Santucci 2011

2011 - Analytical Chemistry 2011, 83(12), 4863-70

Optical tweezers for synchrotron radiation probing of trapped biological and soft matter objects in aqueous environments

Silvia C. Santucci, Dan Cojoc, Heinz Amenitsch, Benedetta Marmiroli, Barbara Sartori, Manfred Burghammer, Sebastian  Schoeder, Emanuela Dicola, Michael Reynolds, Christian Riekel


Investigations of single fragile objects manipulated by optical forces with high brilliance X-ray beams may initiate the development of new research fields such as protein crystallography in an aqueous environment. We have developed a dedicated optical tweezers setup with a compact, portable, and versatile geometry for the customary manipulation of objects for synchrotron radiation applications. Objects of a few micrometers up to a few tens of micrometers size can be trapped for extended periods of time. The selection and positioning of single objects out of a batch of many can be performed semi-automatically by software routines. The performance of the setup has been tested by wide-angle and small-angle X-ray scattering experiments on single optically trapped starch granules, using a synchrotron radiation microbeam. We demonstrate here for the first time the feasibility of microdiffraction on optically trapped protein crystals. Starch granules and insulin crystals were repeatedly raster-scanned at about 50 ms exposure/raster-point up to the complete loss of the structural order. Radiation damage in starch granules results in the appearance of low-angle scattering due to the breakdown of the polysaccharide matrix. For insulin crystals, order along the densely packed [110] direction is preferentially maintained until complete loss of long-range order.


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