Abstract: The present invention provides methods for determining fluorescence lifetime of a fluorophor or an optical sensor using frequency domain gated detection. The method comprises the steps of exciting the fluorophor with frequency modulated light from a pulsed light source, gating a photodetector during excitation of the fluorophore, detecting light emitted from the fluorophor with the photodetector, where the emission light exhibits a phase shift in frequency from that of the excitation light, converting the detected excitation light to an amplified electric signal, and evaluating the amplified electric signal as a measure of fluorescence lifetime of the fluorophor. Also provided is a device with which to use the methods disclosed herein.

Abstract: A method and apparatus for measuring the concentration of various analytes in a sample using native fluorescence is described. A first light source for producing a first light having a first wavelength is directed at the sample to produce a first emission from the sample, a second light source for producing a second light having a second wavelength is directed at the sample to produce a second emission from the sample. A detecting device for detecting the first and second emissions emitted from the sample, and a controlling device responsive to the detecting device for alternately switching between the first and second light source so that only one light source is directing light at the sample at any one time are employed to excite emissions from the sample to be analyzed. An analyzing device that is responsive to the controlling device for producing a duty ratio is used to determine the analytic concentration of the specific analyte present in the sample.

Abstract: A low cost apparatus and method for measuring nanosecond luminescence lifetimes with a modulated LED light source that is driven by a lock-in amplifier. The lock-in amplifier provides both a DC bias and an AC signal used to modulate the intensity of an LED source light at a wavelength capable of exciting a photoluminescent species. Excitation of the photoluminescent species produces a corresponding emission. The emission, which can be detected in a variety of ways, was measured by a photomultiplier tube with the resulting signal being sent through a DC block back to the lock-in amplifier with no external signal processing or heterodyning required. The measuring process can be controlled by a computer through a GPIB, USB, serial or similar connection. The computer can also be used to correct for the most common sources of error, namely coherent pickup and stray ambient light. The apparatus without the computer has a component cost of less than US $10,000.

Abstract: The inventive bioprocessing system (and technique) relies on non-invasive optical chemical sensing technology wherein an optical excitation source excites an optical chemical sensor. The optical chemical sensor then emits luminescence or absorbs light which is measured by a detector. The luminescence emitted from the chemical sensor or the amount of light absorbed by the chemical sensor is related to the concentration of an analyte, such as oxygen. If the luminescence emitted changes, or if the amount of light absorbed changes, then the concentration of the analyte has changed. Using such a system to measure and adjust multiple parameters at one time allows one to efficiently and cost-effectively determine optimal conditions for a given cell type and/or cell environment, for example.

Abstract: In a model system, Green fluorescent Protein fusions were constructed with several oxidative stress promoter probes from E. coli. These were chosen from the superoxide, hydrogen peroxide and hydroxyl radical inducible genes. When exposed to various free radical insults, the cells fluoresced with great specificity based on the corresponding regulon. These constructs are thus useful as a tool for mechanistic screening of a variety of anti-tumor drugs.

Abstract: Disclosed are methods and sensors for detecting the presence or concentration of an analyte in a sample, preferably a sugar such as glucose, which preferably utilizes a labeled engineered protein, or fragment thereof, that is capable of binding the analyte to be detected.

Abstract: An apparatus and method to enable minimally invasive transdermal measurements of the fluorescence lifetime of an implanted element without reagent consumption and not requiring painful blood sampling. The monitoring apparatus displays the quantity of a selected substance present in the skin and stores the data in memory. The stored information can be transmitted via modem, or antenna, to a master station for diagnostic purposes or clinical evaluation. The use of this method and apparatus improves control of blood monitoring, and therefore, enhances long-term disease management with fewer complications.

Abstract: A ground conductor break in a polyphase A.C. cable having a separate power conductor and an equal number of symmetrically spaced ground conductors for each phase is detected by sensing negative-sequence current components being induced in the ground conductors. In response to two or more ground conductors of a three-phase cable being broken, the break is detected by sensing a current flow in one of the power conductors and an absence of positive sequence current components in the ground conductors. In response to the broken ground conductor being sensed, power conductors are open circuited. The sequence components are sensed with a network including a channel responsive to the current induced in each ground conductor. Each channel includes a current transformer for deriving an A.C. voltage that is a replica of the induced current for the conductor of the particular channel. The network includes operational amplifiers responsive to the voltages derived from the current transformers.