Andrew Marcus

Associate Professor of Chemisty

B.A., University of California;
Ph.D., Stanford University

Member of:
• Institute of Molecular Biology
• Materials Science Institute

Research Interests

The Marcus group studies the dynamics of complex systems. These include the motions of biological and synthetic macromolecules in polymer melts, blends, and living biological cells. All of these systems are multi-component macromolecular fluids where the macroscopic behavior depends on the details of the underlying molecular fluctuations. In these systems, relaxations often occur over several decades in time and exhibit an interesting dependence on spatial scale, related to the mechanism of molecular interactions.

Because molecular fluctuations are difficult to study by conventional methods, a significant component of our research is devoted to the development of new optical techniques. Fourier imaging correlation spectroscopy (FICS), is a new method that we developed to study the motions of intracellular species in cellular compartments and synthetic macromolecules in polymer liquids. FICS is a sensitive spatially selective method to determine the distribution of density fluctuations from fluorescently labeled species. The ability of FICS to determine distribution functions of parameters that depend on molecular coordinates distinguishes it from conventional spectroscopies that determine the ensemble average values of the same parameters. We are using FICS in combination with single-molecule-imaging techniques to study cytoskeletal-assisted dynamics of mitochondria, protein transport in bacteria, and molecular diffusion in polymer melts.

Another interest is the development of ultra-fast non-linear spectroscopic methods to study the dynamics of excited states in molecules and how they interact with their local environments. In collaboration with Profs. Jeff Cina and Tom Dyke, we are developing a multi-dimensional four-pulse electronic spectroscopy to study the dynamics of vibrational wave-packets on the excited state electronic potential energy surfaces of coupled chromophore systems. We are using this approach to study excited state dynamics, including fluorescence resonance energy transfer (FRET), in a variety of synthetic and biological systems.

Understanding Complexity in Polymer, Colloid, and Bio-Membrane Materials

The research carried out in the Marcus group aims to achieve an improved understanding of the physical properties of polymer, colloid, and bio-membrane materials. These are complex (often multicomponent macromolecular) fluid systems, where mechanical and thermodynamic behavior depends on the myriad ways in which molecules (or particles) can pack and move relative to one another. Our goal is to shed light on fundamental structure- function relationships by studying material properties in terms of the underlying microscopic fluctuations that give rise to them. Specific attention is devoted to explore the influence of particle shape, symmetry, surface interactions, and composition (in the case of polymer blends).

Of particular interest is the behavior of macromolecular systems restricted to confined spaces. When one of the dimensions of a complex fluid is made to be as small as the length scale for which short range order normally occurs, the isotropy of the liquid is perturbed. Molecular fluctuations that occur uniquely at the interface can induce entirely new phases that are not observed in the unconfined fluid state. An example is the appearance of an equilibrium ÔhexaticÕ phase, with quasi-long-range orientational order and short-range translational order, in a monolayer suspension of uncharged sterically stabilized poly(methylmethacrylate) spheres. [See Marcus, et al., Phys. Rev. Lett., 77, 2577 (1996); Marcus, et al., Phys. Rev. E 55, 637 (1997).] Mechanical properties are also dramatically affected by confinement. The microscopic origin of the onset of solid-like behavior (crystallization verses glass formation) with decreasing film thickness is currently being studied in thin colloidal suspensions and thin film binary polymer blends. A second aspect of our work involves the development of new, highly sensitive, instrumental techniques specialized in the detection of optical signals from volumes that are very small or narrow. For thin film systems, it is necessary to have techniques that are sensitive enough to detect microscopic structure, and the time-dependent evolution of structure, from samples that give very little signal. To this end, we combine powerful features of optical microscopy with linear and non-linear laser spectroscopy to directly probe particle fluctuations (in some cases, single molecule fluctuations) in thin film or membrane samples. These experiments are designed to be spatially and temporally selective over many decades and serve to quantify the microscopic dynamic structure. Additional information is obtained by using con-focal microscopy to record sequences of images of particles (or fluorescence from single molecules).

These images are digitized and analyzed using computer algorithms to yield microscopic trajectories. The information contained in pre-averaged trajectories allows us to correlate microscopic processes with observed macroscopic phenomena. The connection between microscopic and macroscopic behavior can be bridged using a variety of statistical mechanical models for complex fluid dynamics. Because microscopic measurements contain more information than do measurements of bulk quantities alone, our analyses provide rigorous tests of the validity of any particular theoretical description.

Selected Publications

Tekavec PF, Dyke TR, Marcus AH. Abstract Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation. J Chem Phys. 2006 Nov 21;125(19):194303.

Fink M. C., Adair K. V., Guenza M. G., and A. H. Marcus. (2006) Translational diffusion of fluorescent proteins by molecular Fourier imaging correlation spectroscopy. Biophys. J., 91 (9): 3482-98

Knowles M. K., Honerkamp-Smith A. R., and A. H. Marcus. (2005) Direct  measurement of relative and collective diffusion in a dilute binary  colloidal suspension. J. Chem. Phys. 2005 Jun 15; 122 (23): 234909

Knowles M.K., M.G. Guenza, R.A. Capaldi, and A.H. Marcus. (2002) Cytoskeletal-assisted dynamics of the mitochondrial reticulum in living cells. PNAS 99:14772-7.

Knowles, M. K.; Margineantu, D.; Capaldi, R. A.; Marcus, A. H. Translational Dynamics of Fluorescently Labeled Species by Fourier Imaging Correlation Spectroscopy, in Liquid Dynamics: Experiment, Simulation, and Theory. Pgs. 58 – 70. ACS Symposium Series 820 (American Chemical Society: Washington DC, 2002)

Margineantu, D.; Brown, R. M.; Brown, G. K.; Marcus, A. H.; Capaldi, R. A. Heterogeneous Distribution of Pyruvate Dehydrogenase in the Matrix of Mitochondria. Mitochondrion 2001, 1, 327 – 338.

Grassman, T.J., M.K. Knowles, and A.H. Marcus (2000) Structure and Dynamics of Fluorescently Labeled Complex Fluids by Fourier Imaging Correlation Spectroscopy. Physical Review E 62:8245-57.

Knowles, M.K., T.J. Grassman, and A.H. Marcus (2000) Measurement of the Dynamic Structure Function of Fluorescently Labeled Complex Fluids by Fourier Imaging Correlation Spectroscopy. Physical Review Letters 85:2837-40.

Margineantu, D., R.A. Capaldi, and A.H. Marcus (2000) (journal cover article) Dynamics of the Mitochondrial Reticulum Live Cells using Fourier Imaging Correlation Spectroscopy and Digital Video Microscopy. Biophysical J. 79:1833-49.
See also J.M. Schurr (2000) (editorial comment) Molecular Motions in Fourier Transform Space. Biophysical J. 79:1692-4.

Marcus, A.H., J. Schofield, and S.A. Rice (1999) Experimental Observations of Non-Gaussian Behavior and Stringlike Cooperative Dynamics in Concentrated Quasi-Two-Dimensional Colloidal Liquids. Physical Review E 60:5725-36.

Chung-Ming Tam, M., S.A. Rice, and A.H. Marcus (1998) Unusual Structure in a Quasi-Two-Dimensional Binary Colloidal Fluid. Chemical Physics Letters 294:217-22.

Marcus, A.H., and S.A. Rice (1997) Phase Transitions in a Confined Quasi-Two-Dimensional Colloid Suspension. Physical Review E 55:637-56.

Schofield, J., A.H. Marcus, and S.A. Rice (1996) The Dynamics of Quasi-Two-Dimensional Colloidal Systems. Chem. Phys. J. 100:18950-61.

Marcus, A.H., and S.A. Rice (1996) Observation of First Order Liquid-to-Hexatic and Hexatic-to-Solid Phase Transitions in a Confined Colloid Suspension. Physical Review Letters 77:2577-80.

Marcus, A.H., B. Lin, and S.A. Rice (1996) Self-Diffusion in Dilute Quasi-Two-Dimensional Hard Sphere Suspensions: Evanescent Wave Dynamic Light Scattering and Video Microscopy Studies. Physical Review E 53:1765-76.

Marcus, A.H., T. Morkved, H. Jaeger, S.A. Rice, D.M. Hussey, N.A. Diachun, and M.D. Fayer (1996) Chromophore-Rich Nanodomains in Bulk and Ultra Thin Film Polymer Blends. Molecular Crystals and Liquid Crystals 283:31-5.

Leezenberg, P.B., A.H. Marcus, M.D. Fayer, and C.W. Frank (1996) Rotational Dynamics of Naphthalene-Labeled Cross-link Junctions in Poly(dimethylsiloxane) Elastomers. Chem. Phys. J. 100:7646-55.

Marcus, A.H., D.M. Hussey, N.A. Diachun, and M. D. Fayer (1995) Nanodomain Formation in a Liquid Polymer Blend: the Initial Stages of Phase Separation. Chem. Phys. J. 103:8189-201.

Marcus, A.H., M.D. Fayer, and J.G. Curro (1994) Intermolecular Structure in a Single Component Polymer Glass: Towards High Resolution Measurements of the Side Chain Pair Correlation Function. Chem. Phys. J. 100:9156-69.

Diachun, N.A., A.H. Marcus, and M.D. Fayer (1994) Dynamics in Polydimethylsiloxane: The Effect of Solute Polarity. Amer. Chem. Soc. J. 116:1027-32.

Finger, K.U., A.H. Marcus, and M.D. Fayer (1994) Structure of Complex Systems using Electronic Excitation Transport: Theory, Monte Carlo Simulations, and Experiments on Micelle Solutions. Chem. Phys. J. 100:271-86.

Marcus, A.H., N.A. Diachun, and M.D. Fayer (1993) Intermolecular Structure in a Polymer Glass: Electronic Excitation Transfer Studies. Macromolecules 26:3041-8.

Quitevis, E.L., A.H. Marcus, and M.D. Fayer (1993) Dynamics of Ionic Lipophilic Probes in Micelles: Picosecond Fluorescence Depolarization Measurements. Chem. Phys. J. 97:5762-9.

Marcus, A.H., N.A. Diachun, and M.D. Fayer (1992) Electronic Excitation Transfer in Concentrated Micelle Solutions. Chem. Phys. J. 96:8930-7.

Stein, A.D., D.A. Hoffmann, A.H. Marcus, P.B. Leezenberg, C.W. Frank, and M.D. Fayer (1992) Dynamics in Poly(dimethylsiloxane) Melts: Fluorescence Depolarization Measurements of Probe Chromophore Orientational Relaxation. Chem. Phys. J. 96:5255-63.

Marcus, A.H., and M.D. Fayer (1991) Electronic Excitation Transfer in Clustered Chromophore Systems: Calculations of Time-Resolved Observables for Intercluster Transfer. Chem. Phys. J. 94:5622-30.

Marcus, A.H., TF. Molinski, E. Fahy, D.J. Faulkner, C. Xu, and J. Clardy (1989) 5-Isothiocyanatopupukeanane from a Sponge of the Genus Axinyssa. Organic Chem. J. 54:5184.

Zabriskie, T.M., J.A. Klocke, C.M. Ireland, A.H. Marcus, T.F. Molinski, D.J. Faulkner, C. Xu, and J. Clardy (1986) Jaspamide, a Modified Peptide from a Jaspis Sponge, with Insectisidal and Antifungal Activity. Amer. Chem. Soc. J. 108:3123.