Pair Of Bridges Research Articles

English

A cDNA encoding a new putative serine protease, named Ssmase, was cloned and characterized from the venom gland of the centipede Scolopendra subspinipes mutilans. The cDNA sequence was 1029 bp length, including a 780 bp open reading frame (ORF), a 105 bp 5’ untranslated region, and a 144 bp 3’ untranslated region. The precursor nucleotide sequence of Ssmase was deduced to encode a prepro-peptide of 19 residues and a mature protein of 240 residues. The 19 amino acid residues prepro-peptide of Ssmase putatively composed of 14 amino acids of pre-peptide and 5 amino acids of propeptide (QGSSA). The mature protein of Ssmase contained the typical domain of a trypsin-like serine protease, where His61, Asp108 and Ser208 were the principal residues of the catalytic center. The cysteine residues at 46 to 62, 141 to 214, 180 to 195 and 204 to 233 possibly formed four pairs of disulfide bridges. Ssmase was found to have five N-glycosylation sites (N-Xaa-T/S). To the best of our knowledge, Ssmase was a trypsin-like serine protease firstly characterized from centipede venoms. Ssmase represented a new family of trypsin-like serine protease with four disulfide bridge motif.   Key words: Centipede, Scolopendra subspinipes mutilans, trypsin-like serine protease, cysteine motif.

Degradation versus Expansion of the AgX Frameworks: Formation of Oligomeric and Polymeric Silver Complexes from Reactions of Bulk AgX with N,N-Bis(diphenylphosphanylmethyl)-2-aminopyridine

Reactions of N,N-bis(diphenylphosphanylmethyl)-2-aminopyridine (bdppmapy) with [Ag(MeCN)4]ClO4 or AgX (X = Cl, Br, I, SCN, CN) afforded a family of oligomeric and polymeric complexes: [Ag2(MeOH)(bdppmapy)2](ClO4)2 (1), [AgCl(bdppmapy)] (2), [AgBr(bdppmapy)] (3), [AgI(bdppmapy)] (4), [AgSCN(bdppmapy)] (5), [{(η2-bdppmapy)Ag(μ-CN)AgCN}2(μ-bdppmapy)] (6), [Ag4(μ-CN)4(μ-bdppmapy)] (7), and [Ag2(μ-CN)(μ-bdppmapy)2][Ag5(μ-CN)6] (8). Compounds 1–8 were characterized by elemental analyses, IR spectra, 1H and 31P{1H} NMR, electrospray ionization (ESI) mass spectra, powder X-ray diffraction (XRD), and single-crystal X-ray diffraction. Compounds 1–3 and 5 hold a one-dimensional (1D) chain in which [Ag(MeOH)]+ or [AgX] motifs are linked by bdppmapy bridges. Compound 6 has a tetrameric framework in which two linear [(η2-bdppmapy)Ag(μ-CN)AgCN] fragments are connected by a μ-bdppmapy ligand. Compound 7 contains a 1D staircase chain in which two zigzag [Ag(μ-CN)]n chains are linked by pairs of μ-bdppmapy bridges. Compoun...

Synthesis, Crystal Structures and Fluorescence Properties of Two d10 Metal Coordination Polymers with Flexible Bis(benzimidazolyl)alkane Ligands

Two d10 metal coordination polymers with bis-benzimidazole ligands, [(Ag(L1))·NO3·4H2O]n (1) and [Cu2(L2)(CN)2]n (2) [L1 =1,4-bis(benzimidazol-1-yl)butane, L2 =1,4-bis(5,6-dimethylbenzimidazol- 1-yl)butane] have been synthesized hydrothermally and characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis and single-crystal X-ray diffraction. Compound 1 features a ribbon-like chain structure bridged by L1 ligands, and is ultimately extended into a 2D supramolecular network through two kinds of π-π stacking interactions. Compound 2 displays a (6,3) wave-like layer in which [Cu6(μ-CN)6(L2)2]n double chains are interconnected by pairs of L2 bridges. The fluorescence properties of the compounds in the solid state at room temperature were investigated.

Zinc coordination to the bapbpy ligand in homogeneous solutions and at liposomes: zinc detection via fluorescence enhancement

In this work, the complexation of the bapbpy ligand to zinc dichloride is described (bapbpy = 6,6′-bis(2-aminopyridyl)-2,2′-bipyridine). The water-soluble, colorless complex [Zn(bapbpy)Cl]Cl·2H2O (compound 2·H2O) was synthesized; its X-ray crystal structure shows a mononuclear, pentacoordinated geometry with one chloride ligand in apical position. Upon excitation of its lowest-energy absorption band (375 nm) compound 2 shows intense emission (Φ = 0.50) at 418 nm in aqueous solution, and an excited state lifetime of 5 ns at room temperature. Photophysical measurements, DFT, and TD-DFT calculations prove that emission arises from vibronically coupled Ligand-to-Ligand Charge Transfer singlet excited states, characterized by electron density flowing from the lone pairs of the non-coordinated NH bridges to the π* orbitals of the pyridine rings. Monofunctionalization of the ligand with one long alkyl chain was realized to afford ligand 3, which can be inserted into dimyristoylphosphatidylglycerol (DMPG) or dimyristoylphosphatidylcholine (DMPC) unilamellar vesicles. For negatively charged DMPG membranes the addition of a zinc salt to the vesicles leads to an enhancement of the fluorescence due to zinc coordination to the membrane-embedded tetrapyridyl ligand. No changes were observed for the zwitterionic DMPC lipids, where binding of the Zn ions does not take place. A modest binding constant was found (5 × 10(6) M(−1)) for the coordination of zinc cations to bapbpy-functionalized DMPG membranes, which allows for the detection of micromolar zinc concentrations in aqueous solution. The influence of chloride concentration and other transition metal ions on the zinc binding was evaluated, and the potential of liposome-supported metal chelators such as ligand 3 for zinc detection in biological media is discussed.

Design-driven quadrangulation of closed 3D curves

We propose a novel, design-driven, approach to quadrangulation of closed 3D curves created by sketch-based or other curve modeling systems. Unlike the multitude of approaches for quad-remeshing of existing surfaces, we rely solely on the input curves to both conceive and construct the quad-mesh of an artist imagined surface bounded by them. We observe that viewers complete the intended shape by envisioning a dense network of smooth, gradually changing, flow-lines that interpolates the input curves. Components of the network bridge pairs of input curve segments with similar orientation and shape. Our algorithm mimics this behavior. It first segments the input closed curves into pairs of matching segments, defining dominant flow line sequences across the surface. It then interpolates the input curves by a network of quadrilateral cycles whose iso-lines define the desired flow line network. We proceed to interpolate these networks with all-quad meshes that convey designer intent. We evaluate our results by showing convincing quadrangulations of complex and diverse curve networks with concave, non-planar cycles, and validate our approach by comparing our results to artist generated interpolating meshes.

Crystal Structure of TNF-α-Inducing Protein from Helicobacter Pylori in Active Form Reveals the Intrinsic Molecular Flexibility for Unique DNA-Binding

Tipα (TNF-α-inducing protein) from Helicobacter pylori is a carcinogenic effector. Studies on this protein revealed that a homodimer linked by a pair of intermolecular disulfide bridges (Cys25-Cys25 and Cys27-Cys27) was absolutely necessary for its biological functions. The activities of Tipα would be abolished when both disulfide bridges were disrupted. The crystal structures of Tipα reported to date, however, were based on inactive, monomeric mutants with their N-terminal, including residues Cys25 and Cys27, truncated. Here we report the crystal structure of H. pylori Tipα protein, TipαN25, at 2.2Å resolution, in which Cys25 and Cys27 form a pair of inter-chain disulfide bridges linking an active dimer. The disulfide bridges exhibit structural flexibility in the present structure. A series of structure-based mutagenesis, biochemical assays and molecular dynamic simulations on DNA-Tipα interactions reveal that Tipα utilizes the dimeric interface as the DNA-binding site and that residues His60, Arg77 and Arg81 located at the interface are crucial for DNA binding. Tipα could bind to one ssDNA, two ssDNA or one dsDNA in experiments, respectively, in the native or mutant states. The unique DNA-binding activities of Tipα indicate that the intrinsic flexible nature of disulfide bridges could endow certain elasticity to the Tipα dimer for its unique bioactivities. The results shed light on the possible structural mechanism for the functional performances of Tipα.

Structural Reduction Techniques for Logic-Chain Bridging Fault Diagnosis

This paper proposes four logic-chain bridging fault models, which involve one net in the combinational logic and the other net in the scan chain. Test results of logic-chain bridging faults, unlike existing scan chain fault models, depend on the previous scan inputs as well as primary inputs. A bridging pair extraction algorithm is proposed to quickly extract bridging pairs from the layout. The paper proposed two sets of structural reduction techniques so that runtime is very short. Experimental results on ISCAS benchmark circuits show that, on the average, logic-chain bridging faults can be diagnosed within an accuracy of four bridging pairs. The techniques are still applicable when there are only 10 failing patterns due to limited ATE failure memory. This paper demonstrates the feasibility to diagnose logic-chain bridging faults by software.

Catena-Poly[(diaquastrontium)-bis{μ-5-[4-(1H-imidazol-1-yl)phenyl]tetrazolido}

In the title complex polymer, [Sr(C10H7N6)2(H2O)2]n, the SrII atom lies on an inversion centre and is coordinated by four N atoms from two bidentate bridging trans-related 5-[4-(1H-imidazol-1-yl)phen­yl]tetra­zolide ligands [Sr—N = 2.387 (4) Å for the tetrazolide moiety and Sr—N = 2.273 (5) Å for the imidazole moiety], and by two O atoms from water mol­ecules [Sr—O = 2.464 (4) Å], giving a distorted octa­hedral coordination. Pairs of ligand bridges link the complex units, forming chains which extend along [111] and are inter-associated through Owater—H⋯N hydrogen bonds, giving a two-dimensional network structure parallel to (001). Weak π–π stacking inter­actions between the benzene and imidazole rings are also present [minimum ring centroid separation = 3.691 (4) Å].

Reactions of cadmium(ii) nitrate with 4-(trimethylammonio)benzenethiolate in the presence of N-donor ligands

Reactions of Cd(NO(3))(2)·4H(2)O with TabHPF(6) (TabH = 4-(trimethylammonio)benzenethiol) and Et(3)N in the presence of NH(4)SCN and five other N-donor ligands such as 2,2'-bipyridine (2,2'-bipy), phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (2,9-dmphen), 2,6-bis(pyrazd-3-yl)pyridine (bppy) and 2,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (bdmppy) gave rise to a family of Cd(II)/thiolate complexes of N-donor ligands, {[Cd(2)(μ-Tab)(4)(NCS)(2)](NO(3))(2)·MeOH}(n) (1), [Cd(2)(μ-Tab)(2)(L)(4)](PF(6))(4) (2: L = 2,2'-bipy; 3: L = phen), [Cd(Tab)(2)(L)](PF(6))(2) (4: L = 2,9-dmphen; 5: L = bppy), and [Cd(2)(μ-Tab)(2)(Tab)(2)(bdmppy)](2)(PF(6))(8)·H(2)O (6·H(2)O). These compounds were characterized by elemental analysis, IR spectra, UV-Vis spectra, (1)H NMR, electrospray ionization (ESI) mass spectra and single-crystal X-ray diffraction. For 1, each [Cd(NCS)](+) fragment is connected to its equivalents via a pair of Tab bridges to a one-dimensional chain. For 2 and 3, two [Cd(2,2'-bipy)(2)](2+) or [Cd(phen)(2)](2+) units are linked by a pair of Tab bridges to form a cationic dimeric structure. The Cd atom in [Cd(Tab)(2)(L)](2+) dication of 4 or 5 is coordinated by two Tab ligands and chelated by two N atoms from 2,9-dmphen (4) or three N atoms from bppy (5), forming a distorted tetrahedral (4) or trigonal bipyramidal (5) coordination geometry. For 6, each of two [Cd(Tab)(bdmppy)] fragments is linked to one [(Tab)Cd(μ-Tab)(2)Cd(Tab)] fragment via two Tab bridges to generate a unique cationic zigzag tetrameric structure where the Cd centers take a tetrahedral or a trigonal bipyramidal coordination geometry. The results may provide an interesting insight into mimicking the coordination spheres of the Cd(II) sites of metallothioneins and their interactions with various N-donor ligands encountered in nature.

Spacer length-controlled assembly of [CunIn]-based coordination polymers from CuI and bis(4-phenylpyrimidine-2-thio)alkane ligands

Reactions of CuI with bis(4-phenylpyrimidine-2-thio)alkane ligands with different spacer lengths, [(phpy)(CH2)n(phpy)] (phpyH = 4-phenylpyrimidine-2-thiol; n = 1, bphpym; n = 2, bphpye; n = 3, bphpypr; n = 4, bphpyb; n = 5, bphpyp; n = 6, bphpyh), afforded a set of six [CunIn]-based coordination polymers, [{Cu(μ3-I)}2(phpym)]n (1), [{Cu(μ3-I)}4(bphpye)]n (2), [{(MeCN)Cu3(μ-I)2(μ4-I)}2(bphpypr)2]n (3), [{((MeCN)Cu)(μ-I)}2(bphpyb)]n (4), [{Cu2(μ-I)(μ3-I)}2(bphpyp)2]n (5) and [{((MeCN)Cu)(μ3-I)}2{Cu(μ-I)}2(bphpyh)2]n (6), respectively. Compounds 1–6 were characterized by elemental analysis, IR and single-crystal X-ray crystallography. 1 and 2 consist of an unique 2D network in which the 1D staircase [Cu2I2]n chains are linked by phpym or phpye ligands via the μ-η1(N)-η1(N) or μ-η1(N),η1(S)-η1(N),η1(S) coordination modes, respectively. Complexes 3 and 5 consist of double butterfly-shaped {(MeCN)Cu3(μ-I)2(μ4-I)}2 units or chair-like [Cu2(μ-I)(μ3-I)]2 units that are linked to their neighboring ones by pairs of bphpypr or bphpyp bridges to form a 1D double chain. 4 contains a 1D zigzag chain assembled by dimeric [{(MeCN)Cu}(μ-I)]2 cores and bphpyb ligands. In 6, unique 1D tandem-rhomboid [Cu2I2]n chains are connected by dphpyh ligands to form a 2D staircase network. In addition, the photoluminescent properties of 1–6 in the solid state at ambient temperature were investigated.

Catena-Poly[[bis(1-ethyl-1H-imidazole-κN3)cadmium]-di-μ-chlorido-[(1-ethyl-1H-imidazole-κN3)cadmium]-di-μ-chlorido-[(1-ethyl-1H-imidazole-κN3)cadmium]-di-μ-chlorido-[bis(1-ethyl-1H-imidazole-κN3)cadmium

The asymmetric unit of the crystal structure of the title compound, [Cd2Cl4(C5H8N2)3]n, contains two CdII cations, three 1-ethyl-1H-imidazole ligands, and four Cl− anions. The two CdII atoms have quite different coordination environments: one is octa­hedrally coordinated by four Cl atoms and two N atoms from two 1-ethyl-1H-imidazole ligands, and the second is in a severely distorted fivefold coordination by four Cl atoms and one N atom from a 1-ethyl-1H-imidazole ligand. Adjacent CdII cations are inter­connected alternately by pairs of chloride bridges, generating an infinite step-like chain along the a axis. One ethyl group of the 1-ethyl-1H-imidazole ligand is disordered over two sets of sites with a 0.668 (13):0.332 (13) site-occupancy ratio.

Access to the Complement Factor B Scissile Bond Is Facilitated by Association of Factor B with C3b Protein

Factor B is a zymogen that carries the catalytic site of the complement alternative pathway C3 convertase. During convertase assembly, factor B associates with C3b and Mg(2+) forming a pro-convertase C3bB(Mg(2+)) that is cleaved at a single factor B site by factor D. In free factor B, a pair of salt bridges binds the Arg(234) side chain to Glu(446) and to Glu(207), forming a double latch structure that sequesters the scissile bond (between Arg(234) and Lys(235)) and minimizes its unproductive cleavage. It is unknown how the double latch is released in the pro-convertase. Here, we introduce single amino acid substitutions into factor B that preclude one or both of the Arg(234) salt bridges, and we examine their impact on several different pro-convertase complexes. Our results indicate that loss of the Arg(234)-Glu(446) salt bridge partially stabilizes C3bB(Mg(2+)). Loss of the Arg(234)-Glu(207) salt bridge has lesser effects. We propose that when factor B first associates with C3b, it bears two intact Arg(234) salt bridges. The complex rapidly dissociates unless the Arg(234)-Glu(446) salt bridge is released whereupon conformational changes occur that activate the metal ion-dependent adhesion site and partially stabilize the complex. The remaining salt bridge is then released, exposing the scissile bond and permitting factor D cleavage.

Specificity and cooperativity at β-lactamase position 104 in TEM-1/BLIP and SHV-1/BLIP interactions.

Establishing a quantitative understanding of the determinants of affinity in protein-protein interactions remains challenging. For example, TEM-1/β-lactamase inhibitor protein (BLIP) and SHV-1/BLIP are homologous β-lactamase/β-lactamase inhibitor protein complexes with disparate K(d) values (3 nM and 2 μM, respectively), and a single substitution, D104E in SHV-1, results in a 1000-fold enhancement in binding affinity. In TEM-1, E104 participates in a salt bridge with BLIP K74, whereas the corresponding SHV-1 D104 does not in the wild type SHV-1/BLIP co-structure. Here, we present a 1.6 Å crystal structure of the SHV-1 D104E/BLIP complex that demonstrates that this point mutation restores this salt bridge. Additionally, mutation of a neighboring residue, BLIP E73M, results in salt bridge formation between SHV-1 D104 and BLIP K74 and a 400-fold increase in binding affinity. To understand how this salt bridge contributes to complex affinity, the cooperativity between the E/K or D/K salt bridge pair and a neighboring hot spot residue (BLIP F142) was investigated using double mutant cycle analyses in the background of the E73M mutation. We find that BLIP F142 cooperatively stabilizes both interactions, illustrating how a single mutation at a hot spot position can drive large perturbations in interface stability and specificity through a cooperative interaction network.

Novel Zn and Cd coordination polymers of 1,1′-(1,6-hexanediyl)bis-1H-benzimidazole: solvothermal synthesis, crystal structures and photoluminescence properties

Solvothermal reactions of 1,1′-(1,6-hexanediyl)bis-1H-benzimidazole (hbbm) with Zn(II), or Cd(II) salts yielded six coordination polymers, [MX2(hbbm)]n (1: M = Zn, X = Cl; 2: M = Zn, X = Br), {[CdI2(hbbm)]·0.5H2O}n (3), [CdCl2(hbbm)2]n (4), [Cd3(η,μ-OAc)2(μ-OAc)2(OAc)2(hbbm)2]n (5), and [Zn2(μ-OAc)4(hbbm)]n (6). Compounds 1–6 were characterized by elemental analysis, IR, powder X-ray diffraction, and single crystal X-ray diffraction. Compounds 1–3 contain a 1D zigzag chain in which [MX2] units are linked by hbbm bridges. For 4, each [Cd4Cl8(hbbm)4] unit acting as a planar four-connecting node connects other four equivalent ones via eight hbbm molecules to form a 2D (4,4) network. For 5, each linear [Cd3(η,μ-OAc)2(μ-OAc)2(OAc)2] unit is linked by two pairs of hbbm bridges to afford a 1D double chain. For 6, each [Zn2(μ-OAc)4] unit is connected by hbbm bridges to form a 1D U-type chain, which further interweaves with other adjacent chains to form a unique 3D net. The solid state luminescent properties of 1–6 at ambient temperature were also investigated.

Assembly of bicyclic or monocyclic clusters from [(η5-C5Me5)2Mo2(μ3-S)4(CuMeCN)2]2+ with tetraphosphine or N,P mixed ligands: syntheses, structures and enhanced third-order NLO performances

Reactions of the preformed cluster [(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)(MeCN)(2)](ClO(4))(2) (1) with two tetraphosphine ligands, 1,4-N,N,N',N'-tetra(diphenylphosphanylmethyl)benzene diamine (dpppda) and N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda), produced two bicyclic clusters {[(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)](2)(L)}(ClO(4))(4) (3: L = dpppda; 4: L = dppeda). Analogous reactions of 1 or [(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)(MeCN)(2)](PF(6))(2) (2) with two N,P mixed ligands, N,N-bi(diphenylphosphanylmethyl)-2-aminopyridine (bdppmapy) and N-diphenylphosphanylmethyl-4-aminopyridine (dppmapy), afforded two monocyclic clusters {[(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)](2)(L)(2)}X(4) (5: L = bdppmapy, X = ClO(4); 6: L = dppmapy, X = PF(6)). Compounds 3-6 were fully characterized by elemental analysis, IR spectra, UV-vis spectra, (1)H and (31)P{(1)H} NMR spectra, ESI-MS and single-crystal X-ray crystallography. In the tetracations of 3-6, two cubane-like [Mo(2)(μ(3)-S)(4)Cu(2)] cores are linked either by one dpppda or dppeda bridge to form a bicyclic structure or by a pair of bdppmapy or dppmapy bridges to afford a monocyclic structure. The third-order nonlinear optical (NLO) properties of 1 and 3-6 in MeCN were also investigated by femtosecond degenerate four-wave mixing (DFWM) technique with a 50 fs pulse width at 800 nm. Compounds 3-6 exhibited enhanced third-order NLO performances relative to that of 1.

Construction of [Cu n I n ]-based coordination polymers via flexible benzimidazolyl-based ligands

Four new [Cu n I n ]-based coordination polymers, [{ Cu4(µ3-I)4(mbbm)2}·2DMF] n (1), [(CuI)2(mbbm)2] n (2), [{Cu2(µ-I)2-(ebbm)2}·2MeCN] n (3), and [Cu2(µ-I)2(prbbm)2] n (4), were prepared from solvothermal reactions of CuI with three flexible ligands [(bzim)(CH2) n (bzim)] (bzim = benzimidazole; n = 1, mbbm; n = 2, ebbm; n = 3, prbbm). These compounds were characterized by elemental analysis, IR and X-ray crystallography. 1 consists of cubanelike [Cu4(µ3-I)4] fragments that link the neighboring ones via mbbm bridges to form a 1D ladder-type chain. 2 contains mononuclear [CuI] fragments that are bridged by mbbm ligands to yield a 1D zigzag chain. 3 or 4 contains a [Cu2(µ-I)2] dimeric fragment, which works as a four-connecting node to link its four equivalent ones to form a 2D (4,4) network (3) or acts as a two-connecting node to connect its two equivalent ones via two pairs of prbbm bridges to form a 1D double chain (4). The photoluminescent properties of 1–4 in the solid state at ambient temperature were investigated.

Third Extracellular Loop (EC3)-N Terminus Interaction Is Important for Seven-transmembrane Domain Receptor Function: IMPLICATIONS FOR AN ACTIVATION MICROSWITCH REGION

The canonical heptahelical bundle architecture of seven-transmembrane domain (7TM) receptors is intertwined by three intra- and three extracellular loops, whose local conformations are important in receptor signaling. Many 7TM receptors contain a cysteine residue in the third extracellular loop (EC3) and a complementary cysteine residue on the N terminus. The functional role of such EC3-N terminus conserved cysteine pairs remains unclear. This study explores the role of the EC3-N terminus cysteine pairs on receptor conformation and G protein activation by disrupting them in the chemokine receptor CXCR4, while engineering a novel EC3-N terminus cysteine pair into the complement factor 5a receptor (C5aR), a chemo attractant receptor that lacks it. Mutated CXCR4 and C5aRs were expressed in engineered yeast. Mutation of the cysteine pair with the serine pair (C28S/C274S) in constitutively active mutant CXCR4 abrogated the receptor activation, whereas mutation with the aromatic pair (C28F-C274F) or the salt bridge pair (C28R/C274E), respectively, rescued or retained the receptor activation in response to CXCL12. In this context, the cysteine pair (Cys(30) and Cys(272)) engineered into the EC3-N terminus (Ser(30) and Ser(272)) of a novel constitutively active mutant of C5aR restrained the constitutive signaling without affecting the C5a-induced activation. Further mutational studies demonstrated a previously unappreciated role for Ser(272) on EC3 of C5aR and its interaction with the N terminus, thus defining a new microswitch region within the C5aR. Similar results were obtained with mutated CXCR4 and C5aRs expressed in COS-7 cells. These studies demonstrate a novel role of the EC3-N terminus cysteine pairs in G protein-coupled receptor activation and signaling.

Synthesis and Structural Properties of Heteroleptic Rare Earth Mixed Carboxylates with Well‐defined Solvation Spheres

AbstractMixed carboxylate complexes of cerium(III) and yttrium(III), [Ce2(OAc)4(salH)2(OH2)4]·4HOAc and [Y2(OAc)4(salH)2(OH2)4]·2H2sal (HOAc, H2sal ≡ acetic, salicylic acids) have been structurally characterized as tetrakis(acetic) and bis(salicylic) acid solvates, respectively. The dinuclear complex components take an identical form: [(OAc‐O,O′)(H2O)2Ln(O,μ‐O′‐OAc)2(O‐Hsal‐O′)2Ln(OH2)2(O,O′‐OAc)], with bridging pairs of acetate and salicylate ligands. The solvating acid molecules are closely and elegantly associated with the dinuclear complex via hydrogen bonding, these aggregates in turn being held together in the lattice by interactions between water molecule hydrogen atoms and neighboring carboxylate oxygen atoms.

5,8-Dibromo-2,11-dithia[3,3](2,6)pyridinoparacyclophane

The title compound, C15H13Br2NS2 [systematic name: 12,15-dibromo-2,7-dithia-1(1,4)-benzena-5(2,6)-pyridinaocta­phane], contains a dibromo-substituted benzene ring and a pyridine ring that are linked by a pair of bridging —CH2SCH2— groups. There is a weak π–π inter­action between the rings, the distance between the ring centroids being 3.572 (4) Å. The rings are not parallel, but form a dihedral angle of 18.29 (4)°.

Structural diversity of chlorido methoxido- and ethoxido-oxidovanadium(V) complexes: Two-dimensional network, dimer, and unusual syn-oriented V=O functionality

The syntheses and structural characterization of methoxido- and ethoxido-vanadium complexes [VOCl 2 (OMe)(HOMe) 2 ] ( 1 ), [VOCl(OMe) 2 ] 2 ( 2 ), and [{VOCl(OEt) 2 } 2 (THF)] ( 3 ) are described. The effects of the reactant ratio, starting materials, and reaction media on the formation of the alkoxido oxidovanadium and their molecular structures are reported. Complex 1 was prepared by reaction of VOCl 3 with three equiv of MeOH in pentane. In the solid state, each molecule of 1 is linked with four symmetry related molecules through four O–H···Cl interactions resulting in the formation of a 2D infinite network. Reaction of VOCl 3 with 2 equiv of NaOMe in pentane yields the dimeric complex 2 , which features a pair of methoxido bridges in the molecular structure. In THF, reaction of VOCl 3 with 2 equiv of NaOEt results in a very thermolabile [{VOCl(OEt) 2 } 2 (THF)] ( 3 ), which adopts a butterfly conformation in the molecular structure and features an interesting alkoxido oxidovandium with syn -orientated V=O functionality. Methoxido- and ethoxido-oxidovanadium(V) with different coordination geometry have been synthesized and characterized. Reaction of VOCl 3 with 2 equivalents of NaOEt in tetrahydrofuran affords a novel solvent coordinated complex [VOCl(OEt) 2 ] 2 (THF) ( 3 ) with the two V═O moieties syn- oriented in the solid state.