デオキシリボ核酸 (DNA) の孔中の拡散に及ぼす共存分子の影響

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An attempt was made to clarify the effect of coexisting substances on the diffusion coefficient D of a DNA molecule in a pore. The substances used were (1) DNA with different molecular weight, (2) inorganic electrolyte, (3) protein, and (4) protein with NaCl. The micro porous cuprammonium regenerated cellulose hollow fibers with various mean pore size of 10,15,35 and 75nm (PLANOVA in registered name) were used as a membrane. Calf thymus DNA and λ phage DNA were employed as a polydispersed DNA and monodispersed DNA, respectively. The tris-HCl buffer solution, NaCl aq. solution and CaCl_2 aq. solution were used as a medium containing an inorganic electrolyte. The γ-globulin from Bovine plasma was used as a protein. The D value and an apparent activation energy ΔHa of the diffusion for DNA molecules were evaluated through the stationary state method of the diffusion using our trial apparatus. The results are : (1) D increased with an increase in a width of molecular weight distribution. (2) Inorganic electrolyte worked on D value through the generation of the diffusion potential. (3) D increased with an increase in the mean pore size and when the size is larger than 35nm, ΔHa is less than 5kcal/mol, and when the size is 10nm, ΔHa is larger than 7.5kcal/mol. (4) The coexistence of γ-globulin made aggregates of DNA resulting in precipitation and the transportation of DNA molecule by this diffusion was prohibitted. The addition of NaCl gave the dissolution of the aggregates and DNA diffuse as a molecule. In the case of the membrane larger than 35nm in mean pore size, ΔHa value of the diffusion was 1.7kcal/mol. We conclude that the diffusion of a DNA molecule through the membrane with the mean pore size of less than 10nm is influenced strongly by the thermal molecular motion of the polymers which compose pores and conclude that when the pore size is more than 35nm a DNA molecule diffuses through a pore by a one dimensional brownian motion in water.
2000-02-25

デオキシリボ核酸 (DNA) の孔中の拡散に及ぼす共存分子の影響

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