Jifeng Chen

A signal process method for DNA segments separation in micro-channel electrophoresis.

This paper presents a signal process method for DNA segments separation in micro-channel electrophoresis. It is developed and optimized by using a laser induced fluorescence (LIF) based detection system. In this detection system, signal is sampled and processed through a novel signal process module. The results show that this signal process method provides good signal-to-noise ratios and lower limit of detection (LOD).

The Use of Immobilized Cytochrome P4502C9 in PMMA-Based Plug Flow Bioreactors for the Production of Drug Metabolites

Cytochrome P450 enzymes play a key role in the metabolism of pharmaceutical agents. To determine metabolite toxicity, it is necessary to obtain P450 metabolites from various pharmaceutical agents. Here, we describe a bioreactor that is made by immobilizing cytochrome P450 2C9 (CYP2C9) to a poly(methyl methacrylate) surface and, as an alternative to traditional chemical synthesis, can be used to biosynthesize P450 metabolites in a plug flow bioreactor. As part of the development of the CYP2C9 bioreactor, we have studied two different methods of attachment: (1) coupling via the N-terminus using N-hydroxysulfosuccinimide 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and (2) using the Ni(II) chelator 1-acetato-4-benzyl-triazacyclononane to coordinate the enzyme to the surface using a C-terminal histidine tag. Additionally, the propensity for metabolite production of the CYP2C9 proof-of-concept bioreactors as a function of enzyme attachment conditions (e.g., time and enzyme concentration) was examined. Our results show that the immobilization of CYP2C9 enzymes to a PMMA surface represents a viable and alternative approach to the preparation of CYP2C9 metabolites for toxicity testing. Furthermore, the basic approach can be adapted to any cytochrome P450 enzyme and in a high-throughput, automated process.

Orthogonal array design for minimizing loss of vitamin B9 in bread

Purpose – The purpose of this paper is to study and minimize loss of vitamin B9 in bread during warming protocol.Design/methodology/approach – In this study, warming intensity, warming time, warming device, and bread storage method were selected as the most effective factors on B9 loss in bread. The variation of B9 in bread and its loss were studied with orthogonal array design (OAD) using the L9 optimization matrix.Findings – With a calculated per cent of contribution (P%) of error of 0.38 per cent and according to the analysis of variance, ANOVA, of the fluorescence data, 86 per cent of B9 was saved by using toaster as the warming device, a bread warming temperature of <200○F and a warming time of <10min. Fluorescence method evaluated warming intensity and warming device as the most powerful factors affecting the B9 concentration in bread with corresponding P% of 42.28 per cent and 41.72 per cent, respectively.Practical implications – In conclusion, heat destroyed significant portion of B9 in bread duri...

Performance of an Electrokinetic Shuttle Polymerase Chain Reactor

An alternative polymerase chain reactor (PCR) driven by electrokinetic flow was developed and tested. A single straight microchannel and a double-T intersection were designed for injection of DNA samples and thermal cycling by shuttling between constant temperature zones. Thermal performance of the device was studied using numerical and analytical models to understand the temperature distribution. Devices were made on a polycarbonate substrate by hot embossing with a micromilled brass mold insert. A PID control system, with a tolerance of ± 0.2°C, was used to maintain the temperatures in each zone during experiments. Power consumption in each zone was predicted using thermal simulations. Molecular diffusion of 500 bp DNA was evaluated using two methods, an empirical equation and an analytical model, and the diffusion length after 20 cycles from both models was 100 μm with a 0.97 μm difference. Electroosmotic flow (EOF) was minimized by using dynamic coating and Joule heating was reduced by decreasing the KCl component in the DNA cocktail. Successful amplification of 500 bp DNA fragments at shuttle velocities of 1mm s-1 (620 seconds), 2mm s-1 (310 seconds), and 3mm s-1 (207 seconds) was demonstrated for 20 thermal cycles. The amplification efficiencies were 31%, 28%, and 18%, respectively. Unintentional flows resulting from siphoning phenomenon due to hydrostatic pressure, and Laplace pressure due to surface tension, may be responsible for the reduced amplification performance.Copyright

A Signal Process Method for Detection of Micro-Channel Electrophoresis

This paper presents a signal process method for detection of micro-channel electrophoresis. It was developed and optimized using a laser induced fluorescence (LIF) based detection system. In this detection system, signal was sampled and processed through a novel signal process module. We have used this system to DNA segments separation. The result shows that this signal process method can provide good signal-to-noise ratios.