Screening of the Bacillus thuringiensis Cry1Ac delta-endotoxin on the artificial phospholipid monolayer incorporated with brush border membrane vesicles of Plutella xylostella by optical biosensor technology

Facile fabrication of an interface for online coupling of microchip CE to surface plasmon resonance

Background: The aim was to develop a simple route to coupling microchip CE (MCE) to surface plasmon resonance (SPR). MCE is a microfluidic technology that utilizes microfabrication techniques to connect interacting fluid reservoirs. Its advantages include rapid analysis (typically seconds), easy integration of multiple analytical steps and parallel operation. SPR detects changes in refractive index within a short distance from the surface of a thin metal film as variations in light intensity reflected from the back of the film and, thus, does not require labeling. There is a great demand for developing hyphenated techniques like MCE–SPR that are fast, sensitive and inexpensive to analyze biological materials. Materials & Methods: The separation channel and flow cell exist as overlapping regions constructed during the microchip production and buffer solution was delivered mechanically. Such a design has successfully isolated the electrical field inherent in the MCE from the SPR detector. Consequently, the potential interference to the SPR signal (or modulation of the density of surface plasmons at the gold chip) is circumvented. Results: The limits of detection for bovine serum albumin and sodium fluorescein were determined to be 7.5 µM and 3.1 mM, respectively. Conclusion: The technique described, herein, has been successfully applied in the separation of two species. The method offers the advantages of a near zero connection dead volume, electrical shielding from the separation voltage and minimization of the mass transfer effect.

Efficient solubilization, activation, and purification of recombinant Cry45Aa of Bacillus thuringiensis expressed as inclusion bodies in Escherichia coli

A cytotoxic protein Cry45Aa of Bacillus thuringiensis expressed as inclusion bodies in Escherichia coli was solubilized in 10 mM HCl. Protein concentration of saturated solution of the recombinant Cry45Aa in 10 mM HCl was about 25 times higher than that in the buffer of previous method (in 50 mM sodium carbonate buffer, pH 10.5, containing 1 mM EDTA, and 10 mM dithiothreitol). The Cry45Aa solubilized in the acidic solution was activated by pepsin as an alternative to proteinase K in the previous method. Cytotoxic activity against CACO-2 cells of the pepsin-treated Cry45Aa was almost identical to the proteinase K-treated protein. The pepsin-treated Cry45Aa was purified by cation-exchange chromatography. The concentration of the purified protein was 539 microg/ml, which was 27-fold higher than that of the activated Cry45Aa by the previously method. The cytotoxic activity of the purified protein was stable in broad pH region (pH 2.0-11.0) for 3 days, and 97% cytotoxic activity remained after incubation at 30 degrees C for 360 min.

Bacillus thuringiensis serovar shandongiensis strain 89-T-34-22 produces multiple cytotoxic proteins with similar molecular masses against human cancer cells

AIMS

To prove that Bacillus thuringiensis serovar shandongiensis strain 89-T-34-22 produces several novel cytotoxic proteins against human leukaemic T cells.

METHODS AND RESULTS

Parasporal inclusion protein was solubilized and processed by proteinase K and was separated by anion-exchange chromatography. Cytopathic effects of each fraction against MOLT-4 and Jurkat cells were monitored.

CONCLUSIONS

Existence of at least two novel cytotoxic proteins was suggested and N-terminal sequences of the newly identified proteins were determined to be QSTTDVIREY and X (Y or I) (P or I) NLANELA (X indicates uncertain amino acids). Molecular masses of the two proteins were approx. 27-28 kDa.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study, we demonstrated that the strain 89-T-34-22 produces at least two novel cytotoxic proteins with similar molecular masses against human cancer cells. This is the first strain of B. thuringiensis which produces multiple cytotoxic proteins against human cancer cells.

Survey of the year 2001 commercial optical biosensor literature

We have assembled references of 700 articles published in 2001 that describe work performed using commercially available optical biosensors. To illustrate the technology's diversity, the citation list is divided into reviews, methods and specific applications, as well as instrument type. We noted marked improvements in the utilization of biosensors and the presentation of kinetic data over previous years. These advances reflect a maturing of the technology, which has become a standard method for characterizing biomolecular interactions.