bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxytetracycline Sorption to Organic Matter by Metal‐Bridging
Authors: MacKay Allison A. , Canterbury Brian 
Published: October 2005

ABSTRACTThe sorption of oxytetracycline to metal‐loaded ion exchange resin and to natural organic matter by the formation of ternary complexes between polyvalent metal cations and sorbent‐ and sorbate ligand groups was investigated. Oxytetracycline (OTC) sorption to Ca‐ and Cu‐loaded Chelex‐100 resin increased with increasing metal/sorbate ratio at pH 7.6 (OTC speciation: 55% zwitterion, 45% anion). Greater sorption to Cu‐ than Ca‐loaded resin was observed, consistent with the greater stability constants of Cu with both the resin sites and with OTC. Oxytetracycline sorption to organic matter was measured at pH 5.5 (OTC speciation: 1% cation, 98% zwitterion, 1% anion). No detectable sorption was measured for cellulose or lignin sorbents that contain few metal‐complexing ligand groups. Sorption to Aldrich humic acid increased from “clean” < “dirty” (no cation exchange pretreatment) < Al‐amended < Fe(III)‐amended clean humic acid with Kd values of 5500, 32000, 48000, and 250000 L kg−1 C, respectively. Calcium amendments of clean humic acid suggested that a portion of the sorbed OTC was interacting by cation exchange. Oxytetracycline sorption coefficients for all humic acid sorbents were well‐correlated with the total sorbed Al‐plus‐Fe(III) concentrations (r2 = 0.87, log‐log plot), suggesting that sorption by ternary complex formation with humic acid is important. Results of this research indicate that organic matter may be an important sorbent phase in soils and sediments for pharmaceutical compounds that can complex metals by the formation of ternary complexes between organic matter ligand groups and pharmaceutical ligand groups.
Reducing Sediment and Phosphorus in Tributary Waters with Alum and Polyacrylamide
Authors: Mason L. B. , Amrhein C. , Goodson C. C. , Matsumoto M. R. , Anderson M. A. 
Published: October 2005

ABSTRACTThe Salton Sea is the largest inland water body in California, covering an area of 980 km2 Inflow to the Salton Sea (1.6 km3 yr−1) is predominately nutrient‐rich agricultural wastewater, which has led to eutrophication. Because internal phosphorus release from the bottom sediments is comparatively low and external phosphorus loading to the Salton Sea is high, reduction of tributary phosphorus is expected to reduce algal blooms, increase dissolved oxygen, and reduce odors. Removing both dissolved phosphorus and phosphorus‐laden sediment from agricultural drainage water (ADW) should decrease eutrophication. Both alum and polyacrylamide (PAM) are commonly used in wastewater treatment to remove phosphorus and sediment and were tested for use in tributary waters. Laboratory jar tests determined PAM effectiveness (2 mg L−1) for turbidity reduction as cationic > anionic = nonionic. Although cationic PAM was the most effective at reducing turbidity at higher speeds, there was no observed difference between the neutral and anionic PAMs at velocity gradients of 18 to 45 s−1 Alum (4 mg L−1 Al) reduced turbidity in low energy systems (velocity gradients < 10 s−1) by 95% and was necessary to reduce soluble phosphorus, which comprises 47 to 100% of the total P concentration in the tributaries. When PAM was added with alum, the anionic PAM became ineffective in aiding flocculation. The nonionic PAM (2 mg L−1) + alum (4 mg L−1 Al) is recommended to reduce suspended solids in higher energy systems and reduce soluble P by 93%.
Contribution of multiplexed electrical resistance and magnetic techniques to the archaeological investigations at Poros, Greece
Authors: Papadopoulos N. G. , Sarris A. , Kokkinou E. , Wells B. , Penttinen A. , Savini E. , Tsokas G. N. , Tsourlos P. 
Published: October 2005

AbstractThe Sanctuary of Poseidon at Kalaureia is located on the island of Poros in the Saronic Gulf in Greece. Two Swedish archaeologists first carried out excavations at the site in 1894; in 1997 investigations were resumed by the Swedish Institute at Athens. Although there are traces of occupancy in the area by the early Bronze Age, the results so far attest to some activity in the very late Bronze Age (ca. 1100 BC); with a considerable proportion of the remains dating from the eighth century BC and the visible remains dating to the sixth to second centuries BC.A geophysical investigation was conducted at the site using both electrical resistance techniques and magnetic methods. A small area of 20 × 15 m at the southeast section of the site was surveyed with high‐resolution multiplexed electrical resistance techniques in order to maximize the information content of the subsurface remains in both horizontal and vertical extent.The local vertical magnetic gradient of the Earth's magnetic field was measured using a fluxgate gradiometer, and multiplexed electrical resistance techniques were applied in order to map the subsoil resistance at different depths. In addition, the whole area was investigated with a double twin probe configuration.Emphasis was given to the use of the multiplex electrical resistance technique with different configurations. A small grid to the southeast of the survey area was investigated with a twin probe configuration, recording the subsurface resistance at four increasing depths. Additionally, 0.5 m dipole–dipole and 0.5 m Wenner mapping configurations were performed. The above data were processed using a specifically developed processing package (GPP). The resistance instrument was also programmed in such a way as to conduct parallel resistance tomographies along the x and y directions with a pole–pole array. Copyright © 2005 John Wiley & Sons, Ltd.
Preparation, characterization, and properties of chitosan‐g‐poly(vinyl alcohol) copolymer
Authors: Huang Meifang , Fang Yue'e 
Published: October 2005

AbstractThe graft copolymer chitosan‐g‐poly(vinyl alcohol), with nontoxicity, biodegradability, and biocompatibility, was prepared by a novel method. The copolymer with porous net structure was observed by scanning electron microscopy (SEM). It is a potential method to combine chitosan with the synthetic polymers. The grafting reactions were conducted with various poly(vinyl alcohol) (PVA)/6‐O‐succinate‐N‐phthaloyl‐chitosan (PHCSSA) feed ratios to obtain chitosan‐g‐poly(vinyl alcohol) copolymers with various PVA contents. The chemical structure of the chitosan‐g‐poly(vinyl alcohol) was characterized by Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and SEM were also detected to characterize the copolymer. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 160–166, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
On‐line monitoring of CO2 production in Lactococcus lactis during physiological pH decrease using membrane inlet mass spectrometry with dynamic pH calibration
Authors: Andersen Ann Zahle , Lauritsen Frants Roager , Olsen Lars Folke 
Published: October 2005

AbstractMonitoring CO2 production in systems, where pH is changing with time is hampered by the chemical behavior and pH‐dependent volatility of this compound. In this article, we present the first method where the concentration and production rate of dissolved CO2 can be monitored directly, continuously, and quantitatively under conditions where pH changes rapidly (≈2 units in 15 min). The method corrects membrane inlet mass spectrometry (MIMS) measurements of CO2 for pH dependency using on‐line pH analysis and an experimentally established calibration model. It is valid within the pH range of 3.5 to 7, despite pH‐dependent calibration constants that vary in a non‐linear fashion with more than a factor of 3 in this interval. The method made it possible to determine the carbon dioxide production during Lactococcus lactis fermentations, where pH drops up to 3 units during the fermentation. The accuracy was approximately 5%. We used the method to investigate the effect of initial extracellular pH on carbon dioxide production during anarobic glucose fermentation by non‐growing Lactocoocus lactis and demonstrated that the carbon dioxide production rate increases considerably, when the initial pH was increased from 6 to 6.8. © 2005 Wiley Periodicals, Inc.
Preparation of human metabolites of propranolol using laboratory‐evolved bacterial cytochromes P450
Authors: Otey Christopher R. , Bandara Geethani , Lalonde James , Takahashi Katsuyuki , Arnold Frances H. 
Published: October 2005

AbstractTesting the toxicities and biological activities of the human metabolites of drugs is important for development of safe and effective pharmaceuticals. Producing these metabolites using human cytochrome P450s is difficult, however, because the human enzymes are costly, poorly stable, and slow. We have used directed evolution to generate variants of P450 BM3 from Bacillus megaterium that function via the “peroxide shunt” pathway, using hydrogen peroxide in place of the reductase domain, oxygen and NADPH. Here, we report further evolution of the P450 BM3 heme domain peroxygenase to enhance production of the authentic human metabolites of propranolol by this biocatalytic route. This system offers a versatile, cost‐effective, and scaleable route to the synthesis of drug metabolites. © 2005 Wiley Periodicals, Inc.
Feasibility of early emergency room notification to improve door‐to‐balloon times for patients with acute ST segment elevation myocardial infarction
Authors: Sekulic Milan , Hassunizadeh Bischan , McGraw Steve , David Shukri 
Published: October 2005

AbstractAn algorithm to lower time from first contact in the field by EMS personnel to in‐hospital mechanical reperfusion is described. ECG tracings were telemetered via cellular phone to an emergency room physician, who then activated the cardiac catheterization call team to bypass usual delays seen during ER triage. Seventy‐one ECGs were sent to the ER in the time interval from October 2003 to October 2004. Five ECGs (7.0%) failed to transmit due to failure of the cellular phone to receive an adequate signal. Sixty‐six patients (93.0%) had an adequate ECG transmitted to the ER and six patients with ST elevation myocardial infarction were identified. Door‐to‐balloon times were lowered to 44 ± 17.4 min, a substantial decrease over historical norms that range from 120 min (25th percentile) to 289 min (75th percentile). © 2005 Wiley‐Liss, Inc.
Encapsulation of Cyanometalates by a Tris‐macrocyclic Ligand Tricopper(II) Complex: Syntheses, Structural Variation, and Magnetic Exchange Coupling Pathways
Authors: Atanasov Mihail , Comba Peter , Lampeka Yaroslaw D. , Linti Gerald , Malcherek Thomas , Miletich Ronald , Prikhod'ko Alexander I. , Pritzkow Hans 
Published: October 2005

AbstractThe reaction of [M(CN)6]3− (M=Cr3+, Mn3+, Fe3+, Co3+) and [M(CN)8]4−/3− (M=Mo4+/5+, W4+/5+) with the trinuclear copper(II) complex of 1,3,5‐triazine‐2,4,6‐triyltris[3‐(1,3,5,8,12‐pentaazacyclotetradecane)] ([Cu3(L)]6+) leads to partially encapsulated cyanometalates. With hexacyanometalate(III) complexes, [Cu3(L)]6+ forms the isostructural host–guest complexes [{[Cu3(L)(OH2)2][M(CN)6]2}{M(CN)6}]⋅[M(CN)6]⋅30 H2O with one bridging, two partially encapsulated, and one isolated [M(CN)6]3− unit. The octacyanometalates of Mo4+/5+ and W4+/5+ are encapsulated by two tris‐macrocyclic host units. Due to the stability of the +IV oxidation state of Mo and W, only assemblies with [M(CN)8]4− were obtained. The Mo4+ and W4+ complexes were crystallized in two different structural forms: [{Cu3(L)(OH2)}2{Mo(CN)8}](NO3)8⋅15 H2O with a structural motif that involves isolated spherical [{Cu3(L)(OH2)}2{M(CN)8}]8+ ions and a “string‐of‐pearls” type of structure [{[Cu3(L)]2[M(CN)8]}{M(CN)8}](NO3)4⋅ 20 H2O, with [M(CN)8]4− ions that bridge the encapsulated octacyanometalates in a two‐dimensional network. The magnetic exchange coupling between the various paramagnetic centers is characterized by temperature‐dependent magnetic susceptibility and field‐dependent magnetization data. Exchange between the Cu⋅⋅⋅Cu pairs in the [Cu3(L)]6+ “ligand” is weakly antiferromagnetic. Ferromagnetic interactions are observed in the cyanometalate assemblies with Cr3+, exchange coupling of Mn3+ and Fe3+ is very small, and the octacoordinate Mo4+ and W4+ systems have a closed‐shell ground state.
Supramolecular Assembly of an Amphiphilic GdIIIChelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate
Authors: Torres Susana , Martins José A. , André João P. , Geraldes Carlos F. G. C. , Merbach André E. , Tóth Éva 
Published: October 2005

AbstractWe report the synthesis and characterization of the novel ligand H5EPTPA‐C16((hydroxymethylhexadecanoyl ester)ethylenepropylenetriaminepentaacetic acid). This ligand was designed to chelate the GdIIIion in a kinetically and thermodynamically stable way while ensuring an increased water exchange rate (kex) on the GdIIIcomplex owing to steric compression around the water‐binding site. The attachment of a palmitic ester unit to the pendant hydroxymethyl group on the ethylenediamine bridge yields an amphiphilic conjugate that forms micelles with a long tumbling time (τR) in aqueous solution. The critical micelle concentration (cmc = 0.34 mM) of the amphiphilic [Gd(eptpa‐C16)(H2O)]2−chelate was determined by variable‐concentration proton relaxivity measurements. A global analysis of the data obtained in variable‐temperature and multiple‐field17O NMR and1H NMRD measurements allowed for the determination of parameters governing relaxivity for [Gd(eptpa‐C16)(H2O)]2−; this is the first time that paramagnetic micelles with optimized water exchange have been investigated. The water exchange rate was found to be${k{{\,298\hfill \atop {\rm ex}\hfill}}}$= 1.7×108s−1, very similar to that previously reported for the nitrobenzyl derivative [Gd(eptpa‐bz‐NO2)(H2O)]2−(${k{{\,298\hfill \atop {\rm ex}\hfill}}}$= 1.5×108s−1). The rotational dynamics of the micelles were analysed by using the Lipari–Szabo approach. The micelles formed in aqueous solution show considerable flexibility, with a local rotational correlation time of${\tau {{\,298\hfill \atop {\rm l0}\hfill}}}$= 330 ps for the GdIIIsegments, which is much shorter than the global rotational correlation time of the supramolecular aggregates,${\tau {{298\hfill \atop {\rm g0}\hfill}}}$= 2100 ps. This internal flexibility of the micelles is responsible for the limited increase of the proton relaxivity observed on micelle formation (r1= 22.59 mM−1 s−1for the micelles versus 9.11 mM−1 s−1for the monomer chelate (20 MHz; 25 °C)).
Lipase Active‐Site‐Directed Anchoring of Organometallics: Metallopincer/Protein Hybrids
Authors: Kruithof Cornelis A. , Casado Miguel A. , Guillena Gabriela , Egmond Maarten R. , van der Kerk‐van Hoof Anca , Heck Albert J. R. , Klein Gebbink Robertus J. M. , van Koten Gerard 
Published: October 2005

AbstractThe work described herein presents a strategy for the regioselective introduction of organometallic complexes into the active site of the lipase cutinase. Nitrophenol phosphonate esters, well known for their lipase inhibitory activity, are used as anchor functionalities and were found to be ideal tools to develop a single‐site‐directed immobilization method. A small series of phosphonate esters, covalently attached to ECE “pincer”‐type d8‐metal complexes through a propyl tether (ECE=[C6H3(CH2E)2‐2,6]−; E=NR2 or SR), were designed and synthesized. Cutinase was treated with these organometallic phosphonate esters and the new metal‐complex/protein hybrids were identified as containing exactly one organometallic unit per protein. The organometallic proteins were purified by membrane dialysis and analyzed by ESI‐mass spectrometry. The major advantages of this strategy are: 1) one transition metal can be introduced regioselectively and, hence, the metal environment can potentially be fine‐tuned; 2) purification procedures are facile due to the use of pre‐synthesized metal complexes; and, most importantly, 3) the covalent attachment of robust organometallic pincer complexes to an enzyme is achieved, which will prevent metal leaching from these hybrids. The approach presented herein can be regarded as a tool in the development of regio‐ and enantioselective catalyst as well as analytical probes for studying enzyme properties (e.g., structure) and, hence, is a “proof‐of‐principle design” study in enzyme chemistry.
Transition‐Metal‐Catalyzed Sequential Cross‐Coupling of Bis(iodozincio)methane and ‐ethane with Two Different Organic Halides
Authors: Yoshino Hideaki , Toda Narihiro , Kobata Masami , Ukai Katsumi , Oshima Koichiro , Utimoto Kiitiro , Matsubara Seijiro 
Published: October 2005

AbstractBis(iodozincio)methane, prepared from diiodomethane and zinc, reacts with an organic halide in the presence of a transition‐metal catalyst to give an iodozinciomethylenated compound; this then reacts with another organic halide to form a CC bond. The overall process connects two electrophiles with one carbon atom. Bis(iodozincio)ethane can also undergo this transformation, yielding a new stereogenic center. The asymmetric induction of this stereogenic center was investigated by using a chiral palladium catalyst.
A Close Look at Fluorescence Quenching of Organic Dyes by Tryptophan
Authors: Doose Sören , Neuweiler Hannes , Sauer Markus 
Published: October 2005

AbstractUnderstanding fluorescence quenching processes of organic dyes by biomolecular compounds is of fundamental importance for in‐vitro and in‐vivo fluorescence studies. It has been reported that the excited singlet state of some oxazine and rhodamine derivatives is efficiently and almost exclusively quenched by the amino acid tryptophan (Trp) and the DNA base guanine via photoinduced electron transfer (PET). We present a detailed analysis of the quenching interactions between the oxazine dye MR121 and Trp in aqueous buffer. Steady‐state and time‐resolved fluorescence spectroscopy, together with fluorescence correlation spectroscopy (FCS), reveal three contributing quenching mechanisms: 1) diffusion‐limited dynamic quenching with a bimolecular quenching rate constant kd of 4.0×109 s−1 M−1, 2) static quenching with a bimolecular association constant Ks of 61 M−1, and 3) a sphere‐of‐action contribution to static quenching described by an exponential factor with a quenching constant λ of 22 M−1. The latter two are characterized as nonfluorescent complexes, formed with ≈30 % efficiency upon encounter, that are stable for tens of nanoseconds. The measured binding energy of 20–30 kJmol−1 is consistent with previous estimates from molecular dynamics simulations that proposed stacked complexes due to hydrophobic forces. We further evaluate the influence of glycerol and denaturant (guanidine hydrochloride) on the formation and stability of quenched complexes. Comparative measurements performed with two other dyes, ATTO 655 and Rhodamine 6G show similar results and thus demonstrate the general applicability of utilizing PET between organic dyes and Trp for the study of conformational dynamics of biopolymers on sub‐nanometer length and nanosecond time‐scales.
Tuning of the α‐Terthiophene Radical Cation Coupling Reaction Using Mixed Micelles with Varying Charge Density
Authors: van Stam Jan , Viaene Lucien , Evans Christopher H. 
Published: October 2005

AbstractThe photophysics and photochemistry of α‐terthiophene (αT), compartmentalized in mixed nonionic/anionic micelles, have been investigated with focus on the influence of the micellar surface charge density on the formation of the radical coupling product α‐hexathiophene (αH). By varying the ratio of nonionic‐to‐anionic surfactants, and assuming ideal mixing, the charge density of the mixed micelles was varied. From Poisson–Boltzmann calculations, performed using the cell model, the electrostatic potential and the counterion activity were estimated as a function of the distance from the micellar surface. Upon excitation, the triplet state of αT is formed, from which the αT radical cation can be formed by absorption of a second photon. The radical cation can form αH if it encounters another αT radical cation. Under the experimental conditions used, this implies that the αH formation only occurs if the compartmentalized radical cation is able to migrate from its host micelle to another micelle, either via the surrounding bulk or by fusion of two micelles followed by mixing of their contents before micellar fission. The formation yield of the radical cation depends on the charge density of the mixed micelle; a lower charge density, that is, an increased amount of nonionic surfactant, lowers the yield. The yield of the coupling product αH, however, does not follow the same trend. A maximum yield of αH is found at intermediate nonionic surfactant molar ratios. This behavior is understood in terms of the Poisson–Boltzmann simulation results and by comparing charge‐density changes as a function of molar fraction with the changes in counterion activity. The αH yield is a result of the balance between an increased possibility of radical cation bulk migration and a lowered electrostatic stabilization of the radical.
Novel Highly Substituted Biraryl Ethers, Phomosines D–G, Isolated from the Endophytic Fungus Phomopsis sp. from Adenocarpus foliolosus
Authors: Dai Jingqiu , Krohn Karsten , Flörke Ulrich , Gehle Dietmar , Aust Hans‐Jürgen , Draeger Siegfried , Schulz Barbara , Rheinheimer Joachim 
Published: October 2005

AbstractSix new metabolites, phomosines D–G (4–7), 6‐hydroxy‐6‐isopropylcyclohex‐1‐enecarboxylic acid (8) and(1aS,3R,4R,4aR,6S,7R,8aS)‐7‐chloro‐3,6‐dihydroxy‐3,4a,8,8‐tetramethyl‐octahydro‐1aH‐naphtho[1‐b]oxirene‐4‐carboxylic acid (9) were isolated together with seven known compounds (1–3, 10–13) from the endophytic fungus Phomopsis sp. The structures of 1–13 were determined by spectroscopic methods (mainly extensive 1D and 2D NMR experiments and by mass spectrometric measurements). The antibacterial, fungicidal, and herbicidal properties of the new compounds were evaluated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Natural Product‐Guided Synthesis of a Spiroacetal Collection Reveals Modulators of Tubulin Cytoskeleton Integrity
Authors: Barun Okram , Kumar Kamal , Sommer Stefan , Langerak Anette , Mayer Thomas U. , Müller Oliver , Waldmann Herbert 
Published: October 2005

AbstractThe spiro[5.5]ketal moiety forms the underlying structural skeleton of numerous biologically active natural products. Since simplified but characteristic spiroketals derived from the parent natural products retain biological activity, the spiro[5.5]ketal unit can be regarded as a biologically prevalidated framework for the development of natural product‐derived compound collections. We report an enantioselective synthesis of spiro[5.5]ketals on solid support. The reaction sequence employs asymmetric boron enolate aldol reactions with the enolate bound to the polymer or in solution as the key enantiodifferentiating step. It proceeds in up to 12 steps on solid support, makes the desired spiroketals available in high overall yields and with high stereoselectivities and is amenable to structural variation of the products. The small spiroketal collection synthesized contains phosphatase inhibitors and compounds that modulate the formation of the tubulin cytoskeleton in human cancer cells without directly targeting microtubules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)