Our earlier work established that a quantitative measure of protein conformation can be obtained from the temperature dependence of the Raman relaxation rate in low spin ferric proteins. This measure is d, the fractal dimensionality of the protein backbone, and it appears explicitly in the temperature dependence of the Raman spin-lattice relaxation rate of low spin ferric proteins are T**(3+2d). The values of d can also be computed from protein x-ray structure and fall in the range between 1.2 and 1.9 with ferredoxins near 4/3 and hemoproteins near 5/3. A d value of 1 implies a non-folding, linear structure; while a value of 2 equals the fractal dimension of an unrestricted random walk in three dimensional space. The proposed research will determine if the Raman spin-lattice relaxation rates in non-ferric, paramagnetic proteins also exhibit this correlation with structure. Proteins containing copper, cobalt, or spin labels will be investigated using pulse saturation and cw saturation techniques. Correlations between the fractal dimensionality and the secondary or tertiary structure of proteins will be sought. In addition, we will determine the cause of the change form a T to a T**2 temperature dependence observed for the direct relaxation rate in many proteins as solvent conditions are altered.
