The possible role of Cu(II) for the origin of life

The most crucial prerequisite for the origin of life-most probably long before RNA/DNA-based reproduction could develop-was the formation of peptides and proteins under the conditions of the primitive earth. All reactions formerly proposed to have enabled this step of chemical evolution are highly questionable concerning their realizability under prebiotic conditions. However, the salt-induced peptide formation (SIPF) reaction, found some years ago, provides much more encouraging aspects for the creation of various peptides under such conditions. The necessary reagents-besides amino acids-are only sodium chloride and copper ions, and for both there is sufficient evidence of their presence on the primitive earth. The SIPF reaction occurs readily within a wide spectrum of environmental conditions (atmosphere, temperature etc.) and combines preferentially alpha-amino acids to peptides. Since it is applicable to all amino acids investigated so far, it has been possible to compare its preferentially formed peptide linkages with those found in the membrane proteins of the oldest still living organisms, namely archebacteria. The coincidence of these preferences is so high that it could have occurred by chance only with a probability of 10(-18). This leads to the conclusions that the SIPF reaction has been the basis for the formation of first peptide and protein matrices on earth (later reproduced by other, more efficient mechanisms and thus conserved, with some evolutionary variations, in these old organisms until now) and that, hence, Cu(II) has played a most significant role in the origin of life on earth. (C) 1999 Elsevier Science S.A. All rights reserved.