Biophys J, August 2000, p. 1095-1106, Vol. 79, No. 2

Multiple-Particle Tracking Measurements of Heterogeneities in Solutions of Actin Filaments and Actin Bundles

Joshua Apgar,^* Yiider Tseng,^* Elena Fedorov, Matthew B. Herwig,^* Steve C. Almo, and Denis Wirtz^*

Departments of  ^*Chemical Engineering and  Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218; and  Department of Biochemistry, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461 USA

One of the central functions of actin cytoskeleton is to provide the mechanical support required for the establishment and maintenance of cell morphology. The mechanical properties of actin filament assemblies are a consequence of both the available polymer concentration and the actin regulatory proteins that direct the formation of higher order structures. By monitoring the displacement of well-dispersed microspheres via fluorescence microscopy, we probe the degree of spatial heterogeneity of F-actin gels and networks in vitro. We compare the distribution of the time-dependent mean-square displacement (MSD) of polystyrene microspheres imbedded in low- and high-concentration F-actin solutions, in the presence and absence of the F-actin-bundling protein fascin. The MSD distribution of a 2.6-µM F-actin solution is symmetric and its standard deviation is similar to that of a homogeneous solution of glycerol of similar zero-shear viscosity. However, increasing actin concentration renders the MSD distribution wide and asymmetric, an effect enhanced by fascin. Quantitative changes in the shape of the MSD distribution correlate qualitatively with the presence of large heterogeneities in F-actin solutions produced by increased filament concentration and the presence of actin bundles, as detected by confocal microscopy. Multiple-particle tracking offers a new, quantitative method to characterize the organization of biopolymers in solution.

Biophys J, August 2000, p. 1095-1106, Vol. 79, No. 2
© 2000 by the Biophysical Society   0006-3495/00/08/1095/12  $2.00

This article has been cited by other articles:

				M. Tassieri, R. M. L. Evans, L. Barbu-Tudoran, J. Trinick, and T. A. Waigh The Self-Assembly, Elasticity, and Dynamics of Cardiac Thin Filaments Biophys. J., March 15, 2008; 94(6): 2170 - 2178. [Abstract] [Full Text] [PDF]

				J. S. H. Lee, C. M. Hale, P. Panorchan, S. B. Khatau, J. P. George, Y. Tseng, C. L. Stewart, D. Hodzic, and D. Wirtz Nuclear Lamin A/C Deficiency Induces Defects in Cell Mechanics, Polarization, and Migration Biophys. J., October 1, 2007; 93(7): 2542 - 2552. [Abstract] [Full Text] [PDF]

				N. Salamat-Miller, J. Fang, C. W. Seidel, Y. Assenov, M. Albrecht, and C. R. Middaugh A Network-based Analysis of Polyanion-binding Proteins Utilizing Human Protein Arrays J. Biol. Chem., April 6, 2007; 282(14): 10153 - 10163. [Abstract] [Full Text] [PDF]

				B. R. Daniels, B. C. Masi, and D. Wirtz Probing Single-Cell Micromechanics In Vivo: The Microrheology of C. elegans Developing Embryos Biophys. J., June 15, 2006; 90(12): 4712 - 4719. [Abstract] [Full Text] [PDF]

				S. L. Gupton, K. L. Anderson, T. P. Kole, R. S. Fischer, A. Ponti, S. E. Hitchcock-DeGregori, G. Danuser, V. M. Fowler, D. Wirtz, D. Hanein, et al. Cell migration without a lamellipodium: translation of actin dynamics into cell movement mediated by tropomyosin J. Cell Biol., February 14, 2005; 168(4): 619 - 631. [Abstract] [Full Text] [PDF]

				T. Savin and P. S. Doyle Static and Dynamic Errors in Particle Tracking Microrheology Biophys. J., January 1, 2005; 88(1): 623 - 638. [Abstract] [Full Text] [PDF]

				T. P. Kole, Y. Tseng, L. Huang, J. L. Katz, and D. Wirtz Rho Kinase Regulates the Intracellular Micromechanical Response of Adherent Cells to Rho Activation Mol. Biol. Cell, July 1, 2004; 15(7): 3475 - 3484. [Abstract] [Full Text] [PDF]

				Y. Tseng, J. S. H. Lee, T. P. Kole, I. Jiang, and D. Wirtz Micro-organization and visco-elasticity of the interphase nucleus revealed by particle nanotracking J. Cell Sci., April 15, 2004; 117(10): 2159 - 2167. [Abstract] [Full Text] [PDF]

				M. Dawson, D. Wirtz, and J. Hanes Enhanced Viscoelasticity of Human Cystic Fibrotic Sputum Correlates with Increasing Microheterogeneity in Particle Transport J. Biol. Chem., December 12, 2003; 278(50): 50393 - 50401. [Abstract] [Full Text] [PDF]

				Y.-K. Ng, X. Lu, A. Gulacsi, W. Han, M. J. Saxton, and E. S. Levitan Unexpected Mobility Variation among Individual Secretory Vesicles Produces an Apparent Refractory Neuropeptide Pool Biophys. J., June 1, 2003; 84(6): 4127 - 4134. [Abstract] [Full Text] [PDF]

				J. Suh, D. Wirtz, and J. Hanes Efficient active transport of gene nanocarriers to the cell nucleus PNAS, April 1, 2003; 100(7): 3878 - 3882. [Abstract] [Full Text] [PDF]

				Y. Tseng, T. P. Kole, and D. Wirtz Micromechanical Mapping of Live Cells by Multiple-Particle-Tracking Microrheology Biophys. J., December 1, 2002; 83(6): 3162 - 3176. [Abstract] [Full Text] [PDF]

				Y. Tseng, B. W. Schafer, S. C. Almo, and D. Wirtz Functional Synergy of Actin Filament Cross-linking Proteins J. Biol. Chem., July 5, 2002; 277(28): 25609 - 25616. [Abstract] [Full Text] [PDF]

				Y. Tseng, K. M. An, and D. Wirtz Microheterogeneity Controls the Rate of Gelation of Actin Filament Networks J. Biol. Chem., May 10, 2002; 277(20): 18143 - 18150. [Abstract] [Full Text] [PDF]

				J. Xu, Y. Tseng, and D. Wirtz Strain Hardening of Actin Filament Networks. REGULATION BY THE DYNAMIC CROSS-LINKING PROTEIN alpha -ACTININ J. Biol. Chem., November 10, 2000; 275(46): 35886 - 35892. [Abstract] [Full Text] [PDF]