- Granada, Andalucia, Spain
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Coral biomineralization is explored through calcium carbonate precipitation experiments, by counter-diffusion, using highly viscous agarose sol or gel entrapping soluble organic matrices extracted from Balanophyllia europaea and... more
Coral biomineralization is explored through calcium carbonate precipitation experiments, by counter-diffusion, using highly viscous agarose sol or gel entrapping soluble organic matrices extracted from Balanophyllia europaea and Leptopsammia pruvoti species, as well as diffusing Mg2+.
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Neutron macromolecular crystallography (NMC) is the prevailing method for the accurate determination of the positions of H atoms in macromolecules. As neutron sources are becoming more available to general users, finding means to optimize... more
Neutron macromolecular crystallography (NMC) is the prevailing method for the accurate determination of the positions of H atoms in macromolecules. As neutron sources are becoming more available to general users, finding means to optimize the growth of protein crystals to sizes suitable for NMC is extremely important. Historically, much has been learned about growing crystals for X-ray diffraction. However, owing to new-generation synchrotron X-ray facilities and sensitive detectors, protein crystal sizes as small as in the nano-range have become adequate for structure determination, lessening the necessity to grow large crystals. Here, some of the approaches, techniques and considerations for the growth of crystals to significant dimensions that are now relevant to NMC are revisited. These include experimental strategies utilizing solubility diagrams, ripening effects, classical crystallization techniques, microgravity and theoretical considerations.
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ABSTRACT A novel and efficient synthetic method has been developed for the preparation of alkylated aminopurines (N,N-dimethyl-, 2-chloro-N-methyl-, and N-methyladenines) with achiral and chiral 3,4-dihydro-2H-1,5-benzoxathiepin-3-ol by... more
ABSTRACT A novel and efficient synthetic method has been developed for the preparation of alkylated aminopurines (N,N-dimethyl-, 2-chloro-N-methyl-, and N-methyladenines) with achiral and chiral 3,4-dihydro-2H-1,5-benzoxathiepin-3-ol by the Mitsunobu reaction under microwave-assisted conditions. This reaction reveals a complete inversion of the stereogenic centre of the secondary alcohol giving an alkylated purine linked to a homochiral six-membered ring. Fifty novel purine derivatives have been prepared. Alkylation sites have been determined by 2D NMR techniques and for three compounds have been confirmed by X-ray crystallography. The N-9/N-3 regioselectivity can be justified by the electronic effects of the substituents at positions 2 and 6 of the purine.
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ABSTRACT Biomineralization can afford crystal frameworks of great diversity and utmost complexity, frequently featuring hierarchical structures and morphologies beyond any crystallographic restrictions. The formation of such architectures... more
ABSTRACT Biomineralization can afford crystal frameworks of great diversity and utmost complexity, frequently featuring hierarchical structures and morphologies beyond any crystallographic restrictions. The formation of such architectures is usually directed by organic molecules or matrices, which modify crystallization in a deliberate manner. Their influence often leads to sinuous forms, which, by intuition, suggest the presence of life and distinguish these minerals from their inanimate, mostly euhedral counterparts. However, such a strict distinction does not hold. In fact, smooth curvature and higher-order structuring can occur also in purely inorganic environments: simply by precipitating alkaline earth carbonates in silica-containing media, aggregates of highly oriented carbonate nanocrystals can be obtained that display striking noncrystallographic morphologies such as regular helicoids. Thereby, individual crystallites as well as the entire assembly are sheathed by amorphous silica, thus giving a composite material with various levels of hierarchy. These exceptional forms, called “silica biomorphs”, self-assemble through a bottom-up process, which relies on local variations in the conditions and is driven by a pH-based coupling of the carbonate and silicate. Here, we review recent progress in the field of silica biomorphs with particular focus on their mechanism of formation, provide insight into structural details at different length scales, and discuss implications of these biomimetic crystal aggregates for both primitive life detection and materials science.
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... José Luis Arias, Karlheinz Mann, Yves Nys, Juan Manuel Garcia Ruiz, and Maria Soledad Ferna´ndez ... J. 2001, 57, 349357; (d) JL Arias, JP Wiff, V. Fuenzalida, MS Fernandez, in: I. Kobayashi, H. Ozawa (Eds.), Biomineralization:... more
... José Luis Arias, Karlheinz Mann, Yves Nys, Juan Manuel Garcia Ruiz, and Maria Soledad Ferna´ndez ... J. 2001, 57, 349357; (d) JL Arias, JP Wiff, V. Fuenzalida, MS Fernandez, in: I. Kobayashi, H. Ozawa (Eds.), Biomineralization: formation, diversity, evolution and application. ...
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Several mechanisms have been proposed to explain the interactions between proteins and mineral surfaces, among them a combination of electrostatic, stereochemical interactions and molecular recognition between the protein and the crystal... more
Several mechanisms have been proposed to explain the interactions between proteins and mineral surfaces, among them a combination of electrostatic, stereochemical interactions and molecular recognition between the protein and the crystal surface. To identify the mechanisms of interaction in the lysozyme–calcium carbonate model system, the effect of this protein on the precipitation kinetics and morphology of calcite crystals was examined.
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The eggshell is an highly ordered structure deposited in the distal oviduct and composed of calcium carbonate and an organic matrix which is believed to influence its fabric. We have identified ovotransferrin as an 80 kDa matrix protein... more
The eggshell is an highly ordered structure deposited in the distal oviduct and composed of calcium carbonate and an organic matrix which is believed to influence its fabric. We have identified ovotransferrin as an 80 kDa matrix protein observed at high concentration in the uterine fluid at the initial stage of shell mineralization, by N-terminal sequencing and western blotting using monoclonal and polyclonal antibodies. It is present in extracts from demineralized eggshell and was localized by immunofluorescence in the eggshell membranes and mammillae, which are the sites of calcite nucleation. Northern blotting and RT-PCR demonstrated that ovotransferrin message was expressed in the proximal oviduct (magnum and white isthmus), and at a lower magnitude in the distal oviduct (red isthmus and uterus). Ovotransferrin was revealed by immunofluorescence in the tubular gland cells of the uterus. Calcium carbonate crystals grown in vitro in the presence of purified ovotransferrin showed large modifications of the calcite morphology. These observations and its presence in eggshell and membranes suggest a dual role for ovotransferrin, as a protein influencing nucleation and growth of calcite crystals and as a bacteriostatic filter to reinforce its inhibition of Salmonella growth in egg albumen.
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Research Interests: Geology and Geochemistry
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ABSTRACT We have studied the electrostatic interactions of proteins with the calcite surfaces during its subsequent nucleation and growth on a surface. In doing so, a model system of four globular proteins (lysozyme, ribonuclease,... more
ABSTRACT We have studied the electrostatic interactions of proteins with the calcite surfaces during its subsequent nucleation and growth on a surface. In doing so, a model system of four globular proteins (lysozyme, ribonuclease, myoglobin and α-lactalbumin), having the same size and conformation, but differing in surface properties (i.e. surface charge) was used. Depending on the nature of the charge on the protein, its morphological effect on calcite growth (inhibition of specific crystal faces) varies, with this effect becoming more pronounced as the protein is more negatively charged. To study how the adsorption of proteins affects the growth of calcite along different crystal directions, calcite plates cut with different crystallographic orientations (i.e. (001), (104), (100) and (110)) were used as substrates. The overgrowing calcite crystals show the same orientation as the substrate. The nucleation density also varies with the crystallographic orientation of the calcite substrates, increasing in accordance with the sequence: (110), (100) and (001). Finally, to study how the protein itself controls the orientation of crystals, we used amorphous substrates (glass). After incubation on the glass substrates with negatively charged proteins, an oriented nucleation of the calcite crystals was induced.
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Desde el punto de vista morfológico, los cristales de la Cueva de los Cristales puede dividirse en dos grupos visualmente muy diferentes. Las paredes de la cueva y en particular el suelo están cubiertos de cristales equantes con forma de... more
Desde el punto de vista morfológico, los cristales de la Cueva de los Cristales puede dividirse en dos grupos visualmente muy diferentes. Las paredes de la cueva y en particular el suelo están cubiertos de cristales equantes con forma de bloque casi equidimensional ...
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Dispositivo para el crecimiento de cristales en contradifusión (ver figura en archivo de texto adjunto). El dispositivo ha sido concebido para llevar a cabo procesos de cristalización macromolecular en los cuales la transferencia de... more
Dispositivo para el crecimiento de cristales en contradifusión (ver figura en archivo de texto adjunto). El dispositivo ha sido concebido para llevar a cabo procesos de cristalización macromolecular en los cuales la transferencia de materia se controla por difusión. La ...