title: Spatiotemporal image correlation spectroscopy (STICS) theory, verification, and application to protein velocity mapping in living CHO cells.
abstract: We introduce a new extension of image correlation spectroscopy (ICS) and image cross-correlation spectroscopy (ICCS) that relies on complete analysis of both the temporal and spatial correlation lags for intensity fluctuations from a laser-scanning microscopy image series. This new approach allows measurement of both diffusion coefficients and velocity vectors (magnitude and direction) for fluorescently labeled membrane proteins in living cells through monitoring of the time evolution of the full space-time correlation function. By using filtering in Fourier space to remove frequencies associated with immobile components, we are able to measure the protein transport even in the presence of a large fraction (>90%) of immobile species. We present the background theory, computer simulations, and analysis of measurements on fluorescent microspheres to demonstrate proof of principle, capabilities, and limitations of the method. We demonstrate mapping of flow vectors for mixed samples containing fluorescent microspheres with different emission wavelengths using space time image cross-correlation. We also present results from two-photon laser-scanning microscopy studies of alpha-actinin/enhanced green fluorescent protein fusion constructs at the basal membrane of living CHO cells. Using space-time image correlation spectroscopy (STICS), we are able to measure protein fluxes with magnitudes of mum/min from retracting lamellar regions and protrusions for adherent cells. We also demonstrate the measurement of correlated directed flows (magnitudes of mum/min) and diffusion of interacting alpha5 integrin/enhanced cyan fluorescent protein and alpha-actinin/enhanced yellow fluorescent protein within living CHO cells. The STICS method permits us to generate complete transport maps of proteins within subregions of the basal membrane even if the protein concentration is too high to perform single particle tracking measurements.
authors.affiliation: Department of Physics and Department of Chemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Benedict
authors.initials: B
authors.lastname: Hebert
authors.forename: Santiago
authors.initials: S
authors.lastname: Costantino
authors.forename: Paul W
authors.initials: PW
authors.lastname: Wiseman
mesh_terms: D000185:Actinin / Q000737:chemistry; D000465:Algorithms; D000818:Animals; D001703:Biophysics / Q000379:methods*; D016466:CHO Cells; D003198:Computer Simulation; D006224:Cricetinae; D004058:Diffusion; D005456:Fluorescent Dyes / Q000494:pharmacology; D005583:Fourier Analysis; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D018613:Microscopy, Confocal; D008863:Microspheres; D015233:Models, Statistical; D017785:Photons; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013053:Spectrophotometry / Q000295:instrumentation* / Q000379:methods*; D013997:Time Factors
chemical_list: C485182:Cyan Fluorescent Protein; D005456:Fluorescent Dyes; D011506:Proteins; D011993:Recombinant Fusion Proteins; D000185:Actinin; D049452:Green Fluorescent Proteins
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