Size and shape determination of proteins in solution by a noninvasive depolarized dynamic light scattering instrument

Naomi Chayen, Matthias Dieckmann, Karsten Dierks, Petra Fromme

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Dynamic light scattering (DLS) is a well-known noninvasive technique for investigating interactions of protein molecules in solution. Unfortunately, DLS is not very sensitive to small size changes because covariables, such as temperature, viscosity, and refractive index, are not precisely known, or they vary as functions of an experiment run, making it difficult to resolve subtle size changes of only a few Angström. It is usually not possible, if these covariables are not systematically measured and brought into the DLS analysis, to separate monomers from dimers when both are present in solution. We present here measurements with a variant of DLS that determines rotational diffusion as well as translation diffusion. This technique, called depolarized dynamic light scattering (DDLS) is, like DLS, also an old method, but it is rarely used due to enormous practical difficulties. However, we have found that a combination of DLS with DDLS is very promising, because it allows for a rough shape determination of the molecule under study and it is more sensitive to subtle size changes. We built an instrument that overcomes some of the difficulties, and report measurements made with this instrument. One of the samples was Photosystem-I, a membrane protein for photosynthesis. Its dimensions were determined to be 9.6 nm thick and 26 nm in diameter, values that are in good agreement with the dimensions obtained from X-ray diffraction analysis of single crystals.

Original languageEnglish (US)
Pages (from-to)20-27
Number of pages8
JournalAnnals of the New York Academy of Sciences
Volume1027
DOIs
StatePublished - Jan 1 2004

Keywords

  • Depolarized scattering
  • Dynamic light scattering
  • Particle sizing
  • Shape determination

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • History and Philosophy of Science

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