Images of the DNA double helix in water

The scanning tunneling microscope can image uncoated DNA submerged in water. The grooves of the double helix were clearly resolved in images of the 146-base pair fragment extracted from calf thymus nucleosome. In contrast to images obtained with dry DNA, the helix pitch varied only a small amount (36 +/- 5 angstroms). The path of the helix shows considerable variation. It is quite straight when the molecules are densely packed, but it curves and bends in isolated molecules.     

Protein-DNA interactions in vivo upstream of a cell cycle-regulated human H4 histone gene

Cell cycle-dependent histone genes are transcribed at a basal level throughout the cell cycle, with a three- to fivefold increase during early S phase. Protein-DNA interactions in the 5' promoter region of a cell cycle-regulated human H4 histone gene have been analyzed at single-nucleotide resolution in vivo. This region contains two sites, with four potential protein-binding domains, at which the DNA is protected from reaction with dimethyl sulfate in cells and from digestion with deoxyribonuclease I in nuclei. These protein-DNA interactions persist during all phases of the cell cycle and dissociate with 0.16 to 0.2M sodium chloride.     

Antiarthritic gold compounds effectively quench electronically excited singlet oxygen

Although certain gold [Au(I)] compounds have been used effectively in the treatment of rheumatoid arthritis for some years, the molecular basis for such therapeutic action has been unclear. One possible mechanism of the action of Au(I) compounds is that they protect unsaturated membrane lipids and proteins against oxidative degradation caused by activated phagocytes that are not properly regulated. In this study it has been shown that superoxide ion (O-2.), a product of activated phagocytes, can be oxidized to electronically excited singlet oxygen (O1(2)delta g), an agent that is capable of peroxidation of unsaturated fatty acid derivatives. It has also been shown that antiarthritic Au(I) compounds are effective deactivators of O1(2)delta g with quenching constants on the order of 10(7) M-1 sec-1.     

Expression and properties of two types of protein kinase C: alternative splicing from a single gene

Two complementary DNA's, encoding the complete sequences of 671 and 673 amino acids for subspecies of rat brain protein kinase C, were expressed in COS 7 cells. The complementary DNA sequence analysis predicted that the two enzymes are derived from different ways of splicing and differ from each other only in the short ranges of their carboxyl-terminal regions. Both enzymes showed typical characteristics of protein kinase C that responded to Ca2+, phospholipid, and diacylglycerol. The enzymes showed practically identical physical and kinetic properties and were indistinguishable from one of the several subspecies of protein kinase C that occurs in rat brain but not in untransfected COS 7 cells. Partial analysis of the genomic structure confirmed that these two subspecies of protein kinase C resulted indeed from alternative splicing of a single gene.     

Autoimmune glomerulonephritis induced in sheep by injections of human lung and Freund's adjuvant

Sheep immunized with human lung and Freund's adjuvant develop progressive glomerulonephritis with deposition of autoantibodies and complement in the glomerular basement membrane. This nephritis appears to be the first autoimmune disease induced by antigens that are not organspecific. By clinical and immunopathologic criteria, this nephritis appears identical to the nephritis induced in sheep by human glomerular basement membrane and greatly resembles certain nephritides of man, in particular, the nephritis in Goodpasture's disease.     

环境低温对肉鸡肺小动脉壁c-jun mRNA表达的影响

研究环境低温诱发肉鸡肺动脉高压综合征(PHS)过程中肺小动脉壁c-junmRNA的表达变化,从而确定原癌基因c-jun在环境低温诱发肉鸡PHS过程中的参与作用,为肉鸡PHS发生机制的研究提供基础。160只雄性AA商品代肉鸡15日龄随机分为对照组(22±1.5)℃和低温组(11±2)℃。15~50日龄,每周每组随机取6只,做肺组织石蜡切片,应用原位杂交染色法进行c-junmRNA杂交,并结合图像分析法,测定对照组与低温组肉鸡肺小动脉壁原癌基因c-junmRNA的表达情况。1)低温组肉鸡PHS发生率(18.75%)极显著高于对照组(1.25%)(P<0.01);2)低温组肉鸡肺小动脉壁c-junmRNA的表达从22日龄开始较对照组明显增加(P<0.05),从29~50日龄较对照组极显著升高(P<0.01)。说明环境低温明显诱发了肉鸡肺小动脉壁c-junmRNA的表达,且c-junmR-NA的表达参与了环境低温诱发的肉鸡PHS的发生。     

Spherical bilayer vesicles of fullerene-based surfactants in water: a laser light scattering study

The low solubility of fullerenes in aqueous solution limits their applications in biology. By appropriate substitution, the fullerenes can be transformed into stabilized anions that are water soluble and can form large aggregated structures. A laser light scattering study of the association behavior of the potassium salt of pentaphenyl fullerene (Ph5C60K) in water revealed that the hydrocarbon anions Ph5C60- associate into bilayers, forming stable spherical vesicles with an average hydrodynamic radius and a radius of gyration of about 17 nanometers at a very low critical aggregation concentration of less than 10(-7) moles per liter. The average aggregation number of associated particles in these large spherical vesicles is about 1.2 x 10(4).