A fluorescence resonance energy transfer-derived structure of a quantum dot-protein bioconjugate nanoassembly.

The first generation of luminescent semiconductor quantum dot (QD)-based hybrid inorganic biomaterials and sensors is now being developed. It is crucial to understand how bioreceptors, especially proteins, interact with these inorganic nanomaterials. As a model system for study, we use Rhodamine red-labeled engineered variants of Escherichia coli maltose-binding protein (MBP) coordinated to the surface of 555-nm emitting CdSe-ZnS core-shell QDs. Fluorescence resonance energy transfer studies were performed to determine the distance from each of six unique MBP-Rhodamine red dye-acceptor locations to the center of the energy-donating QD. In a strategy analogous to a nanoscale global positioning system determination, we use the intraassembly distances determined from the fluorescence resonance energy transfer measurements, the MBP crystallographic coordinates, and a least-squares approach to determine the orientation of the MBP relative to the QD surface. Results indicate that MBP has a preferred orientation on the QD surface. The refined model is in agreement with other evidence, which indicates coordination of the protein to the QD occurs by means of its C-terminal pentahistidine tail, and the size of the QD estimated from the model is in good agreement with physical measurements of QD size. The approach detailed here may be useful in determining the orientation of proteins in other hybrid protein-nanoparticle materials. To our knowledge, this is the first structural model of a hybrid luminescent QD-protein receptor assembly elucidated by using spectroscopic measurements in conjunction with crystallographic and other data.

Driver behaviour of ethanol-impaired non-vehicular trauma victims.

During a recent 12-month period, a group of patients injured from causes other than road accidents were studied. Twenty-four patients with no evidence of alcohol impairment served as controls for another group of 24 patients with a blood alcohol concentration of greater than 100 mg%. Examination of public records revealed that the alcohol-impaired group had committed more serious traffic violations, including reckless driving, crashes causing bodily injury, and property damage. Eleven of the 24 alcohol-impaired subjects had a total of 18 previous citations for driving under the influence of alcohol while there were none in the control group (P less than 0.001). Alcohol-related non-vehicular trauma is highly predictive of alcohol-impaired driving behaviour.