Esterase activity and isoenzymes in relation to morphogenesis in Mammillaria gracillis Pfeiff. tissue culture

Cactus Mammillaria gracillis Pfeiff. (Cactaceae), cultivated in vitro, spontaneously switches from an organised to unorganised way of growth, producing a habituated organogenic callus which regenerates normal and hyperhydric shoots without the addition of any growth regulators. Tumour tissues, induced by A. tumefaciens wild strain B6S3 (tumour TW) and rooty mutant GV3101 (tumour TR), do not express any organogenic potential. The esterase (arylesterase EC 3.1.1.2 and carboxylesterase EC 3.1.1.1) activity and isoenzyme pattern of morphologically different cactus tissues: shoot, callus, hyperhydric regenerant, tumours TW and TR, were compared. Tissue samples were frozen at –80 °C and lyophilized before protein extraction. Two esterase substrates, 1- and 2-naphthylacetate, were used. Esterase activity of all tissues varied during the period of one subculture. In shoots and tumours, the highest esterase activity for both substrates was measured on the 21st day, while in the callus and hyperhydric regenerants the highest activity was on the 7th day. Esterases were separated electrophoretically in polyacrylamide gradient gels under non-denaturating conditions. In total, 13 isoesterases, reacting with both substrates, were resolved. No differences in isoenzyme profile were noticed in correlation with the age of tissues, but the esterase activity varied among tissues. The significance of these results is discussed

Esterase activity and isoenzymes in relation to morphogenesis in Mammillaria gracillis Pfeiff. tissue culture

Cactus Mammillaria gracillis Pfeiff. (Cactaceae), cultivated in vitro, spontaneously switches from an organised to unorganised way of growth, producing a habituated organogenic callus which regenerates normal and hyperhydric shoots without the addition of any growth regulators. Tumour tissues, induced by A. tumefaciens wild strain B6S3 (tumour TW) and rooty mutant GV3101 (tumour TR), do not express any organogenic potential. The esterase (arylesterase EC 3.1.1.2 and carboxylesterase EC 3.1.1.1) activity and isoenzyme pattern of morphologically different cactus tissues: shoot, callus, hyperhydric regenerant, tumours TW and TR, were compared. Tissue samples were frozen at –80 °C and lyophilized before protein extraction. Two esterase substrates, 1- and 2-naphthylacetate, were used. Esterase activity of all tissues varied during the period of one subculture. In shoots and tumours, the highest esterase activity for both substrates was measured on the 21st day, while in the callus and hyperhydric regenerants the highest activity was on the 7th day. Esterases were separated electrophoretically in polyacrylamide gradient gels under non-denaturating conditions. In total, 13 isoesterases, reacting with both substrates, were resolved. No differences in isoenzyme profile were noticed in correlation with the age of tissues, but the esterase activity varied among tissues. The significance of these results is discussed

Experimental study of the collision 11Be + 64Zn around the Coulomb barrier

In this paper details of the experimental procedure and data analysis of the collision of 11Be +64Zn around the Coulomb barrier are described and discussed in the framework of different theoretical approaches. In a previous work, the elastic scattering angular distribution of the collisions 9 ,10Be +64Zn as well as the angular distribution for the quasielastic scattering and transfer/breakup cross sections for the 11Be +64Zn reaction were briefly reported. The suppression of the quasielastic angular distribution in the Coulomb-nuclear interference angular region observed in the collision of the 11Be halo nucleus with respect to the other two beryllium isotopes was interpreted as being caused by a long-range absorption owing to the long decay length of the 11Be wave function. In this paper, new continuum-discretized coupled-channel calculations of the 11Be +64Zn reaction are reported in the attempt to interpret the effect of coupling with the breakup channels on the measured cross sections. The calculations show that the observed suppression of the Coulomb-nuclear interference peak is caused by a combined effect of Coulomb and nuclear couplings to the breakup channels.INFN y Ministerio de Ciencia e Innovación (España) FPA2009-07653 FPA2009-07387 FPA2010-17142Comisión Europea 50606

Observation of 15 N + α resonant structures in 19 F using the thick target in inverse kinematics scattering method

The spectroscopy of 19 F is of interest for nuclear astrophysics and nuclear structure. In astrophysics, fluorine and the reactions producing and destroying it play a key role in constraining models of stars in different evolutionary stages, such as the asymptotic giant branch (AGB) stars, responsible of the production of about half of the elements heavier than Fe. In nuclear structure, 19 F has been subject to many investigations aiming at the identification of α and more exotic cluster structures. Also, its spectroscopy is very useful to constrain the nuclear properties of the 19 Ne mirror nucleus. In this work, we report on the measurement of the 15 N − α elastic scattering using the thick target inverse kinematics approach, allowing us to span a very large fluorine excitation energy range ( ∼ 6 –10 MeV). The use of 15 N − α scattering proves very useful to study α clustering in 19 F thanks to the likelihood for populating states with such a structure. Indeed, the R -matrix analysis of the measured differential cross sections shows the occurrence of many candidate α -cluster states of 19 F . It also calls for the redefinition of the spin-parity and widths of a number of 19 F states with respect to what reported in the literature

Quasielastic backscattering and barrier distributions for the 6, 7Li + 64Zn systems

Excitation functions of quasielastic scattering at backward angles were measured for the weakly bound 6Li and 7Li projectiles on a 64Zn target at energies around the Coulomb barrier. The corresponding barrier distributions were derived from the experimental cross sections. The experimental data were analyzed within the coupled-channel model using a double-folding potential as the bare potential. Inelastic excitations of the target, the 7Li first excited state, and 6Li, 7Li resonant state(s), corresponding to sequential breakup, were included in the calculations. The comparison between the data and coupled-channel predictions shows that the effects of channels not included in the calculations, such as direct breakup and transfers, are much larger for 6Li than for 7Li

Elastic Scattering for the 11Be+64Zn System Close to the Coulomb Barrier

The quasi-elastic scattering angular distribution of the collision 11Be + 64Zn was measured and compared with the elastic scattering angular distribution for its core, the 10Be nucleus on the same target. Optical model and continuum-discretized coupled-channel calculations of the 11Be+64Zn reaction were performed in order to interpret the effect of coupling with the break-up channels on the measured cross-sections