Genome re-diploidization occurs spontaneously just prior to anthesis in artificially induced auto-tetraploid maize (Zea mays L.) inbred lines

Plant Cell, Tissue and Organ Culture (PCTOC) - In this study, various concentrations of oryzalin (0, 5, 10, 50, and 100 mg l?1), trifluralin (0, 5, 10, 50, and...     

Diurnal variation of the delta 13C of pine needle respired CO2 evolved in darkness

The delta 13C of pine needle CO2 evolved in darkness (delta 13Cr) for slash pine trees (Pinus elliottii) was determined by placing recently collected pine needles in darkness and collecting respired CO2 over a short time period (<15 min). Delta 13Cr measurements were made over several 24 h periods to test the hypothesis that significant variation in delta 13Cr would be observed during a diurnal cycle. The delta 13Cr measurements from the 24 h time series trials showed a consistent midday 13C-enrichment (5-10 per thousand) relative to bulk biomass. The delta 13Cr values became more 13C-depleted at night and following shading, and approached bulk-biomass delta 13C values by dawn. The effect of night-time respired 13C-enriched CO2 on the delta 13C value of the remaining assimilate is shown to be minimal (13C depleted by 0.22 per thousand) under field conditions for P. elliottii needles.     

Spermine as a porcine pancreatic elastase activator: spectroscopic and molecular simulation studies

Abstract

The aim of this study was to investigate the spermine effect on the thermal denaturation, conformation and activity of elastase at three temperatures of 303, 313 and 323?K in the Tris buffer, at pH 8.5, using UV–vis spectrophotometry, spectrofluorometry and circular dichroism as well as molecular docking and molecular simulation. The increased absorption of elastase in the presence of spermine suggested a change in the environment of tryptophan. It was found that under the influence of spermine, the emission intensity of elastase extremely was reduced, and the use of the Stern-Volmer equation showed that some static quenching had occurred. The thermodynamic parameters values (enthalpy and entropy) and the molecular docking technique also revealed that van der Waals forces or hydrogen bonding interactions played an important role in the binding process. The spermine–elastase complex formation led to increasing the value of the catalytic constant (k_cat). So it could be considered as an activator. Slight changes were observed in the second structure of elastase (1.06% increase for the α-helix and 0.048% decrease the β-sheet) and the thermal stability effect. Molecular docking results also demonstrated that spermine could bind to porcine pancreatic elastase, and van der Waals forces or hydrogen bonding interactions played the major role in the binding process. Overall, our results showed that spermine could induce structural alterations in elastase, acting as a partial stabilizer and an activator for the enzyme.

Communicated by Ramaswamy H. Sarma     

On problem solving with Hopfield neural networks

Hopfield and Tank have shown that neural networks can be used to solve certain computationally hard problems, in particular they studied the Traveling Salesman Problem (TSP). Based on network simulation results they conclude that analog VLSI neural nets can be promising in solving these problems. Recently, Wilson and Pawley presented the results of their simulations which contradict the original results and cast doubts on the usefulness of neural nets. In this paper we give the results of our simulations that clarify some of the discrepancies. We also investigate the scaling of TSP solutions found by neural nets as the size of the problem increases. Further, we consider the neural net solution of the Clustering Problem, also a computationally hard problem, and discuss the types of problems that appear to be well suited for a neural net approach.