Molecular immobilisationat the diffraction limit
 
Summary
 
We have developed a new photonic technology and demonstrate that it allows for precise immobilisation of proteins to sensor surfaces. The new technology secures spatially controlled molecular immobilisation since the immobilisation of each molecule to a support surface can be limited to the focal point of the UV laser beam, with dimensions as small as a few micrometers. We now show that we can immobilise molecules on a surface with any arbitrary pattern, including immobilisation of biomolecules according to diffraction patterns of light. The observed pattern of immobilised proteins reproduces the diffraction pattern of light used to induce molecular immobilisation. 
 
 
Fluorescence from proteins immobilised according to a diffraction pattern

The diffraction limited resolution of our current setup is given by d = lambda * 0.61 / NA , where lambda is the wavelength used (280 nm) and NA is the numerical aperture of the focusing lens. For our lens the lens has a NA of 1/3 which yields d = 512 nm i.e. just about half a micron. This distance should be compared with the radius of the central peak (from the center of the top to the center of the first dark ring in the circular part of the diffraction pattern).

From the analyzed picture of the immobilized diffraction pattern the diameter of the first dark ring around the central peak can be estimated to be roughly 1 micrometer, which fits exactly with he expected value of 500 nm for the radius (half the diameter).

 

 

A 2x2 microarray of proteins, where each spot contains proteins immobilised according to the diffraction pattern of the light that induced molecular immobilisation

 

 

 

 

 

 

                                                                Details of one Spot