bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of NO2, SO2, O3, Benzene and Toluene Using Differential Optical Absorption Spectroscopy (DOAS) in Shanghai, China
Authors: Hao Nan , Zhou Bin , Chen Dan , Sun Yi , Gao Song , Chen Limin
Published: June 2006

NO2, SO2, O3, benzene, and toluene were measured in Taopu industry park of Shanghai during the period June to August 2003 by differential optical absorption spectroscopy (DOAS) technique. The daily average concentrations ofSO2, NO2, and O2ranged from 5.7 ppb to 40 ppb, 22 ppb to 123 ppb, and 10.6 ppb to 23 ppb respectively. SO2and NO2concentrations were found to depend on wind direction. The diurnal variation of NO2concentrations had two peaks due to traffic emission. Our DOAS measurements of NO2, SO2and O3were compared with the conventional measurement instruments (API automatic monitoring instrument). The concept of a percent difference (PD) and linear regression methods were employed to study the difference between DOAS and API instruments. The correlation analysis between PD values and meteorological parameters and analysis of abnormal higher absolute PD values indicated that the lower visibility induced the bad compatibility between the two systems. The results showed that both systems exhibited strong compatibility with good correlation, therefore the DOAS system is able to provide reliable information on distribution patterns of major air pollutants. Average benzene and toluene concentrations were 1.4 and 8.0 ppb respectively.
Construction and Performance Characterization of Ionselective Electrodes for Potentiometric Determination of Pseudoephedrine Hydrochloride Applying Batch and Flow Injection Analysis Techniques
Authors: Zayed Sayed. I. M. , Issa Yousry. M. , Hussein Ahmed
Published: June 2006

New pseudoephedrine selective electrodes have been constructed of the conventional polymer membrane type by incorporation of pseudoephedrine‐phosphotungstate (PE‐PT) or pseudoephedrine–silicotungstate (PE‐SiT) ion‐associates in a poly vinyl chloride (PVC) membrane plasticized with dibutyl phthalate (DBP). The electrodes were fully characterized in terms of the membrane composition, temperature, and pH. The electrodes exhibited mean slopes of calibration graphs of 57.09 and 56.10 mV concentration decade‐1 of PECl at 25 °C for (PE‐PT) and (PE‐SiT) electrodes, respectively. The electrodes showed fast, stable, and near‐Nernstian response over the concentration ranges 6.31 × 10‐6−1.00 × 10‐2 and 5.00 × 10‐5 −1.00 × 10‐2 M in the case of PE‐PT applying batch and flow injection (FI) analysis, respectively, and 1.00 × 10‐5‐1.00 × 10‐2 and 5.00 × 10‐5 − 1.00 × 10‐2 M in the case of PE‐SiT for batch and FI analysis system, respectively. Detection limit was 5.01 × 10‐6 M for PE‐PT electrode and 6.31 × 10‐6 M for PE‐SiT electrode. The electrodes were successfully applied for the potentiometric determination of pseudoephedrine hydrochloride (PECl) in pharmaceuticalpreparations with mean recovery 101.13 ± 0.85 % and 100.77 ± 0.79 % in case of PE‐PT applying batch and flow injection systems, respectively, and 100.75 ± 0.85 % and 100.79 ± 0.77 % in case of PE‐SiT for batch and flow injection systems, respectively. The electrodes exhibited good selectivity for PECl with respect to a large number of inorganic cations, sugars and amino acids.
Distribution and Determination of Pb, Cd, Bi and Cu in the Sea Brine System: Solution ‐ Colloidal Particles – Biota
Authors: Bozhkov Ognyan , Tzvetkova Christina , Russeva Elena
Published: June 2006

The distribution of Pb, Cd, Bi, and Cu in Black Sea brine system (solution ‐ colloidal particles – biota) produced in Burgas and Pomorie salterns is studied. The established distribution of the title elements among the brine components is as follows: Pb ‐ 25 % in the salt solution, 30 % ‐ in colloidal particles, 45 % ‐ in biota (Halobacterium salinarium and microalgae Dunaliela salina); Cu – 30 % in the salt solution, 22 % ‐ in colloidal particles, 48 % ‐ in biota. Cd and Bi are not detected in biota. They are uniformly distributed (50 %: 50 %) between the salt solution and colloidal particles. Two procedures for analysis are developed. The first one is designed for determination of the total content of the studied metals in brine. It involves elimination of the biota interference by addition of ethanol, extraction and pre‐concentration of the metals with NaDDC into CCl4 followed by FAAS determination. The second procedure intends determination of the elements in the separate components of the brine. It involves separation of the colloidal particles through centrifugation, separation of the studied elements from the resulting solution as dithiocarbamate complexes on a Millipore filter, dissolution of the retained metal species and subsequent FAAS analysis.
Characterization of the Thermal Decomposition and Polymerization of Arprocarb Using Pyrolysis‐GC‐MS
Authors: Wang Guoqing , Sun Yu'an , Zhang Rongjie , Xie Kui , Liu Hongli
Published: June 2006

Arprocarb is a carbamate type insecticide used to control cockroaches, flies, mosquitoes, and is a lawn and turf insect growth regulator. In order to evaluate the effects of the thermal behavior of arprocarb on its bioactivity or the environment, its thermal decomposition and polymerization were characterized using pyrolysis‐GC‐MS (Py‐GC‐MS). Arprocarb was pyrolysed at 450 °C, 600 °C, 750 °C, and 900 °C, respectively. In all 71 components were determined. It was found that arprocarb was obviously decomposed when the temperature was lower (450∼750 °C), and a large number of mono‐ and polycyclic aromatic hydrocarbons (PAHs) were produced at higher temperatures (750∼900 °C). Furthermore, the variety of the representative compounds versus the temperature was reported. The research results can provide useful information for the understanding of the thermal behavior of arprocarb.
Studies and Application of Catalytic Kinetic Spectrophotometric Determination of Trace Chromium(VI) Sensitized by Microemulsion Medium
Authors: Wei Qin , Duan Caihong , Wang Jin , Ma Hongmin , Du Bin
Published: June 2006

A new catalytic kinetic spectrophotometric method for the determination of trace amount of chromium (VI) in microemulsion medium has been developed. The method is based on the catalytic effect of chromium (VI) on the oxidation of nuclear fast red in the presence of Tween‐80 microemulsion and HAc‐NaAc buffer solution (pH = 5.2). The linear ranges are in the range of 0 ∼ 0.0480 μg mL‐1 of Cr (VI) at 528 nm and the detection limit is 1.56 × 10‐9g mL‐1. The method has been applied in determination of Cr (VI) in water and food samples with satisfactory results. The relative standard deviation is less than 4.6 % and the recovery is 93.5 ∼ 104 %.
Use of a Glass Residue in the Removal of Heavy Metals from Wastewater
Authors: Catalfamo Paola , Primerano Patrizia , Arrigo Ileana , Corigliano Francesco
Published: June 2006

The extraction of silica from powdered glass cullet with an aqueous solution of sodium hydroxide has been proposed as an alternative to glass recycling aimed to the low temperature production of sodium silicates. The unextracted residue obtained after a counter current two‐step extractive process at ≅ 100 °C and room pressure is mainly made of calcium and sodium silicate and shows high porosity and a large surface area. We thought that it could be active as an agent for the removal of heavy metals from wastewater. In this paper the capacity of the unextracted residue of removing six metal ions (i.e., Cu2+, Ni2+, Zn2+, Cd2+, Pb2+ e Cr3+) was studied in a stirred batch reactor. The data obtained demonstrate that the removal of metal ions from wastewater is achieved with high capacity in a short time and their concentration is lowered under the legal limits without any appreciable influence from changes of physical and chemical conditions. Sodium and calcium ions take the place of heavy metals in water while pH keeps almost neutral. The exchange mechanism was identified.
Osmium‐Catalyzed Olefin Dihydroxylation and Aminohydroxylation in the Second Catalytic Cycle
Authors: Wu Peng , Hilgraf Robert , Fokin Valery V.
Published: June 2006

Two catalytic cycles operate in the osmium‐catalyzed olefin dihydroxylation and aminohydroxylation. Slow hydrolysis of the Os(VI) monoglycolate (or monoazaglycolate in aminohydroxylation) intermediate often results in the addition of another molecule of olefin thereby shunting the catalysis into the second catalytic cycle. As a result, both enantio‐ and chemoselectivity are reduced. A series of new chelating ligands were devised, which force the catalysis into the second cycle while maintaining enantiocontrol in the olefin addition step. Excellent catalytic turnover and moderate to good enantioselectivity were achieved.
A Novel Chemoentrapment Approach for Supportless Recycling of a Catalyst: Catalytic Asymmetric Dihydroxylation
Authors: Lee Daewon , Lee Honggeun , Kim Seyoung , Yeom Chang‐Eun , Kim B. Moon
Published: June 2006

A simple method of recycling a metal catalyst through chemoentrapment in an aqueous layer using ethyl vinyl ether has been developed. Using this new methodology, a highly efficient, filtration‐free recycling of osmium for catalytic asymmetric dihydroxylation was accomplished. By means of the formation of a water‐soluble OsO42− using EVE, AD reactions of mono‐ and disubstituted olefins with 1 mol % of OsO4 proceeded for up to 9 cycles without any loss of yields and enantioselectivities.
Practical by Ligand Design: A New Class of Monodentate Phosphoramidite Ligands for Rhodium‐Catalyzed Enantioselective Hydrogenations
Authors: Zhao Baoguo , Wang Zheng , Ding Kuiling
Published: June 2006

A new class of low‐cost and easy‐to‐prepare monodentate phosphoramidite ligands (CydamPhos) has been developed from readily accessible and cheap trans‐1,2‐diaminocyclohexane as starting material through a three‐step transformation. This type of ligands exhibited excellent enantioseletivities and high activities in rhodium(I)‐catalyzed asymmetric hydrogenations of dehydro‐α‐amino acid methyl esters 9 (ee: 96.2–99.8 %) and acetylenamides 11 (91.8–98.8 %). The remarkable substituent effects exhibited by the ligands on the enantioselective control of the catalysis are rationalized on the basis of molecular structure of the catalyst precursor.
Cascade Reactions: Sequential Homobimetallic Catalysis Leading to Benzofurans and β,γ‐Unsaturated Esters
Authors: Gabriele Bartolo , Mancuso Raffaella , Salerno Giuseppe , Costa Mirco
Published: June 2006

The concatenation between a Pd(0)‐promoted deallylation catalytic cycle and a Pd(II)‐promoted heterocyclization catalytic cycle (an example of what we have named “sequential homobimetallic catalysis”) has been shown to occur starting from 1‐(2‐allyloxyphenyl)‐2‐yn‐1‐ols 1 to afford 2‐benzofuran‐2‐ylacetic esters 2 and β,γ‐unsaturated esters in high yields under carbonylative conditions. In view of the conceptual as well as the synthetic importance of the process, the mechanistic aspects and the synthetic scope of the reaction have been investigated in detail. All the experimental evidence is in agreement with the sequential homobimetallic mechanism, and the reaction has proven to be of general synthetic applicability.
Practical Syntheses of Both Enantiomers of Cyclopropylglycine and of Methyl 2‐Cyclopropyl‐2‐N‐Boc‐iminoacetate
Authors: Larionov Oleg V. , de Meijere Armin
Published: June 2006

A facile three‐step synthesis of racemic cyclopropylglycine in multigram quantities from inexpensive cyclopropyl methyl ketone has been elaborated. Enzymatic hydrolysis of the N‐Boc‐protected methyl ester of cyclopropylglycine 9 with the inexpensive enzyme papain from Carica papaya affords both enantiomers of cyclopropylglycine (8) with enantiomeric excesses of 99 % or better after deprotection under acidic conditions. Furthermore, the new cyclopropyl group‐containing building block methyl 2‐cyclopropyl‐2‐N‐Boc‐iminoacetate (13) was prepared by N‐chlorination and subsequent dehydrochlorination with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU). Addition of nucleophiles to 13 offers a ready access to an unusual, orthogonally bisprotected α,α‐diamino acid derivative and interesting components of rigid peptide backbones.
An Effective Bismuth‐Catalyzed Benzylation of Arenes and Heteroarenes
Authors: Rueping Magnus , Nachtsheim Boris J. , Ieawsuwan Winai
Published: June 2006

A highly efficient Bi(OTf)3‐catalyzed benzylation of arenes and heteroarenes has been developed. The mild reaction conditions, high yields, operational simplicity and practicability, broad scope, and remarkably low catalyst loading render this environment friendly process an attractiv approach to diarylmethane derivatives. The extension to an intramolecular variant of this procedure provides a valuable route to substituted fluorenes.
Recent Progress in Chiral Brønsted Acid Catalysis
Authors: Akiyama Takahiko , Itoh Junji , Fuchibe Kohei
Published: June 2006

Hydrogen bond catalysis and Brønsted acid catalysis are rapidly growing areas in organocatalysis. A number of chiral acid catalysts has been developed recently. Recent progress in the chiral Brønsted acid catalysis has been reviewed with a focus being placed on thiourea, TADDOL, and phosphoric acids. 1  Introduction 2  Hydrogen Bond Catalysis 2.1 Monofunctional Thiourea Catalysts 2.2 Bifunctional Thiourea Catalysts 2.3 TADDOL Derivatives 2.4 BINOL Derivatives 3  Brønsted Acid Catalysis 3.1 Ammonium Salts 3.2 Phosphoric Acids 4  Conclusion
Chemische Fortbewegung
Authors: Paxton Walter F. , Sundararajan Shakuntala , Mallouk Thomas E. , Sen Ayusman
Published: June 2006

Forschungen zur eigenständigen Bewegung künstlicher Mikro‐ und Nanoobjekte bilden die Grundlage für mögliche Anwendungen wie die Selbstorganisation von Überstrukturen, bewegliche Sensoren oder den Wirkstofftransport. Zwar unterscheiden sich die Antriebsmechanismen der beschriebenen Systeme, in jedem Fall beruht die Bewegung aber auf der lokalen Umwandlung von chemischer Energie in mechanische Energie. Der Einsatz von Katalysatoren, die direkt in die Objekte integriert werden, erzeugt nichtdissipative Systeme, die sich zielgerichtet bewegen können. Entscheidend beim Aufbau von Nano‐ und Mikromotoren ist die asymmetrische Platzierung des Katalysators, da diese zu einem ungleichmäßigen Verbrauch des Substrats und einer ungleichmäßigen Verteilung der Reaktionsprodukte führt, die schließlich in eine Bewegung umgesetzt werden. Die Natur nutzt die gleichen Konzepte, um selbständige Bewegung zu ermöglichen.
Titelbild: Bildung von selbstorganisierten dynamischen Strukturmustern von Bariumcarbonatkristallen bei der polymerkontrollierten Kristallisation (Angew. Chem. 27/2006)
Authors: Wang Tongxin , Xu An‐Wu , Cölfen Helmut
Published: June 2006

Die Belousov‐Zhabotinsky‐Reaktion mit ihrem typischen konzentrischen Ringmuster wurde erstmals für eine Fällungsreaktion beschrieben. Die Bildung und Selbstorganisation von BaCO3‐Nanopartikeln kann mit einem neuen phosphonierten Blockcopolymer von ultralangen zu kurzen Nanofasern und letztlich zum konzentrischen B‐Z‐Ringmuster gesteuert werden. Dies könnte helfen, natürliche Musterbildung zu erklären. Das Titelbild zeigt beobachtete und simulierte B‐Z‐Muster sowie das Blockcopolymer. Mehr Details finden sich in der Zuschrift von A.‐W. Xu, H. Cölfen und T. Wang auf S. 4561 ff.
Chemical Locomotion
Authors: Paxton Walter F. , Sundararajan Shakuntala , Mallouk Thomas E. , Sen Ayusman
Published: June 2006

Research into the autonomous motion of artificial nano‐ and microscale objects provides basic principles to explore possible applications, such as self‐assembly of superstructures, roving sensors, and drug delivery. Although the systems described have unique propulsion mechanisms, motility in each case is made possible by the conversion of locally available chemical energy into mechanical energy. The use of catalysts onboard can afford nondissipative systems that are capable of directed motion. Key to the design of nano‐ and micromotors is the asymmetric placement of the catalyst: its placement in an environment containing a suitable substrate translates into non‐uniform consumption of the substrate and distribution of reaction products, which results in the motility of the object. These same principles are exploited in nature to effect autonomous motion.
Ingestion of Hijiki seaweed and risk of arsenic poisoning
Authors: Nakajima Yoshiaki , Endo Yoko , Inoue Yoshinori , Yamanaka Kenzo , Kato Koichi , Wanibuchi Hideki , Endo Ginji
Published: June 2006

The major route of human exposure to arsenic is via ingestion. Seafoods contain large amounts of various arsenic compounds. Recently, people have been advised not to eat Hijiki seaweed (Hijikia fusiforme) in the UK because of its high content of inorganic arsenic (iAs). To clarify the risks of Hijiki ingestion, a 42‐year‐old male volunteer ingested 825 µg of iAs compounds contained in eight servings of commercial Hijiki food, after refraining from eating seafood for 3 months. In order to determine the distribution of arsenic species in his urine, arsenic compounds were analyzed using HPLC‐ICP‐MS. The maximum concentrations of arsenate (AsV), arsenite (AsIII), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were found at 4, 6.5, 13 and 17.5 h after ingestion, respectively. Arsenobetaine concentration was very low, and almost constant throughout the observation period. A total of 28% of ingested arsenic was excreted in urine. The total amounts of AsV, AsIII, MMA and DMA excreted in urine over 50 h were 11.2, 31.8, 40.9 and 104.0 µg, respectively. After eating one serving of Hijiki, arsenic intake and urinary excretion were at levels similar to those in individuals affected by arsenic poisoning. Long‐term ingestion of Hijiki might thus have the potential to cause arsenic poisoning. Copyright © 2006 John Wiley & Sons, Ltd.
Homoleptic lanthanide amidinate complexes: A single‐component initiator for ring‐opening polymerization of trimethylene carbonate and copolymerization with ϵ‐caprolactone
Authors: Li Cheng , Wang Yaorong , Zhou Liying , Sun Hongmei , Shen Qi
Published: June 2006

The ring‐opening polymerization of trimethylene carbonate (TMC) using homoleptic lanthanide amidinate complexes [CyNC(R)NCy]3Ln as single component initiators has been fully investigated for the first time. The substituents on amidinate ligands and center metals show great effect on the catalytic activities of these complexes, that is, Me > Ph, and La > Nd > Sm > Yb. Among them, [CyNC(Me)NCy]3La shows the highest catalytic activity. Some features of the TMC polymerization initiated by [CyNC(Me)NCy]3La were studied in detail. A mechanism that the polymerization occurs via acyl‐oxygen bond cleavage rather than alkyl‐oxygen bond cleavage was proposed. The copolymerization of TMC with ϵ‐caprolactone initiated by [CyNC(Me)NCy]3La was also tested. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 22–28, 2006
Preparation of core/shell PVP/PLA ultrafine fibers by coaxial electrospinning
Authors: Sun Bin , Duan Bin , Yuan Xiaoyan
Published: June 2006

This study investigated the process feasibility and stability of core/shell structured bicomponent ultrafine fibers of poly(vinyl pyrrolidone) (PVP) and poly(D,L‐lactide) (PLA) by coaxial electrospinning. The morphological structure of the core/shell ultrafine fibers was studied by means of scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Results suggested that PVP/PLA core/shell ultrafine fibers with drawbacks could be produced from 6 or 8% PVP solutions (inner) in the mixture of N,N‐dimethlformamide (DMF) and ethanol and a 22% PLA solution (outer) in DMF and acetone when the flow rates of inner and outer fluids were 0.05 and 0.1 mL/h, respectively. The tensile modulus and tensile strength of the core/shell PVP/PLA membrane were dramatically lower than those of the electrospun PLA membrane, and its water uptake was twice more than that of the PLA membrane. Membranes made from the biodegradable core/shell ultrafine fibers could be potentially used in loading bioactive molecules for tissue regeneration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 39–45, 2006
Overcoming the thermodynamic limitation in asymmetric hydrogen transfer reactions catalyzed by whole cells
Authors: Goldberg Katja , Edegger Klaus , Kroutil Wolfgang , Liese Andreas
Published: June 2006

Whole lyophilized cells of an Escherichia coli overexpressing the alcohol dehydrogenase (ADH‐‘A’) from Rhodococcus ruber DSM 44541 were used for the asymmetric reduction of ketones to secondary alcohols. The recycling of the required nicotinamide cofactor (NADH) was achieved in a coupled‐substrate process. In the course of the reaction the ketone is reduced to the alcohol and the hydrogen donor 2‐propanol is oxidized to acetone by one enzyme. This leads to a thermodynamic equilibrium between all four components determining the maximum achievable conversion. To overcome this limitation an in situ product removal technique (ISPR) for the application with whole cells was developed. In this method the most volatile compound is separated from the reaction vessel by an air flow resulting in a shift of the equilibrium towards the desired secondary alcohol. The so‐called stripping process represents a simple and efficient method to overcome the thermodynamic limitation in biocatalytic reactions. Employing this method, the conversion of selected biotransformations was increased up to completeness. © 2006 Wiley Periodicals, Inc.
Characterization of sol‐gel entrapped chlorophyllase
Authors: Yi Yunyu , Kermasha Selim , Neufeld Ronald
Published: June 2006

Immobilization of membrane proteins remains a challenge compared to soluble proteins. The membrane protein—chlorophyllase was successful entrapped in tetramethoxysilane (TMOS)‐based sol‐gel in the presence of lipid. Activity was examined against mixing rate, incubation temperature, time, substrate, acetone, and canola oil concentration. The external mass transfer of chlorophyll is not the rate‐limiting step at higher mixing rates. Stability against temperature and acetone as denaturant was enhanced. In spite of the fact that an initial reaction lag phase was observed, 20% more chlorophyll was hydrolyzed, compared to reaction with free enzyme by the end of a 12 h assay. The initial lower activity demonstrated by entrapped chlorophyllase is likely due to the diffusion resistance of chlorophyll into and within the entrapment matrix. This hypothesis was substantiated by a low diffusion coefficient on the order of 10−14 m2/s obtained for chlorophyll in nanoporous sol‐gel particles. Pore size distribution of nanoporous wet TMOS‐based sol‐gel with or without protein was determined by thermoporometry. The change in pore morphology upon doping with chlorophyllase suggests that protein acts as a template during the sol‐gel process. © 2006 Wiley Periodicals, Inc.
A Unique Mechanism for Methyl Ester Formation via an Amide Intermediate Found in Myxobacteria
Authors: Müller Inga , Weinig Stefan , Steinmetz Heinrich , Kunze Birgitte , Veluthoor Sheeba , Mahmud Taifo , Müller Rolf
Published: June 2006

Secondary metabolism involves a broad diversity of biochemical reactions that result in a wide variety of biologically active compounds. Terminal amide formation during the biosynthesis of the myxobacterial electron‐transport inhibitor, myxothiazol, was analyzed by heterologous expression of the unique nonribosomal‐peptide synthetase, MtaG, and incubation with a synthesized substrate mimic. These experiments provide evidence that the terminal amide is formed from a carrier protein‐bound myxothiazol acid that is thioesterified to MtaF. This intermediate is transformed to an amide by extension with glycine and subsequent oxidative cleavage by MtaG. The final steps of melithiazol assembly involve a highly similar protein‐bound intermediate (attached to MelF, a homologue of MtaF), which is transformed to an amide by MelG (homologue of MtaG). In this study, we also show that the amide moiety of myxothiazol A can be hydrolyzed in vivo to the formerly unknown free myxothiazol acid by heterologous expression of melJ in the myxothiazol producer Stigmatella aurantiaca DW4/3‐1. The methyltransferase MelK can finally methylate the acid to give rise to the methyl ester, which is produced as the final product in the melithiazol A biosynthetic pathway. These experiments clarify the role of MelJ and MelK during melithiazol assembly.
Resonance Structures of the Amide Bond: The Advantages of Planarity
Authors: Mujika Jon I. , Matxain Jon M. , Eriksson Leif A. , Lopez Xabier
Published: June 2006

Delocalization indexes based on magnitudes derived from electron‐pair densities are demonstrated to be useful indicators of electron resonance in amides. These indexes, based on the integration of the two‐electron density matrix over the atomic basins defined through the zero‐flux condition, have been calculated for a series of amides at the B3LYP/6‐31+G* level of theory. These quantities, which can be viewed as a measure of the sharing of electrons between atoms, behave in concordance with the traditional resonance model, even though they are integrated in Bader atomic basins. Thus, the use of these quantities overcomes contradictory results from analyses of atomic charges, yet keeps the theoretical appeal of using nonarbitrary atomic partitions and unambiguously defined functions such as densities and pair densities. Moreover, for a large data set consisting of 24 amides plus their corresponding rotational transition states, a linear relation was found between the rotational barrier for the amide and the delocalization index between the nitrogen and oxygen atoms, indicating that this parameter can be used as an ideal physical‐chemical indicator of the electron resonance in amides.
An Experimental and Theoretical Investigation of Gas‐Phase Reactions of Ca2+with Glycine
Authors: Corral Inés , Mó Otilia , Yáñez Manuel , Salpin Jean‐Yves , Tortajada Jeanine , Moran Damian , Radom Leo
Published: June 2006

The gas‐phase reactions between Ca2+and glycine ([Ca(gly)]2+) have been investigated through the use of mass spectrometry techniques and B3‐LYP/cc‐pWCVTZ density functional theory computations. The major peaks observed in the electrospray MS/MS spectrum of [Ca(gly)]2+correspond to the formation of the [Ca,C,O2,H]+, NH2CH2+, CaOH+, and NH2CH2CO+fragment ions, which are produced in Coulomb explosion processes. The computed potential energy surface (PES) shows that not only are these species the most stable product ions from a thermodynamic point of view, but they may be produced with barriers lower than for competing processes. Carbon monoxide is a secondary product, derived from the unimolecular decomposition of some of the primary ions formed in the Coulomb explosions. In contrast to what is found for the reactions of Ca2+with urea ([Ca(urea)]2+), minimal unimolecular losses of neutral fragments are observed for the gas‐phase fragmentation processes of [Ca(gly)]2+, which is readily explained in terms of the topological differences between their respective PESs.
Diels–Alder Ligation of Peptides and Proteins
Authors: de Araújo Aline Dantas , Palomo Jose M. , Cramer Janina , Seitz Oliver , Alexandrov Kirill , Waldmann Herbert
Published: June 2006

The development of the Diels–Alder cycloaddition as a new method for the site‐specific chemoselective ligation of peptides and proteins under mild conditions is reported. Peptides equipped with a 2,4‐hexadienyl ester and an N‐terminal maleimide react in aqueous media to give cycloadducts in high yields and depending on the amino acid sequence with high stereoselectivity. Except for the cysteine SH group the transformation is compatible with all amino acid side chain functional groups. For ligation to proteins the hexadienyl group was attached to avidin and streptavidin noncovalently by means of complex formation with a biotinylated peptide or by covalent attachment of a hexadienyl ester‐containing label to lysine side chains incorporated into the proteins. Site‐specific attachment of the hexadienyl unit into a Rab protein was achieved by means of expressed protein ligation followed by protection of the generated cysteine SH by means of Ellman's reagent. The protein reacted with different maleimido‐modified peptides under mild conditions to give the fully functional cycloadducts in high yield. The results demonstrate that the Diels–Alder ligation offers an advantageous and technically straightforward new opportunity for the site‐specific equipment of peptides and proteins with further functional groups and labels. It proceeds under very mild conditions and is compatible with most functional groups found in proteins. Its combination with other ligation methods, in particular expressed protein ligation is feasible.
Cover Picture: Ethylene Oligomerisation and Polymerisation with Nickel Phosphanylenolates Bearing Electron‐Withdrawing Substituents: Structure–Reactivity Relationships (Chem. Eur. J. 20/2006)
Authors: Kuhn Pierre , Sémeril David , Jeunesse Catherine , Matt Dominique , Neuburger Markus , Mota Antonio
Published: June 2006

A variety of SHOP‐type catalysts, in which the CC(O) double bond of nickel phosphanylenolates [Ni{Ph2PC(R1)C(R2)O}Ph(PPh3)] was substituted by electron‐withdrawing substituents, were assessed as ethylene‐ oligomerization and ‐polymerization catalysts and compared with Keim's complex [Ni{Ph2PCHC(Ph)O}Ph(PPh3)] (1). Regardless of their relative electron‐withdrawing strength, all of these substituents induced an increase in activity with respect to 1. A rationale for the influence of the double‐bond substituents of the P,O‐chelate unit on the catalytic properties is proposed by Matt et al. in their Full Paper on page 5210 ff.
Individual cell‐based models of the spatial‐temporal organization of multicellular systems—Achievements and limitations
Authors: Galle J. , Aust G. , Schaller G. , Beyer T. , Drasdo D.
Published: June 2006

Computational approaches of multicellular assemblies have reached a stage where they may contribute to unveil the processes that underlie the organization of tissues and multicellular aggregates. In this article, we briefly review and present some new results on a number of 3D lattice free individual cell‐based mathematical models of epithelial cell populations. The models we consider here are parameterized by bio‐physical and cell‐biological quantities on the level of an individual cell. Eventually, they aim at predicting the dynamics of the biological processes on the tissue level. We focus on a number of systems, the growth of cell populations in vitro, and the spatial‐temporal organization of regenerative tissues. For selected examples we compare different model approaches and show that the qualitative results are robust with respect to many model details. Hence, for the qualitative features and largely for the quantitative features many model details do not matter as long as characteristic biological features and mechanisms are correctly represented. For a quantitative prediction, the control of the bio‐physical and cell‐biological parameters on the molecular scale has to be known. At this point, slide‐based cytometry may contribute. It permits to track the fate of cells and other tissue subunits in time and validated the organization processes predicted by the mathematical models. © 2006 International Society for Analytical Cytology
Toward complete laser ablation of melanoma contaminant cells in a co‐culture outgrowth model via image cytometry
Authors: Shen Feimo , Price Jeffrey H.
Published: June 2006

Background:

Contaminant cancer cells in autologous transplant tissue can cause relapse and the rates are unknown. A method capable of removing all contaminant cells with a high probability detected by cytomic analyses would be useful. Neither 100% cell purging nor techniques for measuring the probability of success have been developed. Here, we report a method for removing 100% of the cells under ideal staining conditions and quantify the probability of success.

Methods:

Laser ablation was combined with previously reported automated microscopy to purge contaminant cells and evaluate 100% ablation in a co‐culture model of prestained mouse melanoma cells mixed with mouse NIH‐3T3 cells. Melanoma passage efficiency was measured by: (1) micropipetting single cells into microtiter wells and (2) ablating all but one melanoma cell in co‐cultures.

Results:

(74 ± 5)% of single melanoma cells pipetted into microtiter plate wells divided at least once. With ablation of all but one contaminant cell in co‐cultures, melanoma dominated in (62 ± 8)% cultures in 21 days. With 100% ablation in six additional experiments, no melanoma outgrowth was observed, giving a >99.1% probability that all contaminant melanoma cells were purged.

Conclusions:

We successfully demonstrated a model for complete ablation within a defined probability using automated high‐content image cytometry with ideal staining conditions. The results show that the instrumentation is capable of delivering 100% ablation at a defined probability and establishes the basis for further studies with clinical models wherein pretherapeutic cytomic analyses of unique cellular expression and/or morphological characteristics will be key for contaminant cancer cell identification. © 2006 International Society for Analytical Cytology
Scanning cytometry with a LEAP: Laser‐enabled analysis and processing of live cells in situ
Authors: Szaniszlo Peter , Rose William A. , Wang Nan , Reece Lisa M. , Tsulaia Tamara V. , Hanania Elie G. , Elferink Cornelis J. , Leary James F.
Published: June 2006

Background:

Scanning cytometry now has many of the features (and power) of multiparameter flow cytometry while keeping its own advantages as an imaging technology. Modern instruments combine capabilities of scanning cytometry with the ability to manipulate cells. A new technology, called LEAP™ (laser‐enabled analysis and processing), offers a unique combination of capabilities in cell purification and selective macromolecule delivery (optoinjection).

Methods:

LEAP‐mediated cell purification and optoinjection effects were assessed in model experiments using adherent and suspension cell types and cell mixtures plated and processed at different densities. Optoinjection effects were visualized by delivering fluorescent dextrans into cells. Results were analyzed using the LEAP instrument's own imaging system as well as by fluorescence and confocal microscopy.

Results:

Live cell samples (adherent and suspension) could be purified to 90–100% purity with 50–90% yield, causing minimal cell damage depending on the cell type and plating density. Nearly one hundred percent of the targeted cells of all cell types examined could be successfully optoinjected with dextrans of 3–70 kDa, causing no visual damage to the cells. Indirect optoinjection effects were observed on untargeted cells within 5–60 μm to targeted areas under conditions used here.

Conclusions:

LEAP provides solutions in cell purification and targeted macromolecule delivery for traditional and challenging applications where other methods fall short. © 2006 International Society for Analytical Cytology
Quality assessment of confocal microscopy slide‐based systems: Instability
Authors: Zucker Robert M.
Published: June 2006

Background:

All slide‐based fluorescence cytometry detections systems basically include an excitation light source, intermediate optics, and a detection device (CCD or PMT). Occasionally, this equipment becomes unstable, generating unreliable and inferior data.

Methods:

A number of tests have been devised to evaluate equipment performance and instability. The following four instability tests are described: galvanometer scanning, stage drift, correct wavelength spectral detection, and long‐term laser power.

Results:

Quality assurance tests revealed that a confocal microscope can become unstable in the following parameters, yielding inaccurate data: laser power, PMTs functionality, spectrophotometer accuracy, galvanometer scanning and laser stability, and stage drift. Long‐term laser power stability has been observed to vary greatly.

Conclusions:

Confocal systems can become unstable in the following parameters: long‐term laser power, galvanometer scanning, spectrophotometer accuracy, and stage stability. Instability in any of these parameters will affect image quality. Laser power fluctuations result from either a defective Acousto‐optic tunable filter or improper heat dissipation. Spectrophotometer instability will generate unreliable spectra data, extra light reflections, and poor image quality. Galvanometer scanning instability yields poor image quality while microscope stage drift results in a sample going out of the plane of focus. With minor modifications, these tests may be applicable to other slide‐based systems. © 2006 International Society for Analytical Cytology
Quality assessment of confocal microscopy slide based systems: Performance
Authors: Zucker Robert M.
Published: June 2006

Background:

All fluorescence slide‐based cytometry detections systems basically include the following components: (1) an excitation light source, (2) intermediate optics, and (3) a detection device consisting of a CCD camera or a PMT. The optical principles employed is slide‐based systems are similar to those of confocal microscopes (CLSM).

Methods:

The following tests evaluated confocal equipment performance: dichroic reflectivity, field illumination, lens performance, laser power output, spectral registration, axial resolution, PMT reliability, and system noise.

Results:

Quality assurance tests provide a basis to determine if the equipment is operating correctly. Laser power, PMTs function, dichroic reflection, spectral registration, axial registration, system noise and sensitivity, lens performance and laser stability were tested colocalization of UV and visible peaks of a bead should be less than 210 nm. Interference contrast optics decrease fluorescence resolution.

Conclusions:

QA tests that assess CLSM system performance are also applicable to other slide‐based systems. By utilization this type of testing approach, the subjective nature of assessing the CLSM may be eliminated. These tests serve as guidelines for other investigators to ensure that their machines are providing data that is accurate with the necessary resolution, sensitivity and precision. © 2006 International Society for Analytical Cytology
Slide‐based cytometry for cytomics—A minireview
Authors: Tárnok Attila
Published: June 2006

In the postgenomic era, to gain the most detailed quantitative data from biological specimens has become increasingly important in the emerging new fields of high‐content and high‐throughput single‐cell analysis for systems biology and cytomics. Areas of research and diagnosis with the demand to virtually measure “anything” in the cell include immunophenotyping, rare cell detection and characterization in the case of stem cells and residual tumor cells, tissue analysis, and drug discovery. Systemic analysis is also a prerequisite for predictive medicine by genomics, proteomics, and cytomics.

This issue of Cytometry Part A is dedicated to innovative concepts of system wide single cells analysis and manipulation, new technologies, data analysis and display, and, finally, quality assessment. The manuscripts to these chapters are provided by cutting edge experts in the fields. This overview will briefly highlight the most important aspects of this continuously developing field. © 2006 International Society for Analytical Cytology
A Ruthenium(II) Complex with a Tripodal Ligand Containing Three Imidazole Groups
Authors: Yamaguchi Tomoka , Harada Kazutoshi , Sunatsuki Yukinari , Kojima Masaaki , Nakajima Kiyohiko , Matsumoto Naohide
Published: June 2006

The orange [RuII(H3L)](ClO4)2·3H2O (1) complex was synthesized from cis‐[RuCl2(dmso)4] and H3L, where H3L (tris{[2‐{(imidazol‐4‐yl)methylidene}amino]ethyl}amine) is a tripodal ligand obtained by condensation of tris(2‐aminoethyl)amine and 4‐formylimidazole in a 1:3 mol ratio. The X‐ray crystal structure analysis revealed that the complex has an octahedral structure coordinated by three imidazole nitrogen atoms and three Schiff base (imine) nitrogen atoms. The uncoordinated NH groups of the imidazole moieties of 1 are easily deprotonated by the action of a base. The effect of deprotonation on the RuIII/RuII redox potential was studied by cyclic voltammetry in methanol containing 0.1 M LiClO4. Complete deprotonation shifts the RuIII/RuII potential to a much more negative value from –0.18 to –0.72 V vs. Ag/Ag+, making it easier to oxidize. The bluish‐purple RuIII complex, [RuIII(H3L)]3+, was formed by controlled‐potential electrolysis of 1, and the electronic spectrum is reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Metal Atom Vibrational Amplitudes in Decamethylferrocene and Related Organometallics
Authors: Herber Rolfe H. , Nowik Israel , Kahlenberg Volker , Kopacka Holger , Schottenberger Herwig
Published: June 2006

Recent experiments have shown that root‐mean‐square amplitudes‐of‐vibration (rmsav) for iron atoms in organometallic complexes at various temperatures can be extracted from temperature‐dependent 57Fe Mössbauer spectroscopic data related to the recoil‐free fraction of the metal atom. The applicability of this procedure has been validated by comparison with rmsav data extracted from Uij values obtained from single‐crystal X‐ray diffraction parameters at various temperatures. This analysis has been applied in detail to a study of decamethylferrocene (DMFc), for which the agreement between the rmsav values derived from the two experimental procedures is compared in the present study. A comparison of these rmsav values for a number of related structures is also reported over a similar temperature range. An improved method for the quantitative preparation of isotopically enriched DMFc is described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Simultaneous Regio‐ and Enantiodifferentiation in Carbohydrate Coupling
Authors: Cid M. Belén , Alonso Inés , Alfonso Francisco , Bonilla Julia B. , López‐Prados Javier , Martín‐Lomas Manuel
Published: June 2006

The glycosylation of 1,2‐trans‐diequatorial diols derived from tetrabenzoylated and tetrabenzylated D‐ and L‐chiro‐inositol with several glycosyl donors has been investigated. An unprecedented dependence of the regioselectivity on the absolute configuration of the acceptor has been found. However this trend is also modulated by the nature of the protecting groups on both the donor and acceptor, with benzoylated acceptors affording higher levels of regioselectivity. Most of the results have been rationalized by DFT calculations which indicate that stereoelectronic factors and hydrogen bonding between the donor and acceptor govern their relative orientation and determine the regiochemical outcome of the process. These studies also highlight the role of the acyl group adjacent to the OH to be glycosylated in facilitating the glycosylation reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Synthesis of cis‐ and trans‐Fused Bicyclic Sugar Amino Acids
Authors: Risseeuw Martijn D. P. , Grotenbreg Gijsbert M. , Witte Martin D. , Tuin Adriaan W. , Leeuwenburgh Michiel A. , Van der Marel Gijsbert A. , Overkleeft Herman S. , Overhand Mark
Published: June 2006

Four isomeric bicyclic sugar amino acids (SAAs) were prepared from α‐acetylenic‐C‐glucoside 6 by employing a Petasis olefination and a ring‐closing metathesis (RCM) as key steps. The applicability of the resulting SAAs in solid‐phase peptide synthesis was demonstrated by the synthesis of tetrapeptide 36. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Impedance DNA Biosensor Using Electropolymerized Polypyrrole/Multiwalled Carbon Nanotubes Modified Electrode
Authors: Xu Ying , Ye Xiaoyan , Yang Lin , He Pingang , Fang Yuzhi
Published: June 2006

In this paper, we present an electrochemical impedance‐based DNA biosensor by using a composite material of polypyrrole (PPy) and multiwalled carbon nanotubes (MWNTs) to modify glassy carbon electrode (GCE). The polymer film was electropolymerized onto GCE by cyclic voltammetry (CV) in the presence of carboxylic groups ended MWNTs (MWNTs‐COOH). Such electrode modification method is new for DNA hybridization sensor. Amino group ended single‐stranded DNA (NH2‐ssDNA) probe was linked onto the PPy/MWNTs‐COOH/GCE by using EDAC, a widely used water‐soluble carbodiimide for crosslinking amine and carboxylic acid group. The hybridization reaction of this ssDNA/PPy/MWNTs‐COOH/GCE resulted in a decreased impedance, which was attributed to the lower electronic transfer resistance of double‐stranded DNA than single‐stranded DNA. As the result of the PPy/MWNTs modification, the electrode obtained a good electronic transfer property and a large specific surface area. Consequently, the sensitivity and selectivity of this sensor for biosensing DNA hybridization were improved. Complementary DNA sequence as low as 5.0×10−12 mol L−1 can be detected without using hybridization marker or intercalator. Additionally, it was found that the electropolymerization scan rate was an important factor for DNA biosensor fabrication. It has been optimized at 20 mV s−1.
Effect of staining reagent on peptide mass fingerprinting from in‐gel trypsin digestions: A comparison of SyproRuby™ and DeepPurple™
Authors: Tannu Nilesh S. , Sanchez‐Brambila Gabriela , Kirby Pam , Andacht Tracy M.
Published: June 2006

As the new fluorescent stains such as SyproRuby™ and DeepPurple™ are getting widespread recognition for proteome analyses by the traditional 2‐D gel method, it becomes important to test the feasibility of these stains with respect to staining reproducibility, protein quantitation, and compatibility of the stain with downstream MS. The binding of epicocconone, active ingredient of DeepPurple™, to one of the primary cleavage sites of trypsin (lysine residue) raises the possibility of incomplete cleavage and interference with PMF. However, the current study tests and concludes that the DeepPurple™ stain can result in increased peptide recovery compared to SyproRuby™ stain and can improve MS‐based identification of lower intensity proteins spots.
On‐capillary derivatization and analysis of amino acids in human plasma by capillary electrophoresis with laser‐induced fluorescence detection: Application to diagnosis of aminoacidopathies
Authors: Veledo Maria Teresa , de Frutos Mercedes , Diez‐Masa Jose Carlos
Published: June 2006

A capillary electrophoresis with laser‐induced fluorescence detection method for the analysis of free amino acids (AA) in human plasma was developed. A mixture of 16 AA was on‐capillary derivatized with 3‐(2‐furoyl)quinoline‐2‐carboxaldehyde (FQ) and separated inside the capillary in less than 30 min using 70 mM borax‐3.5 mM SDS pH 9.3 as running buffer. Four plasma samples from a healthy donor and patients suffering from phenylketonuria, propionic acidemia, and tyrosinemia type II were studied. Repeatabilities calculated as intra‐day RSD (n = 3) values for the AA involved in these aminoacidopathies (glycine, phenylalanine, and tyrosine) were in the range of 0.3 to 1.2% for migration time and 3.7 to 8.2% for peak height. Reproducibilities calculated as inter‐day RSD (n = 4) values for the same AA were between 0.7 and 1.4% for migration time and 4.7 and 9.1% for peak height. A fast qualitative analysis allowed the identification of the corresponding disease by comparing the electrophoretic profiles from the patient and the healthy donor and noting the increased level of the specific AA accompanying each individual disease. The results of the quantitative analysis for glycine, phenylalanine, and tyrosine in the plasma samples studied using the developed method showed a good agreement with those provided by the Center of Diagnosis of Molecular Diseases using a standard method for AA analysis.