Cytochrome c self-assembly on alkanethiol monolayer electrodes as characterized by AFM, IR, QCM, and direct electrochemistry

Koji Nakano, Tadateru Yoshitake, Yasunori Yamashita, Edmond F. Bowden

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)

Abstract

With the advantage of carbodiimide coupling chemistry, horse heart cytochrome c (cyt c) has been covalently immobilized onto self-assembled monolayers (SAMs) from 11-mercaptoundecanoic acid (MUDA) developed on single-crystal or polycrystalline gold substrate surfaces. The cyt c immobilized substrates thus prepared have been characterized by atomic force microscopy (AFM); we have succeeded in obtaining surface topographical images down to single-protein resolution. AFM imaging has also shown densely packed, uniform protein monolayer formation that is highly suggestive of self-assembly of cyt c molecules on MUDA SAMs. Covalent attachment of cyt c has been further evidenced by reflection-absorption FT-IR as well as microgravimetric analysis using a quartz crystal microbalance (QCM). In the latter, the specific MUDA and cyt c surface concentrations were determined to be 0.86 ± 0.11 nmol cm -2 (n = 5) and 28 ± 12 pmol cm-2 (n = 5), both of which agree fairly well with their theoretical counterparts. The obtained QCM chips having the cyt c/MUDA/Au interfacial structure were found to be capable of the direct electrochemistry of the surface-attached cyt c molecules. Cyclic voltammetric measurements on the chips gave particular redox waves showing characteristics of surface process. The electroactive protein surface concentration was determined to be 7.2 ± 4.8 pmol cm-2 (n -6); it was almost consistent with values found in literature, while it was limited to 26% in magnitude for the QCM data. This was deemed to have arisen from the orientation variation of the surface-confined cyt c molecules and is discussed briefly.

Original languageEnglish
Pages (from-to)6270-6275
Number of pages6
JournalLangmuir
Volume23
Issue number11
DOIs
Publication statusPublished - May 22 2007

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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