47121-G10
Active Orientation and Encapsulation of Bacteriorhodopsin-Driven Photo-Energy Transduction in Copolymer Shells
Research Impact: Our research has addressed the insertion of Bacteriorhodopsin (BR), a protein derived from the bacterial cell line Halobacterium halobium in polymer-based artificial membranes for the fabrication of next-generation solar energy systems based on biological function. BR utilizes light to pump protons uni-directionally, a process that has been perfected and coupled with the production of ATP, the energy that is used to drive a spectrum of foundational processes of life. Our research has aimed to harness the electrons that are coupled with proton transport to use BR for practical use as a nanofilm (4-nm thick) energy system. Experiments performed included the application of Langmuir-Blodgett (LB) thin film deposition to co-deposit the polymer membrane and protein molecules. The LB method allows for molecules that have both hydrophilic and hydrophobic groups (The membrane and protein possesses both of these properties) to be deposited on top of water (air-water interface). Subsequent compression of the molecules enables nanoscale films to be fabricated and deposited on solid substrates such as glass for analysis. The polymethyloxazoline-polydimethylsiloxane-polymethyloxazoline (PMOXA-PDMS-PMOXA) copolymer dissolved in chloroform was injected across the air-water interface. Following the evaporation of the chloroform, purified BR molecules were injected into the water and one hour was allowed for the protein to integrate with the membrane. Compression studies were performed to confirm protein insertion, and imaging studies using atomic force microscopy (AFM) examined the hybrid film morphology. A key element of this project involved our ability to determine the optimal parameters for deposition to realize optimized film stability. Surface pressures consistently greater than 45mN/m were achieved, serving as an important foundation towards the stable electrical/pH change measurements that will be explored during the next phase. This was an important accomplishment towards the production of subsequent generations of oriented protein-based devices which was a primary focal point of this work. Furthermore, robust protein encapsulation within the polymeric matrix was another major objective of the proposed work. Our studies thus demonstrated the streamlined capabilities of our fabrication approach. This will also play a key role in the work for the upcoming year where protein functionality (e.g. proton pumping/capacitive current generation) is explored. Because BR is among the most stable proteins available and the polymer membranes are very robust, these nanofilms are expected exhibit robust lifetimes/functionality. Impact on Career: Support from the ACS PRF program catalyzed a very rapid upstart in my research program. Partial support of my postdoctoral fellows allowed a rapid buildup of my research team and the production of impacting peer-reviewed proceedings papers which will be further developed during the coming year for journal paper submission. In addition, the impact of our work has already been acknowledged by the community, resulting in several invitations for the PI to deliver Keynote/Plenary lectures at major international meetings. The ACS PRF fund was graciously acknowledged in these talks. Impact on Education: The Principal Investigator places the education of the next generation of scientific leadership among his highest priorities. This project involved several undergraduates who performed LB and imagery experiments. Senior undergraduate students were also able to mentor junior undergraduate students in experimental protocols towards the acquisition of publishable data. For example, these teams analyzed the protein-induced changes in surface pressure during hybrid film fabrication and analyzed topographical imagery data of the atomic force microscope readouts of the hybrid films. Subsequent work for the coming year will involve electrical activity measurement of the nanofilms. Furthermore, findings from this project were also presented in BME 344 (Biological Performance of Materials) and ME 385 (Nanotechnology), two courses taught by the PI which correlated with the theme of this research. In fact, students from these courses have already developed K-12 teaching modules as part of their course final projects that will address emerging Nanotechnology and Energy concepts, a topic that is particularly relevant to our current generation of K-12 students. This initiative was co-programmed with the University’s Searle Center for Teaching excellence to assist with maximizing module impact and relevance towards K-12 students as well as teachers for use in new course development. Furthermore, the PI has developed a teaching partnership with Chicago-area and schools across the country to further develop and streamline the K-12 teaching modules. Resulting Publications: As a result of this project, our group will be submitting two peer-reviewed publications to the IEEE-NEMS-2009 international meeting (With grateful acknowledgements to the ACS PRF program). This research support has enhanced the opportunity for our laboratory to explore novel energy source development while working with several of NU’s most talented graduate/undergraduate students and postdoctoral fellows. Bibliographic Information: S. Wu, J. Lee, E. Robinson, M. Chen, E. Pierstorff, H. Huang, and D. Ho, “Deposition of Robust Protein-Polymer Membranes for Photo-Active Functionality,” in preparation, IEEE-NEMS 2009 H. Huang, E. Pierstorff, E. Robinson, and D. Ho, “Emergent Nanomaterial Strategies Based on Biotic-Abiotic Interfacing,” in preparation, IEEE-NEMS 2009.
