The study of spectral and luminescent properties of humic acids and their impact on the photodegradation process of 2,6-bis(hydroxymethyl)-4-methylphenol

UV photolysis (KrCl excilamp, λrad ~ 222 nm) of aqueous humic acids (HAs) samples was carried out without and in the presence of 2,6-bis(hydroxymethyl)-4-methylphenol. The samples of HAs fractions were obtained from Aldrich Chemical Co and prepared from peat of Arkhangelsk region. The presence of Aldrich humic acid in the solution has a essential effect on the processes of phenolic compound photochemical degradation under the action of light from the excilamp.

A cyanosulfidic origin of the Krebs cycle

The centrality of the Krebs cycle in metabolism has long been interpreted as evidence of its antiquity, and consequently, questions regarding its provenance, and whether it initially functioned as a cycle or not, have received much attention. The present report shows that prebiotic oxidation of α-hydroxy carboxylates can be achieved by UV photolysis of a simple geochemical species (HS−), which leads to α-oxo carboxylates that feature in the Krebs cycle and glyoxylate shunt. Further reaction of these products leads to almost all intermediates of the Krebs cycle proper, succinate semialdehyde bypass, and glyoxylate shunt. Fumarate, the missing Krebs cycle component, and the required α-hydroxy carboxylates can be provided by a highly related hydrogen cyanide chemistry, which also provides precursors for amino acids, nucleotides, and phospholipids.