Effect of salts on C-phycocyanin

The effect of a number of inorganic anions on the quaternary structure of C-phycocyanin has been investigated by fluorescence polarization. Dissociation to monomer occurred in the order: SCN⁻ > ClO₄⁻ > NO₃⁻ > Br⁻ > Cl⁻. These results suggest that hydrophobic interactions are important in the hexamer-monomer equilibrium of C-phycocyanin.     

Charge effects in the sedimentation of polyelectrolytes

The theory for sedimentation of macromolecular polyelectrolytes in solutions of low-ionic strength has been modified for the case of a supporting low molecular weight electrolyte possessing a partial specific volume close to unity. The final equations simplify greatly, allowing sedimentation data to be plotted in a linear fashion. These data then may be readily extrapolated to infinite dilution, yielding a value, S^o, simply related to size and shape. From the initial slope of such plots, the net charge on the macro-molecular polyelectrolyte may be determined. It is suggested that tetramethyl-ammonium chloride may prove to be a satisfactory supporting electrolyte for such studies.     

Reductive alkylation of ribosomes as a probe to the topography of ribosomal proteins

Escherichia coli ribosomes were treated with a number of different aldehydes of various sizes in the presence of NaBH(4). After incorporation of either (3)H or (14)C, the ribosomal proteins were separated by two-dimensional polyacrylamide-gel electrophoresis and the extent of alkylation of the lysine residues in each protein was measured. The same pattern of alkylation was observed with the four reagents used, namely formaldehyde, acetone, benzaldehyde and 3,4,5-trimethoxybenzaldehyde. Every protein in 30S and 50S subunits was modified, although there was considerable variation in the degree of alkylation of individual proteins. A topographical classification of ribosomal proteins is presented, based on the degree of exposure of lysine residues. The data indicate that every protein of the ribosome has at least one lysine residue exposed at or near the surface of the ribonucleo-protein complex.     

Inhibition of enzymes by metal ion-chelating reagents. Theory and new graphical methods of study

1. The mechanism of inhibition of enzymes by metal ion-chelating reagents is discussed and equations derived. 2. Two distinct mechanisms are postulated and graphical methods are given for differentiating between them. 3. Where the metal ion is actually removed from the enzyme to form a co-ordination complex in solution, a procedure is described for obtaining the stability constant for metal-enzyme interaction, the number of metal ions involved and the stoicheiometry of metal ion-ligand interaction.     

Alkaline phosphatase of Drosophila melanogaster. II. Biochemical comparison among four allelic forms

Biochemical analyses of partially purified preparations of APH-4 and -6 (common allelic forms) and APH-2 and -10 (rare allelic forms) of D. melanogaster reveal that the two common forms are similar in all properties investigated except for pH optimum (8.0 vs. 8.5). The common and rare forms share certain properties in common but differ in that the common forms are more stable to heat and more sensitive to inhibition by inorganic phosphate. With respect to such properties as substrate preferences and K _i values for inorganic phosphate, the common forms and APH-2 are similar to one another, whereas APH-10 is distinctly different. All four activities show preference for a phosphoaromatic compound as substrate, with O-phosphotyrosine being the best substrate of biological origin. Transphosphorylation, as related to these allelic forms of APH, is discussed.Paper No. 3892 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina. This study was supported by Atomic Energy Commission Contract AT-(40-1-)-3980.     

Effect of Gibberellic Acid on the Elongation Rate of Agrostis alba Root Hairs

The influence of gibberellic acid over a wide range of concentrations on the rate of elongation of root hairs of redtop grass was investigated. The rate of root hair elongation was increased by GA over the concentration range of 10^?7 to 10^?12 M inclusive, with peak stimulation occurring at 10^?6 M. Although root hair growth was slightly accelerated by 10^?6 M GA, this concentration damaged many root hairs and caused some to stop growing altogether. Rate of root hair elongation was reduced to less than 84% of the control by 10^?5 M GA.