A mathematical model is proposed for the elution of proteins on ion exchange columns by a linear gradient increase and stepwise increase of ionic strength in order to predict relationships between the elution characteristics (the peak position, the peak width, etc.) and the operating conditions (the flow rate, the slope of gradient, etc). This model is in principle based on the continuous-flow plate theory, in which the protein concentration and ionic strength dependent distibution coefficient between proteins and ion exchangers and zone sperading effects are taken into consideration. The advantage of this model is its simplicity since it requires only two parameters: The distribution coefficient and the number of plates. Since the distribution coefficient of proteins depends on both the protein concentration and ionic strength of the elution buffer, the number of plates should vary with time. However, it is extremely difficult to take into consideration the time-dependent number of plates. Therefore, we assume that the number of plates is constant and related to that number derived from a mass balance model which includes longitudinal dispersion and gel phase diffusion. On the basis of these assumptions, a method for determining the number of plates by the moment method is presented. Although the dependencies of the peak position and peak width on the slope of linear gradient are predictable by numerical calculations of the present model, simpler methods for prediction of these dependencies are desirable. A graphical method is proposed for prediction of the peak position. For prediction of the peak width, an asymptotic solution is derived from a quasi-steady-state model.

Etiolated pea seedlings (5 days old) were treated with red light for 5 min and grown for 2 days more in darkness. Effects of the red light on the mRNA levels of two subunits of ribulose-l,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) (ribulose-P2 carboxylase), rate of enzyme synthesis and accumulation of the enzyme were examined for the plants. Increases of the two mRNA levels, encoded in nuclei and chloroplasts were observed. Red light followed by far-red light treatment for 5 min inhibited the increases. An increase parallel with the mRNA levels was found for the rate of the enzyme synthesis and accumulation of the enzyme. These results indicate that the induction of two mRNA levels is mediated by phytochrome and causes the red-light-inducible, far-red-light-reversible increase of ribulose-P2 carboxylase. When white light was irradiated to induce the enzyme, the effects of red light given in darkness were reinforced. These results indicate that light-induction of ribulose-P2 carboxylase is mediated by phytochrome and controlled by the two mRNA levels.Ribulose-1,5-bisphosphate carboxylase/oxygenase (ribulose-P2 carboxylase) is a key enzyme in photosynthesis, and is localized in the chloroplast. This enzyme is composed of eight large and eight small subunits. The large subunit is encoded in chloroplast D N A [l] and synthesized on chloroplast ribosomes [2]. The small subunit is encoded in nuclear DNA [3] and synthesized on cytoplasmic ribosomes in the form of a precursor. The precursor is transported into chloroplasts and results in the small subunit after removal of an extra peptide during transportation [4-71. The large and the small subunits combine in the chloroplast to form ribulose-P2 carboxylase holoenzyme.Production of ribulose-Pz carboxylase is induced by light. We have previously shown that the light induction of the enzyme is pretranslationally controlled, and that the large and the small subunit mRNA levels seem to be coordinately regulated during light induction [8,9]. We want to know whether the pigment-protein phytochrome [lo] is involved in the photoresponses of the two mRNA levels. The present work shows that both the large and the small subunit mRNA levels of ribulose-P2 carboxylase are regulated by phytochrome.

jg-Galactosidases (EC 3.2.1.23) from Bacillus circulans were purified and separated into two different enzyme forms, using Sephadex G-150, ion-exchange, polybuffer chromatography, and preparative polyacrylamide gel electrophoresis. The molecular weights estimated for these two enzymes were 2.4x lO5 (jS-galactosidase-1) and 1.6x lO5 (/?-galactosidase-2). They showed similar isoelectric points of about 4.5 and the same optimum pH of 6.0, whereas they were considerably different in Km values, substrate specificity, and particularly oligosaccharideproducing activity./?-Galactosidase-2 produced many galacto-oligosaccharides, including di-, tri-, tetra-, and pentasaccharides, during hydrolysis of4.56% lactose. When 60% of the lactose was converted, the total amount of oligosaccharide production reached a maximum at which about 41% of the products formed were oligosaccharides. /?-Galactosidase-1 produced only 6%at its maximum.

No abstract

No abstract