Harvesting of Algae by Froth Flotation

A highly efficient froth flotation procedure has been developed for harvesting algae from dilute suspensions. The method does not depend upon the addition of flotants. Harvesting is carried out in a long column containing the feed solution which is aerated from below. A stable column of foam is produced and harvested from a side arm near the top of the column.

The cell concentration of the harvest is a function of pH, aeration rate, aerator porosity, feed concentration, and height of foam in the harvesting column. The economic aspects of this process seem favorable for mass harvesting of algae for food or other purposes.

     

Production of a Pyrrole Antibiotic by a Marine Bacterium

Evidence is presented for the isolation and identification of bacteria able to synthesize an unusual antibiotic containing five bromine atoms per molecule. The identification and taxonomic position of these bacteria was made by use of a computer in conjunction with traditional methods. These microorganisms and closely related strains have been isolated on various occasions from tropical water in the vicinity of Puerto Rico. One bacterium, a pseudomonad, has been given the name Pseudomonas bromoutilis because of its distinctive capability. The antibiotic has been extracted, purified, and obtained in crystal form, and its structure has been determined. Although clinical tests of its properties were not encouraging, it may be of significant value and interest from an ecological standpoint.     

Studies on the Bohr Effect of Sheep Hemoglobin

A simple method is described for the measurement of pH changes in hemoglobin solutions on oxygenation and reduction. Data are presented establishing the absence of a Bohr effect in p-chloromercuribenzoate [PCMB] treated hemoglobin. The influence of a number of sulfhydryl inhibitors on the Bohr effect of a hemoglobin solution is reported and an interpretation based on steric factors in the protein is proposed.     

Studies on the Hemolytic Properties of Protamine

The basic protein protamine causes a rapid hemolysis when incubated with the red blood cells of many mammalian species. The age of the cells does not affect the process. Neutralization of the active side groups of the protamine molecule with formalinization demonstrates that a specific degree of charge is necessary for hemolysis, as more than 30 per cent of the guanidine groups must remain unreacted to maintain activity. Unlike the hemolysis induced by the synthetic polypeptides polylysine and polyhomoarginine, protamine hemolysis is temperature-dependent. Whole lipoprotein material derived from red blood cell membranes inhibits protamine hemolysis to a greater extent than do the membranes themselves, serum, serum protein fractions, or cholesterol. The phosphatide and protein moieties derived from the membranes are quite avid in inhibiting protamine hemolysis. A probable explanation is that intracellular aggregation of these structural elements may cause changes in electrostatic charge and surface tension which result in increased permeability. The hemolytic and antitumor cell properties of protamine could not be segregated from its animal toxicity. Despite formalinization to a degree which eliminated the former, the compound remained quite toxic to mice and rabbits.     

Structure of 11-deoxydaunomycin bound to DNA containing a phosphorothioate

The anthracyclines form an important family of cancer chemotherapeutic agents with a strong dependence of clinical properties on minor differences in chemical structure. We describe the X-ray crystallographic solution of the three-dimensional structure of the anthracycline 11-deoxydaunomycin plus d(CGTsACG). In this complex, two drug molecules bind to each hexamer duplex. Both the drug and the DNA are covalently modified in this complex in contrast with the three previously reported DNA-anthracycline complexes. In the 11-deoxydaunomycin complex the 11 hydroxyl group is absent and a phosphate oxygen at the TpA step has been replaced by a sulfur atom leading to a phosphorothioate with absolute stereochemistry R. Surprisingly, removal of a hydroxyl group from the 11 position does not alter the relative orientation of the intercalated chromophore. However, it appears that the phosphorothioate modification influenced the crystallization and caused the 11-deoxydaunomycin-d(CGTsACG) complex to crystallize into a different lattice (space group P2) with different lattice contacts and packing forces than the non-phosphorothioated DNA-anthracycline complexes (space group P4(1)2(1)2). In the minor groove of the DNA, the unexpected position of the amino-sugar of 11-deoxydaunomycin supports the hypothesis that in solution the position of the amino sugar is dynamic.     

Indexes to the reassociation and stability of solution DNA hybrids

Summary The computation, assumptions, and properties of DNA-hybrid stability and reassociation indexes were reviewed. Different methods of computing the same index typically yielded similar values. However, because dissociation curves change from asymmetric to symmetric as increasingly divergent DNAs are compared, adequate determination of mode required fitting a complex function. Delta Tm, delta mode, and delta T50H correlated well up to ca. 12, and all were found to be useful indexes of genomic similarity in that range. They also exhibited similar levels of error, even though T50H comprises a percent reassociation component with relatively large variance. At greater distances, the delta Tm scale became markedly compressed because of the boundary imposed by the temperature of hybrid formation (incubation temperature). Though not compressed or technically limited by it, delta mode and delta T50H could not be extrapolated with certainty below the incubation temperature. Among theoretical problems discussed: Tm and mode index an increasingly small percentage of the genome as the extent of reassociation decreases, and they may compare different genomic segments as DNAs become highly diverged. T50H relies upon the assumptions that all sequences evolve at a constant rate and that reassociation behavior is the same among all sequences regardless of their extent of divergence. Tm and T50H may be biased by selfhybridization of repetitive elements or cross-hybridization of paralogous sequences. Delta mode is free of such biases as long as the genomes under comparison are not too diverged. No index was found to be best in all circumstances.     

Cell-specific fatty acylation of proteins in cultured cells of neuronal and glial origin

Distinct sets of cellular proteins were labeled with [³H]myristic and [³H]palmitic acids in primary (rat neurons and astroglia) and continuous (murine N1E-115 neuroblastoma and rat C6 glioma) cell cultures derived from the nervous system. Both soluble and membrane proteins were modified by myristate in a hydroxylamine-stable (amide) linkage, while palmitoylated proteins were esterlinked and almost exclusively membrane bound. Chain elongation of both labeled fatty acids prior to acylation was observed, but no protein amide-liked [³H]myristate originating from [³H]palmitate was detected. Fatty acylation profiles differed considerably among most of the cell lines, except for rat astroglial and glioma cells in which myristoylated proteins appeared to be almost identical based on SDS gel electrophoresis. An unidentified 47 kDa myristoylated protein was labeled to a significantly greater extent in astroglial than in glioma cells; the expression of this protein could be related to transformation or development in cells of glial origin.