デオキシペントース核蛋白の抽出・精製およびその化学的性状の研究

概要

論文の詳細を見る
The aim of the investigations reported in this paper is to shed the light on the chemical nature of deoxypentosenucleoproteins (DNP) composed of deoxyribonucleic acid (DNA) and basic protein such as protamine or histone. The descriptions of the experiments and discussions are divided into four sections. In the first section the processes of the analytical methods used in the studies are described. Some comments are given on the determination of nucleic acids with the use of colorimentic methods. In the second section the studies on the purification of DNPs are described. The DNPs purified were nucleoclupeine from herring soft roe, nucleosalmine from salmon soft roe, nucleoiridine from trout semen, and nucleohistones from calf thymus and from wheat germ. For the preparation of nucleoprotamine, sperm heads were collected and washed by centrifugation and extracted with strong saline. Nucleoprotamines were not extractable with distilled water. Calf thymus nucleohistone was extractable either with strong saline or with distilled water. Wheat germ nucleohistone was not extractable with distilled water but with 1.5 M saline. All DNPs were precipitated at the sodium chloride concentration from 0.14M to 0.5M. In the third section some investigations on the chemical nature of DNPs are described. First : the results of the chemical analysis on the DNPs with respect to their nitrogen, phosphorus, and nucleic acid content. Nucleoprotamines contained from 60 to 70 per cent of DNA, calf thymus nucleohistone 46 per cent, and wheat germ nucleohistone 36 per cent respectively. Near the ten per cent of wheat germ nucleohistone could not be extracted with acid. Second : the dissociation of DNP into DNA and protein in strong saline solution. This was tested in three experiments ; precipitation of DNA and non-precipitation of protein by the addition of ethanol into strong saline solution of DNP, dialysis and high speed centrifugation of strong saline solution of DNP. Third : the solubility of DNPs in saline of different strength. It was found from the solubility curves with respect to DNA and to protein that DNPs were generally soluble in strong saline. Considerable part of protein was salted out as the salt concentration was increased. When the concentration of salt was decreased to 0.5M-0.14M, DNPs were not soluble at all. Fresh preparations of calf thymus nucleohistone were soluble in distilled water to give viscous solution. By the addition of small amount of salt fibrous mass was settled out. From these experiments the nature of the chemical bond between DNA and protein was deduced to be electrostatic in nature which must be weakened in the presence of high concentration of salt and strengthened as the salt concentration was reduced. In the latter case the recombination will be occur which results in the neutralization of the charged groups. And the solubility decreaced greatly as the result of complex formation. This will provoke the formation of fibrous precipitate. In the fourth section the studies on the interaction between DNA and basic proteins in 0.14M saline and in distilled water are described. When DNA and basic protein were mixed in 0.14M saline artificial DNA-protein complex was precipitated. This precipitation was found to be affected by several factors: concentration of both components, mixing ratio (protein: DNA), pH, and state of DNA. The shapeof the curves, which show the amount and the composition of the precipitate formed, varied by the kind of basic protein used. The susceptiblity of the DNA-protein complex of varing composition to the deoxyribronuclease (DNase) action was also studied. It was found that the susceptibility was decreased as the protein to DNA ratio was increased. In this case, also, the susceptibility was dependent on the kind of proten used. Protamine was most inhibitory and argine rich histone was least. The interaction between DNA and basic protein in solution was studied in distilled water. The intensity of the ultraviolet light absorption of the mixture was increased above the sum of the both components. From the shape of absorption spectra this increase was thought to be the result of the the scattering light of the mixture. This was ascertained by light scattering experiments. Even the transparent mixture showed high extent of light scattering effect. From these experiments it was supposed that in distilled water DNA and basic protein interact to form some structure, the nature of which is still obscure. In this phenomenon the difference between basic proteins was apparent. From the investigations described above it will be concluded that DNA and basic protein interact in weak salt medium or in distilled water and the bonds between these components are electrostatic in nature. And the nature of the DNPs is seemed to be dependent, at least in part, on the kind of the protein conjugated.
宇宙航空研究開発機構の論文
1957-12-24

著者

鈴木〓之
東京大学理工学研究所

デオキシペントース核蛋白の抽出・精製およびその化学的性状の研究

スポンサーリンク

概要

著者

関連論文

スポンサーリンク