A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ],... more A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ], [NBu 4 ][Bi(dmit) 2 ] is reported. The vibrational spectrum and the molecular orbitals were calculated at the HartreeFock level of theory with the pseudo-potential SBKJC for Bi and a basis set ...
contributed by Adalberto Vieyra∗∗ There exists an extensive literature on the possible roles of m... more contributed by Adalberto Vieyra∗∗ There exists an extensive literature on the possible roles of minerals in the prebiotic stages of the chemical
The role of simple Chemical Demonstrations and Experimental Chemistry Courses needs to be revised... more The role of simple Chemical Demonstrations and Experimental Chemistry Courses needs to be revised in present days. Comments over difficulties and effectiveness are presented in this paper as a series of thoughts.
There exists an extensive literature on the possible roles of minerals in the prebiotic stages of... more There exists an extensive literature on the possible roles of minerals in the prebiotic stages of the chemical evolution of life (
Methyl p-dimethylaminobenzenesulfonate rearranges in the solid state, as a malt, and in solution ... more Methyl p-dimethylaminobenzenesulfonate rearranges in the solid state, as a malt, and in solution to a zwitterionic product, p-trimethylammoniumbenzenesulfonate. By a combination of kinetic and field desorption mass spectrometric techniques, we have found that the reaction is intermolecular and that it proceeds at a considerably faster rate in the crystal than it does either in the melt or in solution. The structure of the starting sulfonate has been solved by single crystal x-ray diffraction, and this study revealed that the molecules in the crystal are nearly ideally oriented for reaction in the solid state. Powder diffraction studies have shown that due to the constraints of the starting crystal lattice, the product is initially formed in a metastable crystalline form which slowly reverts to its thermodynamically most stable crystalline modification. 100 46 3 43 44 61 49 47 46 44 31
... (9) D. Dolphin, R. H. Felton, D. C. Borg, and J. Fajer, J. Am. Chem. Soc.. ... Chaim N. Suken... more ... (9) D. Dolphin, R. H. Felton, D. C. Borg, and J. Fajer, J. Am. Chem. Soc.. ... Chaim N. Sukenik," Jose A. P. BonapaceI2 Neil S. Mandel, Robert G. Bergman*13 Contribution No, 5079, Laboratories of Chemistry California Institute of Technology Pasadena, California 91 125 ...
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 1975
The coordination about the cobalt atom is closely octahedral with average Co-CI and CoN distances... more The coordination about the cobalt atom is closely octahedral with average Co-CI and CoN distances of 2.255 (2) and 1.987 (3) A respectively.
ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ... more ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ENVIRONMENTS ADALBERTO VIEYRA1, ANA ... in artificial seawater promotes breakdown of the (3, 7-and the a,(}-phosphoanhydride bond of ATP ...
ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ... more ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ENVIRONMENTS ADALBERTO VIEYRA1, ANA ... in artificial seawater promotes breakdown of the (3, 7-and the a,(}-phosphoanhydride bond of ATP ...
Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affect... more Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P i sorption whereas mild alkaline media-as well as those simulating sulfur oxidation to SO 2− 4-revert this capture process. Several mechanisms relevant to P i availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg 2+ bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na + and K +). The increase of both the medium pH and the SO 2− 4 trapping by the mineral interface would provoke the release of sorbed P i due to charge polarization. Moreover it is shown that P i self-modulates its sorption, a mechanism that depends on the abundance of SO 2− 4 in the interface. The relevance of the proposed mechanisms of P i capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, sincesimilarly to contemporary aqueous media-inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity for P i could have trapped this molecule in an efficient manner, allowing its
Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affect... more Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P i sorption whereas mild alkaline media-as well as those simulating sulfur oxidation to SO 2− 4-revert this capture process. Several mechanisms relevant to P i availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg 2+ bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na + and K +). The increase of both the medium pH and the SO 2− 4 trapping by the mineral interface would provoke the release of sorbed P i due to charge polarization. Moreover it is shown that P i self-modulates its sorption, a mechanism that depends on the abundance of SO 2− 4 in the interface. The relevance of the proposed mechanisms of P i capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, sincesimilarly to contemporary aqueous media-inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity for P i could have trapped this molecule in an efficient manner, allowing its
Page 191. PHOSPHATE IMMOBILIZATION BY PRIMITIVE CONDENSERS Implications in the Availability of So... more Page 191. PHOSPHATE IMMOBILIZATION BY PRIMITIVE CONDENSERS Implications in the Availability of Soluble Phosphate in Abiotic Environments FERNANDO DE SOUZA-BARROS3, MARISA BM MONTE1, ANA CP DUARTE1 ...
A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ],... more A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ], [NBu 4 ][Bi(dmit) 2 ] is reported. The vibrational spectrum and the molecular orbitals were calculated at the HartreeFock level of theory with the pseudo-potential SBKJC for Bi and a basis set ...
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 1999
Minerals have been implicated in different catalytic processes during chemical evolution. It has ... more Minerals have been implicated in different catalytic processes during chemical evolution. It has been proposed that exergonic synthesis of pyrite (FeS2) could have served to promote the endergonic synthesis of biomonomers in early stages of life formation on Earth. The present study was aimed to investigate whether pyrite can adsorb nucleotides and oxo acids in the potentially mild prebiotic conditions found away from the hot hydrothermal vents. It is shown that pyrite strongly adsorbs adenosine 5'-triphosphate in an artificial medium that simulates primordial aqueous environments, and that adsorption is enhanced in the presence of acetate and in an oxygen-free atmosphere. Moreover, the mineral catalyzes the sequential hydrolysis of the gamma and beta phosphoanhydride bonds of the nucleotide.
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 2003
The present study is based on the proposal that if the aqueous phosphorus-capture mechanism by ir... more The present study is based on the proposal that if the aqueous phosphorus-capture mechanism by iron oxide precursors was inhibited in prebiotic anoxic scenarios then soluble phosphates could have been more available than what is observed now. Supporting this conjecture, we examine prevailing contemporary trapping mechanisms of orthophosphate (Pi) and pyrophosphate (PPi). To illustrate its efficiency, the attachment of (Pi) onto aggregates of iron-3 oxyhydroxide is compared with the one reported for the product of its condensation, PPi. The electrophoretic profiles of the Pi- and PPi-aggregate complexes reveal different pH-modulated interactions of the phosphorylated compounds with both the aggregate and its aqueous surrounding layers. The observed differences of Pi/PPi sorption and desorption mechanisms are discussed in terms of their consequences to the prebiotic availability of soluble orthophosphate and of a phosphorylated compound having the high-energy phosphoanhydride linkage ...
A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ],... more A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ], [NBu 4 ][Bi(dmit) 2 ] is reported. The vibrational spectrum and the molecular orbitals were calculated at the HartreeFock level of theory with the pseudo-potential SBKJC for Bi and a basis set ...
contributed by Adalberto Vieyra∗∗ There exists an extensive literature on the possible roles of m... more contributed by Adalberto Vieyra∗∗ There exists an extensive literature on the possible roles of minerals in the prebiotic stages of the chemical
The role of simple Chemical Demonstrations and Experimental Chemistry Courses needs to be revised... more The role of simple Chemical Demonstrations and Experimental Chemistry Courses needs to be revised in present days. Comments over difficulties and effectiveness are presented in this paper as a series of thoughts.
There exists an extensive literature on the possible roles of minerals in the prebiotic stages of... more There exists an extensive literature on the possible roles of minerals in the prebiotic stages of the chemical evolution of life (
Methyl p-dimethylaminobenzenesulfonate rearranges in the solid state, as a malt, and in solution ... more Methyl p-dimethylaminobenzenesulfonate rearranges in the solid state, as a malt, and in solution to a zwitterionic product, p-trimethylammoniumbenzenesulfonate. By a combination of kinetic and field desorption mass spectrometric techniques, we have found that the reaction is intermolecular and that it proceeds at a considerably faster rate in the crystal than it does either in the melt or in solution. The structure of the starting sulfonate has been solved by single crystal x-ray diffraction, and this study revealed that the molecules in the crystal are nearly ideally oriented for reaction in the solid state. Powder diffraction studies have shown that due to the constraints of the starting crystal lattice, the product is initially formed in a metastable crystalline form which slowly reverts to its thermodynamically most stable crystalline modification. 100 46 3 43 44 61 49 47 46 44 31
... (9) D. Dolphin, R. H. Felton, D. C. Borg, and J. Fajer, J. Am. Chem. Soc.. ... Chaim N. Suken... more ... (9) D. Dolphin, R. H. Felton, D. C. Borg, and J. Fajer, J. Am. Chem. Soc.. ... Chaim N. Sukenik," Jose A. P. BonapaceI2 Neil S. Mandel, Robert G. Bergman*13 Contribution No, 5079, Laboratories of Chemistry California Institute of Technology Pasadena, California 91 125 ...
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 1975
The coordination about the cobalt atom is closely octahedral with average Co-CI and CoN distances... more The coordination about the cobalt atom is closely octahedral with average Co-CI and CoN distances of 2.255 (2) and 1.987 (3) A respectively.
ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ... more ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ENVIRONMENTS ADALBERTO VIEYRA1, ANA ... in artificial seawater promotes breakdown of the (3, 7-and the a,(}-phosphoanhydride bond of ATP ...
ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ... more ADSORPTION AND CATALYSIS OF NUCLEOTIDE HYDROLYSIS BY PYRITE IN MEDIA SIMULATING PRIMEVAL AQUEOUS ENVIRONMENTS ADALBERTO VIEYRA1, ANA ... in artificial seawater promotes breakdown of the (3, 7-and the a,(}-phosphoanhydride bond of ATP ...
Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affect... more Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P i sorption whereas mild alkaline media-as well as those simulating sulfur oxidation to SO 2− 4-revert this capture process. Several mechanisms relevant to P i availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg 2+ bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na + and K +). The increase of both the medium pH and the SO 2− 4 trapping by the mineral interface would provoke the release of sorbed P i due to charge polarization. Moreover it is shown that P i self-modulates its sorption, a mechanism that depends on the abundance of SO 2− 4 in the interface. The relevance of the proposed mechanisms of P i capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, sincesimilarly to contemporary aqueous media-inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity for P i could have trapped this molecule in an efficient manner, allowing its
Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affect... more Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P i sorption whereas mild alkaline media-as well as those simulating sulfur oxidation to SO 2− 4-revert this capture process. Several mechanisms relevant to P i availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg 2+ bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na + and K +). The increase of both the medium pH and the SO 2− 4 trapping by the mineral interface would provoke the release of sorbed P i due to charge polarization. Moreover it is shown that P i self-modulates its sorption, a mechanism that depends on the abundance of SO 2− 4 in the interface. The relevance of the proposed mechanisms of P i capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, sincesimilarly to contemporary aqueous media-inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity for P i could have trapped this molecule in an efficient manner, allowing its
Page 191. PHOSPHATE IMMOBILIZATION BY PRIMITIVE CONDENSERS Implications in the Availability of So... more Page 191. PHOSPHATE IMMOBILIZATION BY PRIMITIVE CONDENSERS Implications in the Availability of Soluble Phosphate in Abiotic Environments FERNANDO DE SOUZA-BARROS3, MARISA BM MONTE1, ANA CP DUARTE1 ...
A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ],... more A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate ], [NBu 4 ][Bi(dmit) 2 ] is reported. The vibrational spectrum and the molecular orbitals were calculated at the HartreeFock level of theory with the pseudo-potential SBKJC for Bi and a basis set ...
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 1999
Minerals have been implicated in different catalytic processes during chemical evolution. It has ... more Minerals have been implicated in different catalytic processes during chemical evolution. It has been proposed that exergonic synthesis of pyrite (FeS2) could have served to promote the endergonic synthesis of biomonomers in early stages of life formation on Earth. The present study was aimed to investigate whether pyrite can adsorb nucleotides and oxo acids in the potentially mild prebiotic conditions found away from the hot hydrothermal vents. It is shown that pyrite strongly adsorbs adenosine 5'-triphosphate in an artificial medium that simulates primordial aqueous environments, and that adsorption is enhanced in the presence of acetate and in an oxygen-free atmosphere. Moreover, the mineral catalyzes the sequential hydrolysis of the gamma and beta phosphoanhydride bonds of the nucleotide.
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 2003
The present study is based on the proposal that if the aqueous phosphorus-capture mechanism by ir... more The present study is based on the proposal that if the aqueous phosphorus-capture mechanism by iron oxide precursors was inhibited in prebiotic anoxic scenarios then soluble phosphates could have been more available than what is observed now. Supporting this conjecture, we examine prevailing contemporary trapping mechanisms of orthophosphate (Pi) and pyrophosphate (PPi). To illustrate its efficiency, the attachment of (Pi) onto aggregates of iron-3 oxyhydroxide is compared with the one reported for the product of its condensation, PPi. The electrophoretic profiles of the Pi- and PPi-aggregate complexes reveal different pH-modulated interactions of the phosphorylated compounds with both the aggregate and its aqueous surrounding layers. The observed differences of Pi/PPi sorption and desorption mechanisms are discussed in terms of their consequences to the prebiotic availability of soluble orthophosphate and of a phosphorylated compound having the high-energy phosphoanhydride linkage ...
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