title: Brownian nanoimaging of interface dynamics and ligand-receptor binding at cell surfaces in 3-D.
abstract: We describe a method for nanoimaging interfacial dynamics and ligand-receptor binding at surfaces of live cells in 3-D. The imaging probe is a 1-μm diameter glass bead confined by a soft laser trap to create a "cloud" of fluctuating states. Using a facile on-line method of video image analysis, the probe displacements are reported at ~10 ms intervals with bare precisions (±SD) of 4-6 nm along the optical axis (elevation) and 2 nm in the transverse directions. We demonstrate how the Brownian distributions are analyzed to characterize the free energy potential of each small probe in 3-D taking into account the blur effect of its motions during CCD image capture. Then, using the approach to image interactions of a labeled probe with lamellae of leukocytic cells spreading on cover-glass substrates, we show that deformations of the soft distribution in probe elevations provide both a sensitive long-range sensor for defining the steric topography of a cell lamella and a fast telemetry for reporting rare events of probe binding with its surface receptors. Invoking established principles of Brownian physics and statistical thermodynamics, we describe an off-line method of super resolution that improves precision of probe separations from a non-reactive steric boundary to ~1 nm.
authors: Biomedical Engineering, Boston University, Boston, MA 02215, USA.
authors: Igor R
authors: IR
authors: Kuznetsov
authors: Evan A
authors: EA
authors: Evans
mesh_terms: D000465:Algorithms; D002138:Calibration; D022081:Cell Surface Extensions / Q000378:metabolism* / Q000648:ultrastructure; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D039041:Integrin alpha4beta1 / Q000378:metabolism; D019169:Jurkat Cells; D007700:Kinetics; D008024:Ligands; D016013:Likelihood Functions; D008390:Markov Chains; D018715:Microscopy, Video / Q000379:methods; D008954:Models, Biological; D036103:Nanotechnology / Q000379:methods; D052898:Optical Tweezers; D011485:Protein Binding; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D005353:Fibronectins; D039041:Integrin alpha4beta1; D008024:Ligands