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The European Physical Journal E

, Volume 12, Issue 2, pp 255–264 | Cite as

Stability of dense hydrophobic-polar copolymer globules: Regular, random and designed sequences

  • E. N. Govorun
  • A. R. Khokhlov
  • A. N. Semenov
Article

Abstract.

Stability of dense globular structures formed by amphiphilic copolymers consisting of hydrophobic (insoluble) units and a small fraction of single polar (soluble) monomer units is considered in the mean-field approximation for different types of unit distributions along the chain. Polar (P) units are located in a relatively thin surface layer due to their strong repulsion from hydrophobic (H) monomer units. We compared globules formed by different copolymer sequences with the same gross numbers of P- and H-units: regular HP-sequences (P-units separated by equal H-blocks), random copolymers (uncorrelated positions of P-units, i.e. Flory distribution of H-block lengths), proteinlike (PL) sequences (designed sequences involving both long H-blocks dominating by total mass, and short blocks dominating by number). We showed that PL-globules are more stable (lower free energy) and are characterized by a higher temperature of the coil-to-globule transition when compared with the other sequences mentioned above. We also considered HP-H-copolymers consisting of one long and many short hydrophobic blocks; we showed that it is these sequences that yield the dense globules corresponding to the lowest free energy.

Keywords

Free Energy Surface Layer Total Mass Monomer Unit Random Copolymer 

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Copyright information

© Springer-Verlag Berlin/Heidelberg 2003

Authors and Affiliations

  • E. N. Govorun
    • 1
  • A. R. Khokhlov
    • 1
    • 2
  • A. N. Semenov
    • 1
    • 3
  1. 1.Physics DepartmentMoscow State UniversityMoscowRussia
  2. 2.Polymer ScienceUniversity of UlmUlm Germany
  3. 3.Institut Charles SadronStrasbourg CedexFrance

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