YidC/Oxa/Alb3超家族蛋白的起源演化研究

YidC/Oxa/Alb3超家族蛋白是重要的蛋白转运酶，分别负责将一些能量合成相关的蛋白质转运到细菌内膜、线粒体内膜和叶绿体类囊体膜。因为线粒体和叶绿体起源于内共生的细菌，所以真核细胞线粒体的Oxa和叶绿体的Alb3很容易像许多其它线粒体/叶绿体蛋白质一样被认为是起源于内共生细菌的同源物YidC。事实是否如此？我们基于已有的基因组数据库，对整个生物界中的众多古菌、真细菌和真核生物中YidC/Oxa/Alb3超家族的分布和分子系统发育关系进行了较全面、系统的调查分析，获得了如下主要结果： 1）YidC在古细菌中有所发现，但只零星分布于一些广古菌（Euryarchaeota）中；2）绝大多数真细菌只有一个YidC基因，但一些革兰氏阳性菌（芽胞杆菌、乳酸杆菌、放线菌和梭菌中的一些物种）已分化出两个YidC基因；3) 分子系统分析显示：线粒体Oxa、叶绿体Alb3和古菌YidC组成了3个独立的进化分枝，线粒体Oxa并未与蛋白菌序列聚在一起，叶绿体Alb3也未显示出与蓝细菌YidC有更近的亲缘关系；4）真菌、后生动物、绿藻和植物均具有两个Oxa（Oxa1和Oxa2）基因，这些真核生物的Oxa序列聚在两个独立的分开的进化枝上(Oxa1和Oxa2)；绿藻和植物中普遍具有两个Alb3基因。绿藻类生物的Alb3分布在两个独立的进化枝上，标记为Alb3.1和Alb3.2。植物Alb3序列也分布在两个不同的进化枝（Alb3.a和Alb3.b）上，并且它们一起和绿藻Alb3.1进化枝距离最近；结构域分析显示绿藻和植物中的Oxa2具有一个额外的C端TPR结构域；一些原生生物中Oxa和Alb3同源物的数目和在进化树上的聚类情况很特殊。 根据以上结果，我们认为：YidC亚家族蛋白在真细菌和一些广古菌中已起源；真核生物Oxa和Alb3基因有不同的原核起源，但它们的起源跟这两个细胞器的内共生起源事件无关；Oxa基因和Alb3基因在真核细胞进化早期即分别发生了古老的重复事件，因此现在绝大多数真核生物中均有两个Oxa和两个Alb3基因。但是后来在一些类群中，尤其是原生生物中，Oxa和Alb3基因发生了次生性丢失、新的复制或获得新的结构域编码片段，从而导致这些类群中这两种转运酶有丰富的多样性和不同的适应性。 最终，基于以上结果和结论，我们勾勒出了YidC/Oxa/Alb3超家族在整个生 I 物界中的进化路线图。

~(143)Dy和~(141)Dy的β缓发质子衰变与自旋指认

分析了143Dy和141Dy的β缓发质子衰变的数据,对比计算了这两种核的核位能面。从中看到了143Dy的衰变包括有1/2+基态和11/2-同核异能态的两种衰变成分,并且确定了它们的半衰期分别为(6.0±1.5)s和(3.0±0.5)s。同时也测定了141Dy的半衰期为(0.9±0.2)s,并指认了它的自旋宇称为9/2-。

~(140)Tb和~(141)Dy的β缓发质子衰变以及~(143)Dy的自旋宇称

利用40Ca+106Cd融合蒸发反应产生了近质子滴线核140Tb和141Dy,配合氦喷嘴带传输系统采用“质子-γ”符合方法观测了它们的β缓发质子衰变,其中包括半衰期、质子能谱和衰变到第二代子核不同低位态的分支比．通过统计理论拟合提取了140Tb和141Dy的基态自旋宇称分别为7±和9／2±．另一方面,用Woods-Saxon Strutinsky方法计算了这两种核限制组态的势能面,由此得到140Tb和141Dy的基态自旋宇称分别为7+和9／2-．此外用同一方法还计算了143Dy的核势能面,从中看出143Dy存在有自旋宇称为1／2+的基态和一个激发能为198keV的11／2-的同质异能态．该结果与2003年Eur．Phys．J． A16:347-351中的143Dy衰变实验数据相符．

~(143)Pm高自旋态研究

通过熔合蒸发反应12 8Te( 19F ,4nγ)布居了143Pm的高自旋态 ,利用在束γ谱学方法 ,对143Pm的高自旋态核结构进行了研究 .测量了γ射线单谱和γ -γ符合谱 ,并进行了γ射线各向异性以及DCO比率分析 ,建立了激发能高达1 0 53 5 4keV的能级纲图 ,其中包括新发现的 3 2条γ射线和 1 7个新能级 .用弱耦合模型对143Pm的晕态能级结构进行了解释

~(143)Nd中高自旋同质异能态的识别与研究

利用能量为 80MeV的18O束流 ,通过130 Te( 18O ,5n)反应研究了143Nd的高自旋态能级结构 .基于γ γ延迟符合、γ射线的角分布及线性极化测量 ,首次发现了143Nd的一个半寿命为 ( 35± 8)ns,自旋和宇称为 4 9/ 2 + 的同质异能态 .用形变独立粒子模型探讨了此同质异能态的形成机制

beta-delayed proton decays of Tb-140 and Dy-140 as well as the spin and parity of Dy-143

Tb-140 and Dy-141 were produced via fusion evaporation in the reaction Ca-40+Cd-106. Their beta-delayed proton decays were studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of Tb-140 and Dy-141 were extracted as 7(+/-) and 9/2(+/-), respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of Tb-140 and Dy-147 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 was also calculated by using the same method. From the NPES a 1/2(+) ground state and a 11/2(-) isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of Dy-143 reported in Eur. Phys. J., 2003, A16: 347-351.

beta-delayed proton decays and spin assignments for Tb-140, Dy-141 and Dy-143

The proton-rich isotopes Tb-140 and Dy-141 were produced via the fusion evaporation reaction Ca-40+ Cd-106. Their beta-delayed proton decays were studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nuclei were determined. Comparing the experimental data with statistical model calculations, the ground-state spins of Tb-140 and Dy-141 were found to be consistent with 7 and 9/2, respectively. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated using the Woods-Saxon-Strutinsky method, which suggest the ground-state spins and parities of Tb-140 and Dy-141 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 were calculated, which predict a 1/2(+) ground state and a 11/2(-) isomer with excitation energy of 198 keV. These findings are consistent with our previous experimental data on Dy-143 reported in Eur. Phys. J. A 16, 347 (2003).

Studies on organolanthanide complexes .58. Syntheses of 1,1'-(3-oxa-pentamethylene)dicyclopentadienyl divalent organolanthanides (Ln=Sm, Yb) and X-ray molecular structure of O(CH2CH2C5H4)(2)Yb(DME)

The compounds O(CH2CH2C5H4)(2)Ln(THF)(2) [Ln = Sm(1), Yb(2)] were synthesized by the reduction of O(CH2CH2C5H4)(2)LnCl with sodium metal in tetrahydrofuran (THF) at room temperature. Recrystallization of 2 from dimethoxyethane (DME) produced the single-crystal O(CH2CH2C5H4)(2)Yb(DME) (3) whose structure has been determined by an X-ray diffraction study. The crystals are orthorhombic, space group Pcab, with a = 14.168(4), b = 13.541(6), c = 19.314(8) Angstrom, Z = 8, D-calc. = 1.66 g cm(-3).