Urea appears to be a key intermediate of important prebiotic synthetic pathways. Concentrated pools of urea likely existed on the surface of the early Earth, as urea is synthesized in significant quantities from hydrogen cyanide or cyanamide (widely accepted prebiotic molecules), it has extremely high water solubility, and it can concentrate to form eutectics from aqueous solutions. We propose a model for the origin of a variety of canonical and non‐canonical nucleobases, including some known to form supramolecular assemblies that contain Watson‐Crick‐like base pairs.The dual nucleophilic‐electrophilic character of urea makes it an ideal precursor for the formation of nitrogenous heterocycles. We propose a model for the origin of a variety of canonical and noncanonical nucleobases, including some known to form supramolecular assemblies that contain Watson‐Crick‐like base pairs. These reactions involve urea condensation with other prebiotic molecules (e. g., malonic acid) that could be driven by environmental cycles (e. g., freezing/thawing, drying/wetting). The resulting heterocycle assemblies are compatible with the formation of nucleosides and, possibly, the chemical evolution of molecular precursors to RNA. We show that urea eutectics at moderate temperature represent a robust prebiotic source of nitrogenous heterocycles. The simplicity of these pathways, and their independence from specific or rare geological events, support the idea of urea being of fundamental importance to the prebiotic chemistry that gave rise to life on Earth.
Uniform iron oxide magnetic nanoparticles have been synthesized using a microwave assisted synthesis method in organic media and their colloidal, magnetic, and relaxometric properties have been analyzed after its transference to water and compared with those nanoparticles prepared by thermal decomposition in organic media. The novelty of this synthesis relies on the use of a solid iron oleate as precursor, which assures the reproducibility and scalability of the synthesis, and the microwave heating that resulted in being faster and more efficient than traditional heating methods, and therefore it has a great potential for nanoparticle industrial production. The effect of different experimental conditions such as the solvent, precursor, and surfactant concentration and reaction time as well as the transference to water is analyzed and optimized to obtain magnetic iron oxide nanoparticles with sizes between 8 and 15 nm and finally colloids suitable for their use as contrast agents on Magnetic Resonance Imaging (MRI). The r2 relaxivity values normalized to the square of the saturation magnetization were shown to be constant and independent of the particle size, which means that the saturation magnetization is the main parameter controlling the efficiency of these magnetic nanoparticles as MRI T2-contrast agents.
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