Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalli...Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.展开更多
Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, and mesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of these ...Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, and mesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of these polymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Their liquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. The results show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2) a flexible spacer will decrease the 'Jacket Effect' and the liquid crystallinity and 3) a subtle modification of the terminal groups on the mesogenic unit may also have a significant influence on properties of the polymers.展开更多
5S rDNA(即5S r RNA基因)是由120 bp的编码区和非转录间隔区(nontranscribed spacers,NTS)组成的串联重复序列,及其NTS区碱基序列和长度在不同的种间甚至在种内都有差异,从而形成种内和种间特有的不同重复单元类型,不同单元类型各自代...5S rDNA(即5S r RNA基因)是由120 bp的编码区和非转录间隔区(nontranscribed spacers,NTS)组成的串联重复序列,及其NTS区碱基序列和长度在不同的种间甚至在种内都有差异,从而形成种内和种间特有的不同重复单元类型,不同单元类型各自代表不同的基因组型,因此5S r DNA多基因家族是研究物种基因组结构的有效工具。本研究以生长在不同地区的四个新疆春小麦地方品种(黑芒麦)作为供试材料,通过TA克隆法获得了128个5S r RNA基因重复单元,每个品种都有长度为326~422 bp之间的短5S r DNA片段和长度为481~491 bp之间的长5S r DNA片段。通过多次序列比对,Blast比对,聚类分析等方法将所有序列分为不同的5S r DNA单元类型。在ZM5291和ZM52300中发现了Short A2、Short D1、Short G1、Long A1、Long D1和Long{S1等6种不同的单元类型,而在ZM5306和ZM5343中只发现了Short A2、Short D1、Short G1和Long{S1等4种不同的单元类型,丢失了Long A1和Long D1。依据5S r DNA各单元类型在山羊草属和小麦属二倍体物种及其异源多倍体物种中的分布情况确定这四个春小麦地方品种的基因组型为AABBDD,确实是普通小麦。本研究首次在普通小麦中发现了六种不同的5S r DNA单元类型,6种单元类型在这4个地方品种中的分布情况表明ZM5291和ZM5300 5S r DNA序列的一致进化程度比ZM5306和ZM5343弱,推测生长在不同地区的黑芒麦多倍体物种形成的时代不一样,并ZM5291和ZM5300比ZM5306和ZM5343可能具有来自各基因组祖先的丰富基因资源。本研究结果为鉴别新疆春小麦种质资源的基因组类型以及亲本选配和育种工作提供新的依据。展开更多
文摘Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.
基金This Project was supported by China Postdoctoral Science Foundation and National Natural Science Foundation of China (No. 59873001).
文摘Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, and mesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of these polymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Their liquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. The results show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2) a flexible spacer will decrease the 'Jacket Effect' and the liquid crystallinity and 3) a subtle modification of the terminal groups on the mesogenic unit may also have a significant influence on properties of the polymers.
文摘5S rDNA(即5S r RNA基因)是由120 bp的编码区和非转录间隔区(nontranscribed spacers,NTS)组成的串联重复序列,及其NTS区碱基序列和长度在不同的种间甚至在种内都有差异,从而形成种内和种间特有的不同重复单元类型,不同单元类型各自代表不同的基因组型,因此5S r DNA多基因家族是研究物种基因组结构的有效工具。本研究以生长在不同地区的四个新疆春小麦地方品种(黑芒麦)作为供试材料,通过TA克隆法获得了128个5S r RNA基因重复单元,每个品种都有长度为326~422 bp之间的短5S r DNA片段和长度为481~491 bp之间的长5S r DNA片段。通过多次序列比对,Blast比对,聚类分析等方法将所有序列分为不同的5S r DNA单元类型。在ZM5291和ZM52300中发现了Short A2、Short D1、Short G1、Long A1、Long D1和Long{S1等6种不同的单元类型,而在ZM5306和ZM5343中只发现了Short A2、Short D1、Short G1和Long{S1等4种不同的单元类型,丢失了Long A1和Long D1。依据5S r DNA各单元类型在山羊草属和小麦属二倍体物种及其异源多倍体物种中的分布情况确定这四个春小麦地方品种的基因组型为AABBDD,确实是普通小麦。本研究首次在普通小麦中发现了六种不同的5S r DNA单元类型,6种单元类型在这4个地方品种中的分布情况表明ZM5291和ZM5300 5S r DNA序列的一致进化程度比ZM5306和ZM5343弱,推测生长在不同地区的黑芒麦多倍体物种形成的时代不一样,并ZM5291和ZM5300比ZM5306和ZM5343可能具有来自各基因组祖先的丰富基因资源。本研究结果为鉴别新疆春小麦种质资源的基因组类型以及亲本选配和育种工作提供新的依据。
