NOTES
506 B ~ O -8.2' W loglo P,,
=
10.0682
2032.2
- T-
The slopes of these curves give a heat of transition of 2290 cal. per mole and a heat of fusion of 510 cal. per mole. These may be compared with the 1600 and 500 cal. per mole values given above. Acknowledgment.-This work was done under contract with the Office of Naval Research. VARIATION OF SEDIMENTATION CONSTANT WITH FIELD AND TEMPERATURE FOR NATURALLY OCCURRING POLYELECTROLYTES BY D. A. I. GORINGAND CAROLCHEPESWICK Maritime Regional Laboratory, National Reaearch Council, Halijaz, N . 8. Received October 81, lB66
In the course of ultracentrifugal studies on sodium desoxyribonucleate (DNA), carrageenate2fa and alginate, 3*4 certain careful experiments were done to test the dependence of sedimentation rate on the centrifugal field and temperature. This is a brief report of the findings. Experimental Sodium carrageenate was extracted at 60" from the seaweed, Chondrus c"pus, by the method re orted previously.* Its intrinsic viscosity in acetate bu&r (pH 5.5; I = 0.05) was 24 g.-1 dl. Sodium alginate was prepared by dial sis from a commercial sample previous y described' as 8-1. Its intrinsic viscosity in acetate-NaC1 buffer (pH 5.5; I = 0.15) was 19.2 g,-I dl. The preparation of the DNA has been given previously.5 The sample was described as TNA-V. Sedimentation was measured in a Spinco ultracentrifuge at room temperature or at 40-50" by warming the rotor and the cell.' At room temperature, the fixed couple readings increased 2-3" during the run. A similar decrease was noted a t the higher temperatures. The mean of the fixed couple readings was corrected by the differencebetween the fixed and the free couple at the end of the run. Sedimentation constants were corrected to a solvent of pure water at 25" in the usual manner. Polyelectrolytes were dissolved either in sodium acetateNaCl buffer of ionic strength, Z = 0.15 and H 5.5 or a sodium phosphate buffer with I = 0.002 and p 6 6.5. In studying variation of field runs were carried out alternately at two speeds in series of 4 or 6 on samples of a single solution. The smallest concentration of solute consistent with sustained clarity of the diagrams was chosen by trial and error. Choice of conditions was particularly critical for measurements at low ionic strength. By use of a flat and a wedge cell, a solution and a control were co-sedimented. The ratio s/so was obtained where sa was the sedimentation constant for the control. Errors due to rotor expansion, variation of speed or incorrect determination of temperature were thereby compensated. I n the early runs edestina (prepared in a monodisperse form from hemp seed) was used as the control. For this, almost spherical, molecule it was assumed that the rate of sedimentation was independent of the speed of centrifugation. With edestin as control, s was (1) Isoued a6 N.R.C. No. 3884. (2) D. A. I. Goring and E. G . Young, Can. J . Chenz., 33, 480 (1955). (3) D. A. I. Goring and Carol Chepeswick, J . Colloid Sci., 10, 440 (1955). (4) D. L. Vincent, D . A. I. Goring and E. G. Young, J . A p p l . Sci., 6, 374 (1955). (6) A. M. Marko and G . C. Butler, J . Biol. Chem., 190, 165 (1951).
The authors are indebted to Dr. Marko for providing the D N A . (6) D. A. I. Goring and P. Jolinson, Arch. Biochem. Biophys., 66, 448 (1955).
Vol. 60
found independent of field for sodium carrageenate in the sodium acetate-NaC1 buffer. Such solutions were therefore used as controls in the later runs a t low ionic strength. In studying the effect of temperature, measurementa were made alternately a t room temperature and 50' in series of four, with two at each temperature. The concentration of solute was 0.1%.
Results and Discussion As shown in Table I, the ratios s/sc are essentially constant for wide variations in field. The small differences observed could be due to experimental error. The invariance remains a t low ionic strength when the molecule is considerably extended. These results suggest that no perceptible orientation of the molecule occurs as a result of the increase in the centrifugal field. Koenig and Perrings7 have noted a similar invariance of s with field for DNA in 0.2 M NaC1. However, these authors claim a significant variation of s with field for bovine fibrinogen* and plasma a1bumin.D TABLE I VARIATION OF s/so Polyelectrolyte .
Carrageenate Carrageenate DNA
Conon.,
WITH Field
x
5% 0.03
0.15
0.03
0.002
0.02
0.002
I
FIELD
10-1 9
44 260 63 260 63 260
Mean dev., a/no
%
0.525 0.526 0.614 0.628 0.416 0.434
0.6 0.9 0 0.6 1.9 0.9
An interesting effect was found with DNA. A t high speeds the peak was sharp while a t low speeds the peak appeared more diffuse. If, in a single run, the speed was reduced for a time and again increased the peak was alternately-sharp, diffuse and again sharp. This effect was observed and photographed in several experiments. The sedimentation constants corresponding to the three steps of the run agreed within 15?Z0. Evidently some property of the boundary varied reversibly with speed, although s remained unchanged. VARIATION Polyelectrolyte
Carrageenate Alginate
OF
TABLE I1 SEDIMENTATION CONSTANT WITH TEMPERATURE
I
0.15 0.15 0.002 0.002 0.15 0.15
0.002 0.002
0
Mean dev.,
T%mp., C.
816,
8
%
48.4 28.6 48.4 28.6 47.6 28.0 47.6 28.0
4.46 4.59 1.56 1.27 2.90 2.67 1.15 0.96
1.6 2.4 5.1 4.7 0.; 1 .9
0.2 3.6
The variation of s& with temperature is given in Table TI. A t I = 0.15 there was no significant change for carrageenate or alginate. A t I = 0.002 there was a marked increase of sZ6 with temperature. Koenig and Perrings have fouiid similar but smaller trends for DNA7 and boviile (7) V. L. Koenig and J. D. Perrings, J . Colloid Sci., 8 , 452 (1957). (8) V. L. Koenig and J. D. Perrings, Arch. Biochem. Biophys., 40, 218 (1952). (9) V. L. Koenig and J. D. Perrings, ibid., 41, 367 (1952).
April, 1956
NOTES
plasma albuming in 0.2 M NaC1. The change in si5 is possibly due to a decrease in the hydration of the polyelectrolyte at higher temperatures. With salt present, hydration would be less at all temperatures, and a difference in temperature might not produce a perceptible effect.
The Acidities of Chloramine and Dichloramine. -For the following discussion, it will be convenient to define an aquo acid molecule m a water molecule in which one of the protons has been replaced by another group, R. The ionization of an aquo acid is thus represented by
507
HOR = H +
THE THERMODYNAMIC PROPERTIES OF CHLORAMINE, DICHLORAMINE AND NITROGEN TRICHLORIDE BY WILLIAM L. JOLLY Department of Chemistry, University of California, Berkeley, CaZ. Received November 10. 1066
I n both aqueous solutions’ and in liquid ammonia solutions,2 chloramine reacts with ammonia to form hydrazine. Therefore the thermodynamic properties of chloramine are of importance in discussing equilibria involved in the synthesis of hydrazine. I n this note, the free energies of aqueous chloramine and related species are estimated from literature data,. It is emphasized that some of the results are only rough approximations and are to be considered tentative until better experimental data are obtained.
+ OR-
(1)
The corresponding ammono acid molecule is an ammonia molecule in which one of the protons has been replaced by the group R HzNR
=
Hf
+ HNR-
(2)
The pK values for several ammono acids and the corresponding aquo acids are listed in Table I. It appears that most of the aquo acids tabulated are roughly lo7 times stronger than the corresponding ammono acids. Chloramine, NH2CI, may be looked upon as the ammono analog of hypochlorous acid, HOCI. Since the pK value for hypochlorous acid is about 73, one may estimate pK = 14 2 for chloramine. Hence in very alkaline solutions one should expect an appreciable concentration of chloramide ion, NHCI-. The acidity of dichloramine, NHC12, may be estimated from Table I and the acidities of several
*
TABLE I pK VALUESFOR AMMONO AND AQUOACIDS Ammono acid
PK
Ammonia, HNHna -33 Acetamide, CHsCONH24 15 Benzamide, C~HICON Hz4 14.5 o-Nitroaniline, ( N O Z ) C ~ H ~ N H ~ 14 p-Nitroaniline, ( N02)C6H4NHz6 12 Sulfamide, HZNSOZNHZ~ -11 Cyanamide, HzNCN* 10.5 Benzenesulfonamide, C ~ H ~ S O Z N H Z ~ -10 Sulfanilamide, ( NHz)CBH~OZNH+ 10 Nitramide, HzNNOZ’ 7
Aquo acid
PK
Water, HOHa Acetic acid, CHaCOOHa Benzoic acid, C~H6COOH10 +Nitrophenol, (NOz)c6H4OH6 p-Nitrophenol, (N02)CeH40H6 Sulfamic acid, H2NSOZ0H1l Cyanic acid, HOCNla Benzenesulfonic acid, C6HsSOzOH13 Sulfanilic acid, (NHz)C6H4S0z0H14 Nitric acid, HONOz
The methods of calculation are straightforward except for the estimation of the acid ionization constants of chloramine and dichloramine. A method for estimating the acidity of an ammono acid from the known acidity of the corresponding aquo acid (or vice versa) is outlined. (1) L. F. Audrieth and B. A. Ogg. “The Chemistry of Hydrazine,” John Wiley and Sons, Inc., New York. N. Y., 1951. (2) H. H. Bider, F. T. Neth and F. R. Hurley, J . A m . Chem. Soc., 16, 3909 (1954). (3) G. E. K. Branch and M. Calvin, “The Theory of Organic Chemistry,” Prentice-Hall Inc., New York, N. Y., 1941. (4) G. E. K. Branch and J. 0. Clayton, J . A m . Chem. SOC.,60, 1680 (1928).
(5) A. I. Schattenstein, Acta Phueicochim. U.S.S.R., 10, 121 (1939). ( 6 ) Personal communication from Professor L. F. Audrieth. (7) Determined by the author by pH titration. (8) A. Albert and R. Goldacre, Nature, 149, 245 (1942). (9) Branch and Calvin8 have estimated A p K = 6 for the reaonance energy of the carboxylate ion. (10) W. M. Latimer, “Oxidation Potentials.” 2nd ed., PrenticeHall, Inc., New York. N. Y., 1952. (11) Estimated from the data of M. E. Cupery, I n d . Eno. Chem.. 80, 627 (1938). (12) “Iuternational Critical Tablea,“ Vol. VI, McGraw-Hill Book Co., Inc.. New York, N . Y., 1928. (13) R. S. Airs and M. P. Balfe, T r a m . Faraday SOC., 89, 102 (1 943). (14) W. Carr and W. J. Bchutt, ibid., 86, 579 (1939).
16 5 (5 4 (4 7 7 1 4
