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Measurement of Dynamics of ANS Binding to Apomyoglobin by Fluorescence correlation spectroscopy (FCS) (CAT#: STEM-MB-1158-WXH)

Introduction

8-Anilinonaphthalene-1-sulfonic acid (ANS), also called 1-anilino-8-naphthalenesulfonate, is an organic compound containing both a sulfonic acid and an amine group. This compound is used as a fluorescent molecular probe. For example, ANS can be used to study conformational changes induced by ligand binding in proteins, as ANS's fluorescent properties will change as it binds to hydrophobic regions on the protein surface. <br />Apomyoglobin is a representative of a group of relatively small, α-helical and globular proteins. It has been extensively employed as a model system for protein folding and stability studies.




Principle

Fluorescence correlation spectroscopy (FCS) is a statistical analysis, via time correlation, of stationary fluctuations of the fluorescence intensity. Its theoretical underpinning originated from L. Onsager's regression hypothesis. The analysis provides kinetic parameters of the physical processes underlying the fluctuations. One of the interesting applications of this is an analysis of the concentration fluctuations of fluorescent particles (molecules) in solution. In this application, the fluorescence emitted from a very tiny space in solution containing a small number of fluorescent particles (molecules) is observed. The fluorescence intensity is fluctuating due to Brownian motion of the particles. In other words, the number of the particles in the sub-space defined by the optical system is randomly changing around the average number. The analysis gives the average number of fluorescent particles and average diffusion time, when the particle is passing through the space. Eventually, both the concentration and size of the particle (molecule) are determined. Both parameters are important in biochemical research, biophysics, and chemistry.

Applications

• Measurement of the diffusion coefficient of biomolecules
• Detection of translational diffusions
• Measurement of the biomolecular concentration in vitro or in vivo
• Quantification of the viscosity of a solution
• Monitoring the binding or unbinding of two kinds of biomolecules
• Probing the diffusion paths of different directions and mapping the intercellular obstacles

Procedure

1. Sample Preparation
2. Fluorescence correlation spectroscopy (FCS) testing
3. Data analysis

Materials

Fluorescence Correlation Spectrometer