Seibutsu Butsuri

Organization in Ionic Solutions: How and Why?

Norio Ise

1984 Volume 24 Issue 1 Pages 17-28
Published: January 25, 1984
Released on J-STAGE: January 07, 2010

DOIhttps://doi.org/10.2142/biophys.24.17

JOURNAL FREE ACCESS

Show abstractHide abstract

The small-angle X-ray scattering on dilute solutions of ionic polymers (such as synthetic polymers, proteins, polynucleotides, surfactant micelles, virus particles) shows a single, broad peak. The peak position depends on the molecular weight of polymer. When two fractions of different molecular weights are mixed, there appears one peak at position different from and inbetween the original peak positions of the mother fractions. This suggests positively that "ordering" which is responsible for the scattering peak, is not intra-, but inter-molecular. Thus, the ionic polymers are concluded to be distributed in a fairly regular way. The interparticle distance (2Dexp) estimated by the Bragg equation is found to be smaller than the theoretical distance (2Do) calculated from the polymer concentration, suggesting the presence of a Coulombic interparticle attraction. These experimental findings are confirmed by using Polymer latex particles of larger dimensions (diameter 1000-4000 Å). The ordering formation of the particles in dilute solutions and the vibrational motion of the particles in the ordered array are studied by a light microscope. The thermal motion of these particles is violent even in relatively high concentrations. Finally, the DLVO theory is critically discussed; when an imperfection of the theory is corrected, a Coulombic interparticle attraction is demonstrated to exist, as was found experimentally.

View full abstract

Download PDF (1628K)
On protein precipetant

Tsutomu ARAKAWA, Serge N. Timasheff

1984 Volume 24 Issue 1 Pages 29-39
Published: January 25, 1984
Released on J-STAGE: May 25, 2009

DOIhttps://doi.org/10.2142/biophys.24.29

JOURNAL FREE ACCESS

Show abstractHide abstract

Protein solubility is a function of such a factor as pH, ionic strength, temperature, presence or absence of additive (e.g. salt) and kind and concentration of the additive. Inorganic salts are known to affect the protein solubility in widely different manner. Certain salts, e.g. Na₂SO₄ and (NH₄)₂SO₄, and organic solvents such as acetone, alcohol and polyethylene glycol are frequently used to precipitate or crystallize proteins. To eluci- date the effect of such additives on the protein solubility, study on preferential interactions of proteins with solvent components in water/protein/additive system has been carried out. In this review, concept of the preferential interaction and thermodynamic analysis of the protein solubility on the basis of the preferential interaction are introduced. In addition, typical data of the preferential interaction measurements were summerized, showing a correlation between the protein solvent interaction and the effect of solvent additive on the protein solubility. The salting-out effects of certain salts, polyethylene glycol and hexylene glycol were interpreted in terms of the unfavorable interaction between proteins and theseadditives, favoring a state in which the interaction is reduced and therefore more contacts between protein molecules are formed. From the protein solvent interactions and the measurements of protein stability, it was pointed out that these additives are different in their effects on the protein stability.

View full abstract

Download PDF (957K)
[title in Japanese]

[in Japanese], [in Japanese], [in Japanese]

1984 Volume 24 Issue 1 Pages 40-44
Published: January 25, 1984
Released on J-STAGE: May 25, 2009

DOIhttps://doi.org/10.2142/biophys.24.40

JOURNAL FREE ACCESS

Download PDF (2120K)

Register with J-STAGE for free!