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Research concerning the ability of polycytidylate to direct and catalyze the synthesis of oligoguanylates from guanosine 5'-phosphate 2-methylimizadolide is discussed. Results demonstrate that small amounts of isomeric dimers are formed slowly in the absence of poly(C).

Research has been conducted on the aqueous solutions of deoxyguanosine. Results indicate that the initial rate of G (sub)2 (super)P demonstrates the dependence on 2-MeImpdG concentration.

The reactivity of the natural polyamines, spermine (spm) and spermidine (spd), with guanosine 5'-phosphate 2-methylimidazolide (2-MeImpG) generates guanosine 5'-phosphate-polyamine derivatives that are very stable for pHs between four and 11. This reaction indicates that the secondary amino groups of the polyamines are unreactive, probably due to a steric effect, leaving only the the primary groups to react with 2-MeImpG. Therefore, only two of the three possible spd products and only one of the two expected spm products are generated. The basicity of the two primary amino groups are identical.

Kinetic studies of the reaction of different aliphatic amines with phosphoimidazolide-activated of guanosine and cytidine (ImPN) derivatives reveal that kinetic barrier for the reaction increases with the size of the alkyl group in the aliphatic secondary amines. Kinetic data support the higher reactivity of the primary amino groups than the secondary amino groups toward ImPN. The slow reactivity accounts for the absence of substitution products of the secondary amino groups of the polyamines.

Two kinetic processes, observed in the hydrolysis of benzylideneacetylacetone in a strong basic medium, include fast step in the reversible OH- addition to the substrate to form T(sub OH)(super -) and the rate-determining step in the carbon protonation of T(sub OH)(super -) to form the products. pH jump experiments determine rate constants for all forward and reversible steps and are compared with those of the benzylidenemalondialdehyde and benzylidene Meldrum's acid hydrolysis.

The poly(C)-directed oligoguanylate synthesis from guanosine 5'-phosphate 2-methylimidazolide, 2-MeImpG is an extensively studied nonenzymatic polymerization. Only small samples of dimers and traces of trimers are seen in the absence of the template. The template is found to catalyze the process of elongation by 20-fold, but selectively enhances the 3'-5'-linkage formation by 140-fold. Mor-pG was selected as the nucleophile and 2-MeImpdG as the electrophile to study the dimerization of 2-MeImpG, resulting in a correlation between template concentration and diguanylate product yield and regioselectivity.

Phosphoimidazolide-activated derivatives of guanosine and cytidine 5'-monophosphates, henceforth called ImpN's, exhibit enhanced rates of degradation in the presence of aqueous inorganic phosphate in the range 4.0 < or = pH < or = 8.6. This degradation is been attributed to (i) nucleophilic substitution of the imidazolide and (ii) catalysis of the P-N bond hydrolysis by phosphate. The first reaction results in the formation of nucleoside 5'-diphosphate and the second in nucleoside 5'-monophosphate. Analysis of the observed rates as well as the product ratios as a function of pH and phosphate concentration allow distinction between various mechanistic possibilities. The results show that both H2PO4- and HPO4(2-) participate in both hydrolysis and nucleophilic substitution. Statistically corrected biomolecular rate constants indicate that the dianion is 4 times more effective as a general base than the monoanion, and 8 times more effective as nucleophile. The low Bronsted value beta = 0.15 calculated for these phosphate species, presumed to act as general bases in facilitating water attack, is consistent with the fact that catalysis of the hydrolysis of the P-N bond in ImpN's has not been detected before. The beta nuc = 0.35 calculated for water, H2PO4-, HPO4(2-), and hydroxide acting as nucleophiles indicates a more associative transition state for nucleotidyl (O2POR- with R = nucleoside) transfers than that observed for phosphoryl (PO3(2-)) transfers (beta nuc = 0.25). With respect to the stability/reactivity of ImpN's under prebiotic conditions, our study shows that these materials would not suffer additional degradation due to inorganic phosphate, assuming the concentrations of phosphate, Pi, on prebiotic Earth were similar to those in the present oceans ([Pi] approximately 2.25 micromoles).