Evidence for Sodium Dodecyl Sulfate/Protein Complexes Adopting a Necklace Structure

Montserrat Samsó, Joan‐Ramon ‐R Daban, Steen Hansen, Gareth R. Jones

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Structural analysis by cryo‐electron microscopy and small‐angle X‐ray scattering of ten sodium dodecyl sulfate/protein complexes in 25 mM Tris/HCl, 0.192 M glycine, pH 8.3, showed necklace‐like structures of spherical micelles dispersed along the unfolded peptide chain. The micelles of most SDS/protein complexes had a constant diameter (≈ 6.2nm), slightly larger than pure SDS micelles (≈ 5.7 nm), all micelles possessing a degree of surface roughness. The micelle‐associated polypeptide is mostly situated at the interface of the sulfate head groups and hydrocarbon core, intruding into the core rather than outward from the surface. Proteins with a molecular mass less than about 20 kDa formed complexes with a single SDS micelle. Multi‐micellar SDS/protein complexes had centre‐to‐centre intermicellar distances in the range 7.0–12.0 nm. Our findings on the constancy of micellar size, number of micelles/complex, and the relationship between the degree of occupancy of micelles and a polypeptide's molecular mass, have enabled us to speculate on the correlation between the electrophoretic mobility of a polypeptide in SDS/PAGE and its molecular mass. The anomalous electrophoretic behaviour observed for the sodium dodecyl sulfate/histone H5 complex is accounted for by the large micelle of its complex. Copyright © 1995, Wiley Blackwell. All rights reserved
Original languageEnglish
Pages (from-to)818-824
JournalEuropean Journal of Biochemistry
Issue number3
Publication statusPublished - 1 Jan 1995


  • electron microscopy
  • maximum entropy
  • proteiddetergent complexes
  • X‐ray scattering


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