A nomograph for the conversion of ammonium sulfate concentrations at 0° is presented in which concentration is expressed both in percentage of saturation and in molarity, and the number of grams of the salt to be added to any initial volume is given

F. di Jeso

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THE JOURNAL cm BIOLOGICAL CHEMISTRY Vol. 243, No. 8, Issue of April 25, pp. 2022-2023, 1968 Printed in U.S.A. Ammonium Sulfate Concentration Conversion Nomograph for 0” (Received for publication, August 25, 1967) FERNANDO DI JESO From the Istituto di Chimica Biologica, University of Pavia, Pavia, Italia SUMMARY A nomograph for the conversion of ammonium sulfate con- centrations at 0” is presented in which concentration is ex- pressed both in percentage of saturation and in molarity, and the number of grams of the salt to be added to any initial volume is given. It is well known that, for the purification of a given enzyme by salting out, choosing a narrower range of ammonium sulfate concentration may be more effective than repeated fractionation (l-5). However, when fine adjustments of ammonium sulfate concentration are used, any condition such as pH, temperature, and protein and salt concentration must be more exactly es- tablished. The nomograph in Fig. 1 establishes the last condition ac- curately and conveniently. The temperature of 0” adopted is nearer to the temperatures generally employed in enzyme handling than is the room temperature adopted by others (6-7). The same nomograph may be employed with adequate precision in the range from -5” to 10” by adding algebraically 0.002 per each degree of temperature to the corresponding saturation values. The grams, y, of ammonium sulfate to be added to a volume, 2, in liters, of a solution of saturation S1 at 0” to yield a saturation & at 0” have been calculated as shown in Equation 1 Y= x G (52%) (1) I- Es 1000 2 where G is grams of ammonium sulfate in 1000 ml of saturated solution, 514.72, and V is apparent specific volume of am- monium sulfate in a saturated solution, 0.5262, as calculated from values in the International Critical Tables of Numerical Data (8, 9). This equation leads to entirely reproducible results, con- sistently the same as may be obtained at given values of tempera- ture and pH, by the more traditional but often less convenient procedure of adding a volume, z, in milliliters, of saturated solution to a liter of solution of fractional saturation Sr (10) (Equation 2). 1000 (s2- s$ 2 = 0) 1 - 52 Solutions prepared by both equations may differ about 1 y0 from their nominal values. Despite the extensive use of fractional saturation to designate the actual concentration of ammonium sulfate, it would be less ambiguous to use final molarity (11). In our nomograph all of the values at 0” of fractional saturation or of molarity are both reported either for the initial or for the final concent.ration and it is possible to raise to 3.9 M (z.e. saturation) all possible solutions of molarities lower than 3.9. REFERENCES 1. ROCHE, J., AND DERRIEN, Y., Bull. Sac. Chim. Biol., 28, 838 (1946). 2. GREEN, A. A., AND HUGHES, W. L., in S. P. COLOWICK AND N. 0. KAPLAN (Editors), Methods in enzymology, Vol. I, Aca- demic Press, New York, 1955, p. 67. --’ 3. RACKER. E.. AND SCHROEDER. E. A. R.. Arch. Biochem. Bio- phys.,‘74, ,326 (1958). ’ 4. CZOK, R., AND BUTCHER, T., Advance. Protein Chem., 16, 315 (1960). 5. DIXON, M., AND WEBB, E., Advance. Protein Chem., 16, 197 (1961). 6. DIXON, M., Biochem. J., 64,457 (1953). 7. CHAYKIN, S., Biockmistry laboratory techniques, John Wiley and Sons, New York, 1966, p. 138. 8. GILLESPIE, L. J., in International critical tables of nuwm-ical data. VoZ. III. McGraw-Hill Book Comnanv, New York. 1928; p. 60. * “I 9. BR~NSTED, J. N., in International critical tables of numerical data, Vol. IV, McGraw-Hill Book Company, New York, 1928, p. 218. 10. TAYLOR, J. F., in H. NEURATH AND K. BAILEY (Editors), The proteins. Vol. I. Academic Press. New York. 1953. D. 55. 11. P&ELL, g. M., A&D MCGILVERY, R, W., in W. ‘W. U~BREIT, R. H. BURRIS, AND J. F. STAUFFER (Editors), Manometric techniques, Ed. 3, Burgess Publishing Company, Minneapo- lis, 1957, p. 307. This is an Open Access article under the CC BY license.Issue of April 25, 1968 F. di Jeso 2023 3.8 3.6 34 3.2 3.0 2.8 2.6 24 k 2.2 z is 2.0 a 3 1.E “E If 1.4 1.2 1.c 0.E Of OL 0.2 , _. I -: 3 -: j -- i -1 ) . 1.5 0.4 0.3 0.2 0.1 0 1.0 3.9 3.8 3.7 3.6 Initial O5 on0 1 0 concentration Desired concentration 0 ?O 30 50 60 70 i 030 1.0 0.20 50 $0 30 20 10 0 Fro. 1. Ammonium sulfate conversion nomograph for 0”. The given initial concentration and desired concentration are first A line from this point through the volume at hand (initia2 volume) joined by a straight line. The value from the scale on the ex- of the solution gives the actual amount of salt required, in grams, treme right is then read at the point of intersection to give the read from the grams required line. Over the temperature range grams of solid (NH&S04 to be added to 100 ml of the solution. -5” to 10” it is recommended that the fractional saturation values be adjusted by adding algebraically 0.002 unit per degree. 

Ammonium Sulfate Concentration Conversion Nomograph for 0

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Ammonium Sulfate Concentration Conversion Nomograph for 0

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