METABOLISM OF PEPTIDES IN DROSOPHILA I 
Column fractionation. The work with injected larvae that were squashed directly on 
paper and then chromatographed made it clear that the system being studied was 
very complex. It was hoped that greater resolution could be obtained through the use 
of ion-exchange chromatography. After the injection of 7000 Drosophila larvae 
(approx. 5 g) with a mixture of L-[14C} glutamic acid and L-|C] leucine enough unin- 
jected animals were added to give a total weight of 51 g. The larvae were then ground 
with dry ice at —80° in an Omni-Mixer (Servall). The resulting powder was placed on 
a sintered glass funnel and extracted with goo ml of chloroform—methanol (2 : 1) 
yw MOLES 
COUNTS / MIN 

FRACTION NO. 
Fig. 6. Elution diagram resulting from the ion-exchange chromatography of a larval extract. The 
before-hydrolysis concentration of ninhydrin-positive material is indicated by the height of the 
open bars and the after-hydrolysis concentration by that of the black bars. Radioactivity is shown 
by the continuous black line. The fractions in which known amino acids were eluted are indicated. 
This information was obtained by separating a known amino acid mixture under the same con- 
ditions used in this experiment. Introduction of eluting solvents was started with ammonium 
formate buffer (pH 2.49, 0.05 M with respect to ammonium). After the collection of Fraction 11, 
elution was continued to Fraction 75 with this buffer. At this point a pH and concentration gra- 
dient was started by slowly introducing 0.1 17 ammonium formate buffer at pH 2.9 into the solvent 
reservoir (100 ml) containing the first buffer. Rapid mixing was assured by mechanical stirring. 
The addition of the pH-2.9 buffer continued until the introduction of the next buffer started. The 
other buffers, and the fraction at which their introduction into the mixing reservoir was started, 
were as follows: 
Buffer pH Molarity Fraction 
Ammonium formate 3.3 0.15 142 
Ammonium formate 3.65 0.2 191 
Ammonium acetate 5.5 0.4 259 
Ammonium acetate 6.8 0.6 29¢ 
Ammonium acetate 8.0 1.0 359 
Fractions eluted from the column were analyzed by the methods 
previously given. 
References p. 155 
