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Results for “Origin of Life”

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At least 343 records · Page 19Linked to original sources
PubMed2006

Social circumstances and education: life course origins of social inequalities in metabolic risk in a prospective national birth cohort.

OBJECTIVES: We investigated the relative importance of education and childhood and adult social class in the risk of metabolic syndrome. METHODS: We conducted a prospective birth cohort study of 1311 men and 1318 women aged 53 years in 1999, when metabolic syndrome components were measured. Logistic regression analyses were used to calculate relative index of inequality estimates. RESULTS: Relative to men and women at the highest education levels, men (odds ratio [OR]=2.0; 95% confidence interval [CI]=1.2, 3.2) and women (OR=2.7; 95% CI=1.5, 4.6) with the least education were at twice the risk or more of having the metabolic syndrome. Adjustment for childhood and adult social class strengthened this result among men and weakened it among women. Childhood social class was independently associated with the metabolic syndrome in women (OR=2.0; 95% CI=1.1, 3.6) but not in men (OR=1.1; 95% CI= 0.7, 1.8). Associations between adult social class and the metabolic syndrome or its components were largely accounted for by childhood socioeconomic measures. CONCLUSIONS: Educational differences should be considered in the design of interventions aimed at reducing the burden of the metabolic syndrome in socially disadvantaged groups.

Child, Preschool↗
PubMed1973

The origin of life.

Explore the source record for details and available documents.

Biochemical Phenomena↗
PubMed1995

Hypercycles versus parasites in the origin of life: model dependence in spatial hypercycle systems.

Spatial hypercycle systems can be modelled by means of cellular automata or partial differential equations. In either model, two dimensional spirals or clusters can be formed. Different models give rise to slightly different spatial structures, but the response to parasites is fundamentally different: In cellular automata the hypercycle is resistant to parasites that are fatal in a partial differential equations model. In three dimensions scroll rings correspond to the two dimensional spirals. Numerical simulations on a partial differential equations model indicate that the scroll rings are unstable: The contract by a power law and disappear. Therefore, in three dimensions clusters seem to be the best candidate for the hypercycle resistant to parasites.

Computer Simulation↗
PubMed1991

Catalytic activity of aminoacyl tRNA synthetases and its implications for the origin of life. I. Aminoacyl adenylate formation in tyrosyl tRNA synthetase.

The changes in the catalytic activity resulting from amino acid substitutions in the active site region have been theoretically modeled for tyrosyl tRNA synthetase (Tyr-RS). The catalytic activity was calculated as the differential stabilization of the transition state using electrostatic approximation. The results indicate that charged residues His45, His48, Asp78, Asp176, Asp194, Lys225, Lys230, Lys233, Arg265, and Lys268 play essential roles in catalysis of aminoacyl adenylate formation in Tyr-RS, which is in general agreement with previously known experimental data for residues 45, 48, 194, 230, and 233. These catalytic residues have also been used to search for sequence homology patterns among class I aminoacyl RSs of which HIGH and KMSKS conserved sequence motifs are well known. His45 and His48 belong to the HIGH signature sequence of class I aminoacyl tRNA synthetases (aRSs), whereas Arg265 and Lys268 can constitute a part of the KMSKS charge pattern. Lys225, Lys230, and Lys233 may be part of the conservative substitution pattern [HKR]-X(4)-[HKR]-X(2)-[HKR], and Asp194 is part of the new GSDQ motif. This demonstrates that the three dimensional charge distribution near the active site is an essential feature of the catalytic activity of aRS and that the theoretical technique used in this work can be utilized in searches for the catalytically important residues that may provide a clue for a charge residue pattern conserved in evolution. The appearance of patterns I-IV in Arg-, Gln-, Met-, Ile-, Leu-, Trp-, Val-, Glu-, Cys-, and Tyr-RS indicates that all these enzymes could have the same ancestor.

Amino Acid Sequence↗
PubMed2006

Re-creating an RNA world.

The RNA world hypothesis states that life originated via a system based on RNA genomes and RNA catalysts. Researchers have been trying to develop such a system since catalytic RNAs (ribozymes) were discovered in 1982. This review summarizes the recent progress made in that endeavor and outlines the obstacles that remain to be overcome. After giving a short background on prebiotic chemistry and in vitro evolution, the discussion focuses on the generation of three important components of an RNA world: a sufficient polymerase ribozyme, self-replicating membrane compartments and ribozymes that are capable of performing basic metabolic processes.

Evolution, Molecular↗