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Biomedical subjects

E Artacho

Publications and source records attributed to E Artacho.

17 recordsLinked to original sources
PubMed2001

Polarons in carbon nanotubes.

We use ab initio total-energy calculations to predict the existence of polarons in semiconducting carbon nanotubes (CNTs). We find that the CNTs' band edge energies vary linearly and the elastic energy increases quadratically with both radial and with axial distortions, leading to the spontaneous formation of polarons. Using a continuum model parametrized by the ab initio calculations, we estimate electron and hole polaron lengths, energies, and effective masses and analyze their complex dependence on CNT geometry. Implications of polaron effects on recently observed electro- and optomechanical behavior of CNTs are discussed.

Journal Article↗
PubMed2000

Absence of dc-conductivity in lambda-DNA.

The electrical conductivity of biomaterials on a molecular scale is of fundamental interest in the life sciences. We perform first principles electronic structure calculations, which clearly indicate that lambda-DNA chains should present large resistance values. We also present two direct procedures to measure electrical currents through DNA molecules adsorbed on mica. The lower limit for the resistivity is 10(6) Omega . cm, in agreement with our calculations. We also show that low energy electron bombardment induces a rapid contamination and dramatically affects the measured conductivity, thus providing an explanation to recent reports of high DNA conductivity.

Animals↗
PubMed2000

New superhard phases for three-dimensional C60-based fullerites

We have explored new possible phases of 3D C60-based fullerites using semiempirical potentials and ab initio density functional methods. We have found three closely related structures-two body-centered orthorhombic and one body-centered cubic-having 52, 56, and 60 tetracoordinated atoms per molecule. These 3D polymers result in semiconductors with bulk moduli near 300 GPa, and shear moduli around 240 GPa, which make them good candidates for new low density superhard materials.

Journal Article↗
PubMed1986

Synergistic effect of ammonium and potassium ions on pyruvate kinase from Ehrlich ascites tumor cells.

The effect of NH4+ on M2-pyruvate kinase isolated from Ehrlich ascites tumor cells was investigated. The enzyme is activated by NH4+ more efficiently than by K+. Moreover, a synergistic interaction of the two cations is observed since NH4+ increases the affinity of the enzyme for K+. The affinity of the enzyme for phosphoenolpyruvate is also increased in the presence of NH4+, and in these conditions the activating effect of fructose-1,6-bisphosphate is reduced. It is proposed that NH4+ be considered a specific allosteric activator of the tumor enzyme.

Ammonia↗