Amino acid stability and interactions with mineral surfaces.

摘要

Amino acids are the basic building blocks of proteins, one of the most important classes of biomolecules. The deep-sea hydrothermal vents have been often recognized as an exceptional microenvironment where chemical evolution of biomolecules might have occurred. The stability of biomolecules such as amino acids under such environments is of interest in various fields of study. Here I studied the stability of glutamate with and without reducing hydrothermal conditions imposed by 13 mmolar aqueous H2 at temperatures of 150 to 250 °C and initial pH values of 6 and 10. The results indicate that the amount of glutamate decomposition products depend on the temperature, the pH and particularly the redox state of the fluid. This result suggests that reducing hydrothermal environments may have been favorable for assembling the building blocks of biomolecules in the origin of life.;How abiotically formed biomolecules interact with mineral surfaces has been recognized as an important issue in that mineral surfaces may have played an important role in their selection, organization and concentration in the prebiotic era. In this study, I investigated the adsorption of the oppositely charged amino acids glutamate and lysine with and without the addition of Ca2+. Without Ca2+, glutamate shows a maximum in adsorption at a pH of ~4 and lysine shows a maximum in adsorption at a pH of ~9.4. In comparison, with calcium present, glutamate showed maxima in adsorption at both low and high pH, whereas lysine showed no adsorption at all. These dramatic effects can be described as cooperative adsorption between glutamate and Ca2+ and as competitive adsorption between lysine and Ca2+.;The mechanism by which amino acids attach to mineral surfaces is vital for understanding bioadhesion, biomineralization, and potentially the origin of life. I have conducted surface-enhanced Raman spectroscopy (SERS) measurements to probe the attachment configurations of L-DOPA on nano-rutile particles at different pH and surface coverages. The SERS spectra show peaks that progressively change with pH and surface coverage, indicating changing surface speciation. This observation provides a perspective on the possible role of mineral surfaces in the chemical evolution of biomolecules on early Earth.