Dynamic Light Scattering

1. Dynamic Light Scattering

3. Introduction
In 1869 J.Tyndall performed the first experimental studies on light
scattering from aerosols. He explained the blue colour of the sky by the presence of dust
in the atmosphere. DLS is routinely used for fast (a few minutes) and accurate (1-2%)
measurements of translational diffusion coefficients of macromolecules in solution and
rotational diffusion coefficients of small globular proteins and oligonucleotides, and for
anemometric measurement of linear and turbulent flow.
DLS is the most powerful technique for accurate measurements of
translational diffusion coefficients of macromolecules in solution. Dynamic Light
Scattering is a generic term encompassing all of the light scattering methods that provide
information on molecular dynamics.
DLS(Dynamic Light Scattering) analyses are routinely used in biology
laboratories to detect aggregates in macromolecular solutions, to determine the size of
proteins ,nucleic acids, and complexes or to monitor the binding of ligands. For samples
composed of a single population of particles, two characteristics derived from
Dt(Diffusivity) . First the mean hydrodynamic particles size can be calculated assuming a
simple geometry like that of a sphere. Second , the polydispersity of the population is
given by the standard deviation on Dt. The degree of poly disparity of this solution is
essentially due to asymmetry in shape and to inter molecular interaction. In a mono
disperse sample all particles are identical in size and shape.

4. The Brownian motion is that small molecules moves faster than large ones. This
movement of for example the molecules in liquid, causes constant collisions with
other molecules. Due to these frequent collisions is the movement of the liquid
molecules completely at random and no orderly structure exists. How intensive,
respectively fast, this trembling motion on a molecular level really is, depends on
the temperature and viscosity of the liquid. Here high temperatures mean a faster
motion. If the liquid contains a particle, so it also constantly collides with liquid
molecules, causing a trembling motion of the particles. The speed of this trembling
motion of the particle though depends besides on the viscosity and temperature of
the surrounding liquid also on the particle size.
The Brownian motion is that small molecules moves faster than large ones. This
movement of for example the molecules in liquid, causes constant collisions with
other molecules. Due to these frequent collisions is the movement of the liquid
molecules completely at random and no orderly structure exists. How intensive,
respectively fast, this trembling motion on a molecular level really is, depends on
the temperature and viscosity of the liquid. Here high temperatures mean a faster
motion. If the liquid contains a particle, so it also constantly collides with liquid
molecules, causing a trembling motion of the particles. The speed of this trembling
motion of the particle though depends besides on the viscosity and temperature of
the surrounding liquid also on the particle size.
The Brownian motion is that small molecules moves faster than large ones. This
movement of for example the molecules in liquid, causes constant collisions with
other molecules. Due to these frequent collisions is the movement of the liquid
molecules completely at random and no orderly structure exists. How intensive,
respectively fast, this trembling motion on a molecular level really is, depends on
the temperature and viscosity of the liquid. Here high temperatures mean a faster
motion. If the liquid contains a particle, so it also constantly collides with liquid
molecules, causing a trembling motion of the particles. The speed of this trembling
motion of the particle though depends besides on the viscosity and temperature of
the surrounding liquid also on the particle size.