Early stage mineralization of extracellular matrix proteins probed at the nanoscale by synchrotron imaging methods

Note: Pizza served at 11:45 AM
Speaker: Elaine DiMasi, NSLS, Brookhaven National Laboratory

When: October 23, 2009 (Fri), 12:00PM to 01:00PM (add to my calendar)
Location: SCI 352
Hosted by: Ophelia Tsui

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract:
We are studying biological mineralization and its control by the protein matrix that exists in tissue such as bone. Biominerals are organized over a hierarchy of length scales, and their formation remains a fascinating unsolved problem important for technology and medicine.
Extracellular matrix (ECM) proteins are part of the puzzle. The proteins themselves self-assemble to form structures that affect mineralization and also provide feedback to mineralizing cells such as osteoblasts. We present a model system of ECM proteins, which form micron-scale fibers arranged in a mesh of 10 micron scale.
Using scanning probe microscopy to measure the elastic properties, we show that different ECM proteins thicken and stiffen to different extents when mineralized in-vitro with calcium phosphate. This is evidence of mineralization, probed at very early growth stages before mineral particles can be imaged by electron microscopy or detected with synchrotron x-ray diffraction. To discover the location and atomic coordination of Calcium in these early-stage mineralized ECMs, we use soft x-ray transmission microscopy at the synchrotron source. In this measurement a 50-nm soft x-ray beam is used to obtain a spatially resolved map of Ca in the proteins.

We will also discuss the state of the art in synchrotron imaging of biominerals, pointing out new directions and making an appeal for involvement of a larger user base – and a larger funding base! Such methods can and should continue to be extended to other composite materials.