Abstract
The formation of biopolymers in prebiotic environments is still unresolved regarding nucleic acids and functional peptides. Peptide function especially requires proper folding and hence sufficient lengths. In 1969, Cavadore and Previero1 observed that the EDC-mediated (EDC=1-ethyl, 3-(3-dimethylaminopropyl)carbodiimide hydrochloride) α-amino acid polymerization in water is significantly improved when N-acylated amino acids are introduced as initiators. Obviously, EDC is highly unlikely to have been abiotically formed but there are indications in the literature that underivatized carbodiimide HN[DOUBLE BOND]C[DOUBLE BOND]NH is involved as an intermediate in reactions of cyanamide,2 a prebiotically plausible reagent, and dicyandiamide is reported to behave similarly as carbodiimides.3 The behavior of N-acylamino acids as polymerization initiators was explained in the original work1 by an inhibition of activation owing to the greater acidity of free α-amino acids (pKA≈2.3) compared to C-terminal carboxy groups in peptides (pKA≈3.7). However, alternative explanations could be proposed.