Influence of Intramineral Proteins on the Growth of Carbonate Crystals Using as a Scaffold Membranes of Ratite Birds and Crocodiles Eggshells.

The lack of information on structural basis where proteins are involved, as well as the biomineralization processes of different systems such as bones, diatom frustules, and eggshells, have intrigued scientists from different fields for decades. This scientific curiosity has led to the use of methodologies that help understand the mechanism involved in the formation of these complex structures. Therefore, this work focuses on the use of eggshell membranes from different species of ratites (emu and ostrich) and reptiles (two species of crocodiles) as a model to differentiate biocalcification and biosilicification by introducing calcium phosphate or silica inside the membrane fiber mantles. We performed this to obtain information about the process of eggshell formation as well as the changes that occur in the membrane during crystal formation. In order to identify and understand the early processes leading to the formation of the microstructures present in the eggshell, we decided to carry out the synthesis of silica-carbonate of calcium, barium, and strontium called biomorph in the presence of intramineral proteins. This was carried out to evaluate the influence of these proteins on the formation of specific structures. We found that the proteins on untreated membranes, present a structural growth similar to those observed in the inner part of the eggshell, while in treated membranes, the structures formed present a high similarity with those observed in the outer and intermediate part of the eggshell. Finally, a topographic and molecular analysis of the biomorphs and membranes was performed by scanning electron microscopy (SEM), Raman and Fourier-transform Infrared (FTIR) spectroscopies.

Biosynthesis of micro- and nanocrystals of Pb (II), Hg (II) and Cd (II) sulfides in four Candida species: a comparative study of in vivo and in vitro approaches.

Nature produces biominerals (biogenic minerals) that are synthesized as complex structures, in terms of their physicochemical properties. These biominerals are composed of minerals and biological macromolecules. They are produced by living organisms and are usually formed through a combination of chemical, biochemical and biophysical processes. Microorganisms like Candida in the presence of heavy metals can biomineralize those metals to form microcrystals (MCs) and nanocrystals (NCs). In this work, MCs and NCs of PbS, HgS or HgCl2 as well as CdS are synthesized both in vitro (gels) and in vivo by four Candida species. Our in vivo results show that, in the presence of Pb2+ , Candida cells are able to replicate and form extracellular PbS MCs, whereas in the presence of Hg2+ and Cd2+ , they did synthesize intercellular MCs from HgS or HgCl2 and CdS NCs respectively. The MCs and NCs biologically obtained in Candida were compared with those PbS, HgS and CdS crystals synthetically obtained in vitro through the gel method (grown either in agarose or in sodium metasilicate hydrogels). This is, to our knowledge, the first time that the biosynthesis of the various MCs and NCs (presented in several species of Candida) has been reported. This biosynthesis is differentially regulated in each of these pathogens, which allows them to adapt and survive in different physiological and environmental habitats.

Coupling of acetylene molecules on ruthenium clusters, involving cleavage of C-Si bonds in the alkyne and coordination of a phenyl ring of a SiPh3 group.

The reaction of [Ru3(CO)12] with the disubstituted acetylene Me3SiC≡CSiMe3 yields several compounds where cleavage of the C-Si bond has occurred thus allowing an easy coupling of carbon fragments to produce allene complexes [Ru4(CO)12(µ4-η(3)-Me3SiCCCSiMe3)] (2), differently substituted metallacycle compounds [Ru3(µ2-CO)2(CO)6{µ3-C(R)C(SiMe3)C(R')C(SiMe3)}] (3) [R = SiMe3, R' = CH3 (3a); R = H, R' = CH3 (3b); R = C≡CSiMe3; R' = H (3c)] and a pentanuclear ruthenium cluster containing three separate alkyne units; two with one SiMe3 substituent and one with two SiMe3 substituents, coordinated to the metal framework [Ru5(CO)12{µ3-(C2SiMe3)2}µ2-C2(SiMe3)2] (4). Another product of the reaction is the acetylide derivative [(µ-H)Ru3(CO)9(CCSiMe3)] (1a). In order to determine if this was an intermediate for the formation of the products already mentioned, the reaction of this compound was carried out with the two terminal alkynes HCCSiMe3 and HCCSiPh3. In the case of the reaction with the SiMe3 derivative, products included the same metallocyclopentadiene derivatives as well as the pentanuclear cluster already mentioned. If the acetylene is the SiPh3 derivative, products show coupling of SiPh3CC units with CCSiMe3 fragments and CO molecules, coordinated to mononuclear [Ru(CO)2(CCSiPh3){η(5)-(CCSiPh3)2C(OH)}] (7), dinuclear [Ru2(CO)3{Ph3Si(H)CC(H)CC(SiMe3)C(O)C(SiPh3)C(H)}] (8) and trinuclear [Ru3(CO)4{(Ph3Si(H)CC(H)CC(SiMe3)}{(H)CC(SiPh3)C(O)}] (9) clusters. One important characteristic in compounds 8 and 9 is that one of the phenyl rings of the SiPh3 substituent is η(6) coordinated to a ruthenium atom. Compounds 2 to 4(a-c) and 7 to 9 were characterized spectroscopically and by X-ray diffraction.