Prebiotic synthesis of histidine and histidyl-histidine : studies of catalytic activities of histidyl-histidine in prebiotic reactions



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The syntheses of imidazole, imidazole derivatives(2-Me-Im, 4-Me-Im), histidine precursor(4-Im-acetaldehyde), histidine have been demonstrated under plausible primitive earth conditions. The histidyl-histidine was synthesized by the cyanamide-mediated reaction of the aqueous solution of histidine. The possible catalytic activities of histidyl-histidine have been tested in some prebiotic reactions in this investigation. The syntheses of imidazole from glyoxal, formaldehyde and ammonia; 2-methylimidazole from glyoxal, acetaldehyde and ammonia; and 4-methylimidazole from glucose and ammonia have been demonstrated under plausible prebiotic conditions. The imidazole and its derivatives obtained by those methods were analyzed by paper chromatography using diazo reagent, and by gas chromatography-mass spectrometry. Several imidazole derivatives, as histidine precursors, have been synthesized from the prebiotic precursors. Imidazole-4-acetaldehyde and imidazole-4-glycol were synthesized from erythrose and formamidine; imidazole-4-glycol and imidazole-4-ethanol were synthesized from erythrose, formaldehyde and ammonia. The products were identified by TLC, HPLC, and LC/MS by comparison with authentic samples. Imidazole-4-acetaldehyde would have been an intermediate molecule for the prebiotic formation of histidine, and several prebiotic reactions would convert imidazole-4-glycol and imidazole-4-ethanol to imidazole-4- acetaldehyde. [...]