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BP: Fachverband Biologische Physik

BP 6: Biopolymer Conformation and Dynamics

BP 6.5: Vortrag

Montag, 26. März 2007, 15:30–15:45, H44

Conformation control of plasmid DNA on a solid substrate — •Wei Zhuang, Hua Liang, Nikolai Severin, and Jürgen P. Rabe — Institut für Physik, Humboldt University Berlin, Berlin, Germany

The conformation of single DNA molecules may be controlled by stretching them with optical tweezers [1] or an scanning force microscope (SFM) probe [2]. In recent work it has been demonstrated that a highly oriented pyrolytic graphite (HOPG) surface coated by self-assembled alkylamine amphiphiles can serve as a substrate on which single DNA molecules can be manipulated by an SFM probe [3]. A disadvantage of the above mentioned techniques is that they have to be applied to one molecule at a time. Here we describe a preparation of an amphiphile coated HOPG surface, on which the conformation of plasmid DNA can be fully controlled across the whole surface. By varying the concentration of amphiphiles on the surface, plasmid DNA molecules exhibit different conformations ranging from supercoiling, relaxed open circle, to overstretching. Particularly, when DNA molecules are adsorbed on 60% amphiphile sub-monolayer covered HOPG, upon mild annealing the DNA molecules can be overstretched up to 1.5 times of their B-form length due to steric repulsion between adjacent alkyl chains. It is suggested that a fully screened amphiphile-DNA complex is formed on the surface. The spontaneous overstretching of many DNA molecules at a time may become useful for the development of a fast processing genomic analysis chip. 1. S.B.Smith, et. al Science 271 (1996) 795 2. M.Rief, et. al Nat. Struct. Biol. 6 (1999) 346 3. N.Severin, et. al Nano Lett. 4 (2004) 577