198 INDUSTRIAL BIOTECHNOLOGY FALL 2005 ORIGINAL RESEARCH Shi-You Ding 1 *, Steven Smith 1 , Qi Xu 1 , Junji Sugiyama 2 , Marcus Jones 1 , Garry Rumbles 1 , Edward A. Bayer 3 , and Michael E. Himmel 1 * 1 National Bioenergy Center Basic Sciences Center National Renewable Energy Laboratory, Golden, CO 80401 2 Research Institute of Sustainable Humanosphere Kyoto University Gokanosho, Uji, Kyoto 611-0011, Japan 3 Weizmann Institute of Science Dept. of Biological Chemistry Rehovot 76100, Israel *Corresponding authors Shi-You Ding Phone (303) 384 7758, Fax (303) 384 7752, E-mail: shi_you_ding@nrel.gov Michael E. Himmel Phone: (303) 384 7756, Fax (303) 384 7752, E-mail mike_himmel@nrel.gov Abstract We are working toward validating the concept of using natural and/or recombinant biomacromolecules to build quantum dot (QD)–protein conjugates into arrays with highly controlled geome- tries. Our ultimate objective is to study energy-transfer phenomena between photon-energized QDs and other nanoparticles or surfaces. We have employed the unique cellulosomal cohesion/dockerin inter- action to build self-assembled protein polymers. This protein poly- mer in turn binds to native cellulose nanofibrils through the highly selective polysaccharide-recognizing properties of cellulose-binding module (CBM). The recombinant protein monomer also contained a Strep Tag-II peptide which functions as a linker to force-directed interaction of the protein monomer with the biotinylated QDs through the intermediary streptavidin (protein tetramer). Biotinylated QDs were thus assembled on a rigid template (cellulose crystal) using cellulosomal chimera and streptavidin conjugates. Fluorescence, atomic force, and transmission electron microscopy were used to characterize the properties of these controlled QD-protein-cellulose arrays. We noted a dramatic effect observable in real time: the “blinking” of QDs that were more remotely located on a cellulose strand. QDs grouped in closer proximity do not blink but emit steadily when viewed by eye. An analysis of the periodicity of the blinking behavior was performed by tracking the energized pixels from the high-resolution digital image as a function of time. We also meas- ured the amplitude and cycle characteristics of these blinking, lone QDs and are currently comparing this observation with theory. We believe that such novel nanoscale moieties, namely, quantum dots coupled to self-assembling protein scaffolded on cellulose, can be effectively engineered. Introduction e are today only in the initial phases of exploiting the potential of nanometer-scale systems. The bottom-up approach for nanofabrication proposes to overcome the limitations of traditional top-down lithographic techniques by relying on the self-organization of molecular building blocks into higher-order assemblies having a desired configura- tion 1,2 . This organization of modules or components requires precise templating, which is challenging at the nanometer scale. In this context, a variety of molecular building blocks with programmed noncovalent recognition sites have been designed and produced by organic syn- thesis. Using the evolutionary process, nature has been working on nanoscale self-assembly for hundreds of millennia, with unquestion- Ordered arrays of quantum dots using cellulosomal proteins W