In nature, the molecular-recognition ability of peptides and, consequently, their functions are evolved through successive cycles of mutation and selection. Using biology as a guide, it is now possible to select, tailor, and control peptide-solid interactions and exploit them in novel ways. Combinatorial mutagenesis provides a protocol to genetically select short peptides with specific affinity to the surfaces of a variety of materials including metals, ceramics, and semiconductors. In the articles of this issue, we describe molecular characterization of inorganic-binding peptides; explain their further tailoring using post-selection genetic engineering and bioinformatics; and finally demonstrate their utility as molecular synthesizers, erectors, and assemblers. The peptides become fundamental building blocks of functional materials, each uniquely designed for an application in areas ranging from practical engineering to medicine.
The cover shows a fluorescent microscopy image of co‐assembly of streptavidin functionalized quantum dots (SA‐QD) and fluorescein molecules self‐assembled using biotinylated and conjugated quartz binding peptides (QBP‐bio and QBP‐fluorescein). Mehmet Sarikaya and co‐workers describe how inorganic binding peptides can act as universal linkers . Stamping of the QBP‐bio using micro‐contact printing is followed by directed assembly of SA‐QD (red). The QBP‐fluorescein is then immobilized on the bare silica (green) to generate uniform bifunctional micropatterns.
The characteristic of combining liquid behavior with and magnetic properties makes ferrofluids unique and it provides them a variety of applications, in particular in the medial field. For medical application ferrofluids are required to be stable at neutral pH and against high salt concentration. Here we present a new approach to stabilize water-based ferrofluids by using genetically engineered peptides for inorganics (GEPI's). Such GEPI's selected for specific and strong binding to the surface of nanoparticles not only increase colloidal stability by acting as a thin surfactant, but they also enable an efficient route for rendering the ferrofluid bio-functional and bio-compatible. The stability of a ferrofluid was characterized by the ac-susceptibility and by using it in a ferro-microfluidic device. This chip actuates the ferrofluid directly via magnetic fields alone, and the pumping spectrum as a function of frequency reveals information about the size of the magnetic nanoparticles. An ideal ferrofluid with monodisperse particles displays a single and clear pumping peak. Agglomeration can directly be observed as a broadening of the pumping spectrum.
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