CAMERINI-OTERO et zy al. zyxwvutsrqp Koppel, D. E. (1973), Ph.D. Thesis, Columbia University. Lin, S. H. C., Dewan, R . K., Bloomfield, V. A., and Morr, C. V. (1971), Biochemistry 10,4788. Mandel, L. (1969), Phys. Rev. 181,75. Mandel, L., and Wolf, E. (1965), Rev. Mod. Phys. 37,231. Margenau, H., and Murphy, G. M. (1956), The Mathematics of Physics and Chemistry, 2nd ed, Princeton, N. J., D. van Nostrand Co., Inc., p 341. Nossal, R., Chen, S. H., and Lai, C. C. (1971), Opt. Commun. 4,35. Oliver, C. J., Pike, E. R., Cleave, zyxwvuts A. J., and Peacocke, A. R. (1971), Biopolymers10,1731. Pecora, R. (1964), J. Chem. Phys. 40,1604. Pecora, R. (1969, J. Chem. Phys. 43,1562. Pecora, R . (1968), J. Chem. Phys. 48,4126. Pecora, R . (1972), Annu. Rev. Biophys. Bioeng. 1,257. Pusey, P. N., Schaefer, D. W., Koppel, D. E., Camerini- Otero, R. D., and Franklin, R. M. (1972), J. Phys. (Paris) 33, C1-33. Rimai, L., Hickmott, J. T., Cole, T., and Carew, E. B. (1970), Schaefer, D. W. (1973), Science 180, 1293. Schaefer, D. W., Benedek, G. B., Schofield, P., and Bradford, Schaefer, D. W., and Berne, B. J. (1972), Phys. Rev. Lett. 28, Schwarz, G. (1968), Rev. Mod. Phys. 40,206. Tanford, C. (1961), Physical Chemistry of Macromolecules, Uzgiris, E. E., and Costaschuk, F. M. (1973), Nature, Phys. Vournakis, J., and Rich, A. (1971), Proc. Nut. Acad. Sci. Ware, B. R., and Flygare, W. H. (1971), Chem. Phys. zy Lett. Yphantis, D. A. (1964), Biochemistry 3,297. Biophys. J. zyxwv IO, 20. E. (1971), J. Chem. Phys. 55,3884. 475. New York, N. Y., Wiley, pp 147,380. zyx Sci. 242,77. U. S. 68,3021. 12,81. Intensity Fluctuation Spectroscopy of Laser Light Scattered by Solutions of Spherical Viruses: R17, zyxwvuts QP, BSV, PM2, and T7. 11. Diffusion Coefficients, Molecular Weights, Solvation, and Particle Dimensionst Rafael D. Camerini-Otero,* Peter N. Pusey,$ Dennis E. Koppel,$ Dale W. Schaefer,B and Richard M. Franklin// ABSTRACT: The diffusion coefficients (D) of several spherical viruses have been determined by the method of intensity fluctuation spectroscopy. The values for D&,, for bacterio- phages R17, QP, PM2, and T7 are (in units of lO-7cmZ sec-1): 1.534 zyxwvutsrq i 0.015, 1.423 f 0.014, 0.650 zyxwvuts i 0.007, and 0.644 i 0.007, respectively; that for the plant virus, tomato bushy stunt virus (BSV), is 1.246 i 0.012. The molecular weights were calculated from these values of D combined with litera- ture values for the sedimentation coefficients (s) and values for the apparent specific volumes determined by us (R17, QP, and PM2) or obtained from the literature (BSV and T7). The calcu- lated molecular weights for R17, QP, BSV, PM2, and T7 are (in millions of daltons): 4.02 i 0.17,4.55 f 0.16,8.81 f 0.17, 47.9 zyxwvutsrqpo * 1.7, and 50.9 f 1.1, respectively. These values are in good agreement with literature values and those estimated T he method of intensity fluctuation spectroscopy of scattered coherent (laser) light (Pecora, 1964; Dubin er al., t From the Department of Molecular Biophysics, The Public Health Research Institute of the City of New York, Inc., New York, New York 10016 (R. D. C.-0. and R. M. F.), the IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 zyxwvutsr (P. N. P., D. E. K., and D. W. S,), and the Department of Physics, Columbia University, New York, New York 10027 (D. E. K.). Received May 8, 1973. This research was supported by IBM and by Grant AI-07645 from the U. S. Public Health Service. R. D. C.-0. is an M.D.-Ph.D. Predoctoral Fellow at the New York University School of Medicine, supported by U. S. Public Health Service Medical Scientist Training Grant No. 5 TO5-GMO- 1668-06. A preliminary report of some of the work on R17 has been presented earlier (Pusey et al., 1972). 960 BIOCHEMISTRY, VOL. 13, NO. 5, 1974 from composition. Using the Stokes-Einstein equation, we have calculated hydrodynamic radii, Rh, for these viruses from our values of D~O,~. These radii are 140 f 2, 151 f 2, 172 i 2, 330 =t 3, and 333 i 3 A for R17, QP, BSV, PM2, and T7, respectively, and are in agreement with the dimensions obtained by such techniques as low-angle X-ray scattering, light scattering, and electron microscopy. Values for the solvation of these viruses, derived from the data, are (in cm3 of solvent/g of virus): 1.02 f 0.09, 1.22 i 0.08, 0.75 f 0.04, 1.11 f 0.08, and 1.18 f 0.06, in the same order as above. The diffusion coefficients for all the viruses were studied as functions of virus concentration. In addition, D for R17 and PM2 was studied as a function of ionic strength, and D for R17 was also measured as a function of temperature and pH. 1967, 1970; Cummins et a/., 1969; Foord et a/., 1970; Pusey et al., 1972, 1974) has been used to determine the translational diffusion coefficients 1 of several nearly spherical viruses : the bacteriophages R17, QP, PM2, and T7 and the plant virus, $ Present address: Royal Radar Establishment, Gt. Malvern, Worcs., 8 Present address: Department of Applied and Engineering Physics, 7 Present address: Sandia Laboratories, Albuquerque, New Mexico Present address: Biozentrum der Universitat, CH-4056, Basel, 1 Throughout we shall assume translational diffusion coefficients to be England. Clark Hall, Cornell University, Ithaca, N . Y. 14850. 87115. Switzerland. understood,