Nanomechanics of Desmin Filaments Explored with Optical Tweezers

Abstract

Desmin forms the intermediate filament system of muscle cells where it plays important role in maintaining mechanical integrity and elasticity. Although the importance of intermediate-filament elasticity in cellular mechanics is being increasingly recognized, the molecular basis of desmin's elasticity is not fully understood. In the present work we explored the mechanical properties of purified and reconstituted desmin filaments by using optical tweezers.Desmin, purified from chicken gizzard, was polymerized by the addition of MgCl2. Desmin assembly was monitored by using atomic force microscopy. For mechanical manipulation, desmin filaments were captured between two anti-desmin-coated latex beads, one of which was positioned in a force-measuring optical trap and the other one held and manipulated with a moveable micropipette. By moving the micropipette away from the trap, typically a few-hundred-nanometer section of the captured desmin filament was stretched. Non-linear portions of the elastic curves were fitted with the wormlike-chain model, yielding an average 1 nm apparent persistence length. In the force versus extension curves transitions appeared at 10 pN, which extended the filament by ∼60 nm. This distance corresponds well to unit-length-filament (ULF) dimensions, suggesting that the ULF components of the desmin filament may be rearranged axially upon stretch.Acknowledgement: This study was supported by TAMOP-4.2.1.B-09/1/KMR-2010-0001