M. HALWER, G. C. NUTTING AND B. A. B R I C ~
2786
[CONTRIBUTION FROM
THE
Vol. 73
EASTERN REGIONAL RESEARCH LABORATORY1]
Molecular Weight of Lactoglobulin, Ovalbumin, Lysozyme and Serum Albumin by Light Scattering2 BY &I. HALWER, G. C. XUTTINGAND B. A. BRICE Molecular weights of several proteins were determined from measurements of light scattering a t 90°, using an absolute photoelectric turbidimeter. The values obtained were 35,700 for 8-lactoglobulin, 45,700 for ovalbumin, 14,800 for lysozyme, a minimum of 73,000 for bovine serum albumin and 79,000 for horse serum albumin. Bovine serum albumin underwent a gradual aggregation when stored near 0", with a moisture content of 2 t o 10%. Satisfactory separation of normal and aggregated molecules was not accomplished by recrystallization, centrifugation or ultrafiltration. Osmotic pressure was a far less sensitive indicator of aggregates than light scattering.
The light scattering method for measuring mo- globulin13; and on o ~ a l b u m i n . ' ~ ~The ' ~ molecular lecular weights, developed chiefly by D e b ~ e ,was ~ , ~ weights of the influenza virus, bushy stunt virus and first applied to proteins by Putzeys and B r o ~ t e a u x , ~ovalbumin were evaluated from measurement of who determined the molecular weights of amandin, the turbidities of solutions by the transmission excelsin and hemocyanin relative to ovalbumin. method. The turbidities of solutions of the other Other light scattering studies have been made on proteins were measured indirectly b y comparison of the seed globulins of several species of the genus 90' scattering with that of materials of known or asPrunus6; on edestin'; on influenza virus and to- sumed turbidity. The turbidities reported here for mato bushy stunt virusx; on tobacco mosaic virus9; lactoglobulin, lysozyme, ovalbumin and serum alon a rabbit antibody proteinl0; on the mercury bumin were obtained directly from the scattering a t compound of enolase"; on bovine serum albu- 90" by means of an absolute photoelectric turbii ~ ~ i n l 'on , ' ~serum albumin and human y-pseudo- dimeter developed in this Laboratory.
E~perirnental~~
1 40
0
0
.4
.e
1.2
2
CONCENTRATION, g/lOOml. Fig. 1.-Plot of Hc/r vs. concentration for lysozyme, lactoglobulin and ovalbumin: 1, lysozyme, open circles are before centrifuging, closed circles after centrifuging; 2 , lactoglobulin, before centrifuging; 3, lactoglobulin, after centrifuging; 4, ovalbumin. (1) One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture. Article not copyrighted. (2) Presented in part a t the 116th Meeting of the American Chemical Society, Atlantic City, N . J., September 18-23, 1949. (3) P. Debye, J . A p p l i e d Phys., 15, 338 (1944). (4) P. Debye, J . Phys. Colloid Chenz., S I , 18 (1947). (:I) I'. Putzeyq and J . lirosteaus, l / u i i s . Forailay So'.., 31, 1314 11!l33) (.6) 1'. P u t z e y a and 11. I,. Reeckmans, B d l so
