Interactions between anti-ErbB2 antibody A21 and the ErbB2 extracellular domain provide a basis for improving A21 affinity

Anti-ErbB2 antibodies are well researched for the therapy of ErbB2-overexpressing tumors. The therapeutic potential and efficacy of these antibodies are closely related to their affinities to ErbB2. Previously we reported that an anti-ErbB2 antibody A21 targeting a conformational epitope comprising several loops in ErbB2 extracellular subdomain I and II could inhibit the proliferation of ErbB2-overexpressing cancer cells in vitro and in vivo. Here we found that another structureless and non-conserved loop in subdomain I of ErbB2 extracellular domain (ECD) was important for binding to A21, and then the antigen-contact sites on A21 were determined by site-directed mutation. The loop was constructed by molecular modeling, and a new model of A21-ErbB2 complex was generated by docking using the crystal structure of the scfv A21 and the model of ErbB2 ECD with the loop built. Based on the complex model, computational design for A21 affinity improvement was performed to enhance its affinity to ErbB2. Two mutants with about 1.7-fold improvement in affinity were obtained. Our study provided a rational molecular basis for affinity improvement and mechanism investigation of A21.     

Polymorphism of NaVO2F2: a P21/c superstructure with pseudosymmetry of P21/m in the subcell

The ADDSYM routine in the program PLATON [Spek (2015). Acta Cryst. C 71 , 9–18] has helped researchers to avoid structures of (metal–)organic compounds being reported in an unnecessarily low symmetry space group. However, determination of the correct space group may get more complicated in cases of pseudosymmetric inorganic compounds. One example is NaVO₂F₂, which was reported [Crosnier‐Lopez et al. (1994). Eur. J. Solid State Inorg. Chem. 31 , 957–965] in the acentric space group P2₁ based on properties but flagged by ADDSYM as (pseudo)centrosymmetric P2₁/m within default distance tolerances. Herein a systematic investigation reveals that NaVO₂F₂ exists in at least four polymorphs: P2₁, (I), P2₁/m, (II), P2₁/c, (III), and one or more low‐temperature ones. The new centrosymmetric modification, (III), with the space group P2₁/c has a similar atomic packing geometry to phase (I), except for having a doubled c axis. The double‐cell of phase (III) arises from atomic shifts from the glide plane c at (x, , z). With increasing temperature, the number of observed reflections decreases. The odd l reflections gradually become weaker and, correspondingly, all atoms shift towards the glide plane, resulting in a gradual second‐order transformation of (III) into high‐temperature phase (II) (P2₁/m) at below 493 K. At least one first‐order enantiotropic phase transition was observed below 139 K from both the single‐crystal X‐ray diffraction and the differential scanning calorimetry analyses. Periodic first‐principles calculations within density functional theory show that both P2₁/c superstructure (III) and P2₁ substructure (I) are more stable than P2₁/m structure (II), and that P2₁/c superstructure (III) is more stable that P2₁ substructure (I).     

The Crystal Structure of Ni21Sn2P6

During an investigation of the phase equilibria in the ternary system Ni/P/Sn, the existence of a new phase Ni₂₁Sn₂P₆ with a composition close to the known Ni₁₀P₃Sn phase was found. The crystal structure of the new phase was determined using single crystal X‐ray diffraction. The structure was solved employing Patterson and Difference Fourier Analysis. Ni₂₁P₆Sn₂ (space group , a = 1112.2 pm) crystallizes in an ordered variant of the C₆Cr₂₃ structure common to many carbides, borides and phosphides. The relation between Ni₂₁Sn₂P₆ and other C₆Cr₂₃ type phases and to Ni₁₀P₃Sn was established.     

Study of the heat capacity of the derivatives C21H16N2O and C21H19N2O2Br of the alkaloid harmine

Temperature dependences of the heat capacity of the alkaloid harmine derivatives 9-methoxy-2-phenyl-11H-indolysine[8,7-b]indole (C₂₁H₁₆N₂O) and N-(2)-phenacylharminium bromide C₂₁H₁₉N₂O₂Br wer studied by the experimental calorimetry method.     

Oxidation and oxygenation of iron complexes of 2-aza-21-carbaporphyrin

Oxidation and oxygenation of (HCTPPH)Fe(II)Br an iron(II) complex of 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin (CTPPH)H2 have been followed by 1H and 2H NMR spectroscopy. Addition of I2 or Br2 to the solution of (HCTPPH)Fe(II)Br in the absence of dioxygen results in one-electron oxidation yielding [(HCTPPH)Fe(III)Br]+. One electron oxidation with dioxygen, accompanied by deprotonation of a C(21)H fragment and formation of an Fe-C(21) bond, produces an intermediate-spin, five-coordinate iron(III) complex (HCTPP)Fe(III)Br. In the subsequent step an insertion of the oxygen atom into the preformed Fe(III)-C(21) bond has been detected to produce [(CTPPO)Fe(III)Br]-. Protonation at the N2 atom affords (HCTPPO)Fe(III)Br. The considered mechanism of (HCTPPH)Fe(II)Br oxygenation involves the insertion of dioxygen into the Fe-C bond. The 1H NMR and 2H NMR spectra of paramagnetic iron(III) complexes were examined. Functional group assignments have been made with use of selective deuteration. The characteristic patterns of pyrrole and 2-NH resonances have been found diagnostic of the ground electronic state of iron and the donor nature localized at C(21) center as exemplified by the 1H NMR spectrum of intermediate-spin (HCTPP)Fe(III)Br: beta-H 7.2, -10.6, -19.2, -20.6, -23.2, -24.9, -43.2; 2-NH -76.6 (ppm, 298 K). The structures of two compounds (HCTPP)Fe(III)Br and (HCTPPO)Fe(III)Br, were determined by X-ray diffraction studies. In the first case, the iron(III) is five-coordinate with bonds to three pyrrole nitrogen atoms (Fe-N distances: 1.985(8), 2.045(7), 2.023(8) A), and the pyrrolic trigonal carbon (Fe-C: 1.981(8) A). The iron(III) of (HCTPPO)Fe(III)Br forms bonds to three pyrrole nitrogen atoms (Fe-N distances 2.104(5), 2.046(5), 2.102(5) A). The Fe-O 2.041(5) A and Fe-C(21) 2.192(5) A distances suggests a direct interaction between the iron center and the pi electron density on the carbonyl group in a eta2 fashion.     

复合氧化物Dy10W2O21的热学性质研究

采用高温固相反应法合成了单相的稀土复合氧化物Dy10W2O21。用热膨胀仪测定了其表观热膨胀系数。采用变温X射线衍射方法测定不同温度衍射谱，TREOR程序进行了指标化，确定为立方晶系，计算了单胞常数和本征热膨胀系数。用热分析仪测定了样品的DSC曲线，表明没有相变发生。对相应含镝的复合氧化物体系反应的标准Gibbs自由能变化进行了计算。     

1,3-Dipolar cycloaddition of 2,6-dichlorobenzonitrile oxide to 2-methyl-N-confused porphyrin. Regio- and stereoselective synthesis and structural characterization of 2-aza-21-carbabacteriochlorin and resolution of 2-aza-21-carbachlorin enantiomers

The 1,3-dipolar cycloaddition reaction of 2-methyl-N-confused porphyrin with 2,6-dichlorobenzonitrile oxide yielded four isomeric monoadducts of carbachlorin type and one diadduct of carbabacteriochlorin type. Two major carbachlorin products, constituting 82% of the monoadducts, were shown to be structural precursors of the unique 2-aza-21-carbabacteriochlorin. Enantiomers of the most abundant isomer of 2-aza-21-carbachlorin (55% of all carbachlorin products) have been resolved. The crystal structures of 2-aza-21-carbabacteriochlorin and the most abundant isomer of 2-aza-21-carbachlorin were characterized by X-ray diffraction.     

Tautomers of azine derivatives. 21. Tautomerism in 2-(2-hydroxyaryl)azines

Tautomerism in 2-(2-hyroxyaryl)azines has been studied using ¹⁷O NMR and UV spectroscopy. Consideration has been given to the influence of solvent and structural factors which facilitate the establishment of a tautomeric equilibrium in these compounds.Communication 20, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–80, January, 1990.     

O-confused oxaporphyrin--an intermediate in formation of 3-substituted 2-oxa-21-carbaporphyrins

[Reaction: see text]. A condensation of 2,4-bis(phenylhydroxymethyl)furan with pyrrole and p-toluylaldehyde in the presence of ethanol formed 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-3-ethoxy-3-hydro-21-carbaporphyrin [(H,EtO)OCPH]H2. The new carbaporphyrinoid has 1H NMR features of an aromatic molecule, including the upfield shift of the inner H(21) atom (-5.48 ppm). Addition of acid removes the ethoxy substituent and converts [(H,EtO)OCPH]H2 into the dication of "true" O-confused oxaporphyrin {[(H)OCPH]H3}2+ via an exocyclic C(3)-O bond cleavage followed by an elimination of the ethoxy group as determined by 1H NMR. Addition of ethanol, water, or pyrrole converts {[(H)OCPH]H3]2+ into [(H,EtO)OCPH]H2, [(H,OH)OCPH]H2, or pyrrole appended O-confused porphyrin [(H,pyrrole)OCPH]H2, respectively. The reaction of [(H,OEt)OCPH]H2 with silver(I) acetate yields a stable Ag(III) complex [(H,OEt)OCP]AgIII substituted at the C(3) position by the ethoxy group and hydrogen. Coordination through the nitrogen donors is reflected by the presence of 107/109Ag scalar splitting seen for the selected -H pyrrolic signals. Addition of TFA to [(H,OEt)OCP]AgIII produces a weakly aromatic O-confused porphyrin complex {[(H)OCP]AgIII}+. In the course of this reversible process the tetrahedral-trigonal rearrangements originate at the C(3) atom but extend its consequences on the whole structure. Insertion of silver into the hydroxy analogue of [(H,OEt)OCPH]H2, i.e., [(H,OH)OCPH]H2, was accompanied by ligand oxidation, yielding carbaporpholactone which contains the lactone functionality instead of the regular furan moiety embedded in the carbaporphyrin ligand of [(O)OCP]AgIII. The structure was determined by X-ray crystallography. The macrocycle is only slightly distorted from planarity, and silver(III) is located in the NNNC plane.     

Kinetic studies of the reactions CH2I2 + HI⇄CH3I + I2 and 2 CH3I⇄CH4 + CH2I2 the heat of formation of the iodomethyl radical

The rate of the reaction CH₂I₂ + HI ? CH₃I + I₂ has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k₁/M^?1 sec^?1) = 11.45 ± 0.18 - (15.11 ± 0.44)/θ. This value, combined with the assumption that E₂ = 0 ± 1 kcal/mole, leads to ΔH (CH₂I, g) = 55.0 ± 1.6 kcal/mole and DH (H? CH₂I) = 103.8 ± 1.6 kcal/mole. The kinetics of the disproportionation, 2 CH₃I ? CH₄ + CH₂I₂ were studied at 331° and are compatible with the above values.     

Synthesis,crystal structure,and physical properties of a new boride Ga2Ni21B20 with a modified Zn2Ni21B20-type structure

A ternary boride Ga₂Ni₂₁B₂₀, with modified Zn₂Ni₂₁B₂₀-type structure (space group I4/mmm, and lattice parameters a = 7.2164(1) Å, c = 14.2715(4) Å), was synthesized from the constituent elements. Single crystal diffraction data reveal Ni at 8f site splitting into 16m position with nearly half occupancy. In this structure, [Ni₆B₂₀] cages share ligand boron atoms with [Ga₂B₄Ni₉] hexa-capped square prisms, forming two dimensional layers. Layers are interconnected via Ga−Ni interactions and build up a three-dimensional framework. Quasi-two-dimensional infinite planar nets formed by intercrossed Ni atoms are embedded. Ga₂Ni₂₁B₂₀ is a metallic Pauli paramagnet, in agreement with electronic structure calculations, resulting in 8.2 states eV⁻¹ f.u⁻¹ at the Fermi level.     

Darstellung,Kristallstruktur und magnetische Eigenschaften von In2Ni21B6

Preparation, Crystal Structure, and Magnetic Properties of In₂Ni₂₁B₆ In₂Ni₂₁B₆ was prepared by solid state reaction of the elements at 1223 K. The single‐crystals, obtained for the first time, exhibit metallic luster and crystallize in space group Fm 3 m (a = 1059.11(2) pm; Z = 4; 128 symmetry independent reflections; R1 = 0.027; wR2 = 0.125). In₂Ni₂₁B₆ is related to the Cr₂₃C₆‐structure and belongs to the structural family of τ‐borides. The compound melts at 1426 K. Polycrystalline samples of In₂Ni₂₁B₆ are ferromagnetic with a Curie‐Temperature of T_C = 596 K and show metallic conductivity in the range from 12 K to 320 K.     

A polyoxometalate-based single-molecule magnet with an S = 21/2 ground state

Ligand modification transforms a polyoxometalate-anchored cubane-type [Mn(III)(3)Mn(IV)O(4)] core into a centrosymmetric [Mn(III)(6)Mn(IV)O(8)] di-cubane cluster, and restores the slow magnetization relaxation characteristics typical for [Mn(4)O(4)] cubane-based single-molecule magnets.     

Extended average energy perturbation calculation of the 2s2 and 2p21S resonance state energies of two-electron atoms

An extended average energy (EAE) calculation of the 2s² and 2p²¹S resonance state energies of two-electron atoms is carried out. We take the bare-nucleus hamiltonian as the initial approximation and treat the zeroth-order degeneracy by van Vleck perturbation theory, For both H^? and He the lower state energies agree quite well with experiment while the upper state is about 1–2 eV too high. Our remits for He are comparable in accuracy to those obtained by the 1/Z Hartree—Fock perturbation method. A brief concluding discussion of ways to improve the simple EAE technique is presented.