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Counting Nucleosomes in Living Cells by Fluorescence correlation spectroscopy (FCS) (CAT#: STEM-MB-1134-WXH)

Introduction

A nucleosome is the basic structural unit of DNA packaging in eukaryotes. The structure of a nucleosome consists of a segment of DNA wound around eight histone proteins and resembles thread wrapped around a spool. The nucleosome is the fundamental subunit of chromatin. Each nucleosome is composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones, which are known as a histone octamer. Each histone octamer is composed of two copies each of the histone proteins H2A, H2B, H3, and H4.




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