HF (95 GHZ) EPR OF SPIN LABELED DNA

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We are exploring applications of HF EPR in studying molecular motion of spin-labeled DNA. Initial trials include W-band experiments with a 50-mer duplex of 5'-GGT GCG ACC TCG QAT CGT GCT CCT CAT CCT CGT GTC CTA ATC TAT CGT AT matched against its complement (2-aminopurine matches against the spin label Q). The spin label is in position 13. During the 1997 grant year we have acquired an extensive set of experimental 95-GHz EPR spectra from spin-labeled DNA segments of different length. Analysis of these spectra indicate that enhanced g-factor resolution of W-band EPR allows to characterise the intrasegment motion not only along the z-direction, but along x- and y-directions. This information was not available from earlier X-band studies. The data also show a great sensitivity enhancement to these modes of motion and will lead to a better understanding of rigidity of DNA.