Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Biological Systems

CPP 14.7: Talk

Tuesday, March 27, 2007, 11:45–12:00, H47

Mechanical Properties of Polypeptide by using Atom Force Microscopy — •Kaitian LI, Jens Hentschel, Hans Börner, and Andreas Fery — Max-Planck-Institut für Kolloid und Grenzflächen, Am Mühlenberg 14424 Potsdam

Helical, tube- or tape-like structures formed by peptide self aggregation are a common motive found in biological systems. In this work, we explore the mechanical properties of such tubular aggregates formed from well defined synthetic block-copolymers, which consist of a peptide block which triggers self aggregation and conventional polymeric blocks. The amino acid sequence of the peptide encodes a high tendency to adopt an antiparallel β-sheet motif, and thus programs the formation of tapelike microstructures. The helical superstructures undergo defined entanglement to form superhelices. A twisted two-dimensional core-shell tape is proposed as a structure model, in which the peptide segments form an antiparallel β-sheet with a polymer shell. [1] Here, we discovered that the resulting helical superstructures, when deposited on a substrate, are 2.9 nm high, 10 nm wide, and up to 2.3 μm long. We also try to measure their mechanical properties, which we directly measured through indentation type experiments using atomic force microscopy. We find that these structures which on the silicon substrate are deucedly soft and flexible. They could easily be deformed even by soft cantilever (K~0.05). From the averaged point we can have a correspondingly Young*s modulus as calculated by finite element analysis. We also plan test their bending elasticity by using a novel AFM based approach.