LETTERS TO THE EDITORS 103

]:~EFEREN CES

1. GOE~TE, E. K., J. Colloid Sci. 4, 459 (1949). 2. AER&MSON, H. A., MOYER, L. S., AND GORIN, M. H., Electrophoresis of Proteins,

Reinhold, New York, 1942. .3. VOLD, R. D., AND KONECNY, C. C., J. Phys. & Colloid Chem. 53, 1262 (1949). 4. GREI~R, L., AND Vou), R. D., J. Phys. & Colloid Chem. 53, 67 (1949). 5. CORRIN, M. L., LIND, E. L., ROGI:NSKY, A., AND HARKINS, W. D., J. Colloid Sci. 4,

485 (1949). 6. NEVILLE~ H. A., AND JEANSON, C. A., J. Phys. Chem. 37, 1001 (1937); see also

GOETTE, E. I~., Die Chemie 57, 67 (1944). 7. McBAIN, J. W., AND BETZ, M. D., J. Am. Chem. Soc. 57, 1909 (1934). 8. McBAIN, J. W,, AND HUFF, H. M., J. Colloid Sci. 4, 383 (1949). 9. HARTLEY, G. S., COLLIE, B., AND SAMIS, C. S., Trans. Faraday Soc. 32, 795 (1936).

TODD M. DOSCHER Department of Chemistry, University of Southern California, Los Angeles 7, California

Received January 6, 1950

SOLUBILIZATION IN AQUEOUS SOLUTIONS OF BOVINE SERUM ALBUMIN

It has been found that an aqueous solution of bovine serum albumin will solubilize so-called fat-soluble dyes. The phenomenon appears to be reversible as indicated by dialysis experiments as well as experiments involving the effect of temperature. The solubilization can be observed in a few minutes after the solid dye and protein solution are mixed. Several days are required, nevertheless, to obtain equilibrium values.

The results are given in Fig. 1 for the effect of the native protein on dimethylaminoazobenzene. All solutions were maintained at pH 6.8 with 0.07 M phosphate buffer. The values of the optical density at the absorp- tion maximum (h = 4200 A) are plotted against the concentration of albumin in Fig. 2. The linear relation indicates that the ratio of solubilized (or adsorbed) dye to protein is constant.

To obtain a numerical value for this ratio, the absorption of a series of alcohol'water solutions of the dye was determined. The best match was obtained for a 1 : 1 alcohol-water solution. This solvent gave a value (1) for E / C = 0.1080 rag./1, at h = 4200 A for dimethylaminoazobenzene. The molar ratio of dye to protein w~s very close to 1:6.

The linear relation between the solubilization Of dye and concentration of albumin may be seen by considering the protein molecules as a separate phase. Since the dye is limited to the surface of the serum albumin mole- cule, a surface activity function, n*, may be set up which in the ideal case is equal to n, the number of molecules of dye per unit area of protein surface. The two-dimensional activity coefficient of the dye molecule

104 L E T T E R S TO T H E E D I T O R S

0.~'

0 .6

0 , 5

0 . 4

Elcm.

0 .5

0 . 2

O,1

/ \ I \

I \ ! \

I

/ '\ // \

Y

I I/ D

I

! I I I

\

i \

FIo. 1. The optical density for bovine se rum albumin solution which has been in contact wi th dimethylaminoazobenzene, p i t 6.8, 0.07 M phospha te buffer, t empera tu re 27 4- 0.1°C.

P e r Cen t A l b u m i n Concen t ra t ion

A . . . . . . . . . . . 0 .0

B . . . . . . . . . . . 0.1 C . . . . . . . . . . . . 0.4 D . . . . . . . . . . . 0.5 " E . . . . . . . . . . . . 1.0 F . . . . . . . . . . . . Dimethylaminoazobenzene

6.5 rag./1, i n 1 : 1 alcohol-water solution.

~icm.

0.4

0.6

0.5

0.5

0.2

0.I

I , , I I I 0.2 0.4 0.6 0.S % ALBU~4IN

LETTERS TO THE EDITORS 105

FIG. 2. The optical density at X = 4200 A for bovine serum albumin solution which has been in contact with dimethylaminoazobenzene, pH 6.8, 0.07 M phosphate buffer, temperature 27 =i= 0.1°C.

m a y be defined by (2) f = n * / n .

The chemical po ten t i a l of the adsorbed dye is

u2 = u~ ° + k T l n n*,

and tha t for the dye in solution is

u2' = u2 °' + k T In a2. At equilibrium

u2 = u2' and n * = Ca2 where C is a constant.

Since the solution is sa tura ted with respect to the dye and the concen- t ra t ion of buffer is kept a t the same value in all experiments, a~ remains constant. The surface of the a lbumin molecule is so sparsely popula ted

106 LETTERS TO THE EDITORS

wi th dye molecules t h a t the two-dimensional ac t iv i ty coefficient can be set equal to u n i t y wi th the result t h a t n is cons tant .

ACKNOWLEDGMENT

The suggestions of Prof. A. W. Thomas in this work is gratefully acknowledged.

REFERENCES

1. KOLTHOFF AND STRICKS, J. Phys. & Colloid Chem. 52, 915 (1948). 2. WARD AND TOP, PAIl Trans. Faraday Soc. 42, 413 (1946).

BENJAMIN CARROLL Newark Colleges of Rutgers University, Newark, N. J.

and Department of Chemistry, Columbia University, New York, N. Y.

Received January 13, 1950

B O O K S R E C E I V E D F O R R E V I E W

Abriss der Chemischen Technologie der Textilfasern, H. E. Fierz-David and E. Merian, Verlag Birkh~user, Basel, 1948, 295 pp.

An Introduction to Biochemistry, Roger J. Williams. D. Van Nostrand and Co., Inc., 2nd edition, 1948, 736 pp., $5.75.

Advances in Catalysis, Vol. I, Frankenburg, Komarewsky and Rideal, editors, Academic Press Inc., 1948, 321 pp., $7.80.

Proceedings of the Congress on Rheology, Holland, 1948, Interscienee Publ. Inc., $11.00.

Vierteljahresband Chemisches Zentralblatt IV" Quartal, 1945, Akademie-Verlag, Berlin, 1948, 1876 pp.

The Science of Plastics, H. Mark and E. S. Proskauer, Interscience Publ. Inc., 1948, 632 pp., $9.00.

]~lastomers and Plastomers, ¥ol. II, R. Houwink, Elsevier Pubt. Co., 1948, 515 pp., $9.00.

High-Polymer Physics, A Symposium, Howard A. Robinson, editor, Remsen Press Division, Chem. Pub1. Co., Brooklyn, 1948, 572 pp.

The Colloid Chemistry of the Silicate Minerals, C. E. Marshall, Academic Press Inc. Chemistry of Specific, Selective and Sensitive Reactions, Fritz Feigl, Academic Press

Inc. Acetylene Chemistry (translated from German), J. W: Reppe, Charles A. Meyer & Co.,

New York, 209 pp., $10.OO. Torchbearers of Chemistry, H. M. Smith, Academic Press Inc., 1949, 270 pp., $8.00. Advances in Carbohydrate Chemistry, Pigman and Wolfrom, editors, Academic Press

Inc., 1949, Vol. IV, 378 pp., $7.80. Die Thermodynamik des W~me- und Stoffaustanches in der Veffahrenstechnik, "W.

Matz, Verlag Dr. Dietrich Steinkopff, Frankfurt, Main, 1949, 355 pp. Colloid Science II. Reversible Systems, H. R. Kriiyt, editor, Elsevier PubL Co., Inc.,

New York, 1949, 753 pp., $11.50. Strength of Plastics and Glass, R. N. Haward, Interscience Publ. Inc., New York, 1949,

245 pp., $5:50.