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Macromolecular Crystallisation Diagnostics by Dual polarization interferometry (DPI) (CAT#: STEM-MB-0444-WXH)

Introduction

DPI was found to also be an effective diagnostic tool for macromolecular crystallisation, which may allow the early and efficient detection of conditions that are most likely to lead to crystals, more economically than by conventional screening. It may in addition provide information useful to the study of nucleation as well as to crystal optimisation. It is shown that DPI can be used to discriminate between the formation of crystalline and amorphous material in real time, in a dialysis setup. This setup allows the screening of a continuous or stepwise concentration gradient of a precipitating agent in one trial. Real-time DPI monitoring of such a trial provides therefore information as to whether this particular precipitant or precipitant/buffer combination is worth pursuing and optimising for crystal production.




Principle

Dual polarization interferometry (DPI) is an analytical technique that allows the simultaneous determination of thickness, density, and mass of a biological layer on a sensing waveguide surface in real time. DPI focuses laser light into two waveguides. One of these functions as the "sensing" waveguide having an exposed surface while the second one functions to maintain a reference beam. A two-dimensional interference pattern is formed in the far field by combining the light passing through the two waveguides. The DPI technique rotates the polarization of the laser, to alternately excite two polarization modes of the waveguides. Measurement of the interferogram for both polarizations allows both the refractive index and the thickness of the adsorbed layer to be calculated. These measurements can be used to infer conformational information about the molecular interactions taking place, as the molecule size (from the layer thickness) and the fold density (from the RI) change.

Applications

Macromolecular Crystallisation Diagnostics.
Early and efficient detection of conditions that are most likely to lead to crystals.
Study of nucleation as well as to crystal optimisation

Procedure

1. Setting of dual polarization interferometry
2. Preparing the DPI sensor chip
3. Immobilization of target on DPI biosensor
4. Reagent was injected to react
5. Quantitative analysis

Materials

• DPI biosensor
• DPI sensor chip