A model for the tertiary structure of transfer ribonucleic acids

In view of the possible changes of the structure of DNA at different relative humidities, a similar model for tRNA is proposed. In the native form, the sugar phosphate backbone folds repeatedly on itself resulting in a circular rod structure of about 50 Å in length and about 25 Å in diameter. Both the amino-acyl end and the anticodon site are surrounded by segments of base sequences common to different tRNA’s.     

Periodic conformations of deoxyribonucleic acids

The conformation of a deoxyribonucleotide unit in a deoxyribonucleic acid molecule can be defined by six angles, each of which specifies the relative orientations between two groups of atoms adjacent to a covalent bond. With the assumption that these atoms are hard spheres with fixed van der Waal radii, conformations are sought to minimize their overlapping. The additional requirement of the polymer having a periodic structure further reduces the allowable conformations.     

高胆固醇高脂肪膳食对家兔β-VLDL组成及其与巨噬细胞相互作用的影响的初步研究

给家兔喂以1％胆固醇及10％菜油(A组)或猪油(B组)50多天后A组血胆固醇水平(824.2±265.1mg/dl)明显低于B组(1666±693.8mg/dl);A组甘油三酯水平(51.9±19.1mg/dl)亦低于B组(104±40.2mg/dl)。二组家兔的β—VLDL的脂类组成无差别,但A组β—VLDL的apoE高于B组,分别为45.2％及37.5％。高分子量apoB(apoB_h)为33.6％,低于B组β-VLDL(47.3％)。A组β-VLDL促进小鼠腹腔巨噬细胞胆固醇堆积的程度大于B组,可能与apoE含量高有关。我们认为多不饱和脂酸减轻动脉粥样硬化(As)的作用不在于改变脂蛋白构成后阻碍泡沫细胞的形成而是促进β—VLDL从体内清除。     

Synteny on mouse chromosome 5 of homologs for human DNA loci linked to the Huntington disease gene

Comparative mapping in man and mouse has revealed frequent conservation of chromosomal segments, offering a potential approach to human disease genes via their murine homologs. Using DNA markers near the Huntington disease gene on the short arm of chromosome 4, we defined a conserved linkage group on mouse chromosome 5. Linkage analyses using recombinant inbred strains, a standard outcross, and an interspecific backcross were used to assign homologs for five human loci, D4S43, D4S62, QDPR, D4S76, and D4S80, to chromosome 5 and to determine their relationships with previously mapped markers for this autosome. The relative order of the conserved loci was preserved in a linkage group that spanned 13% recombination in the interspecific backcross analysis. The most proximal of the conserved markers on the mouse map, D4S43h, showed no recombination with Emv-1, an endogenous ecotropic virus, in 84 outcross progeny and 19 recombinant inbred strains. Hx, a dominant mutation that causes deformities in limb development, maps approximately 2 cM proximal to Emv-1. Since the human D4S43 locus is less than 1 cM proximal to HD near the telomere of chromosome 4, the murine counterpart of the HD gene might lie between Hx and Emv-1 or D4S43h. Cloning of the region between these markers could generate new probes for conserved human sequences in the vicinity of the HD gene or possibly candidates for the murine counterpart of this human disease locus.     

A polymerase chain reaction-based method for isolation of gene-specific sequences from the interferon-alpha gene cluster.

The interferon-alpha gene is a gene family of over 20 distinct genes having 80-95% homology with one another at a nucleotide level. Because of the high homology in the gene cluster, the available interferon-alpha gene probes can hybridize to multiple bands of different size on Southern blot analysis of restricted human genomic DNA. We used the polymerase chain reaction with the primers synthesized from Alu repetitive sequence and the conserved sequences of the interferon-alpha gene cluster to generate specific probes for individual interferon-alpha genes. The amplification products were subcloned into a plasmid vector and analyzed by DNA sequencing and Southern blotting of the restricted human placental DNA. One clone, which derived from interferon-alpha 14 gene, produced a single 5.2-kb band in Southern blots of the HindIII-restricted human placental DNA. This stands in contrast to the 10 bands of different size that were detected with a cDNA for the interferon-alpha I' gene. Our results indicate that a polymerase chain reaction-based method can be used to isolate gene-specific sequences from the interferon-alpha gene cluster. Since a variety of human cancers has been found to have the complete or partial deletion of the interferon-alpha gene cluster, the gene-specific probe generated by this method may aid in determining the breakpoints in the vicinity of the gene cluster.     

Variability of entrainment of cohesive sediments in freshwater

Estimates of sediment entrainment are required for models of particle transport in lakes and estuaries but are difficult to make because of the multiplicity of factors affecting cohesiveness of surficial sediments. We present results of sediment resuspension studies performed in an annular flume calibrated with laser-Doppler velocimetry. In our experiments, using sediments collected from two sites in the R. Raisin which flows into L. Erie and from one site in the western basin of L. Erie near the mouth of the R. Raisin, we applied shear stresses at the sediment-water interface in steps from 2 to 12 dyne/cm². Percent water content at the surface of the sediments was either 77 or 74%, and trials were run with and without oxygenating the water overlying the sediments. Entrainment rates as a function of shear stress at the sediment-water interface were best described by a power-law relationship. All but 14% of the variability in the power law expression was due to shear stress and percent water content; the variability not accounted for was due to differences in particle size distributions, chemical properties, and biological activity in the sediments.