Quantum-dot immobilization DOI: 10.1002/smll.200600070 Materials Specificity and Directed Assembly of a Gold- Binding Peptide Candan Tamerler, Memed Duman, Ersin Emre Oren, Mustafa Gungormus, Xiaorong Xiong, Turgay Kacar, BabakA. Parviz, and Mehmet Sarikaya* Adsorption studies of a genetically engineered gold-binding peptide, GBP1, were carried out using a quartz-crystal microbalance (QCM) to quantify its molecular affinity to noble metals. The peptide showed higher adsorption onto and lower desorption from a gold surface compared to a platinum substrate. The material specificity, that is, the preferential ad- sorption, of GBP1 was also demonstrated using gold and platinum mi- cropatterned on a silicon wafer containing native oxide. The biotinylated three-repeat units of GBP1 were preferentially adsorbed onto gold regions delineated using streptavidin-conjugated quantum dots (SAQDs). These experiments not only demonstrate that an inorganic-binding peptide could preferentially adsorb onto a metal (Au) rather than an oxide (SiO 2 ) but also onto one noble metal (Au) over another (Pt). This result shows the utility of an engineered peptide as a molecular erector in the directed immobilization of a nanoscale hybrid entity (SAQDs) over selected regions (Au) on a fairly complex substrate (Au and Pt micropat- terned regions on silica). The selective and controlled adsorption of inorganic-binding peptides may have significant implications in nano- and nanobiotechnology, where they could be genetically tailored for specific use in the development of self-assembled molecular systems. Keywords: · cross-specificity · directed assembly · peptide binding · protein engineering · quantum dots 1. Introduction Biological materials are formed via the templating of proteins that may control nucleation, morphogenesis, and the synthesis of hard tissue such as the skeletons of single- and multi-celled organisms with complex architectures. [1–3] The biological processes through which organisms control and monitor tissue formation are due to the molecular rec- ognition and the self- and co-assembly of proteins with inor- ganic materials that are involved in biomineralization; or- ganisms acquire these characteristics through millions of years of evolution. [3] Biogenic materials, such as metals (gold, silver, etc.), ceramics (silica, hydroxyapatite, calcite, aragonite, and magnetite), and semiconductors (cadmium sulfide and iron sulfide), of different physical properties, for example, mechanical, electronic, optical, and magnetic, are fabricated under mild conditions of neutral pH, ambient [*] Prof. C. Tamerler, M. Duman, Dr. E. E. Oren, M. Gungormus, T. Kacar, Prof. M. Sarikaya Materials Science & Engineering Department Roberts Hall, Box: 352120 University of Washington Seattle, WA 98195 (USA) Fax:(+ 1)206-543-3100 E-mail: sarikaya@u.washington.edu Prof. C.Tamerler, M. Gungormus, T. Kacar Molecular Biology & Genetics Istanbul Technical University Maslak 80626, Istanbul (Turkey) X. Xiong, Prof. B. A. Parviz Electrical Engineering Department, University of Washington Seattle, WA 98195 (USA) 1372 # 2006 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim small 2006, 2,No.11,1372–1378 full papers M. Sarikaya et al. S PECIAL S ECTION