On the self-condensation of aminoguanidine leading to 1,1,4,10,10-pentaamino-2,3,5,6,8,9-hexaazadeca-1,3,5,7,9-pentaene (structure elucidation through X-ray powder diffraction)

Chemical and spectroscopic (UV; ¹H, ¹³C, ¹⁵N NMR; HRMS) studies determined the structure of 1,1,4,10,10-pentaamino-2,3,5,6,8,9-hexaazadeca-1,3,5,7,9-pentaene for the red-violet compound, which was obtained by treating aminoguanidine hydrochloride with KOH. X-ray powder diffraction and lattice-constrained PBC-DFT optimization confirmed this structure and defined a linear all-trans configuration.     

An easy access to halogenated and non-halogenated spiro-hexadienones

We describe an improved protocol for the synthesis of spiro-hexadienones from Morita–Baylis–Hillman adducts. Solvent modification and temperature resulted in a significant increase in the yield. This protocol was used to synthesize mono- and dibrominated spiro-hexadienones in good overall yields. This report is the first to describe the synthesis of halogenated spiro-hexadienones from Morita–Baylis–Hillman adducts.     

Stochastic induced dynamics in neuromorphic optoelectronic oscillators

We investigate the dynamics of optoelectronic oscillator (OEO) systems based on resonant tunneling diode photodetector (RTD-PD) and laser diode hybrid integrated circuits. We demonstrate that RTD-based OEOs can be noise-activated in either monostable or bistable operating conditions, providing a rich variety of signal outputs—spiking, square pulses, bursting—and behaviours—stochastic and coherence resonances—that are similar to that of biological systems such as neurons. The potential for fully monolithic integration of our OEO confers them a great potential in novel neuromorphic optoelectronic circuits for signal processing tasks including re-timing and re-shaping of pulsed signals exploiting either the monostable or the bistable operating conditions.     

Characterization of Glycosyltransferase Activity of Wild-Type Leuconostoc mesenteroides Strains from Bulgarian Fermented Vegetables

Glycosyltransferase activity of 13 Leuconostoc mesenteroides strains isolated from Bulgarian fermented vegetables was investigated. All the strains displayed a mucoid phenotype on sucrose-containing agar media. Strains were characterized according to carbohydrate fermentation, species-specific multiple PCR using several primers, repetitive element-PCR fingerprinting using (GTG)₅ primers and glycosyltransferase activity. Level of activity and cellular localization (soluble or cell-associated) were variable among strains. Precipitation of exopolysaccharides produced from sucrose by the soluble fractions from these strains allowed recovery of only glucans and further characterization by ¹H and ¹³C NMR analysis and enzymatic digestion with dextranase revealed dextran production. However, levans could be detected in presence of raffinose as fructosyl donor. Both fructosyltransferase and glucosyltransferase encoding genes were detected by PCR and both active enzymes were detected after functional characterization by SDS-PAGE electrophoresis and in situ polymer production after incubation with sucrose. This work therefore showed that concomitant production of glucosyltransferase and fructosyltransferase is widespread in L. mesenteroides strains.     

Computer data analysis of the oscillating forward–reverse method

Nonequilibrium work theorems have recently gained wide acceptance as useful tools in determining free energy profiles for soft-matter systems. We have recently proposed an extension of the forward–reverse method, called the oscillating forward–reverse method; by introducing an oscillatory drift it enables the user to obtain PMFs from a single nonequilibrium pull. The analysis, although manageable, is non-trivial. We present here the data analysis and the software (OFR-AT) created to construct PMFs and associated uncertainties from the oscillating forward–reverse (OFR) method. The output analyzed by OFR-AT is often from molecular dynamics simulations, but as with the OFR method itself, it can be more generally applied. OFR-AT is a fast and efficient analysis tool that can analyze very large files (larger than 5 GB) in a short time period. We also describe the uncertainty and correlation calculations performed, provide a map of the data flow through the program, and present representative examples of PMF profiles calculated using OFR-AT.