214
S I L V I O R A N Z I
photometer after dilution 1 : 10 with solvent. Afterwards, lipids were
extracted by shaking with ethyl ether and the solution was then fractionated by the method of Derrien et al. (1952). Procedure was similar
to that shown in Fig. 1. In a series of 19 test tubes, the first contained
9 ml of Weber and Edsall fluid, the second 8-5 ml of the fluid and 0-5 ml
of a saturated solution of ammonium sulphate in Weber and Edsall
fluid, the third 8 ml of the Weber and Edsall fluid and 1 ml of the saturated solution of ammonium sulphate and so on, the nineteenth tube
receiving 9 ml of the saturated solution of ammonium sulphate alone;
1 ml of the protein solution was added to each test tube. After centrifugation, absorption of the samples was read in a Beckman spectrophotometer at 280 m/x. Absorption of the first sample (not containing
ammonium sulphate) was arbitrarily taken to be 100 and the differences
between successive samples were calculated.
This method is very reliable and it is possible to repeat the readings
on a solution of the same powder after one year's storage and obtain
identical results.
The nitrogen soluble in Weber and Edsall fluid was determined on the
3530
^ Μ 25H
20
Unfertilized
V:\\
20 40 60 60 C
FIG. 4. Salting-out diagrams for the unfertilized egg and hatching blastula of Arbacia
lixula. ~P l9 P 2 are two protein fractions synthesized during development inside the egg
envelope.