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From an origin-of-life perspective, processes able to provide energy to feed self-or­ ganizing systems are required for the formation of their own components but also to maintain a far from equilibrium state essential for the system to remain under kinetic control. a-Amino acid N-carboxyanhydrides (NCAs) and 5(4H)-oxazolones represent activated intermediates of the chemistry of peptides that may be involved in the self-organization of life and in the evolution of translation. An experimental survey of previously published activating agents has been carried out using the epi­ merization associated with the transient formation of 5(4H)-oxazolones as a tool to monitor their potential to promote strong activation. None of reagents investigated in this survey proved to be totally satisfactory demonstrating that the identification of activation processes remains a crucial goal in this field. ispartof: Journal of Systems Chemistry vol:7 issue:1 pages:29-37 status: published

The authors compare the enantiomeric cross-inhibition of D- and L-guanosine 5'-phosphoro-2-methyl-imidazole (I) polymn. on C10 (RNA), dC10 (DNA), or hC10 (hexitol nucleic acid) (II). RNA or DNA templates catalyze efficient oligomerization of D-I, with a strong enantiomeric cross-inhibition by L-I, but II shows efficient oligomerization of D-I with a less sever cross-inhibition, resulting in G6-9 polymers, thus showing that efficient selection of one optical isomer from a racemic mixt. of nucleotides during nonenzymic oligo-nucleotide synthesis on an analog of a nucleic acid template is possible, which may be of relevance to prebiotic conditions. [on SciFinder (R)]

The synthesis and a preliminary evaluation of the pairing properties of ribo-cyclohexanyl nucleic acids (r-CNA) is herein reported. Incorporation of a single r-CNA nucleotide into natural duplexes did not enhance their stability, while a very high pairing selectivity for RNA was found. As deduced by comparative analysis of Tm and NMR data, a relationship between pairing selectivity and conformational preferences of the "sugar" moiety of r-CNA (and more generally of six-membered nucleic acids) was suggested.

The synthesis and a preliminary investigation of the base pairing properties of (6′ → 4′)-linked 1′,5′-anhydro-l-ribo-hexitol nucleic acids (α-l-HNA) have herein been reported through the study of a model oligoadenylate system in the mirror image world. Despite its considerable preorganization due to the rigidity of the “all equatorial” pyranyl sugar backbone, α-l-HNA represents a versatile informational biopolymer, in view of its capability to cross-communicate with natural and unnatural complements in both enantiomeric forms. This seems the result of an inherent flexibility of the oligonucleotide system, as witnessed by the singular formation of iso- and heterochiral associations composed of regular, enantiomorphic helical structures. The peculiar properties of α-l-HNA (and most generally of the α-HNA system) provide new elements in our understanding of the structural prerequisites ruling the stereoselectivity of the hybridization processes of nucleic acids.

Methods and protocols for automated synthesis and purification of locked nucleic acid (LNA), a class of oligonucleotides obeying the Watson-Crick base-pairing rules but displaying unprecedented binding affinities toward complementary deoxyribonucleic acid (cDNA) and ribonucleic acid (RNA), is described. LNA and LNA-DNA chimeras containing phosphordiester or phosphorothioate linkages, or a mixture thereof, can be assembled by standard DNA synthesizers using 2-cyanoethyl DNA phosphoramidites and 2-cyanoethyl LNA phosphoramidites. Compared to the standard protocols used for DNA synthesis, slightly longer coupling time and oxidation time are needed for efficient oligomerization of LNA phosphoramidites. When the LNA has been assembled, it is removed from the solid support as the 5'-end-O-dimethoxytrityl (DMT) protected LNA oligomer by treatment with concentrated aqueous ammonia that also removes the phosphate and nucleobase protecting groups. The crude DMT protected LNA product can be purified using, for example, reversed-phase chromatography.