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Surface Potentials in Langmuir Mono layers of Unidirectionally Oriented alpha-Helical Diblock Copolypeptides

Nguyen, L-T. T., Ardana, A., ten Brinke, G. & Schouten, A. J., 4-May-2010, In : Langmuir. 26, 9, p. 6515-6521 7 p.

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  • Le-Thu T. Nguyen
  • Aditya Ardana
  • Gerrit ten Brinke
  • Arend J. Schouten

The surface potentials and effective dipole moments of alpha-helical amphiphilic diblock copolypeptides during monolayer compression at the air water interface are reported. Amphiphilic diblock copolypeptides (PLGA-b-PM LGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and poly(gamma-methyl-L-glutamate-ran-gamma-stearyl-L-glutamate) with 30 mol% of stearyl substituents (PMLGSLG) of various block lengths were studied during the double-brush formation process at the water surface. Upon monolayer spreading of PLGA-b-PMLGSLGs, surface potentials of hundreds of millivolts were recorded, attributed to the dipole moments of water molecules reorienting due to interactions with the monolayers. Upon compression, the effective dipole moments derived from the surface potentials of the PLGA-b-PMLGSLG monolayers decrease gradually, most likely as a result of the immersion of the hydrophilic block in water and cancellation of the interactions between the hydrophobic block and the underlying water molecules. The polypeptide macrodipole moment immersed in water was apparently effectively screened out. The remaining effective dipole moment of the monolayer contributes mainly to the hydrophobic block, and upon tilting away from the water surface toward the surface no it was found to increase with the hydrophobic block length, indicating the gradual formation of unidirectional aligned polypeptide molecules in the double-brush monolayer.

Original languageEnglish
Pages (from-to)6515-6521
Number of pages7
JournalLangmuir
Volume26
Issue number9
Publication statusPublished - 4-May-2010

    Keywords

  • AIR-WATER-INTERFACE, SELF-ASSEMBLED MONOLAYERS, REACTION ALIGNMENT FILM, ELECTRON-TRANSFER, CONTROLLABLE ORIENTATION, MOLECULAR-ORIENTATION, LIQUID-CRYSTAL, POLYPEPTIDES, PEPTIDES, DIPOLE

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