Polysome profiling

Polysome profiling is a technique in molecular biology that is used to study the association of mRNAs with ribosomes.

This lysate contains polysomes, monosomes (composed of one ribosome residing on an mRNA), the small (40S in eukaryotes) and large (60S in eukaryotes) ribosomal subunits, "free" mRNA and a host of other soluble cellular components.

A specific amount (as measured by optical density) of the lysate is then layered gently on top of the gradient in the tube.

The lysate, even though it contains a large amount of soluble material, is much less dense than 15% sucrose, and so it can be kept as a separate layer at the top of the tube if this is done gently.

The first fractions removed have a large amount of relatively small molecules, such as tRNAs, individual proteins, etc.