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The real crystal structure of fukalite, [Ca.sub.4][Si.sub.2][O.sub.6][(OH).sub.2]([CO.sub.3]), was solved by means of the application of order-disorder (OD) theory and was refined through synchrotron radiation diffraction data from a single crystal. The examined sample came from the Gumeshevsk skarn copper porphyry deposit in the Central Urals, Russia. The selected crystal displays diffraction patterns characterized by strong reflections, which pointed to an orthorhombic sub-structure (the 'family structure' in the OD terminology), and additional weaker reflections that correspond to a monoclinic real structure. The refined cell parameters are a = 7.573(3), b = 23.364(5), c = 11.544(4) (Angstrom], [beta] = 109.15(1)[degrees], space group [P2.sub.1]/c. This unit cell corresponds to one of the six possible maximum degree of order (MDO) polytypes, as obtained by applying the OD procedure. The derivation of the six MDO polytypes is presented in the Appendix (1). The intensity data were collected at the Elettra synchrotron facility (Trieste, Italy); the structure refinement converged to R = 0.0342 for 1848 reflections with 1 > 2[sigma](I) and 0.0352 for all 1958 data. The structure of fukalite may be described as formed by distinct structural modules: a calcium polyhedral framework, formed by tobermorite-type polyhedral layers alternating along b with tilleyite-type zigzag polyhedral layers; silicate chains with repeat every fifth tetrahedron, running along a and linked to the calcium polyhedral layers on opposite sides; and finally rows of [CO.sub.3] groups parallel to (100) and stacked along a. Keywords: Crystal structure, fukalite, calcium carbonate silicate, OD structure

Single crystals of CaIr[O.sub.3] were prepared via flux growth method. Crystal structure parameters, including the anisotropic displacement parameters, are determined based on a single-crystal X-ray diffraction experiment. The unit-cell dimensions are a = 3.147(2), b : 9.866(6), and c = 7.302(5) [Angstrom]. The structure is a three-dimensional dense structure with small vacant spaces. The CaIr[O.sub.3] structure can be described as a pseudo-one-dimensional oxide and is compared with [Ca.sub.4]Ir[O.sub.6] structure. The Ir[O.sub.6] octahedra are significantly distorted, in contrast to other octahedral [Ir.sup.4+] compounds. The O-O distances for faces and edges shared between polyhedra are shorter than other non-shared edge distances. These effects are explained by Pauling's rules and occur to decrease the repulsion between the cations. Thermal vibrations of Ca and Ir atoms are significantly anisotropic. Thermal vibrations of Ca and Ir atoms are restricted in orientation toward the shared face, shared edges, and shortest cation-cation directions. The single-crystal experiment shows that CaIr[[O.sub.3] crystals grow fastest along the a axis and that they assume a prism or needle shape. Strongly preferred orientation of such prism shaped CaIr[O.sub.3]-type post perovskite MgSi[O.sub.3] crystals may develop under the shear flow in the Earth's mantle. Keywords: Post-perovskite, CaIr[O.sub.3], single crystal, X-ray diffraction, lower mantle, D' layer

The effect of copper, zinc and calcium on the structure stability of serum amyloid A (SAA)2.2 in aqueous solution is examined using various probes of quaternary, tertiary, and secondary structure. The result shows that the structure and stability of SAA2.2 are differently affected depending on the metal type and concentration.

The significance of the [gamma]2 calcium-binding site in fibrin polymerization is determined by synthesizing the fibrinogen variant, [gamma]D298,301A. The structure data has indicated that Gly-Pro-Arg-Pro-amide (GPRP) bound to the 'b' site and has induced the same local conformational changes as Gly-His-Arg-Pro-amide (GHRP) to this site.

The interplay between calcium and lectin and chaperone activities of calreticulin (CRT) is studied. It is found that the affinity of CRT for monoglucosylated glycans measured in solution by equilibrium dialysis and fluorescence anisotropy is not affected by the absence of calcium.

Three engineered CaM mutants that are covalently labed with N-(1-pyrene) maleimide at introduced cysteines in the C and N-domains are utilized to understand the relationship between the calcium-dependent activation of individual domains and interdomain structural transitions associated with productive binding to target proteins. The results indicate that interdomain interactions between the opposing domains of CaM occur in solution.

The research presents the synthesis, structure, electrical and physical properties of the polar oxysulfide CaZnOS. The compound is found to exhibit a non-phase-matchable second harmonic generation, as it is ferroelectric and contains very small pyroelectric coefficient between the room temperature and the boiling point of water.

The first molecular structure of an alkaline-earth-metal carbene complex is presented. This calcium bis(iminophosphorno)methandiide chelate complex crystallizes as a dimer in which the carbene carbons bridge the metal centers.

Sorcin-annexin VII interaction was studied directly by Western blot and surface plasmon resonance experiments and the interaction of sorcin with ryanodine receptor (RyR2) was monitored by measuring [Ca.sup.2} spark activity in isolated rabbit heart cells. Results provide experimental support to the proposal that the interaction network around the D helix is central to the [Ca.sup.2}-induced activation mechanism of sorcin.

A calcium vanadate apatite (VAp) in which [PO4.sup.3-] of hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is completely substituted by V[O.sup.3-] in the apatite framework, was synthesized. The VAp acts as a high-performance heterogeneous base catalyst for various carbon-carbon bond-forming reactions such as Michael and aldol reactions in aqueous media and the H-D exchange reaction using deuterium oxide.

An investigation of the influence of the binding of the calmodulin-binding domain of calmodulin kinase I is conducted on the fast internal dynamics of calcium-saturated calmodulin. The results reveal a fundamental role for residual protein entropy in molecular recognition by calmodulin.

In some cell types, oscillations in the concentration of free intracellular calcium ([[Ca.sup.2+]]) are accompanied by oscillations in the concentration of inositol 1,405-trisphosphate ([I[P.sub.3]]). However, in most cell types it is still an open question as to whether oscillations in [I[P.sub.3]] are necessary for [Ca.sup.2+] oscillations in vivo, or whether they merely follow passively. Using a wide range of models, we show that the response to an artificially applied pulse of I[P.sub.3] can be used to distinguish between these two cases. Hence, we show that muscarinic receptor-mediated, long-period [Ca.sup.2+] oscillations in pancreatic acinar cells depend on [I[P.sub.3]] oscillations, whereas shortperiod [Ca.sup.2+] oscillations in airway smooth muscle do not. mathematical model

The sarcoplasmic reticulum [Ca.sup.2+]-cycling proteins are key regulators of cardiac contractility, and alterations in sarcoplasmic reticulum [Ca.sup.2+]-cycling properties have been shown to be causal of familial cardiomyopathies. Through genetic screening of dilated cardiomyopathy patients, we identified a previously uncharacterized deletion of arginine 14 (PLN-R14Del) in the coding region of the phospholamban (PLN) gene in a large family with hereditary heart failure, No homozygous individuals were identified. By middle age, heterozygous individuals developed left ventricular dilation, contractile dysfunction, and episodic ventricular arrhythmias, with overt heart failure in some cases. Transgenic mice overexpressing the mutant PLN-R14Del recapitulated human cardiomyopathy exhibiting similar histopathologic abnormalities and premature death. Coexpression of the normal and mutant-PLN in HEK-293 cells resulted in sarcoplasmic reticulum [Ca.sup.2+]-ATPase superinhibition. The dominant effect of the PLN-R14Del mutation could not be fully removed, even upon phosphorylation by protein kinase A. Thus, by chronic suppression of sarcoplasmic reticulum [Ca.sup.2+]-ATPase activity, the nonreversible superinhibitory function of mutant PLN-R14Del may lead to inherited dilated cardiomyopathy and premature death in both humans and mice. dilated cardiomyopathy | heart failure | calcium cycling | mutation | phosphorylation

Bacterial cell-surface attachment of macromolecular complexes maintains the microorganism in close proximity to extracellular substrates and allows for optimal uptake of hydrolytic byproducts. The cellulosome is a large multienzyme complex used by many anaerobic bacteria for the efficient degradation of plant cell-wall polysaccharides. The mechanism of cellulosome retention to the bacterial cell surface involves a calcium-mediated protein-protein interaction between the dockerin (Doc) module from the cellulosomal scaffold and a cohesin (Coh) module of cell-surface proteins located within the proteoglycan layer. Here, we report the structure of an ultra-high-affinity ([K.sub.a] = 1.44 x [10.sup.10] [M.sup.-1]) complex between type II Doc, together with its neighboring X module from the cellulosome scaffold of Clostridium thermocellum, and a type II Coh module associated with the bacterial cell surface. Identification of X module-Doc and X module-Coh contacts reveal roles for the X module in Doc stability and enhanced Coh recognition. This extremely tight interaction involves one face of the Coh and both helices of the Doc and comprises significant hydrophobic character and a complementary extensive hydrogen-bond network. This structure represents a unique mechanism for cell-surface attachment in anaerobic bacteria and provides a rationale for discriminating between type I and type II Coh modules. cellulose degradation | cellulosome | protein-protein interaction | calcium

Structural and thermodynamic properties of crystal hexagonal calcium apatities were investigated using an all-atom Born-Huggins-Mayer potential by a molecular dynamics technique. The accuracy of the model at room temperature and atmospheric pressure was checked against crystal structural data, with maximum deviations of ca. 4% for the haloapatites and 8% for hydroxyapatite.

The synthesis, crystal structure and chemical bonding of a new ternary polar intermetallic phase, Ca(sub 6)Cu(sub 2)Sn(sub 7) are described. It is found that Ca (sub 6)Cu(sub 2)Sn(sub 7) is metallic compound and exhibits temperature- independent paramagnitism.

The intrachain ferromagnetism in Ca3Co2O6 is described in terms of the spin-state-dependent metal-metal interactions. The spin moments of Ca3FeRhO6 are largely localized on the trigonal prism (TP) sites and hence the spin exchange between adjacent TP sites becomes dominated by antiferromagnetic (AFM) interactions through the Fe-O...O-Fe super-exchange paths.

Mono-, di-, and trinuclear copper-azido moieties are synthesized by varying the size of the countercations and all the complexes are structurally characterized by single-crystal X-ray analysis. The results not only confirm the prevailing role of the Cu(super II)-mu(sub 1,1)-N(sub azido)-Cu(super II) systems but also validates the lower value predicted for the critical angle.

The study reveals that high-spin d(super 6) ions at trigonal prism and linear two coordinate sites have unaxial properties and this is stated by calculating their low-lying eigenstates under the influence of crystal field and spin orbit coupling. The unixial magnetic properties of Ca3Co2O6 with high-spin Co(super 3+) (d(super 6) ions at the trigonal prism sites and of those of Fe[C(SiMe3)3]2 with high-spin Fe(super 2+)(d(super 6) ions at linear two coordinates sites are interpreted.

A series of samples with the composition Ca1-xNa2xAl2B2O7 were investigated and a hexagonal structure with unusually large range of homogeneity was revealed. The hexagonal phase consist of [AL2b2O7](infinity)(super 2-) lamellae stacked along the c axis, as in CaAl2B2O7 and Na2Al2B2O7.

Twenty five amino acids within the 'N', 'P', and 'A' domains of Calcium(super 2+) ATPase(SERCA1) headpiece were subjected to site directed mutagenesis, taking advantage of high yield expression system. Functional and conformational effects of mutations were interpreted systematically in the light of the high resolution WT(wild type) structure.

The related parameters of cation size and valence that control the crystallization of Sr3CaRu2O9 into a 1:2 B-site-ordered perovksite structure were explored by cationic substitution at the strontium and calcium sites and application of high pressure. The size of calcium relative to ruthenium is a critical structure-determining factor in Sr3CaRu2O9.

CaC(sub n), CaC(sub n)(super +), and CaC(sub n)(super -) (n = 1-8) monocyclic clusters are studied by using the B3LYP density functional method. Predictions for several molecular properties that could help in possible experimental characterization, such as equilibrium geometries, electronic structures, dipole moments, and vibrational frequencies are reported.

Density functional theory calculations are used to investigate the gas-phase chelating structures of Ca(super 2+) with glutamic acid. Accurate geometric structures, relative stability, charge distributions, bonding analysis, and harmonic vibrational frequencies are explored.

The 2.8 A[ring] crystal structure of the type II restriction endonuclease HincII bound to Ca(super 2+) and cognate DNA containing GTCGAC is presented. Kinetic data consistent with an important role for the 3'- phosphate group in DNA cleavage by HincII are presented.

By immersing ether Au(111) or Au(100) substrate into benzene ad layers of 15-crown 15-ether- substituted cobalt (II) phtalocyanine (CoCRPc) were prepared. Relationship between CRPc and Au lattice is significant in trapping of Ca(super 2+) ions in crown rings.

Small-angle X-ray scattering (SAXS) is used to study the structure of a complex formed from DNA, calcium and DPPC. The effects of calcium on lipids are studied.

The examples of group 2 metal-gallium heterocycle complexes containing the first crystallographically characterized Ga-Mg and Ga-Ca bonds in molecular compounds are reported. These have the potential for use as a milder reagents for the transfer of the gallium heterocycles to less electropositive metals than the potassium salts of [:Ga{(ArNCH)2}(super -).

The electronic nature and the layered oxysulfide [Sr.sub.2-x][Ca.sub.x][Cu.sub.2]Co[O.sub.2][S.sub.2] with Co[O.sub.2] which has strongly correlated Co[O.sub.2] square planes is studied. A remarkable decrease in the electrical resistivity in the Sr defect system, and the chemical shifts of S 2s and S 2p orbitals suggest that carriers are doped into [Cu.sub.2][S.sub.2] layers.

The thickness and substrate dependences on the surface and interface structures and the associated temperature dependence of the resistance of thin La0.67Ca0.33MnO3 (LCMO) films are discussed. Different texture structure of LCMO films on the ALO and YSZ substrates is observed and the LCMO films deposited on the STO substrate are well crystallized in the (001) orientation.

Modified linear combination of the atomic orbital (LCAO) band method was used for examining the electronic structures and magnetic properties of manganites Nd0.5Ca0.5MnO3 with a charge-exchange-type antiferromagnetic ordering. The partial density of states (DOS) of Mn ions at Fermi level (Ef) declines due to local spin density approximation and Coulomb energy (LSDA + U) and fails in yielding a charge ordering or an insulating energy gap.

Structure, magnetic, and transport properties of the compounds La(sub 2/3)Ca(sub 1/3)Mn(sub 1-x)Ti(sub x)O(sub 3) (0 less than or equal to x is less than or equal to 0.3) are investigated. It is reported that the magnetic dilution should be responsible for the experimental results.

Quantum-chemical calculations including band structure and electron localization function (ELF) analysis are employed to study the electronic properties of [Ca.sub.2]Li[C.sub.3]H crystals generated by the reaction of carbon and Ca[H.sub.2] in a calcium/lithium flux mixture. The [Ca.sub.2]Li[C.sub.3]H structure is observed to feature the rarely seen [C.sub.3.sup.4-] carbide anion and the protolysis reaction of this compound with ammonium chloride produces [C.sub.3][H.sub.4].

Low temperature memory phenomena observed on the [La.sub.0.7][Ca.sub.0.3]Mn[O.sub.3] nanomanganite system is screened for atomic spin glass (SG), super spin glass (SSG), cluster glass (CG) and superparamagnetic behavior. The results have shown the existence of various time and length scales in the system, which is described by considering the nanoparticles with grain boundary spin disorder and the presence of noncompact ferromagnetic clusters.

Electrical, magnetic and Mossbauer measurements are performed on [La.sub.0.67-x][Eu.sub.x][Ca.sub.0.33]Mn[O.sub.3] in order to study different grain size materials. The combined effect of chemical pressure induced due to the additional rare earth doping and smaller grain size has led to a more stable AFM phase where no such hysteresis is observed in field cooled cooling and warming cycles of magnetization measurements.

Several studies are conducted to explain the structural, magnetic, as well as the transport properties exhibited by the [Bi.sub.0.6][Ca.sub.0.4]Mn[O.sub.3] compounds. The various impacts caused by the progressive substitution of the Bi ion by the La ion on these properties are also analyzed.

Magnetic structure and dielectric response of [Ca.sub.3]CoMo[O.sub.6] are analyzed as a function of temperature and applied magnetic field. Dielectric measurements have disclosed the presence of magnetoelectric coupling below magnetic ordering temperature and have described the existence of a correlation between magnetic structure and dielectric properties.

The crystal growth of CaTi[O.sub.3] hollow crystals with different microstructures is examined. The formation mechanism of the hollow CaTi[O.sub.3] crystals have helped in controlling the microstructures of the materials and also explain the formation of many other hollow crystals.

Molecular dynamics techniques are used for carrying out large-scale simulations of various 25-mer sequences of ribonucleic acid (RNA) in bulk water and with aqueous montmorillonite clay over many tens of nanoseconds. Specific RNA sequences are folded to characteristic secondary structural motifs over time scales of few nanoseconds, but in aqueous [Ca.sup.2+] environments, RNA has tethered to the clay surface through a nucleotide base, leaving the 3' -end of the strand exposed, thus providing a mechanism for the regiospecific adsorption and elongation of RNA oligomer on clay surfaces.

The combination of a microcontact printing technique and fusion of lipid vesicles to create spatially organized surfaces of lipids and proteins that might mimic renal tubule surfaces are used to fabricate the patterns of phosphatidylserine (DPPS) bilayers and osteopontin (OPN) on silica substrates. The patterning protocol could also be expanded to other urinary molecules and provide a convenient approach for understanding the effects of biomolecules on COM crystal attachment and the pathogenesis of kidney stones.

Several studies are conducted to explain the different magnetic, as well as the structural properties of the nanocrystalline low-doped [La.sub.0.8][Ca.sub.0.2]Co[O.sub.3] nanoparticles with different particle sizes. The freezing temperature of the compounds is shown to change continuously with the magnetic field.

The reaction of bromo-2,4,6-triphenylbenzene with calcium in varying stoichiometric ratios was used to mechanically study the formation of the stable inverse Ca(I) sandwich complex [[(thf).sub.3]Ca([mu]-[C.sub.6][H.sub.3]-1,3,5-[Ph.sub.3])Ca[(thf).sub.3]]. The modified substitution pattern of arylcalcium halides showed that phenyl substituents at the para position induce lability, leading to an enhanced tendency to cleave ethers.