. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 550 650 WAVELENGTH (nm) Figure 3. Visible absorption spectra of the three ink pigments. The solvent is sodium phosphate bufl'er, pH , with M sodium chloride. purity. The hydroxylapatite chromatography was per- formed as described previously (MacColl e! ai, 1981), and the B-phycoerythrin eluted prior to the other bilipro- teins. Purified protein was dialyzed into distilled water, lyophilized, and stored in a refrigerator. B-Phycoerythrin is composed of three subunits, « and ft (17,500 molecular weight) and y (30,000 m
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 550 650 WAVELENGTH (nm) Figure 3. Visible absorption spectra of the three ink pigments. The solvent is sodium phosphate bufl'er, pH , with M sodium chloride. purity. The hydroxylapatite chromatography was per- formed as described previously (MacColl e! ai, 1981), and the B-phycoerythrin eluted prior to the other bilipro- teins. Purified protein was dialyzed into distilled water, lyophilized, and stored in a refrigerator. B-Phycoerythrin is composed of three subunits, « and ft (17,500 molecular weight) and y (30,000 molecular weight). The subunits were dissociated in M urea, pH and separated on a Sephacryl S-200 (Pharmacia) col- umn in the same solvent. Fractions containing y subunit were identified spectroscopically on the basis of its char- acteristic phycourobilin absorbance at 490 nm. The y subunit has both phycourobilin and phycoerythrobilin chromophores while the « and ft subunit have only phy- coerythrobilins (see MacColl and Guard-Friar, 1987. for references). The fractions containing y subunit were then rechromatographed on the same column to complete their purification. C-Phycocyanin was isolated from the blue-green alga, Phormidium luridum, after treating the cells with the en- zyme lysozyme. The protein was purified by ammonium sulfate precipitation, first with 50% followed by 35% sat- urated ammonium sulfate. Purified protein was dialyzed into distilled water, lyophilized, and stored in a refriger- ator. C-Phycocyanin, which has only phycocyanobilin for chromophores, was refluxed in methanol overnight. The reflux mixture was filtered and the blue solution, con- taining phycocyanobilin, was evaporated to dryness. The absorption spectrum of the protein-free phycocyanobilin was obtained in acidic methanol. Absorption spectra were obtained at room temperature using a model 320 spec- trophotometer (Perkin-Elmer). Sodium dodecyl sulfate gel electrophoresis was per- formed u
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