High-bandwidth laser tweezers detection system for directly observing the transition paths taken by single proteins and nucleic acids during structural transitions

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Biological molecules like the proteins that make up our bodies must form intricate structures to function properly. How these structures form - a process called "folding" - is an important question for understanding biological function and for addressing diseases that arise from incorrect structures. However, the microscopic details of folding are difficult to observe because they are very fast and involve very small motions. We have developed "optical tweezers" that use lasers to grab onto single protein molecules and pull them apart, allowing us to observe structural changes with atomic-scale resolution. The timescale of the motions, however, is still too fast to resolve them properly. This project will allow us to build new tweezers instrumentation with time resolution fast enough - for the first time ever - to observe the protein while in the midst of changing its structure. It will open a new window on the folding problem, allowing us to investigate the microscopic mechanisms of folding in unprecedented detail. The instrument will first be applied to molecules with simple structures (e.g. small proteins and nucleic acids) that have been studied in depth by other techniques, both experimental and computational. By comparing to previous results, we will validate the measurements and demonstrate the improvements in resolution. We will then measure molecules with more complex structures that are involved in regulating gene expression, to understanding better the effects of structural complexity on the pathways taken by the molecule during folding. Finally, we will use the instrument to study proteins that sometimes form incorrect structures, thereby causing diseases such as "mad cow" disease & Lou Gehrig's disease. By characterising the paths taken by the proteins during the structural transitions, we hope to distinguish properties that differentiate the correct paths from those leading to diseased structures.