Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 28: Focus: Charge Effects in Soft and Biological Matter II (joint CPP, BP, ST)

BP 28.4: Talk

Thursday, March 25, 2010, 15:00–15:15, H37

Effective charge of globular proteins and denrimers — Ute Böhme and •Ulrich Scheler — Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, 01069 Dresden

The density of charges on macromolecules is usually so high, that the thermal energy of the respective counterions is insufficient to escape the electric field generated from the charges on the macromolecule. Therefore a fraction of counterions condenses on the macromolecule, lowering the effective charge of the. The combination of diffusion and electrophoresis NMR provides an umambiquous possibility for the experimental determination of the effective charge, which is in good agreement with molecular simulations [1, 2]. This approach has been applied to linear poylelectrolytes as well as proteins and other globular molecules [3]. PAMAM dendrimers exhibit only two types of chargeable groups, therefore counterion condensation can easily be quantified, where the degree of protonation of the amino groups is inferred from proton NMR spectra. At low generations the fraction of condensed counterions increases with increasing molecular weight to level at about 70%. [1] U. Böhme, U. Scheler, Colloids and Surfaces A, 222, (2003), 35 [2] K. Grass, U. Böhme, U. Scheler, H. Cottet, C. Holm, Physical Review Letters 100, (2008) 096104 [3] Ute Böhme, Ulrich Scheler Chemical Physics Letters 435, (2007), 342