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Phenotype can express different morphologies in response to biotic or abiotic environmental influences. Mollusks are particularly sensitive to different environmental parameters, showing shell morphology variation with several environmental factors. Here, we investigate shell morphology of the commercially important clam Chamelea gallina in relation to natural variations in sea surface temperature (SST) and solar radiation (SR). Specimens of C. gallina were sampled using hydraulic dredges on soft bottoms in the subtidal zone at 3-7 m depth, in six populations along a latitudinal gradient (~400 km) in the Western Adriatic Sea. Only clams of commercial size (25-30 mm) were used in this study. To analyze shell morphology, length, width, height, thickness of the valve and dry shell mass were measured. Volume and shell density parameters were obtained by means of the buoyant weight technique and used to calculate skeletal properties (micro-density, bulk-density and apparent porosity). Compression tests were conducted to check for shell resistance to fracture. Furthermore, to obtain qualitative information about shell mineral composition, X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were performed. C. gallina shells from the warmest and the most irradiated population were about 30% lighter, thinner and more porous. They also showed a reduction in shell stiffness and load to fracture, with an increase in fragility and damage susceptibility. However, no variation was observed in shell polymorphism (100% aragonite), indicating no effects of environmental parameters on the composition of biomineralized shell. Because of the importance of this species as a commercial resource in the Adriatic Sea, the variation of mass and fragility in C. gallina shells with increasing SST and SR could have economic implications along Adriatic coastline. Less resistance to breakage shells could be more damages during the catch with hydraulic dredges, with a bigger amount of clams discarded from the trade and a bigger catch effort for fishermen with a loss in economic yield.

Rietveld method has been applied to refine the structure of magnesium substituted β-tricalcium phosphate at a magnesium content of about 14 mol%. The results of the refinements, which show a final agreement factor Rwp = 0.12, are in agreement with an almost complete substitution in two of the five crystallo-graphically independent cation sites. The preference of magnesium for these two sites can be explained on the basis of the coordination geometry of the five different cation sites. Furthermore the results allow to interpret the discontinuity found around 10 magnesium mol% in the variation of the c axis as a function of magnesium content.

Structure analysis of human ubiquitin metal-ion adducts

A physical hydrogel prepared with the low-molecular-weight hydrogelator (LMWHG) CH2(C3H6CO-L-Phe-D-Oxd-OH)2 and water/ethanol mixture was applied as a potential “Trojan Horse” carrier into cells. By SEM and XRD analysis we could demonstrate that a fibrous structure is present in the xerogel, making a complex network. The gelator is derived from α-amino acids (Thr, Phe) and a fatty acid (azelaic acid) and is biocompatible: it was dosed to IGROV-1 cells, which internalized it, without significantly affecting the cell proliferation. To check the internalization process by confocal microscopy, fluorescent hydrogels were prepared, introducing the fluorescent dansyl moiety into the mixture.

Calcium phosphate biogenic materials are biocompatible and promote bioactivity and osteoconductivity, which implies their natural affinity and tendency to bond directly to bones subsequently replacing the host bone after implantation owing to its biodegradability. Calcium hydrogen phosphate dihydrate, CaHPO4·2H2O, is known to be a nucleation precursor, in aqueous solutions, for apatitic calcium phosphates and, hence, a potential starting material for bone substitutes. Numerous approaches, via hydrothermal and ambient synthetic routes, have been used to produce calcium phosphate from biogenic calcium carbonate, taking advantage of the peculiar architecture and composition of the latter. In this article, the lamellar region of the cuttlefish bone (Sepia officinalis) was used as a framework for the organized deposition of calcium phosphate crystals, at ambient conditions via a fast procedure involving an amorphous calcium carbonate intermediate, and ending with a conversion to calcium phosphate and a fixation procedure, thereby resulting in direct conversion of biogenic calcium carbonate into calcium phosphates at ambient conditions from the scale of months to hours.

The metal-binding ability of human ubiquitin (hUb) towards a selection of biologically relevant metal ions and complexes has been probed. Different techniques have been used to obtain crystals suitable for crystallographic analysis. In the first type of experiments, crystals of hUb have been soaked in solutions containing copper(II) acetate and two metallodrugs, Zeise salt (K[PtCl(3)(η(2)-C(2)H(4))]·H(2)O) and cisplatin (cis-[PtCl(2)(NH(3))(2)]). The Zeise salt is used in a test for hepatitis, whereas cisplatin is one of the most powerful anticancer drugs in clinical use. The Zeise salt readily reacts with hUb crystals to afford an adduct with three platinum residues per protein molecule, Pt(3)-hUb. In contrast, copper(II) acetate and cisplatin were found to be unreactive for contact times up to one hour and to cause degradation of the hUb crystals for longer times. In the second type of experiments, hUb was cocrystallized with a solution of copper(II) or zinc(II) acetate or cisplatin. Zinc(II) acetate gives, at low metal-to-protein molar ratios (8:1), crystals containing one metal ion per three molecules of protein, Zn-hUb(3) (already reported in previous work), whereas at high metal-to-protein ratios (70:1) gives crystals containing three Zn(II) ions per protein molecule, Zn(3)-hUb. In contrast, once again, copper(II) acetate and cisplatin, even at low metal-to-protein ratios, do not give crystalline material. In the soaking experiment, the Zeise anion leads to simultaneous platination of His68, Met1, and Lys6. Present and previous results of cocrystallization experiments performed with Zn(II) and other Group 12 metal ions allow a comprehensive understanding of the metal-ion binding properties of hUb with His68 as the main anchoring site, followed by Met1 and carboxylic groups of Glu16, Glu18, Glu64, Asp21, and Asp32, to be reached. In the case of platinum, Lys6 can also be a binding site. The amount of bound metal ion, with respect to that of the protein, appears to be a relevant parameter influencing crystal packing.

A series of oligomers of the type Boc-(L-Phe-D-Oxd)(n)-OBn (Boc = tert-butoxycarbonyl; Oxd = 4-methyl-5-carboxy oxazolidin-2-one; Bn = benzyl) were prepared for n = 2-5. The shortest oligomer, Boc-(L-Phe-D-Oxd)(2)-OBn, aggregates and forms a fiber-like material with an anti-parallel beta-sheet structure in which the oligopeptide units are connected to each other by only one intermolecular hydrogen bond. The longer oligomers exhibit structural heterogeneity. They start to organize into secondary structures by the formation of intramolecular hydrogen bonds at the pentamer level. Microscopy and diffraction of the oligomers indicated a crystalline character for only the shorter ones.E’ stata sintetizzata la serie di oligomeri Boc-(L-Phe-D-Oxd)

Rhodium on graphite (Rh/Gr, C(24)Rh) was prepared by reaction of anhydrous rhodium trichloride with potassium graphite (C(8)K, 3 equivalents) and used as a heterogeneous catalyst for the hydrogenation of carbocyclic and heterocyclic aromatic compounds at room temperature and 1 atm of hydrogen pressure. The effect of substitution on the benzene ring was examined in a variety of derivatives, including those with alkyl, hydroxy, alkoxy, aryloxy, carboxy, amino, nitro, acyl, chloro, or functionalized alkyl groups. Reduction of carbonyl functions of aromatic aldehydes and ketones occurred with complete or partial cleavage of the benzylic C-O bond; this cleavage also occurred in the hydrogenation of benzylic alcohols and esters.

Poly-L-glutamic (pGlu) and poly-L-aspartic (pAsp) acids, as analogues of naturally occurring soluble acidic proteins, were used to investigate specific interactions between the acidic polypeptides and calcite as a mineral surface. A basic polypeptide (poly-L-lysine, pLys) served as a negative control for testing the role of conformity between the substrate and the adsorbed polypeptides in biomineralization processes. The kinetics of calcite crystal growth was determined in a simplified precipitation model system by inoculating well defined calcite seed crystals into a moderately supersaturated solution containing one of the polypeptides. From the kinetic data, the mode and extent of the calcite/polypeptide interactions were determined. The parabolic rate law was found to be valid for the calcite crystal growth, the integration of ions into the spiral steps at the calcite crystal surface being the rate-determining mechanism. Small amounts of pGlu or pAsp caused an inhibition of calcite crystal growth, the effect being pAsp > pGlu, and the exponential dependence of the growth rate on supersaturation confirmed that surface nucleation was the growth controlling mechanism in the presence of the two acidic polypeptides. The pLys non-selective, weak, electrostatic adsorption at the crystal surface was probably responsible for increasing the calcite growth rate at low concentrations and for inhibiting it at higher concentrations. The strongest interactions between the crystal surfaces and the polypeptides were observed for the calcite/pAsp systems. They could be accounted for by coordinative interactions between the side chain carboxylic groups of the predominantly planar arrangement of the pAsp structure (β -pleated sheet) and Ca2+ ions from the calcite surface.

The dipeptide Boc-L-Phe-D-Oxd-OBn spontaneously forms fibers consisting of parallel infinite linear chains arising from single intermolecular N-H…O=C hydrogen bonds, as demonstrated by IR spectroscopy, X-ray diffraction, and solid-state NMR. SEM observations show that the thickness and the width of the filamentous material are almost constant. This is the absolute borderline case of a parallel beta-sheet structure.

Since the 1991 discovery of hollow cylindrical carbon-based unidimensional structures, the nanotubular form of matter has been thoroughly investigated leading to a wealth of literature. Their particular features are not limited to graphite but are common in many inorganic highly anisotropic two-dimensional layered compounds. The first non-mineral inorganic nanotubes, constituted of lamellar molybdenum and tungsten disulfides, were synthesized in 1992. Afterwards, a large number of inorganic nanotubes have been synthesized, opening the path to the development of nanoelectronics, due to their dielectric properties. The unique mineral phase that crystallizes with a tubular morphology is chrysotile, which has been tentatively used to prepare ultra-thin wires by filling its hollow nanodimensional core with a conductive material. To overcome its natural heterogeneity in composition, morphology, and structure, synthetic chrysotile-inspired nanotubes have been recently synthesized. These geoinspired nanotubes can be prepared with specific properties, finalized to focused achievements such as preparation of new quantum wires. The existing knowledge on the structural and physicochemical properties of mineral and synthetic chrysotile nanotubes is reviewed, with the aim of emphasizing their potential applications as nonlinear optical and conducting technological devices. Bibliography encompasses over one hundred references.

CryoTEM demonstrates that a CNA35-bearing liposomal MRI contrast agent selectively binds to poorly assembled collagen type I as opposed to well-assembled collagen fibrils, whereas monomeric CNA35 binds to all forms of collagen. It is shown that upon conjugation to liposomes and micelles CNA35 loses its ability to dissociate ordered collagen fibrils and thereby to create its own binding sites.

Integrating carbon nanoparticles (CNPs) with proteins to form hybrid functional assemblies is an innovative research area with great promise for medical, nanotechnology, and materials science. The comprehension of CNP–protein interactions requires the still-missing identification and characterization of the ‘binding pocket’ for the CNPs. Here, using Lysozyme and C60 as model systems and NMR chemical shift perturbation analysis, a protein–CNP binding pocket is identified unambiguously in solution and the effect of the binding, at the level of the single amino acid, is characterized by a variety of experimental and computational approaches. Lysozyme forms a stoichiometric 1:1 adduct with C60 that is dispersed monomolecularly in water. Lysozyme maintains its tridimensional structure upon interaction with C60 and only a few identified residues are perturbed. The C60 recognition is highly specific and localized in a well-defined pocket.

The crystallization of skeletal aragonite by corals takes place in sites whose physical characteristics resemble those of a highly viscous sol or a gel. In these sites, biomolecules are secreted by calicoblast cells of the coral and some of them become entrapped in the skeleton. To explore the biomineralization process, a series of calcium carbonate crystallization experiments were carried out in a counter-diffusion system (CDS) containing a viscous agarose sol with two dissolved intra-skeletal soluble organic matrices (SOM) that were extracted from Balanophyllia europaea, a zooxanthellate coral, and Leptopsammia pruvoti, an azooxanthellate species. The influence of the viscosity of the media and the presence of Mg2+ were investigated in two additional sets of experiments, one using an agarose gel of variable viscosity, and another allowing Mg2+ to diffuse from the cationic reservoir. The main findings are the following: (i) the species-specific molecular composition of the two SOMs has a different impact on the crystallization parameters and morphology of calcium carbonate; (ii) the viscosity of the gelling media, and thus its porosity, is important in regulating the SOM action; (iii) Mg2+ is important in defining specific and sharp limits of supersaturation under which crystallization occurs; (iv) the polymorph distribution is determined by SOM concentration. Thus, through the use of the CDS, it was possible to first study in vitro the biomineralization of zooxanthellate and azooxanthellate corals.

A growing number of classes of organic (macro)molecular materials have been trapped into inorganic crystalline hosts, such as calcite single crystals, without significantly disrupting their crystalline lattices. Inclusion of an organic phase plays a key role in enhancing the mechanical properties of the crystals, which are believed to share structural features with biogenic minerals. Here we report the synthesis and mechanical characterization of composite calcite/SWCNT-COOH single crystals. Once entrapped into the crystals SWCNT-COOH appeared both as aggregates of entangled bundles and nanoropes. Their observation was possible only after crystal etching, fracture or FIB (focused ion beam) cross-sectioning. SWCNT-COOHs occupied a small volume fraction and were randomly distributed into the host crystal. They did not strongly affect the crystal morphology. However, although the Young's modulus of composite calcite/SWCNT-COOH single crystals was similar to that of pure calcite their hardness increased by about 20%. Thus, SWCNT-COOHs provide an obstacle against the dislocation-mediated propagation of plastic deformation in the crystalline slip systems, in analogy with the well-known hardness increase in fiber-reinforced composites. © The Royal Society of Chemistry 2013.

Many mineralization processes occur in convection-free conditions. Understanding these processes requires knowledge of crystal nucleation and growth processes in gels or high viscous sol systems. In this work, the crystallization parameters of calcium carbonate in an agarose viscous sol using counterdiffusion crystallization were monitored as a function of time. Additionally, by comparing the precipitation parameters in the high viscous sol entrapping charged polypeptides, namely, poly-l-lysine (pLys), poly-l-aspartate (pAsp), and poly-l-glutamate (pGlu), it was possible to establish the polypeptide capability to inhibit, or eventually promote, the calcium carbonate nucleation and/or crystal growth processes. The polymorphism and morphology of the precipitates indicate that pLys only influences the growth mechanism of calcium carbonate without affecting the nucleation process. On the contrary, pAsp and, to a minor extent, pGlu affect both nucleation and growth. The application of this analysis can be extended to other additives and macromolecules able to affect crystallization processes.

Mineralized tissues grow through biologically controlled processes in which specific macromolecules are involved. Some of these molecules, which are present in very low concentrations and are difficult to localize and characterize, become entrapped inside the mineralized tissue. Herein, a protein fragment, GP, which was obtained by the alkaline digestion of the green sheet of the abalone shell, is used as a probe to study the changes in molecular structure that occur during the precipitation of calcium carbonate. This important goal was achieved by exploiting a fluorescent tag in GP. The experimental results that were obtained by using spectroscopic-, chromatographic-, and microscopic techniques indicate that GP controls the precipitation kinetics and morphology of calcium carbonate crystals, and that it only undergoes structural reorganization when entrapped inside calcium carbonate crystals. To the best of our knowledge, this report represents one of the first studies on the conformational changes of a protein fragment that is involved in biomineralization processes on moving from the solution phase into the mineral phase.

Acid catalysts were prepared by sulfonation of carbon materials obtained from the pyrolysis of sugar beet molasses, a cheap, viscous byproduct in the processing of sugar beets into sugar. Conditions for the pyrolysis of molasses (temperature and time) influenced catalyst performance; the best combination came from pyrolysis at low temperature (420 °C) for a relatively long time (8-15 h), which ensured better stability of the final material. The most effective molasses catalyst was highly active in the esterification of fatty acids with methanol (100 % yield after 3 h) and more active than common solid acidic catalysts in the transesterification of vegetable oils with 25-75 wt % of acid content (55-96 % yield after 8 h). A tandem process using a solid acid molasses catalyst and potassium hydroxide in methanol was developed to de-acidificate and transesterificate algal oils from Chlamydomonas reinhardtii, Nannochloropsis gaditana, and Phaeodactylum tricornutum, which contain high amounts of free fatty acids. The amount of catalyst required for the de-acidification step was influenced by the chemical composition of the algal oil, thus operational conditions were determined not only in relation to free fatty acids content in the oil, but according to the composition of the lipid extract of each algal species.

The formation of cyclic dipeptides (DKPs, 2,5-diketopiperazines) from dipeptides having proline (Pro) as the fixed N-terminal amino acid was investigated by analytical pyrolysis with a heated platinum filament coil. Glutamic acid (Glu), aspartic acid (Asp), glutamine (Gin), lysine (Lys) or arginine (Arg) was the terminal amino acid. Products evolved from off-line pyrolysis at 500 degrees C were analysed by GC-MS as such or after trimethylsilylation. The structure of a novel DKP from the pyrolysis of Pro-Glu, namely hexahydrodipyrrolo[1,2-a:1',2'-d]pyrazine-3,5,10(10aH)-trione, was established by ESI-MS/MS and extensive NMR analysis. This DKP could be identified in the pyrolysates of dipeptide Pro-Gln, tripeptide Pro-Glu-Leu, collagen and bovine serum albumin (BSA). Pyrolysis of Pro-Lys and Lys-Pro-Leu afforded the cyclo(Pro-Lys) tentatively identified by interpretation of its trimethylsilyl (TMS) derivative mass spectra and the DKPs resulting from the deamination of the lateral chain. The dipeptide Pro-Asp yielded isomeric cyclo(Pro-Asp) revealed as TMS derivatives and cyclo( Pro-Ala) from the decarboxylation of the side chain. Analytical pyrolysis of the above peptides as well as of Pro-Tyr, collagen and BSA enabled the compilation of GC (retention times relative to an internal standard) and MS data (characteristic ions) of over eighty DKPs including their TMS derivatives, the latter ones useful in the identification of thermal degradation products of proteinaceous materials in several matrices. (C) 2012 Elsevier B.V. All rights reserved.

Human bones and teeth are frequently recovered at archaeological sites. Their state of preservation may depend on the mode and the burial environment. The content of collagen and the degree of crystallinity of carbonate hydroxyapatite (HA) are among the indicators adopted to evaluate the conservation status of bones. Analytical pyrolysis (Py) [1] together with X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), were used at this scope. In this work, a new quantitative procedure in Py was employed to characterise residual proteins in five bone samples from the medieval necropolis of Vicenne-Campochiaro (Molise, Italy)[2]. The yields of cyclic dipeptides (2,5-diketopiperazines, DKPs) evolved form the pyrolysis of the samples, including the cyclo(proline-hydoxyproline) as distinctive marker of collagen, were determined by GC-MS with and without silylation. The detection of DKPs enabled the identification of collagen in all the analysed samples, in accordance to the FTIR spectra showing the characteristic amide peak. The presence of organic matter along with that of carbonatic phases was confirmed and estimated by TGA. XRD data showed that the samples mainly contained HA having different degrees of crystallinity; small amounts of quartz and calcite were also detected in some samples. The quantitative experimental data were combined to provide a relative estimate of the degree of conservation of the bone samples. The bones of an adult young female (t.139) and an aged male (t.165) resulted to be the worst and best preserved, respectively. The tombs were located in the same area where the acidity of the soil has damaged nearly all the skeletons. The skeleton from t.165 was almost complete, whereas the one from t.139 was lacking in many bones. Therefore biological (age-at-death, sex) and ritual (care, depth) factors as well as specific conditions of each burial could be involved in the observed different preservation state.

In protein crystallization trials there is always some ambiguity in defining if the nucleation event occurred by a homogeneous or a heterogeneous process. One of the reasons comes from the difficulty to compare experiments with or without a heterogeneous nucleant under the same chemical conditions. The outcome is that it is difficult to figure out the values of supersaturation addressing homo- versus heterogeneous nucleation. Recently it has been shown that the crystallization mushroom allows performance of sitting drop vapor diffusion experiments under identical physical-chemical conditions and that functionalized surfaces are favorable heterogeneous substrates for protein crystallization. With the aim to discriminate between nucleation processes, three model proteins, lysozyme, glucose isomerase, and thaumatin, have been crystallized at different starting concentrations, using positively and negatively charged surfaces, in the crystallization mushroom. The results show that (i) the heterogenenous nucleation does not crucially affect the nucleation process under conditions of high supersaturation and that (ii) the nucleating action of the fianctionalized surfaces is mainly related to their superficial charge distribution more than to their absolute charge, according to both classical and colloidal nucleation theories.

Biomineralization processes are the subject of numerous investigations. This article gives a review of the study on interactions between the charged polypeptides and the mineral surfaces involved in biomineralization, with an additional kinetic approach. The influence of polypeptides on two types of precipitation processes is discussed: the spontaneous precipitation from supersaturated solution and the growth kinetics of calcite seed crystals. In the first case the phenomenon of the formation and stabilization of metastable phases was found while in the second case the influence of the applied polypeptides on the kinetics and mechanisms of calcite crystal growth was investigated. Calcium carbonate polymorphs, calcite and vaterite, were used as biomineral substrates and acidic polypeptides, poly-L-aspartic (pAsp) acid and poly-L-glutamic (pGlu) acid, as simplified models of naturally occurring soluble acidic proteins. A basic polypeptide, poly-L-lysine (pLys), was also used in experiments in order to find out whether conformity between the crystal surface and the adsorbed polypeptide, or just the electrostatic interactions, have a decisive role in these processes. The addition of a particular polypeptide into the precipitation system caused a significant inhibition of nucleation and growth of vaterite, the extent of inhibition being in the order InhpAsp > InhpGlu >> InhpLys. In addition to the inhibition of precipitation, the change of the polymorphic composition and the crystal morphology of the precipitate were also achieved. The explanation of such acidic polypeptide behaviour is a consequence of kinetic constraints through the diverse efficiency of inhibition of both calcite nucleation and vaterite growth caused by adsorption of acidic polypeptides. The acidic polypeptides also caused the inhibition of calcite crystal growth, the effect being pAsp > pGlu, and changed the observed mechanism of growth controlled by the integration of ions into the spiral steps, as found for the model systems, to the surface nucleation rate-determining mechanism. Nonselective, weak and electrostatic adsorption of pLys at the crystal surface was probably responsible for increasing the calcite crystal growth rate when pLys was present at low concentrations and for inhibiting it at pLys higher concentrations. The strongest interactions between the crystal surfaces and the polypeptides, observed for the calcite/pAsp system, can account for coordinative interactions between the side chain carboxylic groups of the predominantly planar arrangement of the pAsp structure (β-pleated sheet) and Ca2+ ions from the crystal surface. (doi: 10.5562/cca1809)

A small library of stereoisomeric pseudopeptides able to make gels in different solvents has been prepared and their attitude to make gels in the presence of several metal ions was evaluated. Four benzyl esters and four carboxylic acids, all containing a moiety of azelaic acid (a long chain dicarboxylic acid) coupled with four different pseudopeptide moieties sharing the same skeleton (a phenyl group one atom apart from the oxazolidin-2-one carboxylic group), were synthesized in solution, by standard coupling reaction. The tendency of these pseudopeptides to form gels was evaluated by using the inversion test of 10 mM solutions of pure compounds and of stechiometric mixtures of pseudopeptides and metal ions. To obtain additional information on the molecular association, the gel samples were left to dry in the air to form xerogels that were further analyzed using SEM and XRD. The formation of gel containing Zn(II) or Cu(II) ions gave good results in term of incorporation of the metal ions, while the presence of Cu(I), Al(III) and Mg(II) gave less satisfactory results. This outcome is a first insight in the formation of stable LMWGs formed by stechiometric mixtures of pseudopeptides and metal ions. Further studies will be carried out to develop similar compounds of pharmacological interest.

Some compounds containing the L-Phe-D-Oxd [L-Phe = L-phenylalanine; D-Oxd = (4R,5S)-4-carboxy-5-methyl oxazolidin-2-one] moiety have been prepared and their properties as supramolecular material have been checked. Some derivatives of the dipeptide L-Phe-L-Phe (that usually forms nanotubes) and some long chain derivatives that behave as low molecular weight gelators (LMWG) have been prepared. Simultaneously we have built the same structures replacing the D-Oxd moiety with a D-Pro (D-Pro = D-proline) moiety, to check if the presence of the Oxd moiety is essential for the existence of those materials: in contrast with the D-Oxd containing compounds, no material is ever formed with all the D-Pro containing molecules. This outcome suggests that the L-Phe-D-Oxd moiety may be defined as a “privileged scaffold” for the formation of supramolecular materials and can be introduced in more complex structures to induce some selected properties in the solid state.

The interstitial green sheets in abalone shell nacre are shown to be bifacially differentiated trilaminate polymeric complexes, with glycoprotein layers sandwiching a central core containing chitin. They share some common feature with the organic matrix layers between the aragonite tablets in the nacre and the periostracum, and show similarities to the myostracum. Thus, although the green sheet is reported to be unique to the abalone shell, it represents an interesting model for the study of molluscan shell biomineralization processes. Indeed, during shell formation, prismatic and spherulitic aragonite precedes and follows the deposition of the interstitial green polymeric composite sheets, and there is evidence to suggest that these sheets demark the interruption of nacre synthesis and serve to nucleate the resumption of calcium carbonate crystal growth. The green polymeric interstitial sheet purified from the abalone shell was investigated by spectroscopic and imaging techniques: FTIR, confocal microscopy, scanning and transmission electron microscopy, and by pyrolysis combined with GC–MS. Structural and compositional differences are observed between the surfaces of the two sides of the interstitial polymeric composite sheets. Moreover, comparative crystallization experiments on the green sheet sides also reveal asymmetry with respect to the nucleation of calcium carbonate. These findings suggest that these bifacially differentiated interstitial composites may play an active role in the mineral assembly processes, with one of the surfaces acting as a crystal nucleator.

Hybrid microspheres of calcium carbonate/fullerenol were synthesized and characterized. Their morphology depends on the concentration of the fullerenol solutions. XRD and FT-IR measurements proved that the mineral phase is consistently calcite, while fluorescence confocal microscopy indicated that fullerenol is homogenously included in the crystalline matrix.

Precipitation of calcium carbonate in different carrageenan gelling environments was initiated by fast mixing of calcium chloride and sodium carbonate solutions. Carrageenan concentration and the gelling mechanism, controlled by the addition of different cross-linking cations, calcium or sodium, were varied in order to elucidate the mechanism and dynamic of solid phase formation in highly supersaturated precipitation systems in which initial formation of three calcium carbonate polymorphs and amorphous calcium carbonate is possible. The analysis of the samples isolated 5 days after initiating the precipitation showed that calcite was the only solid phase obtained in the whole range of carrageenan concentrations investigated. At lower carrageenan concentrations, the calcite aggregates were observed, while at higher concentrations rhombohedral crystals of uniform size distribution were found. Spherical imprints on the surfaces of calcite particles precipitated at lower gel concentrations were observed, thus pointing out the initial and simultaneous precipitation of stable calcite and metastable calcium carbonate phases, vaterite and possibly amorphous calcium carbonate. Time resolving precipitation experiments within gelling media of low concentration confirmed such an assumption and implied the solution mediated mechanism of transformation of metastable vaterite, which was in close contact with calcite crystals. Reference precipitation systems, performed at apparently similar initial supersaturation and hydrodynamic conditions but without the presence of carrageenan, showed a comparable pattern of stepwise solution mediated transformation of metastable amorphous calcium carbonate and vaterite into calcite

The synthesis of the small pseudopeptide Boc-L-Phe-D-Imz-OBn (Imz = imidazolidin-2-one-4-carboxylate) is reported. Crystallization of this peptide from methanol, ethanol, and isopropanol leads to isostructural solvates when the solvent is methanol or ethanol with a peptide/solvent ratio of 2:1 and to an unsolvated polymorph in the case of isopropanol. The solvate peptide crystallizes forming infinite chains with the monomers in parallel orientation connected by a single hydrogen bond. The chains are arranged in antiparallel direction and cross-linked through the NH group of the imidazolidin heterocycle with formation of a stable 2D network. Crystals from isopropanol form a different 2D network. The degree of order in the crystal assembly decreases from methanol and ethanol solvates to the unsolvated pseudopeptide grown from isopropanol. Quantum chemical calculations at the HF/6-31G* level of ab initio MO theory, carried out on the two different packings, show a slight preference for the unsolvated packing.

Rhodium-graphite is easily prepared by reaction of anhydrous rhodium trichloride with 3 equivalemts of potassium graphite (C8K) and is active as an active heterogeneous hydrogenation catalyst for the hydrogenation of carbocyclic and heterocyclic aromatic compounds in hydrocarbon or alcoholic solvents at room temperature and 1 atm of hydrogen pressure.

The two epimers Boc-l-Phe-d-Oxd-(S)-β3-hPhg-OBn (1) and Boc-l-Phe-d-Oxd-(R)-β3-hPhg-OBn (2) have been prepared by standard methods in solution, and their conformation was analyzed both in solution ...

The effectiveness of some seawater components, such as magnesium, potassium, sodium, sulfate and chloride ions, and humic acid, in the control of calcium carbonate composition, morphology, and phase distribution was studied. These components were tested singularly, in pairs, and all together. It was observed that magnesium ions phase distribution control is influenced by the presence of other ions and that in the presence of a high content of magnesium ions monohydrocalcite precipitates. Moreover, in the presence of magnesium or potassium ions the calcite crystals show modified rhomohedral morphologies, while the presence of sulfate ions favors their aggregation. Humic acids have an inhibition effect on calcium carbonate precipitation, induce the formation of empty spheres of vaterite, and modify the calcium carbonate phase distribution. The isomorphic substitution of magnesium to calcium in the calcite structure is favored by some seawater ions and enhanced by the presence of humic acids.

Mathematical morphology is a tool for extracting image components that are useful for representation and description. The technique consists of a set-theoretic method of image analysis providing a quantitative description of geometrical structures. A simple application of mathematical morphology to a bi-dimensional processing of TEM images of airborne particles allows us to distinguish between particles grown and/or transported in atmosphere under dry conditions or in rainy days by a simple comparison of the corresponding image form factors. The form factors range in the 0.385–0.031 interval in the case of particles sampled in rainy days, and in the 0.103–0.006 interval in the case of non-rainy conditions. The same classification criterion was applied to filters collected under dry conditions and plunged in water. The results demonstrate that a morphological change may be artificially induced to the particle structure. The artificially wet particles, indeed, display an apparent contraction of their structures evidenced by a two-fold increase of the average values of their form factors. The last experiment roughly simulates the impact of particles on membranes of the respiratory tract.

Comb-like polymers have an important application in cement industries, where they are referred to as polymeric admixtures/superplasticizers. They are used to increase the workability of fresh cementitious mixtures as well as to improve the strength and durability of the hardened state. So far, the interaction of polymer/Portland-limestone cement particles has been poorly investigated. This paper describes the overgrowth of calcite on Portland-limestone cement particles, a mixture of ground clinker and calcite, in the presence of comb-like polymers. The morphological and aggregational variation of overgrown calcite crystals is used as a model to evaluate the interaction occurring between cement particles and polymeric admixtures. Rhombohedral, spherulitic, microtrumpet, or fibrous calcite crystals were observed as a function of the kind of cement particles and comb-like polymers used. These results suggest that comb-like polymers may assume diverse conformations when associated with the different particles that constitute Portland-limestone cement.

The chemical conjugation of bisphosphonates (BPs), specifically alendronate, to hydroxyapatite could be an effective means to impart to it fine-tuned bioactivity. Horse heart myoglobin (Mb), a well-characterized protein, has been adsorbed onto biomimetic hydroxyapatite nanocrystals (nHA) and onto the nHA/alendronate conjugate powdered samples. The obtained materials have potential use in bone implantation and as prospective drug-delivery devices. The kinetic absorption of Mb onto nHA is dramatically affected by its functionalization with alendronate. The covering of the nHA surface by alendronate inhibits the adsorption of myoglobin. The adsorption mechanisms of the protein were studied by spectroscopic techniques (UV−vis and surface-enhanced Raman spectroscopy). The results indicate that the protein changes conformation upon adsorption on the inorganic substrate. In particular, the interaction with nHA alters the coordination state of the iron in the heme through the formation of a hexacoordinated low-spin Mb heme, possibly involving the distal histidine. Instead, the covering of the nHA surface by alendronate does not adsorb the protein but preserves the coordination state of the heme moiety. This study could be of significance either in the field of biomaterials science, in particular, to fine tune a bone-specific drug delivery device and to test nHA as a new support for heterogeneous catalysis, improving the understating of enzyme immobilization.

Ribosome inactivating proteins (RIPs) are toxins, which depurinate major RNA inhibiting protein synthesis1. The cleaved N-glycosidic bond corresponds to a specific adenine located in the sarcin/ricin loop, highly conserved in rRNAs from different species and essential for interaction with elongation factors. RIPs depurinate other polynucleotides as RNAs from different sources, DNA, poly(A), and even poly(ADP-ribosyl)ated proteins2. This action may lead to cell death by apoptosis or necrosis depending upon the level of damage. The three-dimensional structure of three type 1 RIPs, dianthin 303, bouganin and lychnin4, has been solved in the crystallographic research unit of Bologna. Their adenine polynucleotide glycosylase activity was also determined together with other known RIPs: PAP-R, momordin I, ricin A chain and saporin-S6. Saporin-S6 releases the highest number of adenine molecules from rat ribosomes, and poly(A), while its efficiency is similar to dianthin 30, bouganin and PAP-R on herring sperm DNA. Measurements of the protein synthesis inhibitory activity confirmed that saporin-S6 is the most active. The overall structure of the three studied proteins is similar to the other considered RIPs and the typical RIP fold is conserved. The superimposition of the Ca atoms highlights some differences in the N-terminal and C-terminal domains. Detailed structural and potential electrostatic analyses indicates that the efficiency of saporin-S6 on various polynucleotides may be ascribed to a negative electrostatic surface potential at the active site and several exposed positively charged residues in the region around that site. These two conditions, not present at the same time in others examined RIPs, may guarantee to saporin-S6 an efficient interaction with the substrates, characterized by a negatively charged backbone, and an efficient catalysis. 1. Endo Y, Tsurugi K (1987). J. Biol. Chem., 262:8128-8130. 2. Barbieri L, Brigotti M, Perocco P, Carnicelli D, Ciani M, Mercatali L, Stirpe F (2003). FEBS Lett., 538:178-182. 3. Fermani S, Falini G, Ripamonti A, Polito L, Stirpe F, Bolognesi A. (2005) J Struct Biol., 149:204-212. 4. Fermani S, Tosi G, Farini V, Polito L, Falini G, Ripamonti A, Roveri N, Barbieri L, Chambery A., Bolognesi A (2008) Proteins: Struct. Func. Bioinf., submitted.

The influence of different water-soluble polysaccharides, dextrans (cationic, anionic and non-ionic) and soluble starch, on the precipitation of calcium carbonate, has been investigated in the model system in which calcium hydroxide and carbonic acid were reactants. In the absence of additives, the formation of metastable phases, vaterite and amorphous calcium carbonate is observed at the early stage of the process, and as a consequence of the solution-mediated transformation process calcite appears in the system as the only solid phase in equilibrium. In the presence of starch, vaterite is found in the final precipitate, with the content increasing with the increase of starch concentration, probably as a consequence of calcite nucleation and crystal growth inhibition. Non-ionic dextran causes the inhibition of vaterite nucleation, which results in the formation of calcite as a predominant solid phase throughout the precipitation process. The crystal size of the so-formed calcite reduces by increasing the relative molecular mass ( M r ) of neutral dextran. The presence of charged dextrans, either cationic or anionic, causes inhibition of the overall precipitation process: in the case of anionic dextran the inhibition seems to be the consequence of its reaction with Ca 2+ ions (supersaturation decrease), while cationic dextran most probably adsorbs electrostatically onto the negatively charged surfaces of calcite and vaterite.

Alkaline and alkaline earth cations have been used in the synthesis of SBA-3, a silica mesoporous materials. These cations can not substitute silicon in the silica structure. However, we found that...

Helical domain collagen substrates had been mineralized using simulated body fluid. They had an increasing level of structural organization; being in the form of gel, film, and uniaxial deformed film. The experiments were carried out for different periods of time and the obtained composite materials were characterized in their mineral content. Apatite precipitation was detected. The results show that the helical domain collagen substrates partially inhibit the in vitro apatite precipitation processes, but the amount and the crystallinity of deposited mineral can be controlled by the different assemblies of the helical domain collagen fibers.

With the aim of obtaining new molecules that could form nanomaterials through intermolecular aggregations in the solid state, we prepared some oligomers of the Boc-(L-Phe-D-Oxd)n-OR series with the expectation that the presence of phenyl groups could favour aggregation by means of NH hydrogen bonds and/or pi-stacking interactions. We can show that fibers or fibrils are formed dependent on the length of the foldamer chain. The chemical properties of these compounds have been examined in the solid phase utilizing X-ray diffraction, solid state NMR, SEM, and TEM microscopy. Theoretical calculations have been performed to explain the results.

Functionalized mica sheets and polystyrene films exposing ionisable groups have been used as heterogeneous nucleating surfaces for model proteins. Surfaces with different densities of amino or sulfonated groups have been prepared. Crystallization trials were carried out using the hanging-drop vapour-diffusion method. The results show that using these surfaces the starting protein concentration necessary to form crystals is reduced. The effect of these surfaces on the crystallization process may be the consequence of electrostatic interactions between charged residues of proteins and ionisable groups on surfaces. These interactions can be attractive or repulsive, depending on the relative charge of the protein and the surface at the crystallization pH. Both phenomena can induce an increase of the local protein concentration on the surface or in its proximity, favouring nucleation. Moreover, a reduction of the waiting time (an estimation of the nucleation time) was also observed for some proteins, suggesting a surface-stabilization effect on crystal nuclei.

The interaction of proteins with solid surfaces is not only a fundamental phenomenon but is also key to several important and novel applications. In the biomaterials field, protein adsorption is the first step in the integration of an implanted device or material with tissue. In nanotechnology, protein–surface interactions are pivotal for the assembly of interfacial protein constructs, such as sensors, activators and other functional components at the biological/electronic junction. Fundamentally, the interaction of proteins with surfaces involves both protein binding and at least partial unfolding; these studies may therefore increase our knowledge of protein biophysics in general. Synthetic hydroxyapatite Ca10(PO4)6(OH)2 (HA) nanocrystals represent an elective material for bone substitutes. HA nano-crystals are similar to the mineral component of bone as composition and attempt to mimic the structural and morphological features of natural bone crystals by their nanosize, blade-like shape, low degree of crystallinity and high surface reactivity[1]. Bioactivity of a bone substitute material can be evaluated through its chemical reactivity with the physiological environment. In this sense the interaction between proteins and HA has received special attention because it can represent a model to investigate the way by which biomimetic materials communicate. Moreover, the use of probe proteins is very important to characterize the surface of substrate in wet conditions. For this purposes, myoglobin (from horse heart) (Mb), the oxygen binding protein in tissues, is a useful model to test as adsorbate. We investigated the isothermic kinetic adsorption of Mb onto different hydroxyapatites at several pH. In order to better understand this interaction, the HA/Mb has been explored by transmission electron microscopy (TEM), Raman spectroscopy and infrared spectroscopy (FT-IR). UV and CD spectroscopy investigations on the Mb solutions exchanged from the nanocrystals surface have given contributions towards understanding modifications in the protein structure due to the interaction with substrate.Chemical conjugation of bisphosphonates (BP’s) to HA is an effective means to impart it fine-tuned bioactivity[2]. This modification on the apatitic surface can be tested through its effect on the affinity towards proteins with respect to unloaded apatite. The first step is the binding of alendronate with HA and the second is the study of the adsorption of Mb onto this conjugate compared on its adsorption with unfunctionalized HA. The results show that Mb can not be completely adsorbed by the conjugates because the binding sites of the support are partially saturated by alendronate which also avoid the secondary structure modification of Mb. This study could improve our knowledge in the field of biomaterials science, in particular to fine tune a bone-specific drug delivery device and to test HA as a new support for enzyme immobilization.