STEM Mass Measurements

Do you need to know the aggregation state of a protein or the stoichiometry of a protein complex?

Can we help? Our scanning transmission electron microscope is calibrated and routinely employed to measure the mass of biological samples from their electron scattering power.

Advantages:

• Only a small amount of sample is required.

• Measurements can be made over a large mass range.

• Provides an image of the sample which allows visual assessment and also mass mapping in some cases.

Mass range:

• Mass of particles: 100 kDa to over 25 MDa.

• Mass-per-length of filaments: 2 kDa/nm to over 130 kDa/nm.

• Mass-per-area of layers: approx. 1 kDa/nm² upwards.

Accuracy:

• ± 5 - 10 %; limited by the sample.

Samples:

Can be in their usual buffer solution. High concentrations of metallic cations, sucrose and glycerol should be avoided if possible. 
A protein concentration of 1 µg/microscope grid is generally sufficient (particles). In all, 4 to 8 grids prepared using 7.5 µl of solution are required to optimise the sample concentration and make the measurements.

Contact:

Dr. Shirley Müller: Shirley.Mueller@unibas.ch