alpha-Amylase adsorption on starch crystallites

The goal of this work was to characterize the adsorption of Bacillus subtills alpha-amylase onto crystalline starchy materials of the B-type polymorph. Monodisperse spherulitic particles (R z6; 5.0 mum), essentially resistant to alpha-amylolysis at 25 degrees C were prepared from short amylose chains (DP(n) approximately 15). The alpha-amylase adsorbed specifically onto the spherulites, and adsorption was found to be a prerequisite step for hydrolysis. Adsorption was inhibited by the presence of maltose and maltotriose in the reaction mixture. Adsorption isotherm of the enzyme on the particles showed a well developed plateau of 1.62 mug/cm(2) at 25 degrees C corresponding to a monolayer adsorption process. The binding free energy calculated from the initial slope of the isotherm was DeltaG approximately -20.7 kJ/mol. This is smaller than published values for the binding of alpha-amylase to soluble amylosic chains (DeltaG < -30 kJ/mol).     

Molecular evolution of mitochondrial 12S RNA and cytochrome b sequences in the pantherine lineage of Felidae

DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among 17 Felidae species, notably 15 in the previously described pantherine lineage. The polymerase chain reaction (PCR) was used to generate sequences of 358 base pairs of the mitochondrial 12S RNA gene and 289 base pairs of the cytochrome b protein coding gene. DNA sequences were compared within and between 17 felid and five nonfelid carnivore species. Evolutionary trees were constructed using phenetic, cladistic, and maximum likelihood algorithms. The combined results suggested several phylogenetic relationships including (1) the recognition of a recently evolved monophyletic genus Panthera consisting of Panthera leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2) the recent common ancestry of Acinonyx jubatus, the African cheetah, and Puma concolor, the American puma; and (3) two golden cat species, Profelis temmincki and Profelis aurata, are not sister species, and the latter is strongly associated with Caracal caracal. These data add to the growing database of vertebrate mtDNA sequences and, given the relatively recent divergence among the felids represented here (1-10 Myr), allow 12S and cytochrome b sequence evolution to be addressed over a time scale different from those addressed in most work on vertebrate mtDNA.      

Distribution and Activity of the Plasma Membrane H+-ATPase in Mimosa pudica L. in Relation to Ionic Fluxes and Leaf Movements

Plasma membrane H+-ATPase was immunolocalized in several cell types of the sensitive plant Mimosa pudica L., and transmembrane potentials were measured on cortical cells. In comparison with the nonspecialized cortical cells of the petiole or stem, the proton pump was highly expressed in motor cells. These immunological data are in close agreement with electrophysiological data, because the active component of the transmembrane potential was low in the nonspecialized cortical cells and high in motor cells. Therefore, motor cells contain the plasma membrane H+-ATPase required to mediate the ionic fluxes that are involved in circadian leaf movements and that are necessary to recover the turgor potential that is considerably affected by the large K+ and Cl- efflux associated with seismonastic movement. With the exception of sieve tubes, the phloem also had a high density of H+-ATPase. This suggests that the recovery of the transmembrane ionic gradients (K+ and Cl-), which is affected by various stimuli, is more energized by the companion and parenchyma cells than by the sieve elements. In addition, at the phloem/cortex interface collocytes displayed the required properties for lateral transduction of the action potential toward the pulvinal motor cells.     

Sea urchin Hox genes: insights into the ancestral Hox cluster

We describe the Hox cluster in the radially symmetric sea urchin and compare our findings to what is known from clusters in bilaterally symmetric animals. Several Hox genes from the direct-developing sea urchin Heliocidaris erythrogramma are described. CHEF gel analysis shows that the Hox genes are clustered on a < or = 300 kilobase (kb) fragment of DNA, and only a single cluster is present, as in lower chordates and other nonvertebrate metazoans. Phylogenetic analyses of sea urchin, amphioxus, Drosophila, and selected vertebrate Hox genes confirm that the H. erythrogramma genes, and others previously cloned from other sea urchins, belong to anterior, central, and posterior groups. Despite their radial body plan and lack of cephalization, echinoderms retain at least one of the anterior group Hox genes, an orthologue of Hox3. The structure of the echinoderm Hox cluster suggests that the ancestral deuterostome had a Hox cluster more similar to the current chordate cluster than was expected Sea urchins have at least three Abd-B type genes, suggesting that Abd-B expansion began before the radiation of deuterostomes.