A rapid rock and roll dialyzer

ANALYTICAL

BIOCHEMISTRY

3, 264-266 (1962)

SHORT COMMUNICATION

A Rapid

Rock

and

Roll

Dialyzer

Experiments requiring large numbers of equilibrium dialyses across semipermeable membranes are unwieldy and time consuming. They become more practical if a means can be found to accelerate the rate of attaining equilibrium. Apparatus to do this has been designed by Calib and Algranati (1) , Ogston (2)) and Lauffer (3). None of these designsmet our requirements for multiple simultaneous dialyses, compact size (so that it would operate in a 3-cu ft refrigerator), and ease of operation. We wished to study equilibrium between metal ions and aqueous protein solutions (4, 5j at a temperature controlled to approximately 4OC. Figure 1 shows the apparatus (6) designed to meet these requirements. Each dialysis tube is placed on a drum of lo-in. diameter and length at an angle of 10” to the axis of rotation. The angle is achieved by mounting the polythene-coated clips skew to the axis of the drum. Rotation produces a rocking motion in each dialysis system by moving bubbles of air in each compartment. The drum is rotated by a 50-w AC motor at a fixed speed of 28 rpm using a simple reduction gear box. This motor is adequate to rotate the drum and a load of 4 kg provided the load is placed symmetrically round its circumference. The drum and stand are constructed of 22 s.w.g. aluminum sheet. The performance of the dialyzer was tested in a number of ways. In all experiments the same batch of Visking cellulose tubing was used. The distribution of ions across the membrane was assessedby a radioactive isotope dilution technique. In Fig. 2 the results are shown when 140 ml of .O.Ol M sodium chloride was dialyzed against 10 ml of distilled water inside a membrane. Equilibrium was achieved in 2 hr. Similar experiments using molar and 0.01 M solutions gave the same result. Cobalt (0.01 M) took 4 hr and ferric ions (O.Ol), 24 hr to reach equilibrium in similar systems in the presence of 0.05 M acetate (pH 4.2). The effect of varying the ratio of the volumes in the inner and outer compartments was tested using the ratios 1: 1, 1: 2, 1: 5, and 1: 14 with 0.01 M sodium ions. In all experiments 2 hr was required for equilibrium. 264

SHORT

FIG.

1. The

COMMl.INICATION

rapid

L I

rock

and

265

roll

dialgzer.

WI 2

9 3

4

Hours FIG. 2. Plot of difference in molarity tions of a dialysis system against time. against 140 ml of 0.1 M NaCl.

(M, - Mi) Ten milliliters

between inner and outer soluof distilled water was dialyzed

266

SHORT COMMUNICATION

Unstirred dialyses using 0.01 M NaCl required 24 hr and 0.01 M CoCl,, 36 hr to reach equilibrium. In comparison 0.01 M NaCl required 2 hr to reach equilibrium in a tilting table dialyeer tilting 28 times per minute. The advantage of the rapid dialyzer over the tilting table and other devices is that it is more compact and better suited to varying scales of dialysis. The machine tested had a capacity of 12 X 150 ml and 12 X 30 ml dialysis systems. ACKNOWLEDGMENT We wish

to acknowledge

the support

from

the free

funds

of St. George’s

Hospital.

REFERENCES E., AND ALGRANATI, I. D., Nature 188, 409 (1960). A. G., Arch. Biochem. Biophys. 89, 181 (1960). LAUFFER, M. A., Science 95,363 (1942). CODDINGTON, A., AND PERKINS, D. J., Biochim. et Biophys. PERKINS, D. J., Biochem. J. 80,668 (1961). U. K. Letters Patent 855,503 (1958).

1. CALIB,

2. 3. 4. 5. 6.

OGSTON,

Acta

44, 361 (1960).

A. M. STEWART D. J. PERKINS J. EL GREENING St. George’s Hospital Medical School 9, Knightsbridge London, S.W. 1, England Received September 1, 1961