ATOMIC-FORCE MICROSCOPY AND MODELING OF NATURAL ELASTIC FIBRILLIN POLYMERS

A central issue in the understanding of Marfan syndrome deals with the functional architecture of fibrillin-containing microfibrils. Fibrill in-rich microfibrils are long extracellular matrix fibrillar component s exhibiting a 50 nm periodic beaded-structure with a width of around 20-25 nm after rotary shadowing and a 10-12 nm diameter when observed in ultra-thin sections. They are composed of fibrillin monomers more o r less associated with many other components which are, for the most p art, poorly characterized up to date. They are known to be elastic but few data have been accumulated to understand their properties. Atomic force microscopy (AFM) allowed us to morphologically differentiate fi brillin-rich microfibrils from other fibrillar components and to inves tigate the thin structure of these beaded filaments in their native st ate. They showed, in AFM, a periodic beaded structure ranging from 50 to 60 nm and a width of about 40 nm. The different sizes of fibrillin- containing microfibrils previously observed after rotary shadowing and in ultra-thin sections was resolved with our technique and is reveale d to be 10 nm in diameter. Each beaded microfibril appears to be compo sed of heterogeneous beads connected by 2-3 arms. An orientation of th e microfibrils has been shown, and allows us to propose a complementar y model of microfibrillar monomer association. ((C) Elsevier, Paris).