Partition Cell for Spinco Preparatory Ultracentrifuge. Ole Arne Schjeide and Reginald IT,Dickinson, .4tomic Energy Project, School of Medicine, University of California a t Los Angeles, Calif.
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cially re-enforced x i t h sheets of glass wool situated horizontally to the cylinder. These have remained intact during several centrifugations at 30,000 r.p.m. LITERATURE CITED
methods developed by Gofman and his associates (1, 2 ) for the stratification of serum proteins in the Spinco preparatory ultracentrifuge (Model L ) are now widely used, but in many cases there is nerd for a simple device for the preci-e partitioning of such layers of protein. This laboratory is now u-ing a specially devised partition cell (Figure 1) for the Spinco preparatory ultracentrifuge. HE
This consists in part of a stack of five clear Lucite disks 3/s inch thirk machined to fit loosely into a Lustrroid tube, A , 1 inch in diameter. The disks have a center hole 3/16 inch in diameter, in a hich the serum to be centrifuged is placed. A second hole for the insertion of an alignment rod, B , is located near the edge of each disk. The rod is also used to lift the partition cell assembly out of the Lusteroid tube. Two other plastic disks, solid except for the offset holes. serve as bottom plate and cap in the paltition cell assembly. The offset hole in the bottom plate is threaded to fit the end of the alignment rod. A plastic plug fills the round bottom of the Lusteroid tube. This tube fits snugly into the 30,000 r p ni. maximum rotor of the Spinco preparatory ultracentrifuge. The plastic disks are sealed together with a rubber-base stopcock grease (high vacuum stopcock grease, Type 111, obtained fiom Robert R. .4ustin, Box 3743, Pasadena 8, Calif.). The partition cells are assembled a t room temperature T\ ith the stopcock grease heated to 60" C. Serum is then pipetted into the cell until it is level with the top of the fourth plastic disk. The filled assemblv is chilled to 3" C. 2rior to centrifugation I-pon completion of centiifugatioii a t 3 C. the partition cell assembly is lifted out of the Lusteroid tube, the rod is withdrawn, and, beginning with the top disk, the disks are slid partially across each other so as to cut off the contents of each quarter in turn, L'. If it is desired to isolatp a stratum of material greater or less than one-quaiter cell, this ma>- be accomplished by sliding the partition cell assembly off the bottom disk onto a special plastic plate with a hole through which a plunger can be pushed, D JYhen the assembly is located so that the serum column is in line I\ ith the plunger, the plunger can be raised or 1015 ered, thus lifting or dropping the column to any desired level
(1) Gofman, J. W., Jones, H. B., Lindgren, F. T., Lyon, T. P., Elliott, H. A , , and Strisower, B., Circuletion, 2, 161 (1950). (2) Gofman, J. W., Lindgren, F. T., Elliott; H., Mants, W., Hewitt, J., Strisower, B., and Herring, V., Science, 3, 166 (1950). BASEDon work performed under Contract No. AT-04-1-GEN-12 between the -4tomic Energy Commission and the University of California a t Los Anpeles.
Papers Made from Inorganic Fibers a s Filter Mats for Gooch Crucibles. T . S. Ma. Chemistry Department, Sew York University, Sew York, X . T..a n d .4.A . Renedett,i-Pichler, Queens ('ollege, Flushing, S . T. prepared from glass fibers were used by Duval F.in his mats critical investigations with the thermobalance, and ILTER
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filter mats for Gooch crucibles prepared from silica fibers have been recommended by Russell and Harley ( 3 ) . Disks cut from unsized paper made from fibers of either glass or vitreous silica should combine the advantages of chemical stability and convenience. Such papers have been recently developed by the Sational Bureau of Standards ( d ) , a i d the glass fiber variety is becoming commercially available for general use. Because the fibers used are extremely fine, it is not surprising that the papers have the appearance of filter paper and are dense enough to retain very fine precipitates. Small amounts of organic binder used in some grades for increasing mechanical stability cannot be tolerated in analytical work, as significant amounts of binder are extracted during filtration. Binder may be easily removed, however, by moistening the paper disks in the Gooch crucible with some strongly oxidizing cleaning mixture and thoroughly washing with water after a few minutes of digestion. The chloride determinations mentioned below were performed lyith various grades of such binder-containing paper. Grade XY-934-rlH,0.009 to 0.010 inch, white, of the Hurlbut Paper Co., is free from organic admixtures and may he used as Thr Lucite diPk directly adjacent to the solid bottom disk freobtained from the factory. I t is probably because of the smooth quently fractured radially during the second or third centrifugasurface of the fibers that such a paper has a somewhat Ion-er tion, even though disks higher on the column successfully withmechanical stability and may begin to disintegrate during filtrastood many centrifugations. The authors therefore contracted tion under the impact of the liquid poured into the Gooch crucin ith Pearce Plastics Corp., Hollyn ood, Calif., to cast disks speble. This disadvantage is safely overcome by using two disks of paper, the top one serving to protect the disk in cont,act with the bottom of the crucible. The prepared filter mat should he washed briefly with water, or, still better, \yith a solution having the same reaction as the liquid to be filtered, for the removal of loose fibers and accidentally present soluble contaminants. The use of the glass fiber disks is extremely simple. Two disks which exactly fit the bottom are placed in the Gooch crucible, and 20 to 50 ml. of x a t e r are passed through the disks with the application of suction. The crucible is then dried and weighed. Before filtration is started, the disks of glass paper are cautiously moistened, and slight suction is applied to make them tightly adhere to the bottom of the crucible. Filtration, drying, cooling, and weighing are performed as usual. The inexpensive paper disks are discarded after use. Precipitates may be heated to temperatures up to 520' C. The u hygroscopicity and chemical resistance of the glass fiber papers B C I are naturally determined by the kind of glass used for the fibers. ONE INCH A Grade X-934-AH compares favorably in these respects with Figure 1. ' Partition Cell Jena filter crucibles having bottoms of fritted glass. There is no
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