Site-Specific Modification of Glucose Proteins Enabling Precise Surface Orientation For Glucose Sensors

An ideal labeling reaction between protein and surface should generate a protein-patterned surface with control over the orientation of the desired protein. Controlling orientation would generate a homogeneous, un-fouled protein surface and allow for maximum efficiency in regards to the activity, reactivity, and stability of the protein. In this research ideal bioorthogonal ligations were used between proteins modified with the noncanonical amino acid (ncAA), tetrazine-2.0 (Tet-2.0), and a surface containing a strained trans-cyclooctene (sTCO) to engineer ideal protein surfaces.\ud Creation of genetic glucose dehydrogenase (GDH)-TAG mutants and incorporation of the Tet- 2.0 amino acid was successful. The multiple Tet-2.0 modified GDH proteins were purified and their reactivity was compared to natural GDH. Tet-2.0 GDH had similar catalytic activity compared to unmodified GDH. Quantifying the bioorthogonal ligation was attempted with Total Internal Reflection Fluorescence (TIRF) microscopy, X-ray Photoelectron Spectroscopy (XPS), amine-modified magnetic bead assays, and with a carbon nanotube electrode amperometric assay. It has been difficult to discern native protein attachment to surfaces from tetrazine protein attachment to surfaces, which may be due to a problem with the bioorthogonal ligation. It was confirmed that all the tetrazine-GDH enzymes could be site-specifically labeled with retention of their activity on surfaces. Improvements in labeling carbon nanotube (CNT) electrodes are necessary to use this ideal reaction for amperometric sensing