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Single Chain a-Helical Bundle Designed Around a Non-Biological Cofactor

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PI: Michael J. Therien, Jeffrey Saven, Willam DeGrado

Nonlinear Optical chromophores based on the RuPZn motif have been synthesized and shown to exhibit large hyperpolarizabilities. To elaborate nanoscale electrooptic materials, RuPZn dipoles must be uniformly aligned. Binding such a chromophore to the interior of an a-helical bundle offers one approach to organizing the dipole moment.

Previous bundle designs used heterotetrameric archetectures that did not completely encapsulate the chromophore. In addition, the penta-coordination requirement of the zinc center and the asymmetric structure of the RuPZn supermolecule necessitates an asymmetric bundle design. A single chain bundle (SC RPZ) asymmetirc template was thus design to provide appropriate binding affinity.

Preliminary UV/visible results display the single chain peptide binds the Ru-PZn chromophore. Circular dichroism spectroscopy indicates a-helical character in the presence and absence of protein. Size exclusion chromatography confirms the peptide encapsulates the chromophore as it elutes at a different volume (10.0 mL) from the apo protein (11.8 mL).

Conclusions:

The single chain design of an a-helical bundle has been completed. The peptide binds the RuPZn cofactor. This successful design will lead toward additional asymmetric/single chain designs that will offer a variety of functions including investigations of the non-linear optical properties of the assembly shown here.

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UV/vis of RuPZn with and without the single chain bundle CD of SC RPZ with and without the RuPZn cofactor
 

 

 

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