Structural Properties of Hachimoji Nucleic Acids and Their Building Blocks: Comparison of Genetic Systems with Four, Six and Eight Alphabets.

Expansion of the genetic alphabet is an ambitious goal. A recent breakthrough has led to the eight-base (hachimoji) genetics having canonical and unnatural bases. However, very little is known on the molecular-level features that facilitate the candidature of unnatural bases as genetic alphabets. Here we amalgamated DFT calculations and MD simulations to analyse the properties of the constituents of hachimoji DNA and RNA. DFT reveals the dominant syn conformation for isolated unnatural deoxyribonucleosides and at the 5'-end of oligonucleotides, although an anti/syn mixture is predicted at the nonterminal and 3'-terminal positions. However, isolated ribonucleotides prefer an anti/syn mixture, but mostly prefer anti conformation at the nonterminal positions. Further, the canonical base pairing combinations reveals significant strength, which may facilitate replication of hachimoji DNA. We also identify noncanonical base pairs that can better tolerate the substitution of unnatural pairs in RNA. Stacking strengths of 51 dimers reveals higher average stacking stabilization of dimers of hachimoji bases than canonical bases, which provides clues for choosing energetically stable sequences. A total of 14.4 µs MD simulations reveal the influence of solvent on the properties of hachimoji oligonucleotides and point to the likely fidelity of replication of hachimoji DNA. Our results pinpoint the features that explain the experimentally observed stability of hachimoji DNA.

Clinical Consequences of Untreated Dental Caries Evaluated with the Pulpal Involvement-Roots-Sepsis Index in the Primary Dentition of School Children from the Raipur and Durg Districts, Chhattisgarh State, India.

Objective: To evaluate the prevalence of the clinical consequences of untreated dental caries in primary dentition among 6- to 8-year-old children using the prs [pulpal involvement (p), roots (r) and sepsis (s)] index and record the distribution of prs among boys and girls. Subjects and Methods: The study included a sample of 371 children aged 6-8 years with at least one carious primary molar tooth, who had been randomly selected from schools in the districts of Raipur and Durg, Chhattisgarh State, India. We recorded the presence of decayed, extracted and filled (i.e. def) teeth. The prevalence of the consequences of untreated dental caries was evaluated using the prs index. The data were statistically analyzed to express the prevalence of prs among boys and girls and the distribution of individual prs codes in the sample population. Results: The prevalence of carious lesions was very high (87%) and teeth with clinical consequences of untreated dental caries were found in 49.3% of the children. The prs distribution in children who were 8 years old (40.9%) was higher than in the 6-year-old children (25.6%). In the group of 8-year-olds, the occurrence of prs was greater among the boys whereas in the 6- and 7-year-old group, it was greater among the girls. Conclusion: The prs index is a valuable tool for measuring the clinical consequences of untreated dental caries. It could be useful for epidemiological studies and provide relevant information regarding treatment needs. © 2014 S. Karger AG, Basel.