three random linear copolymers composed of two or three of the amino acids d-tyrosine , d-glutamic acid , d-alanine and d-lysine , and a branched multichain copolymer with a poly-d-lysine backbone and polymeric side chains of d-tyrosine and d-glutamic acid , were found to be non-antigenic in rabbits , by precipitin and passive cutaneous anaphylaxis , and in guinea pigs , by delayed hypersensitivity tests .
C0002520
amino acids
C0001898
alanine