Determination of size and shape of micelles by gel filtration chromatography

Summary The size and shape of a series of nonionic surfactants (polyoxyethylene nonyl phenols with number of ethyleneoxide groups 10, 13 and 18) were determined by gel filtration chromatography. TheStokes radius (R) was determined from the retention time. The hydration of micelles was estimated from the frictional ratios. The number of hydrating water molecules per oxyethylene unit was found to be 3–5, which agrees with the results reported by other investigators using other methods. It is thus shown that gel filtration chromatography can be applied to the micellar systems.

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Zusammenfassung Größe und Gestalt einer Serie von nichtionischen oberfldchenaktiven Substanzen (Polyoxydthylennonylphenolen mit 10, 13 und 18 Äthylenoxydgrappen) wurde mit Gelfiltrationschromatographie bestimmt. DerStokes-Radius wurde mit Hilfe der Rückhaltezeit bestimmt. Die Hydratation der Mizellen aus den Reibungszahlen geschdtzt, Zahl der Hydratwassermoleküle pro Oxydthylen ist 3–5, übereinstimmend mit Angaben anderer Autoren nach anderen Methoden. Damit ist die Anwendbarkeit der Gelfiltrationschromatographie auf mizellare Systeme erwiesen.

     

Donnan equilibria in microbial cell walls: a pH-homeostatic mechanism in alkaliphiles

A pH-homeostatic mechanism for alkaliphilic bacteria has been proposed taking the important role of anionic polymer layer in their cell walls into account. Donnan equilibria in the bacterial cell walls were calculated to estimate the pH values inside the polymer layer of the cell walls when the outer aqueous solution is in alkaline nature. The fixed charge concentration in the polymer layer was estimated to be 2–5 mol/l from the data reported for Gram-positive bacteria, particularly for an alkaliphilic bacterium Bacillus halodurans C-125. The salt concentrations of near isotonic conditions were taken as the outer aqueous solutions. The pH values calculated for the inside of the polymer layer (the cell wall) were smaller than those of the outer solution by 1–1.5 pH units. This result agrees well with the expected values estimated from the stability of cell membranes.     

Determination of the net electric charge of a polyacrylamide molecule by Donnan potential measurements

The net electric chargez _pof a polyacrylamide molecule (Praestol, Mol. Wt. 3.4×10⁶) in aqueous solution was determined for two pH values (7.2 and 10.0) by measuring the Donnan e.m.f. as function of the solutions NaCl contentc (2.7 mM<c<74 mM). Taking into account a non-ideal behavior of the counterions (Na⁺) mobility, the numerical values ofz _pturned out to be 3100 and 5500 electric charge units for pH=7.2 and 10.0, respectively. A measurable contribution of the assumed non-ideal model for the Na⁺ ions is found forc<15 mM.     

Purification of enzymes by high-speed gel filtration on TSK-GEL SW columns

The purification of enzymes was investigated by high-speed gel filtration on TSK-GEL G3000SWG columns packed with porous silica gel deactivated by chemically bonded hydrophilic compounds. Crude β-galactosidase from bacterial cells and commercial urease were purified ca. 15-fold in a single gel filtration. These enzymes were eluted within an hour from the column and the recoveries of enzymatic activity were almost 100% although the operation was carried out at room temperature (22°). Samples up to 100 mg could be applied to the column without loss of separation efficiency.     

Separation of oligogalacturonic acids by high-performance gel filtration chromatography on silica gel with diol radical.

Oligogalacturonic acids (OLGAs) ranging from two to nineteen residues in length were separated using high-performance gel filtration chromatography on a silica gel with diol radical. The optimum conditions (eluent, column temperature) for separation of OLGAs by high-performance gel filtration chromatography were investigated. The column used in this experiment allowed a high pressure of 4900 p.s.i. and a flow-rate of 2 ml/min. The stationary phase of silica gel stabilized the separation of OLGAs. The peaks of OLGAs separated using this column were assigned by comparing retention times with standards, and the molecular weights of the corresponding OLGAs were determined by fast atom bombardment mass spectrometry.