THE BINDING AND REACTIONS OF NUCLEOTIDES AND POLYNUCLEOTIDES ON IRON-OXIDE HYDROXIDE POLYMORPHS

The iron oxide hydroxide minerals goethite and akaganeite were likely constituents of the sediments present in, for instance, geothermal reg ions of the primitive earth. They may have adsorbed organics and catal yzed the condensation processes which led to the origins of life. The binding to and reactions of nucleotides and oligonucleotides with thes e minerals was investigated. The adsorption of adenosine, 5'-AMP, 3'-A MP, 5'-UMP, and 5'-CMP to these minerals was studied. Adenosine did no t bind to goethite and akaganeite. The adsorption isotherms for the bi nding of the nucleotides revealed that they all had close to the same affinity for the mineral. Binding to goethite was about four times str onger than to akaganeite. There was little difference in the adsorptio n of each nucleotide suggesting the binding was between the negative c harge on the phosphate group and the positive charges on the mineral s urface. The absence of binding of adenosine is consistent with this ex planation. Binding decreases as the pH increases due to the titration of the positive (acidic) centers on the minerals. Two times as many mo les of polynucleotides were bound to these minerals as compared to the mononucleotides. Watson-Crick hydrogen bonding of adenosine and 5'-AM P to poly(U) complexes with goethite and akaganeite was observed. Ther e was no interaction of uridine with the poly(U)-goethite complex as e xpected if Watson-Crick hydrogen bonding is taking place. Neither goet hite nor akaganeite catalyzed the oligomerization of the phosphorimida zolide of adenosine (ImpA). The template directed synthesis of oligome rs of 5'-GMP on the poly(C) bound to goethite was observed. Higher mol ecular weight oligomers were observed when the poly(C) was bound to go ethite than was found in the absence of the mineral.