title: Optical tweezers for synchrotron radiation probing of trapped biological and soft matter objects in aqueous environments.
abstract: 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.
authors.affiliation: European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Cedex, France. silvia.santucci@esrf.fr
authors.forename: Silvia C
authors.initials: SC
authors.lastname: Santucci
authors.forename: Dan
authors.initials: D
authors.lastname: Cojoc
authors.forename: Heinz
authors.initials: H
authors.lastname: Amenitsch
authors.forename: Benedetta
authors.initials: B
authors.lastname: Marmiroli
authors.forename: Barbara
authors.initials: B
authors.lastname: Sartori
authors.forename: Manfred
authors.initials: M
authors.lastname: Burghammer
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schoeder
authors.forename: Emanuela
authors.initials: E
authors.lastname: DiCola
authors.forename: Michael
authors.initials: M
authors.lastname: Reynolds
authors.forename: Christian
authors.initials: C
authors.lastname: Riekel
mesh_terms: D003460:Crystallization; D007328:Insulin / Q000737:chemistry; D052898:Optical Tweezers; D010316:Particle Size; D053838:Scattering, Small Angle; D011198:Solanum tuberosum / Q000378:metabolism; D013213:Starch / Q000737:chemistry; D017356:Synchrotrons; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D007328:Insulin; D014867:Water; D013213:Starch