分子马达的研究进展

本文对国内外分子马达的研究现状进行综述。并以生物中的关键酶ATP水解酶类(F0 F1 ATPase)为例 ,对其运动特点进行较详尽的描述 ,它是一类做圆周运动的旋转马达。同时还讨论了一些做直线运动的分子马达 ,如肌球蛋白 ,驱动蛋白等。并对分子马达的运动机理提出一些相应的观点 ,对分子马达的应用进行了展

五配位磷化合物与生物化学

综述了五配位磷化合物与生物化学的关系,发现当α-氨基酸的氨基接上磷酰基团以后,化学性质发生了许多奇特的现象,在室温下可发生自身活化现象而成肽、成酯、磷上酯交换及N→O磷酰基转位;丝氨酸和苏氨酸与核苷缀合以后,在弱碱性条件下能够对不同的碱基进行识别;磷酰化组氨酸和丝组二肽可以在中性条件下切割核酸、蛋白、酯.发现上述现象的发生都经历了一个五配位磷中间体,认为五配位磷中间体是决定它们活性的结构因素

Effects of tannic acid on salt ion availability of saline-alkali soils in the Yellow River Delta

In soil, plant polyphenolics can affect nutrient dynamics and mobility of metals, but their role in saline-alkali soil is largely unknown. The present study aimed to understand the effects of polyphenolics on the salt ion content of Tamarix chinensis community and bare land soils in the Yellow River Delta. The effect of polyphenolics on salt ion availability in saline and alkaline soil was determined by selecting the native T. chinensis community and bare land soils as low and high salt content soils, respectively. Different concentrations of tannic acid (TA) were added to the soils, and then their salt ion composition and contents were analyzed. Differences in the cation and anion contents and ratios among different treatments were analyzed using analysis of variance and multiple comparisons. Correlation analysis was also used to determine the relationships among different salt ions in the soils having varied salt content. The results showed that TA strongly increased the extraction of salt ions, K~+, Ca~(2+), HCO_3~-, and Cl~-, from soils with high salt level and SO_4~(2-) from soils with low salt level; nevertheless, Na~+, Mg~(2+), and Cl~- concentrations in soils with low salt level and SO_4~(2-) concentration in soils with high salt level first increased and then decreased with increasing TA concentration. The Na~+/K~+, Na~+/Ca~(2+), Ca~(2+)/K~+, Mg~(2+)/K~+, Cl~-/HCO_3~-, SO_4~(2-)/HCO_3~-, and Cl~-/SO_4~(2-) in soils of low salt levels decreased with increasing TA, but Na`+/Mg~(2+), Ca~(2+)/Mg~(2+), and Cl~-/SO_4~(2-) in soils of high salt levels increased continuously. In soils of high salt level, TA had no effect on Na+, but had a significant effect on other salt ions. The relationships between SO_4~(2-) and K~+, Na~+, Mg~(2+), and HCO_3~- were contradictory in low and high salt content soils. However, the correlations among other salt ions were consistent in soils having different salt contents. The results indicated that TA led to the disassociation of salt ions from exchange sites in soils and facilitated the leaching of salt from the saline-alkali soils. Therefore, TA could be used as a soil amendment to ameliorate saline-alkali soil. However, the amount of TA needs to be appropriate to accelerate the leaching of Na+ and avoid the erosion of Ca~(2+) and K~+

世界上最小的马达——分子马达

世界上最小的马达在哪里?就在我们每个人的身体里,它被称为"分子马达"(molecular motor)。分子马达是生物体内的一类蛋白质,就像传统的马达一样,它们"燃烧"燃料,做出特定的运动,完成特定的功能。它们是生物体内的"化学能与机械能之间的转换器"。某些分子马达也有定子、转子,只不过它们的尺寸都非常小,以纳米为单位,所以被称为世界上最小的马达。 "生命在于运动",这对于分子马达来说最确切

黄河三角洲柽柳植株周围土壤盐分离子的分布

为探讨柽柳的盐分富集效应及其对不同盐分离子分布的影响,以黄河三角洲盐碱地柽柳为研究对象,分析了离植株不同距离不同土层中的盐分离子组成、含量、离子比及不同离子之间的相关性。研究结果表明:各土层阳离子中Na^+含量最高,其次是Ca^2+和Mg^2+,K+最低,Cl^-在阴离子中的含量最高,(SO_4)^2-次之,(HCO_3)^-最低,而未检测到(CO_3)^2-。在柽柳植株周围,尤其是表层土壤中,离植株越近盐分含量越高,显示出柽柳对盐分的富集效应,其中对不同阳离子的富集程度表现为K^+>Na^+>Mg^2+>Ca^2+,而对阴离子的富集程度表现为(HCO_3)^->Cl^..

Distribution of soil salt ions around Tamarix chinensis individuals in the Yellow River Delta

为探讨柽柳的盐分富集效应及其对不同盐分离子分布的影响,以黄河三角洲盐碱地柽柳为研究对象,分析了离植株不同距离不同土层中的盐分离子组成、含量、离子比及不同离子之间的相关性。研究结果表明:各土层阳离子中Na^+含量最高,其次是Ca^2+和Mg^2+,K+最低,Cl^-在阴离子中的含量最高,(SO_4)^2-次之,(HCO_3)^-最低,而未检测到(CO_3)^2-。在柽柳植株周围,尤其是表层土壤中,离植株越近盐分含量越高,显示出柽柳对盐分的富集效应,其中对不同阳离子的富集程度表现为K^+&gt;Na^+&gt;Mg^2+&gt;Ca^2+,而对阴离子的富集程度表现为(HCO_3)^-&gt;Cl^...</p

Penta-coordinate phosphorous compounds and biochemistry

The relationship between penta-coordinate phosphorus compounds and biochemistry is briefly reviewed. Some interesting phenomena such as peptide formation, ester formation, ester exchange on phosphorus and N to O migration occur at room temperature when the amino group of amino acid is associated with phosphoryl group. Serine or threonine in conjugate of nucleoside-amino acid could recognize different nucleobases. N-phosphoryl Histine and Ser-His dipeptide could cleavage nucleic acid, protein and ester in neutral medium. It is found that the above phenomena all undergo penta-coordinate intermediate of phosphorus atom, which is proposed as the key factor to determine their activities

东天山圪塔山口镁铁-超镁铁质岩体地球化学、锆石U-Pb年代学及其对Ni-Cu成矿的指示/Geochemistry and zircon U-Pb geochronology of Getashankou mafic-ultramafic intrusions, eastern Tianshan, and its implication for Ni-Cu mineralization[J]

新疆新近发现的圪塔山口镍铜硫化物矿床位于东天山康古尔-黄山镍铜硫化物成矿带的东端.矿区包含4个镁铁-超镁铁质岩体,其中Ⅰ、Ⅱ、Ⅲ号岩体均见镍铜硫化物矿化.本文利用SIMS锆石U-Pb法测得Ⅰ号矿化岩体辉长岩年龄为282.6±1.9Ma,不仅与东天山地区其它含Ni-Cu矿化的镁铁-超镁铁质岩体形成时代一致,而且与塔里木玄武岩、镁铁质岩墙及北山地区的镁铁-超镁铁质岩体形成时限相一致.其形成可能与造山后伸展背景下的地幔柱叠加作用有关.地球化学数据表明圪塔山口岩体具有高Mg特征,除2个辉长岩样品m/f值较低外,其余14个样品集中于2.73～ 5.05之间,属铁质超基性岩.岩石稀土元素配分模式为右倾式,轻、重稀土比2.64～3.39;含长角闪辉橄岩及部分含长角闪橄辉岩和含长橄辉岩δEu具正异常,可能与这3个岩相中存在斜长石的结晶有关.微量元素蛛网图表明岩石富集大离子亲石元素Cs、Rb、Ba、K、Sr,富集高场强元素U、Pb,亏损高场强元素Th、Nb等特征.主量元素SiO2-(Na2O +K2O)与(FeOT/MgO)-FeOT图解、微量元素相关图及微量元素比值相关图说明圪塔山口岩体成岩物质为来源于亏损地幔的钙碱性玄武质岩浆,成岩作用以岩浆结晶分异为主导,并受到地壳的混染作用,具有较好的镍铜硫化物矿床成矿潜力

东天山圪塔山口铜镍矿区镁铁-超镁铁质岩体橄榄石与尖晶石矿物学特征/Mineralogical Characteristics of Olivine and Spinel for Getashankou Cu-Ni-Bearing Mafic-Ultramafic Intrusions in Eastern Tianshan, NW China[J]

新近发现的圪塔山口含铜镍矿化镁铁-超镁铁质岩体位于新疆东天山黄山-镜儿泉铜镍矿带东端,共有4个镁铁-超镁铁质岩体,其中Ⅰ、Ⅱ、Ⅲ号岩体均见铜镍硫化物矿化,研究表明其形成时代(282Ma)及岩浆来源与东天山地区其它铜镍矿化镁铁-超镁铁质岩体一致.本文对主要造岩矿物橄榄石及副矿物尖晶石进行了显微镜下观察及电子探针分析,结果表明橄榄石Fo值介于83.1～ 86.6之间,平均85.2,为贵橄榄石,其Ni含量变化于1273×10-6～ 2719 × 10-6,平均1918×10 6;尖晶石根据铝含量的不同可以分为高铝和低铝两种.圪塔山口岩浆为地幔源区发生15.8％ ～18.8％的部分熔融,并有过剩橄榄石加入的玄武质岩浆经结晶分异作用形成的派生岩浆.对橄榄石分离结晶和硫化物熔离的计算模拟表明橄榄石结晶前,岩浆已经达到S饱和,结晶过程始终伴随硫化物的熔离作用,虽然早期结晶的橄榄石与硫化物熔体间发生了Fe-Ni交换,但仍有很好的铜镍成矿潜力