A Hybrid Tirf-Magnetic Tweezers Instrument for Studying Force-Induced Conformational Changes in Proteins

Optical tweezers are a useful research tool for applying forces to single proteins and measuring the resulting changes in extension, but they can only observe conformational changes along the axis of force application and only if the accompanying changes in extension are on the nanometer scale. Our experimental setup skirts this limitation by measuring distance changes using single-molecule Forster resonance energy transfer (smFRET) produced from a total internal reflection fluorescence (TIRF) microscope incorporating magnetic tweezers.