It is well known that mineral surfaces play an important role as catalysts for abiotic polymerization of amino acids to form peptides, which are the main components of the first self-replicating system. Understanding ...It is well known that mineral surfaces play an important role as catalysts for abiotic polymerization of amino acids to form peptides, which are the main components of the first self-replicating system. Understanding the mechanism behind the adsorption of simple amino acids on mineral surfaces is a topic of great interest not only in field of prebiotic evolution and but also in many other branches of material sciences. Various clay minerals have been suggested for studying how organic molecules were first synthesized in a prebiotic “inorganic” environment. Among them, pyrite (FeS<sub>2</sub>) is one of the most potential minerals as it possesses a highly reactive surface to drive molecular adsorption in prebiotic chemistry reactions. Recent theoretical experiments suggest that amino acids are adsorbed on the pyrite surface depending on its surface structures. However, these results have not been tested experimentally, and the exact mechanism of the specific interactions on this mineral has not been fully resolved yet at the molecular level. In this work, through quantitative force analysis with atomic force microscope (AFM) in which a single amino acid residue was mounted on the tip apex of AFM probe, we were able to find the reaction sites and study the interaction forces between the amino acid and the pyrite surface. Our results of Raman spectroscopic studies and force measurements with a well-designed AFM probe demonstrated for the first time that pyrite provided higher adsorption probabilities of amino acid residues for the chemical reactions at surfaces.展开更多
Two-dimensional self-assembly of melem at pH-controlled aqueous solution-Au（111） interfaces has been investigated by electrochemical scanning tunneling microscopy. In the solutions with pH 〉 pKbl of melem, two orde...Two-dimensional self-assembly of melem at pH-controlled aqueous solution-Au（111） interfaces has been investigated by electrochemical scanning tunneling microscopy. In the solutions with pH 〉 pKbl of melem, two ordered self-assembled structures （honeycomb and close-packed structures） and one disordered fibrillar structure were observed as a function of the surface coverage ofmelem controlled by the electrode potential. In contrast, in the acidic solution with pH 〈 pKbl of melem, only the self-assembled honeycomb network was observed in a relatively wide potential range probably due to the presence of monoprotonated melem cations. Dots attrib- uted to counteranions were frequently observed in the pores of the honeycomb network. The lack of close-packed and fibrillar structures at low pH （ 〈 pKbl） is attributed to ionic repulsion of melemium cations.展开更多
文摘It is well known that mineral surfaces play an important role as catalysts for abiotic polymerization of amino acids to form peptides, which are the main components of the first self-replicating system. Understanding the mechanism behind the adsorption of simple amino acids on mineral surfaces is a topic of great interest not only in field of prebiotic evolution and but also in many other branches of material sciences. Various clay minerals have been suggested for studying how organic molecules were first synthesized in a prebiotic “inorganic” environment. Among them, pyrite (FeS<sub>2</sub>) is one of the most potential minerals as it possesses a highly reactive surface to drive molecular adsorption in prebiotic chemistry reactions. Recent theoretical experiments suggest that amino acids are adsorbed on the pyrite surface depending on its surface structures. However, these results have not been tested experimentally, and the exact mechanism of the specific interactions on this mineral has not been fully resolved yet at the molecular level. In this work, through quantitative force analysis with atomic force microscope (AFM) in which a single amino acid residue was mounted on the tip apex of AFM probe, we were able to find the reaction sites and study the interaction forces between the amino acid and the pyrite surface. Our results of Raman spectroscopic studies and force measurements with a well-designed AFM probe demonstrated for the first time that pyrite provided higher adsorption probabilities of amino acid residues for the chemical reactions at surfaces.
基金This work was supported by a Grant-in-Aid for Young Scientists （A） （23681016） from the Ministry of Education, Culture, Sports, Science and Technology （MEXT）, Japan, and partly by the Hayashi Memorial Foundation for Female Natural Scientists and Technology Agency and the Tokuyama Science Foundation.
文摘Two-dimensional self-assembly of melem at pH-controlled aqueous solution-Au（111） interfaces has been investigated by electrochemical scanning tunneling microscopy. In the solutions with pH 〉 pKbl of melem, two ordered self-assembled structures （honeycomb and close-packed structures） and one disordered fibrillar structure were observed as a function of the surface coverage ofmelem controlled by the electrode potential. In contrast, in the acidic solution with pH 〈 pKbl of melem, only the self-assembled honeycomb network was observed in a relatively wide potential range probably due to the presence of monoprotonated melem cations. Dots attrib- uted to counteranions were frequently observed in the pores of the honeycomb network. The lack of close-packed and fibrillar structures at low pH （ 〈 pKbl） is attributed to ionic repulsion of melemium cations.
