温度及膜中蛋白质含量与膜粘度和膜中分子排列方向的关系

本实验用闪光诱导的瞬间二向色性方法测量了不同温度以及不同蛋白质含量下菌紫质分子在脂质囊泡膜中的旋转扩散运动.根据旋转扩散运动得到了温度和蛋白质含量与膜粘度以及分子在膜中排列方向的关系.温度和蛋白质的含量都影响膜的粘度,但并不影响蛋白质分子在膜中的排列方向.     

例析等位基因显、隐性关系的分子机理

孟德尔提出的显性和隐性概念从个体表型水平描述了一对遗传因子的功能关系。高中生在初学时会产生困惑,随着学习的深入,教师应引导学生分析明确:等位基因的显、隐性关系取决于基因的表达产物是否最终"发挥作用"进而决定个体表型。从2个常见误区出发,用案例阐述了基因显、隐性关系的分子水平解释,明确了关系判断的原则;借用2道北京高考遗传题分析了上述分子机理在试题中的呈现;通过若干案例拓展了表观遗传学背景下的等位基因显、隐性关系分析。     

第六次全国医学遗传学学术会议通知（第一轮）

中国遗传学会和中华医学会医学遗传学会分会定于2005年12月16日-18日在北京召开第六次全国医学遗传学学术会议。会议将邀请国内知名专家围绕医学分子遗传学、分子细胞遗传学、医学基因组学、临床遗传学、复杂疾病遗传学、肿瘤遗传学、发育遗传学、表观遗传学、群体遗传学和遗传流行病学、遗传病动物模型、基因诊断和基因治疗等领域的新进展作专题学术报告     

单分子实时测序及其在微生物表观遗传学中的应用

表观遗传学对于微生物的生命进程起着重要作用。由限制-修饰系统调控的DNA修饰参与微生物的免疫防御系统,无限制-修饰系统调控的DNA修饰通过调控基因表达影响表型。然而,表观遗传信息还没有被常规地作为DNA信息收集分析。基于对DNA合成反应的动力学分析,单分子实时测序技术可以在获得基本序列数据的同时实现对被修饰核苷酸的检测。这个技术为微生物中已知DNA修饰的研究提供了新的平台,也为新型DNA修饰的发现做好准备。本文综述了单分子实时测序技术及其在微生物表观遗传学中的应用。     

分子运动性预测麻栎种子离体胚轴适宜贮藏条件初探

应用电子顺磁共振波谱仪和自旋标记技术,以硝基氧探针为标记物,检测了室温下麻栎种子离体胚轴脱水过程中分子运动性的变化。发现含水量0.7gH2O/gDW至0.64gH2O/gDW范围是细胞质粘度的转折区域,低于这个含水量区域,细胞质粘度骤然上升,推测这个区域是室温下保存离体胚轴的适宜含水量下限。通过变温电子顺磁共振波谱测定,找到离体胚轴含水量在0.43gH2O/gDW至1.02gH2O/gDW范围内,分子运动性的临界温度和玻璃态相变温度所在区间。根据分子运动性随温度变化的规律,预测含水量为0.69gH2O/gDW的麻栎种子离体胚轴适宜贮藏温度约为-50℃。     

植物春化作用的分子机制及应用

植物能响应环境中的低温信号实现开花调控，这种经历低温促使植物开花的作用即为春化作用。本文结合国内外春化作用的研究进展，概述春化作用的发现和特点，阐述模式植物拟南芥及单子叶作物的春化作用分子机制，并举例说明春化作用在农业、园艺等方面的应用。     

LncRNA的结构、功能及其与疾病的关系

70%的人类基因组能够被转录,而其中仅有1%～2%的转录本能够编码蛋白,余下98%均为非编码RNA（non-coding RNA,ncRNA）.在ncRNA中,长度大于200核苷酸称为长链非编码RNA（long non-coding RNA,LncRNA）,占全部ncRNA的80%～90%．LncRNA除了数量庞大以外,还具有表达量较低、物种间保守性较差及细胞表达特异性等特点,使LncRNA结构及作用机制等研究充满挑战．目前关于LncRNA的研究主要集中于功能方面．LncRNA能够广泛参与生物体的各种生理及病理过程,如表观遗传学调控、癌症、神经系统功能等．LncRNA作用机制众多,能够以分子诱饵、分子向导、分子支架及信号通路的调节剂等多种角色参与调节机体各种生物学过程．解析LncRNA的分子结构、深入研究其在生物体生理及病理过程中所发挥的作用,并揭示其作用机制,不仅能够加深对生物体生理及病理过程的认识,同时也能给某些疾病的诊断、防治提供新的思路及解决途径．本文综述了近年来有关LncRNA结构、功能及作用机制相关研究进展,以期为后续LncRNA相关研究提供参考.     

表观遗传标记在猪分子育种中的研究与应用前景

家畜动物的表型是由基因组、表观基因组和环境等多种因素相互影响共同作用决定的。近年来,随着遗传育种领域的迅速发展,表观遗传标记在猪分子育种中的研究受到越来越多科研人员的关注。表观遗传学是研究基因表达发生可遗传的改变而DNA序列不发生改变的一门生物学分支学科,其遗传标记主要包括DNA甲基化、组蛋白修饰、非编码RNA、印记基因等。越来越多的研究表明,表观遗传标记在猪的遗传性状中发挥着重要作用,主要通过调控与性状相关基因的表达进而达到改变生物表型的目的。然而,在当前猪分子育种领域,表观遗传标记的作用还没有得到足够的重视,影响猪重要性状的机制还没有得到深度解析,因此在实际应用中还缺乏足够的科学依据和可操作性。本文从营养、疾病、重要经济性状以及隔代遗传几个方面综述了表观遗传标记在猪分子育种中的研究现状、应用前景以及遇到的挑战,以期为表观遗传标记在猪分子育种中的应用提供较全面的理论依据。     

精准医学基础研究与临床实践的回顾与展望

精准医学是健康卫生和医学科学的发展方向,是发展了一个多世纪的现代医学实践的升级版。本文研究了医学科研和医疗实践的发展趋势,从分子遗传、环境变迁及医疗信息管理等领域,分析和总结了影响精准医学发展的一些因素,提出了精准医学基础研究和临床实践的一些新思路,希望对精准医学的发展、医学科研实践及医疗卫生政策的制定产生积极的影响。     

粘度法研究牛血清蛋白蛋白的溶液行为

经粘度法测量证明牛血清白蛋白在ＮａＣｌ,ＫＳＣＮ和ＫＩ３种盐溶中的流体力学行为有较大差别,并按经验公式由粘度数据计算了表观分子轴比较和分子体积,它们也随盐的种类不同而相应变化,     

白芨多糖胶-瓜尔胶复配溶液的流变性

考察了瓜尔胶溶液和白芨多糖胶-瓜尔胶复配溶液的流变特性。两组溶液呈现典型的假塑性,不同浓度下两组溶液表观黏度(ηa)随剪切速率(τ)的变化可以用Ostwald-Dewaele方程描述。白芨多糖胶和瓜尔胶复配产生协同增效作用,复配溶液的ηa大于单一组分的白芨多糖胶溶液或瓜尔胶溶液的ηa。复配溶液中白芨多糖胶与瓜尔胶的最佳配比是质量比为9∶1。     

灵芝液态发酵高产胞外多糖菌株筛选及多糖特性分析

对10株灵芝菌株发酵菌丝体生物量、胞内多糖含量、胞外粗多糖得率及其多糖含量和单糖组成特征进行了系统分析。结果表明,随着培养时间的延长,10株菌株的生物量均有不同程度增加,但不同菌株胞内多糖含量和胞外粗多糖得率变化趋势有所不同。在培养至7d时,G0023和G0160菌株胞外粗多糖得率均较高,分别为3.02g/L和3.14g/L,其多糖含量分别达到了84.11%和91.03%,可作为发酵高产胞外多糖的优良菌株。分级醇沉胞外多糖分析结果表明,各菌株胞外液20%乙醇沉淀所得20E组分的得率和多糖含量均高于50%乙醇沉淀所得的50E组分,说明胞外液中主要以大分子量多糖为主。20E主要由葡萄糖组成,含有少量木糖和甘露糖;50E主要由葡萄糖和甘露糖组成,含有少量木糖和半乳糖。胞外液表观粘度随剪切速率变化曲线分析结果显示,各菌株胞外液均呈现剪切变稀非牛顿流体特性,其表观粘度大小与菌株对应20E组分的得率及多糖含量呈正相关。     

酿酒酵母发酵降解灵芝胞外多糖组分分析及活性研究

本研究采用酿酒酵母发酵的方法对灵芝胞外多糖进行了降解,并对其产物在表观粘度、分子量、多糖得率和含量及单糖组成和生物活性等方面进行了系统比较和分析。结果表明,灵芝发酵胞外液经酿酒酵母培养后,所得胞外液的表观粘度明显降低,其中多糖的分子量也随酵母培养时间的延长出现下降趋势,大分子多糖的分子量从3.55×10 ⁶g/mol下降到1.93×10 ⁶g/mol,低分子多糖的分子量从6.18×10 ⁴g/mol下降到3.11×10 ⁴g/mol。多糖得率和含量测定结果显示,经酵母培养后,灵芝胞外液中20%乙醇沉淀所得20E组分得率明显降低,从2.43g/L下降到0.98g/L,但该组分多糖含量均较高,达到70%以上;而70%乙醇沉淀所得70E组分得率明显增加,达到1.87g/L。单糖组成分析表明,20E组分主要由葡萄糖组成,70E组分主要由甘露糖组成。各组分均表现出较好的与Dectin-1受体结合激活NF-κB增强免疫的活性,且经酿酒酵母发酵24h所得70E组分的活性最好。     

4-O-Methylglucuronoxylan Isolated from the Midrib of Nicotiana tabacum

An acidic xylan from the midrib of Nicotiana tabacum was isolated by alkaline extraction and fractionation on a DEAE-cellulose column. Based on the results of methylation analysis, partial acid hydrolysis and Smith degradation, the acidic xylan was concluded to be composed of a linear backbone of β-(1→4)-linked D-xylopyranosyl residues with approximately every ninth residue carrying a terminal 4-O-methyl-α-D-glucopyranosyluronic acid residue linked as a single side chain by (1→2) linkage.     

Rheological properties of the water-soluble mucilage of a green laver, Monostroma nitidium

A study was made to explore the rheological properties of the water-solublemucilage of a green laver, Monostroma nitidium. The apparentviscosity of the water-soluble mucilage decreased with increasing shear rate,with increasing solution temperature (from 4 to 70 °C), withincreasing NaCl concentration from (0.5% to 2.0%), and decreasedslightly with a shearing time for 60 min. The decreases in the apparentviscosity were more pronounced for higher-concentration water-solublemucilage. However, it increased with increasing solution pH from pH 3 to 9.     

Transit time and digestibility of two experimental diets in the maned wolf (Chrysocyon brachyurus) and domestic dog (Canis lupus)

Recent research involving nutritional management of clinical disease secondary to cystinuria in captive maned wolves (Chrysocyon brachyurus) in the United States resulted in the production of a commercially manufactured maintenance diet and subsequently, a further modified experimental diet. These two diets differed only in their protein sources and sodium concentrations. The purpose of this study was to further investigate these diets by determining their digestibility and transit time in maned wolves, and also to compare these results to the digestibility and transit time of the diets in domestic dogs. The experiment consisted of two diets (maned wolf commercial maintenance diet and experimental diet) and two species (maned wolf and domestic dog [beagle]) arranged as a 2 × 2 factorial design. For the transit time study, titanium dioxide (TiO₂, 5 g/kg diet) was administered as a pulse dose and total collection of feces was carried out for 50 hr. There was no effect of diet or species on initial Ti recovery time (IRT), the amount of Ti recovered at IRT, or the time to reach 50% of Ti excretion in the feces. Maned wolves had lower total percent recovery (P<0.01) of Ti than dogs and shorter time to last recovery of Ti in the feces (P<0.05), however, marker excretion in the maned wolves may not have been complete. For the digestibility study, in which chromic oxide was used as a marker, fecal samples were collected on 2 consecutive days immediately after 12 days of being fed the diets and then analyzed for dry matter, energy, protein, and minerals. Crude protein, calcium, phosphorus, and zinc apparent digestibilities were unaffected by species or diet (P>0.05). Apparent digestibility of dry matter (P<0.05) and energy (P<0.01) were higher in the experimental diet and in the dogs. Both dogs and maned wolves fed the maintenance diet exhibited a greater apparent retention of copper, iron, and magnesium (P<0.01). Dogs had a higher apparent retention of magnesium and sodium than the maned wolves. Zoo Biol 0:1–13, 2006. © 2006 Wiley‐Liss, Inc.     

Apparent densities of spermatozoa of various mammalian species

The apparent densities of sperm cells in several mammalian species were determined by means of Percoll density-gradient centrifugation. Semen samples were obtained from (1) ejaculates from the bull, human, and rabbit, and (2) from the cauda epididymis of the goat, golden hamster, house musk shrew, mastomys, and mouse. The profiles of sperm distribution showed a single peak after the centrifugation in the first group and goat, whereas two separate main peaks in the second group (except goat). This disparity in sperm distribution profiles may be due mainly to differences in the degree of maturity of the sperm. Highly motile and mature sperm were obtained at higher densities, whereas immotile or immature sperm were found at the apparent densities. Thus, in mammals, the profiles of sperm distribution in the Percoll density gradient are classified into two types, those with a single peak and those with two separate peaks. The apparent density of sperm cells may be of importance in sperm physiology.     

Indirect population interaction between two aphid species

We designed an experiment to test whether two species of aphid feeding on different species of host plant influence each others population dynamics via shared parasitoids (apparent competition) or other indirect processes. Pea aphid ( Acyrthosiphon pisum ) colonies declined faster towards mid-summer when there were nearby colonies of nettle aphid ( Microlophium carnosum ), though the significance of the difference ( P  = 0.06) was just short of the traditional 0.05 level. Observations suggested that parasitoids were not responsible for this difference, however, and that it was highly likely to be caused by aphid-specific predators.     

Perception of fluids with diverse rheology applied to the underarm versus forearm skin

Little is known about the tactile–perceptual structure of fluids. Therefore, ten fluids with diverse, characterized rheologies were rated by 16 females, on 27 sensory attributes (e.g., “slippery”) and 14 emotional attributes (e.g., “enjoyable”) via five-point categorical scales. Fluids were assessed against the volar forearm and underarm, sites that commonly experience contact with fluids during the use of personal care products. Application of fluids was either by the participant to their own body (“self-applied”) or by the experimenter to the participant's body (“experimenter-applied”). Separate factor analyses of the sensory and emotional attributes for different body sites and modes of touch suggested approximately the same factorial structure in each case. Four general sensory factors emerged, labeled Lubricating, Textured, Silken, and Viscous, and two emotional factors, Comfortable and Arousing. These factors resembled those from equivalent work that used solid materials as stimuli, emphasizing that despite the differences in perceptual structure between fluid-coated and dry, solid surfaces, different body sites, and modes of touch influence the perception of fluid and dry stimuli similarly. As expected, fluids varied widely in how they scored on the factors. Site-wise differences were found, whereby stimuli assessed against the forearm were rated as more Lubricating, less Textured, more Silken, and more Comfortable than they were against the underarm. Self-applied touch was less Comfortable than experimenter-applied. The physical and perceptual were linked insofar as greater measured viscosity at low shear rates was associated with perceptions of cold and wet, whereas at high shear rates, greater viscosity was associated with greater perceived thickness.     

Effect of rock phosphate on soil properties and apparent phosphorus recovery in acid soil of Sumatra

The effects of rock phosphate (RP) on soil properties and apparent P recovery of corn in acid soil of Sumatra were investigated. The soil was dominated by kaolinitic minerals, very acid and low in extractable phosphorus. The experiment was conducted in two steps: incubation and greenhouse. The treatments were rock phosphate and triple superphosphate (TSP) at 0, 200, 400 and 600 µg P g^-1 for the incubation experiment, and at 0, 50, 100, 150 and 200 µg P g^-1 for greenhouse experiment In the incubation experiment, rock phosphate reduced exchangeable Al and increased pH_H2O better than TSP, and supplied Bray-1 extractable P as much as did TSP. In the greenhouse experiment, apparent P recovery values of rock phosphate were very close to those of TSP and the values tended to decrease at higher rates of P. Although corn yields of the rock phosphate treatment were lower than TSP, its relative agronomic effectiveness was quite high.