L-Phe end-capped poly(L-lactide) as macroinitiator for the synthesis of poly(L-lactide)-B-poly(L-lysine) block copolymer

A poly(L-lactide)-b-poly(Nepsilon-(Z)-L-lysine) (PLLA-b-PZLys) block copolymer was synthesized through the ring-opening polymerization of Nepsilon-(Z)-lysine-N-carboxyanhydride using L-Phe-terminated PLLA as a macroinitiator. The L-Phe-terminated PLLA was prepared through a novel three-step process. First, the hydroxyl-terminated PLLA was synthesized through the ring-opening polymerization of L-lactide initiated by n-butanol under the existence of tin(II) ethylhexanoate. Subsequently, the complete capping of the hydroxyl end group of PLLA with BOC-L-Phe was achieved by using a mixed anhydride of BOC-L-Phe under the catalysis of 4-(1-pyrrolidinyl) pyridine. Finally, the free amino end group was obtained by removal of the t-butoxycarbonyl group through trifluoroacetic acid treatment under anhydrous condition. All these treatments were conducted under mild conditions, thus avoiding the breakdown of the PLLA backbone. Poly(L-lactide)-b-poly(L-lysine) block copolymer was produced after deprotection treatment of PLLA-b-PZLys. The structure of the block copolymer was confirmed by 1H NMR, IR, and GPC. Adjustment of the ratio of the NCA monomer to the macroinitiator could control the chain length of the PLys block.     

Synthesis and anti-HIV-1 activity of 4-substituted-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine analogues

Three novel 4-subsituted-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine analogues were designed, synthesized, and tested for their anti-HIV-1 activity. Initial biological studies indicated that among these pyrrolo[2,3-d]pyrimidine ribonucleoside analogues, 4-amino-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine 10 exhibited the most potent anti-HIV-1 activity (EC(50)=0.5±0.3 μM), while 4-hydroxy-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d] pyrimidine 9 and 4-amino-5-fluoro-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d] pyrimidine 11 showed moderate activity (EC(50)=13±8 and 5.4±0.3 μM, respectively). The cytotoxicity of these compounds has also been assessed. No significant cytotoxicities were found for any of these compounds with concentrations up to 25 μM.     

中国海兽研究概述

我国对海兽的研究已有80多年的历史.为了回顾我国海兽研究的历史,总结我国海兽研究的进展,并展望我国海兽研究的未来,借<兽类学报>创刊30周年之际,作者查阅了大量历史文献,并结合我们的研究积累,从鲸类、鳍脚类和其他海兽三个类群分别综述了我国海兽研究的进展.本文重点总结了我国几种代表性海兽的生态学、饲养与繁殖生物学、保护遗...     

Characterization of milk composition in narrow‐ridged finless porpoises (Neophocaena asiaeorientalis) at different lactation stages

Lactation plays a vital role in reproductive success, evolving with ecological adaptations of mammalian life histories. Knowledge of the lactation process in odontocetes is scarce and limited to a handful of species. We investigated the changes in milk composition across different lactation stages, including prepartum mammary secretion and early, mid‐ and late lactation of narrow‐ridged finless porpoises. Prepartum mammary secretion was greenish and characterized by high protein, low sugar, and negligible fat contents. In contrast, milk fat became predominant over protein and sugar contents throughout all lactation stages. At the early lactation stage, the contents of all milk constituents except water varied greatly. At the mid‐late lactation stage, the gross milk composition was relatively stable and was composed of, on average, 67.34% ± 4.13% water, 9.96% ± 0.75% protein, 21.40% ± 3.24% fat, and 1.72% ± 0.73% sugar. Our findings provide new insight into milk composition at different lactation stages in the narrow‐ridged finless porpoise.     

开都河流域天山桦树轮宽度年表的建立及其气候响应

利用开都河流域中段采集的天山桦树芯样本,建立了这一采样点的树轮宽度年表。该年表的特征参数与其他地区已有的桦木树轮宽度年表相近,且能较好地反映研究区内天山桦树轮宽度变化的基本特征。该年表与研究区内雪岭云杉树轮宽度年表间的相关分析表明,两者在全频域、高频域及低频域上均存在显著正相关。树木生长气候响应分析结果显示,天山桦树轮宽度与降水量的相关则不显著;而与上年12月呈显著正相关(r= 0.346,P < 0.01,n=59),与当年6月的平均气温呈显著负相关(r=-0.312,P < 0.01,n=60)。该年表存在2.1、4.0a和~50a变化准周期,并且其与3月多元El Nio-Southern Oscillation (ENSO)指数存在相似的变化趋势。     

新疆赛里木湖流域过去373年降水变化的树轮记录

利用采自天山西部赛里木湖流域的树木年轮标准化宽度年表,重建了赛里木湖流域过去373年上年8月到当年7月的降水变化,重建序列的解释方差达到39.8%,多方验证表明,重建结果是稳定可靠的。分析历史降水变化特征表明,赛里木湖流域过去373年的降水经历了6干7湿的阶段变化,其中,持续最长的干旱阶段为1762—1791年,而最为干旱的阶段为1841—1865年;持续最长的湿润阶段为1794—1840年,而最为湿润的阶段为1734—1761年间;赛里木流域历史降水存在3个极端湿润年(1749,1876和1924年)和4个极端干旱年(1714,1775,1847和1917年),1910年代为最干旱的十年;降水变化存在11—12a、3.0a、2.5a、2.1a和2.0a的变化准周期;赛里木湖流域过去373年的降水的阶段变化、周期变化和极端降水年份均与天山北坡中西部和中亚天山山区降水变化具有很好的一致性,本研究的降水重建序列能较好的代表天山北坡中西部和中亚大部分区域历史降水变化。     

树轮宽度记录的额尔齐斯河上游地区过去291年的降水变化

利用采自额尔齐斯河上游6个采点的西伯利亚云杉(Picea obovata Ledeb)树轮样本建立了区域树轮宽度年表。与气候要素的相关分析表明,该地区树木径向生长主要受降水制约,区域树轮宽度年表与富蕴气象站上年7月至当年6月的降水总量相关显著。在此基础上建立了转换方程,重建了额尔齐斯河上游地区1722—2012年上年7月至当年6月的降水总量,方差解释量高达55.1%(调整自由度后为54.2%)。重建结果显示,该地区过去291年间存在9个降水偏多的时期和8个降水偏少的时期。降水重建序列还存在2.1a和3.2a的显著周期及2.3、21.6、24.3a的较显著周期,并且在1876—1877年及1983年前后发生了降水突变。空间相关分析表明,重建的上年7月至当年6月降水量对额尔齐斯河上游阿勒泰地区的降水量具有很好的空间代表性。此外,重建结果还与周边地区其他基于树轮资料重建的降水序列的干湿变化有较好的一致性。     

Targeting the exogenous htPAm gene on goat somatic cell beta-casein locus for transgenic goat production

Combining gene targeting of animal somatic cells with nuclear transfer technique has provided a powerful method to produce transgenic animal mammary gland bioreactor. The objective of this study is to make an efficient and reproducible gene targeting in goat fetal fibroblasts by inserting the exogenous htPAm cDNA into the beta-casein locus with liposomes or electroporation so that htPAm protein might be produced in gene-targeted goat mammary gland. By gene-targeting technique, the exogenous htPAm gene was inserted to milk goat beta-casein gene sequences. Fetal fibroblasts were isolated from Day 35 fetuses of Guanzhong milk goats, and transfected with linear gene-targeting vector pGBC4htPAm using Lipefectamin-2000 and electoporation, respectively. Forty-eight gene-targeted cell colonies with homologous recombination were obtained, and three cell colonies were verified by DNA sequence analysis within the homologous recombination region. Using gene-targeted cell lines as donor cells for nuclear transfer, a total of 600 reconstructed embryos had been obtained, and 146 developed cloned embryos were transferred to 16 recipient goats, and finally three goats showed pregnancy at Day 90.