title: Agglomeration of proteins in acoustically levitated droplets.
abstract: An ultrasonic trap (acoustic levitator) was used as an analytical tool to allow container-free handling of proteins in small sample volumes. This trap was combined for the first time with synchrotron small-angle X-ray scattering (SAXS) for structure analysis of biological macromolecules in a solution. The microfocus beamline at BESSY was used as a source of intense X-ray radiation. Apoferritin (APO) was used as a model protein, and its aggregation behavior in a levitator was followed from a diluted solution to the solid state. Different stages of APO agglomeration were observed without solid container walls, which may influence aggregation behavior and produce a parasitic scattering background. Starting with a volume of 5 microL we analyzed the concentration dependence of APO structure factors in the range from 5 to 1,200 mg/mL (solid protein). The solution was stirred automatically due to convection inside the droplet caused by the ultrasonic field. SAXS data recording of APO was performed in time intervals of 60 s during an aggregation experiment of 30 to 60 min.
authors.affiliation: BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Str. 11, 12489, Berlin, Germany. friedmar.delissen@bam.de
authors.forename: Friedmar
authors.initials: F
authors.lastname: Delissen
authors.forename: Jork
authors.initials: J
authors.lastname: Leiterer
authors.forename: Ralf
authors.initials: R
authors.lastname: Bienert
authors.forename: Franziska
authors.initials: F
authors.lastname: Emmerling
authors.forename: Andreas F
authors.initials: AF
authors.lastname: Thünemann
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000818:Animals; D001052:Apoferritins / Q000737:chemistry*; D006736:Horses; D008958:Models, Molecular; D011487:Protein Conformation; D053838:Scattering, Small Angle; D055672:Static Electricity; D014465:Ultrasonics; D014961:X-Ray Diffraction
chemical_list: D001052:Apoferritins