Microchip electrophoretic protein separation using electroosmotic flow induced by dynamic sodium dodecyl sulfate-coating of uncoated plastic chips

Separation of sodium dodecyl sulfate (SDS)-protein complexes is difficult on plastic microchips due to protein adsorption onto the wall. In this paper, we elucidated the reasons for the difficulties in separating SDS-protein complexes on plastic microchips, and we then demonstrated an effective method for separating proteins using polymethyl methacrylate (PMMA) microchips. Separation difficulties were found to be dependent on adsorption of SDS onto the hydrophobic surface of the channel, by which cathodic electroosmotic flow (EOF; reversed flow) was generated. Our developed method effectively utilized the reversed flow from this cathodic EOF as a driving force for sample proteins using permanently uncoated but dynamic SDS-coated PMMA microchips. High-speed (6 s) separation of proteins and peptides up to 116 kDa was successfully achieved using this system.     

Holographic window for solar power generation

A new photovoltaic generation unit based on the application of holographic technologies called a Holo-Window is proposed in this work. The basic principle and the optical configuration used for the basic experimental unit are described. Suitable fabrication technology for a hologram with the broadband spectrum required to provide the appropriate sunlight capture capability is then discussed. Finally, a laboratory-prototype Holo-Window unit was developed and its performance was evaluated.     

A novel injection method for high-speed proteome analysis by capillary electrophoresis

We have developed a new sample injection method for capillary electrophoresis (CE) that reduces the required migration time. We demonstrated a pressurization technique that was performed with buffer in the outlet after the electrokinetic sample injection with no buffer in the outlet. To reduce the migration time, the sample injection had to be performed with no buffer in the outlet; water should be pressurized while the buffer is in the outlet. Though the resolution was slightly decreased using this method, the addition of a separation carrier (curdlan) to the run buffer restored the resolution without delaying the migration time. The use of our new sample injection method combined with our high-quality separation carrier will enable us to improve the efficiency of the high-throughput screening (HTS) system for proteome analysis.     

Bio-sensing on a chip with compact discs and nanofibers

This paper describes a novel, sensitive detection system for biomolecules (DNA and proteins etc.) that is integrated in a lab-on-a-chip utilizing optical compact discs (CDs) and bio-nanofibers. The new method comprises a microchannel containing CD grating that confines fragments of unique bacterial cellulose fibrils (BC), which have nanometre scale fibers and holes. A maximum of six times higher sensitivity to detect DNA was obtained with this CD and BC system compared to a conventional method. We also demonstrate an effective light-confining effect for biological application with the new method.     

Temperature dependence of Raman linewidth and shift in CuI

The temperature dependence of the optical phonon linewidth and frequency shift in CuI has been measured in the temperature range of 4.2 ～ 300 K. Utilizing phonon dispersion curves obtained from neutron scattering measurements, the linewidths and frequency shifts are calculated in terms of three-phonon interactions proposed by Pine and Tannenwald. The experimental results for the change in linewidth and frequency with temperature are in good agreement with this theory.     

Third-order optical nonlinearity in regioregular head-to-tail coupled poly(3-Hexylthiophene)

We measured the third-order optical nonlinearity of regioregular head-to-tail coupled poly (3-hexylthiophene) (HT-PHT) and regiorandom poly (3-hexylthiophene) (R-PHT) around exciton resonance using degenerate four wave mixing. The observed value of ∣χ⁽³⁾∣ at the exciton resonance peak of HT-PHT is in the order of 10^-9 esu which is approximately three-fold larger than that of R-PHT. We observed for the first time the enhancement in optical nonlinearity that occurs through the control of regularity of the polymeric structure. Response time of the nonlinearity was also measured using the transient grating method. The decay time of the transient grating in R-PHT and HT-PHT was less than 2 ps.     

High-speed separation of proteins by microchip electrophoresis using a polyethylene glycol-coated plastic chip with a sodium dodecyl sulfate-linear polyacrylamide solution

In this paper, we describe a method for size-based electrophoretic separation of sodium dodecyl sulfate (SDS)-protein complexes on a polymethyl methacrylate (PMMA) microchip, using a separation buffer solution containing SDS and linear polyacrylamide as a sieving matrix. We developed optimum conditions under which protein separations can be performed, using polyethylene glycol (PEG)-coated polymer microchips and electrokinetic sample injection. We studied the performance of protein separations on the PEG-coated PMMA microchip. The electrophoretic separation of proteins (21.5-116.0 kDa) was completed with separation lengths of 3 mm, achieved within 8 s on the PEG-coated microchip. This high-speed method may be applied to protein separations over a large range of molecular weight, making the PEG-coated microchip approach applicable to high-speed proteome analysis systems.     

A triple-injection method for microchip electrophoresis

We report here a novel triple injection method for microchip electrophoresis (micro-CE) that results in a higher intensity of DNA peaks. This new method includes a triple-repeated process of a combination of a sample loading voltage and a separation voltage in each interval, namely (loading time) + (separation time) + (loading time) + (separation time) + (loading time), prior to electrophoretic separation. All these injections were electrokinetically controlled by a software. Although the usual sample injection, which included the process of one 60 s electrokinetically application, was limited by the amount of sample, peaks of 40% higher intensity were obtained using the new method within half of the conventional injection time compared to the conventional method. Maximum peak intensity was successfully achieved with integration of the intensities of the triple-repeated peaks by adjusting the application period of the separation voltage. Repetition of the sample loading voltage for an adjusted period with a further adjusted period of separation voltage in each interval may be an effective method for injection of samples that results in peaks with higher intensity.     

Active compensation of rf-pulse transients

A new approach to compensate rf-pulse transients is proposed. Based on the idea of the response theory of a linear system, a formula is derived to obtain the required excitation voltage profile back from the intended target rf-pulse shape. The validity of the formula is experimentally confirmed by monitoring the rf-field created inside the sample coil with a pickup coil. Since this approach realizes accurate rf-pulse shapes without reducing the Q-factor of the tank circuit of the probe, it can be used not only to suppress the transient tail of the rf-pulse, but also as a general concept for accurate rf-pulsing.