Kulim Kht DP Meeting Helsinki

An Introduction to Biophysical Characterisation

using Dual Polarisation Interferometry

Dual Polarisation Interferometry (DPI) is a highly versatile, powerful analytical technique for

biophysical characterisation of proteins and other biomolecules. It extends the typical dynamic

measurements of conventional biosensors by including an additional quantitative, sub molecular,

conformational measurement.

DPI delivers a unique perspective on biochemistry, linking conformational changes to biochemical activity at a resolution normally associated with ‘big physics.

Two polarisations of light are passed through the

sensor which consists of an upper ‘sensing’ layer

and an embedded ‘reference’ layer. The output

from each of the layers then combine producing two

interference patterns which are detected by a

camera.

As molecules bind (or change shape) on the

surface of the ‘sensing’ layer, they are probed by

the evanescent field from the ‘sensing’ surface.

This, in turn, changes both interference patterns. As

material binds, the interference pattern shifts one

way. As material is removed from the surface, the

interference pattern returns.

The AnaLight® Resolver software automatically analyses both sets of data and outputs the real time

changes in the thickness, density and mass of the molecular layer. All of the calculations are based on

classical optics theory and have been independently validated by, amongst others, the National

Physics Laboratory (NPL) in the UK. www.farfield-group.com