Fluorescence correlation spectroscopy shows that monomeric polyglutamine molecules form collapsed structures in aqueous solutions

Scott L. Crick, Murali Jayaraman, Carl Frieden, Ronald Wetzel, Rohit V. Pappu

Research output: Contribution to journalArticlepeer-review

200 Scopus citations

Abstract

We have used fluorescence correlation spectroscopy measurements to quantify the hydrodynamic sizes of monomeric polyglutamine as a function of chain length (N) by measuring the scaling of translational diffusion times (τD) for the peptide series (Gly)-(Gln)N-Cys-Lys 2 in aqueous solution. We find that τD scales with N as τoNν and therefore ln(τD) = ln(τo) + νln(N). The values for ν and ln(τo) are 0.32 ± 0.02 and 3.04 ± 0.08, respectively. Based on these observations, we conclude that water is a polymeric poor solvent for polyglutamine. Previous studies have shown that monomeric polyglutamine is intrinsically disordered. These observations combined with our fluorescence correlation spectroscopy data suggest that the ensemble for monomeric polyglutamine is made up of a heterogeneous collection of collapsed structures. This result is striking because the preference for collapsed structures arises despite the absence of residues deemed to be hydrophobic in the sequence constructs studied. Working under the assumption that the driving forces for collapse are similar to those for aggregation, we discuss the implications of our results for the thermodynamics and kinetics of polyglutamine aggregation, a process that has been implicated in the molecular mechanism of Huntington's disease.

Original languageEnglish
Pages (from-to)16764-16769
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number45
DOIs
StatePublished - Nov 7 2006

Keywords

  • Chain collapse
  • Poor solvent

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