Visible Genetics Inc.

James W Cassidy

John A Renfrew

John K Stevens

James M Dunn

Alexandre M Izmailov

Paul Waterhouse

Henryk Zaleski

Gregory Dee

A high dynamic range apparatus for separation and detection of polynucleotide fragments has a housing adapted to receive an electrophoresis gel holder containing an electrophoresis gel loaded with fluorophore-labeled samples; one or more laser diodes for providing radiation of a frequency suitable for excitation of the fluorophore which irradiates a an array of excitation/detection sites on the electrophoresis gel; an array of detectors aligned with the excitation/detection sites for collecting fluorescent emissions; and one or more components for increasing the dynamic range of the instrument by at least an order of magnitude. These components, which can be used individually or in combination include detectors that are connected to a signal processing system that modulates the period of signal integration employed so that large signals are totaled at short time intervals and smaller signals are totaled at longer time intervals; the use of a beam splitter to produces a high intensity beam of emitted light and a low intensity beam of emitted light from each excitation/detection site; and a device for modulating the intensity of the excitation beam can be used to improve the dynamic range of the instrument.

High dynamic range apparatus for separation and detection of

An improved electrophoresis and fluorescence detection method for nucleotide sequences comprises a fluorescence sensing region along the path of nucleotide detection, coupled with amplification and integration in an integrator of output signals in the form of activity peaks. The output signal, which is converted to a voltage signal, is summed with a programmable offset generated by an inexpensive eight-bit D/A converter. The offset signal is selected to establish a lower starting point for the dynamic range of analog-digital conversion, and is selected to null some or all of the background fluorescence level. The integrator is switchable under program control. The integrator is switched on for long and short integration intervals. The short intervals permit sensing over a dynamic range accommodating very high levels of fluorescence; very high peaks may be measured and features of the peaks distinguished. The long intervals permit sensing over a dynamic range that is optimized for the peaks associated with the smaller peaks of individual nucleotides. In this way, the dynamic range of the analog-digital conversion permits the highest possible resolution over the range of interest during the time in which the sequencing of the nucleotides takes place. The method of nucleotide sequencing and analysis is fast, economical, and yields data with high resolution.

Electrophoresis and fluorescence detection method

A virtual DNA sequencer combines a plurality of individual DNA sequencers. Samples of DNA or other nucleic acid from subjects are prepared and allocated in real time to particular lanes or sets of lanes in electrophoresis plates of the individual sequencers, with records kept of the allocations. The data resulting from the electrophoresis runs is collected and collated according to the identities of the subjects. The individual sequencers are networked, and each individual sequencer is preferably equipped with a data buffer large enough to accommodate all or substantially all of a data run, thus protecting the virtual sequencer from loss of valuable data in the event that the network is disrupted for some portion of the time of the data run. In this way, a plurality of sequencers is virtually the same as a single sequencer with a very large number of tracks each of which can run for a much longer sequencing run than an individual sequencer.

Virtual DNA sequencer

An improved electrophoresis and fluorescence detection apparatus has an electromagnetic radiation sensor juxtaposed with a sensing region. The output signal from the electromagnetic radiation sensor is a current signal, and the current signal is converted to a voltage signal. The voltage signal is summed with a programmable offset generated by an inexpensive eight-bit D/A converter. The offset signal is selected to establish a lower starting point for the dynamic range of the A/D conversion, and is selected to null some or all of the background electromagnetic radiation level. The summed signal is amplified and integrated in an integrator. The integrator is switchable under program control. The integrator is switched on for long and short intervals. The short intervals permit sensing over a dynamic range accommodating very high levels of fluorescence; very high peaks may be measured and features of the peaks distinguished. The long intervals permit sensing over a dynamic range that is optimized for the peaks associated with the smaller peaks of individual nucleotides. In this way, the dynamic range of the A/D convertor is set to permit the highest possible resolution over the range of interest during the time in which the sequencing of the nucleotides takes place. The sequencer is fast and economical and yields data with high resolution.

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Waterloo, Canada

James W Cassidy