RESUMEN
Compartmentalization is a major prerequisite for the origin of life on earth according to Wächtershäuser "Iron-Sulfur-World". The hypothesis is mainly based on an autocatalytic inorganic energy reproducing redox system consisting of iron and sulfur as requirement for the subsequent synthesis of complex organic structures. Here, we modified [FeFe]-hydrogenase models by means of covalent coupling to either oleic acid or the amphiphilic block copolymer polybutadiene-polyethyleneoxide (PB-PEO) and incorporated those into the membranes of vesicles composed of phospholipids (liposomes) or the unmodified amphiphilic polymer (polymersomes). We employed a [2Fe-2S] cluster as a hydrogenase model, since these structures are known to be suitable catalysts for the generation of H2 in the presence of weak acids. Successful incorporation was confirmed by spectrophotometric iron quantification and the vesicles formed were characterized by size determination (photon correlation spectroscopy (PCS)), and zeta potential as well as by cryo-transmission electron microscopy (Cryo-TEM). The modified models could be incorporated into liposomes or polymersomes up to molar proportions of 3.15% and 28%, respectively. Due to the immobilization in vesicular bilayers the [FeFe]-hydrogenase models can even exhibit catalytic action under the particular conditions of the intravesicular microenvironment. Our results suggest that the vesicular systems described may be applied as a nanoreactor for the reduction of encapsulated substances by generating hydrogen and thus as a minimal cell model.
Asunto(s)
Hidrógeno/química , Hidrogenasas/química , Hierro/metabolismo , Oxidación-Reducción , Azufre/metabolismo , Butadienos/química , Elastómeros/química , Espectroscopía de Resonancia por Spin del Electrón , Humanos , Hierro/química , Liposomas/química , Nanotecnología , Ácido Oléico/química , Polietilenglicoles/química , Azufre/químicaRESUMEN
According to Wächtershäuser's "Iron-Sulfur-World" one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on external energy sources, the "Iron-Sulfur-World" is based on the catalytic and energy reproducing redox system FeS+H2S-->FeS2+H2. The energy release out of this redox reaction (∆RG°=-38 kJ/mol, pH 0) could be the cause for the subsequent synthesis of complex organic molecules and the precondition for the development of more complex units similar to cells known today. Here we show the possibility for precipitating iron sulfide inside vesicles composed of amphiphilic block-copolymers as a model system for a first prebiotic unit. Our findings could be an indication for a chemoautotrophic FeS based origin of life.
Asunto(s)
Compuestos Ferrosos/química , Polímeros/química , Crecimiento Quimioautotrófico , Origen de la Vida , Oxidación-ReducciónRESUMEN
In search for peptidic [FeFe] hydrogenase mimics, the cyclic disulfide Sandostatin (octreotide) was allowed to react with Fe(3)(CO)(12). An octreotide-Fe(2)(CO)(6) complex was isolated and characterized spectroscopically as well as by elemental and thermochemical analysis. The complex catalyzes the electrochemical reduction of H(+) to H(2). It is suggested by radioligand binding assays that the complex retains much of the binding affinity for the somatostatin hsst(1-5) receptors of octreotide.
Asunto(s)
Antineoplásicos Hormonales/química , Carbonatos/química , Compuestos Férricos/química , Octreótido/química , Proteínas Bacterianas/química , Dominio Catalítico , Técnicas Electroquímicas , Humanos , Hidrogenasas/química , Proteínas Hierro-Azufre/química , Estructura Molecular , Somatostatina/químicaRESUMEN
The theory of chemoautotrophy, as developed by Wächtershäuser, has been subject to experimental studies, which show a possible carbon fixation pathway of several consecutive steps from simple CO2 to amino acids, using the redox system of iron sulphide and hydrogen sulphide. Main findings were a mimicking of the acetyl-CoA enzyme reaction using the mixed sulphide (Fe,Ni)S and the reduction of dinitrogen to ammonia. Present studies aim at a more detailed investigation of the mechanism of the redox system FeS/H2S and its properties. For these studies a method to produce and immobilise FeS nanoparticles has been developed.
Asunto(s)
Hidrógeno/química , Hierro/química , Oxidación-Reducción , Sulfuros/química , Amoníaco/química , Metabolismo Energético , Nanopartículas/química , Nitrógeno/químicaRESUMEN
Rydberg matter (RM) is a novel metal-like material in the form of electronically excited clusters of atoms (e.g. K and H) or molecules (e.g. H(2)). It is used as the inverted laser medium for IR in the RM laser. RM has recently been formed in its lowest state, which is proposed to be metallic hydrogen [Energy and Fuels 19 (2005) 2235]. An emitter material (K-doped iron oxide catalyst) that forms RM is studied by a specialized spectroscopic method, needed to detect the Rydberg states on the emitter surface. The spectroscopic method is phase-delay Rabi-flopping; it gives spectra from the time delay due to the periodic motion of the optical nutation vector. The formation of Rydberg species in the form of complexes K*-M (M a general small molecule) and (K-M)* is studied. So-called avoided transitions in K(+) ions are detected, of the same type as observed as transitions in the RM laser by stimulated emission. The formation and detection of Rydberg complexes containing H and H(2) is of great interest for metallic hydrogen production. Complexes with M=CH(2), H(2)O (or OH), CHO, H(2) and M'H are observed. Avoided transitions in RM clusters K(N)(*) are also identified. The identification of H containing Rydberg complexes on the surface indicates that metallic hydrogen is formed by the same cluster desorption route as other RM clusters.