Chapter III 



The Physical Properties of Infective Particles 



Howard K. Schachman and Robley C. Williams 

 Virus Laboratory, University of California, Berkeley, California 



I. Introduction 224 



II. Physical Methods 227 



A. Hydrodynamic and Thermodynamic Methods 227 



1, Introduction 227 



2. Viscometry 228 



a. General Considerations 228 



b. Viscosity of Solutions 229 



c. Measurement of Viscosity 231 



d. Interpretation of Viscosity Data 233 



3. Rotational Diffusion 236 



a. General Considerations 236 



b. Experimental Methods 238 



i. Electric Birefringence 238 



ii. Streaming Birefringence 239 



iii. Anomalous Viscosity 239 



iv. Dielectric Dispersion 240 



V. Polarization Fluorescence 240 



4. Diffusion 241 



a. General Considerations 241 



b. Measurement of Diffusion Coefficients 243 



i. Diffusion Through a Porous Disk 243 



ii. Free Diffusion 245 



c. Interpretation of Diffusion Coefficients 248 



5. Ultracentrifugation 252 



a. Introduction 252 



b. Sedimentation Velocity Method 255 



i. Sedimentation Coefficient 255 



ii. Molecular Size and Shape 257 



iii. Partial Specific Volume 259 



iv. Demonstration of Homogeneity 261 



V. Sedimentation in Multicomponent Systems 263 



vi. Sedimentation in a Partition Cell 264 



c. Sedimentation Equilibrium 265 



d. The Transient States During the Approach to Sedimentation 

 Equilibrium 267 



6. Electrophoresis 268 



B. Optical Methods 271 



1. Light Scattermg 271 



a. Small-Particle (Rayleigh) Scattering in a Gas 272 



b. Small-Particle Scattering in Solutions 273 



c. Large-Particle Scattermg 275 



2. Low-xAngle X-ray Scattering 277 



VOL. I — 16 223 



