The quest to create a human immunodeficiency virus type 1 (HIV-1) vaccine capable of eliciting broadly neutralizing antibodies against Env has been challenging. Among other problems, one difficulty in creating a potent immunogen resides in the substantial overall sequence variability of the HIV envelope protein. The membrane-proximal region (MPER) of gp41 is a particularly conserved tryptophan-rich region spanning residues 659 to 683, which is recognized by three broadly neutralizing monoclonal antibodies (bnMAbs), 2F5, Z13, and 4E10. In this study, we first describe the variability of residues in the gp41 MPER and report on the invariant nature of 15 out of 25 amino acids comprising this region. Subsequently, we evaluate the ability of the bnMAb 2F5 to recognize 31 varying sequences of the gp41 MPER at a molecular level. In 19 cases, resulting crystal structures show the various MPER peptides bound to the 2F5 Fab'. A variety of amino acid substitutions outside the 664DKW666 core epitope are tolerated. However, changes at the 664DKW666 motif itself are restricted to those residues that preserve the aspartate's negative charge, the hydrophobic alkyl-pi stacking arrangement between the beta-turn lysine and tryptophan, and the positive charge of the former. We also characterize a possible molecular mechanism of 2F5 escape by sequence variability at position 667, which is often observed in HIV-1 clade C isolates. Based on our results, we propose a somewhat more flexible molecular model of epitope recognition by bnMAb 2F5, which could guide future attempts at designing small-molecule MPER-like vaccines capable of eliciting 2F5-like antibodies.

The 31P CP-MAS NMR spectra of trans-square-planar complexes of dihalonickel(II) complexes with tribenzyl-, tricyclohexyl- and tricyclohexylmethylphosphines have been examined and the chemical shift tensors determined. The spans, δ11–δ33, of the tensor components decrease with change in the halide, Cl > Br > I, for all the tertiary phosphines due principally to the deshielding of the δ33 component.

The crystal and molecular structures of the mesitylpseudohalogermanes, Mes2Ge(CN)2 (Mes=2,4,6-trimethylphenyl) and Mes3GeX (X=CN, NCS, N3, NCO, or OH), have been determined by X-ray diffraction methods; the isocyanate and hydroxide crystallise as a 1:1 hydrogen-bonded complex. All are covalent monomers free from pseudohalogen bridging, and all except the cyanides and hydroxide are N-bonded to germanium. Each Ge atom is four-coordinate in a distorted tetrahedral geometry, as evident from (mes)Ge(mes) angles between 112 and 120°, which are attributed to the sterically demanding mesityl groups. The greatest distortion is displayed by Mes2Ge(CN)2, for which the NCGeCN angle of 97.8(3)° and (mes)Ge(mes) angle of 119.8(3)° are also consistent with the bulky mesityl groups and the small steric requirements of the cyano groups. The GeNY angles show a distinctive trend, decreasing from 173.3(5)° for the isothiocyanate (Y=CS), through 153.5(5)° for the isocyanate (Y=CO), to 119.0(7)° for the azide (Y=NN), an effect attributed to differences in electronic structure of the pseudohalo ligands. The geometries of the compounds examined here are compared with those of some other tri- and dimesityl-Group 14 metal derivatives as well as related phenylgermanium compounds.

Three new cage peroxides, 1,6-diaza-3,4,8,9-tetraoxabicyclo[4.4.2]dodecane (3a),1,6-diaza-3,4,8,9-tetraoxa-11-methylbicyclo[4.4.2]dodecane (3b), and 1,6-diaza-3,4,8,9-tetraoxatricyclo[4.4.2.4 11,12 ]hexadecane (4), have been prepared by reaction of 1,2-diaminoethane, 1,2-diaminopropane, and trans-1,2-diaminocyclohexane, respectively, with formaldehyde and hydrogen peroxide in aqueous acidic solution. Their structures have been established by X-ray diffraction, and show the bridgehead nitrogen atoms to be predominantly sp 2 hybridized. The structures accord with 1 H and 13 C NMR spectra. Variable temperature NMR studies show that the diperoxide 3a begins to undergo rapid inversion (on the NMR time scale) at about 303 K; up to 370 K the diperoxides 3b and 4 show no conformational change.Key words: cage compounds, formaldehyde, peroxides, amine nitrogen, hybridization.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTRapid Hydrolysis of 2‘,3‘-cAMP with a Cu(II) Complex: Effect of Intramolecular Hydrogen Bonding on the Basicity and Reactivity of a Metal-Bound HydroxideMark Wall, Barry Linkletter, Dan Williams, , Rosemary C. Hynes, and Jik ChinView Author Information Department of Chemistry, McGill University Montreal, Canada H3A 2K6 Cite this: J. Am. Chem. Soc. 1999, 121, 19, 4710–4711Publication Date (Web):May 5, 1999Publication History Received13 April 1998Revised14 December 1998Published online5 May 1999Published inissue 1 May 1999https://doi.org/10.1021/ja981227lCopyright © 1999 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views733Altmetric-Citations76LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (44 KB) Get e-AlertsSUBJECTS:Hydrolysis,Metals,Noncovalent interactions,Phosphates,Reactivity Get e-Alerts

The methods of synthesis, elemental analysis, IR and NMR spectroscopic data and fungicidal activity against Ceratocystis ulmi are reported for a series of triorganotin esters of N-arylidene-omega-amino acids of general formula R3SnO-CO(CH2)(n)N=CHAr (R=Ph, n-Bu; Ar=2-HOC6H4, 2-HOC10H6; n=1, 2, 3 and 5). The crystal structures for two of the compounds, tributyltin N-2-hydroxynaphthalidene glycinate (1) and tributyltin N-2-hydroxynaphthalidene-beta-alaninate (2), have been determined. Although both of these compounds have a trans-R3SnO2 structure, in compound 1 the carboxylate group is monodentate and the fifth coordination position around the tin atom is taken up by a coordinated phenolic group, whereas in 2 the carboxylate group is bridging. These two examples thus correspond to the two different structures reported for trans-R3SnO2 complexes. Both compounds were found to be active against Ceratocystis ulmi, but there was no significant difference in their levels of biological activity against this particular fungus. Apart from compound 1, the other tributyltin compounds reported are believed to adopt the carboxylate bridging mode shown by compound (2).Crystal data: for 1, crystals monoclinic, space group P2(1)/c, a =012.9435(11) Angstrom, b = 13.5769(10) Angstrom, c = 15.7715(12) Angstrom, beta = 108.919(6)degrees Z = 4, R-f = 0.046 and R-w = 0.058 for 1448 significant reflections; for 2, crystals monoclinic, space group C 2/c a = 24.588(14) Angstrom, b = 9.733(3) Angstrom, c = 27.611(12) Angstrom, beta = 113.49(4)degrees Z = 8, R-f = 0.053 and R-w = 0.069 for 3822 significant reflections. (C) 1998 John Wiley & Sons, Ltd.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTStructure and Reactivity of Dinuclear Cobalt(III) Complexes with Peroxide and Phosphate Diester Analogues Bridging the Metal IonsJin Seog Seo, Rosemary C. Hynes, Daniel Williams, Jik Chin, and Nack-Do SungView Author Information Department of Chemistry, McGill University Montreal, Canada H3A 2K6 Department of Agricultural Chemistry Chung-Nam National University, Taejeon 305-764 Korea Cite this: J. Am. Chem. Soc. 1998, 120, 38, 9943–9944Publication Date (Web):September 10, 1998Publication History Received8 April 1998Published online10 September 1998Published inissue 1 September 1998https://pubs.acs.org/doi/10.1021/ja9811905https://doi.org/10.1021/ja9811905rapid-communicationACS PublicationsCopyright © 1998 American Chemical SocietyRequest reuse permissionsArticle Views588Altmetric-Citations35LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Hydrolysis,Metals,Organophosphorus compounds,Oxides,Phosphates Get e-Alerts

The complexes [Cu(NNS)X] (HNNS represents the 2-benzoylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; X = Cl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectral evidence support a square-planar structure for the [Cu(Bp-SR)X] (Bp-SR=the benzoylpyridine Schiff bases; R = CH3, CH2C6H5; X = Cl, Br) and [Cu(Bp-SMe)NO3] complexes and a five-coordinate distorted square-pyramidal structure for the [Cu(Bp-SBz)NO3] complex. The crystal structures of [Cu(Bp-SMe)NO3] and [Cu(Bp-SBz)NO3] have been determined by X-ray diffraction studies. The complex [Cu(Bp-SMe)NO3] crystallizes in the triclinic space group P1 with a = 7.600(3), b = 10.5346(2), c = 11.564(3) Angstrom, alpha = 116.0033(14), beta = 103.91(3), gamma = 91.55(3)degrees, V = 798.3(4) Angstrom(3) and Z = 2. The complex has a distorted square-planar geometry with the copper ion lying in an approximate plane of four coordinating atoms, three of which come from the 2-benzoylpyridine Schiff base of S-methyldithiocarbazate while the fourth coordination site is occupied by an oxygen from the nitrate ligand. The complex, [Cu(Bp-SBz)NO3] crystallizes in the monoclinic space group P2(1)/a with a = 9.0124(19), b = 18.501(5), c = 13.0642(24) Angstrom, beta = 106.377(15)degrees, V = 2089.9(9) Angstrom(3) and Z = 4. The coordination environment around the copper(II) ion is a distorted square-pyramid with three donor atoms (NNS) coming from the 2-benzoylpyridine Schiff base and the fourth and fifth atoms (oxygen) coming from the bidentate NO3- ion. The antifungal and antibacterial properties of the copper(II) complexes have been evaluated against three pathogenic fungi and two bacteria. The Schiff bases and copper (II) complexes display moderate antifungal activities but their activities are less than that of the commercially important antifungal agent nystatin.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Copper(II) complexes of the general formula [Cu(Ap-SMe)X] or [Cu(Ap-SBz)X] (where HAp-SMe and HAp-SBz, respectively, represent the 2-acetylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; XCl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic evidence support a square-planar structure for the [Cu(Ap-SMe)X] (XCl, Br) complexes and a five-coordinate structure for the [Cu(Ap-SBz)NO3] complex. The structure of [Cu(Ap-SBz)NO3] has been determined by X-ray diffraction studies. The geometry of the complex is a distorted square-pyramid with the NNS tridentate ligand and an oxygen atom of the nitrate ion occupying the basal plane. The fifth coordination position is occupied by another oxygen from the nitrate ion. The anti-fungal and anti-bacterial properties of the Schiff bases and their copper(II) complexes have been evaluated against the phytopathogenic fungi A. solanyi, F. equisetti and M. phaseolina and the pathogenic bacteria E. coli and S. aureas. The fungitoxicity of the five-coordinated [Cu(Ap-SBz)NO3] complex approaches that of nystatin, whereas the Schiff base HAp-SMe and its copper(II) complex [Cu(Ap-SMe)NO3] display significant antibacterial activity against E. coli and S. auereas.

The new diorganotin complex ((C6H5)2Sn(OC10H6CH=NCH2COO)) was prepared and characterized by 1H NMR, IR, elemental analysis, and a single crystal X-ray diffraction study. The crystals are monoclinic, space group P21/a with a = 16.9167(9) Å, b = 19.1276(16) Å, c = 26.538(2) Å, β = 100.534(6)°, V = 8442.5(11) Å3, Z = 16, and Dcalc = 1.574 Mg m−3. The final discrepancy factors are RF = 0.030, and RW = 0.021 for 6524 significant reflections. The tin atom has a distorted trigonal bipyramidal coordination, with no short intermolecular contacts. The two axial Sn—O bonds of 2.12 Å and 2.09 Å and the equatorial Sn—N bond of 2.14 Å are among the shortest found in related complexes. Key words: diorganotin(IV), bicycloazastannoxide, trigonal bipyramidal, antitumour.

The phosphate monoester in 2-H is hydrolyzed an unprecedented 10(11) times more rapidly than the corresponding unbound phosphate. Clean conversion of the bidentate monoester (2-H) to the tridentate inorganic phosphate (3), together with the crystal structure of an analog of 2-H, provides detailed mechanistic insight into the hydrolysis reaction.[GRAPHICS]gradients for coherence-transfer selection in combination with H-1 detection is a powerful method for obtaining two- and three-bond H-1-C-13 connectivities between hyperfine-shifted resonances.

A series of bisperoxovanadium complexes (bpV) of the general formula K3[VO(O2)2(L-L′)] has been prepared and characerized. where L-L′ is a pyridinedicarboxylate (2,3-pdc, 2,4-pdc, 2,5-pdc) or 3-acetatoxypicolinate (3-acetpic). Two structures have been determined: bpV(2,4-pdc), P21, a = 38.187(5) Å, c = 11.4088(8) Å, β = 90.546(9)°, V = 3093.8(7) Å3, Z = 8, R/Rw = 0.049/0.055, and bpV(3-acetpic), P1, a = 7.4037(13) Å, b = 10.709(3) Å, c =10.9569(19) Å, α = 110.742(16)°, β = 95.600(19)°, γ = 100.195(19)°, V = 787.4(3) Å3, Z = 2, R/Rw=0.036/0.026. The oxygen atom of the 2-carboxylate group and the oxo ligand are situated in apical positions of a pseudotrigonal plane formed by the nitrogen atom and the centres of the two peroxo groups. The compounds rapidly oxidize sodium tris(3-sulfonatophenyl)phosphine, in water, to the corresponding oxide. The results are discussed with reference to the reported insulin mimetic activity of this class of compounds.

Two new copper(II) chloride complexes of N-(2-hydroxyethyl)bis(pyridylmethyl)amine (CuL(2)) and N-(3-hydroxypropyl)bis(pyridylmethyl)amine (CuL(3)) have been synthesized and characterized. The reactivities of CuL(2) and CuL(3) for cleaving bis(2,4-dinitrophenyl) phosphate (BDNPP) have been compared to that of copper(II) chloride complex of bis(pyridylmethyl)amine (CuL(1)). The copper complex with the hydroxypropyl group (CuL(3)) cleaves the phosphate diester by transesterification while the complex with the hydroxyethyl group (CuL(2)) or the complex without any pendant alcohol groups (CuL(1)) cleaves it by hydrolysis. Furthermore, CuL(3) (k = 7.2 x 10(-1) M(-1) s(-1) at 25 degrees C, pH 8.8) is about two orders of magnitude more reactive than CuL(2) (k = 9.5 x 10(-3) M(-1) s(-1)) and CuL(1) (k = 2.0 x 10(-2) M(-1) s(-1)) for cleaving the diester. The differences in the mechanisms and the reactivities are explained in terms of the differences in the structures of the three copper complexes. Crystal structures of [(L(1)')-Cu(OP(O)(OCH3)(2))(HOCH3)]Cl and [(L(2)')Cu(Cl)]Cl have been determined as structural models of CuL(1) and CuL(2), respectively (L(1)' = bis(2-benzimidazolylmethyl)amine; L(2)' = N-(2-hydroxyethyl)bis(2-benzimidazolylmethyl)amine).

The synthesis and crystal structure of the 1:1 complex formed between triphenyltin chloride and isoquinoline-1-carboxylic acid ([Ph 3 SnCl:C 10 H 7 NO 2 ]) is described. The tin(IV) atom is found to be five coordinate, being bound to three phenyl groups, the chlorine atom, and an oxygen from isoquinoline-1-carboxylic acid. The geometry around the tin atom is that of a trigonal bipyramid, with the three phenyl groups occupying the equatorial positions, and the apical sites taken by the chlorine atom and a carboxyl oxygen from the isoquinoline-1-carboxylic acid. The crystals are triclinic, space group [Formula: see text] with a = 17.932(12) Å, b = 17.935(15) Å, c = 18.686(12) Å, α = 63.16(5)°, β = 81.70(6)°, γ = 68.45(6)°, V = 4986(6)(10) Å 3 Z = 8, and D calc = 1.486 Mg m −3 The final residual is R F = 0.050, on 8375 reflections with I net > 2.5σ(I net ). Two of the cell dimensions are equivalent and there are four molecular units in the unit cell, so precautions are described for ensuring that correct space-group determination had been made and that some concealed symmetry in the final structure had not been overlooked. Keywords: triorganotin, complex, isoquinoline-1-carboxylic acid, fungicidal activity.

EPR spectroscopy of single crystals of tetraethylammonium 2,3,5,6-tetracyano-p-benzoquinonide, ([Et(4)N](+))(2)[Q](2-)(2), at temperatures near ambient indicates the presence of an electronic triplet species (S = 1) exhibiting fine-structure splitting. At 380 K the g- and spin-spin interaction matrices were established from measurements of the fine-structure splitting as a function of angle in three orthogonal crystal planes of crystallographically oriented single crystals: g = (2.0020, 2.0079, 2.0048); D = (-379.6, 243.7, 141.2 MHz). The g(2)-tensor is aligned within a few degrees of the local symmetry elements of the constituent [Q](-) anions of the crystal, i.e., perpendicular to the ring, along 0-0, and across the ring. Comparison of the eigenvectors of D with crystal directions shows that the triplet spectrum is not due to intradimer electronic interaction, i.e., interaction associated with the constituents of the [Q](2-)(2) dimer anion, but rather to interdimer interactions within the anion stack. The change in D as a function of temperature is explained in terms of thermal expansion of the crystal. From the temperature dependence of the spectral intensity it is established that the radical pair has a singlet ground state which lies 3075 +/- 42 cm(-1) (8.79 +/- 0.12 kcal/mol; 0.381 +/- 0.005 eV) below the observed triplet.

Fusarium lateritium Nees is a natural antagonist of the plant pathogen Eutypa armeniacae. In an effort to show that this biological phenomenon is chemically mediated, the bioactive metabolites of F. lateritium were investigated. The cytotoxic alkaloids 2-(1-hydroxyethyl)-4(3H)quinazolinone (1) and 2-acetyl-4(3H)quinazolinone (2), and the three cyclohexadepsipeptides, enniatins B (3), B1 (4), and A1 (5), were isolated and characterized. Metabolites 3, 4, and 5 were found to exhibit strong antifungal activity against E. armeniacae. The structures of the novel metabolites 1 and 2 were elucidated by spectroscopic analysis and that of 2 was confirmed by X-ray crystallography. The absolute stereochemistry of 1 was investigated by 1H and I9F NMR analysis of its Mosher ester derivative.

Tris(5-acetyl-3-thienyl)methane forms an inclusion compound with CCl 4 in a host-guest ratio of 2:1, 2C 19 H 16 O 3 S 3 .CCl 4 , which crystallizes in a P1 triclinic unit cell. Molecular packing in the crystals produces a channel-type cavity in which the CCl 4 molecules are located in two orientationally disordered positions with 65 and 35% occupation

The crystal structure of tetrakis[m-(trifluoromethyl)phenyl]tin(IV), [Sn(C6H4CF3)4], has been determined. The Mossbauer spectrum of the compound shows a single peak with an isomer shift of 1.20 mm s-1. The molecule is tetrahedral with no short intermolecular contacts. The Sn atom is located at a special position and the four Sn-C bond lengths [2.143 (5) angstrom] are equal by symmetry.