Regensburg 2010 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 13: Nanoparticles and Viruses
BP 13.8: Vortrag
Dienstag, 23. März 2010, 16:15–16:30, H45
Swelling and softening of the CCMV plant virus capsid in response to pH shifts — •Bodo D. Wilts1, Iwan A.T. Schaap1, Chris C. Broomell2, Charles M. Knobler3, and Christoph F. Schmidt1 — 1III. Physikalisches Institut, Georg-August-Universität Göttingen, Germany — 2Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT, USA — 3Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA, USA
Previous research on cowpea chlorotic mottle viruses (CCMV) has revealed a swelling transition and a softening of the protein capsid in response to a pH increase. In this study, we have performed nano-indentation experiments using an atomic force microscope and tested the shell response from low (4.8) up to high pH (7.5) in the absence of divalent ions. We could, for the first time, study the elastic behavior of the swollen virions. Indentations were performed in the reversible linear regime with indentation forces up to 200 pN. The results show a gradual swelling transition of the RNA-filled capsids preceded by a softening of the shell as a function of pH. Control measurements with the empty capsid and a salt-stable mutant revealed that the softening is not directly coupled to the swelling of the protein shells. Instead we hypothesize that the softening of the CCMV virions is triggered by pH-dependent opening of bonds within the protein shell which may be necessary, but not sufficient for swelling.