, although neither treatments affected the electron transfer to FX as judged by flash kinetic spectrophotometry. Electron transfer in the P700–FAFB complex was not impaired by either phenylglyoxal or trypsin treatment indicating that the small subunit(s) protect the arginine residues that become chemically modified or cleaved. The data are consistent with the working model and point to additional experiments designed to identify the specific residues involved in the interaction between the P700–FX core and PsaC.Abbreviations PG-
phenylglyoxal
- PS 1-
Photosystem 1 相似文献
232.
Somatic embryos and embryogenic callus were initiated from immature zygotic embryos of ginseng (Panax ginseng C.A. Meyer). These somatic embryos were multiplied by adventitious (secondary and tertiary) embryogenesis and their growth and development were dependent on growth hormones in the medium. Auxins, 2,4-d, NAA, and IAA at 1.0 mg l-1 were effective in inducing secondary and tertiary somatic embryos, which proliferated directly from the apical or cotyledonary portions of the primary somatic embryos. Single somatic embryos or clusters or embryos developed from the explanted primary embryos. Cytokinin (Kn, BA) inhibited adventitious embryogenesis. Secondary somatic embryos developed to maturation and later regenerated into plantlets in two stage process; firstly elongation of the shoot axes on MS +1.0 mg l-1 Kn, secondly formation of root on 1.0 mg l-1 Kn+1.0 mg-1 GA3 medium.Abbreviations 2,4-d
2,4-dichlorophenoxyacetic acid
- NAA
naphthaleneacetic acid
- IAA
in-doleacetic acid
- Kn
kinetin
- BA
benzylaminopurine
- PSE
primary somatic embryo
- SSE
secondary somatic embryo
- TSE
tertiary somatic embryo 相似文献
233.
Maria Giovanna Riparbelli Romano Dallai Giuliano Callaini 《Biology of the cell / under the auspices of the European Cell Biology Organization》1993,78(3):223-227
Rhodamine phalloidin-staining was used to study the organization of the cortical actin cytoskeleton of the early Ceratitis capitata embryo. The dynamics of the actin aggregates and their changes in distribution during the formation of the syncytial blastoderm, were followed in detail. It was found that these aggregates formed a shell-like cluster around the interphase nuclei, and concentrated toward the poles of the mitotic apparatus when the nuclei divided. Laser scanning confocal microscopy revealed that aggregates not clustered at the poles of the mitotic apparatus were closely associated with fine fibers of a dense cytoplasmic network of actin filaments. 相似文献
234.
LAURE LECOIN PASCALE MERCIER NICOLE M. LE DOUARIN 《Pigment cell & melanoma research》1994,7(4):210-216
In the Silky Fowl (SF) breed of chicken, most of the internal organs are infiltrated with melanocytes. Previous studies have shown that this generalized mesodermal pigmentation is not due to a cell autonomous abnormality of the melanocytes but to environmental factors able to promote both the homing of pigment cell precursors in abnormal embryonic sites and their proliferation and differentiation. To analyse the mode of these environmental cues, we tested the effect of SF embryo extract (SFEE) on cultured quail neural crest cells as compared with that of EE from normal chickens of the JA57 strain (JA57EE). We found that SFEE enhances crest cell proliferation as judged by 3H-TdR incorporation and cell counting. In contrast, no effect of SFEE was observed either on the proportion of cultured cells that are engaged into the melanocytic differentiation pathway or on the amount of melanin produced by each differentiated pigment cell. The simple observation, however, reveals that SFEE has a significant effect on pigmentation of the cultured quail neural crest cells. This effect has therefore to be accounted for by the general increase in cell number induced by SFEE. The question is raised as to whether the in vivo SF phenotype is generated exclusively by this mechanism. 相似文献
235.
利用离体诱变技术选育小麦大粒种质的研究 总被引:3,自引:0,他引:3
以鲁麦12等为材料进行幼层培养,转分化前辐照1000rad,在R2代调查千粒重变异情况,结果表明,后代千粒重发生了显著变化,变异范围为39.5—68.5g.突变率高达63.08%,最高千粒重超过对照40.95%。已选出一批大粒材料应用于生产.其中核生二号新品种千粒重65g,杂交后代表明,大粒变异多为显性突变。 相似文献
236.
接合转移诱动系统在遗传分析和体内基因操作中的应用赵巍,张成刚,蔺继尚(中国科学院沈阳应用生态研究所,110015)细菌间DNA的转移主要有转化、转导、接合和原生质体融合等几种形式。接合是通过供体菌和受体菌完整细胞间的直接接触,而传递大段DNA的方法,... 相似文献
237.
本文研究了超声波和相转移催化剂在Reimer—Tiemann反应中的应用,提出了超声波和相转移催化下Reimer—Tiemann反应的机理。研究结果表明:在超声波和相转移催化剂的共同作用下,二氯卡宾形成十分迅速,羟基苯甲醛产率显著提高,反应时间成倍缩短。 相似文献
238.
T. E. Tautorus M. M. Lulsdorf S. I. Kikcio D. I. Dunstan 《In vitro cellular & developmental biology. Plant》1994,30(1):58-63
Summary Embryogenic cell cultures ofPicea mariana (black spruce) and the species complexPicea glauca-engelmannii (interior spruce) were maintained either as suspensions in liquid medium in 250 or 500-ml-capacity shake-flasks, 7-liter-capacity
airlift or mechanically stirred bioreactors, or on agar-solidified medium. Cultures from each of the maintenance conditions
were subsequently transferred to agar-solidified LP medium containing 40μM (±) -abscisic acid for maturation into cotyledonary stage embryos. For both species, the highest maturation frequency resulted
from cultures grown in the airlift bioreactor. With black spruce cells grown in the airlift bioreactor containing LP medium
with 60 mM sucrose, a maximum of 7.1 g·liter−1 dry weight and 2892 embryos·ml−1 were obtained after 15 days. For interior spruce cells, a maximum dry weight of 5.9 g·liter−1 and 2698 embryos·ml−1 were obtained after 21 to 30 days. During culture over 2 wk, ammonia was almost completely utilized by both species, wherease
nitrate was depleted to 40% of the initial concentration. Sucrose was rapidly hydrolyzed to glucose and fructose by both species.
Black spruce cultures preferentially metabolized glucose, whereas interior spruce preferentially metabolized fructose. Improved
growth of interior spruce cells in mechanically stirred bioreactors occurred when cultured in LP medium with 60 mM fructose as the sole carbon source.
NRCC no. 36479 相似文献
239.
Summary Somatic embryos could be induced from the cotyledons of zygotic embryos from immature fruits ofFeijoa sellowiana Berg (Feijoa) in the presence of a wide range of concentrations of fructose, glucose, maltose, and sucrose. Mannitol or sorbitol
alone were ineffective. The highest frequencies of induction (99%) and the greatest number of somatic embryos per explant
(134) were obtained with 0.4M fructose and 0.3M sucrose, respectively. This sucrose concentration also showed greater induction capacity than equimolar combinations of its
monosaccharide constituents combined. Somatic embryo development was arrested at the globular stage at concentrations higher
than 0.5M of all the sugars tested. When transferred to solid germination medium containing 2.0 mg/liter (5.77μM) gibberellic acid, 0.5 mg/liter (2.32μM) kinetin, and 0.029M sucrose, somatic embryos formed under 0.3 or 0.4M sucrose had better germination capacity than those induced under lower (0.1 and 0.2M) concentrations, as assessed by the frequency of explants presenting germinated embryos and by the number of plants obtained
from those explants. On liquid media of similar composition somatic embryos did not germinate. Our data suggest that high
(0.3 to 0.4M) carbohydrate levels improve somatic embryogenesis by acting both as carbon source and as osmotic regulator. 相似文献
240.
A novel membrane bioreactor for detoxifying industrial wastewater: I. Biodegradation of phenol in a synthetically concocted wastewater 总被引:5,自引:0,他引:5
Livingston AG 《Biotechnology and bioengineering》1993,41(10):915-926
A novel process has been used to biodegrade phenol present in an acidic (1 M HCI) and salty (5% w/w NaCl) synthetically bioreactor, in which the phenol present in the wastewater is separated from the inorganic components by means of a silicone rubber membrane. Transfer of the phenol from the wastewater and into a biological growth medium allows biodegradation to proceed under controlled conditions which are unaffected by the hostile inorganic composition of the wastewater. At a wastewater flow rate of 18 mL h(-1) (contact time 6 h), 98.5% of the phenol present in the wastewater at an inlet concentration of 1000 mg ( (-1) ) was degraded; at a contact time of 1.9 h, 65% of the phenol was degraded. Phenol degradation was accompanied by growth of a biofilm on the membrane tubes and by conversion of approximately 80% of the carbon entering the system to CO(2) carbon. Analysis of the transport of phenol across the membrane revealed that the major resistance to mass transfer arose in the diffusion of phenol across the silicone rubber membrane. A mathematical model was used to describe the transfer of phenol across the membrane and the subsequent diffusion and reaction of phenol in the biofilm attached to the membrane tube. This analysis showed that (a) the attached biofilm significantly lowers the mass transfer driving force for phenol across the membrane, and (b) oxygen concentration limits the phenol degradation rate in the biofilm. These conclusions from the model are consistent with the experimental results. (c) 1993 Wiley & Sons, Inc. 相似文献