bluuebunny/crossref_metadata_2025 huggingface dataset:
Delayed selfing and low levels of inbreeding depression in Hibiscus trionum (Malvaceae)
Authors: Ramsey Mike , Seed Leahwyn , Vaughton Glenda
Published: August 2003

We used experimental pollinations to examine the breeding system and inbreeding depression in Hibiscus trionum L., an annual herb of cultivated and disturbed sites in eastern Australia. Seeds were not produced asexually. Flowers were fully self-compatible and autonomously self-pollinating. Autonomous self-pollination was due to a delayed selfing mechanism that gave precedence to cross pollen but ensured that stigmas contacted the anthers at the end of floral life. Using selfed and crossed progeny from 10 maternal plants, we examined the magnitude and timing of inbreeding depression over a range of life-cycle stages, including seed production by maternal plants, and seed germination, seedling growth, survival, flowering and seed production by F1 plants. Average cumulative inbreeding depression was 0.15, although there was considerable variation among maternal families (δ = –0.07–0.43). Inbreeding depression was not uniform across all life stages and was most prevalent late in the life cycle, affecting days to flowering and fruiting and flower production. Our results indicate that major lethal alleles have been purged from this population, probably through high levels of recurrent self-fertilisation. The flexibility in plant mating afforded by delayed selfing is likely to contribute to the invasiveness of H. trionum, particularly in annual cropping situations.
Gene flow between introduced and native Eucalyptus species: exotic hybrids are establishing in the wild
Authors: Barbour R. C. , Potts B. M. , Vaillancourt R. E.
Published: August 2003

F1 hybrids between exotic Eucalyptus nitens plantations and native E. ovata have previously been reported among seedlings grown from open-pollinated seed collected from E. ovata, on the island of Tasmania. Such exotic hybrid seedlings have now been found in the wild adjacent to plantations at three locations. The proportion of exotic hybrids in open-pollinated seed collected from nearby mature E. ovata was 5.5%. This level compares with only 0.4% for natural hybrids between native species at these sites (E. ovata, E. viminalis and E.�rodwayi). Detection of hybrids was initially based on their deviant morphology, which was generally intermediate between parental species. This subjective classification was then successfully verified by morphometric and allozyme analyses. Pure E. nitens seedlings (wildlings) were restricted to within 30 m of these plantations, whereas established hybrids were found up to 310 m from the plantations. This pattern of establishment reflects dispersal of exotic seed and pollen respectively. It is likely that the recent expansion of the eucalypt plantation estate in Australia will cause an increase in the frequency of exotic hybrids. However, the long-term impact of such hybridisation is yet to be assessed.
Chromosome number and size variations in the Australian Salicornioideae (Chenopodiaceae)—evidence of polyploidisation
Authors: Shepherd K. A. , Yan G.
Published: August 2003

New somatic chromosome counts were recorded from 27 accessions representing 21 Australian species across six genera, Halosarcia Wils., Pachycornia Hook.f., Sarcocornia Scott, Sclerostegia Wils., Tecticornia Hook.f. and Tegicornia Wils., in the subfamily Salicornioideae Ulbr. (Chenopodiaceae Venten.). The results indicated that the Australian Salicornioideae have a basic chromosome number of x = 9, congruent with other members of the Chenopodiaceae. Polyploidy is evident, particularly in the largest genus Halosarcia, ranging from diploid to hexaploid (2x = 18, 27, 36 and 54). With the exception of Pachycornia triandra (F.Muell.) Black, the chromosomes observed were 1.11–3.85 μm in length, with a total genome length of the haploid set of 13.82–23.16�μm. P. triandra had considerably larger chromosomes (3.09–5.57 μm) with a total genome length of the haploid set of 36.93 μm.Intraspecific ploidy variation occurs in the mostly endemic genus Halosarcia, which is the largest genus in the subfamily. Diploid, triploid and tetraploid ploidy levels were detected in H. indica (Willd.) subsp. bidens (Nees) Wils. sampled from separate populations and two ploidy levels were recorded in seedlings germinated from individual H. leptoclada Wils. and H. pterygosperma (Black) Wils. adults. The presence of polyploidy in Halosarcia may provide a mechanism that fosters diversity and phenotypic variation.
Synthesis and Phytotoxicity Evaluation of Substituted para-Benzoquinones
Authors: Lima Larissa S. , Barbosa Luiz Cláudio de A. , de Alvarenga Elson S. , Demuner Antônio J. , da Silva Antônio A.
Published: August 2003

Sorgoleone (1) is one of the major constituents of sorghum root exudates. Sorgoleone is an allelochemical that reduces the growth of broad-leaf plants. The 3,5-dimethoxybenzylic alcohol (3) was used as starting material for the synthesis of 2-methoxy-6-(non-1-yl)benzo-1,4-quinone (9) in 69% yield. Acetylation of (9) with acetic anhydride gave the triacetate (10) in 82% yield. The triacetate (10) was then converted in two steps in 2-hydroxy-5-methoxy-3-(non-1-yl)benzo-1,4-quinone (11) and 2-acetoxy-5-methoxy-3-(non-1-yl)benzo-1,4-quinone (12) in 8% and 37% yield, respectively. Quinone (11) was obtained also by reaction of (12) with DBU in 63% yield. Alkylation of (3) and oxidation with chromic anhydride formed the new quinones (16) (17) and (18) in 23%, 16% and 12% overall yield, respectively. The effect of these quinones and sorgoleone (1) at concentrations of 5.5 μg g–1 on the development of radicle and aerial parts of Cucumis sativus, Brachiaria decumbens, Hyptis lophanta, and Euphorbia heterophylla was tested.
Solid-State Complexation Reaction between p-Benzoquinone and p-Nitroaniline
Authors: Singh N. B. , Pathak Aradhana , Fröhlich Roland
Published: August 2003

Reaction between p-benzoquinone (p-BQ) and p-nitroaniline (p-NA) occurs both in the solid state and solution, forming a weak molecular addition compound (p-BQ)1 · (p-NA)1 in which the two components are associated by hydrogen bonding between one O atom of p-BQ and one H atom of the NH2 group of p-NA. Single crystals of the reaction product grown from solution belong to a monoclinic system.
Unique Tetradentate Coordination of 2,2′-Bipyridyl-3,3′-Dicarboxylate (bpdc). Hydrothermal Synthesis and Crystal Structure of A Novel Polymeric Supramolecule [Co(bpdc)(H2O)2]n
Authors: Wu Ben-Lai , Zhang Hong-Quan , Zhang Hong-Yun , Wu Qing-An , Hou Hong-Wei , Zhu Yu , Wang Xiang-Yu
Published: August 2003

The title complex has been synthesized using hydrothermal methods and its structure determined by X-ray diffraction. It consists of polymeric chains of [Co(bpdc)(H2O)2] units (bpdc = 2,2′-bipyridyl-3,3′-dicarboxylate) which are linked by intermolecular hydrogen bonds to form two-dimensional layer-shaped supramolecules. Each bpdc ligand bridges two cobalt(II) centers in a rare tetradentate fashion through its two pyridyl nitrogen atoms chelating to one cobalt and two carboxyl oxygen atoms to the other in the equatorial plane. The octahedral coordination of cobalt is completed by two axial water molecules.
Crystal and Molecular Structures of Some Alkynyl - Group 9/Group 11 Complexes [M2m4(C2R)8(PPh3)2] (M = Rh, Ir; m = Cu, Ag; R = Ph, Fc (Ir/Cu only))
Authors: Bruce Michael I. , Zaitseva Natasha N. , Skelton Brian W. , Somers Neil , White Allan H.
Published: August 2003

The crystal and molecular structures of five complexes [M2m4(C≡ CR)8(PPh3)2] (M = Rh, Ir; m = Cu, Ag; R = Ph, Fc (Ir/Cu only)) are described. Each consists of an approximately octahedral arrangement of the six metal atoms, with atoms M occupying opposite apical positions and atoms m forming an approximate plane. Four alkynyl groups are σ-bonded to each M. Two of these, one from each M, also interact by an asymmetric π-bonding mode with each atom m. Each M is also coordinated to one PPh3 ligand. The M–m distances range between 2.7698(9) and 3.2050(9) Å, although average values fall within the tight ranges 2.86(8) and 2.90(5) (m = Cu) or 3.06(5), 3.09(9) Å (m = Ag). Formally non-bonding M ··· M distances range between 4.1511(8) and 4.654(1) Å, while the shorter m ··· m separations range between 2.659(1) and 2.918(2) Å, which suggests that only weak intermetallic bonding exists. Both the geometries of these complexes and their intense colours suggest that the M2m4 cluster formulation is a major contributor to the structure, rather than a more simplistic, formally zwitterionic assemblage of two [M(C≡ CR)4(PPh3)]2− centres held together by the four m+ cations.
Synthesis, Characterization, and Crystal Structures of [Cu(ca2en)(PPh3)(X)] (X = Cl, Br, I, NCS, N3) Complexes
Authors: Kickelbick Guido , Amirnasr Mehdi , Khalaji Aliakbar D. , Dehghanpour Saeed
Published: August 2003

Novel mixed-ligand copper(I) complexes, [Cu(ca2en)(PPh3)X] (ca2en = N,N′-bis(trans-cinnamaldehyde)-1,2-diaminoethane, X = Cl (1), Br (2), I (3), NCS (4), N3 (5)), have been synthesized and characterized by 1H and 31P NMR spectroscopy, infrared spectroscopy, and elemental analyses. The single crystal X-ray structures of complexes (1)–(5) have been determined. All five complexes reveal discrete monomeric structures in the crystal. The geometry around the copper atom is in each case a distorted tetrahedron, with the distortion most pronounced in (3). The NCS− and N3− are coordinated as terminal ligands and the NCS− ligand is N-bonded in (4). Dynamic 31P NMR studies show partial bond breaking in solution.
α-Sulfonyl Radical Initiated Intramolecular Tandem Radical Cyclization: Stereochemistries of a Pair of Doubly Cyclized Products
Authors: Byrne Lindsay T. , Phomakotr Manat , Poolsanong Chompoonut , Reutrakul Vichai , Skelton Brian W. , White Allan H.
Published: August 2003

Room-temperature single-crystal X-ray structure determinations are recorded for trans-1,2,3,3a,9,9a-Hexahydro-cyclopenta[b]-1-benzothiapyran-4,4-dioxide and its 3a-methyl analogue, minor products of the α-sulfonyl radical-initiated intramolecular tandem radical cyclization of H2C=CH(CH2)CRBrSO2Ph (R = H, CH3), confirming the assigned structures and rigorously establishing the trans relationship at the ring junctions.
Synthesis and Structure of the Binuclear 1 : 1 Silver(I) 2-Hydroxy-3,5-dinitrobenzoate/Triphenylphosphine Complex
Authors: Othman A. Hamid bin , Skelton Brian W. , White Allan H.
Published: August 2003

A room-temperature single-crystal X-ray structure determination of the 1 : 1 adduct of silver(I) 2-hydroxy-3,5-dinitrobenzoate/triphenyl-phosphine (AgL/PPh3) was recorded, showing it to be a binuclear centrosymmetric system with the silver atoms bridged by one of the carboxy oxygen atoms of each ligand, [(PPh3)Ag(μ-O)2Ag(PPh3)] as in the parent acetate; the phenolic oxygen, retaining its protonation, is hydrogen bonded within the ligand to the other feebly chelating carboxylate oxygen.
Syntheses of New Gramicidin A Derivatives
Authors: Bali Doreen , King Lionel , Kim Sungho
Published: August 2003

Gramicidin A was covalently coupled with theophylline, thyroxine, digoxigenin, and biotin. New compounds were synthesized when the four molecules were coupled to ethanolamine on the C-terminus of gramicidin. Peptidic linkers were inserted between gramicidin and the bio-molecules.
Discrimination Effects in MALDI-MS of Mixtures of Peptides—Analysis of the Proteome
Authors: Burkitt William I. , Giannakopulos Anastassios E. , Sideridou Foteini , Bashir Sajid , Derrick Peter J.
Published: August 2003

Peptide ion suppression in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) can hinder the detection of site-specific post-translational protein modifications. Within a peptide mixture, the presence or absence of a particular peptide can affect the ion intensities of other peptides in the mixture. These effects have been studied using equimolar solutions of target peptides and observation of the increase or decrease in ion intensity of the peptides upon the removal or addition of individual peptides. Gas-phase basicities and hydrophobicity measures have been used to rationalize this behaviour. ZipTips have been used to remove impurities and reduce the number of peptides present at any moment in a solution, a procedure that results in a significant increase in the total percentage of the amino acid coverage of enzymatically digested proteins. The efficacy of this approach was demonstrated using specifically nitrated lysozyme and specifically nitrated myoglobin.
Structural Effects on the Gas Phase Reactivity of Organic Salt Complexes: Substitution versus Hofmann Elimination
Authors: Gronert Scott , Fong Lil-Myra
Published: August 2003

Salt complexes between a dianion and a tetraalkylammonium cation were formed during electrospray ionization (ESI) and their reactions were studied under collision-activated dissociation (CAD) conditions in a quadrupole ion trap mass spectrometer. Products corresponding to SN2 and E2 reactions within the complexes were observed. The competition between substitution and elimination was explored by varying the nature of the alkyl group on the ammonium. In addition, primary and secondary deuterium kinetic isotope effects were determined for the E2 (kH/kD = 3.5 ± 0.2) and SN2 reactions (kH/kD = 0.94 ± 0.05), respectively. When compared with the analogous bimolecular reactions of alkyl bromides, the data indicate that Hofmann (ammonium salts) and Saytzev (alkyl bromides) reactivity patterns are operative in the gas phase.
Reactions of Active Methylene Compounds with Benzhydrol During Solvolysis in Formic Acid
Authors: Gullickson Glen C. , Lewis David E.
Published: August 2003

Formic acid reacts with benzhydrol to give benzhydryl formate, which reacts with active methylene compounds in refluxing formic acid to give either C-alkylation or Ritter reaction products. The product formed is determined by the equilibrium enol content of the active methylene compound. These reaction conditions avoid the use of halogenated reaction solvents, and the pure products are isolated without recourse to chromatography.
Structure-Making with 3,5-Dinitrosalicylic Acid. II. The Proton-Transfer Compounds of 3,5-Dinitrosalicylic Acid with the Monocyclic Heteroaromatic Amines
Authors: Smith Graham , Wermuth Urs D. , Healy Peter C. , White Jonathan M.
Published: August 2003

The crystal structures of the proton-transfer compounds of 3,5-dinitrosalicylic acid (dnsa) with a series of common monocyclic heteroaromatic amines (pyridine, 4-cyanopyridine, pyridine-4-carboxylic acid, 2,6-diaminopyridine, and 2-aminopyrimidine) have been determined and the hydrogen-bonding associations in each analyzed. The compounds are the adduct [(C5H6N)+(dnsa)–· (dnsa)] (1), the 1 : 1 salts [(C6H5N2)+(dnsa)–] (2), [(C6H6NO2)+(dnsa)–] (3), [(C5H8N3)+(dnsa)–] (4), and the 2 : 2 ethanol hemi-solvate [2(C4H6N3)+·2(dnsa)–· 0.5(EtOH)] (5). With all compounds, protonation of the hetero-nitrogen atom occurs with subsequent hydrogen bonding to the oxygen atoms of the functional groups of the dnsa anions, resulting in the formation of relatively simple linear or chain polymer associations. Compound (1) represents a rare example of other than a 1 : 1 association, and the first example of a 2 : 1 (dnsa/amine) type, with the unusual presence of an additional adduct molecule of dnsa in the structure.
Clathriol B, a New 14β Marine Sterol from the New Zealand Sponge Clathria lissosclera
Authors: Keyzers Robert A. , Northcote Peter T. , Berridge Michael V.
Published: August 2003

A new anti-inflammatory sterol, clathriol B (1.3 mg), was isolated from the New Zealand marine sponge Clathria lissosclera collected at the Three Kings Islands. Clathriol B possesses the unusual 14β stereochemistry, a structural feature that occurs naturally only in marine sponges.
Designing Biostable Polyurethane Elastomers for Biomedical Implants
Authors: Gunatillake Pathiraja A. , Martin Darren J. , Meijs Gordon F. , McCarthy Simon J. , Adhikari Raju
Published: August 2003

The chemical structure, synthesis, morphology, and properties of polyurethane elastomers are briefly discussed. The current understanding of the effect of chemical structure and the associated morphology on the stability of polyurethanes in the biological environments is reviewed. The degradation of conventional polyurethanes appears as surface or deep cracking, stiffening, and deterioration of mechanical properties, such as flex-fatigue resistance. Polyester and poly(tetramethylene oxide) based polyurethanes degrade by hydrolytic and oxidative degradation of ester and ether functional groups, respectively. The recent approaches to develop polyurethanes with improved long-term biostability are based on developing novel polyether, hydrocarbon, polycarbonate, and siloxane macrodiols to replace degradation-prone polyester and polyether macrodiols in polyurethane formulations. The new approaches are discussed with respect to synthesis, properties and biostability based on reported in vivo studies. Among the newly developed materials, siloxane-based polyurethanes have exhibited excellent biostability and are expected to find many applications in biomedical implants.
Hydrolysis of Sesquimustards
Authors: St Quintin Timothy D. , Leslie D. Ralph , Collins J. Grant
Published: August 2003

The hydrolysis of the sesquimustards 1,2-bis(2-chloroethylthio)ethane (QN2) and 1,3-bis(2-chloroethylthio) propane (QN3) has been studied by 1H and 13C nuclear magnetic resonance spectroscopy. For both sesquimustards, stable cyclic sulfonium ions were observed in hydrolysis experiments in a 1 : 1 mixture of [D6]acetone and D2O. The cyclic sulfonium ions, which persist in the aqueous solution for up to a week, are likely to retain some toxicity and could possibly be used as markers for sesquimustards in the analysis of mustard-contaminated soil for chemical weapons treaty verification. The formation of a macrocyclic oxadithiaether was also demonstrated for QN2 but not QN3.
Synthesis of Photopolymerizable Glycolipids and their Application as Scaffolds to Immobilize Proteins with a Micron-Sized Pattern
Authors: Nagahori Noriko , Niikura Kenichi , Sadamoto Reiko , Monde Kenji , Nishimura Shin-Ichiro
Published: August 2003

Photopolymerizable glycolipids incorporating ceramide- or amido-type linkers and able to form stable monolayers were efficiently synthesized by chemical and enzymatic methods. Glycolipid polymer films served as platforms for the immobilization of proteins through specific carbohydrate–protein interactions at the air–water interface. Carbohydrate-binding proteins deposited on the glycolipid film were observed by atomic force microscopy, which showed varying submicron-sized protein patterns such as dendrites, dots, and networks, depending on the lipid structure, membrane preparation process, and sugar density of the membrane. Surface plasmon resonance measurement confirmed that the subunit-type lectins immobilized on the glycolipid membranes exhibited the ability to interact specifically with carbohydrate ligands by using unoccupied binding sites.
Gas Phase Reactions of Trimethylborate with the [M − H]− Ions of Nucleotides and Their Non-Covalent Homo- and Heterodimer Complexes
Authors: Vrkic Ana K. , O'Hair Richard A. J.
Published: August 2003

Trimethylborate (TMB) reacts with deprotonated monomer, homo-, and heterodimer ions of nucleotides (2′-deoxyadenosine-5′-monophosphate [dAMP], 2′-deoxycytidine-5′-monophosphate [dCMP], 2′-deoxyguanosine-5′-monophosphate [dGMP], and 2′-deoxythymidine-5′-monophosphate [dTMP]) in a quadrupole ion trap mass spectrometer by addition with concomitant elimination of one or two methanol molecules (monomers), one or three methanol molecules (homodimers), and three methanol molecules (heterodimers). The mode of reaction appears to influence the observed rates, with the loss of only one methanol molecule corresponding to the fastest rate. There appears to be a structure–reactivity correlation for the monomers, with the [dGMP – H]– ions (which adopt a syn conformation of the guanine moiety) reacting fastest with TMB through the loss of only one methanol molecule. No such structure–reactivity trends are observed for the homo- and heterodimers. In addition, the collision-induced dissociation (CID) reactions of the [(dXMP)n − H]– (n = 1 or 2) as well as the [dXMP + dYMP – H + (CH3O)3B – 3(CH3OH)]– ions (where nucleotides X, Y = A, C, G, or T) were studied. The latter fragment to form [dXMP – H + BPO4]– and [dXMP – 3H + BPO3]– ions (where X = A, C, G, or T), while [dXMP – H]– ions fragment by neutral base loss. The homo- and heterodimers fragment to form [dXMP – H]– and [dXMP + HPO3]– ions, and the relative abundances of the [dXMP – H]– monomer ions from the heterodimers led to the following acidity order: dGMP ≈ dTMP > dCMP > dAMP.
Azacineole (1,3,3-Trimethyl-2-azabicyclo[2.2.2]octane)
Authors: Carman Raymond M. , Derbyshire Roger P. C.
Published: August 2003

The title compound (5) has been synthesized and its presence sought in various eucalypt leaf oils. Aspects of the chemistry of the precursor aziridine (14) are discussed.
Counting Single DNA Molecules in a Capillary with Radial Focusing
Authors: Zheng Jinjian , Yeung Edward S.
Published: August 2003

For single-molecule detection, usually a small detection volume of 10 pL or less is used to improve the signal-to-noise ratio. Detection of every molecule in a sample requires that the sample be driven through a well-defined volume to facilitate laser excitation. We report a novel approach to count single DNA molecules with nearly 100% efficiency. By applying an electric field across a 40 cm long, 75 × 75 µm2 square capillary together with hydrodynamic flow from cathode to anode, we were able to concentrate more than 95% of DNA molecules into a 10 µm region at the centre of the capillary. The YOYO-1 labelled λ-DNA molecules were imaged with an intensified CCD camera. We found that the single DNA molecule detection efficiency in a 10–17 M solution was 114 ± 21%. The mobility of the DNA molecules after radial focusing was relatively constant, with relative standard deviations ranging from 0.8% to 1.4%. This allowed us to match the sampling rate to the length of the detection window to maximize counting efficiency. Analysis of a 40.2 nL injected plug of 2 × 10–14 M λ-DNA gave a result of 492 ± 73 molecules, which agreed well with the estimated value of 484. This method should be generally useful for counting deformable molecules or non-spherical particles at extremely low concentrations.
Synthesis, Characterization, and Ethylene Oligomerization of 2,6-Bis(imino)phenoxy Cobalt Complexes
Authors: Du Jianlong , Han Lingqin , Cui Yong , Li Jitai , Li Yan , Sun Wen-Hua
Published: August 2003

A series of cobalt complexes bearing 2,6-bis(imino)phenoxy ligands were synthesized by treating the ligand 2,6-bis(imino)phenol with a molar equivalent of cobalt dichloride. These complexes were characterized by elemental analyses and IR spectroscopy. The structure of the resulting complex was determined by single-crystal X-ray diffraction; it crystallizes in the monoclinic space group C2/c, with a 22.313(3) Å, b 14.7078(15) Å, c 17.7652(17) Å, β 107.96(7)°, and V 5546.0(10) Å3. The coordination geometry around the cobalt atom can be described in terms of a distorted tetrahedral bonded with one phenoxy oxygen, one imino nitrogen, and two chloride atoms. In the presence of a methylaluminoxane cocatalyst, this and related complexes displayed catalytic activities towards ethylene oligomerization.
Neotricone and Norperistictic Acid, Two New Depsidones from the Lichen Genus Phaeographis
Authors: Elix John A. , Kalb Klaus , Wardlaw Judith H.
Published: August 2003

Two new β-orcinol depsidones, neotricone (4,10-dihydroxy-5,8-dimethyl-3,7-dioxo-1,3-dihydro-7H-isobenzofuro[4,5-b][1,4]benzodioxepin-11-carboxylic acid) (2) and norperistictic acid (1,4,10-trihydroxy-5,8-dimethyl-3,7-dioxo-1,3-dihydro-7H-isobenzofuro[4,5-b][1,4]benzodioxepin-11-carboxylic acid) (4) have been identified in the lichens Phaeographis syngraphizans and P. neotricosa. The structure of the new depsidones followed from a combination of partial syntheses, chromatographic comparisons, and spectroscopic data.
Solid-State NMR Structural Determination of Components in an Ion Channel Switch Biosensor
Authors: Anastasiadis Aphrodite , Separovic Frances
Published: August 2003

High-resolution structural analysis of membrane proteins is difficult to achieve with the commonly used methods of structural biology, X-ray diffraction, and solution-state NMR spectroscopy. By combining solid-state NMR studies of membrane peptides in powder and oriented samples, with solution-state studies in detergent micelles, three dimensional molecular structures can be obtained. We have used solid-state NMR methods to study the antibiotic, gramicidin A (gA), a peptide that forms ion channels in bilayer lipid membranes (BLMs). Receptor groups have been linked to gA channels embedded in a BLM tethered to a gold electrode in an 'ion channel switch' biosensor. The receptor is attached to gA via a protein (either streptavidin or avidin) bonded to a biotin (B) moiety, with B in turn being covalently linked to the C-terminus of gA by one or more aminocaproyl (X) groups. Using NMR, we determined that the structures of these biotinylated gA analogues are very similar to native gA, and that biotinylated gA analogues with longer linkers (more X groups) are more accessible for binding to streptavidin/avidin and hence function better as ligand-gated ion channels.
Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device: An Overview
Authors: Heinema William R. , Seliskar Carl J. , Richardson John N.
Published: August 2003

A novel type of sensor based on spectroelectrochemical techniques possessing three modes of selectivity is described. The selectivity of this type of sensor comes from the ability of the analyte to (1) partition into an ion-exchange film coating an optically transparent electrode (OTE), (2) undergo oxidation or reduction at a given potential, and (3) absorb light in either its oxidized or reduced form at the analytical wavelength. This review charts the development of this type of sensor from its inception, illustrating its ability to selectively sense target ions in the presence of various interferents, its limits of detection, and our attempts to modify and improve its performance in both of these areas. Also provided is an overview of how this type of sensor can be employed as a small, portable unit appropriate for field work; an example is its employment in the detection of ferrocyanide in tank waste at the Hanford nuclear waste site located near Richland, Washington. Such applications as this illustrate the effectiveness of the sensor design, especially when used in harsh, real-world conditions where many sensor prototypes fail.
Advances in the Application of Array Detectors for Improved Chemical Analysis, Part I. Comparison of Qualitative Analyses Using Large, Computer-Based Raman Spectral Libraries
Authors: Denton M. Bonner , Sperline Roger P. , Giles Jeffrey H. , Gilmore Daniel A. , Pommier Carolyn J. S. , Downs Robert T.
Published: August 2003

Although a mature technique, Raman spectroscopy remains not widely used as a routine analytical technique. The advantages of Raman spectroscopy, such as minimal sample preparation and relatively uncomplicated spectra, combined with technical advances, including more stable diode lasers, higher quality filters, and better polychromators and array detectors, have led to a renaissance in sensitive and versatile Raman spectrometers. The lack of appropriate databases for routine analysis, which represents the last barrier to the technique's widespread use, is beginning to be overcome, as described in this review.
Advances in the Application of Array Detectors for Improved Chemical Analysis, Part II. Rapid Trace Metal Analysis of High Solids Wastewater and Sludge Using a Direct Current Plasma Source Equipped with an Echelle Spectrometer and a Charge-Injection Device Detector
Authors: Prevatt Jeff , Denton M. Bonner
Published: August 2003

A direct current plasma (DCP) source, equipped with an echelle spectrometer and charge-injection device (CID) detector, was employed for the analysis of trace metals in municipal sludge and wastewater containing high solids. The use of DCP as a plasma source has largely vanished in the past decade due to the popularity of inductively coupled plasma. Resurrecting this robust plasma source and coupling it to a state-of-the-art echelle spectrometer provides for an extremely forgiving analytical technique capable of analysing trace metals rapidly, even in complex high-solid matrices. Instrument performance is further enhanced as the echelle/CID spectrometer provides a simultaneous multi-element fingerprint of contaminants in the waste. The improved design offers increased sensitivity in the far ultraviolet, with overall wavelength coverage from 175 to 800 nm. Furthermore, multi-element analysis is obtained quickly with minimal or no sample preparation, making this the fastest screening technique available.
Measurement of Trace Elements in Marine Environmental Samples using Solution ICPMS. Current and Future Applications
Authors: Maher William , Krikowa Frank , Kirby Jason , Townsend Ashley T. , Snitch Peter
Published: August 2003

The strengths and weaknesses of using inductively coupled plasma mass spectrometer (ICPMS) measurements of samples in solution for marine environmental analyses using real world examples is discussed.
ICPMS can detect nanogram per litre concentrations of trace elements but suffers from polyatomic interferences generated from the sample matrix. Most of the routine trace elements measured in marine biological tissue and sedimentdigests, with the notable exceptions of iron, chromium, vanadium, and selenium, are not subject to severe interferences. Low recoveries of trace elements from sediments are due to the inability of extraction acids to remove trace elements such as chromium and nickel from sediment matrices. The use of ICPMS offers the advantage that elements such as phosphorus, which previously required elaborate digestion procedures and a colorimetric determination, can be rapidly determined using nitric acid digestion alone.
The use of flow injection coupled with ICPMS allows on-line preconcentration of trace metals and metalloids using chelation by ion-exchange resins or hydride generation and trapping as well as separation from matrix elements. Thus, the routine determination of trace elements and inorganic and methylated arsenic, antimony, mercury, and germanium species in open-ocean waters is possible.
The coupling of HPLC and GC to ICPMS allows the measurement of metal and metalloid species in biological and sediment extracts. However, extraction of unaltered species from matrices presents a challenge. Many of the species found in the environmental samples are not known and analytical standards are not available. The concurrent use of HPLC-MS is needed to confirm these species.
Detection of NO at Small Carbon Electrodes as a Means to Assess the Inhibition Efficiency in its Release from Foetal Pig Islet-Like Cell Clusters
Authors: Lin Jianwei , Smith Murray S. R. , Tuch Bernard E. , Walsh David A. , Wong Danny K. Y.
Published: August 2003

As a xenotransplant, foetal pig islet-like cell clusters (ICCs) are tissues with a potential to reverse hyperglycaemia in Type I diabetes. Following the exposure of ICCs to some pro-inflammatory cytokine factors, the amino acid L-arginine is catalytically cleaved into NO. A cascade of events is then triggered by the NO, leading to tissue apoptosis. In our laboratory, N-monomethyl-L-arginine (an antagonist of NO formation) and heat shock treatment (an inhibitor of NO synthetic enzyme) have been used to prevent pathological injuries in cytokine-induced ICCs. Chronoamperometry at Nafion-coated carbon cylinder electrodes (<5 µm tip diameter) adjacent to cytokine-induced ICCs was employed in this study to periodically monitor NO release and diffusion in ICCs, so that the inhibition efficiency of the respective treatments could be evaluated. Using cytokine-induced ICCs with L-arginine, the electrode recorded a current increase, arising from the oxidation of released NO, over a period of 30 min, followed by a current plateau that persisted for 3 h. In contrast, no corresponding current increase was observed in control experiments involving non-cytokine-induced ICCs with L-arginine, demonstrating the reliability of the direct detection of NO at the carbon electrodes. When the cells were subjected to N-monomethyl-L-arginine or mild heat shock pre-treatment, a decrease in the oxidation current of released NO was observed, demonstrating their inhibitive role in down-regulating NO generation and release.
Rapid Determination of Sequence Selectivity and Stability of Alkylated Oligonucleotide Adducts by Electrospray Tandem Mass Spectrometry
Authors: Colgrave Michelle L. , Iannitti-Tito Paula , Wickham Geoffrey , Sheil Margaret M.
Published: August 2003

The binding of the antitumor antibiotics, duocarmycin C2 (pyrindamycin A), duocarmycin C1 (pyrindamycin B), hedamycin, and DC92-B to self complementary oligonucleotides (ranging from 6 to 14-mers) has been studied using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The duocarmycins bind via non-covalent interactions in the minor groove of DNA with subsequent alkylation of the N3 atom of adenine. Hedamycin and DC92-B are intercalating, alkylating agents that target the N7 of guanines within 5′-CGT, and to a lesser extent, 5′-CGG sequences. We show here that the site(s) of alkylation by these ligands are strongly influenced by the location of high affinity binding sites within these short oligonucleotides. These data clearly demonstrate value of using ESI-MS/MS to pre-screen ligand–oligonucleotide complexes prior to performing more detailed structural studies, since subtle selectivity differences have been detected by this technique that were not evident from conventional sequencing studies on larger segments of DNA.
Extractability of Polycyclic Aromatic Hydrocarbons in Sediments: A Matter of Association?
Authors: Ahrens Michael J. , Hickey Christopher W.
Published: August 2003

Bioavailability and accumulation of sediment-bound polycyclic aromatic hydrocarbons (PAHs) by benthic biota are closely related to their extractability by water or mild aqueous solvents. Nevertheless, PAH accumulation by benthic organisms is sometimes considerably different from predictions based on an equilibrium partition coefficient KOC between water and bulk sedimentary organic carbon (OC). We present evidence that PAH extractability is strongly affected by the type of OC acting as a sorbent. We compared extractability of spiked [14C]fluoranthene from a variety of natural and man-made OC matrices, including bulk sediment organic carbon, peat moss, power plant fly ash, diesel soot, petroleum/natural gas soot, coal dust, and carbon black. Artificial sediments were prepared from glass beads amended with equal weight percentages (2%) of nine different types of OC. Amended sediments were spiked with [14C]fluoranthene and batch-extracted with seawater and 0.5% sodium dodecyl sulfate (SDS) after 65 and 12 h of equilibration, respectively. Fluoranthene extractability by seawater ranged between 0.03% and 0.9%, corresponding to a 50-fold variation of apparent KOC, and 0.03–18% for SDS. Correlation between seawater and SDS extraction efficiencies was weak, suggesting differences in the mechanism of solubilization. These results demonstrate that use of a single value of KOC to predict bioavailability of fluoranthene should be avoided, and that attempts to extrapolate PAH extractability from water-only extraction experiments to aqueous solutions containing surface-active dissolved organic carbon, such as the gut fluids of deposit feeding macrofauna, is very likely to lead to erroneous predictions.
Position-Addressable Nano-Scaffolds. I. The Preparation of N,O-, N,C- and N,N-Bridged Sesquinorbornadiene Succinimides as Compact, Highly Functionalized Addressable Building Blocks
Authors: Warrener Ronald N. , Margetic Davor , Sun Guangxing , Russell Richard A.
Published: August 2003

Succinimide-functionalized N,O-, N,C-, and N,N-bridged benzo[2]polynorbornanes (benzosesquinorbornadienes) are reported for the first time and are prepared by the cycloaddition of either five-membered cyclic 1,3-dienes onto N-substituted benzo-7-azanorbornadienomaleimides or N-substituted isoindoles onto the appropriate norbornadienomaleimides. These products contain an end-fused norbornene (or a 7-substituted relative) and have been designed to act as alkene BLOCKs for the production of nano-scaffolds with up to six addressable sites supplied by each norbornene unit. The N-bridges in these BLOCKs (and their coupled products) allow N-substituent mobility by invertomerization of the sp3 nitrogen whereas the N-substituents on the succinimides are attached to an sp2 nitrogen atom and remain static. Preferred invertomer geometry can be determined using molecular modelling.
Position-Addressable Nano-Scaffolds. II. The Introduction of One, Two, or Three Addressable Succinimide Linkage Points onto the Under-Surface of ‘Southern’ Cavity Bis-Porphyrins
Authors: Warrener Ronald N. , Sun Hongsui , Johnston Martin R.
Published: August 2003

Cavity bis-porphyrins containing up to three addressable succinimide rings on the underface are reported for the first time. This is achieved by site-selective addition of o-chloranil to the 7-oxanorbornene π-bond of O-bridged sesquinorbornadienosuccinimide (1a) to form a scaffold α-dione, followed by condensation with porphyrindiamine (12) to produce a porphyrin-containing norbornene BLOCK (13) incorporated a succinimide ring fused to the underside. Dual 1,3-dipolar coupling of (13) with alicyclic bis-epoxides (15) formed the cavity bis-porphyrins (16) containing two succinimide rings while similar 1,3-dipolar coupling with succinimide-containing bis-epoxide (17) gave the extended cavity bis-porphyrin (18) having three succinimide rings within the cavity section. A similar cycloaddition/condensation strategy provides the shortest route to cavity bis-porphyrins containing a single succinimide ring yet reported.
Swept-Cavity Ringdown Absorption Spectroscopy: Put Your Laser Light In and Shake It All About
Authors: Shorten Richard A. , He Yabai , Orr Brian J.
Published: August 2003

Cavity ringdown (CRD) absorption spectroscopy with continuous-wave (cw) tunable coherent light sources provides a convenient, sensitive, and precise way to measure very weak optical absorption spectra and to analyze trace gas concentrations. Several recently introduced innovations in cw-CRD spectroscopy are described. Our approach involves one or more single-mode tunable diode laser sources, a rapidly swept ringdown cavity, and a simple optical heterodyne detected approach (based on the dynamics of coherent light reflected from such an active optical cavity). This offers high performance in a relatively simple, low-cost, compact instrument that is facilitated by fibre optic and other standard photonics or telecommunications components. New experimental results are reported, comprising CRD spectra of water vapour in the 0.815 µm wavelength region and of mixtures of CO2 and CO in the range of 1.56–1.59 µm. Promising applications of such techniques include chemical analysis of trace gases in medicine, agriculture, industry, and the environment.
Functionalized Macrocyclic Compounds: Potential Sensors of Small Molecules and Ions
Authors: Bernhardt Paul V. , Moore Evan G.
Published: August 2003

The potential applications of macrocycles in chemistry and at its interfaces with biology and physics continue to emerge, one of which is as receptors for small molecules and ions. This review illustrates these applications with examples from the last ten years employing complexation as the binding mechanism; some of the systems presented have already found real-world sensor applications. In any case, the challenges remain to design more selective and sensitive receptors for guests.
Metal Bioaccumulation and Toxicity in Soils—Why Bother with Speciation?
Authors: Nolan Annette L. , Lombi Enzo , McLaughlin Mike J.
Published: August 2003

This review assesses metal speciation in soils, including analytical techniques used for measurement and the advantages and disadvantages of using chemical speciation information, in both the solid and aqueous phase, to predict adverse effects of metal contamination in soils and for use in soil protection policies. Other techniques used to assess metal lability and bioavailability in soil are also discussed.
The Formation of Fluorescent Alkaline Earth Complexes by 4-{2-[10-(2-Morpholinoethyl)-9-anthryl]methyl}morpholine and its -Ethyl}morpholine and -Propyl}morpholine Analogues in Acetonitrile
Authors: Geue Jason P. , Head Nicholas J. , Ward A. David , Lincoln Stephen F.
Published: August 2003

The formation of fluorescent alkaline earth complexes of 4-{2-[10-(2-morpholinoethyl)9-anthryl]methyl}morpholine and its new -ethyl}morpholine and -propyl}morpholine analogues, L = (1)–(3), in acetonitrile is reported. Each L has a ‘fluorophore–spacer–receptor’ structure in the sequence ‘anthracene–(methylene)n–morpholine’ in which quenching of the anthracene fluorophore becomes less effective as the receptor tertiary nitrogen becomes more distant with an increase in n from 1 to 3. Complexation by the alkaline earths (M2+) modulates photoinduced electron transfer (PET) and enhances the fluorescence of (1)–(3). The two alkyl morpholine receptors of (1)–(3) may either complex M2+ singly to form [ML]2+ and [M2L]4+ or cooperatively to form a [ML′]2+ ‘sandwich’ complex depending on the length of the alkyl spacer. Thus, (1) dominantly forms [ML]2+ and [ML′]2+ while (2) and (3) form all three complexes as exemplified by [Mg(2)]2+ and [Mg(2)′]2+ characterized by the overall complexation constant K1 = 9.19 × 104 dm3 mol−1 and [Mg2(2)]4+ characterized by the stepwise complexation constant K2 = 1.19 × 103 dm3 mol−1 at 298.2 K and I = 0.05 mol dm−3 (NEt4ClO4). The most stable and fluorescent complexes are formed by Mg2+ and Ca2+, consistent with M2+ size being an important factor affecting complex characteristics. Eighteen complexation constants and quantum yields are reported for the (1)–(3) complexes together with those for (1)–(3) alone. In 40 : 60 (v/v) 1,4-dioxan/water, protonation modulates PET to increase the fluorescence of (1)H22+–(3)H22+. (The pKa values for (2)H22+ are 6.38 and 5.62, and for (3)H22+ are 7.00 and 6.25.) The syntheses of (2) and (3) are reported.
Active Barriers to Reduce Phosphorus Release from Sediments: Effectiveness of Three Forms of CaCO3
Authors: Hart Barry T. , Roberts Simon , James Robert , O'Donohue Mark , Taylor Jeff , Donnert Dietfried , Furrer Rüdiger
Published: August 2003

Three forms of calcite—crushed limestone and two forms of precipitated calcite—were tested in laboratory bio-reactors as possible active barriers to prevent phosphorus release from sediments, and therefore reduce the risks due to algal blooms (or eutrophication). The two precipitated calcite materials proved to be quite effective at reducing the release of phosphorus from Lake Carramar sediments under anaerobic conditions. Over a 20-day period, a 2% (1.1 kg (CaCO3) m–2 layer of SoCal (a commercial product from Germany) reduced the amount of phosphorus released by almost 100 times over that occurring with no barrier. The Australian product (ESCal 2%), while not as effective as the SoCal, still reduced the phosphorus released by around 15 times that with no barrier. Limestone was ineffective in preventing the release of phosphorus. Mean phosphorus flux rates under anaerobic conditions were: control 66, SoCal 0.8, and ESCal 2.9 µmol (P) m–2 d–1.
There is considerable scope to further optimize the conditions under which the ESCal calcite is formed to produce a product with smaller particle size and higher surface area than that tested here. Additionally, there is potential to precipitate the ESCal in situ and thus achieve even greater cost savings. Preliminary cost estimates are that it should be possible to dispense calcium hydroxide directly into the water column at around $A 200 per tonne, and then use a CO2 bubbler system to precipitate CaCO3 directly in the water column.
C-Glycosylation of Oxygenated Naphthols with 3-Dimethylamino-2,3,6-trideoxy-L-arabino-hexopyranose and 3-Azido-2,3,6-trideoxy-D-arabino-hexopyranose
Authors: Brimble Margaret A. , Davey Roger M. , McLeod Malcolm D. , Murphy Maureen
Published: August 2003

In connection with studies directed towards the synthesis of the pyranonaphthoquinone antibiotic medermycin, C-aryl glycosides were prepared by C-glycosylation of naphthols with glycosyl donors. Boron trifluoride diethyl etherate proved to be a suitable Lewis acid to promote the C-glycosylation, and use of the azido glycosyl donor proved more successful than using the dimethylamino glycosyl donor. 5-Hydroxy-1,4-dimethoxynaphthalene underwent facile C-glycosylation with two particular glycosyl donors, whereas 3-bromo-5-hydroxy-1,4-dimethoxynaphthalene was not an effective coupling partner with the same glycosyl donors. These studies indicate that subtle steric and electronic effects need to be considered in order to fine-tune C-glycosylations when using highly functionalized glycosyl donors.
2,6-Diazaanthracene-9,10-dione and its Radical Anion— A Structural and Spectroscopic Investigation
Authors: Morgan Joy L. , Flood Amar , Gordon Keith C. , Kjaergaard Henrik G. , Robinson Brian H. , Simpson Jim
Published: August 2003

An analysis of the structure, vibrational and electronic spectra, and the molecular orbitals of 2,6-diazaanthracene-9,10-dione (DAAD) (1) and its radical anion is presented. Strong π-stacking is seen in the crystal structure of (1) and observed bond lengths and angles are in good agreement with those calculated with the B3LYP/6-31G(d) method. The vibrational spectra of (1) show strong bands at 1686 cm–1 (IR) and 1676 cm–1 (Raman) corresponding to the antisymmetric and symmetric C=O stretch, respectively, in good agreement with calculated data. Electrochemical or chemical reduction to (1)•- results in a new spectrum with a strong absorption due to the antisymmetric stretch at 1481 cm–1 (predicted 1470 cm–1). The lowest energy electronic transition for (1) occurs at 317 nm; new transitions at lower energy (403, 573, and 910 nm) are seen in the spectrum of (1)•-. The dark purple radical anion (1)•- was isolated as the Cp2Co+ salt but its ESR spectrum did not display hyperfine coupling.
The Use of Lead Isotopes in Monitoring Environmental Impacts of Uranium and Lead Mining in Northern Australia
Authors: Munksgaard Niels C. , Brazier Jennifer A. , Moir Cristy M. , Parry David L.
Published: August 2003

Lead isotope ratios, determined by inductively coupled plasma quadropole mass spectrometry (ICPMS), have been used to assess environmental impacts from uranium and lead mining in northern Australia. The lead isotope composition of most environmental samples contained evidence of mixing of two or more end-member components; their characteristic lead isotope ratios allowed lead sources to be unambiguously identified. The isotopic characteristics and sources identified include highly radiogenic lead (low 207Pb/206Pb and 208Pb/206Pb ratios) in sediments from the Finniss River derived from the former Rum Jungle uranium mine; relatively non-radiogenic lead (high 207Pb/206Pb and 208Pb/206Pb ratios) in the livers of magpie geese from the Finniss River floodplains, originating from lead ores via ingested lead shot; and relatively non-radiogenic lead in seagrass leaves and oyster soft tissue from the Gulf of Carpentaria resulting from dispersion of small amounts of lead–zinc concentrate from a coastal loading facility.