NOTES
1336
The macroscopic viscosity, q , was measured over a range of polymer concentrations and temperatures by the conventional falling ball methods with glass spheres of the order of 1 mm. diameter. Values were then interpolated on a logarithmic plot for the concentrations and temperatures of the ultracentrifuge experiments (the temperatures ranged from 22 to 28'). At 2 5 O , log q for the three polymer concentrations cited above was 0.93, 1.56 and 2.33, respect,ively. Presumably an important quantity determining the ratio of qe to q is the ratio of particle diameter ( D ) to some characteristic dimension of the polymer coil; clearly, as the latter ratio becomes large, q e / q mustapproach unity. As a measure of coil size, we have used (ro2)1/2, even though we are dealing with a charged polyelectrolyte; it probably does not deviate much from the 8-solvent configuration in our concentrated solutions, where there is a high density of counter ions as well as added neutral salt. In Fig. 1, log q e / q is plotted against D/(ro2)'/2. The latter size ratio lies in the range from 2 to 4.3: the local effective viscositv is tremendoudy smaller than 'the steady flow viscosity, b"y a factor of 80 t o 1400. Log q e / q increases with increasing 0 / ( 6 ? ) ' / 2 as expected. Moreover, it increases M ith increasing polymer concentration. The latter dependence is probably related to the role of entanglement coupling in determining the viscosity,g which suggests that the average distance between entanglemAnt points, (rT)Ih,is the important dimension rather than (rq2)'/2. The average distance between entanglements certainly decreases with increasing concentration, though the functional relation is uncertain,'O and hence the data of Fig. 1 might fall on a sing& composite curve if log qe/q could be plotted against D/(re2)l/z. The accuracy of the present data is insufficient, however, for a more detailed analysis. Data of this sort are potentially valuable in clarifying the frictional resistance encountered by polymer segments themselves in translation, as reflected in time-dependent mechanical properties." This, too, is of course very much smaller than would correspond to the steady-flow viscosity, and in some diluted systems the local viscosity encountered by the polymer segments appears to be of the same order of magnitude as that of the solvent.12
VOl. 63
ratio of HSA to SDS (HSA/SDS) is between 100/0 and 70/30, there are three kinds of complexes, AD,-ADI2, AD, and AD2, (A: HSA, D:SDS, and n = 105/2). In the mixing ratio region between 70/30 and 45/55 the complex ADzn changes continuously to AD,,. Measuring diffusion coefficient and intriiisic viscosity of the system HSASDS, Neurath and Putnam3 found that the formation of AD, occurs without detectable changes in molecular shape and the formation of AD2n involves an increase in the molecular asymmetry of the protein. This time an ultracentrifugal study was carried out a t p H 6.8. The results are reconciled with those by diffusion and viscosity. Experimental Horse serum albumin and sodium dodecyl sulfate used were the same as used previously.1 Experiments were conducted a t room temperature at 59,780 r.p.m. using a Spinco Model E ultracentrifuge. Ionic strength of the phosphate buffer was 0.10 and the sum of concentrations of HSA and SDS was 1.0%. Ultracentrifugal drive was continued for 60 minutes.
Results and Discussion All the patterns in the weight ratio region HSA/SDS = 100/0 - 45/55 had a single boundary. One of the patterns is shown in Fig. 1.
Acknowledgments.-This work was supported in part by the Research Committee of the Graduate School of the University of Wisconsin from funds supplied by the Wisconsin Alumni Research Foundation. We are greatly indebted to Dr. J. W. Vanderhoff of Dow Chemical Company and Dr. F. J. Glavis of Rohin and Haas Company for supplying materials, and to Mr. E. M. Hanson for operating the ultracentrifuge. (8) J. D. Ferry, L. D. Grandine, Jr., and D. C. Udy, J. Colloid Sci.9 8, 529 (1953). (9) R. F. Landel, J. W. Berge ana J . D. Ferry, ibid., 12, 400 (1957). (10) P. R. Saunders, D. hl. Stern, S. F. Kurath, C. Sakoonkim and J. D. Ferry, ibid., in press. (11) 6. D. Ferry and R . F. Landel, Kolloid-Z., 148, 1 (1550). (12) J. D. Ferry, D.J. Plazek and G. E. Heckler, J. chim. p h y s . , 66, 152 (1958).
ULTRACENTRIFUGAL STUDY OF HORSE SERUM ALBUMIN-SODIUM DODECYL SULFATE INTERACTION BY KOICHIRO AOKI Contribution from the Chemistry Laboratory, Napoya Cilu Uniusrsify. Mixuho-ku, Nagoya, Japan Received December 16,1368
It has been found by electrophoretic studies on the system horse serum albumin (HSA) and sodium dodecyl sulfate (SDS) that various complexes are formed a t p H G.8.192a When the weight mixing (1) K. Aoki, J. Am. Chem. Xoc., 80, 4904 (1958). (2) (a) F. W. Putnam and H. Nerirath, J. Biol. Chem., 169, 155 (1945); see also, (b) J. T. Yang and J. F. FoRter, J . Am. Chem. Soc., 76, 6560 (1953); ( 0 ) &I. J. Pallansch and D. R. Briggs, i b i d . , 76, 1390
(1954).
Sedimentation coefficients ~ ~ calculated 0 , ~ are shown in Fig. 2. These values are not those extrapolated to zero concentration. The ~ 2 0 value , ~ of 0.3% HSA solution was 4.4 8,agreeing wlt'h the value found in the l i t e r a t ~ r e . ~Values of the partial specific volume (6) were determined by sinlply assuming that all the SDS used was bound to HSA to form a complex and by measuring the density of the mixture a t 25.00'. It was found that V was TABLE I WEIGHTMIXINGRATIOREGIONAND THE COMPOSITION OF COMPLEX FORMED HSA/SDS
100/0-95/5 95/5-80/20 80/20-70/30 70/30-45/55
Complex formed
ADi-ADI? A D l 2and A D , AD, and ADw AD2n-ADan
(3) H . Neurath and F. W. Putnam, J . Biol. Cham., 160, 357 (1945) P. A. Charlwood and A. Ens, Can. J . Chem., 86, 99 (1957). (6) P. A. Charlwood, J . A m . C h e n . Sac.. 79, 770 (1957). (4)
5
I
I
1
I
1
I
W
continuous increase in the sedimentation coefficient.
c v
S20
- THE ELECTRICAL
CONDUCTIVITY MOLTEN SILICA
3 E 2 -
-
I
-
I
I
I
I
I
I
OF
BY M. B. PANISH Research and Advanced Deueloprnert Dzvisron, AVCO Corp., Wilmangton, M a s s . Received December 16, 1968
In connection with studies of the properties of materials a t high temperatures we have determined
