RAMAN SPECTROSCOPIC EVIDENCE FOR Z DNA IN RAD ENZYME BOUND DNA

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Existence of left handed DNA (Z-DNA) was discovered and extensively characterized in 1979. Since then there has been considerable research in establishing biological roles for Z-DNA. Recently Rich's group has established that a human protein, ds RNA deminase (dsRAD) has specificity for binding Z-DNA. The goal of this project is to provide direct evidence for the existence of left handed conformation for DNA when it binds to protein ds RAD. Raman spectra of poly(GC) in low salt and high salt solution, control protein, protein/poly (GC) complex have been obtained using 407 nm laser excitation. Raman spectral features of left and right handed DNA conformers have been characterized. By comparing these with the spectra of the protein/ poly (GC) complex, we concluded that DNA exists in left handed conformer when it binds to the ds RAD protein. Additional evidence have been provided by fluorescence and CD spectroscopy.