A convenient device for multiple membrane filtration

384

SHORT COMMUNIChTIONS

angle to eliminate sharp bends in the tubing. B is converted into a multispray nozzle by piercing 4 small holes in it as shown. Assembly of the device is facilitated by first cutting a long taper in the end of the fine polyethylene tubing. The tubing is fed into the large end of the hose connection, A, and pulled nearly through. It is then passed through the angled hole, out the spray nozzle, and trimmed to the proper length. The large end of A is then connected to a water aspirator. The cuvette is tilted slightly so that the tip of the suction tube may be dipped into the lowest corner and the contents of the cuvette sucked out. With the suction tube still in posit.ion successive rinses from the wash bottle are sprayed down the sides of the cell and are similarly withdrawn. If water is used as the washing fluid, the cuvettes may be dried by employing a second rinser with acetone or alcohol. CARL P. CEPURNEEK Department of Biochemistry Purdue University Lafayette, Indiana Received June 23, 1964

A Convenient

Device

for

Multiple

Membrane

Filtration

Recent work involving the precipitation and subsequent counting of washed, radioactively labeled, acid-insoluble proteins and polynucleotides has been greatly facilitated by the development of a filtration technique involving the use of Millipore membranes.l Although this procedure greatly speeds such assays, individual manipulation involved in the filtration of each reaction mixture remains a time-consuming process. In order to extend the applicability of this t.echnique to large experiments, we have designed a device which will permit the simultaneous filtration of 45 samples and provide for the optional collection of both precipitate and filtrate.* The multiple filter consists of an air-tight stainless-steel case upon which fits an acrylic plastic template containing 45 stainless-steel screen ‘Nirenberg, M. W., GL “The Enzymes” (S. P. Colowick and N. 0. Kaplan, rds.), p, 17. Academic Press, New York, 1963. ‘Detailed plans for the fabricat,ion of the multiple filter apparatus map be obtained from Dr. Philip Leder, Nat,ional Heart Institute, Rethcsda, Md. 30014.

SHOHT

FIG.

:

COM.\IUh-lC.4TIOKS

I. Multiple

filtration

385

apparatus

“: .I.

.

FIG. 2. Multiple

.t

filtration

apparatus

showing

filtrate

collection

1-

_.

rack.

filter supports. After Millipore (or other) filter disks have been applied, the template is covered by a thick plastic plate forming an air-tight, seal with each filter disk, provitling a 15-ml well above each filter (Fig. 1 ). Those supports not in use may be plugged conveniently as pictured. When in use, the chamber is simply connected to vacuum and each precipitate containing sample is poured into its correspondingly numbered well, filtered, and washed as required. The upper plate is then removed, giving access to the washed filter disks which may be glued to planchets fol counting. If t,he filtrate is to be saved, a specially designed stainless-steel test-tube rack may be used so that a collection tube fits precisely beneath each filter well (Fig. 2). In our experience, a skilled operator can filter, wash, and prepare 45 samples for radioactive counting in approximately 20 min. ACKNOWLEDGMENT The authors are indebted t,he membrane filtration-type the study of protein synthesis.

to Dr. Marshall assnp provided

W. Nirenberg, an extraordinarily

whose initial work useful technique

on for

P. LEDER

C. J. Seclion on Biochemical Genetics National Heart Instit,ute and Instrument, Engineering and Development lVntiorin1 Institutes of Ncrrltlr lkthesdu, Maryland Received June 25. lUC;,$

An

Apparatus

for of

Brtrnch

Large-Scale

Biological

BYRNE

Lyophilization

Material1

For several years we have been collecting leaf material during the growing season and preserving it fo1 subsequent biochemical analyses by ;L procedure originally tlescribed by Levitt (1 1. In this method, fresh leaf Iuaterial is frozen directly in liquid air or nitrogen and then spread over alumina in a vacuum tlcsiccator. The desiccator is then closed and evacu:ited with an attached vacuum pump. After removal of the air the container is stored in a cold room at 2°C for two days for removal of water from the tissues. Leaf material is then removed, ground in a Wiley mill, 1 Contribution Number 2765.

from

the

Missouri

Agricultural

Experiment

Station.

Journal

Series