Orientation modulation of a synthetic polypeptide in self-assembled monolayers: a TOF-SIMS study

J Am Chem Soc. 2003 Jul 23;125(29):8911-5. doi: 10.1021/ja0210749.

Abstract

Structure and orientation of molecules are key properties of functionalized surfaces. Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), here we investigate how to modulate these parameters upon the immobilization process varying the conditions of self-assembly. The molecule of interest, a template-assembled synthetic protein (TASP), consists of a central peptide ring with orthogonally arranged residues. Thioalkane chains allow the directed self-assembly of the molecule on a gold surface; four serine residues on the opposite side of the ring can be used as anchoring sites for various functional sensing molecules. The TASP conformation and its orientation in self-assembled monolayers (SAMs) play a central role for the accessibility of these serine residues. To study the influence of the self-assembly conditions, two series of samples were prepared. Pure TASP monolayers of different surface densities are compared to mixed TASP/alkanethiol monolayers prepared by sequential adsorption varying sequence and particular incubation times as well as by coadsorption modifying incubation times and TASP/alkanethiol mass ratios. Switching the TASP orientation from a state where the molecules are lying flat on the surface to an upright orientation turned out to be possible by inserting the TASP into a preformed alkanethiol monolayer of an appropriate surface density. This study demonstrates that TOF-SIMS is an excellent tool not only to investigate the surface composition, but also the molecular structure of functionalized surfaces.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Mass Spectrometry / methods
  • Peptides / chemical synthesis
  • Peptides / chemistry*
  • Peptides, Cyclic / chemical synthesis
  • Peptides, Cyclic / chemistry
  • Sulfhydryl Compounds / chemical synthesis
  • Sulfhydryl Compounds / chemistry

Substances

  • Peptides
  • Peptides, Cyclic
  • Sulfhydryl Compounds