The stability of some selected amino acids under attempted redox constrained hydrothermal conditions

In order to evaluate the stability of aspartic acid, serine, leucine, and a lanine under redox buffered hydrothermal conditions, a series of experiment s have been performed. The pyrite-pyrrhotite-magnetite (PPM) mineral assemb lage was used in the experimental systems in order to constrain the oxygen fugacity. Likewise, the K-feldspar-muscovite-quartz (KMQ) assemblage was ad ded to control the hydrogen ion activity during the experiments. The purpos e was to compare the relative stabilities in buffered and unbuffered experi ments. The experiments were conducted at 200 degrees C and 50 bar in Teflon coated autoclaves. Glycine, which was not present initially, started to ap pear at an early stage in the experimental systems and is believed to be th e result of decomposition of serine. Similarly, the increase in relative ab undance of alanine is likely to be the result of decomposition of serine. D ecomposition rates of leucine, alanine and aspartic acid were found to be l ower in experiments containing the redox buffer assemblage pyrite-pyrrhotit e-magnetite than in non-redox buffered experiments. The decomposition rate of serine was higher in buffered experiments, which indicates that a transf ormation pathway via dehydration of serine to dehydroalanine followed by re duction to alanine is promoted by reducing conditions.