Interaction forces between salivary proteins and Streptococcus mutans with and without antigen I/II

The antigen I/II family of surface proteins is expressed by oral streptococci, including Streptococcus mutans, and mediates specific binding to, among others, salivary films. The aim of this study was to investigate the interaction forces between salivary proteins and S. mutans with (LT11) and without (IB03987) antigen I/II through atomic force microscopy (AFM) and to relate these interaction forces with the adhesion of the strains to saliva-coated glass in a parallel plate flow chamber. Upon approach of the bacteria toward a saliva-coated AFM tip, both strains experienced a similar repulsive force that was significantly smaller at pH 6.8 (median 3.0 and 3.1 nN for LT11 and IB03987, respectively) than at pH 5.8 (median 4.6 and 4.7 nN). The decay length of these repulsive forces was between 19 and 37 nm. Upon retraction at pH 6.8, the combined specific and nonspecific adhesion forces were significantly stronger for the parent strain LT11 (median -0.4 nN) than for the mutant strain IB03987 (median 0.0 nN), whereas at pH 5.8 the median of the adhesion forces measured was 0.0 nN for both strains. Moreover, at pH 6.8, the parent strain LT11 adhered in significantly higher numbers (9.6 x 106 cm-2) to a salivary coating than the mutant strain IB03987 (2.5 x 106 cm-2). Similar to the difference in adhesion forces between both strains at pH 5.8, the difference in adhesion between both strains also disappeared at pH 5.8, which suggests the involvement of attractive electrostatic forces in the interaction between antigen I/II and salivary coatings. In summary, this study shows that antigen I/II at the surface of S. mutans LT11 is responsible for its increased adhesion to salivary coatings under flow through an additional attractive electrostatic force.     

Screening and characterization of medicinal plants extracts with bactericidal activity against Streptococcus mutans

Abstract

The aim of the present study was to perform a screening of extracts obtained from 15 medicinal plants using water (at 25 and 90?°C) or ethanol (at 25?°C), to bactericidal activity against cariogenic S. mutans ATCC 25175, as well as to carry out the preliminary phytochemical characterization of the extracts and HPLC/MS assay for selected extracts. The extractions were carried out for 5?h at 400?rpm. Only five from 45 tested extracts were selected based on their antibacterial activity. The IC₅₀ varied from of 28?ppm for Quercus ilex up to 250?ppm for Jatropha dioica. Different polyphenolic and quinic acids, flavonoids, anthocyanin or tyrosol were identified by HPLC/MS in selected extracts from Rosa gallica L., Jatropha dioica Sessé, Mimosa tenuiflora (Willd.) Poir, Quercus ilex L., and Solanum nigrum. The obtained results confirm that selected extracts are good candidates to be used for cariogenic bacteria control.     

Determination of Fe(II), Cu(II) and Ag(I) by using silica gel loaded with 1,10-phenanthroline

The modified silica gel with 1,10-phenanthroline adsorbed was obtained. The adsorption from aqueous solutions onto loaded silica gel of Fe(II), Cu(II) and Ag(I) and their complexes was studied. The loaded silica gel was applied to Fe(II), Cu(II) and Ag(I) reflectance spectroscopy determinations in water (detection limits 0.08, 0.03 and 0.01 ppm respectively). Visual test scales for Fe, Cu and Ag ion determinations in water were worked out.     

Crystal structure and interaction with bovine serum albumin of the Cu(I/II) complex [C20H32Cu2I3N4] n

[C₂₀H₃₂Cu₂I₃N₄] _n was synthesized and characterized by elemental analysis, ESI-MS spectrometry, and IR spectra. The crystal structure was determined by X-ray single-crystal diffraction. The binding of the complex with bovine serum albumin (BSA) was studied by fluorescence spectroscopy under simulated physiological conditions. The binding constant (K _b), the number of binding sites (n), and the corresponding thermodynamic parameters ΔH, ΔS, ΔG were calculated based on the van’t Hoff equation. The complex had strong ability to quench the fluorescence from BSA, and the quenching mechanism of this complex to BSA was static quenching. Hydrogen bonds and van der Waals forces are the interactions between the Cu(I/II) complex and BSA. According to the Förster non-radiation energy transfer theory, the binding average distance between the donor (BSA) and the acceptor (Cu(I/II) complex) was obtained. The effect of the complex on the BSA conformation was also studied by using synchronous fluorescence spectroscopy.     

系列Cu(Ⅱ/Ⅰ)配聚物的合成、结构及光电性能

采用水热方法合成了3种Cu(Ⅱ/Ⅰ)配聚物及超分子, (1) [K₂Cu₂(ox)(btec)(MeOH)₂]_n, (2) {[Cu(pdc)(H₂O)₂]?H₂O}_n, (3) [Cu(cyan)(phen)]?H₂O (H₂ox: 草酸, H₄btec: 均苯四甲酸, MeOH: 甲醇, H₂pdc: 2, 5-吡啶二羧酸, phen: 邻菲啰啉, Hcyan: 氰尿酸). 通过X射线单晶衍射、表面光电压光谱(SPS)、固体紫外-可见(UV-Vis)、傅里叶变换红外(FTIR)光谱、元素分析等方法对配合物进行了表征. 结构解析结果表明, 配合物(1)是具有三维(3D)无限结构的配聚物; (2)是具有二维(2D)无限结构的配聚物, 但又通过氢键进一步连成了三维(3D)网络, (1)与(2)的中心金属均为Cu(II)离子; (3)为含Cu(I)的单核配合物, 但又通过氢键和π-π堆积作用, 使它成为2D超分子化合物. 配合物SPS结果显示, 配合物(1)-(3)在300-800 nm范围内都呈现光伏响应, 表明三者均具有一定的光电转换能力. 讨论了配合物的组成、结构、维数、配体种类、中心金属离子价态及配位微环境对SPS的影响,并将SPS与UV-Vis 光谱进行了关联.     

On the use of edge cracked short bend beam specimen for PMMA fracture toughness testing under mixed-mode I/II

In this paper an inclined edge cracked short beam specimen subjected to symmetric three-point bend loading was designed and examined for conducting mixed-mode I/II fracture toughness experiments. The aspect ratio (i.e. length to width ratio) and the loading span distance are considered much lower than the other conventional cracked bend beam samples. Crack tip parameters such as stress intensity factors and T-stress were computed numerically for this specimen by several finite element analyses and it was demonstrated that the specimen is able to produce full combinations of mode I and II including pure mode II. The practical capability of the short bend beam specimen was studied experimentally by conducting a set of mixed-mode fracture tests on PolymethylMethacrylate (PMMA) as a well-known model brittle material. The critical stress intensity factors, the direction of fracture kinking and the path of fracture trajectory were investigated both experimentally and theoretically using two stress and strain-based fracture criteria. The fracture toughness of tested PMMA was decreased by moving towards mode II case due to the effect of T-stress on the fracture mechanism of the short bend beam specimen.     

Combined Experimental and Theoretical Study on the Reactivity of Compounds I and II in Horseradish Peroxidase Biomimetics

For the exploration of the intrinsic reactivity of two key active species in the catalytic cycle of horseradish peroxidase (HRP), Compound I (HRP‐I) and Compound II (HRP‐II), we generated in situ [Fe^IV?O(TMP^+.)(2‐MeIm)]⁺ and [Fe^IV?O(TMP)(2‐MeIm)]⁰ (TMP=5,10,15,20‐tetramesitylporphyrin; 2‐MeIm=2‐methylimidazole) as biomimetics for HRP‐I and HRP‐II, respectively. Their catalytic activities in epoxidation, hydrogen abstraction, and heteroatom oxidation reactions were studied in acetonitrile at ?15 °C by utilizing rapid‐scan UV/Vis spectroscopy. Comparison of the second‐order rate constants measured for the direct reactions of the HRP‐I and HRP‐II mimics with the selected substrates clearly confirmed the outstanding oxidizing capability of the HRP‐I mimic, which is significantly higher than that of HRP‐II. The experimental study was supported by computational modeling (DFT calculations) of the oxidation mechanism of the selected substrates with the involvement of quartet and doublet HRP‐I mimics (^2,4Cpd I) and the closed‐shell triplet spin HRP‐II model (³Cpd II) as oxidizing species. The significantly lower activation barriers calculated for the oxidation systems involving ^2,4Cpd I than those found for ³Cpd II are in line with the much higher oxidizing efficiency of the HRP‐I mimic proven in the experimental part of the study. In addition, the DFT calculations show that all three reaction types catalyzed by HRP‐I occur on the doublet spin surface in an effectively concerted manner, whereas these reactions may proceed in a stepwise mechanism with the HRP‐II mimic as oxidant. However, the high desaturation or oxygen rebound barriers during C?H bond activation processes by the HRP‐II mimic predict a sufficient lifetime for the substrate radical formed through hydrogen abstraction. Thus, the theoretical calculations suggest that the dissociation of the substrate radical may be a more favorable pathway than desaturation or oxygen rebound processes. Importantly, depending on the electronic nature of the oxidizing species, that is, ^2,4Cpd I or ³Cpd II, an interesting region‐selective conversion phenomenon between sulfoxidation and H‐atom abstraction was revealed in the course of the oxidation reaction of dimethylsulfide. The combined experimental and theoretical study on the elucidation of the intrinsic reactivity patterns of the HRP‐I and HRP‐II mimics provides a valuable tool for evaluating the particular role of the HRP active species in biological systems.     

Comparative structural study of the complexation behaviour of silver(I), cadmium(II), mercury(II), and palladium(II) with a 17-membered N3O2-donor macrocycle

A comparative investigation of the coordination behaviour of the 17-membered, N₃O₂-donor macrocycle, 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane, L, with the soft metal ions Ag(I), Cd(II), Hg(II), and Pd(II) is reported. The X-ray structures of 12 complexes have been determined and a range of structural types, including both mononuclear and dinuclear species, shown to occur. In particular cases the effect of anion variation on the resulting structures has been investigated; L reacts with AgX (X = NO₃, ClO₄, PF₆, OTf and CN) to yield related 2:2 (metal:ligand) complexes of types [Ag₂L₂(NO₃)₂] (1), [Ag₂L₂](ClO₄)₂ · 2DMF (2), [Ag₂L₂](PF₆)₂ · 2DMF (3), [Ag₂L₂](OTf)₂ (4) and [Ag₂L₂(μ-CN)][Ag(CN)₂] · H₂O (5). In all five complexes the ether oxygens of each ring are unbound. In 1–4 the macrocycles are present in sandwich-like arrangements that shield the dinuclear silver centres, with each silver bonded to two nitrogen donors from one L and one nitrogen from a second L. A Ag···Ag contact is present between each metal centre such that both centres can be described as showing distorted tetrahedral geometries. In the case of 5 a rare single μ₂-κC:κC symmetrically bridging two-electron-donating cyano bridge links silver ions [Ag···Ag distance, 2.7437(10) Å]; the macrocyclic ligands are orientated away from the dinuclear metal centres. In contrast to the behaviour of silver, reaction of cadmium(II) perchlorate with L resulted in a mononuclear sandwich-like complex of type [CdL₂](ClO₄)₂ · CH₃CN (6). Again, the ether oxygens do not coordinate, with each L binding to the cadmium centre only via its three nitrogen donors in a facial arrangement such that a distorted octahedral coordination geometry is attained. Reaction of L with HgX₂ (X = ClO₄, SCN and I) yielded the monomeric species [HgL(ClO₄)₂] (7), [HgL(SCN)₂]·CH₃CN (8) and [Hg₂L₂](HgI₄)₂ · 2L (9), in which all five donors of L are bound to the respective mercury centres. However, reaction of L with Hg(NO₃)₂ in dichloromethane/methanol gave a mononuclear sandwich-like complex [HgL₂](NO₃)₂ · 2CH₃OH (10) without anion coordination. Reaction of K₂PdCl₄ and Pd(NO₃)₂ with L yielded the 1:1 complexes [PdLCl]Cl · H₂O (11) and [PdL(NO₃)]NO₃ · CH₃OH (12), respectively, in which the metal is bound to three nitrogen donors from L along with the corresponding chloride or nitrate anion. Each palladium adopts a distorted square-planar coordination geometry; once again the ether oxygens are not coordinated.     

Highly controlling selectivity of copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) between sulfonyl azids and normal alkynes or propynoates

In this article, a combination of Cu(OAc)₂·H₂O/2-aminophenol was developed as a highly efficient and controlling catalytic system for sulfonyl azids involved CuAAC. By using this catalytic system, sulfonyl azids reacted with normal alkynes or propynoates to selectively give the ring products or the chain products, respectively, in excellent yields within minutes. HOAc in situ produced in the reaction has been proved to be a super protonation reagent, by which the unstable intermediate 5-cuprated 1,2,3-triazole was protonated efficiently to yield ring-product 1-sulfonyl 1,2,3-trizoles. The control experiments also proved that 2-aminophenol played dual roles as both ligand and reductant, which led to the cheap and chemically stable Cu(OAc)₂·H₂O being an efficient copper source for our purpose.     

Relationship between the Auger parameter and the ground state valence charge of the core-ionized atom: The case of Cu(I) and Cu (II) compounds

We develop a simple semiempirical model that correlates the Auger parameter to the ground state valence charge of the core-ionized atom with closed shell electron configuration. Until now, the Auger parameter was employed to separate initial and final state effects that influence the core electron binding energy. The model is applied to Cu(I) and Cu (II) compounds with the Auger parameter defined as α' = E_b^FL (2p_3/2) + E_k^FL (L₃M₄₅M₄₅;¹G). The Auger parameter shift for Cu(I) ion in CuI, CuBr, CuFeS₂, Cu₂S, and Cu₂O compounds—with respect to the copper free atom—increases with the electronic polarizability of the nearest-neighbour ligands suggesting a nonlocal screening mechanism. This relaxation process is interpreted as due to an electron transfer from the nearest-neighbour ligands toward the spatially extended 4sp valence orbitals of the core-ionized Cu(I) ion. In agreement with our model, a linear relationship is found between the Auger parameter shift and the ground state Bader valence charge obtained by density functional theory calculations. The Auger parameter shift for the Cu (II) ion in CuF₂, CuCl₂, CuBr₂, CuSO₄, Cu (NO₃)₂•3H₂O, Cu₃(PO₄)₂, Cu (OH)₂, and CuO compounds is very close to the Auger parameter of metallic copper, and therefore, it is not related to the calculated ground state Bader valence charge. The relaxation process in the final state is dominated by the local screening mechanism, which involves an electron transfer from the nearest-neighbour ligands toward the spatially contracted 3d orbitals of the core-ionized Cu (II) ion.     

Simulating the active sites of copper-trafficking proteins. Density functional structural and spectroscopy studies on copper(I) complexes with thiols,carboxylato, amide and phenol ligands

A series of mononuclear binary and ternary Cu(I) complexes with formato, formamide, methylphenol, and methanethiolato ligands were optimized at DFT-B3LYP/6-31G** (BS1) and DFT-B3LYP/6-311++G** (BS2) levels of theory. The solvent effect was taken into account via PCM method (BS1W and BS2W, respectively). The coordination arrangement for [Cu^I(SCH₃/S(H)CH₃)(OOCH)]^?/0 and [Cu^I(SCH₃/S(H)CH₃)(O(H)(C₆H₄)CH₃)]^0/+ was pseudo-linear and for [Cu^I(SCH₃/S(H)CH₃)(OOCH)(OC(H)NH₂)]^?/0 was pseudo-trigonal. The [Cu^I(S-S(H)CH₃/Cu^I(S-SCH₃)]^+/0 link even to amide carbonyl and to general O(H)R residues (R=C₆H₅CH₃). [Cu^I(SCH₃)₂(O(H)(C₆H₄)CH₃)]^? went towards dissociation of the O(H)(C₆H₄)CH₃ ligand, whereas [Cu^I(S(H)CH₃)₂(O(H)(C₆H₄)CH₃)]⁺ converged nicely, maintaining the hydroxy function linked to the metal. The trends of total electronic energies seemed to be significant, suggesting that linear Cu^IS₂ coordination is more suitable than Cu^IS, Cu^IS₃ and Cu^IS₄ arrangements. The formation energies of [Cu^I(S(H)CH₃/SCH₃)(OOCH)]^0/?1 were higher than those of [Cu^I(S(H)CH₃/SCH₃)₂]^+/? on starting from [Cu^I(S(H)CH₃/Cu^I(SCH₃)]^+/0 by ca. 11–9 kcal mol^?1 (BS2W). The structural arrangements, bond distances, and angles as well as computed spectroscopic parameters resulted in good agreement with experimental data for corresponding synthetic complexes and with metal site regions of several copper(I)-proteins. These data help in interpreting structural data of complex biological systems and in constructing reliable force fields for molecular mechanics computations.     

Synthesis,crystal structure,stability studies,DNA/albumin interactions,and antimicrobial activities of two Cu(II) complexes with amino acids and 5-nitro-1,10-phenanthroline

One-dimensional (1-D) coordination polymer and mononuclear copper(II) complexes, ([Cu(nphen)(asn)]ClO₄)_n (1) and [Cu(nphen)(gln)(H₂O)]ClO₄·H₂O (2) (nphen = 5-nitro-110-phenanthroline, asn = asparagine, gln = glutamine), have been synthesized and characterized by IR spectroscopy, ESI-MS, CHN analysis, and single-crystal X-ray diffraction. These binary and ternary complexes of copper(II) with nphen, asn, and gln have been investigated using potentiometric methods in 0.1 M KCl aqueous ionic media at 298.2 K. The protonation constants of the ligands and the stability constants of 1 and 2 have been calculated from the potentiometric data using the “BEST” software package. The potentiometric results have been analyzed using the “SPE” software package, and the distribution curves for the copper-containing species have been determined for the ternary systems. The CT-DNA-binding properties of these complexes have been investigated by thermal denaturation measurements and both absorption and emission spectroscopy. Further, the interaction of these complexes with bovine serum albumin (BSA) and human serum albumin (HSA) has been investigated using absorption and emission spectroscopy. The thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were calculated by the van’t Hoff equation and discussed. The distances between the serum albumins and 1 and 2 have been obtained according to fluorescence resonance energy transfer (FRET). Conformational changes of serum albumins have been observed from synchronous fluorescence technique. The antimicrobial activity of the complexes has also been tested on some bacteria. The effect of different amino acids on the copper(II) complexes are discussed.     

Hydrothermal synthesis and structure of the first tin(II) squarate Sn2O(C4O4)(H2O)—comparison with Sn2[Sn2O2F4]

A tin(II) squarate Sn₂O(C₄O₄)(H₂O) was synthesized by hydrothermal technique. It crystallizes in the monoclinic system, space group C2/m (no. 12) with lattice parameters a=12.7380(9) Å, b=7.9000(3) Å, c=8.3490(5) Å, β=121.975(3)°, V=712.69(7) Å³, Z=4. The crystal structure determined with an R=0.042 factor, consists of [(Sn₄O₁₀)(H₂O)₂] units connected from one another in the [101] and [010] directions via squarate groups to form layers separated by Sn(II) lone pairs. This compound presents the same remarkable structural arrangement as observed in the tin-oxo-fluoride Sn₂[Sn₂O₂F₄] inorganic compound with Sn(II) lone pairs E(1) and E(2) concentrated in large rectangular-shape tunnels running along [001] direction.     

Molecular Mechanics Calculations on Chelates of Titanium(IV), Vanadium(IV/V), Copper(II), Nickel(II), Molybdenum(IV/V), Rhenium(IV/V) and Tin(IV) with Di- and Tridentate Ligands Using the New Extensible Systematic Force Field (ESFF)—An Empirical Study

Force field calculations were performed on a series of 27 transition metal complexes of titanium(IV), vanadium(IV/V), copper(II), nickel(II), molybdenum(IV/V), rhenium(IV/V), and tin(IV) with a broad variety of di- or tridentate ligands in order to find a reliable scheme for determining the molecular structure of such chelates with the new Extensible Systematic Force Field (ESFF). A good agreement between theoretical results and experimental data was achieved. In some cases an unspecific fitting of the force field was necessary.     

Metal complexes with N-(trifluoromethylbenzyl)iminodiacetate chelators (x-3F ligands). Part I. Copper(II) chelates of p-3F,m-3F,and o-3F with or without imidazole-like ligands

Eight Cu(II) complexes with N-(p-, m- or o-trifluoromethylbenzyl)iminodiacetate chelators (x-3F ligands) have been synthesized to promote C–F/H interligand interactions involving the F₃C-group: {[Cu(μ₂-p-3F)(H₂O)]·3H₂O]}_n (1), [Cu(m-3F)(H₂O)₂] (2), [Cu(p-3F)(Him)(H₂O)] (3), [Cu(m-3F)(Him)(H₂O)] (4), [Cu(o-3F)(Him)(H₂O)] (5), [Cu₂(p-3F)₂(H5Meim)₂(H₂O)₂] (6), [Cu(m-3F)(H5Meim)(H₂O)] (7), and [Cu(o-3F)(H5Meim)(H₂O)] (8) [Him and H5Meim = imidazole and the “remote” tautomer 5-methylimidazole, respectively]. The compounds were studied by single-crystal X-ray diffraction, FT-IR, electronic spectra and coupled thermogravimetric + FT-IR methods. The conformation of the iminodiacetate chelating moiety (IDA group) is fac-NO + O(apical) in 1 and mer-NO₂ in 2–8. The fac-IDA conformation observed in 1 is related to its polymeric structure and the coordination of a O’-carboxylate donor, from an adjacent complex unit, trans to the Cu–N(IDA) bond. The mer-IDA conformation in 2 is in agreement with similar compounds with an aqua ligand trans to the corresponding Cu–N(IDA) bond. As expected, the ternary complexes 3–8 feature a mer-IDA conformation. Some of the studied complexes exhibit disorder in the –CF₃ group and C–H?F interligand interactions along with conventional N–H?O and O–H?O interactions. The thermal decomposition of all studied compounds under air flow produces variable amounts of trifluorotoluene.     

Polymerization of 2‐pentene with Ni(II) α‐diimine complex/M‐MAO catalyst and structure of the polymer

Polymerization of 2‐pentene with [ArN?C(An)C(An)·NAr)NiBr₂ (Ar?2,6‐iPr₂C₆H₃)] ( 1‐Ni) /M‐MAO catalyst was investigated. A reactivity between trans‐2‐pentene and cis‐2‐pentene on the polymerization was quite different, and trans‐2‐pentene polymerized with 1‐Ni /M‐MAO catalyst to give a high molecular weight polymer. On the other hand, the polymerization of cis‐2‐butene with 1‐Ni /M‐MAO catalyst did not give any polymeric products. In the polymerization of mixture of trans‐ and cis‐2‐pentene with 1‐Ni /M‐MAO catalyst, the M_n of the polymer increased with an increase of the polymer yields. However, the relationship between polymer yield and the M_n of the polymer did not give a strict straight line, and the M_w/M_n also increased with increasing polymer yield. This suggests that side reactions were induced during the polymerization. The structures of the polymer obtained from the polymerization of 2‐ pentene with 1‐Ni /M‐MAO catalyst consists of ? CH₂? CH₂? CH(CH₂CH₃)? , ? CH₂? CH₂? CH₂? CH(CH₃)? , ? CH₂? CH(CH₂CH₂CH₃)? , and methylene sequence ? (CH₂)_n? (n ≥ 5) units, which is related to the chain walking mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2858–2863, 2008     

Proteomic analysis of cellular soluble proteins from human bronchial smooth muscle cells by combining nondenaturing micro 2DE and quantitative LC‐MS/MS. 2. Similarity search between protein maps for the analysis of protein complexes

Human bronchial smooth muscle cell soluble proteins were analyzed by a combined method of nondenaturing micro 2DE, grid gel‐cutting, and quantitative LC‐MS/MS and a native protein map was prepared for each of the identified 4323 proteins [1]. A method to evaluate the degree of similarity between the protein maps was developed since we expected the proteins comprising a protein complex would be separated together under nondenaturing conditions. The following procedure was employed using Excel macros; (i) maps that have three or more squares with protein quantity data were selected (2328 maps), (ii) within each map, the quantity values of the squares were normalized setting the highest value to be 1.0, (iii) in comparing a map with another map, the smaller normalized quantity in two corresponding squares was taken and summed throughout the map to give an “overlap score,” (iv) each map was compared against all the 2328 maps and the largest overlap score, obtained when a map was compared with itself, was set to be 1.0 thus providing 2328 “overlap factors,” (v) step (iv) was repeated for all maps providing 2328 × 2328 matrix of overlap factors. From the matrix, protein pairs that showed overlap factors above 0.65 from both protein sides were selected (431 protein pairs). Each protein pair was searched in a database (UniProtKB) on complex formation and 301 protein pairs, which comprise 35 protein complexes, were found to be documented. These results demonstrated that native protein maps and their similarity search would enable simultaneous analysis of multiple protein complexes in cells.     

Synthesis and characterization of mercury(II) complexes with 2-styryl-1,3-benzothiazole (sb). Presence of two differently coordinated Hg(II) ions in the dinuclear complex Hg2Cl4(sb)3. Structural characterization of 2-styryl-1,3-benzothiazole and some of its derivatives

The molecular and crystal structures of the following compounds 2-styryl-1,3-benzothiazole, sb, (1), Hg₂Cl₄(sb)₃ (2), 1,3-bis(1,3-benzothiazol-2-yl)-2,4-diphenylcyclobutane (3) 1,3-bis(1,3-benzothiazol-2-yl)-2,4-bis(4-chlorophenyl)cyclobutane (4) and HgBr₂(sb)₂ (5) were determined by single-crystal X-ray diffractometry. The crystal structure of 1 consists of discrete sb molecules which are essentially planar. The dimeric molecules of 3 and 4 are characterized by a cyclobutane ring. In both isolated complexes 2 and 5, sb acts as a neutral monodentate ligand coordinated to the mercury atom through the thiazolyl nitrogen atom. The dinuclear complex 2 is characterized by the unique example of two differently coordinated Hg(II) ions bridged via a non-symmetrical linear Cl⁻ bridge. The first one is coordinated by one terminal and one bridging Cl⁻ ion and two thiazolyl nitrogen atoms in the form of distorted tetrahedron. The second one is bonded to two terminal Cl⁻ ions and the bridging Cl⁻ ion and one thiazolyl nitrogen atom in a 2+2 manner. In complex 5 the Hg(II) ion, which is situated on a crystallographic twofold axis, is tetrahedrally coordinated by two Br⁻ ions and two thiazolyl nitrogen atoms. Both complexes are characterized by stronger mercury-to-halide covalent bonds than mercury-to-nitrogen bonds, which are regarded as contacts shorter than the van der Waals radii sum of the corresponding atoms. The geometry of the sb ligand in both complexes 2 and 5 has not been changed remarkably from that one in the uncoordinated state due to not so strong bonds formation with the Hg(II) ion.