The sizes of viruses and the methods employed in their estimation

摘要: In this review we have given an account of the various methods which are available to determine size virus particles. § IV endeavoured bring ultrafiltration method into agreement with other by suggesting a different factor for converting pore from factors commonly used. Throughout recognized probability that most viruses hydrated in solution and distinguished between molecular weight when dried.In VII formulae suitable interpreting centrifugation diffusion data possibility hydration is contemplated.It evident complication, added shape, makes it necessary several measurements be made before one can claim know virus. For reason, only cases three thought sufficiently adequate enable shape Virus, both dry hydrated, stated. These viruses, tobacco mosaic, tomato bushy stunt vaccinia respectively, separately discussed X.It will clear preceding sections that, while position regarding our knowledge absolute sizes far satisfactory, there has been amassed large amount bearing on subject. We should, however, point out found select what consider best experimental some may conflicting ideas expressed authorities. Frampton (1942) studied electron microscope photographs published Stanley & Anderson (1941) arrives at entirely estimate length mosaic Kausche, Pfankuch Ruska (1939) reported value approximately half Anderson. Electron photomicrographs von Ardenne (1940) Holmes probably strains same virus, also suggest values should not taken as absolute. (1939 a, b), basis viscosity experiments stream birefringence suggested previously forms gel any concentration therefore cannot said size. Lauffer reasons supposing argument incorrect. Bernal Fankuchen (1941a) particles being shorter than Kausche et al. conclude plant itself particle short 100 mμ.In obtaining arid assumptions, correct, long, thin shrink width rather drying almost spherical contract evenly all directions. At moment would seem no proving or disproving truth these but believe unlikely result such gross change invalidate calculations. instance, case haemocyanin Helix pomatia, seems improbable drying, already anhydrous ellipsoidal molecule 66 × 15·32 mμ expand in-width form sphere 24 diameter.In treatment regard density volume ‘bound’ water bulk, true. However, total occupied great hydration, shown markedly smaller mass free water. It is, nevertheless, well-established fact certain cases, gelatin example (Svedberg, 1924), small contraction does take place protein This phenomenon not, necessitate assumption denser ordinary water, explained ways.The solutions especially rod-shaped attracted much attention finding frictional axial ratios (Frampton, 1939 b; Lauffer, 1938; Loring, Neurath, Cooper, Sharp, Taylor, Beard Beard, 1941; Kobinson, Stanley, 1939), but, addition lack verification used, many (Robinson, Frampton, b) applied results obtained circumstances exclude fundamental postulates based. reason omitted detailed discussion methods.It appear order obtain evidence desirable study purified possible show ‘homo-geneous’ preparations obtained, they do consist merely macromolecular substances contaminated quantity Furthermore least sufficient assess assume