Flow cytometry, laser-based

For breweries using flow cytometry to determine yeast count and viability, it is possible to extend use of this method to detect beer spoilers such as Zygosaccharomy-ces, Dekkera (Brettanomyces), and Lactobacillus (Bouix Leveau, 1999 Donhauser, Eger, Hubl, Schmidt, Winnewisser, 1993 Jespersen, Lassen, Jakobsen, 1993). The principle of flow cytometry is based on fluorescence staining or labeling and the cells are brought in a fluid stream within a thin capillary where the fluorescence molecules are excited by a laser and the enfission is detected. The laser is also used to count the particles and determine the size. All data are collected and a report is generated with the result of live/dead cells or detection of beer spoilers. 

Flow cytometry A method of measuring the number of cells in a sample, the percentage of five cells in a sample, and certain characteristics of cells, such as size, shape, and the presence of tumor markers on the cell surface. The cells are stained with a light-sensitive dye, placed in a fluid, and passed in a stream before a laser or other type of light. The measurements are based on how the light-sensitive dye reacts to the light. 

Flame Photometry and Gas Chromatography (CyTerra) -Aerodynamic Particle Size and Shape Analysis (BIRAL) -Flow Cytometry (Luminex, LLNL) -Semiconductor-Based Ultraviolet Light (DARPA) -Polymer Fluorochrome (Echo Technology) -Laser-Induced Breakdown Spectroscopy -Raman Scattering -Infrared Absorption -Terahertz Spectroscopy -UV LIDAR... 

The difficulties of intensity-based flow cytometry are illustrated by the present difficulties of cell-by-cell measurements of intracellular calcium. This can be accomplished using the calcium probe Indo-l,(34 38) but requires an ultraviolet (UV) laser source which is not routinely available in flow cytometry (Indo-1 is an emission wavelength ratiometric probe). Flow cytometers routinely have argon ion laser sources with outputs of 488 or 514 nm. Measurement of intracellular ions other than Ca2+ is nearly impossible. (The SNAFL and SNARF probes should allow pH measurement from the wavelength-ratiometric data.(15))... 

Viability-based technologies Direct epifluorescent filter microscopy Membrane laser scanning Fluorescence cytometry Fluorescence flow cytometry... 

LASER-BASED FLOW CYTOMETRY AND FORWARD-ANGLE LIGHT SCATTERING... 

In addition, highly intense laser light sources with an energy output greater than 5 to 10 mW that are used for flow cytometry, fluorescence microscopy, and laser-induced fluorescence measurements will rapidly photodecompose some fluorescence analytes. This decomposition introduces nonlinear response curves and loss of the majority of the sample fluorescence. Fluorescence-based assays for analytes at ultralow concentrations require optimization of laser intensity and the use of a sensitive detector. 

The laser scanning cytometer (LSC) is a microscope-based cytofluorometer that combines advantages of flow cytometry and image analysis and is finding wide applicability in many disciplines of biology and medicine (see reviews in refs. 8,9). LSC measures cell fluorescence rapidly and with similar accuracy as flow cytometer. However, since the xy coordi-... 

A flow cytometer identifies different cells by measuring the light that they scatter and the fluorescence that they emit as they flow through a laser beam thus it can sort out cells of a particular type from a mixture. Indeed, a fluorescence-activated cell sorter (FACS), an instrument based on flow cytometry, can select one cell from thousands of other cells (Figure 5-34). For example, if an antibody specific to a certain cell-surface molecule is linked to a fluorescent dye, any... 

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