Cristóbal viedma

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                                                                       Research Interests

       

Crecimiento de cristales en la naturaleza  y en la industria con especial interés en la nucleación  y crecimiento con transporte de masa por difusión y capilaridad. Cristalización de proteínas.

Generación espontánea y propagación de asimetría quiral en cristalización y en la naturaleza. Resolución de aminoácidos sobre superficies minerales: implicaciones en el origen de la bioquiralidad

Auto-organización mineral versus auto-organización orgánica: implicaciones en la química pre-biótica. Efecto catalítico y de orden entre moléculas y minerales: biomineralizacion,  minerobiogénesis y morfologías biomiméticas.

Planetas y cuerpos del sistema solar: aspectos geológicos con implicaciones astrobiológicas

                             "The way up and the way down are  one and the same"                            (Heraclitus)    

      

 

                                A few examples of my Research and Recent Research

La formación  de proto-proteinas en los primeros estadios de la química prebiótica es un misterio sin resolver ¿Como pudo generarse el enlace peptídico entre los primeros aminoacidos en un ambiente geológico plausible?

 

Peptide bonds formation was attempted by thermal activation of dry amino acids from aqueous solution that simulated prebiotic evaporative environments. The evaporation trend of amino acids solutions shows a bifurcation and can lead to either a crystalline phase (near equilibrium) or a metastable-non crystalline phase (far from equilibrium). Only amino acids in this metastable phase are able to form peptide bonds by thermal activation at temperatures that are generated by solar radiation today. We suggest that this metastable phase is the ideal initial material to trigger amino acid assemblage with protein-like structure because provide the driving force (supersaturation) for an intense interaction between monomers of different amino acids and allows activation of these monomers in plausible prebiotic conditions

 Origins of Life and Evolution of the Biosphere, 30: 549-556. Viedma (2000)

En este trabajo sintetizamos proto-proteinas en ambientes moderados y establecemos que la diferencia entre auto-organización cristalina y auto-organización orgánica (estado metastable) permite la formación  del enlace peptídico.

Optical microphotographs (x12) of a set of drops from the same solution of aminoacids B after evaporation and ageing for a few days during the ageing process, we selected some crystallized drops, some metastable drops and another one partially metastable-crystalline drop. All them were heated at 85ºC for 80 days. Only aminoacids in metastable state formed peptide bonds.

 

 

CÓMO CRECER BUENOS CRISTALES DE PROTEÍNAS Y    POR QUÉ

 

Para conocer la estructura tridimensional de una proteína y por tanto para conocer con exactitud  su función biológica hay que obtener cristales para  estudiarlos mediante rayos X. Obtener cristales de proteínas es muy difícil por la complejidad fisicoquímica de las interacciones a escala molecular. En este trabajo desarrollamos una técnica de cristalización de proteínas que soslaya todos los problemas planteados y ha generado los mejores cristales obtenidos hasta ahora en la Tierra

 

This paper provides a detailed description of a simple method to obtain large protein single crystals inside glass capillaries. The method is based upon the properties of gels, which are used to hold capillaries containing the protein solution, and also to act as the mass transport medium for the precipitating agent. Recipes for a set of selected experiments bringing a hands-on experience on the crystallization of different soluble proteins are supplied. These experiments are inexpensive and straightforward enough for teaching at the undergraduate level that large biological macromolecules that are the gate our structural studies and drug design can be crystallized. Using simple equations accounting for the solubility of proteins and for the nucleation process, the experimental results are explained to provide a rational approach to the problem. In addition, because of the nature of the crystallization method which is based on diffusion-reactions systems, the student is introduced to the meaning of self-organization. (Am. Chem. Soc., 75: 442-446 Material Research Bulletin, 28: 541-546.)

 En la estación espacial, en condiciones de microgravedad, se desarrollan los mejores cristales de proteínas
Cristales buenos sí, pero... ¿a qué precio y con cuantas dificultades?

Protein crystallization by the gel acupuncture method (Our method)      

Solo los cristales obtenidos con nuestra técnica de crecimiento  han sido capaces de competir en calidad y tamaño con los cristales del laboratorio espacial, pero a   bajo precio y con la cómoda rutina  del laboratorio  terrestre.

 

 

 
 

¿Por qué la luna de Júpiter, Europa, presenta  en su superficie helada,  un intrigante entramado geométrico de grietas con sales potencialmente pre-bióticas ?

 

The anti-Jovian hemisphere of Europa (the hemisphere opposite the one facing Jupiter) displays a complex array of fractures, including roughly concentric and arcuate ones. The geometry of this intriguing pattern on the icy surface of Europa resembles the textural features displayed by perlitic volcanic glass. We argue that fast cooling of a rhyolitic magma may serve as an analogue for fast supercooling of water leading to formation of amorphous ice (glassy water). We envisage two possible scenarios for ice melting and subsequent extremely fast supercooling: (1) massive subglacial volcanic activity or (2) a large impact on the anti-Jovian hemisphere. We suggest that extremely fast formation of amorphous ice on Europa would result in a fracture pattern geometrically equivalent to that observed in perlitic glass. Fast supercooling of water will initially lead to brine retention in the ice phase; however, after some time these brines would be laterally rejected toward fractures. Furthermore, as solidification progresses downward, a shrinking ocean would increase brine concentration. These brines would eventually escape to the surface via the fracture network. Finally, high-pressure crystallization of salts within fractures may provide an efficient mechanism for differential plate separation, horizontal movement, and formation of new fractures. Geology Volume 28, Issue 10  (2000)

            

 

Nuestra explicación a la singular superficie de Europa está basada en consideraciones sobre las distintas fases del hielo que comporta diferentes respuestas mecánicas a esfuerzos y posibilita la presencia de océanos interiores. Al mismo tiempo consideramos la presión de cristalización del hielo como un agente importante en el proceso de concentración de sales  junto con el aporte oceánico.

 

          Recent Research
 
¿Qué pasó en el origen de la vida en la Tierra para que sólo aminoacidos  de izquierda y azucares de derechas entraran en el juego de la evolucion biológica?

Chiral symmetry breaking occurs when a physical or chemical process spontaneously generates a large excess of one of the two enantiomers—left-handed (L) or right-handed (D)––with no preference as to which of the two enantiomers is produced. From the viewpoint of energy, these two enantiomers can exist with an equal probability, and inorganic processes that involve chiral products commonly yield a racemic mixture of both. The fact that biologically relevant molecules exist only as one of the two enantiomers is a fascinating example of complete symmetry breaking in chirality and has long intrigued the science community. The origin of this selective chirality has remained a fundamental enigma with regard to the origin of life since the time of Pasteur, some 140 years ago. Here, it is shown that two populations of chiral crystals of left and right hand cannot coexist in solution: one of the chiral populations disappears in an irreversible autocatalytic process that nurtures the other one. Final and complete chiral purity seems to be an inexorable fate in the course of the common process of growth-dissolution. This unexpected chiral symmetry breaking can be explained by the feedback between the thermodynamic control of dissolution and the kinetics of the growth process near equilibrium. This “thermodynamic-kinetic feedback near equilibrium” is established as a mechanism to achieve complete chiral purity in solid state from a previously solid racemic medium. The way in which this mechanism could operate in solutions of chiral biomolecules is described. Finally, based on this mechanism, experiments designed to search for chiral purity in a new way are proposed: chiral purity of amino acids or biopolymers is predicted in solid phase from a previously solid racemic medium. This process may have played a key role in the origin of biochirality. Astrobiology, 7 (2):312-319. Viedma (2007)

 

 

                 ¿Por qué las principales moléculas asociadas a la vida                                    son Homoquirales?

     LA HOMOQUIRALIDAD ES UNA CARACTERISTICA

                      FUNDAMENTAL DE LA VIDA

            

Demostramos experimentalmente cómo entidades quirales de mano izquierda y derecha no pueden coexistir: Un proceso tan simple como el Oswald ripening es suficiente para que solo una mano sobreviva. Basados en estos datos proponemos una explicación del origen de la homoquiralidad.  

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