Restrained molecular dynamics studies on complex of adriamycin with DNA hexamer sequence d-CGATCG

Adriamycin is an anthracycline anticancer drug used widely for solid tumors in spite of its adverse side effects. The solution structure of 2:1 adriamycin-d-(CGATCG)(2) complex has been studied by restrained molecular dynamics simulations. The restraint data set consists of several intramolecular and intermolecular nuclear Overhauser enhancement cross-peaks obtained from two-dimensional nuclear magnetic resonance spectroscopy data. The drug is found to intercalate between CG and GC base pairs at two d-CpG sites. The drug-DNA complex is stabilized via specific hydrogen bonding and van der Waal's interactions involving 4OCH(3), O5, 6OH, and NH(3)(+) moiety of daunosamine sugar, and rings A protons. The O-glycosidic bond C7-O7-C1'-C2' lies in the range 138 degrees -160 degrees during the course of simulations. The O6-H6...O5 hydrogen bond is stable while O11-H11...O12 hydrogen bond is not favored. The intercalating base pairs are buckled and minor groove is wider in the complex. The phosphate on one strand at intercalation site C1pG2 is in B(I) conformation and the phosphates directly lying on opposite strand is in B(II) conformation. The phosphorus on adjacent site G2pA3 is in B(II) conformation and hence a distinct pattern of B(I) and B(II) conformations is induced and stabilized. The role of various functional groups by which the molecular action is mediated has been discussed and correlated to the available biochemical evidence.     

Evolutionary and morphometric implications of morphological variation among flowers within an inflorescence: a case-study using European orchids

BACKGROUND AND AIMS: This study explores the previously largely ignored morphological variation that occurs among flowers within a single inflorescence. METHODS: Variation in four metric parameters (labellum length and width, spur length and width) that together strongly influence pollination frequency is documented within the simple racemose inflorescences of eight individuals that represent a primary hybrid and six species of European orchids. KEY RESULTS: Regression of each parameter against the location of each flower on the inflorescence, and calculation of correlation coefficients for each pair of parameters within each inflorescence, demonstrate significant decoupling of labellum and spur development, despite the fact that they are different portions of the same floral organ. Spur length and diameter are constant across inflorescences of Dactylorhiza other than the vestigial-spurred D. viridis, whereas in other genera spur length declines in parallel with labellum dimensions. These differences are likely to reflect selection pressures or developmental constraints. Strong negative deviations from the regression line for one or more parameters are evident in occasional flowers, occurring most frequently in the lowermost and uppermost one or two flowers, and so reflecting transitions in meristematic behaviour. Thus, population-level morphometric studies are best conducted on flowers taken from approximately the mid-point of the inflorescence. Moreover, in the two relatively large inflorescences where lower flowers were removed for measurement before the upper flowers had opened, labellum size increased significantly in the flowers immediately above the excisions, suggesting that excision liberated resources that were diverted into the opening buds. Repeat measurement of all flowers from one selected inflorescence demonstrated typical measurement errors of only +/- 30-80 micro m, irrespective of the size of the structure studied. If flowers are not mounted and measured immediately following excision, modest negative deviations of 30-50 micro m result from post-mounting shrinkage; this occurs less rapidly in the spur than in the thinner labellum, which should therefore be measured first. Variation in all four parameters among all the flowers of a single inflorescence is between 42 % and 107 % of that observed between a similar number of flowers sampled from a consistent location on different (but conspecific and coexisting) inflorescences. CONCLUSIONS: This result demonstrates the strong influence of epigenesis on flower morphology and further emphasizes the importance of (a) sampling from a consistent location within the inflorescences under comparison, (b) interpreting morphometric ordinations hierarchically, building from individuals to infraspecific taxa and species via populations, and (c) considering in any microevolutionary study the potentially profound effects of the cline in flower size within each inflorescence.     

内蒙古察哈尔丘陵啮齿动物种群数量的波动和演替

根据内蒙古自治区正镶白旗乌宁巴图苏木９７４－１９９３年随啮齿动物密度监测资料进行分析,得到如下结果。共捕啮齿动物１３种,其中达乌尔黄鼠为优势种（６７．８５％）、一趾鼠为次优势种（１０．１６％）,长爪沙鼠、布氏田鼠、达乌尔鼠兔为常见种,余为少见种。黄鼠密度与个体数呈正相关（Ｐ〈０．０００１）、五趾跳鼠与个体数、黄鼠密度呈负相关（Ｐ〈０．００１）。个体数与黄鼠、五趾跳鼠密度的回归模型为：（个体数）＝１     

Quantification and correlation of vesicular-arbuscular mycorrhizal propagules with soil properties of some mollisols of northern India

The populations of vesicular-arbuscular mycorrhizae (VAM) propagules by the most probable number method in some mollisols and their correlations with some important soil properties were determined. On average, the six soils, Phoolbagh clay loam, Beni silty clay loam, Haldi loam, Nagla loam, Khamia sandy loam and Patherchatta sandy loam contained 4.9, 4.0, 7.9, 7.9, 3.3 and 13.0 propagules/g soil, respectively, i.e. none of the soils was found to be high in VAM. The size of the VAM population was compared to soil properties such as pH, organic carbon, sand content, available phosphorus and available potassium, cation-exchange capacity, silt and clay contents. A significant positive correlation (r=0.586) was only found with available soil phosphorus (P<0.05) and a significant negative correlation (r=-0.555) with soil clay content (P<0.05).Directorate research paper series No. 7862     

湖北斧头湖湖滨湿地植物的联结与相关分析

利用２×２列联表法结合Ｘ２检验对湖北武昌斧头湖湖滨湿地植物进行了联结分析,计算了种间的相关系数并检验了种间相关显著性。结果表明这些种组构成了一个连续体。文中还讨论了各种组的生态意义。     

脑干内的混沌

对脑干听觉诱发电位进行了非线性动力学分析,计算了关联维数Ｄ２和最大Ｌｙａｐｕｎｏｖ特征指数,确认ＢＡＥＰ是一个来源于低维混沌动力系统的时间序列,从而证明人类脑干存在着混沌现象,利用满足最小互信息标准的最佳延迟重构了二维混沌吸引子。     

Analysis of vertical ozone and nitrogen oxides profiles in aPrunus cerasifera canopy

An automatic system was installed for continuous analyses of ozone, sulphur dioxide, nitrogen monoxide and nitrogen dioxide in an experimental orchard with a canopy ofPrunus cerasifera plants in summer 1993. Air samples from three elevations (0.8 m, 1.6 m and 3 m above ground) were sequentially analyzed. Ozone concentrations above the canopy were usually higher than within the canopy; their relationships with stomatal resistance have been investigated. Sulphur dioxide levels were negligible. Nitrogen oxides showed a complex profile, with no particular trend, likely due to a reciprocal exchange between the atmosphere and the ground surface.     

Comparative study of dynamic structure of pig and chicken aspartate aminotransferases by measuring the rotational correlation time

The rotational correlation time of two homologous cytoplasmic aspartate aminotransferase molecules isolated from pig and chicken hearts was obtained by spin-labeling technique. The maleimide and iodoacetamide spin-labels modyfying external SH-groups of a protein were used. In the interpretation of ESR spectra a rotational motion of nitroxide group relative to the protein molecule was taken into account. To determine the macromolecule rotational correlation time two methods of the immobilization of a protein molecule were used: 1) by means of increasing protein solution viscosity and 2) by fixation of the protein molecule on adsorbent. From comparison of experimental and theoretical values of rotational correlation time it was conclude that the both enzymes exhibits an intramolecular flexibility.     

Conformations and dynamics of surfactants in micelles and liquid crystals by nuclear magnetic relaxation

The order parameters as well as the rates of overall and internal motions of aggregated surfactants can be obtained from deuteron and carbon-13 nuclear relaxation experiments. The main contribution to the relaxation is generally the quadrupolar coupling (²H) or the short range dipolar interaction with protons (¹³C). In some cases it is convenient to derive the same information from the¹³C relaxation induced by long range dipolar interactions with a paramagnetic probe exchanging rapidly among the polar heads of surfactant molecules. This paper outlines the methods of interpretation of relaxation data by means of a rotational jump model of internal motions, taking into account most of the accessible conformers. The conformational and dynamical parameters are obtained from the magnetic field dependence of the longitudinal relaxation rates (micelles) or from the simultaneous fit of these rates and of the dipolar or quadrupolar splittings (liquid crystals). Some examples of application of these methods are given from recent works on single and double detailed surfactants.