崖柏属的系统发育与生物地理学研究－兼论广义柏科4CL���因的进化

第三纪末期和第四纪的气候变冷使广泛分布于北半球的暖温带/亚热带生物区系的分布区破碎化，形成了各种洲际间断分布格局。其中东亚—北美东部间断分布最为常见，自林奈时代起就吸引了植物学家们的关注。为了探讨这一地理分布格局的形成过程，前人开展了大量的研究工作，包括间断类群分布的比较、种间关系的经典分类学和化学分类学研究、地理分布的分支分析、遗传距离的估算等。随着分子系统学的发展，在各级分类阶元水平上探讨植物系统发育关系的研究取得了重大进展，很多植物类群的系统发育得到了重建，这使东亚－北美间断分布类群的历史生物地理学研究变得更为切实可行。同时，生物地理学的理论有了新的发展，新的分析方法不断涌现，化石记录及古气候和古地质资料得到大量积累，为深入探讨东亚—北美间断分布提供了条件。目前，已有20 多个东亚－北美间断分布的植物类群被详细研究，丰富了我们对这一现象的认知。然而，以往的研究多基于单亲遗传的叶绿体基因和（或）PCR 直接测序所得的nrDNA ITS 序列，在探讨杂交和网状进化方面存在较大的局限性。在本研究中，我们选取了崖柏属（Thuja L.）这一典型东亚—北美间断分布类群，用来自叶绿体和细胞核的多个基因序列重建其系统发育，探讨其地理分布格局的形成过程，并讨论不同遗传体系的多基因联合分析在植物生物地理学研究中的应用。此外，我们还初步探讨了低拷贝核基因4CL 在广义柏科的进化式样。 1、崖柏属的系统发育和生物地理学研究 崖柏属共 5 种，其中3 种分布于东亚，2 种分别分布于北美东、西部。我们用5 个叶绿体DNA 片段（rpl16 内含子, atpI-rpoC1、trnS-trnfM 和trnS-trnG 基因间区以及trnT-trnF 区）和3 个核基因片段（ITS���LEAFY，4CL���的序列重建了崖柏属的系统发育。发现：（1）基因树拓扑结构的冲突存在于叶绿体基因和核基因之间，甚至不同的核基因之间，说明崖柏属曾发生多次种间杂交并导致网状进化;（2）崖柏属中存在两个种对，即日本香柏－崖柏和朝鲜崖柏－北美香柏;（3）朝鲜崖柏在叶绿体和核基因树上位于不同的位置，可能因古老的杂交和叶绿体捕获所致;（4）北美乔柏的叶绿体基因存在镶嵌式的变异，可能在物种形成过程中发生了叶绿体重组。根据分子钟度量结果，崖柏属两个种对的分化时间为51.1±3.96 Mya，日本香柏和崖柏的分化时间为23.7±5.04 Mya，朝鲜崖柏和北美乔柏的分化时间为14.7±6.06 Mya。 基于多个基因的系统发育分析、DIVA 分析、化石证据和分子钟度量，我们推测崖柏属在古新世或更早的时候起源于北美高纬度地区，并通过白令陆桥扩散到东亚，然后通过隔离分化形成日本香柏－崖柏这一种对。白令陆桥和阿留申陆桥可能在崖柏属的进一步迁移中起了重要介导作用，使崖柏属内发生了多次种间杂交事件，并导致了崖柏－日本香柏和朝鲜崖柏－北美香柏这两种主要的叶绿体类型间的重组以及朝鲜崖柏对北美香柏叶绿体基因的捕获。携带重组叶绿体DNA 的杂交个体迁入北美西部，产生了北美乔柏。根据分子钟估算结果，该迁移事件可能发生在中新世。 鉴于以往对东亚—北美间断分布植物类群的分子系统学研究多基于单亲遗传的叶绿体基因和（或）PCR 直接测序的ITS 数据，这些类群中的网状进化事件可能被低估。同时，我们的结论也部分解释了为什么东亚、北美东部、北美西部三者间的关系存在很多争议：频繁的杂交和渐渗模糊了种间的系统发育关系。因此，我们建议在生物地理学研究中用来源于多个基因组的多基因分析，特别是用单/低拷贝核基因。 2、广义柏科4CL 基因进化的初步研究 广义柏科是松杉类植物中唯一在南、北半球广泛分布的类群，该科中既有古老的孑遗属和寡种属，也有第三纪起源、呈南北半球间断分布的类群。研究4CL 基因在这一类群中的进化，有助于探讨低拷贝核基因在松杉类植物中的进化式样和规律。4CL 在植物次生化合物的生物合成中起重要作用，它催化激活4-香豆酸和一些相关的底物形成不同的辅酶A，促进各种苯丙烷类的代谢。 我们从广义柏科 17 个属中扩增并克隆到23 条4CL 基因序列。基因结构和系统发育分析表明，4CL 在广义柏科中分为4CLI 和4CL II 两大类，二者间的序列相似性为67-70％，进化速率也有很大差异。RT-PCR 结果证明这两种类型均能转录，推测它们都具有功能，且基因结构的差异和序列之间的高度分化暗示这两大类可能执行不同的功能。在4CL 基因树中，落羽杉亚科、北美红杉亚科、狭义柏科的单系都得到了支持。尽管4CL 在广义柏科中的类型及拷贝数还有待研究，但4CLI 很可能以单拷贝或低拷贝存在，其高变的内含子序列可以用来探讨种间的系统发育关系。

Geographic variation in the leaf essential oils of Juniperus sabina L. and J-sablina var. arenaria (E.H. Wilson) Farjon

The composition of the leaf oils from seven populations of J. sabina L., one population of Juniperus sabina var. arenaria (E. H. Wilson) Farjon were examined for their geographic variation. In addition, the leaf oils of J. chinensis L. and J. davurica Pall. were compared to J. sabina. Juniperus sabina var. arenarla, the sand loving juniper, oil was found to be very similar to that of J. davurica, Mongolia, and J. sabina, on sand dunes in Mongolia. This suggests that J. sabina var. arenaria might be conspecific with J. davurica. Farjon's move (2001) of J. sabina var. arenaria out of J. chinensis is supported. Considerable differentiation was found in populations of J. sabina from the Iberian peninsula. Cedrol, citronellol, safrole, trans-sabinyl acetate, terpinen-4-ol and beta-thujone were found to be polymorphic in several populations.

Towards executable specification : combining i* and AgentSpeak(L).

Agent-oriented conceptual modelling (AoCM) approaches in Requirements Engineering (RE) have received considerable attention recently. Semi-formal modeling frameworks such as i* assist analysts in requirements elicitation and reasoning of early-phase RE. AgentSpeak(L) is a widely accepted agent programming language. The Strategic Rationale (SR) model of the i* framework naturally lends itself to AgentSpeak(L) programs. Furthermore, the Strategic Dependency (SD) component of the i* framework prescribes the interaction between the agents in a multi-agent environment. This paper proposes a formal methodology for transforming a SR model to an AgentS- peak(L) agent. The constructed AgentSpeak(L) agents will then form the essential components of a multi-agent system, MAS.

Enhanced human bone marrow stromal cell affinity for modified poly(L-lactide) surfaces by the upregulation of adhesion molecular genes

To enhance and regulate cell affinity for poly (l-lactic acid) (PLLA) based materials, two hydrophilic ligands, poly (ethylene glycol) (PEG) and poly (l-lysine) (PLL), were used to develop triblock copolymers: methoxy-terminated poly (ethylene glycol)-block-poly (l-lactide)-block-poly (l-lysine) (MPEG-b-PLLA-b-PLL) in order to regulate protein absorption and cell adhesion. Bone marrow stromal cells (BMSCs) were cultured on different composition of MPEG-b-PLLA-b-PLL copolymer films to determine the effect of modified polymer surfaces on BMSC attachment. To understand the molecular mechanism governing the initial cell adhesion on difference polymer surfaces, the mRNA expression of 84 human extracellular matrix (ECM) and adhesion molecules was analysed using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). It was found that down regulation of adhesion molecules was responsible for the impaired BMSC attachment on PLLA surface. MPEG-b-PLLA-b-PLL copolymer films improved significantly the cell adhesion and cytoskeleton expression by upregulation of relevant molecule genes significantly. Six adhesion genes (CDH1, ITGL, NCAM1, SGCE, COL16A1, and LAMA3) were most significantly influenced by the modified PLLA surfaces. In summary, polymer surfaces altered adhesion molecule gene expression of BMSCs, which consequently regulated cell initial attachment on modified PLLA surfaces.

Synthesis of 4-arm star poly(L-Lactide) oligomers using an in situ-generated calcium-based initiator

Using an in situ-generated calcium-based initiating species derived from pentaerythritol, the bulk synthesis of well-defined 4-arm star poly(L-lactide) oligomers has been studied in detail. The substitution of the traditional initiator, stannous octoate with calcium hydride allowed the synthesis of oligomers that had both low PDIs and a comparable number of polymeric arms (3.7 – 3.9) to oligomers of similar molecular weight. Investigations into the degree of control observed during the course of the polymerization found that the insolubility of pentaerythritol in molten L-lactide resulted in an uncontrolled polymerization only when the feed mole ratio of L-lactide to pentaerythritol was 13. At feed ratios of 40 and greater, a pseudo-living polymerization was observed. As part of this study, in situ FT-Raman spectroscopy was demonstrated to be a suitable method to monitor the kinetics of the ring-opening polymerization (ROP) of lactide. The advantages of using this technique rather than FT-IR-ATR and 1H NMR for monitoring L-lactide consumption during polymerization are discussed.

L'étendue internationale des nouvelles firmes de hautes technologies: le rôle du capital humain et de l'intention stratégique des fondateurs

De récentes recherches ont mis l���accent sur l���importance pour les nouvelles entreprises internationales de l���existence de ressources et de compétences spécifiques. La présente recherche, qui s���inscrit dans ce courant, montre en particulier l���importance du capital humain acquis par les entrepreneurs sur base de leur expérience internationale passée. Mais nous montrons en même temps que ces organisations sont soutenues par une intention délibérée d’internationalisation dès l���origine. Notre recherche empirique est bas��e sur l���analyse d’un échantillon de 466 nouvelles entreprises de hautes technologies anglaises et allemandes. Nous montrons que ce capital humain est un actif qui facilite la pénétration rapide des marchés étrangers, et plus encore quand l���entreprise nouvelle est accompagnée d’une intention stratégique délibérée d’internationalisation. Des conclusions similaires peuvent être étendues au niveau des ressources que l���entrepreneur consacre à la start-up : plus ces ressources sont importantes, plus le processus d’internationalisation tend à se faire à grande échelle ; et l�� aussi, l���influence de ces ressources est augmenté par l���intention stratégique d’internationalisation. Dans le cadre des études empiriques sur les born-globals (entreprises qui démarrent sur un marché globalis��), cette recherche fournit une des premières études empiriques reliant l���influence des conditions initiales de création aux probabilités de croissance internationale rapide.

Three-dimensional hydrogen-bonded structures in the 1:1 proton-transfer compounds of L-tartaric acid with the associative-group monosubstituted pyridines 3-minopyridine, 3-carboxypyridine (nicotinic acid) and 2-carboxypyridine (picolinic acid).

The 1:1 proton-transfer compounds of L-tartaric acid with 3-aminopyridine [3-aminopyridinium hydrogen (2R,3R)-tartrate dihydrate, C5H7N2+·C4H5O6-·2H2O, (I)], pyridine-3-carboxylic acid (nicotinic acid) [anhydrous 3-carboxypyridinium hydrogen (2R,3R)-tartrate, C6H6NO2+·C4H5O6-, (II)] and pyridine-2-carboxylic acid [2-carboxypyridinium hydrogen (2R,3R)-tartrate monohydrate, C6H6NO2+·C4H5O6-·H2O, (III)] have been determined. In (I) and (II), there is a direct pyridinium-carboxyl N+-HO hydrogen-bonding interaction, four-centred in (II), giving conjoint cyclic R12(5) associations. In contrast, the N-HO association in (III) is with a water O-atom acceptor, which provides links to separate tartrate anions through Ohydroxy acceptors. All three compounds have the head-to-tail C(7) hydrogen-bonded chain substructures commonly associated with 1:1 proton-transfer hydrogen tartrate salts. These chains are extended into two-dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three-dimensional hydrogen-bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet struture of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O-atom acceptors of the primary tartrate chains, closing conjoint cyclic R44(8), R34(11) and R33(12) associations. Also, in (II) and (III) there are strong cation carboxyl-carboxyl O-HO hydrogen bonds [OO = 2.5387 (17) Å in (II) and 2.441 (3) Å in (III)], which in (II) form part of a cyclic R22(6) inter-sheet association. This series of heteroaromatic Lewis base-hydrogen L-tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two-dimensional hydrogen-bonded hydrogen tartrate or hydrogen tartrate-water sheet substructures which are expanded into three-dimensional frameworks via peripheral cation bifunctional substituent-group crosslinking interactions.

Carbodiimide-mediated synthesis of poly(L-lactide)-based networks

Poly(L-lactide-co-succinic anhydride) networks were synthesised via the carbodiimide-mediated coupling of poly(L-lactide) (PLLA) star polymers. When 4-(dimethylamino)pyridine (DMAP) alone was used as the catalyst gelation did not occur. However, when 4-(dimethylamino)pyridinium p-toluenesulfonate (DPTS), the salt of DMAP and p-toluenesulfonic acid (PTSA), was the catalyst, the networks obtained had gel fractions comparable to those which were reported for networks synthesised by conventional methods. Greater gel fractions and conversion of the prepolymer terminal hydroxyl groups were observed when the hydroxyl-terminated star prepolymers reacted with succinic anhydride in a one-pot procedure than when the hydroxyl-terminated star prepolymers reacted with presynthesised succinic-terminated star prepolymers. The thermal properties of the networks, glass transition temperature (Tg), melting temperature (Tm) and crystallinity (Xc) were all strongly influenced by the average molecular weights between the crosslinks ((M_c). The network with the smallest (M_c )(1400 g/mol) was amorphous and had a Tg of 59 °C while the network with the largest (M_c ) (7800 g/mol) was 15 % crystalline and had a Tg of 56 °C.

Phenyl-ring disorder in the two-dimensional hydrogen-bonded structure of the 1:1 proton-transfer salt of the diazo-dye precursor 4-(phenyldiazenyl)aniline (aniline yellow) with L-tartaric acid

The structure of the 1:1 proton-transfer compound from the reaction of L-tartaric acid with the azo-dye precursor aniline yellow [4-(phenylazo)aniline], 4-(phenyldiazenyl)anilinium hydrogen 2R,3R-tartrate C12H12N3+ . C4H6O6- has been determined at 200 K. The asymmetric unit of the compound contains two independent phenylazoanilinium cations and two hydrogen L-tartrate anions. The structure is unusual in that all four phenyl rings of both cations have identical 50% rotational disorder. The two hydrogen L-tartrate anions form independent but similar chains through head-to-tail carboxylic O--H...O~carboxyl~ hydrogen bonds [graph set C7] which are then extended into a two-dimensional hydrogen-bonded sheet structure through hydroxyl O--H...O hydrogen-bonding links. The anilinium groups of the phenyldiazenyl cations are incorporated into the sheets and also provide internal hydrogen-bonding extensions while their aromatic tails layer in the structure without significant interaction except for weak \p--\p interactions [minimum ring centroid separation, 3.844(3) \%A]. The hydrogen L-tartrate residues of both anions have the common short intramolecular hydroxyl O--H...O~carboxyl~ hydogen bonds. This work has provided a solution to the unusual disorder problem inherent in the structure of this salt as well as giving another example of the utility of the hydrogen tartrate in the generation of sheet substructures in molecular assembly processes.