An attoliter droplet injector for nanochemistry and single molecule biochemistry
Jianyong Tang,1 Ana Jofre,2 Rani B. Kishore,2 Geoffrey M. Lowman,1 Mark E. Greene,1 Joseph E. Reiner,3 Kristian Helmerson,2 Lori S. Goldner1
1.Optical Technology Division,.2Atomic Physics Division, Physics Laboratory, 3.Semiconductor Electronics Division, Electronics and Electrical Engineering Laboratory, National Institute of Standards and Technology
Single molecule biophysical and biochemical studies require techniques for isolating and immobilizing single molecules or molecular complexes without significantly perturbing the behavior of the system. We are developing a device (the “atto-miser”) to inject highly monodisperse attoliter droplets on-demand directly into a hydrophobic matrix. A piezoelectic tube is used to inertially launch the droplets into a low index-of-refraction fluorocarbon matrix from the orifice of a pulled micropipette which is hydrophobically coated. We have also developed a novel stoichiometric method to accurately measure the droplet size without the limitation of optical diffraction. Combined with optical tweezers and/or a fluidic system for manipulation of the “hydrosomes” (optically trappable water droplets), we can introduce and mix different reagents from different injectors. This will enable the study of single transiently interacting complexes over many interaction times, and provide a method for observing the initial events upon the binding of biological macromolecules.