Non-crystalline Nature Research Articles

Noncrystalline structure of Ni-P nanoparticles prepared by liquid pulse discharge.

Noncrystalline nickel phosphide (Ni-P) nanoparticles have drawn great attention due to their high potential as catalysts. However, the structure of noncrystalline Ni-P nanoparticles is still unknown, which may shed light on explaining the catalysis mechanism of the Ni-P nanoparticles. In this paper, noncrystalline Ni-P nanoparticles were synthesized. Their morphology, particle size, element contents, local atomic structures, as well as the catalysis in the thermal decomposition of ammonium perchlorate were studied. The results demonstrate that the as-prepared Ni-P nanoparticles are spherical with an average diameter of about 13.5 nm. The Ni and P contents are, respectively, 78.15% and 21.85%. The noncrystalline nature of the as-prepared Ni-P nanoparticles can be attributed to cross-linkage between P-doping f.c.c.-like Ni centers and Ni3P-like P centers. The locally ordered Ni centers and P centers are the nuclei sites, which can explain well the origin of initial nuclei to form the crystalline phases after high-temperature annealing. The starting temperature of high-temperature decomposition of ammonium perchlorate was found having a significant decrease in the presence of the noncrystalline Ni-P nanoparticles. Therefore, the as-prepared noncrystalline Ni-P nanoparticles can be used as a potential catalyst in the thermal decomposition of ammonium perchlorate.

Chemical Vapor Deposition Growth of Composite Silicon-Silica Nanowires from Silicon Monoxide Vapor

Si/SiO2 nanowires were synthesized directly by and on silicon substrate surface without the use of a metal catalyst. Since these nanowires grow directly from the silicon substrate, they do not need to be manipulated or aligned for subsequent applications. The obtained nanowires are amorphous with diameters ranging between 50 to 200 nm and few micrometers in length. Parameters like heating temperature, deposition time, and carrier gas flow-rate were found critical in determining the size, structure, growth yield and morphology of the obtained nanowires. FTIR absorption spectra showed high intensity Si–O asymmetric stretching mode and no absorption for Si-Si backbone vibration mode at 620 cm−1which indicates the non-crystalline nature of grown wires.

Kinetic modeling of Fluorine vacancy/F center creation in LiF:Mg,Ti including vacancy-interstitial recombination: Evaluating the factors leading to the lack of supralinearity in the optical absorption F center concentration dose response

Kinetic model simulations of charge carrier transport following irradiation of LiF:Mg,Ti (TLD-100) including Fluorine vacancy/F center creation by the radiation and dose-dependent vacancy-interstitial recombination are presented which describe the experimentally measured linear/exponentially saturating optical absorption dose response of the electron trapping centers at 4.0eV, 4.77eV, 5.08eV (F band) and 5.45eV. Linear/exponentially saturating dose response is commonly observed for centers which are not created by the radiation. The creation of Fluorine vacancies by the radiation could therefore be expected to lead to a supralinear dose response of the F center before the onset of saturation. Nonetheless, the dose response is linear from 10Gy to 500Gy and can be fitted with a dose-filling constant β=6.1·10−5Gy−1 corresponding to a 5% and 25% decrease from linearity at 103Gy and 5·103Gy respectively. The model attempts to resolve a central question concerning the mechanisms leading to the linear/exponentially saturating dose response of the F band even though Fluorine vacancies are being continuously created during the irradiation. The electron-trapping characteristics of the created vacancies are assumed to differ somewhat from the vacancies originally present in un-irradiated samples due to differences in their immediate environment. Vacancy-interstitial recombination for separation distances less than a critical distance, dc is demonstrated to be significant for D>500Gy (dc=36Å) and is an important mechanism contributing to the F center saturation at high dose-levels. The kinetic model accurately simulates the experimentally observed F center dose response over the entire investigated dose range of 10–105Gy under the following conditions: (i) The concentration of vacancies initially present is unexpectedly high at ∼1023m−3, possibly due to the highly doped, non-crystalline and hot-pressed nature of the LiF:Mg,Ti samples. (ii) The transition probability, An4o, for electron capture into the initially-present vacancies is ∼40 times greater than An4, the transition probability for the radiation-created vacancies. These two factors marginalize the effect of the created vacancies at low dose resulting in a linear dose response.

Confirmatory evidence other than 1hnmr spectroscopic technique for complex formation of diclofenac sodium with go-ghrita

Present investigation showing confirmatory evidence for complex formation of Diclofenac sodium (Dic) with Go-Ghrita (GG) by various sophisticated techniques like FT-IR, In-vitro release study, DSC, X-ray diffraction and SEM other than 1 NMR (which is reported earlier). Diclofenac sodium binary mixture in (1:0.5), (1:1), (1:2), (1:3) w/w proportions were prepared by adding to molten Go-Ghrita kept over a water bath at 65-70 o C with continuous stirring. Organoleptic and Physico-chemical properties of GG (procured from Magan Sangrahalaya, Wardha) were as per the specifications given in Ayurvedic Pharmacopoeia (AP) and Indian Pharmacopoeia (IP). All proportions were subjected for FT-IR and in-vitro release behaviour (SGF, P H 1.2 for 2 Hrs and SIF, P H 6.8 for 7 Hrs) and on basis of it, optimized (1:1) w/w proportions were further analyzed and characterized for Differential Scanning Calorimetry, X-ray diffraction and Scanning Electron Microscopy. Carbonyl stretching of benzene acetic acid group to slight higher frequency 9.23 % cm -1 (increase) and (–C=O) linked (-OH) band stretching to slight lower frequency 0.57 cm -1 (decrease) shown in FT-IR spectra, supported by in-vitro release of Diclofenac sodium 99.13±0.31% of (1:1) w/w in sustenance form than remaining. Retention of peaks with lesser intensity in binary mixture of drug with GG, revealed crystalline as well as non-crystalline (amorphous) nature in X-RD, Slight lowering of 17.6 0 C Tm and enthalpy change of 8.51 % (loss) in DSC, and entrapment of Diclofenac sodium crystals in Dic-GG binary mixture shown in SEM photographs, reflecting possible evidence for the formation of inclusion type complex between Diclofenac sodium and GG.

Polarized Raman Spectroscopy of Aligned Insulin Fibrils.

Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventional techniques of structural biology, X-ray crystallography and solution NMR, for fibril characterization is limited because of the non-crystalline and insoluble nature of the fibrils. Here, polarized Raman spectroscopy was used to determine the orientation of selected chemical groups in aligned insulin fibrils, specifically of peptide carbonyls. The methodology is solely based on the measurement of the change in Raman scattered intensity as a function of the angle between the incident laser polarization and the aligned fibrils. The order parameters 〈 P2 〉 and 〈 P4 〉 of the orientation distribution function were obtained, and the most probable distribution of C=O group orientation was calculated. The results indicate that the peptides' carbonyl groups are oriented at an angle of 13±5° from the fibril axis, which is in consistent with previously reported qualitative descriptions of an almost parallel orientation of the C=O groups relative to the main fibril axis.

Differences in Dynamics and Stability of the Wild Type Beta-Amyloid Aβ1-40, and ΔE22-Aβ1-39 (Japanese) Mutant Protofibril Structures, a Molecular Dynamics Study

Alzheimer's disease has been identified as a neurodegenerative disorder associated with protein misfolding due to the aggregation of monomeric beta-amyloid proteins (Aβ) to form fibrillar plaques. Experimental attempts to chemically analyze the structure of Aβ protofibrils and elucidate the mechanism of fibril formation have yet to reveal much about the molecular etiology of AD, due to the low solubility and non-crystalline nature of Aβ. It has been shown experimentally that the ΔE22-Aβ1-39 (Japanese) mutation of β-amyloid leads to production of typical Aβ fibrils essentially instantaneously, much faster than the fibril formation in wild-type (WT) Aβ1-40. To better understand the fibril-forming mechanism of the Japanese mutant peptide, we ran several long all-atom explicit water molecular dynamics simulations of the mutant and WT structures starting from NMR Alzheimer's β-amyloid fibrils (PDB-ID: 2LMN, 2LMO, 2LMP, 2LMQ). The NMR data suggest two different configurations of the fibrils consisting of either two- or three-stacks. Our WT simulations show that the two-stack model is energetically the most stable configuration; both stacks twist around their central axis in a cooperative manner to form a helical structure without any separation between strands. In contrast, monomers rapidly separate from the top and bottom of the three-stack systems. Simulations with just one-stack from either the two- or three-stack systems display the same twist motion, but monomers from the top and bottom of the stack start to separate. These observations suggest that the two-stack system is the most stable nucleation unit. Japanese mutants built for the one-stack system starting from WT protofibril models remain more stable (∼150 kcal/mol) throughout our simulations compared to the WT one-stack system. This might explain the almost instantaneous fibril formation observed for the ΔE22-Aβ1-39 mutation.

Gadolinium-coordinated elastic nanogels for in vivo tumor targeting and imaging

Coordination polymer gels have been recognized as promising hybrid nanoplatforms for imaging and therapeutic applications. Here we report functional metal-organic coordinated nanogels (GdNGs) for in vivo tumor imaging, whose non-crystalline and elastic nature allows for long blood circulation, as opposed to the rapid systemic clearance of common nanohybrids with rigid/crystalline frameworks. The deformable structure of GdNGs was constructed by random crosslinking of highly flexible polyethyleneimines (PEI) with gadolinium (Gd3+) coordination. The in vitro characterization revealed that GdNGs have elasticity with an apparent Young's modulus of 3.0 MPa as well as minimal cytotoxicity owing to the tight chelation of Gd3+ ions. In contrast to common T1-enhancing gadolinium complexes, GdNGs showed the capability of enhancing negative T2 contrast (r2 = 82.6 mm−1s−1) due to the Gd3+-concentrated nanostructure. Systemic administration of fluorescently labeled GdNGs with core and overall hydrodynamic sizes of ∼65 and ∼160 nm manifested efficient targeting and dual-modality (magnetic resonance/fluorescence) imaging of tumor in a mouse model. The minimal filtration by the reticuloendothelial system (RES) suggests that the structural deformability helps the large colloids circulate in the blood stream for tumor accumulation. The unusual performance of a large Gd3+-complexed colloid (minimal RES sequestration and high T2 contrast enhancement) represents the versatile nature of nanoscopic organic-inorganic hybridization for biomedical applications.

Is the novel amyloid-β tetramer fold a stable conformation?

In the pathogenesis of Alzheimer's disease (AD), the most common neurodegenerative disorder, the amyloid-β (Aβ) peptide plays a key role. Originally, the Aβ fibrils were postulated to be the neurotoxic agents for a long time, because an increased presence of extracellular amyloid plaques, composed primarily of insoluble Aβ fibrils, is found in the brain of affected patients. Recent studies, however, showed a higher cytotoxicity for small Aβ oligomers than for the Aβ fibrils so that these soluble Aβ oligomers are moving to the centre of interest now [1,2]. Because of the unstable and noncrystalline nature of these species, obtaining structural information for small oligomers is an experimentally challenging task. Novel structural insight was obtained from a recent crystal structure of a tetramer formed by the amyloidogenic residues 18-41 of the Aβ peptide. To enhance stability, this fragment was genetically engineered into the CDR3 loop region of a shark Ig single variable domain antibody [3]. Since the respective crystal structure is stabilized by the antibody moiety, we investigated, whether the respective topology also represents a stable fold for the isolated Aβ-peptide. We performed molecular dynamics simulations in explicit solvent for the isolated tetrameric amyloid-β fragment in two different lengths (17-40 and 17-42) and the derived dimer and monomer structures. In contrast to Aβ17-40, we observed a stable dynamical behaviour for the tetramer of Aβ17-42: the extension of the antiparallel β-sheet through the residues 41 and 42 is responsible for the enhanced structural stability. In summary, our results suggest that the novel tetrameric structure represents a stable oligomer conformation for the longer and more neurotoxic Aβ42 species and thus could be a new target in rational drug design aiming at the prevention of toxic oligomer formation.

The Differences in Dynamics and Stability of the Wild Type Beta-Amyloid Aβ1-40, and ΔE22-Aβ1-39 (Japanese) Mutant, a Molecular Dynamics Study

Alzheimer's disease (AD) has been identified as a progressive, neurodegenerative disorder associated with protein misfolding due to the aggregation of monomeric β-amyloid proteins (Aβ) to form fibrillar plaques. Experimental attempts to purify and chemically analyze the structure of Aβ protofibrils and to elucidate the mechanism of fibril formation have yet to reveal much about the molecular etiology of AD, due to the low solubility and non-crystalline nature of Aβ. It has been shown experimentally that the ΔE22-Aβ1-39 (Japanese) mutation of the β-amyloid leads to production of typical Aβ fibrils essentially instantaneously, much faster than the fibril formation in wild-type (WT) Aβ1-40. To better understand the fibril-forming mechanism of the Japanese mutant peptide we have ran several long (μs) all atom explicit water molecular dynamics simulations of the mutant and WT peptide starting from the random-coil structure at two different temperatures (310 and 350 K). Our simulations showed that the ΔE22-Aβ1-39 mutant formed a stable semi-helical hairpin structure about 5 times faster than the WT. The helical hairpin conformation was less evident in WT trajectory and was quickly unfolded (particularly at 310K). The RMSF plots showed similar patterns of fluctuations in both the WT and mutant backbone atoms. However, the deletion of the E22 lowered the fluctuations of the mutant structure by about 2A at 310K. This fast and stable conformational change in ΔE22-Aβ1-39 can be used as a seed for the rapid fibril formation as observed in the experimental studies.

The Role of Bi2O3 on the Thermal, Structural, and Optical Properties of Tungsten-Phosphate Glasses

Glasses in the ternary system (70 - x)NaPO(3)-30WO(3)-xBi(2)O(3), with x = 0-30 mol %, were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) measurements were performed to confirm the noncrystalline nature of the samples. The influence of the Bi(2)O(3) on the thermal, structural, and optical properties was investigated. Differential scanning calorimetry analysis showed that the glass transition temperature, T(g), increases from 405 to 440 °C for 0 ≤ x ≤ 15 mol % and decreases to 417 °C for x = 30 mol %. The thermal stability against devitrification decreases from 156 to 67 °C with the increase of the Bi(2)O(3) content. The structural modifications were studied by Raman scattering, showing a bismuth insertion into the phosphate chains by Bi-O-P linkage. Furthermore, up to 15 mol % of Bi(2)O(3) formation of BiO(6) clusters is observed, associated with Bi-O-Bi linkage, resulting in a progressive break of the linear phosphate chains that leads to orthophosphate Q(0) units. The linear refractive index, n(0), was measured using the prism-coupler technique at 532, 633, and 1550 nm, whereas the nonlinear (NL) refractive index, n(2) was measured at 1064 nm using the Z-scan technique. Values of 1.58 ≤ n(0) ≤ 1.88, n(2) ≥ 10(-15) cm(2)/W and NL absorption coefficient, α(2) ≤ 0.01 cm/GW, were determined. The linear and NL refractive indices increase with the increase of the Bi(2)O(3) concentration. The large values of n(0) and n(2), as well as the very small α(2), indicate that these materials have large potential for all-optical switching applications in the near-infrared.

Ultrafine sputter-deposited Pt nanoparticles for triiodide reduction in dye-sensitized solar cells: impact of nanoparticle size, crystallinity and surface coverage on catalytic activity

This paper presents a detailed electrochemical impedance spectroscopy and cyclic voltammetry (CV) investigation into the electrocatalytic activity of ultrafine (i.e., smaller than 2 nm) platinum (Pt) nanoparticles generated on a fluorine-doped tin oxide (FTO) surface via room temperature tilted target sputter deposition. In particular, the Pt-decorated FTO electrode surfaces were tested as counter electrode candidates for triiodide () reduction in dye-sensitized solar cells (DSSCs). We observed a direct correlation between size-dependent Pt nanoparticle crystallinity and the reduction activity underlying DSSC performance. CV analysis confirmed the higher electrocatalytic activities of sputter-deposited crystalline Pt nanoparticles (1–2 nm) compared with either sub-nanometre Pt clusters or a continuous Pt thin film. While the low catalytic activity and DSSC performance of Pt clusters smaller in size than 1 nm is believed to arise from their non-crystalline nature and charge-trapping attributes, we attribute the high catalytic performance of larger Pt nanoparticles in the 1–2 nm regime to their well-defined crystallinity and fast electron transfer kinetics. For DSSC applications, the optimized Pt loading was calculated to be ∼2.54 × 10−7 g cm−2, which corresponds to surface coverage by ∼1.6 nm sized Pt nanoparticles.

Morphology evolution including formation of cylindrulite in isotactic polypropylene derived from periodical shear field

It has been well established that periodical shear stress can improve the mechanical performance of isotactic polypropylene during injection molding. In the current study, Polarized Light Microscopy (PLM), two-dimensional Wide-Angle X-ray Diffraction (2D-WAXD), Scanning Electron Microscopy (SEM) were employed to investigate the morphology evolution of vibration sample. Compared with static sample, the morphology of vibration one, which is derived from periodical shear field, exhibits different hierarchy structure: there is an additional fiber layer containing cylindrulites between the shear layer and the core layer, and the orientation is enhanced obviously. Through etching technique, it is found that there exists non-crystalline component in the fibril (core) of cylindrulite, and it may induce the growth of β crystals directly regardless of its non-crystalline nature. Based on the investigated results, a model of formation of cylindrulite is proposed.

An Early Investigation of Ytterbium Nanocolloids for Selective and Quantitative “Multicolor” Spectral CT Imaging

We report a novel molecular imaging agent based on ytterbium designed for use with spectral "multicolor" computed tomography (CT). Spectral CT or multicolored CT provides all of the benefits of traditional CT, such as rapid tomographic X-ray imaging, but in addition, it simultaneously discriminates metal-rich contrast agents based on the element's unique X-ray K-edge energy signature. Our synthetic approach involved the use of organically soluble Yb(III) complex to produce nanocolloids of Yb of noncrystalline nature incorporating a high density of Yb (>500K/nanoparticle) into a stable metal particle. The resultant particles are constrained to vasculature (∼200 nm) and are highly selective for binding fibrin in the ruptured atherosclerotic plaque. Nanoparticles exhibited excellent signal sensitivity, and the spectral CT technique uniquely discriminates the K-edge signal (60 keV) of Yb from calcium (bones). Bioelimination and preliminary biodistribution reflected the overall safety and defined clearance of these particles in a rodent model.

Can We Prevent the Beta Amyloid Peptide, the Characteristic Peptide Found in Alzheimer’s Disease, from Becoming Neurotoxic?

At the early-stages of amyloid research, amyloid fibrils were believed to formed from direct conversions of unstructured monomeric amyloid beta peptide, Aβ, the amyloid protein which characterizes Alzheimer's disease (AD). However, recent structural and kinetic results describe a model for the molecular kinetic level. First, monomeric Aβ molecules in random coil conformations self- assemble into a non-beta sheet intermediate, INβ, which is an aggregate with no amyloid-like β-sheet structures. Then, INβ assembles into a β-sheet intermediate, Iβ, a spherical intermediate that is surrounded by well ordered β-sheets. Great interest is focused on the “hair-pin” region, between residues 16 and 21 also known as the “KLVFFA” region. This region has been shown to contribute to both the secondary and tertiary structure of the peptide; containing the transition portion of the peptide which moves from extracellular to transmembrane regions; and it contains the salt bridge from residue D23 to K28. In spite of the growing importance of these intermediates as a therapeutic target for AD, there is little structural information about the intermediates of the shorter region between resides 22 and 35, Aβ(22-35), because of their non-crystalline and unstable nature. The primary objective of this study is to determine the structure of the hair-pin region of these interval sites without the presence of the “KLVFFA” residues. The examination of the intermediate species for various single point mutations will be explained because not only do they have higher neurotoxicity than the wild type, but also promote the formation of subfibrilliar intermediates. The obtained structures will be compared to those of the WT Aβ intermediates and fibrils, based on a hypothesis that the molecular level structural change caused by the mutation also change the kinetics of misfolding.

The Relationship Between the Number of Residues in the Dynamics and Stability of the A-Beta Amyloid, a Molecular Dynamics Study

Alzheimer's disease has been identified as a progressive, neurodegenerative disorder associated with protein misfolding due to the aggregation of monomeric beta-amyloid proteins (A-beta) to form fibrillar plaques. Experimental attempts to purify and chemically analyze the structure of A-beta protofibrils and to elucidate the mechanism of fibril formation have yet to reveal much about the molecular etiology of AD, due to the low solubility and non-crystalline nature of A-beta. Experimentally, it is shown that the 43-residue strand of A-beta has higher cytotoxicity than the 40 or 42 strands. To better understand the relationship between the number of residue and the fibril-forming propensity of the peptide we have ran several all atom explicit water molecular dynamics simulations of A-beta strands of 40, 42, and 43 residues starting from their NMR structures. Overall, our simulations shows a transition of existing alpha helices to 3(10)- or pi-helices in agreement with experimental data. Our simulation of A-beta 40 and 42 residue strands confirms the substantial shift of secondary structure formation due to the additional two residues. However, it is interesting that the addition of the 43rd residue (threonine) only cause a small secondary structure change in the A-beta strand of 42 residues. Therefore it seems that the residues 41 and 42 are more important in secondary structure formation than the residue 43.

Emission Properties of RE3+ (RE = Eu, Tb): CdO-Li2O-B2O3-TeO2 Glasses

Eu3+ or Tb3+ ions doped Cadmium lithium boro tellurite (CLiBT) glasses with different compositions were prepared by melt quenching method. The non-crystalline nature of the glasses has been verified by the XRD measurements. The photoluminescent properties were characterized with excitation and emission spectra. The emission spectra of Eu3+: CLiBT glasses measured with λexci = 392 nm (7F0→5L6) have shown five emission transitions at 578 nm, 592 nm, 612 nm, 652 nm, 701 nm and are assigned to the transitions 5D0→7F0,7F1,7F2,7F3 &7F4 respectively. Among these, the transition at 612 nm (5D0→7F2) has shown a bright red emission. In the case of Tb3+:CLiBT glasses upon excitation with 376 nm (7F6 → 5G6), the emission transitions have been observed at 436 nm, 456 nm, 450 nm, 467 nm, 488 nm, 508 nm, 542 nm, 583 nm, 612 nm, 653 nm and are assigned to the transitions 5D3→7F4,7F3,7F3 & 5D4→7F6,7F6, 7F5,7F4,7F3 &7F2 respectively. Among these, the transition at 542 nm (5D4→7F5) has shown a bright green emission. In this work, we have reported the emission properties of Eu3+ and Tb3+: CLiBT glasses to explore them as novel display materials.

One-pot synthesis and photoluminescence properties of luminescent functionalized mesoporous SiO2@Tb(OH)3 core–shell nanospheres

A facile one-pot synthesis method was used for the preparation of water-soluble luminescent mesoporous SiO2@Tb(OH)3 core–shell nanospheres. The prepared core–shell nanospheres have amorphous characteristics, with diameters in the distribution range of 105–135 nm. The results of X-ray diffraction (XRD) confirmed the non-crystalline nature of the core–shell nanospheres. Furthermore, the transmission electron microscopy (TEM) results have also revealed a typically ordered mesoporous characteristic of the nanospheres, which have a monodisperse spherical feature in addition to a porous surface and a narrow size distribution. Our optical studies have shown the characteristic emission of Tb3+ (5D4–7Fj, where j = 6, 5, 4, 3, 2, 0), even after making a core–shell structure on the surface of the mesoporous silica nanoparticles, indicating that Tb3+ interacts with the silica framework (possibly the hydroxyl groups on the silica surface), and thus prevents aggregation among the Tb3+ ions, therefore efficiently enhancing the luminescence character of the nanospheres. These water-soluble luminescent mesoporous SiO2@Tb(OH)3 core–shell nanospheres could be highly suitable materials for optical bioprobes, protein labeling and drug-delivery, as particle sizes in the range of 50 to 300 nm are widely sought for drug delivery systems.

Calix[4]arene-Based 1,3-Diconjugate of Salicylyl Imine Having Dibenzyl Amine Moiety (L): Synthesis, Characterization, Receptor Properties toward Fe2+, Cu2+, and Zn2+, Crystal Structures of Its Zn2+ and Cu2+ Complexes, and Selective Phosphate Sensing by the [ZnL

A calix[4]arene conjugate bearing salicylyl imine having dibenzyl moiety (L) has been synthesized and characterized, and its ability to recognize three most important essential elements of human system, viz., iron, copper, and zinc, has been addressed by colorimetry and fluorescence techniques. L acts as a sensor for Cu(2+) and Fe(2+) by exhibiting visual color change and for Zn(2+) based on fluorescence spectroscopy. L shows a minimum detection limit of 3.96 ± 0.42 and 4.51 ± 0.53 ppm and 45 ± 4 ppb, respectively, toward Fe(2+), Cu(2+), and Zn(2+). The in situ prepared [ZnL] exhibits phosphate sensing among 14 anions studied with a detection limit of 247 ± 25 ppb. The complexes of Zn(2+), Cu(2+), and Fe(2+) of L have been synthesized and characterized by different techniques. The crystalline nature of the zinc and copper complexes and the noncrystalline nature of simple L and its iron complex have been demonstrated by powder XRD. The structures of Cu(2+) and Zn(2+) complexes have been established by single crystal XRD wherein these were found to be 1:1 monomeric and 2:2 dimeric, respectively, using N(2)O(2) as binding core. The geometries exhibited by the Zn(2+) and the Cu(2+) complexes were found to be distorted tetrahedral and distorted square planar, respectively. The iron complex of L exists in 1:1 stoichiometry as evident from the mass spectrometry and elemental analysis.

A novel canonical dual computational approach for prion AGAAAAGA amyloid fibril molecular modeling

Many experimental studies have shown that the prion AGAAAAGA palindrome hydrophobic region (113–120) has amyloid fibril forming properties and plays an important role in prion diseases. However, due to the unstable, noncrystalline and insoluble nature of the amyloid fibril, to date structural information on AGAAAAGA region (113–120) has been very limited. This region falls just within the N-terminal unstructured region PrP (1–123) of prion proteins. Traditional X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy experimental methods cannot be used to get its structural information. Under this background, this paper introduces a novel approach of the canonical dual theory to address the 3D atomic-resolution structure of prion AGAAAAGA amyloid fibrils. The novel and powerful canonical dual computational approach introduced in this paper is for the molecular modeling of prion AGAAAAGA amyloid fibrils, and that the optimal atomic-resolution structures of prion AGAAAAGA amyloid fibils presented in this paper are useful for the drive to find treatments for prion diseases in the field of medicinal chemistry. Overall, this paper presents an important method and provides useful information for treatments of prion diseases.

Optimal atomic-resolution structures of prion AGAAAAGA amyloid fibrils

X-ray crystallography is a powerful tool to determine the protein 3D structure. However, it is time-consuming and expensive, and not all proteins can be successfully crystallized, particularly for membrane proteins. Although nuclear magnetic resonance (NMR) spectroscopy is indeed a very powerful tool in determining the 3D structures of membrane proteins, it is also time-consuming and costly. To the best of the authors' knowledge, there is little structural data available on the AGAAAAGA palindrome in the hydrophobic region (113–120) of prion proteins due to the noncrystalline and insoluble nature of the amyloid fibril, although many experimental studies have shown that this region has amyloid fibril forming properties and plays an important role in prion diseases. In view of this, the present study is devoted to address this problem from computational approaches such as global energy optimization, simulated annealing, and structural bioinformatics. The optimal atomic-resolution structures of prion AGAAAAGA amyloid fibils reported in this paper have a value to the scientific community in its drive to find treatments for prion diseases.