METABOLIC IMPORTANCE OF AMINO ACID—LIPID COMPLEXES WSS 
incubation. The total radioactivity in the lipid complex rises from zero addition of 
carrier to a maximum at approx. 5 mg added. The total radioactivity then decreases 
to a value which is approx. 70% of the zero carrier amount and 40% of the maximum 
radioactivity value. This value is maintained even after extensive dilution. 
We also have been interested in the nature of the bonds which hold amino acid 
in such non-polar forms. In order to see if the carboxyl group of the amino acid was 
TABLE II 
FE%+ IRC-50 FRACTIONATION 





Mixture % of radioactivity in 
Amino Proline Palmitic H,0O wash 0.3 N HCl CH,OH :1N 
acid hydroxamate hydroxamate wash HCl 
GR as 
— 14C = 3 97 = 
[44C] Proline LE uC 45 55 — 
Leucine 
hydroxamate 
[4C]Glycine 12C 12C 93 5 2 
[24C] Alanine 12¢ 12 86 4 10 
(4C]Alanine + Alanine hydroxamate 
[44C]proline + Proline hydroxamate —- 96 2 2 

covalently linked to a lipid by an ester bond, we studied the reactions of our various 
amino acid—lipid complexes with hydroxylamine. It was first necessary to have an 
effective means of distinguishing between free amino acid, amino acid hydroxamate, 
and fatty acid hydroxamates. This was done by forming a column of weakly acidic 
ion-exchange material which was previously equilibrated with Fe**+ under controlled 
TABLE III 
FE%+ IRC-50 FRACTIONATION 
%, of radioactivity in 

CH,0H :1N 



Silicic acid fractions Ny 
H,0 wash o ay el Hol 
CHCl, peak II 65 24 
CHCl, peak 12 7o 19 
CHCl, : CH,OH (9 : 1): 1st part 41 39 20 
2nd part 53 20 27 
CHC), CHLOE (4:1): 1st part 25 15 60 
2nd part 9 71 20 
CHCl, : CH,OH (rz : 2) 34 10 56 

References p. 758 
