What is the role of sucrose in protein extraction?

Answer 1

To reduce "non-specific" interactions between proteins. Similar to glycerol it stabilises proteins and helps prevent aggregation.

It also acts as a cryoprotectant during free-thaw protein extraction (which should be done via liquid nitrogen snap-freezing to prevent ice crystal formation causing protein degradation).

People will use sucrose gradients in rate-zonal centrifugations to separate proteins based on weight in a linear fashion (the increasing density and viscosity of the liquid further from the centre of rotation counteracts the change in centrifugal force).

Finally, sucrose can also be used as a 'cushion' between phases when using the differential phases of non-ionic detergents such as Triton-X 114 (cloud point 22degrees C) for separating membrane proteins.

The effect of osmolytes like sucrose and glycerol on proteins has been discussed for a long time, but is still not fully understood.

Clear is that the inclusion of osmolytes reduces the concentration of

available water in the solution, which the proteins need as "grease" for

conformational movements. Thus osmolytes stabilise proteins in a compact

conformation, resulting in higher denaturation temperatures, better

crystallisation and lower enzymatic activity.

Note that this effect is shown by compounds which have a high affinity

for water, other compounds may interact preferentially with the

proteins, leading to denaturation (e.g. SDS and DTT). This is the basis of the well known Hofmeister series for ions.

High concentrations of osmolytes will prevent bacterial growth and

protect proteins during freezing by preventing ice crystal formation.

Answer 2

Sucrose can play a role in protein extraction by acting as a stabilizing agent during the extraction process. It helps to maintain protein structure and prevent denaturation by providing a stable environment. Sucrose can also help to separate proteins from other cellular components by forming density gradients during centrifugation steps in the extraction process.