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Measurement of colloidal system heterogeneity by Fluorescence recovery after photobleaching (FRAP) (CAT#: STEM-MT-0005-WXH)

Introduction

A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend the definition to include substances like aerosols and gels.<br />A colloid is a heterogeneous mixture in which the dispersed particles are intermediate in size between those of a solution and a suspension. The particles are spread evenly throughout the dispersion medium, which can be a solid, liquid, or gas.




Principle

Fluorescence recovery after photobleaching (FRAP) is a microscopy technique capable of quantifying the mobility of molecules within cells. By exploiting the phenomenon of photobleaching, fluorescent mole- cules within a region of interest can be selectively and irreversibly 'turned off'. It is capable of quantifying the two-dimensional lateral diffusion of a molecularly thin film containing fluorescently labeled probes, or to examine single cells.

Applications

• Characterization of the mobility of individual lipid molecules within a cell membrane.
• Analysis of molecule diffusion within the cell
• Study of protein interaction partners, organelle continuity and protein trafficking.

Procedure

1. An initial fluorescence of fluorescent molecules is measured in the region of interest (ROI).
2. The fluorescent molecules are rapidly photobleached by focusing the high-intensity laser beam onto the defined area.
3. The exchange of bleached molecules with unbleached molecules from the surrounding region is followed over time using a low-intensity laser.

Materials

• Optical microscope.
• Light source.
• Fluorescent probe.