Cell and Tissue Mechanics. During tissue development and wound healing, cells remodel the extracellular matrix (ECM) that surrounds them. Similar remodeling occurs in model tissues reconstituted in vitro from cells and ECM. Both as basic science and for tissue engineering it is important to understand the mechanisms of remodeling. We can use this understanding to produce tissue equivalents that mimic the structural and mechanical properties of authentic biological tissues. These tissue models can be used to study both normal and pathological cellular and tissue mechanical functions, e.g., regulation of myosin-dependent contractile force in smooth and cardiac muscle and nonmuscle cells by agonists binding to cell surface receptors as well as by interactions with ECM that trigger changes of cellular contractile force. Measurements of force in reconstituted tissues provide an assay to study the signaling pathways that regulate myosin activity (collaboration with R. Wysolmerski, Department of Pathology, St. Louis University). We also measure the mechanical properties of tissue constructs to develop structural models of cell and tissue mechanics.

Fluctuation Spectroscopy. We use Fluorescence Correlation Spectroscopy (FCS) and photobleaching recovery to study transport and molecular interactions in a variety of systems. These include interactions among proteins in cells, e.g., actin filaments with capping protein or the Arp2/3 complex and between collagen fibrils and collagenase molecules (collaboration with G. Goldberg, Department of Dermatology). We are also using FCS to study conformational transformations of proteins (collaboration with C. Frieden, Department of Biochemistry and Molecular Biophysics).

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