共查询到20条相似文献，搜索用时 15 毫秒
1.
Picosecond time-resolved resonance Raman studies of hemoglobin: implications for reactivity 总被引：2，自引：0，他引：2
Picosecond time-resolved Raman spectra of hemoglobin generated with blue pulses (20 to 30 picoseconds) that were resonant with the Soret band and of sufficient intensity to completely photodissociate the starting liganded sample are reported. For both R- and T-state liganded hemoglobins, the peak frequencies in the spectrum of the deoxy transient were the same at approximately 25 picoseconds as those observed at 10 nanoseconds subsequent to photodissociation. In particular, the large R-T differences in the frequency of the stretching mode for the iron-proximal histidine bond (VFe-His) detected in previously reported nanosecond-resolved spectra were also evident in the picosecond-resolved spectra. The implications of this finding with respect to the distribution of strain energy in the liganded protein and the origin of the time course for geminate recombination are discussed. On the basis of these results, a microscopic model is proposed in which delocalization of strain energy is strongly coupled to the coordinate of the iron. The model is used to explain the origin of the R-T differences in the rates of ligand dissociation. 相似文献
2.
Structure, dynamics, and reactivity in hemoglobin 总被引：10，自引：0，他引：10
J M Friedman 《Science (New York, N.Y.)》1985,228(4705):1273-1280
The static structure of hemoglobin and its functional properties are very well characterized. It is still not known how energy is stored and used within the structure of the protein to promote function and functional diversity. An essential part of this question is understanding the mechanism through which the overall protein structure (quaternary structure) couples to the local environment about the oxygen binding sites. Time-resolved resonance Raman spectroscopy has been used to probe the vibrational degrees of the freedom of the binding site as a function of protein structure. Comparison of the spectra from both equilibrium and transient forms of deoxy hemoglobin from a variety of mammalian, reptilian, and fish hemoglobins reveals that for each quaternary structure there exist two tertiary states stabilized by the presence or absence of an iron-bound ligand. Pulse-probe Raman experiments show that for photodissociated, ligated hemoglobins the local tertiary structure relaxes at a solution-dependent rate extending from tens of nanoseconds to microseconds. In this local environment, the linkage between the iron and the proximal histidine proves to be the single observed structural feature that responds in a systematic and substantial manner to structural changes in the protein. The additional finding of a correlation between the frequency of the iron-proximal histidine stretching motion (nu Fe-His) and various parameters of ligand reactivity, including geminate recombination, implicates the associated localized structural element in the mechanism of protein control of ligand binding. On the basis of these and related finds, a model is presented to account for both coarse and fine control of ligand binding by the protein structure. 相似文献
3.
Starch gel electrophoretic patterns of hemoglobins from fetal mice of seven inbred strains (two with single, five with diffuse adult hemoglobins), were compared with each other and with electrophoretic patterns of hemoglobins from adults of the same strains. The blood from 15-day-old fetuses of all strains contained four electrophoretically separable heme components. However, there seems to be a difference between strains with single and diffuse adult hemoglobin in the time of emergence of a clear adult pattern. 相似文献
4.
After administration of glycine-2-(14)C to a patient with thalassemia, the specific activities of heme and globin of F hemoglobin were consistently higher than those of hemoglobin A. After reaching a maximum, the ratio of the specific activity of heme to that of globin remained constant within each hemoglobin. Explanations considered include dilution by preformed subunits, differential turnover of hemoglobins, and possibly more than one heme-synthesizing pool. 相似文献
5.
Influence of preceding crop and tillage system on forage yield and quality of selected summer grass and legume forage crops under arid conditions 
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下载免费PDF全文 Hend H. M. HASSAN El-Sayed E. A. EL-SOBKY Elsayed MANSOUR Ahmed S. M. El-KHOLY Mohamed F. AWAD Hayat ULLAH Avishek DATTA 《农业科学学报》2022,21(11):3329-3344
Among the crop production factors, preceding crop and tillage management affect the sustainable use of soil resources and ultimately crop growth and productivity. This study aimed at investigating the impact of preceding winter crops (grass or legume) and different tillage systems on forage yield, quality and nutritive values of three summer grass (Sudan grass, pearl millet and teosinte) and two legume forage crops (cowpea and guar) under arid conditions. The results exhibited that growing forage crops after legumes (as berseem clover) produced the highest fresh and dry forage yields and quality attributes compared with grasses (as wheat) with the exception of crude fiber content, which was decreased. Moreover, tillage practices showed positive impact on forage yields and quality attributes. The maximum forage yields and quality parameters were recorded under conventional tillage (CT) practice compared with reduced tillage (RT) and no-tillage (NT) systems. Among the evaluated crops, the highest yields of fresh forage, dry forage, crude fiber, crude protein and total digestible nutrient were exhibited by grass forage crops (Sudan grass, pearl millet and teosinte), whereas the highest crude protein content and the digestible energy values were produced by legume forage crops (cowpea and guar). The maximum fresh forage, dry forage, crude fiber, crude protein, total digestible nutrient and digestible crude protein yields were produced by pearl millet followed by Sudan grass under CT and RT after berseem clover. The highest net return was recorded by sowing pearl millet after berseem clover and applying CT followed by RT practices, which could be recommended for the commercial production. Moreover, it could be assumed that the combination of growing grass forage crops after legume crops under CT or RT systems could enhance forage crop yield and quality with an improvement in soil properties for sustainable agriculture with low cost and the highest net income. 相似文献
6.
C Manwell 《Science (New York, N.Y.)》1966,152(727):1393-1396
The hemoglobin of the "thin" sibling species of Thyonella gemmata (phylum: Echinodermata; class: Holothuria) has three electrophoretically distinct polypeptide chains. In "stout" sibling species of T. gemmata there are only two chain types. These results account for the greater number of multiple hemoglobins in "thins" than in "stouts," as well as for differences in the amounts of some of the multiple hemoglobins when comparisons are mnade of hemolyzates of erythrocytes from the water vascular systemn and from the main body cavity of the "thin" but not the "stout" sibling species. 相似文献
7.
Paper electrophoregrams of the hemoglobins from 14 species of fresh- and salt-water fish demonstrated from one to three components. The relative distribution of these fractions was determined for all species. Mobilities of the three hemoglobins of rainbow trout were calculated from moving-boundary patterns. Low anodal mobility at pH 8.8 was characteristic of many species examined. 相似文献
8.
中国红豆杉紫杉烷10β-羟化酶的分子克隆及在酿酒酵母中的表达 总被引：2，自引：0，他引：2
天然产物紫杉醇是一种重要的抗癌药。其天然来源的匮乏和缺少商业上可行的化学全合成促进了对紫杉醇生物来源的深入研究。紫杉醇的生物合成是一个复杂的多步过程,主要包括四环骨架的构建和加入各种羟基和酰基基团,其中羟基的加入由细胞色素P450氧化酶催化。我们从中国红豆杉愈伤组织细胞mRNA构建的cDNA文库中克隆得到几个P450 cDNA片段。其中一个长1494bp的cDNA片段,编码497个氨基酸,推断蛋白分子量为56470 Da,等电点为9．42。序列比较显示,这个推断蛋白包含多个细胞色素P450氧化酶的保守区,具有典型的细胞色素P450氧化酶的特征,进一步的比较发现其与已鉴定的东北红豆杉紫杉烷-10β-羟化酶有92％的同源性。将这个cDNA片段连接在质粒pYeDP60上构建表达载体,导入相应的酵母表达菌株WHT和WVS进行表达,获得相应大小的蛋白表达条带,功能鉴定的工作正在进行中。 相似文献
9.
芦竹Arundo donax L.由于其生长快速、抗逆性强、蛋白含量高等优点,正以重要能源植物的定位受到越来越多的重视。本研究针对本单位收集的源自我国山东省烟台市及福建省福州市永泰县的2种芦竹进行叶片形态、生物量及营养物质含量等生物学特性分析,发现2个芦竹品种在干物质产量、水分含量、纤维含量、粗灰分含量等指标上存在一定差异性。基于上述差异性,对2个芦竹品种的叶片进行Illumina高通量测序分析,构建芦竹转录组数据库。通过de novo的方法对获得的转录组数据进行组装,并预测各组装获得Unigene的开放阅读框,从而获得可能的蛋白氨基酸序列。通过基因表达量差异性分析,筛选2个芦竹品种中表达量差异显著的基因,并将上述基因与Gene Ontology(GO)、Eukaryotic Orthologous Groups of proteins(KOG)及Kyoto Encyclopedia of Genes and Genomes(KEGG)等数据库比对分析,预测差异表达基因的功能及参与的代谢信号通道。针对与生物量及生物乙醇产量相关的代谢途径的分析发现,2个芦竹品种在碳固定光合作用、淀粉/糖代谢及木质素合成相关的信号通道中关键酶基因的表达量上具有显著差异。上述结论从生物学及生物信息学角度分别分析了源自我国不同地域的芦竹品种在生物产量及生物质能源相关指标上的差异性。研究结论为筛选芦竹品种作为优质生物质能源草种提供了依据。 相似文献
10.
Anuran metamorphosis is accompanied by changes in the sedimentation patterns of the lysates of red blood cells of several species. Rana grylio and Rana catesbeiana tadpoles have hemoglobins that sediment at 4.3S (molecular weight, 68,000) and gradually produce a heavier 7.0S component (estimated molecular weight, 136,000) during metamorphosis to the adult frog. There is extensive change in the amino acid compositions of these hemoglobins; these changes may account for observed changes in electrophoretic mobility. 相似文献
11.
春季肥水运筹对冬小麦籽粒产量和品质的影响 总被引：28，自引：2，他引：28
本文探讨了春季灌水次数和追氮量对冬小麦冀麦２４号和冀麦２３号的籽粒产量、籽粒蛋白质含量和蛋白质产量的影响。两品种的籽粒产量和蛋白质产量以及冀麦２３号的籽粒蛋白质含量，均以春季浇４水为最高，冀麦２４号的籽粒蛋白质含量则以春季浇３水最高。追氮量对３项指标均有显著影响，各指标均随春季追氮量增加而提高。在春季灌３～６水范围内，每公顷追纯Ｎ２４０ｋｇ或１８０ｋｇ时３项指标达最高值，仅是浇３水时略有例外。籽粒产量、籽粒蛋白质含量和蛋白质产量之间均是显著正相关。 相似文献
12.
鼎湖山季风常绿阔叶林各层次优势种热值研究 总被引：16，自引：0，他引：16
探讨鼎湖山南亚热带季风常绿阔叶林不同层次优势植物热值一般规律,可为该群落能量特征和生态效率研究提供基础资料和科学依据. 2002年用PARR 1281型氧弹热值仪测定了该群落不同层次21种优势植物不同器官(部位)热值. 结果表明, 季风常绿阔叶林各优势种的平均干重热值在15.92～19.66 kJ/g间,乔木1层干重热值以厚壳桂最高, 乌榄最低; 乔木2层华润楠最高, 云南银柴最低; 层间藤本植物白背瓜馥木和杖枝省藤分别为19.73和18.19 kJ/g; 灌木层干重热值最高仍为厚壳桂, 最低为云南银柴; 草本层植物干重热值在15.92～17.52 kJ/g之间. 各层优势种平均干重热值和去灰分热值都表现为: 层间藤本＞乔木1层＞乔木2层＞灌木层＞草本层. 植物器官去灰分热值存在差异, 乔木1层中锥栗、荷木树皮及厚壳桂、乌榄树叶最高, 乔木2层中云南银柴根最高, 层间植物叶＞干＞根, 草本植物是地上部分＞地下部分; 同种植物(厚壳桂或云南银柴)在不同层次中的去灰分热值没有明显差别, 器官生长的年龄(或直径)对去灰分热值有影响, 随年龄增大, 去灰分热值有减少趋势. 相似文献
13.
R Q Blackwell B N Blackwell J T Huang L C Chien A Samaharn C Thephusdin C Borvornsin 《Science (New York, N.Y.)》1965,150(703):1614-1615
Hemoglobin J(Korat), a "fast" hemoglobin with an anomaly in its beta chain different from the anomalies previously reported, was the major hemoglobin component in the blood of nine subjects among 1923 Thais from northeastern Thailand. After hemoglobin E, J(Korat) is the second most frequent of the anomalous hemoglobins among Thais. 相似文献
14.
颤藻目蓝藻是世界广泛分布的藻类,也是正处于藻类分类学修订中的一大类群.根据形态特征,在2014年夏季上海黄浦江水体采集的藻类样品中,确定了中国蓝藻的一个新纪录属——盖丝藻属(Geitlerinema)和新纪录种——群动盖丝藻(Geitlerinema ionicum),对该属和该种的分类学形态特征进行了详细的描述;另外,参考KOMAREK和ANAGNOSTIDIS分类体系,对我国与该属相关的蓝藻种类进行了重新归类组合,发现尖头颤藻(Osicllatoria acutissima)、两栖颤藻(O.amphibia)、双点颤藻硫泉变种(O.geminate var.sulphurea)、四点颤藻单颗粒变种(O.quadripunctulata var.unigranulata)等4种应归入盖丝藻属. 相似文献
15.
Linkage of functional and structural heterogeneity in proteins: dynamic hole burning in carboxymyoglobin 总被引：10，自引：0，他引：10
Inhomogeneous broadening of the 760-nanometer photoproduct band of carboxymyoglobin at cryogenic temperatures has been demonstrated with a dynamic hole burning technique. Line-shape changes and frequency shifts in this spectral band are generated by ligand recombination and are shown not to be the result of structural relaxation below 60 K. The observation of dynamic hole burning exposes the relation between the structural disorder responsible for the inhomogeneous broadening and the well-known distributed ligand rebinding kinetics. The findings provide direct evidence for the functional relevance of conformational substrates in myoglobin rebinding. In addition, a general protocol for evaluating the relative contributions of structural relaxation and hole burning to the spectral changes accompanying rebinding in hemeproteins is presented. 相似文献
16.
对9个青藏高原植被区的仲彬草属(StYP基因组组成)植物及2个拟鹅观草属(St基因组)物种和2个冰草属(P基因组)植物共13个类群的叶绿体rbcL序列进行遗传和基因谱系分析,探讨青藏高原仲彬草属植物的系统关系及其物种形成的母本供体来源。结果表明:①Kengyilia stenachyra、Kengyilia kokonorica、Kengyilia hirsuta、Kengyilia rigidula和Kengyilia grandiglumis的种间关系较近;②Kengyilia stenachyra和Kengyilia geminata在rbcL序列上发生了一定程度的分化;③拟鹅观草属和冰草属植物均可能作为母本供体参与青藏高原植被区不同仲彬草属植物的物种形成。 相似文献
17.
对葡萄血红蛋白基因的结构、进化关系、序列特征及蛋白结构进行剖析。基因结构和蛋白序列特征分析表明:尽管葡萄3个血红蛋白基因外显子个数和保守基序组织结构变异较大,但功能结构域具有高度保守性。结构模拟显示,葡萄VvHb1以单体形式存在,而VvHb2和VvHb3则以二聚体形式存在,尽管它们三维构象以螺旋结构为主,但结合血红素分子活性不同。进化分析揭示,植物血红蛋白具有4个类群,其中葡萄的血红蛋白落入主要类群外,并且单独形成了一个进化分支,说明葡萄血红蛋白基因在物种形成后发生了快速进化和基因扩增现象。 相似文献
18.
颤藻目蓝藻是世界广泛分布的藻类,也是正处于藻类分类学修订中的一大类群。本文在2014年夏季上海黄浦江水体采集的藻类样品中,根据形态特征鉴定分析,确定了中国蓝藻的一个新纪录属——盖丝藻属(Geitlerinema)和新纪录种——群动盖丝藻(Geitlerinema ionicum),本文对该属和该种的分类学的形态特征进行了详细的描述;另外,本文参考Komárek 和Anagnostidis(2005)分类体系,对我国与该属相关的蓝藻种类进行了重新归类组合,发现尖头颤藻(Osicllatoria acutissima)、两栖颤藻(O. amphibia)、双点颤藻硫泉变种(O. geminate var. sulphurea)、四点颤藻单颗粒变种(O. quadripunctulata var. unigranulata)等4种应归入盖丝藻属。 相似文献
19.
Multiplicity of hemoglobins in the genus Chironomus (Tendipes) 总被引：2，自引：0，他引：2
The number of hemoglobins found in individual mature larvae of several Chironomus species is six to nine. The consistency of this number and of the electrophoretic mobilities of these separable forms seems to indicate the synchronous production of polypeptide chains by several genetic loci. 相似文献