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Adjacent Molecules (adjacent + molecule)
Selected AbstractsHydrogen-bonded supramolecular networks of N,N,-bis(4-pyridylmethyl)oxalamide and 4,4,-{[oxalylbis(azanediyl)]dimethylene}dipyridinium dinitrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010Gene-Hsiang Lee The molecule of N,N,-bis(4-pyridylmethyl)oxalamide, C14H14N4O2, (I) or 4py-ox, has an inversion center in the middle of the oxalamide group. Adjacent molecules are then linked through intermolecular N,H...N and C,H...O hydrogen bonds, forming an extended supramolecular network. 4,4,-{[Oxalylbis(azanediyl)]dimethylene}dipyridinium dinitrate, C14H16N4O22+·2NO3,, (II), contains a diprotonated 4py-ox cation and two nitrate counter-anions. Each nitrate ion is hydrogen bonded to four 4py-ox cations via intermolecular N,H...O and C,H...O interactions. Adjacent 4py-ox cations are linked through weak C,H...O hydrogen bonding between an ,-pyridinium C atom and an oxalamide O atom, forming a two-dimensional extended supramolecular network. [source] Two two-dimensional hydrogen-bonded coordination networks: bis(3-carboxybenzoato-,O)bis(4-methyl-1H -imidazole-,N3)copper(II) and bis(3-methylbenzoato-,N)bis(4-methyl-1H -imidazole-,N3)copper(II) monohydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Ziliang Wang The title two-dimensional hydrogen-bonded coordination compounds, [Cu(C8H5O4)2(C4H6N2)2], (I), and [Cu(C8H7O2)2(C4H6N2)2]·H2O, (II), have been synthesized and structurally characterized. The molecule of complex (I) lies across an inversion centre, and the Cu2+ ion is coordinated by two N atoms from two 4-methyl-1H -imidazole (4-MeIM) molecules and two O atoms from two 3-carboxybenzoate (HBDC,) anions in a square-planar geometry. Adjacent molecules are linked through intermolecular N,H...O and O,H...O hydrogen bonds into a two-dimensional sheet with (4,4) topology. In the asymmetric part of the unit cell of (II) there are two symmetry-independent molecules, in which each Cu2+ ion is also coordinated by two N atoms from two 4-MeIM molecules and two O atoms from two 3-methylbenzoate (3-MeBC,) anions in a square-planar coordination. Two neutral complex molecules are held together via N,H...O(carboxylate) hydrogen bonds to generate a dimeric pair, which is further linked via discrete water molecules into a two-dimensional network with the Schläfli symbol (43)2(46,66,83). In both compounds, as well as the strong intermolecular hydrogen bonds, ,,, interactions also stabilize the crystal stacking. [source] One-Dimensional Coordination Polymers of MnII, CuII, and ZnII Supported by Carboxylate-Appended (2-Pyridyl)alkylamine Ligands , Structure and MagnetismEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009Himanshu Arora Abstract Four new complexes [MnII(L1OO)(H2O)][ClO4]·2H2O (1), [ZnII(L1OO)][ClO4]·2H2O (2), [CuII(L3OO)][CF3SO3]·H2O (3), and [ZnII(L3OO)][ClO4] (4) (L1OO, = 3-[(2-(pyridine-2-yl)ethyl){2-(pyridine-2-yl)methyl}amino]propionate; L3OO, = 3-[(2-(pyridine-2-yl)ethyl){(dimethylamino)ethyl}amino]propionate) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1, 3, and 4 are one-dimensional chain-like coordination polymers. In 1 distorted octahedral MnN3O3 and in 3 square-pyramidal CuN3O2 coordination is satisfied by three nitrogen atoms and an appended carboxylate oxygen atom of the ligand, and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 4 trigonal bipyramidal ZnN3O2 coordination environment is provided by two nitrogen atoms and an appended carboxylate oxygen atom of the ligand in the equatorial plane, and the two axial positions are satisfied by a tertiary amine nitrogen and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 1 the MnII center is coordinated by an additional water molecule. In these complexes each monomeric unit is sequentially connected by syn - anti carboxylate bridges. Temperature-dependent magnetic susceptibilities for 1 and 3 are measured, revealing antiferromagnetic interactions through syn - anti carboxylate bridges between the MII centers. Analysis of the crystal packing diagram reveals that in 1 extensive ,,, stacking involving alternate pyridine rings of adjacent 1D chain exists, which eventually lead to the formation of a 2D network structure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] 4,6-Dinitro- N,N,-di- n -octylbenzene-1,3-diamine, 4,6-dinitro- N,N,-di- n -undecylbenzene-1,3-diamine and N,N,-bis(2,4-dinitrophenyl)octane-1,8-diamineACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009Gary Teng 4,6-Dinitro- N,N,-di- n -octylbenzene-1,3-diamine, C22H38N4O4, (I), 4,6-dinitro- N,N,-di- n -undecylbenzene-1,3-diamine, C28H50N4O4, (II), and N,N,-bis(2,4-dinitrophenyl)octane-1,8-diamine, C20H24N6O8, (III), are the first synthetic meta -dinitroarenes functionalized with long-chain aliphatic amine groups to be structurally characterized. The intra- and intermolecular interactions in these model compounds provide information that can be used to help understand the physical properties of corresponding polymers with similar functionalities. Compounds (I) and (II) possess near-mirror symmetry, with the octyl and undecyl chains adopting fully extended anti conformations in the same direction with respect to the ring. Compound (III) rests on a center of inversion that occupies the mid-point of the central C,C bond of the octyl chain. The middle six C atoms of the chain form an anti arrangement, while the remaining two C atoms take hard turns almost perpendicular to the rest of the chain. All three molecules display intramolecular N,H...O hydrogen bonds between the amine and nitro groups, with the same NH group forming a bifurcated intermolecular hydrogen bond to the nitro O atom of an adjacent molecule. In each case, these interactions link the molecules into one-dimensional molecular chains. In (I) and (II), these chains pack so that the pendant alkyl groups are interleaved parallel to one another, maximizing nonbonded C,H contacts. In (III), the alkyl groups are more isolated within the molecular chains and the primary nonbonded contacts between the chains appear to involve the nitro groups not involved in the hydrogen bonding. [source] Three related benzoannelated diazapolyether macrocycles: effects of macrocycle ring size and position of benzo groups on hydrogen bonding of the amine H atomsACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2007Gary L. N. Smith The benzoannelated diazapolyether macrocycles 6,7,9,10,17,18-hexahydro-5H,11H -8,16,19-trioxa-5,11-diazadibenzo[a,g]cyclopentadecene, C18H22N2O3, (I), 6,7,9,10,12,13,20,21-octahydro-5H,14H -8,11,19,22-tetraoxa-5,14-diazadibenzo[a,g]cyclooctadecene, C20H26N2O4, (II), and 6,7,9,10,17,18,20,21-octahydro-16H,22H -5,8,11,19-tetraoxa-16,22-diazadibenzo[a,j]cyclooctadecene 0.3-hydrate, C20H26N2O4·0.304H2O, (III), show different patterns of hydrogen bonding. In (I), the amine H atoms participate only in intramolecular hydrogen bonds with ether O atoms. In (II), the amine H atoms form intramolecular hydrogen bonds with the phenoxy ether O atoms and intermolecular hydrogen bonds with alkyl ether O atoms in an adjacent molecule, forming a chain linking the macrocycles together via an R22(10) motif. Molecules of (II) were found on a crystallographic twofold axis. In (III), the amine H atoms participate in a hydrogen-bond network with adjacent ether O atoms and with a water molecule [having a partial occupancy of 0.304,(6)] that links the molecules together via a C22(7) motif. [source] Two crystal modifications of (Pro-Pro-Gly)4 -Hyp-Hyp-Gly-(Pro-Pro-Gly)4 reveal the puckering preference of Hyp(X) in the Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs in collagen helicesACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2010Kenji Okuyama Two crystal modifications of a collagen model peptide, (Pro-Pro-Gly)4 -Hyp-Hyp-Gly-(Pro-Pro-Gly)4 [where Hyp is (4R,2S)- l -hydroxyproline], showed very similar unit-cell parameters and belonged to the same space group P21. Both crystals exhibited pseudo-merohedral twinning. The main difference was in their molecular-packing arrangements. One modification showed pseudo-hexagonal packing, while the other showed pseudo-tetragonal packing. Despite their different packing arrangements, no significant differences were observed in the hydration states of these modifications. The peptide in the pseudo-tetragonal crystal showed a cyclic fluctuation of helical twists with a period of 20,Å, while that in the pseudo-hexagonal crystal did not. In these modifications, the puckering conformations of four of the 12 Hyp residues at the X position of the Hyp(X)-Hyp(Y)-Gly sequence were in the opposite conformations to the previous hypothesis that Hyp(X) residues involved in Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs prefer up-puckering and down-puckering conformations, respectively. Detailed investigation of the molecular interactions between Hyp(X) and adjacent molecules revealed that these opposite conformations appeared because the puckering conformation, which follows the hypothesis, is subject to steric hindrance from the adjacent molecule. [source] Synthesis and Structural Characterisation of Palladium and Group-12 Metal Complexes with a Hybrid Phosphanylphosphonate Ferrocene LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2006Abstract Diethyl [1,-(diphenylphosphanyl)ferrocenyl]phosphonate (1) was synthesised by stepwise metallation/functionalisation of 1,1,-dibromoferrocene and studied as a ligand for palladium(II) and group-12 metals. Treatment of [PdCl2(cod)] (cod = ,2:,2 -cycloocta-1,5-diene) with 1 in 1:1 or 1:2 molar ratios gave, respectively, the dinuclear, chloride-bridged complex [{Pd(,-Cl)Cl(1 -,P2)}2] (2) and the mononuclear complex trans -[PdCl2(1 -,P2)2] (3), where 1 coordinates exclusively through the phosphane function. The reactions between 1 and group-12 metal bromides MBr2 in a 1:1 molar ratio gave the adducts [MBr2(1)] [M = Zn (4), Cd (5), and Hg (6)], whose crystal structures change considerably with the metal ion. Thus, whereas 4 is a molecular complex with 1 coordinating as an O1,P2 -chelate, its cadmium(II) analogue is a polymer built up from symmetric {CdBr(,-Br)}2 units interconnected by pairs of O1,P2 -bridging phosphanylphosphonate ligands. Finally, the mercury(II) complex 6 is a halide-bridged dimer, [{Hg(,-Br)Br(1 -,P2)}2]. However, this compound is structurally fluxional in solution (NMR spectra) and, in the crystal, it attains a structure similar to 5 owing to weak interactions between mercury and phosphonate-O1 atoms from adjacent molecules. An isomer to 6, [{HgBr2(1 -,2O1,P2)}2] (7), was isolated from attempted alkylation of 6 and structurally characterised as a dimer, where ligands 1 bridge two {HgBr2} units. All compounds were studied by spectroscopic methods (IR, NMR, mass) and the solid-state structures of 1, 2·,H2O, 3·4,CHCl3, 4, 5, 6·5,C6H6, and 7 have been determined by single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis, Crystal Structure and Characterisation of a Novel Chiral Mixed-Valence Vanadium Oxide Hybrid, [V5O11(dien)3]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2005Ming-Lai Fu Abstract The novel chiral mixed-valence vanadium oxide hybrid [V5O11(dien)3] (1) (dien = NH2C2H4NHC2H4NH2) has been synthesised by a hydrothermal reaction of V2O5 and dien in aqueous solution and characterised by elemental analysis, IR spectroscopy, TG-DSC analysis, magnetism, EPR spectroscopy, single-crystal X-ray diffraction and powder XRD. The X-ray diffraction analysis revealed that the structure of 1 can be regarded as being constructed from two [VVO4]3, groups bicapping three [VIVO(dien)]2+ units to form a discrete asymmetric pentanuclear vanadium complex with the dien ligands coordinating directly to the vanadium(IV) centres. Compound 1 exhibits an interesting tube-like 3D supramolecular structure due to abundant hydrogen-bonding interactions between the oxygen atoms of the inorganic backbone and the hydrogen atoms of the dien ligands from adjacent molecules. The variable-temperature magnetic susceptibility data of 1 suggest a weak ferromagnetic interaction among V4+ ions in the cluster. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The experimental and theoretical QTAIMC study of the atomic and molecular interactions in dinitrogen tetroxideACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2009Vladimir G. Tsirelson The atomic and molecular interactions in a crystal of dinitrogen tetraoxide, ,-N2O4, have been studied in terms of the quantum topological theory of molecular structure using high-resolution, low-temperature X-ray diffraction data. The experimental electron density and electrostatic potential have been reconstructed with the Hansen,Coppens multipole model. In addition, the three-dimensional periodic electron density of crystalline ,-N2O4 has been calculated at the B3LYP/cc-pVDZ level of theory with and without the geometry optimization. The application of the quantum theory of atoms in molecules and crystals (QTAIMC) recovered the two types of intermolecular bond paths between O atoms in crystalline ,-N2O4, one measuring 3.094, the other 3.116,Å. The three-dimensional distribution of the Laplacian of the electron density around the O atoms showed that the lumps in the negative Laplacian fit the holes on the O atoms in the adjacent molecules, both atoms being linked by the intermolecular bond paths. This shows that the Lewis-type molecular complementarity contributes significantly to intermolecular bonding in crystalline N2O4. Partial overlap of atomic-like basins created by zero-flux surfaces in both the electron density and the electrostatic potential show that attractive electrostatic interaction exists between O atoms even though they carry the same net formal charge. The exchange and correlation contributions to the potential energy density were also computed by means of the model functionals, which use the experimental electron density and its derivatives. It was found that the intermolecular interactions in ,-N2O4 are accompanied by the correlation energy-density `bridges' lowering the local potential energy along the intermolecular O...O bond paths in the electron density, while the exchange energy density governs the shape of bounded molecules. [source] Planar packing of tetrachlorodicyanobenzenes.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2009Equimolar mixtures of ortho - and meta -, or ortho - and para -, or meta - and para -tetrachlorodicyanobenzene, C6Cl4(CN)2, form structures with disordered layers containing both kinds of molecules in rhombohedral or pseudo-rhombohedral cells. These structures are similar to the structure of the rhombohedral form of the meta isomer. The guiding force appears to be an intermolecular synthon, in which a nitrile group in one molecule interacts with Cl atoms in two adjacent molecules with N...Cl distances of approximately 3.1,Å. [source] X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1:1 hydrogen-bonded complexes with benzoic acid derivatives: evidence for coupled inter- and intramolecular proton transferACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2006Shasad Sharif Crystal structures of Schiff bases containing pyridoxal (PL), N -(pyridoxylidene)-tolylamine, C15H16N2O2 (I), N -(pyridoxylidene)-methylamine, C9H12N2O2 (III), and their 1:1 adduct with 2-nitrobenzoic acid, (I)+ C7H4NO (II), and 4-nitrobenzoic acid, (III)+ C7H4NO (IV), serve as models for the coenzyme pyridoxal-5,-phosphate (PLP) in its PLP-dependent enzymes. These models allow the study of the intramolecular OHN hydrogen bond of PL/PLP Schiff bases and the H-acceptor properties of their pyridine rings. The free base (I) forms hydrogen-bonded chains involving the hydroxyl side groups and the rings of adjacent molecules, whereas (III) forms related hydrogen-bonded cyclic dimers. The adducts (II)/(IV) consist of 1:1 hydrogen-bonded complexes, exhibiting strong intermolecular bonds between the carboxylic groups of the acids and the pyridine rings of (I)/(III). In conclusion, the proton in the intramolecular O,H,N hydrogen bond of (I)/(III) is located close to oxygen (enolamine form). The added acids protonate the pyridine ring in (II)/(IV), but only in the latter case does this protonation lead to a shift of the intramolecular proton towards the nitrogen (ketoimine form). All crystallographic structures were observed in the open form. In contrast, the formation of the pyridinium salt by dissolving (IV) leads to the cyclic aminal form. [source] Powder X-ray studies of meso -hexamethyl propylene amine oxime (meso -HMPAO) in two different phasesACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Mahmoud Al-Ktaifani Two different forms of meso -3,3,-[2,2-dimethylpropane-1,3-diylbis(azanediyl)]dibutan-2-one dioxime, commonly called meso -hexamethyl propylene amine oxime (HMPAO), C13H28N4O2, designated , and ,, were isolated by fractional crystallization and their crystal structures were determined by powder X-ray diffraction using the direct-space method with the parallel tempering algorithm. The , form was first crystallized from acetonitrile solution, while the , form was obtained by recrystallization of the , phase from diethyl ether. The , form crystallizes in the triclinic system (space group P), with one molecule in the asymmetric unit, while the crystal of the , form is monoclinic (space group P21/n), with one molecule in the asymmetric unit. In both phases, the molecules have similar conformations and RS/EE geometric isomerism. The crystal packing of the two phases is dominated by intermolecular hydrogen-bonding interactions between the two O,H oxime groups of an individual molecule and the amine N atoms of two different adjacent molecules, which lead to segregation of extended poly(meso -HMPAO) one-dimensional chains along the c direction. The structures of the two phases are primarily different due to the different orientations of the molecules in the chains. [source] 4,4,-Bis(2,2,2-trifluoroethoxymethyl)-2,2,-bipyridineACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Norman Lu As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C16H14F6N2O2, contains the smallest fluorinated group, viz. CF3. The molecule resides on a crystallographic inversion centre at the mid-point of the pyridine Cipso,Cipso bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C,H...N and C,H...O interactions are observed, similar to those in related polyfluorinated bpy,metal complexes. A ,,, interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C,H...N hydrogen bonding is present between one of the CF3CH2, methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl-type C,H...F interactions to atoms of the terminal CF3 group. It is of note that the O,CH2CF3 bond is almost perpendicular to the bpy plane. [source] 4-Methoxy-1-naphthol: chains formed by O,H...O hydrogen bonds and ,,, stacking interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Bernard Marciniak The structure of 4-methoxy-1-naphthol, C11H10O2, (I), contains an intermolecular O,H...O hydrogen bond which links the molecules into a simple C(2) chain running parallel to the shortest crystallographic b axis. This chain is reinforced by intermolecular ,,, stacking interactions. Comparisons are drawn between the crystal structure of (I) and those of several of its simple analogues, including 1-naphthol and some monosubstituted derivatives, and that of its isomer 7-methoxy-2-naphthol. This comparison shows a close similarity in the packing of the molecules of its simple analogues that form ,-stacks along the shortest crystallographic axes. A substantial spatial overlap is observed between adjacent molecules in such stacks. In this group of monosubstituted naphthols, the overlap depends mainly on the position of the substituents carried by the naphthalene moiety, and the extent of the overlap depends on the substituent type. By contrast with (I), in the crystal structure of the isomeric 7-methoxy-2-naphthol there are no O,H...O hydrogen bonds or ,,, stacking interactions, and sheets are formed by O,H..., and C,H..., interactions. [source] 5-Amino-1-naphthol: two-dimensional sheets built up from R44(18) rings formed by O,H...N, N,H...O and ,,, interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Ewa Rozycka-Sokolowska The crystal structure of the title compound, C10H9NO, (I), contains intermolecular O,H...N and N,H...O hydrogen bonds which together form sheets parallel to the (001) plane containing rings with an unusual R44(18) motif. These rings are additionally stabilized by an intermolecular ,,, stacking interaction. The significance of this study lies in the comparison drawn between the molecular structure of (I) and those of related compounds (1,5-diaminonaphthalene, 8-amino-2-naphthol, 3-amino-2-naphthol and aniline), which shows a close similarity in the noncoplanar orientation of the amine group and the aromatic moiety. Comparison of the crystal structures of (I) and several of its simple analogues (1-naphthol, naphthalene-1,4-diol, naphthalene-1,5-diol and 4-chloro-1-naphthol) shows a close similarity in the packing of the molecules, which form ,-stacks along the shortest crystallographic axes with a substantial spatial overlap between adjacent molecules. [source] 4-Chloro-1-naphtholACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Ewa Rozycka-Sokolowska Molecules of the title compound, C10H7ClO, (I), are connected by a single strong O,H...O hydrogen bond into a simple C(2) chain, which runs parallel to the c axis and is additionally stabilized by intermolecular ,,, stacking interactions. The significance of this study lies in the comparison drawn between the crystal structure of (I) and those of several of its simple analogues. This comparison shows a close similarity in the packing of the molecules that form ,-stacks along the shortest crystallographic axes. A substantial spatial overlap is observed between adjacent molecules in such a ,-stack, depending mainly on the kind of substituent. [source] Tetraaquabis(d -camphor-10-sulfonato)calcium(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009Dejan Jeremi The structure of the title compound, [Ca(C10H15O4S)2(H2O)4], is the first example in which two d -camphor-10-sulfonate anions are coordinated to a metal ion, in this case with direct Ca,O bonding. The molecule has crystallographically imposed twofold symmetry with the Ca atom on the twofold axis. Hydrogen bonds are formed between the coordinated water molecules and the O atoms of the SO3, groups of adjacent molecules, leading to the formation of a two-dimensional layered network. The compound displays sharp wavelength-selective transparency in the UV,visible spectrum, offering the potential for application as an optical filter. [source] Two crystal modifications of (Pro-Pro-Gly)4 -Hyp-Hyp-Gly-(Pro-Pro-Gly)4 reveal the puckering preference of Hyp(X) in the Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs in collagen helicesACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2010Kenji Okuyama Two crystal modifications of a collagen model peptide, (Pro-Pro-Gly)4 -Hyp-Hyp-Gly-(Pro-Pro-Gly)4 [where Hyp is (4R,2S)- l -hydroxyproline], showed very similar unit-cell parameters and belonged to the same space group P21. Both crystals exhibited pseudo-merohedral twinning. The main difference was in their molecular-packing arrangements. One modification showed pseudo-hexagonal packing, while the other showed pseudo-tetragonal packing. Despite their different packing arrangements, no significant differences were observed in the hydration states of these modifications. The peptide in the pseudo-tetragonal crystal showed a cyclic fluctuation of helical twists with a period of 20,Å, while that in the pseudo-hexagonal crystal did not. In these modifications, the puckering conformations of four of the 12 Hyp residues at the X position of the Hyp(X)-Hyp(Y)-Gly sequence were in the opposite conformations to the previous hypothesis that Hyp(X) residues involved in Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs prefer up-puckering and down-puckering conformations, respectively. Detailed investigation of the molecular interactions between Hyp(X) and adjacent molecules revealed that these opposite conformations appeared because the puckering conformation, which follows the hypothesis, is subject to steric hindrance from the adjacent molecule. [source] Determination of intermolecular distance for a model peptide of Bombyx mori silk fibroin, GAGAG, with rotational echo double resonanceBIOPOLYMERS, Issue 2 2002Tsunenori Kameda Abstract Rotational echo double resonance NMR spectroscopy is applied for the determination of the distance of intermolecular chains of pentapeptide, GAGAG (G: Gly, A: Ala), a model typical of the crystalline domain in Bombyx mori silk fibroin. 1:4 mixture of G[1- 13C]AGAG and GAG[15N]AG with antiparallel ,-sheet structure was used to determine the distance of intermolecular hydrogen bonding between adjacent molecules within pleated sheet and the 13C,15N interatomic distance was determined to be 4.3 Å. On the other hand, 1:4 mixture of GAG[1- 13C]AG and GAG[15N]AG gave information on the interpleated sheet arrangement. When we assumed the same distances between two interpleated sheets, the distance was calculated to be 5.3 Å and the angle 15N,13C,15N was 180°. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 80,85, 2002 [source] | ||||||||||