Enhanced bioconversion rate and released substrate inhibition in (R)-phenylephrine whole-cell bioconversion via partial acetone treatment.

An approach was developed to enhance the efficiency for the bioconversion of 1-(3-hydroxyphenyl)-2-(methyamino)-ethanone to (R)-phenylephrine. The strain Serratia marcescens N10612, giving the benefit of 99% enantiomeric excess in (R)-PE conversion, was used. The fermentation was devised to harvest cells with high hydrophobic prodigiosin content inside the cells. Then, the partial acetone extraction was applied to remove prodigiosin from the cells. The treatment was found to increase the cells conversion rate without loss of the cells NADPH redox system. When using 50% (v/v) acetone for 5min, the processed cells can give a specific conversion rate of 16.03µmol/h/g-cells. As compared the treated cells with cells under the basal medium, the maximum reaction rate (Vmax) increased from 6.69 to 10.27 (µmol/h/g-cells), the dissociation constant (Km) decreased from 0.236 to 0.167mM and the substrate inhibition constant (KSi) increased from 0.073 to 1.521mM. The 20-fold increase in substrate inhibition constant referred to a great release from the substrate inhibition for the use of S. marcescens N10612 in the bioconversion, which would greatly benefit the bioconversion to be industrialized.

Fast Monte Carlo simulation of DNA damage induction by Auger-electron emission.

PURPOSE: A local damage model (LDM) was developed to estimate the biological efficiency of Auger-electron-emitting radionuclides. MATERIALS AND METHODS: The LDM required information on the local dose distribution, local energy spectrum, and clustered DNA damage yields in the cell nucleus. To apply the model, the nucleus was divided into concentric shells where each shell contributed its own local dose, energy spectrum, and damage yield. The local doses and energy spectra were computed using the PENELOPE (PENetration and Energy LOss of Positrons and Electrons) code. The DNA damage yields were estimated using the MCDS (Monte Carlo damage simulation) code. RESULTS: For a typical 4-µm radius mammalian cell nucleus, the absorbed doses to the cell nucleus per unit cumulated activity, equal to 0.0065, 0.00418, 0.0028, 0.0027 and 0.0015 Gy Bq(-1) s(-1) for (125)I, (119)Sb, (123)I, (111)In and (99m)Tc, were within 6% difference with the MIRD (Medical Internal Radiation Dose) published data. The simulated total (simple and complex) single-strand break (SSB) and double-strand break (DSB) yields were in the same order, i.e., (125)I > (119)Sb > (123)I > (111)In > (99m)Tc. The agreement between present results and literature data for the DNA damage yields was generally good. More than 75% of the total SSB and DSB yields were contributed from regions within 2.5 µm of the nucleus center. CONCLUSIONS: The proposed methodology was computationally efficient and could be applied to other irradiation geometries such as cell clusters.

Bluetooth based chaos synchronization using particle swarm optimization and its applications to image encryption.

This study used the complex dynamic characteristics of chaotic systems and Bluetooth to explore the topic of wireless chaotic communication secrecy and develop a communication security system. The PID controller for chaos synchronization control was applied, and the optimum parameters of this PID controller were obtained using a Particle Swarm Optimization (PSO) algorithm. Bluetooth was used to realize wireless transmissions, and a chaotic wireless communication security system was developed in the design concept of a chaotic communication security system. The experimental results show that this scheme can be used successfully in image encryption.