A New High Power LiNi0.81Co0.1Al0.09O2 Cathode Material for Lithium‐Ion Batteries

Among the various Ni‐based layered oxide systems in the form of LiNi_1‐y‐zCo_yAl_zO₂ (NCA), the compostions between y = 0.1–0.15, z = 0.05 are the most successful and commercialized cathodes used in electric vehicles (EVs) and hybrid electric vehicles (HEVs). However, tremendous research effort has been dedicted to searching for better composition in NCA systems to overcome the limitations of these cathodes, particularly those that arise when they are used use at high discharge/charge rates (>5C) and in high temperature (60 °C) environments. In addition, improving the thermal stability at 4.5 V is also very important in terms of the total amount of heat generated and the onset temperature. Here, a new NCA composition in the form of LiNi_0.81Co_0.1Al_0.09O₂ (y = 0.1, z = 0.09) is reported for the first time. Compared to the LiNi_0.85Co_0.1Al_0.05O₂ cathode, LiNi_0.81Co_0.1Al_0.09O₂ exhibits an excellent rate capability of 155 mAh g^?1 at 10 C with a cut‐off voltage range between 3 and 4.5 V, corresponding to 562 Wh kg^?1 at 24 °C. It additionally provides significantly improved thermal stability and electrochemical performance at the high temperature of 60 °C, with a discharge capacity of 122 mAh g^?1 after 200 cycles with capacity retention of 59%.     

Role of the active-site cysteine of Pseudomonas aeruginosa azurin. Crystal structure analysis of the CuII(Cys112Asp) protein

Replacement of the cysteine at position 112 of Pseudomonas aeruginosa azurin with an aspartic acid residue results in a mutant (Cys112Asp) protein that retains a strong copper-binding site. Cu^II(Cys112Asp) azurin can be reduced by excess [Ru^II(NH₃)₆]²⁺, resulting in a Cu^I protein with an electronic absorption spectrum very similar to that of wild-type Cu^I azurin. Cys112Asp azurin exhibits reversible interprotein electron-transfer reactivity with P. aeruginosa cytochrome c ₅₅₁ (μ?=?0.1?M sodium phosphate (pH?7.0);E°(Cu^II/I)?=?180 mV vs NHE); this redox activity indicates that electrons can still enter and exit the protein through the partially solvent-exposed imidazole ring of His117. The structure of Cu^II(Cys112Asp) azurin at 2.4-Å resolution shows that the active-site copper is five coordinate: the pseudo-square base of the distorted square-pyramidal structure is defined by the imidazole N^δ atoms of His46 and His117 and the oxygen atoms of an asymmetrically-bound bidentate carboxylate group of Asp112; the apical position is occupied by the oxygen atom of the backbone carbonyl group of Gly45. The Cu^II–Asp112 interaction is distinguished by an approximately 1.2-Å displacement of the metal center from the plane defined by the Asp112 carboxylate group.     

Characterization of group C meningococcal polysaccharide by light-scattering spectroscopy. III. Determination of molecular weight, radius of gyration, and translational diffusional coefficient.

Group-specific polysaccharides isolated by means of a cetavlon procedure are immunogenic in man and induce protective immunity against meningococcal meningitis. Minute quantities of the polymers in solution can act as vaccines. We now report the first characterization of a fractionated (C-1) group C polysaccharide in 0.4KM KCl and 0.05M sodium acetate by means of light-scattering spectroscopy. Independent measurements of refractive index increments, absolute scattered intensities, angular scattering intensities and line widths as a function of scattering angles and delay times at different concentrations using incident wavelengths of 632.8 nm from a He–Ne laser and of 488 nm from an argon–ion laser yield information on aggregation properties, molecular weight (M_r), radius of gyration 〈r⁰_g〉^1/2_z, translational diffusion coefficient 〈D〉⁰_z, and second virial coefficients A₂ and B₂ of C-1 polysaccharide. At relatively high ionic strength (0.04M KCl + 0.05M sodium acetate), we obtain for the C-1 polysaccharide in solution M_r = 5.15 × 10⁵, 〈r²_g〉^1/2_z = 345 Å, A₂ = 1.25 × 10^?4 ml/g, 〈D〉 = 1.16 × 10^?7 cm²/sec with a corresponding Stokes radius of 240 Å and B₂ = 4.4 ml/g. A₂ and B₂ are the second virial coefficients from intensity- and diffusion-coefficient measurements. The C-1 polysaccharide aggregates in solution and behaves hydrodynamically like random coils. Viscosity and sedimentation studies further confirm our conclusions that the fractioned C-1 polysaccharide aggregates in solution and EDTA can partially break up those aggregates. However, the system remains polydisperse even after adding an excess amount of EDTA. The weight-average molecular weight of the C-1 polysaccharide in solution depends upon ionic strength and exhibits a minimum at ～0.2M KCl. Finally, viscosity, light-scattering, and sedimentation results all show that the aggregated macromolecular system behaves like random-coiled polymers with no measurable shape factors.     

Spectral study of ascorbate oxidase

The electronic, CD and EPR spectra of ascorbate oxidase isolated from the green zucchini squash (Cucurbita pepo medullosa) in 0.1 M phosphate buffer (pH 6.8) have been investigated. The visible absorption bands are clearly resolved in the CD spectrum, where the extrema occur at 735, 610, 550, 475 and 330 nm, while weak additional CD activity possibly occurs near 420 nm. The near-UV spectrum is dominated by the absorption of the aromatic amino acid residues centered at 280 nm, while resolved CD bands occur at 296, 291, 283, 265 and 240 nm. In the far-UV region the protein CD spectrum reflects its secondary structure: a single negative maximum at 218 nm suggests a predominant anti-parallel β conformation for ascorbate oxidase. The frozen solution EPR spectrum of the protein has been fitted according to a new computer simulation procedure. The following parameters were obtained: for the type 1 copper g_z = 2.222, g_x = 2.032, g_y = 2.056, A_z = 59 G, A_x = 11 G, and A_y = 5 G; for the type 2 copper g ? = 2.240, g_⊥ = 2.057, A? = 179 G and A_⊥ = 1 G. Of the eight copper atoms present in the protein four are EPR-detectable: three of type 1 and one of type 2, as shown by computer simulation of the EPR spectrum. Ascorbate oxidase is a rather unstable protein when purified and it is sensitive to a number of environmental factors. Aging of the protein leads to a decrease in the ratio between the type 1 and type 2 coppers. A new species formed at the early stages of the aging process, that has been spectrally characterized, suggests that the loss of the type 1 copper is preceded by a change in the symmetry of the original type 1 site from pseudotetrahedral to pseudotetragonal.     

Electron relaxation and solvent accessibility of the metal site in wild-type and mutated azurins as determined from nuclear magnetic relaxation dispersion experiments

The interaction of water molecules with copper in wild-type azurin and different site-directed mutants of the coordinated residues is studied by nuclear magnetic relaxation dispersion. Different degrees of solvent accessibility are found. The low relaxivity of wild-type azurin agrees with a solvent-protected copper site in solution, the closest water being found at a distance of more than 5?Å from the copper. This low relaxivity contrasts with the relatively large relaxivity of the His46Gly and His117Gly azurin mutants, which shows clear evidence of copper-coordinated water. The data on the latter mutants are best analyzed in terms of one and two water molecules coordinated to the copper in His46Gly and His117Gly, respectively. The Met121His azurin mutant shows an intermediate behavior. The data are analyzed in terms of an increased solvent accessibility with respect to the wild-type azurin, resulting in semi-coordination of water at low pH. These different modes of coordination lead to different geometries, ranging from the trigonal type 1 site of wild-type azurin to the tetragonal type 2 copper sites of the His117Gly and His46Gly azurin mutants through a so-called type 1.5 site of the Met121His mutant. A correlation is found between the relaxation time (τ_s) of the unpaired electron of copper(II) and the geometry of the metal site: as the tetragonal character decreases the relaxation becomes significantly faster. τ_s values of ≤1?ns are found for the tetrahedrally distorted type 1 and type 1.5 sites and of 5–15?ns for the tetragonal type 2 sites.     

Purification and preliminary crystallographic studies on azurin and cytochrome c' from Alcaligenes denitrificans and Alcaligenes sp. NCIB 11015.

Purification and crystallisation procedures are reported for azurin and cytochrome c′ from Alcaligenes denitrificans and Alcaligenes sp. NCIB 11015. The azurin crystals from A. denitrificans are suitable for high-resolution X-ray structure analysis. They are orthorhombic, space group C222₁ (with marked tetragonal pseudo-symmetry), cell dimensions $\text{a = 75.0}\text{A}\text{?}\text{, b = 74.1}\text{A}\text{?}\text{, c = 99.5}\text{A}\text{?}$, with two molecules per asymmetric unit. The cytochrome c′ crystals from both species are hexagonal, space group P6₁22 (or P6₅22), cell dimensions $\text{a = b = 54.7}\text{A}\text{?}\text{, c ~ 185}\text{A}\text{?}$, γ = 120 °, with one subunit (molecular weight 14,000) in the asymmetric unit.     

The crystal structure of cobalt-substituted pseudoazurin from Alcaligenes faecalis

The Cu(II) center at the active site of the blue copper protein pseudoazurin from Alcaligenes faecalis has been substituted by Co(II) via denaturing of the protein, chelation and removal of copper by EDTA and refolding of the apo‐protein, followed by addition of an aqueous solution of CoCl₂. Sitting drop vapour diffusion experiments produced green hexagonal crystals, which belong to space group P6₅, with unit cell dimensions a = b = 50.03, c = 98.80 Å. Diffraction data, collected at 291 K on a copper rotating anode X‐ray source, were phased by the anomalous signal of the cobalt atom. The structure was built automatically, fitted manually and subsequently refined to 1.86 Å resolution. The Co‐substituted protein exhibits similar overall geometry to the native structure with copper. Cobalt binds more strongly to the axial Met86‐Sδ and retains the tetrahedral arrangement with the four ligand atoms, His40‐Nδ₁, Cys78‐Sγ, His81‐Nδ₁, and 86Met‐Sδ, although the structure is less distorted than the native copper protein. The structure reported herein, is the first crystallographic structure of a Co(II)‐substituted pseudoazurin. © 2010 Wiley Periodicals, Inc. Biopolymers 95: 202–207, 2011.     

A theoretical estimate of the energy barriers between stable conformations of the proline dimer.

Semi-empirical energy calculations for an internal Pro-Pro dimer are presented that take into account the nature of the flexibility of the proline ring due to its puckering. Calculations show that three stable conformations are available for the dimer: the cis (ω = 0°, ψ = 160°); the trans (ω = 180°, ψ = 160°, also referred to as trans′); and the cis′ (ω = 180°, ψ = ?40°) conformations. The best conformational pathways between these stable conformations are determined. Calculations also show that the barrier for cis′–trans′ conversion is of the same order of magnitude as that for cis–trans conversion.     

Three-dimensional structure of actinoxanthin. IV. A 2.5-Å resolution

The protein actinoxanthin (isolated from Actinomyces globisporus—molecular weight, 10,300; 107 amino acid residues) crystallizes in space group P2₁2₁2₁ with cell dimensions: a = 30.9 Å, b = 48.8 Å, c = 64.1 Å, and Z = 4. The three-dimensional structure of actinoxanthin was determined by the x-ray multiple isomorphous replacement method at 2.5-Å resolution. The molecule is kidney-shaped and has a well-defined cavity. Its characteristic features are the absence of α-helices and the presence of enhanced content of antiparallel β-structure (～55%). A cylinder-shaped formation of seven antiparallel β-strands comprises the main part of the protein structure. The established β-supersecondary structure is characterized by a three-dimensional topology similar to that of immunoglobulin domains, superoxide dismutase subunits, and azurin and plastocyanin proteins.     

Sr2ZnWO6:Eu3+,Bi3+,Li+: a potential white‐emitting phosphor for near‐ultraviolet white light‐emitting diodes

A series of Sr₂ZnWO₆ phosphors co‐doped with Eu³⁺, Bi³⁺ and Li⁺ were prepared using the Pechini method. The samples were tested using X‐ray diffraction and luminescence spectroscopy. The results show that the samples can be effectively excited by near‐ultraviolet (UV) and UV light. The introduction of Bi³⁺ and Li⁺ significantly enhances the fluorescence emission of Sr₂ZnWO₆:Eu³⁺ and changes the light emitted by the phosphors from bluish‐green to white. When excited at 371 nm, Sr_2–x–zZn_1–yWO₆:xEu³⁺,yBi³⁺,zLi⁺ (x = 0.05, y = 0.05, z = 0.05, 0.1 and 0.15) samples emit high‐performance white light. Intense red–orange emission is also observed when excited by UV light. The obtained phosphor is a potential white‐emitting phosphor that could meet the needs of excitation sources with near‐UV chips. In addition, this phosphor might have promising application as a red–orange emitting phosphor for white light‐emitting diodes based on UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Fluorescence properties of the allenic carotenoid fucoxanthin: Implication for energy transfer in photosynthetic pigment systems

The fluorescence spectrum of an allenic carotenoid, all-trans-fucoxanthin isolated from a brown alga, has been reported for the first time. This carotenoid is known to function efficiently as a primary photosynthetic antenna pigment in marine algae. The emission bands were located around 630, 685 and 750 nm in CS₂ at 20°C, absorption bands being located at 448, 476 and 505 nm. The energy difference between the 0-0 bands of absorption and emission spectra was about 3900 cm^-1 and location of the emission maximum was less sensitive to the polarizability of solvents than that of the absorption maximum. These clearly indicate that the emission originates from the optically forbidden singlet state (2A_g). This is in contrast to other carotenoids whose emission is assigned to 1B_u state, probably due to the symmetric structure of the conjugated double bond responsible for the absorption in the visible region. A rapid internal conversion from 1B_u to 2A_g state might be facilitated by distorted structure of the conjugated double bond of fucoxanthin. The energy level responsible for the emission is almost identical to the Q_y level of the acceptor molecule (Chl a), thus we propose an energy transfer pathway from the optically forbidden 2A_g state of the carotenoid to the Q_y transition of Chl a in algal pigment systems.     

Purification,crystallization, and preliminary X-ray studies on the rhizome lectin from stinging nettle and its complex with NN′N″-triacetylchitotriose

Single crystals were grown from affinity-purified stinging nettle lectin and from its complex with the specific trisaccharide NN′N″ -triacetylchitotriose by vapor diffusion at room temperature. The lectin crystallizes in space group P2₁2₁2₁ with unit cell dimensions a = 54.3 (1) Å, b = 62.2 (1) Å, and c = 92.4 (2) Å, and diffracts to 3.0 Å resolution. The asymmetric unit contains three lectin monomers. The crystals of the lectin-trisaccharide complex have space group P2₁2₁2₁ with cell constants a = 37.69 (4) Å, b = 48.97 (6) Å, and c = 57.32 (4) Å. These crystals diffract to at least 2.0 Å resolution and the asymmetric unit contains one lectin monomer. A three-dimensional X-ray structure determination is on its way. © 1993 Wiley-Liss, Inc.     

Mechanistic Studies on Metal-pyrophosphate Hydrolysis. Structure of Tetraammine(chloroaquo)cobait(III) dichloride ([CO(NH3)4ClH20]2+•-2Cl−), an Acid Hydrolysis Product of Co(NH3)4HP2O7 and Co(NH3)4PO4

Abstract

The octahedral complex tetraammine(chloroaquo)cobalt(III) dichloride is shown to be the HCl hydrolysis product of both P¹,^2-bidentate tetraammine(pyrophosphato)cobalt(III) [CO(NH₃)₄HP₂0₇ or CoPP] and bidentate tetraammine(phosphato)cobalt(III) [Co(NH₃)₄P0₄or CoP]. The complex crystallizes in the orthorhombic space group Pna2¹ with cell dimensions α=13.033(2)Å, b=6.710(1) Å, and c=10.318(2)Å; the crystal structure was refined to a final disagreement index of 0.033. The average of the four Co-N distances is 1.944±6Å. The Co-Cl distance is 2.257(2)Å and the Co-O(W) distance is 1.971(4)Å. Both protons of the coordinated water molecule are engaged in strong hydrogen bonds to the two nonbonded chloride counterions with 0(W)-C1 distances of 3.087(6)Å and 3.123(6)Å. Each nonbonded chloride is engaged in seven hydrogen bonding interactions resulting from the high ratio of hydrogen bond donors to acceptors in the CoP structure. Cobalt bisphosphate (CoP₂) is the final enzyme hydrolysis product when CoPP is used as substrate in the yeast inorganic pyrophosphatase reaction. The bridge oxygen atom is the site of initial CoPP cleavage both, for HCl catalyzed hydrolysis as well as for enzyme catalyzed hydrolysis.     

Studies on coenzyme binding to glyceraldehyde-3-phosphate dehydrogenase.

Tyrosyl-transfer RNA synthetase from Bacillus stearothermophilus has been crystallized as hexagonal plates, $\text{P3}{}_1\text{21, a = b = 64.6}\text{A}\text{?}\text{, c = 238.8}\text{A}\text{?}$, with the dimeric molecule (molecular weight, 90,000) occupying two crystallographic asymmetric units (Reid et al., 1973). Three heavy-atom derivatives have been identified and X-ray diffraction measurements have been made to 2.7 Å resolution, using the oscillation method. The three heavy-atom derivatives were methyl mercury (two sites, half occupied, 3 Å apart), uranyl acetate (single fully occupied site) and chloroplatinite PtCl₄^2? (three sites of differing occupancy). The results were used to compute an electron density map at 2.7 Å resolution, which shows the monomer as a unit of about 60 Å × 60 Å × 40 Å. The maximum dimension of the dimer is about 130 Å. Most of the polypeptide chain has been traced uniquely. It includes five α-helices more than 12 Å long and several shorter helices. A six-stranded pleated-sheet structure lies in the centre of each subunit. The catalytic site of the enzyme is believed to be adjacent to the mercury-binding group.     

Effect of nickel(II) substitution on the resonance Raman and NMR spectra of Alcaligenes xylosoxidans azurin II: implications for axial-ligand bonding interactions in cupredoxin active sites

Assignment of the resonance Raman (RR) spectrum of Ni(II)-substituted azurin II from Alcaligenes xylosoxidans (NCIMB 11015) using Ni isotope substitution reveals an anomalously low Ni-S(Cys) stretching frequency of 349?cm^–1, suggesting the presence of significant axial-ligand bonding interactions. The X-ray crystal structure of Ni(II)-substituted azurin from Pseudomonas aeruginosa shows that there are two potential axial ligands to the Ni ion: a peptide carbonyl O at a distance of 2.46?Å, together with a long-range interaction from a methionine sulfur (S′) at a distance of 3.30?Å. Comparison of the RR properties of Ni(II)-substituted azurin II with stellacyanin (which contains an axial carbonyl ligand, but no methionine) suggests that the interaction from the carbonyl oxygen ligand alone is not sufficient to account for the weak Ni azurin metal-thiolate bond. Instead, it appears that a Ni-methionine bonding interaction is also required to explain the low Ni-S(Cys) stretching frequency in Ni(II)-substituted azurin II. This hypothesis is supported by NMR studies which show a large paramagnetic shift for the protons of the methionine side-chain. Thus, it appears that Ni-substituted azurin II is best described as five-coordinate, and that significant Ni(II)-methionine bonding interactions can occur at a distance of 3.3?Å.     

Cocrystallization of Lysyl–tRNA synthetase from Thermus thermophilus with its cognate tRNAlys and with Escherichia coli tRNAlys

Lysyl-tRNA synthetase from Thermus thermophilus has been cocrystallized with either its cognate tRNA^lYS or Escherichia coli tRNA^lys using ammonium sulfate as precipitant. The crystals grow from solutions containing a 1:2.5 stoichiometry of synthetase dimer to tRNA in 18–22% ammonium sulfate in 50 mM Tris-maleate buffer at pH 7.5. Both complexes form square prismatic, tetragonal crystals with very similar unit cell parameters (a = b = 233 Å, c = 119 Å) and diffract to at least 2.7 Å resolution. However the homocomplex is of space group P42₁2 and the heterocomplex of space group I422. © 1995 Wiley-Liss, Inc.     

Crystal structure and exchange pathways of the complex l-(trypthophyl-glycinato)copper(II)

The crystal structure and the EPR characterization of the compound Cu [C₁₃H₁₃N₃O₃] is reported. It crystallizes in the P2₁2₁2₁ space group, with a=8.2829(5), b=9.347(2), c=16.499(2) Å and Z=4. The copper ion is in a distorted square planar coordination, bonded to two nitrogen and one oxygen atoms from one dipeptide and to an oxygen atom from a symmetry-related molecule. Thus, neighbor copper atoms at 5.14 Å are connected by equatorial syn–anti carboxylate bridges giving rise to a chain structure along the b-axis. The chains are connected via hydrogen bonds and cation–π interactions, the latter being provided by the ‘sandwich’ structure involving each copper atom and two tryptophan residues from neighbor molecules. The EPR spectra of polycrystalline sample imply an essentially d_x2−y2 ground state orbital for the Cu(II) ions. The g-values reflect a slightly distorted axial symmetry around the Cu(II) ions as expected from the structural results. No hyperfine interaction is observed, which is indicative of the presence of exchange interactions between the copper atoms as suggested by the X-ray results as well.     

Crystallization and preliminary crystallographic data of a neutrophil migration-inducing lectin (KM+) extracted from the seed of Artocarpus integrifolia

The tetrameric KM+ lectin from the seeds of Artocarpus integrifolia has, when compared to other plant lectins, the singular property of directly inducing neutrophil migration into the peritoneal cavity or into the air pouch of rats. This protein crystals have been grown and they belong to the orthorhombic system with space group C222₁. The unit cell parameters are a = 54.4 Å, b = 127.9 Å and c = 99.8 Å. A native diffraction dataset to 2.8 Å was collected and an analysis of the self-rotation function has shown the presence of only one independent non-crystallographic 2-fold axis orthogonal to the crystal b-axis, compatible with a dimer in the asymmetric unit. Proteins 27:157–159 © 1997 Wiley-Liss, Inc.