Heterostyly in the Canarian endemic Jasminum odoratissimum (Oleaceae)

Jasminum odoratissimum is a Madeira and Canary Islands endemic showing classic heterostyly, i.e. with long-styled flowers with anthers at a low level in the corolla tube and short-styled flowers with anthers at a high level in the corolla tube. Short-styled flowers have large pollen, whereas long-styled flowers have small pollen. The two types are present in equal frequencies in the population.     

Modeling Lanthanide Complexes: Towards the Theoretical Design of Light Conversion Molecular Devices

Theoretical techniques have been developed and/or improved to predict the molecular structure of lanthanide complexes which were used to calculate their electronic properties, in particular, their electronic spectra and energy levels necessary to calculate the rates of energy transfer from the ligands to the metal ion. The molecular structure has been obtained by the SMLC/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes – Austin Model 1) model where the lanthanide ion is simulated by a sparkle implemented into the AM1 Hamiltonian used to perform a HF-SCF (Hartree-Fock Self-Consistent Field) calculation. The previous implementation of the SMLC/AM1 model (sparkle/1) involving only two parameters has been generalized to be consistent with the AM1 Hamiltonian and the new model (sparkle/2) significantly improved the prediction of molecular structures of Eu(III) complexes. For the electronic spectra and energy level calculations of the lanthanide complexes the model replaces the metal ion by a point charge with the ligands held in their positions as determined by the SMLC/AM1 model, and uses a INDO/S-CI (intermediate neglect of differential overlap/spectroscopic-configuration interaction) model. A preliminary study of the solvent effects on the absorption spectra of the free ligand is also presented. For the ligand-lanthanide ion energy transfer Fermi's golden rule is used with the multipolar and exchange mechanisms being implemented and tested for several complexes. These theoretical techniques have been applied to several complexes yielding very good results when compared to experimental data as well as predictions for the molecular and electronic structures and the relative contributions of the mechanisms for the energy transfer rates. This revised version was published online in June 2006 with corrections to the Cover Date.     

Allozymic characterization and evolutionary relationships in the BrazilianAkodon cursor species group (Rodentia-Cricetidae)

The present study involved an electrophoretic survey of 22 protein loci in 269 individuals belonging to three species of the genusAkodon, A. aff.cursor (2n=16),A. cursor (2n=14/15), andA. montensis (2n=24/25/26), collected in Eastern Brazil. The joint results of gene diversity, genetic distances, phenetic analyses, and phylogenetic trees suggested thatA. aff.cursor has recently separated fromA. cursor and that the three species have experienced a recent chromosomal divergence followed by low allozyme differentiation. These data are in agreement with their classification as sibling species.     

Generation of anNco I restriction site for translational fusions using PCR-mediated,site-directed mutagenesis

A polymerase chain reaction-based method of site-directed mutagenesis was used to introduce anNco I restriction site on the translation start site of a tomato peroxidase gene. This quick and efficient method utilized two overlapping synthetic oligonucleotide primers containing the requisite base pair changes on the ATG translation start site and two flanking primers in PCR. The resulting DNA amplified fragments were fused together byNco I digestion at the mutated ends followed by a T4 ligation reaction. A rapid alternative method utilizing the overlapping fragments and the flanking primers in PCR can also be used for ligating the two fragments. Cloning and sequencing of the PCR-amplified fragments provided additional evidence for the presence of the site-specific mutations. Unique restriction sites upstream and downstream of the site-specific mutation allows for the easy transfer of this mutated region into the wild type peroxidase gene.     

The grass megagametophyte and its possible phylogenetic implications

The structure of the grasses megagametophyte is considered to be characteristic enough as to deserve a particular place in the megagametophyte typology. Furthermore, it is compared with those of other Monocotyledonous families to point out embryological affinities.Both are members of the Carrera del Investigador (Conicet, Argentina).     

Glycine transport into plasma-membrane vesicles derived from rat brain synaptosomes.

1. Transport of glycine has been demonstrated in membrane vesicles isolated from rat brain, using artificially imposed ion gradients as the sole energy source. 2. The uptake of glycine is strictly dependent on the presence of Na+ and Cl- in the medium, and the process can be driven either by an Na+ gradient (out greater than in) or by a C1- gradient (out greater than in) when the other essential ion is present. 3. The uptake of glycine is stimulated by a membrane potential (interior negative), as demonstrated by the effects of the ionophores valinomycin and carbonyl cyanide m-chlorophenylhydrazone and anions of different permeabilities. 4. The kinetic analysis shows that glycine is accumulated by two systems with different affinities. 5. The presence of ouabain, an inhibitor (Na+ + K+)-activated ATPase, does not affect glycine transport. 6. The existence of a high-affinity, Na+-dependent glycine-uptake system in membrane vesicles derived from rat brain suggests that this amino acid may have a transmitter role in some areas of the rat brain.     

The mevalonate pathway in the bloodstream form of Trypanosoma brucei. Identification of dolichols containing 11 and 12 isoprene residues

The major surface antigen of the bloodstream form of Trypanosoma brucei, the variant surface glycoprotein, is attached to the plasma membrane via a glycosylphosphatidylinositol anchor. The biosynthesis of the glycosylphosphatidylinositol anchor, as well as the assembly of the asparagine-linked oligosaccharide chains found on the variant surface glycoproteins, involves polyisoprenoid lipids that act as sugar carriers. Preliminary observations (Menon, A.K., Schwarz, R.T., Mayor, and Cross, G.A.M. (1990) J. Biol. Chem. 265, 9033-9042) suggested that the sugar carriers in T. brucei were short-chain polyisoprenoids containing substantially fewer isoprene residues than polyisoprenols in mammalian cells. In this paper we describe metabolic labeling experiments with [3H]mevalonate, as well as chromatographic and mass spectrometric analyses of products of the mevalonate pathway in T. brucei. We report that cells of the bloodstream form of T. brucei contain a limited spectrum of short chain dolichols and dolichol phosphates (11 and 12 isoprene residues). The total dolichol content was estimated to be 0.28 nmol/10(9) cells; the dolichyl phosphate content was 0.07 nmol/10(9) cells. The same spectrum of dolichol chain lengths was also found in a polar lipid that could be labeled with [3H]mevalonate, [3H]glucosamine, and [3H]mannose, and which was characterized as Man5GlcNAc2-PP-dolichol. The most abundant product of the mevalonate pathway identified in T. brucei was cholesterol (140 nmol/10(9) cells). Ubiquinone (0.09 nmol/10(9) cells) with a solanesol side chain was also identified.