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Researchers Explore Nature's Energy Conversion Process
Newark, N.J. -- Plants and bacteria convert the sun's light energy into electrical energy through a remarkable protein complex called the photosynthetic reaction center. The process of energy conversion is accomplished through a series of light-initiated electron-transfer reactions between both organic and metal complexes that are bound to the protein. Similarly, many of the electron-transfer reactions and catalytic transformations that support life on the planet are mediated by organic and metal complexes bound to proteins.
In the laboratory of Ramy S. Farid at the Newark campus of Rutgers University, state-of-the-art apparatus are being utilized to synthesize metalloproteins to emulate these electron-transfer and catalytic reactions, paving the way for alternative solar-energy systems and molecular-based computers that mimic nature's remarkable powers.
Using a Solid-phase Peptide Synthesizer, Circular Dichroism Spectrometer, Time-correlated Single Photon Counting Instrument, Emission Spectrometer, and other equipment, faculty and student investigators are able to make peptide models, purify and characterize them, and then quantify their function with respect to electron transfer and catalytic activity.
Farid, assistant professor of bioinorganic and biophysical chemistry, explains that emulation is accomplished by binding redox and catalytically active metal complexes and photoexcitable chromophores to the highly tuneable and well-defined interior of both synthetic peptides and modified natural proteins.
The Solid-phase Peptide Synthesizer builds proteins up to 60 amino acids long. Such capability -- unique not only for a university laboratory, but rare even in industrial research settings-- provides the opportunity to study a wide array of model proteins.
Following reversed-phase HPLC purification, the proteins secondary structure is elucidated using the Circular Dichroism (CD) Spectrometer. CD also is used to characterize the stability of the protein with respect to heat and chemical denaturants.
"To be able to measure the function of the metalloproteins, we also must be able to measure the excited-state lifetimes and quantum yields of the protein-bound metal complexes. That is, the electron-transfer rates," says Farid.
The necessary measurements are obtained on the Single Photon Counting Instrument and Emission Spectrometer. With a wavelength of 190 to 900 nm, the instruments are able to measure with high precision the excited-state lifetimes and quantum yields of the metal complexes, respectively. With the pulsed technique of time-correlated photon counting, the instruments can quantify a lifetime from an extremely short 200 picosecond (a rare capability) to 2 milliseconds with light bursts as short as 1 nanosecond.
The proteins that Farid and his students are constructing could lead to the development of efficient molecular-based solar-energy systems and possibly molecular-based computers that derive their energy from synthetic metalloproteins incorporated onto electrode surfaces. Such molecular-based systems not only would be uniquely small, measured on the nanometer scale, but also present the possibility of limitless control of their function by simple chemical modifications of their components.