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Project Progress

The role of hydrogen cyanide polymer chemistry in the origin of life has provoked much speculation. In spite of extensive efforts by many groups, a satisfactory understanding of this polymer’s structure and mechanism of formation still eludes us. Our studies involve the synthesis of HCN polymers under a variety of conditions and the application of modern powerful analytical methods for structure elucidation. Several significant results have been obtained in the last year.

Synthesis of H¹³C¹⁵N polymers and solids NMR analysis.

Despite the profound implications for prebiotic chemistry raised by these materials, full characterization of these intractable heteropolymers has not yet been achieved. As a non-degradative analysis tool, Solid-State Nuclear Magnetic Resonance (SS-NMR) lends itself well to the structural investigation of such complex materials. For this work, ¹³C/¹⁵N labeled (30%) samples of the HCN heteropolymer were prepared and analyzed before and after treatment with H₂O using ¹H/¹³C and ¹H/¹⁵N Cross-Polarization (CP), ¹H/¹³C/¹⁵N Double Cross Polarization (DCP) and single resonance SS-NMR experiments. Spectral assignment of ¹³C and ¹⁵N SS-NMR data verifies that (HCN)x exists as a complex heteropolymer with a wide range of functionality and that a high concentration of N heteroaromatics is present. The initially formed sample is high in DAMN, D in Figure 1, which is removed upon the contact with water. Amide- and acid-like functionalities are seen to increase upon water treatment as well, consistent with the polyamidine model, B (Minard et al. 1975). Little signal attenuation is seen for the ¹³C DCP result (relative to CP) on the native sample, and this result may suggest that the structure C seen in Figure 1 is not present to a significant extent. In contrast, ¹⁵N DCP spectra of the native sample show more prevalent signal attenuation (relative to CP) and lend support for the structures A and E.

A Test for Polyaminomalononitrile as an Intermediate in HCN Polymerization

In 1966, Matthews proposed that HCN polymerizes through a series of reactions depicted in Figure 2, leading to the direct formation of “primordial proteins.” In order to test the validity of Matthews’ pathway, the presence of the intermediate polyaminomalononitrile or poly-a-cyanoamidine, 3, is examined by looking for its reaction with acrylonitrile, an experiment suggested by Eschenmoser. Increased amounts of glutamic acid are observed in the final hydrolysis products of HCN polymer treated with base and acrylonitrile, presumably via the Michael addition reaction shown. Likewise, addition of formaldehyde to HCN polymer leads to the formation of significant quantities of the amino acid serine in its hydrolysis products.

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References:

Minard, R.D.; Yang, W.; Varma, P.; Nelson, J.; Matthews, C.N.: 1975; Heteropolypeptides from poly-a-cyanoglycine and hydrogen cyanide. Model for the origin of proteins, Science (1975), 190(4212), 387-9

Minard, R.D., Hatcher, P.G., Gourley, R.C., Matthews, C.N.: 1998, Origins of Life and Evolution of the Biosphere, 28, 461-473.