Many important cellular interactions involve "weak" interactions, which are difficult to characterize by current techniques. The PI proposes to move into new territory, in terms of directly characterizing these weak intermolecular interactions of biomolecules, by using a technique, Diffusing Colloidal Probe Microscopy (DCPM), developed by the PI's group. The proposal will examine two systems of biological importance, which were also chosen for their significance to biomedical problems: stem-cell based tissue engineering and cancer metastasis. Success in the development of the technique for studying weak biological interactions will have an impact on the understanding of such interactions in cell-cell adhesion, cell migration, tissue morphogenesis, metastasis, immunology, and other cellular processes.
Weak biomolecular interactions, on the order of kT, play an important role in cell-cell adhesion, cell migration, tissue morphogenesis, metastasis, immunology, and other cellular processes. While there are standard mechanical methods for measuring strong interactions (>pN forces), weak interactions are generally measured_ indirectly_ by spectroscopic means. The PI proposes to move into new territory, by directly characterizing these interactions using DCPM, which offers spatial and temporal resolution, statistical significance, and directness not accessible using scanning probes or spectroscopic methods. In essence, DCPM passively monitors Brownian excursions of "diffusing probes" and exploits these natural gauges for time (a2/D), energy (kT), force (fN), and length (nm) when interrogating the interaction of proteins and carbohydrates. This is inherently a nanoscale technique because it harnesses Brownian motion as a useful tool to directly measure kT interactions between proteins rather than avoiding stochastic thermal motion as an undesirable complication of nanoscale systems. Two systems will be studied, CD44-HA interactions and heterophilic cadherin interactions (in the presence of calcium ions) on supported bilayers. The development of DCPM for studying weak biological interactions will have an impact on the understanding of such interactions in cell-cell adhesion, cell migration, tissue morphogenesis, metastasis, immunology, and other cellular processes.
