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131.
Hybrid females from crosses between Drsophila melanogaster males and females of its sibling species, D. simulans, D. mauritiana, or D. sechellia die as embryos. This lethality is believed to be caused by incompatibility between the X chromosome of D. melanogaster and the maternal cytoplasm. Zygotic hybrid rescue (Zhr) prevents this embryonic lethality and has been cytogenetically mapped to a proximal region of the X chromosome of D. melanogaster, probably in the centromeric heterochromatin. We have carried out high resolution cytological mapping of Zhr using deficiencies and duplications of the X heterochromatin. Deletions of the Zhr + gene from the hybrid genome exhibit the Zhr phenotype. On the contrary, addition of the wild-type gene to the hybrid genome causes embryonic lethality, regardless of sex. The Zhr locus has been narrowed down to the region covered by Dp(1;f)1162 but not covered Dp(1;f)1205, a chromosome carrying a duplication of heterochromatin located slightly distal to the In(1)sc 8 heterochromatic breakpoint.  相似文献   
132.
The interfering effects of copper, zinc, and cobalt on the uptake of mugineic acid-ferric complex were studied in barley ( Hordeum vulgare , cv. Minorimugi) grown in nutrient solution. Short-term uptake experiments of 3 h were performed utilizing both ionic and mugineic acid-complex forms of each metal at two different concentrations. Copper was most effective in decreasing iron uptake when added in an ionic form at either concentration. The inhibition order at higher concentrations followed Cu(II) > Zn(II) ≥ Co(II), Co(III), which is consistent with the stability constants of these metal complexes with mugineic acid. The displacement of iron from its mugineic acid complex by these metals is suggested as a probable explanation for the decreased iron uptake. The inhibitory effect of metal complexes with mugineic acid on iron uptake was only found in cases with higher concentrations of Cu(II) and Zn(II) complexes. Deformation of the specific iron transport system in the plasma membrane due to their adsorption may be responsible for this effect.  相似文献   
133.
Photosystem II (PS II) particles isolated from spinach in the presence of 10 M CuSO4 contained 1.2 copper/300 Chl that was resistant to EDTA. When CuSO4 was not added during the isolation, PS II particles contained variable amounts of copper resistant to EDTA (0.1–1.1 copper/300 Chl). No correlation was found between copper content and oxygen evolving capacity of the PS II particles. To identify the copper binding protein, we developed a fractionation procedure which included solubilisation of PS II particles followed by precipitation with polyethylene glycol. A 22-fold purification of copper with respect to protein was achieved for a 28 kDa protein. Partial amino acid sequence of a 13 kDa fragment, obtained after V8 (endo Glu-C) protease treatment, showed identity with CP 26 over a 14 amino acid stretch. EPR measurements on the purified protein suggest oxygen and/or nitrogen as ligands for copper but tend to exclude sulfur. We conclude that the 28 kDa apoprotein of CP 26 from spinach binds one copper per molecule of CP 26. A possible function for this copper protein in the xanthophyll cycle is discussed.Abbreviations CP 26 and CP 29 chlorophyll a/b protein complex 26 and 29 - LHC II light-harvesting chlorophyll a/b protein complex of Photosystem II - SB14 sulfobetaine 14 A preliminary report of these results was presented at the IX Int. Congress on Photosynthesis, Nagoya, Japan, 1992.  相似文献   
134.
Wheat leaves were exposed to light treatments that excite preferentially Photosystem I (PS I) or Photosystem II (PS II) and induce State 1 or State 2, respectively. Simultaneous measurements of CO2 assimilation, chlorophyll fluorescence and absorbance at 820 nm were used to estimate the quantum efficiencies of CO2 assimilation and PS II and PS I photochemistry during State transitions. State transitions were found to be associated with changes in the efficiency with which an absorbed photon is transferred to an open PS II reaction centre, but did not correlate with changes in the quantum efficiencies of PS II photochemistry or CO2 assimilation. Studies of the phosphorylation status of the light harvesting chlorophyll protein complex associated with PS II (LHC II) in wheat leaves and using chlorina mutants of barley which are deficient in this complex demonstrate that the changes in the effective antennae size of Photosystem II occurring during State transitions require LHC II and correlate with the phosphorylation status of LHC II. However, such correlations were not found in maize leaves. It is concluded that State transitions in C3 leaves are associated with phosphorylation-induced modifications of the PS II antennae, but these changes do not serve to optimise the use of light absorbed by the leaf for CO2 assimilation.Abbreviations Fm, Fo, Fv maximal, minimal and variable fluorescence yields - Fm, Fv maximal and variable fluorescence yields in a light adapted state - LHC II light harvesting chlorophyll a/b protein complex associated with PS II - qP photochemical quenching - A820 light-induced absorbance change at 820 nm - PS I, PS II relative quantum efficiencies of PS I and PS II photochemistry - CO 2 quantum yield of CO2 assimilation  相似文献   
135.
Our recent EPR and EXAFS experiments investigating the structure of the oxygen-evolving complex of PS II are discussed. PS II treatments which affect the cofactors calcium and chloride have been used to poise samples in modified forms of the S-states, S1, S2 and S3. X-ray absorption studies indicate a similar overall structure for the manganese complex between treated and native samples although the influence of the treatments and cofactors is observed. Manganese oxidation (or oxidation of a ligand to the manganese cluster) is indicated to occur on each of the transitions S1 S2 and S2 S3 in these modified samples. The cluster appears to contain at least two inequivalent Mn-Mn pairs. In the native samples the Mn-Mn distance is 2.7 Å, but in samples where the calcium site is affected, one of the pairs has a 3.0 Å Mn-Mn distance. The intensity of the 3.3/3.6 Å interaction is reduced on sodium chloride treatment (calcium depletion) perhaps indicating calcium binding close to the manganese cluster. From EPR data we also propose that treatments which affect calcium and chloride binding cause a modification of the native S2 state, slow the reduction of Yz and allow an S3 EPR signal to be observed following illumination. The origin of the S3 EPR signal, a modified S3 or S2 X where X is an organic radical of unknown charge, is discussed in relation to the results from the EXAFS studies.Abbreviations EPR electron paramagnetic resonance spectroscopy - EXAFS extended X-ray absorption fine structure - HTG n-heptyl -d-thioglucoside - MES 2(N-morpholino)ethanesulfonic acid - OEC oxygen evolving complex - PPBQ phenyl-1,4-benzoquinone - PS II Photosystem II - Yz redox active tyrosine  相似文献   
136.
DTT(二流苏糖醇)可解除TPT(氯化三苯锡)对叶绿体光合磷酸化的抑制、减弱TPT对类囊体跨膜△pH的抑制和对类囊体腔内质子外流的促进。由于TPT较专一作用于CF0,推测CF0受DTT修饰。这从DTT可消除TPT对去除CF1的类囊体残缺膜△pH的重建和对残缺膜光下收缩的促进得到进一步的证明。DTT的作用是还原二硫键成为游离的巯基,因而CF0可能含有二硫键。从光下DTT或暗中DTT处理残缺膜对TPT作用的影响,可以看到DTT对CF0的修饰是需光的,类囊体膜在光下发生的构象变化,使CF0的二硫键暴露而被DTT修饰。CF0的二硫键较CF1γ的二硫键更快、更敏感地被DTT所修饰。  相似文献   
137.
中国龙葵复合种细胞学分析和地理分布的研究   总被引:9,自引:1,他引:8  
杨永年  张海洋 《植物研究》1994,14(2):208-213
本文根据15省30余个县的实地考察,和对采自25省的66份中国龙葵种籽进行种植观察,并与国外的有关研究资料对比分析,在国内首次提出;(1)中国龙葵复合种的四个种,从低纬度到高纬度(18.6-53.5°N),分别属于二倍体,四倍体和六倍体种;(2)从中国南方到北方,自然形成了二倍体,六倍体与二倍体交叉,六倍体与四倍体交叉三个地理分布区。  相似文献   
138.
醋酸钙复盐对微生物生长的影响   总被引:1,自引:0,他引:1  
应用四醋酸钙对黑曲霉、黄曲霉、米曲霉、链格孢霉等霉菌和大肠杆菌、枯草杆菌、绿脓杆菌、金黄色葡萄球菌等细菌生长影响作了研究,并将四醋酸钙与醋酸钙、苯甲酸钠对上述微生物的生长抑制作用加以比较。0.4%四醋酸钙对上述细菌的生长有明显的抑制作用。对上述霉菌生长亦有一定的抑制作用。当其与苯甲酸钠协同使用时,能更明显地抑制微生物生长。实验结果表明四醋酸钙很可能是一种安全性高、成本低的新型食品防腐剂。  相似文献   
139.
细胞色素P450(P450,Ec1.14.14.1)是一种十分重要的催化氧化反应的酶。本文测定了12个对氨基苯甲酸酯同系物与P450相互作用而形成P450代谢中间体络合物的活性,用半经验分子轨道法MNDO-PM3计算得到了这些同系物的分子轨道指数,并用逐步多元回归分析法导出了活性与分子轨道指数及正辛醇/水分配系数的对数值(LogP)之间的定量结构与活性关系(QSAR)。结果表明:对氨基苯甲酸脂同系物形成P450代谢中间体络合物的活性与原子净电荷的绝对值之和(∑Q)和LogP均具有很好的抛物线型相务性,同时,LogP与∑Q之间也存在相当好的相关性。  相似文献   
140.
Summary During a search for novel coding sequences within the human MHC class I region (chromosome 6p21.3), we found an exon (named B30-2) coding for a 166-amino-acid peptide which is very similar to the C-terminal domain of several coding sequences: human 52-kD Sjögren's syndrome nuclear antigen A/Ro (SS-A/Ro) and ret finger protein (RFP), Xenopus nuclear factor 7 (XNF7), and bovine butyrophilin. The first three of these proteins share similarities over the whole length of the molecule whereas butyrophilin is similar in the C-terminal domain. The N-terminal domain of butyrophilin is similar to rat myelin/oligodendrocyte glycoprotein (MOG) and chicken B blood group system (B-G) protein. These domains are components of a new subfamily of the immunoglobulin superfamily (IgSF). Butyrophilin is thus a mosaic protein composed of the MOG/B-G Ig-like domain and the C-terminal domain of 52-kD SS-A/Ro, RFP, and XNF7 (1330-2-like domain). Moreover, in situ hybridization shows that RFP, butyrophilin, and MOG map to the human chromosome 6p2l.3-6p22 region and are thus close to the MHC class I genes. It is therefore possible that the butyrophilin gene is the product of an exon shuffling event which occurred between ancestors of the RFP and MOG genes. To our knowledge, this is the first example of the colocalization of a chimeric gene and its putative progenitors. Finally, regulatory protein T-lymphocyte 1 (Rpt-1) shares similarities with the N-terminal halves of RFP, 52-kD SS-A/Ro, and XNF7, but not with the B30-2-like domain. We show that the ancestral Rpt-l gene evolved by overprinting. Correspondence to: P. Pontarotti  相似文献   
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