bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Conformational Studies of a Chiral Octadentate Ligand Derived from (R)‐1,1′‐Binaphthyl‐2,2′‐diamine and its Dinuclear Zinc(II) and Nickel(II) Complexes
Authors: Mimmi Maria Chiara , Gullotti Michele , Santagostini Laura , Pagliarin Roberto , De Gioia Luca , Monzani Enrico , Casella Luigi 
Published: October 2003

AbstractThe synthesis of the octadentate ligand (R)‐(−)‐N,N′‐dimethyl‐N,N′‐bis{3‐[bis(1‐methyl‐2‐benzimidazolylmethyl)]aminopropyl}‐1,1′‐binaphthyl‐2,2′‐diamine (L), containing a central 1,1′‐binaphthalenediamine core connected to two aminobis(benzimidazole) arms by flexible trimethylene carbon chains, and its dinuclear complexes [Zn2L](ClO4)4 and [Ni2L](ClO4)4 is reported. The structural features of the free ligand and the metal complexes have been investigated by NMR, UV/Visible, CD, and computational methods, including simulated annealing‐molecular mechanics and semiempirical PM3 calculations. The preferred conformation of the free ligand is characterized by a relatively small dihedral angle of about 75° between the two naphthyl rings, which is imposed by favorable stacking interactions between benzimidazole rings from different arms. In the dinuclear zinc(II) complex each metal ion is pseudotetrahedral and bound to three N donors of one aminobis(benzimidazole) arm and one N donor of the binaphthalenediamine residue. Coordination of the benzimidazole groups to the metal ions prevents the stacking interactions seen in the free ligand and, consequently, the dihedral angle between the naphthyl groups increases to the more usual ca. 90°. In the dinuclear nickel(II) complex, the ligand still provides four nitrogen donors to each metal centers, but the stereochemical preference of the nickel(II) ions imposes a ligand field of tetragonal symmetry, with pseudo‐octahedral metal centers, and this occurs with pronounced flattening of the dihedral angle between the naphthyl groups. The change in conformation, from L to [Zn2L]4+ to [Ni2L]4+, of the critical 1,1′‐binaphthalenediamine residue is clearly indicated by CD spectra. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Mono‐ and Dinuclear Complexes of a Flexible Schiff Base Ligand − Crystal Structures of a Bishelicate and Two Acentric Monohelicates
Authors: Sanmartín Jesús , García‐Deibe Ana M. , Bermejo Manuel R. , Novio Fernando , Navarro Debora , Fondo Matilde 
Published: October 2003

AbstractNeutral NiII, PdII, CuII, AgI, ZnII, CdII, and PbII complexes of N,N′‐bis(2‐tosylaminobenzylidene)‐1,4‐diaminobutane (H2SB) have been prepared. The Schiff base seems to exist in a helically coiled state around nickel, copper and zinc ions, but not in Pd(SB)·3H2O·MeCN, Ag2(SB)·2H2O, Cd(SB)·3H2O, and Pb(SB)·3H2O, the metal ions of which seem to show planar geometries. The determination of the absolute structures of Cu(SB)·MeCN and Zn(SB)·2MeCN, which crystallise as non‐centrosymmetric racemic compounds, shows that these metal(II) ions assume distorted tetrahedral coordination geometries involving the four N atoms of the dianionic ligand. X‐ray structural characterisation also shows that this ligand behaves as a N2+N2 donor in the [4+4] bishelicate Ni2(SB)2·5MeCN. Secondary interactions between metal centres and one of the O atoms of each tosyl group are detected in these three crystal structures, being especially intense in the dimeric one. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Dioxomolybdenum(VI)‐Modified Mesoporous MCM‐41 and MCM‐48 Materials for the Catalytic Epoxidation of Olefins
Authors: Nunes Carla D. , Pillinger Martyn , Valente Anabela A. , Rocha João , Lopes André D. , Gonçalves Isabel S. 
Published: October 2003

AbstractThe dioxomolybdenum(VI) complex [MoO2Cl2(L‐L)], containing the bidentate 1,4‐diazabutadiene ligand RN=C(Ph)−C(Ph)=NR [R = (CH2)3Si(OEt)3], was immobilised in the ordered mesoporous silica MCM‐41 by carrying out a grafting reaction in dichloromethane. The grafted material (3.3 wt.‐% Mo) was tested as a catalyst for the epoxidation of cyclooctene with tert‐butyl hydroperoxide (TBHP) at 55 °C. Selectivity to the epoxide was very high and the observed kinetic profile was similar to that of the complex [MoO2Cl2(L‐L)] in the homogeneous phase. On recycling several times, some activity was lost from the first to second runs, but thereafter stabilised. Tethered complexes of this type were also prepared by a stepwise approach. The mesoporous silicas MCM‐41 and MCM‐48 were first treated with a toluene solution of the ligand L‐L under reflux. Before isolating the grafted materials, the silylating agent Me3SiCl was added to remove the residual Si−OH groups on the surface of the mesoporous materials. Oxomolybdenum species were subsequently introduced into the ligand‐silicas by pore volume impregnation of a solution of the complex [MoO2Cl2(THF)2] in CH2Cl2 at room temperature. The modified materials have been characterised by powder X‐ray diffraction, N2 adsorption, and solid‐state MAS NMR (13C, 29Si). Despite having lower metal loadings (1 wt.‐% Mo), the materials exhibited similar catalytic activities for the epoxidation of cyclooctene to that of the modified MCM‐41 with 3.3 wt.‐% of Mo. However, selectivities to the epoxide were lower. The MCM supported catalysts have also been tested for the epoxidation of cyclododecene and α‐pinene with TBHP. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Characterisation of New Nickel‐Iron Complexes with an S4 Coordination Environment around the Nickel Centre
Authors: Verhagen Johanna A. W. , Lutz Martin , Spek Anthony L. , Bouwman Elisabeth 
Published: October 2003

AbstractThe nickel complex [Ni(xbsms)] [H2xbsms is α,α′‐bis(4‐mercapto‐3,3‐dimethyl‐2‐thiabutyl)‐o‐xylene] was reacted with FeCl2, [Fe2(CO)9], [Fe(CO)2(NO)2] and [Fe(CO)4I2]. The reaction with FeCl2 gives the heterotetranuclear nickel−iron complex [Ni(xbsms)FeCl2]2. The complex was characterised by analytical, spectroscopic and electrochemical methods and by X‐ray diffraction. [Ni(xbsms)FeCl2]2 crystallises in the monoclinic space group P21/c, with the dimer located on the inversion centre. The nickel ions are in a square‐planar S2S′2 environment, comprised of two thioether and two thiolate sulfur atoms. The thiolate sulfur atoms form a bridge between the nickel ion and the iron centre. The iron ions are in a pseudo square‐pyramidal S2Cl3 environment, with two chloride ions forming a bridge between the two iron centres. The Ni−Fe distance is 3.0403(3) Å. The reaction with [Fe2(CO)9], [Fe(CO)2(NO)2] or [Fe(CO)4I2] gives the heterodinuclear complexes [Ni(xbsms)Fe(CO)4], [Ni(xbsms)Fe(NO)2] and [Ni(xbsms)Fe(CO)2I2], respectively. These complexes were characterised by analytical, spectroscopic and electrochemical methods. In [Ni(xbsms)Fe(CO)4], one thiolate group bridges the Ni and Fe centres, whereas in [Ni(xbsms)Fe(NO)2] and [Ni(xbsms)Fe(CO)2I2], two thiolate groups form a bridge between the centres. These newly synthesised nickel−iron complexes appear to be suitable complexes for new structural models for [NiFe]‐hydrogenases. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Lacunary Wells−Dawson Sandwich Complexes − Synthesis, Characterization, and Stability Studies of Multi‐Iron Species
Authors: Mbomekalle Israel Martyr , Keita Bineta , Nadjo Louis , Neiwert Wade A. , Zhang Lei , Hardcastle Kenneth I. , Hill Craig L. , Anderson Travis M. 
Published: October 2003

AbstractReaction of α‐Na12(As2W15O56) with FeII in 1 M NaCl solution followed by air oxidation yields αααα‐H2Na14[(NaOH2)2FeIII2(As2W15O56)2] (Na2), the arsenic analogue of the divacant lacunary sandwich, αααα‐H2Na14[(NaOH2)2FeIII2(P2W15O56)2] (Na1). This complex (Na2) consists of a Na2Fe2 central unit sandwiched between two B‐α‐As2W15O5612− moieties. Both Na1 and Na2 react with one equivalent of FeIII to give ααβα‐Na14[(NaOH2)(FeIIIOH2)(FeIII)2(X2W15O56)2], where X = P (Na3) or As (Na4), or two equivalents of MnII to give αββα‐Na14[(MnIIOH2)2(FeIII)2(X2W15O56)2], where X = P (Na5) or As (Na6). A single‐crystal X‐ray diffraction analysis of Na5 has been carried out [a = 13.5387(8) Å, b = 13.9327(9) Å, c = 21.3347(13) Å, α = 92.921(1) °, β = 94.367(1) °, γ = 118.154(1) °, triclinic, P$\bar 1$
, R1 = 5.49%, based on 24662 independent reflections], which revealed a Mn2Fe2 central unit sandwiched between two B‐α‐P2W15O5612− units. All of the new complexes have been characterized by FTIR spectroscopy, UV/Visible spectroscopy, elemental analyses, and cyclic voltammetry, and they are all stable for at least 24 h over a wide pH range (0−7), except for Na4, which is unstable below pH 2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Impact of prefractionation using Gradiflow™ on two‐dimensional gel electrophoresis and protein identification by matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry
Authors: Pang Lisa , Fryksdale Beth G. , Chow Nicole , Wong David L. , Gaertner Alfred L. , Miller Brian S. 
Published: October 2003

AbstractPrefractionation of protein samples prior to two‐dimensional electrophoresis (2‐DE) has the potential to increase the dynamic detection range for proteomic analysis. We evaluated a membrane‐based electrophoretic separation technique (Gradiflow™) for its ability to fractionate an exoproteome sample from the filamentous fungus Trichoderma reesei. The sample was separated on the basis of size and charge. Buffer optimization was found to be necessary for successful size fractionation. Fractionation by charge was used to resolve the sample into four fractions that were subjected to analysis by two‐dimensional electrophoresis (2‐DE). Enhanced detection of low‐abundance proteins with selective removal of high‐abundance species was achieved. Fractionated and unfractionated samples were examined for differences in the ability to identify proteins following 2‐DE using trypsin in‐gel digestion followed by peptide mass fingerprinting using matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS). Fractionated samples showed marked improvement in protein identification ability and sequence coverage. This study demonstrates the utility of the Gradiflow™ for fractionation, resulting in an enhancement of resolution and characterization of a moderately complex proteome.
Proteomic analysis of transducin β‐subunit structural heterogeneity
Authors: Clack James W. , Juhl Martha , Rice Carol A. , Li Junyu , Witzmann Frank A. 
Published: October 2003

AbstractPartially purified transducin was resolved using two‐dimensional gel electrophoresis (2‐DE). Peptide mass fingerprinting of several different spots believed to correspond to the 37 kDa β‐subunit of transducin (Tβ) was performed. Spots were excised and proteolyzed using modified trypsin. Matrix‐assisted laser desorption/ionization‐mass spectrometry (MALDI‐MS) was performed on the peptide mixture resulting from each spot. As many as six spots with different pI, ranging from 5.2 to 6.1, were observed when separated using 2‐DE. MALDI peptide mass fingerprinting determined with high probability that all of the spots were the same gene product, guanine nucleotide‐binding protein GI/GS/GT β‐subunit 1 (GNB1; Tβ1). This suggested that post‐translational modification was responsible for the differences in pI. Phosphorylation experiments showed that at least one Tβ1 spot was phosphorylated in vitro with [γ‐32P]ATP by an endogenous kinase. Treatment of Tβ with alkaline phosphatase caused a large change in the spot pattern of Tβ, suggesting that phosphorylated Tβ is a substrate for alkaline phosphatase. We conclude that Tβ1 constitutes over 99% of the Tβ expressed in bovine rod outer segments and displays structural heterogeneity that is due to post‐translational modification. We also conclude that some, but not all, of the heterogeneity observed is due to phosphorylation of Tb1.
High‐resolution single‐stranded DNA analysis on 4.5 cm plastic electrophoretic microchannels
Authors: Shi Yining , Anderson Rolfe C. 
Published: October 2003

AbstractPlastic microchannels (4.5 cm long) fabricated from an etched glass master were tested for high‐resolution single‐stranded DNA analysis. Using replaceable denaturing linear polyacrylamide as sieving matrix, one‐color separation of a fragment sizing standard with single‐base resolution (R > 0.5) was achieved up to 275 bases. Two‐color sizing analysis of four loci short tandem repeat (STR) allelic ladder (CSF1PO, TPOX, TH01, vWA) with single‐base resolution (R = 0.62) on TH01 alleles 9.3 (198 bp) and 10 (199 bp) was demonstrated. An average standard deviation of ± 0.06 bp and ±0.11  bp in sizing 32 alleles of the CTTv ladder was attained between runs and between channels, respectively. Four‐color sequencing separation of a terminator sequencing standard showed a base‐calling accuracy of 99.1% out to 320 bases in 13 min.
Microarray‐based resequencing by apyrase‐mediated allele‐specific extension
Authors: Ericsson Olle , Sivertsson Åsa , Lundeberg Joakim , Ahmadian Afshin 
Published: October 2003

AbstractWe have developed an array‐based resequencing method to determine genetic alterations in putative cancer genes. The method relies on that the specificity of DNA polymerase in allele‐specific extensions can be enhanced by terminating the extension reactions with apyrase and that a tiling set of primers are synthesized covering the investigated gene sequence. We report on such apyrase‐mediated allele‐specific primer extension (AMASE) assay as a method suitable for high‐throughout resequencing and mutation detection in tumor suppressor genes and oncogenes. In the experimental setup, primers complementary to codons 12, 13 and codon 61 of the N‐ras proto‐oncogene were spotted onto glass slides. Overlapping sense and anti‐sense primers were designed so that complementary primers for all possible mutations in each base position were investigated. The extension reactions were performed in a single step following hybridization of target DNA to the immobilized primers on the array surface. Mutation detection limits and the possibility of quantifying the mutations were investigated using synthetic oligonucleotides. In addition, 64 clinical samples were sequenced and 16 of these showed mutations in the N‐ras gene.
Rice proteomics: Current status and future perspectives
Authors: Rakwal Randeep , Agrawal Ganesh Kumar 
Published: October 2003

AbstractRice, the first cereal crop genome to be decoded, has attracted the attention of researchers worldwide because of its immense socio‐economic impact on human existence. With the availability of the draft genome sequence of two major types, japonica‐ and indica‐rice, “rice proteomics” has entered into the era of functional genomics. Although during the last decade an important but limited progress (mainly construction of protein datafiles) has been made in the field of rice proteomics, it is only recently that dedicated research groups have taken this challenge to systematically analyze the rice proteome at the cell (and organelle), tissue, and whole plant level. Important gains achieved by the accelerated technological progress in protein separation and identification will help in going beyond the simple cataloguing of rice proteins in realistic terms. In this review, we discuss the progress made in the field of rice proteomics to date and dwell upon the future direction/problems/approaches towards defining the rice proteome.
Detection of metals in proteins by means of polyacrylamide gel electrophoresis and laser ablation‐inductively coupled plasma‐mass spectrometry: Application to selenium
Authors: Chéry Cyrille C. , Günther Detlef , Cornelis Rita , Vanhaecke Frank , Moens Luc 
Published: October 2003

AbstractThe capabilities of laser ablation‐inductively coupled plasma‐mass spectrometry for the detection of trace elements in a gel after gel electrophoresis were systematically studied. Figures of merit, such as limit of detection, linearity, and repeatability, were evaluated for various elements (Li, V, Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Pd, Ag, Cd, Pt, Tl, Pb). Two ablation strategies were followed: single hole drilling, relevant for ablation of spots after two‐dimensional (2‐D) separations, and ablation with translation, i.e., on a line, relevant for one‐dimensional (1‐D) separations. This technique was applied to the detection of selenoproteins in red blood cells extracts after a 1‐D separation (sodium dodecyl sulfate‐polyacrylamide gel electrophoresis) and the detection of selenium‐containing proteins in yeast after 2‐D electrophoresis (2‐DE). The detection procedure was further improved by using the dynamic reaction cell technology, which allowed the removal of the Ar_2+ interference and hence the use of the most abundant Se isotope, 80Se. Reaction gases were compared (methane, carbon monoxide, ammonia, oxygen and the combination of argon (collision gas) and hydrogen (reaction gas)). In each instance, the reaction cell parameters were optimized in order to obtain the lowest detection limit for Se (as 80Se+, 82Se+ or 77Se+; and as 80Se16O+, 82Se16O+ or 77Se16O+ with O2 as the reaction gas). Carbon monoxide was found to offer the best performance. The detection limit with the use of DRC and He as transport gas was 0.07 μg Se g−1 gel with single hole drilling and 0.15 μg Se g−1 gel for ablation with translation.
Comparative proteome analysis of culture supernatant proteins from virulent Mycobacterium tuberculosis H37Rv and attenuated M. bovis BCG Copenhagen
Authors: Mattow Jens , Schaible Ulrich E. , Schmidt Frank , Hagens Kristine , Siejak Frank , Brestrich Gordon , Haeselbarth Gisela , Müller Eva‐Christina , Jungblut Peter R. , Kaufmann Stefan H. E. 
Published: October 2003

AbstractA comprehensive analysis of culture supernatant (CSN) proteins of Mycobacterium tuberculosis H37Rv was accomplished by combination of two‐dimensional electrophoresis (2‐DE), mass spectrometry, and N‐terminal sequencing by Edman degradation. Analytical 2‐DE gels resolved approximately 1250 protein spots from CSN of M. tuberculosis H37Rv, 381 of which were identified by mass spectrometry and/or Edman degradation. This study revealed 137 different proteins, 42 of which had previously been described as secreted. Comparative proteome analysis of CSN from virulent M. tuberculosis H37Rv and attenuated Mycobacterium bovis BCG Copenhagen identified 39 M. tuberculosis‐specific spots containing 27 different proteins, representing candidate antigens for novel vaccines and diagnostics in tuberculosis. These included five proteins encoded by open reading frames absent from M. bovis BCG, e.g., early secretory antigen target (Esat6), as well as 22 novel differential proteins, such as acetyl‐CoA C‐acetyltransferase (Rv0243) and two putative Esat6‐like proteins (Rv1198, Rv1793).
On‐column concentration and separation of double‐stranded DNA by gradient capillary electrophoresis
Authors: Kuo I‐Ting , Chiu Tai‐Chia , Chang Huan‐Tsung 
Published: October 2003

AbstractWe describe the separation of dsDNA by capillary electrophoresis in the presence of electroosmotic flow (EOF) using poly(ethylene oxide) (PEO). Using 1.0% PEO, the separation of DNA fragments with sizes ranging from 51 bp to 23 kbp has been achieved in less than 12 min, which is better than conventional methods (in the absence of EOF) in terms of speed and resolution. In order to concentrate and separate the DNA sample, gradient changes in the concentrations of PEO and ethidium bromide (EtBr) have been conducted. Different concentrations of PEO solutions are injected to the polyethylene tubes by pressure, where they enter the capillary by EOF. Because the large DNA fragments migrate faster towards the cathode end under counterflow conditions, the introduction sequence is from low to high concentrations of PEO solutions after sample injection. Using the gradient CE approach, the separations of the DNA sample injected at 30 cm height for times up to 120 s have been demonstrated. The linearity between injection time and peak height shows that the DNA fragments stacked during migration from the sample zone to PEO. We found that stacking efficiency is greater when the analysis was performed by simultaneously changing the PEO and EtBr concentration, compared to individual changes in PEO concentration.
Highly sensitive and simple fluorescence staining of proteins in sodium dodecyl sulfate‐polyacrylamide‐based gels by using hydrophobic tail‐mediated enhancement of fluorescein luminescence
Authors: Kang Chulhun , Kim Hyun Jung , Kang Donghoon , Jung Duk Young , Suh Myungkoo 
Published: October 2003

AbstractFluorescein has an extremely low luminescence intensity in acidic aqueous media. However, when it was bound to proteins, subsequent increase of luminescence intensity took place. Furthermore, when a hydrophobic tail, such as aliphatic hydrocarbons, was introduced to fluorescein, more dramatic increase of luminescence intensity was observed upon binding to proteins. In the present study, by utilizing this luminescence enhancement, three hydrophobic fluorescein dyes (5‐dodecanoyl amino fluorescein, 5‐hexadecanoyl amino fluorescein, and 5‐octadecanoyl amino fluorescein) were examined as noncovalent fluorescent stains of protein bands in sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). Effective incorporation of the dyes to proteins in gels was accomplished either simply by adding dyes at the protein fixation step, or by treating gels with a staining solution after the fixation. The sensitivity of this staining method using the fluorescein derivatives was approximately 1 ng/band for most proteins. For some cases, protein bands containing as low as 0.1 ng were successfully visualized. In addition, the detection sensitivity showed much less protein‐to‐protein variation than silver staining. This new staining method was also successfully applied to two‐dimensional electrophoresis of rat brain proteins. Its overall sensitivity was comparable to that of silver staining.
Electrophoretic dynamics of large DNA stars in polymer solutions and gels
Authors: Heuer Daniel M. , Saha Sourav , Archer Lynden A. 
Published: October 2003

AbstractWe have developed a procedure for synthesizing large stable branched DNA structures that enables visualization via fluorescence microscopy. Using this procedure we have synthesized large DNA stars and observed their electrophoretic behavior in polymer solutions and gels. In dilute polyacrylamide solutions, the DNA stars move as random coils and appear to experience only brief collisions with the polymer chains in solution. The effect of polymer solution concentration on the electrophoretic mobility of stars in the dilute regime is found to be in good accord with predictions of the transient entanglement coupling (TEC) model. In semidilute polymer solutions, the star arms extend in the field direction and drag the core through the matrix. The star arms form several U‐shaped conformations as they collide and engage with polyacrylamide chains. The U‐shaped conformations occasionally evolve into J‐shaped conformations as the star arms slide off the matrix chains they engage during electrophoretic migration. In concentrated polymer solutions, the arms of the star extend and form V‐shaped structures with the core as the apex. The arms then pull the core through the matrix. These V‐shaped conformations are much longer‐lived than U‐shaped ones and, unlike the latter, do not transform to J‐shaped conformations. In polyacrylamide and agarose gels, where matrix entanglements are fixed, DNA stars become trapped when entanglements with matrix molecules prevent the core from being pulled through the matrix by the extended arms. This trapping was observed at all gel concentrations and electric fields studied.