bluuebunny/crossref_metadata_2025 huggingface dataset:
Exposure to a moderate intensity static magnetic field enhances the hypotensive effect of a calcium channel blocker in spontaneously hypertensive rats
Authors: Okano Hideyuki , Ohkubo Chiyoji
Published: September 2005

We investigated the combined effects of a moderate intensity static magnetic field (SMF) and an L‐type voltage‐gated Ca2+ channel blocker, nicardipine in stroke‐resistant spontaneously hypertensive rats during the development of hypertension. Five‐week‐old male rats were exposed to SMF intensity up to 180 mT (Bmax) with a peak spatial gradient of 133 mT/mm for 14 weeks. Four experimental groups of 14 animals each were examined: (1) sham exposure with intraperitoneal (ip) saline injection (control); (2) SMF exposure with ip saline injection (SMF); (3) sham exposure with ip nicardipine injection (NIC); (4) SMF exposure with ip nicardipine injection (SMF + NIC). A disc‐shaped permanent magnet or a dummy magnet was implanted in the vicinity adjacent to the left carotid sinus baroreceptor region in the neck of each rat. Nicardipine (2 mg/kg ip) was administered three times a week for 14 weeks, and then 15 min after each injection, arterial blood pressure (BP), heart rate (HR), baroreflex sensitivity (BRS), skin blood flow (SBF), skin blood velocity (SBV), plasma nitric oxide (NO) metabolites (NOx = NO + NO), plasma catecholamine levels and behavioral parameters of a functional observational battery were monitored. The action of nicardipine significantly decreased BP, and increased HR, SBF, SBV, plasma epinephrine and norepinephrine in the NIC group compared with the control respective age‐matched group without changing plasma NOx levels. Neck exposure to SMF alone for 5–8 weeks significantly suppressed or retarded the development of hypertension together with increased BRS in SMF group. Furthermore, the exposure to SMF for 1–8 weeks significantly promoted the nicardipine‐induced BP decrease in the SMF + NIC group compared with the respective NIC group. Moreover, the SMF induced a significant increase in plasma NOx in the nicardipine‐induced hypotension. There were no significant differences in any of the physiological or behavioral parameters measured between the SMF + NIC and the NIC groups, nor between the SMF and the control groups. These results suggest that the SMF may enhance nicardipine‐induced hypotension by more effectively antagonizing the Ca2+ influx through the Ca2+ channels compared with the NIC treatment alone. Furthermore, the enhanced antihypertensive effects of the SMF on the nicardipine‐treated group appear to be partially related to the increased NOx. Theoretical considerations suggest that the applied SMF (Bmax 40 mT, 0 Hz) can be converted into a changing magnetic field (Bmax 30–40 mT, 5.7–6.5 Hz or 7.5–8.3 Hz) in the baroreceptor region by means of the carotid artery pulsation. Therefore, we propose that the moderate intensity changing magnetic field, i.e., the magnetic field modulated by the pulse rate, may influence the activity of baroreceptor and baroreflex function. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Metabolic pathway of magnetized fluid‐induced relaxation effects on heart muscle
Authors: Ayrapetyan Gayane , Papanyan Alexander , Hayrapetyan Hovik , Ayrapetyan Sinerik
Published: September 2005

The effect of magnetized physiological solution (MPS) on isolated, perfused snail heart muscle contractility, 45Ca uptake and intracellular level of cAMP, and cGMP was studied. The existence of the relaxing effect of MPS on heart muscle at room temperature (22 °C) and its absence in cold medium (4 °C) was shown. The MPS had a depressing effect on 45Ca uptake by muscles and intracellular cAMP content and an elevating effect on intracellular cGMP level. It is suggested that the relaxing effect of MPS on heart muscle is due to the decrease of intracellular Ca ions as the result of activation of cGMP‐dependent Ca efflux. The MPS induced decrease of intracellular cAMP content can be considered as a consequence of intracellular Ca loss, leading to the Na + K‐ATPase reactivation, and causing the decrease of the intracellular level of ATP, serving as a substrate and positive modulator of cyclase activity. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Pulsed electric field exposure of insulin induces anti‐proliferative effects on human hepatocytes
Authors: Li Lejun , Dai Yuwen , Xia Ruohong , Chen Shude , Qiao Denjiang
Published: September 2005

The purpose of this study was to examine the effects and the mechanism of a pulsed electric field (PEF) on insulin and its subsequent mediation of proliferative changes in human hepatocytes in vitro. The PEF, the electric field intensity coupled into the culture medium, was about 0.7 V/m with a repeating frequency of 50 Hz. Insulin solution was exposed to PEF for 20 min and added to the culture medium of human hepatocytes. Combining fluorescence spectroscopy, immunocytochemistry, microarrays, RT‐PCR and MTT, several important events of the insulin signaling pathways were investigated, including ligand‐receptor binding capacity, intracellular tyrosine phosphorylation level, gene transcription, and cell proliferation. PEF produced a conformational change of insulin molecule. The binding capacity of insulin to its receptors was reduced to 87% of the control level after PEF treatment, and the average intracellular tyrosine phosphorylation level decreased by 11%. The expression of 55 of 12000 genes examined was modified, including an increase in the expression of human tyrosine phosphatase and the small GTP‐binding protein. Based on these results, a mechanism is proposed to explain the bio‐effects of PEF on hepatic cell proliferation through the insulin signaling pathway. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Numerical assessment of induced ELF Currents in the human head due to the battery current of a digital mobile phone
Authors: Ilvonen Sami , Sihvonen Ari‐Pekka , Kärkkäinen Kimmo , Sarvas Jukka
Published: September 2005

In this study, the extremely low frequency (ELF) fields induced in the human head by the battery currents of a mobile phone are considered. The magnetic field induced by the phone was measured, and this data was used to calculate the resulting currents induced in the human head and brain. Both the finite element method (FEM) and finite integration technique (FIT) were used for numerical computations. The computed current density values were then compared with the guidelines given by the International Commission on Non‐Ionising Radiation Protection (ICNIRP). The comparison showed that the computed exposure is well within the limits of those guidelines. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Effect of a low intensity magnetic field on human motor behavior
Authors: Legros Alexandre , Beuter Anne
Published: September 2005

Extremely low frequency (ELF) magnetic fields (MF) are omnipresent in our modern daily environment, but their effects on humans are still not clearly established. The aim of this study was to determine the effect of a 50 Hz, 1000 µT MF centered at the level of the head on human index finger micro‐displacements. Twenty‐four men recruited among the personnel of the French company, Electricité de France (EDF), completed the experiment. Their postural and kinetic tremors were recorded under four “field‐on” and four “field‐off” conditions, each tested during a real and a sham sequence. Eight postural and four kinetic tremor characteristics were calculated on recorded time series and were used for statistical analysis. No effect of the MF was found for kinetic tremor. Concerning postural tremor, the proportion of oscillations at low frequencies (between 2 and 4 Hz) was higher during the real than during the sham exposure sequence (P < .05). It suggests that MF could have a subtle delayed effect on human behavior, which is clearly not pathological. These results should be taken into account for the establishment of new exposure limits. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Timing of pulsed electromagnetic field stimulation does not affect the promotion of bone cell development
Authors: Hannay Gwynne , Leavesley David , Pearcy Mark
Published: September 2005

Pulsed electromagnetic field (PEMF) devices have been used clinically to promote the healing of surgically resistant fractures in vivo. However, there is a sparsity of data on how the timing of an applied PEMF effects the osteogenic cells that would be present within the fracture gap. The purpose of this study was to examine the response of osteoblast‐like cells to a PEMF stimulus, mimicking that of a clinically available device, using four protocols for the timing of the stimulus. The PEMF signal consisted of a 5 ms pulse burst (containing 20 pulses) repeated at 15 Hz. Cultures of a human osteosarcoma cell line, SaOS‐2, were exposed to the four timing protocols, each conducted over 3 days. Protocol one stimulated the cells for 8 h each day, protocol two stimulated the cells for 24 h on the first day, protocol three stimulated the cells for 24 h on the second day, and protocol four stimulated the cells for 24 h on the third day. Cells were seeded with either 25 000 or 50 000 cells/well (24‐well cell culture plates). All assays showed reduced proliferation and increased differentiation (alkaline phosphatase activity) in the PEMF stimulated cultures compared with the control cultures, except for protocol four alkaline phosphatase measurements. No clear trend was observed between the four protocols; however this may be due to cell density. The results indicated that an osteoblast‐like cell line is responsive to a 15 Hz PEMF stimulus, which will stimulate the cell line to into an increasing state of maturity. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Do electromagnetic fields interact with electrons in the Na,K‐ATPase?
Authors: Blank Martin
Published: September 2005

The effects of low frequency electric and magnetic fields on several biochemical systems, including the Na,K‐ATPase, indicate that electromagnetic (EM) fields interact with electrons. The frequency optima for two enzymes in response to EM fields are very close to their turnover numbers, suggesting that these interactions directly affect reaction rates. Nevertheless, generally accepted ideas about Na,K‐ATPase function and ion transport mechanisms do not consider interactions with electrons. To resolve the clash of paradigms, we hypothesize interaction with transient electrons and protons that arise from flickering of H‐bonds in the hydrated protein. These transient charges in the enzyme could provide a trigger for the sequence of conformation changes that are part of the ion transport mechanism. If the distributions of transient electrons and protons in the membrane are affected by their concentration and the membrane potential, as expected from electric double layer theory, this can account for the different effects of low frequency electric and magnetic fields, as well as for the observation that membrane hyperpolarization reverses the ATPase reaction to generate ATP. Bioelectromagnetics © 2005 Wiley‐Liss, Inc.
Analysis of the structure of magnetic fields that induced inhibition of stimulated neurite outgrowth
Authors: Binhi V.N. , Blackman C.F.
Published: September 2005

The important experiments showing nonlinear amplitude dependences of the neurite outgrowth in pheochromocytoma nerve cells due to ELF magnetic field exposure had been carried out in a nonuniform ac magnetic field. The nonuniformity entailed larger than expected variances in magnetic field magnitudes associated with specific levels of biological effects, thereby evoking a question about validity of the interpretations formulated for the case of a uniform field. In this work, we calculate the relative value of nonuniformity and deviations in ac magnetic field. It is shown that these factors do not affect the main conclusion in the original papers about the form of the amplitude dependence of the observed biological effect. Bioelectromagnetics Published 2005 Wiley‐Liss, Inc.
Microbial transformations 59: First kilogram scale asymmetric microbial Baeyer‐Villiger oxidation with optimized productivity using a resin‐based in situ SFPR strategy
Authors: Hilker Iris , Wohlgemuth Roland , Alphand Véronique , Furstoss Roland
Published: September 2005

This study is demonstrating the scale up of asymmetric microbial Baeyer‐Villiger oxidation of racemic bicyclo[3.2.0]hept‐2‐en‐6‐one (1) to the kilogram scale using a 50 L bioreactor. The process has been optimized with respect to bottlenecks identified in downscaled experiments. A high productivity was obtained combining a resin‐based in situ substrate feeding and product removal methodology (in situ SFPR), a glycerol feed control, and an improved oxygenation device (using a sintered‐metal sparger). As expected both regioisomeric lactones [(−)‐(1S,5R)‐2 and (−)‐(1R,5S)‐3] were obtained in nearly enantiopure form (ee > 98%) and good yield. This represents the first example of such an asymmetric Baeyer‐Villiger biooxidation reaction ever operated at that scale. This novel resin‐based in situ SFPR technology therefore clearly opens the way to further (industrial) upscaling of this highly valuable (asymmetric) reaction. © 2005 Wiley Periodicals, Inc.
Physical and biological performance of a novel block copolymer nerve guide
Authors: Lietz M. , Ullrich A. , Schulte‐Eversum C. , Oberhoffner S. , Fricke C. , Müller H.W. , Schlosshauer B.
Published: September 2005

Although the ability to regenerate is evident in the nervous system, lesioned neurites are unable to cross gaps in neuronal pathways. In order to bridge gaps, guiding cues are essential to direct neurite regrowth. To overcome many of the shortcomings of polymer‐based nerve guides, we developed a bioresorbable nerve guide composed of a novel trimethylene carbonate‐caprolacton block copolymer (TMC‐CL). Pore formation was controlled by using special solvent/precipitation media compositions in combination with the pore forming agent poly ethylene glycol (PEG). NMR spectroscopy, shear force‐, compression‐, and permeation assays were used for conduit characterization. The polymer conduit has a semipermeable wall with submicron pores to allow free metabolite/drug exchange. In order to investigate the principle of temporally controlled expression of therapeutic proteins in nerve guides, Neuro‐2a cells were genetically engineered to express the reporter gene product green fluorescent protein (GFP) under the control of the Tet‐On system. When these transduced cells were encapsulated in nerve guides, GFP expression could be induced for days by adding the antibiotic tetracycline derivative doxycycline to the nerve guide environment. Furthermore, encapsulated dorsal root ganglia (DRG) produced long neurites in vitro. In subsequent in vivo experiments, nerve guides filled with Schwann cells (SC) were implanted into lesioned spinal cords of adult rats. Regeneration of spinal cord axons into nerve guides was promoted by co‐implanted Schwann cells. The data suggest that the novel TMC‐CL nerve guides provide a promising tool for neuroregeneration. © 2005 Wiley Periodicals, Inc.
Reversible permeabilization using high‐intensity femtosecond laser pulses: Applications to biopreservation
Authors: Kohli Vikram , Acker Jason P. , Elezzabi Abdulhakem Y.
Published: September 2005

Non‐invasive manipulation of live cells is important for cell‐based therapeutics. Herein we report on the uniqueness of using high‐intensity femtosecond laser pulses for reversibly permeabilizing mammalian cells for biopreservation applications. When mammalian cells were suspended in a impermeable hyperosmotic cryoprotectant sucrose solution, femtosecond laser pulses were used to transiently permeabilize cells for cytoplasmic solute uptake. The kinetics of cells exposed to 0.2, 0.3, 0.4, and 0.5 M sucrose, following permeabilization, were measured using video microscopy, and post‐permeabilization survival was determined by a dual fluorescence membrane integrity assay. Using appropriate laser parameters, we observed the highest cell survival for 0.2 M sucrose solution (>90%), with a progressive decline in cell survival towards higher concentrations. Using diffusion equations describing the transport of solutes, the intracellular osmolarity at the inner surface of the membrane (x = 10 nm) and to a diffusive length of x = 10 μm was estimated, and a high loading efficiency (>98% for x = 10 nm and >70% for x = 10 μm) was calculated for cells suspended in 0.2 M sucrose. This is the first report of using femtosecond laser pulses for permeabilizing cells in the presence of cryoprotectants for biopreservation applications. © 2005 Wiley Periodicals, Inc.
Bean Yellow Dwarf Virus replicons for high‐level transgene expression in transgenic plants and cell cultures
Authors: Zhang Xiuren , Mason Hugh
Published: September 2005

A novel stable transgenic plant expression system was developed using elements of the replication machinery of Bean Yellow Dwarf Virus (BeYDV). The system contains two transgenes: 1) The BeYDV replicon vector with an expression cassette flanked by cis‐acting DNA elements of BeYDV, and 2) The viral replication initiator protein (Rep) controlled by an alcohol‐inducible promoter. When Rep expression was triggered by treatment with ethanol, it induced release of the BeYDV replicon from stably integrated T‐DNA and episomal replication to high copy number. Replicon amplification resulted in substantially increased transgene mRNA levels (up to 80‐fold) and translation products (up to 10‐fold) after induction of Rep expression by ethanol treatment in tobacco NT1 cells and leaves of whole potato plants. Thus, the BeYDV stable transformant replicon system is a powerful tool for plant‐based production of recombinant proteins. © 2005 Wiley Periodicals, Inc.
Trap and release of oligonucleotide using pH‐responsive amphoteric particle prepared by interfacial polymerization in W/O miniemulsion system
Authors: Taira Shu , Du Yong‐Zhong , Kodaka Masato
Published: September 2005

Novel amphoteric particles are prepared by an interfacial polyaddition reaction of ethylene glycol diglycidyl ether (EGDGE) and L‐lysine in a water‐in‐oil (W/O) miniemulsion system. The ζ‐potential of the copolymer particle as a function of pH indicates a sigmoid curve with an isoelectric point at pH 8.7 due to the existence of secondary amino and carboxyl groups in the copolymer chain. The obtained amphoteric particle bears positive charge under pH 8.7 and negative charge over pH 8.7. This specific property of the pH‐responsive amphoteric particle is employed to separate single‐stranded DNA (ssDNA). The trapped ssDNA at pH 7.0 is almost released by changing pH to 11.0, which can be carried out repeatedly. © 2005 Wiley Periodicals, Inc.
Uptake and biotransformation of 2,4,6‐trinitrotoluene (TNT) by microplantlet suspension culture of the marine red macroalga Portieria hornemannii
Authors: Cruz‐Uribe Octavio , Rorrer Gregory L.
Published: September 2005

Microplantlets of the marine red macroalga Portieria hornemannii efficiently removed the explosive compound 2,4,6‐trinitrotoluene (TNT) from seawater. Photosynthetic, axenic microplantlets (1.2 g FW/L) were challenged with enriched seawater medium containing dissolved TNT at concentrations of 1.0, 10, and 50 mg/L. At 22°C and initial TNT concentrations of 10 mg/L or less, TNT removal from seawater was 100% within 72 h, and the first‐order rate constant for TNT removal ranged from 0.025 to 0.037 L/gFW h under both illuminated conditions (153 µE/m2s, 14:10 LD photoperiod) and dark conditions. Two immediate products of TNT biotransformation, 2‐amino‐4,6‐dinitrotoluene and 4‐amino‐2,6‐dintrotoluene, were identified in the liquid culture medium, with a maximum material balance recovery of 29 mole%. Only trace levels of these products and residual TNT were found within the fresh cell biomass. Removal of TNT by P. hornemannii microplantlets at initial concentrations of 1.0 or 10 mg/L did not affect the respiration rate. At an initial TNT concentration of 10 mg/L, net photosynthesis decreased towards zero, commensurate with the removal of dissolved TNT from seawater, whereas at an initial TNT concentration of 1.0 mg/L, the net photosynthesis rate was not affected. © 2005 Wiley Periodicals, Inc.
Initial transcriptome and proteome analyses of low culture temperature‐induced expression in CHO cells producing erythropoietin
Authors: Baik Jong Youn , Lee Moon Sue , An So Ra , Yoon Sung Kwan , Joo Eun Jin , Kim Young Hwan , Park Hong Woo , Lee Gyun Min
Published: September 2005

Low culture temperature is known to enhance the specific productivity of Chinese hamster ovary (CHO) cells expressing erythropoietin (EPO) (LGE10‐9‐27). Genomic and proteomic approaches were taken to better understand the intracellular responses of these CHO cells resulting from use of low culture temperature (33°C). For transcriptome analysis, commercially available rat and mouse cDNA microarrays were used. The data obtained from the rat and mouse cDNA chips were only somewhat informative in understanding the gene expression profile of CHO cells because of their different sequence homologies with CHO transcriptomes. Overall, transcriptome analysis revealed that low culture temperature could lead to changes in gene expression in various cellular processes such as metabolism, transport, and signaling pathways. Proteome analysis was carried out using 2‐D PAGE. Based on spot intensity, 60 high intensity protein spots, from a total of more than 800, were chosen for MS analysis. Forty of the 60 protein spots, which represent 26 different kinds of proteins, were identified by MALDI‐TOF‐MS and validated by MS/MS. Compared to the reference temperature (37°C), the expression levels of seven proteins (PDI, vimentin, NDK B, ERp57, RIKEN cDNA, phosphoglycerate kinase, and heat shock cognate 71 kDa protein) were increased over twofold at 33°C and those of two proteins (HSP90‐beta and EF2) were decreased over twofold at 33°C. Taken together, the results demonstrate the potential of combined analysis of transcriptome and proteome analyses as a tool for the systematic comprehension of cellular mechanisms in CHO cells. © 2005 Wiley Periodicals, Inc.
Pulsed Gradient Spin Echo (PGSE) Diffusion Measurements as a Tool for the Elucidation of a New Type of Hydrogen‐Bonded Bicapsular Aggregate
Authors: Alajarín Mateo , Pastor Aurelia , Orenes Raúl‐Angel , Martínez‐Viviente Eloísa , Pregosin Paul S.
Published: September 2005

Compounds formed by linking two tris(ureidobenzyl)amine modules with a hexamethylene tether are described. These compounds self‐assemble to form bicapsular aggregates featuring two rings of six hydrogen‐bonded ureas. 1H and 1H/1H ROESY NMR spectroscopy, together with pulsed gradient spin echo (PGSE) NMR diffusion measurements, have been used to characterize the dimers in solution. The results have been compared with energy‐minimized structures. The new compounds are kinetically stable on the NMR timescale, and their thermodynamic stabilities are comparable to other capsular aggregates derived from tris(ureidobenzyl)amines.
Tunable Charge Delocalization in Dinickel Quinonoid Complexes
Authors: Siri Olivier , Taquet Jean‐philippe , Collin Jean‐Paul , Rohmer Marie‐Madeleine , Bénard Marc , Braunstein Pierre
Published: September 2005

When a 2,5‐diamino‐1,4‐benzoquinonediimine C6H2(NR)2(NHR)2(2) is used as a bridging ligand, new dinickel(II) complexes [(acac)Ni{μ‐C6H2(${^{\underline{.....}}}$NPh)4}Ni(acac)] (3 a: R=Ph) and [(acac)Ni{μ‐C6H2(${^{\underline{.....}}}$NCH2tBu)4}Ni(acac)] (3 b: R=CH2tBu) are obtained; upon one‐electron oxidation of these complexes delocalized mixed‐valence compounds are formed. An X‐ray diffraction study on3 breveals equalization of the bond lengths within each of the ligand 6π systems and a lack of conjugation between them. The oxidized state in3 b+involves both the bridging quinonoid ligand and the metal centers, with a major contribution coming from the bridging ligand. Electrochemical and spectroscopic methods were used to study the influence of the N‐substituents of the tetranitrogen donor ligands2. In this combined experimental and theoretical (DFT) study, it is also shown that the electronic structure within the dinickel system can be altered by addition of a coordinating ligand such as pyridine. The latter favors the high‐spin configuration with semi‐occupied metal‐centered orbitals, leading to a metal–metal interaction in the mixed‐valence NiII–NiIII3 b+system.
Structural, Electronic, and Bonding Properties of Zeolite Sn‐Beta: A Periodic Density Functional Theory Study
Authors: Shetty Sharan , Pal Sourav , Kanhere Dilip G. , Goursot Annick
Published: September 2005

The structural, electronic, and the bonding properties of the zeolite Sn‐beta (Sn‐BEA) have been investigated by using the periodic density functional theory. Each of the nine different T‐sites in BEA were substituted by Sn atoms and all the nine geometries were completely optimized by using the plane‐wave basis set in conjunction with the ultra‐soft pseudopotential. On the basis of the structural and the electronic properties, it has been demonstrated that the substitution of Sn atoms in the BEA framework is an endothermic process and hence the incorporation of Sn in the BEA is limited. The lowest unoccupied molecular orbitals (LUMO) energies have been used to characterize the Lewis acidity of each T‐site. On the basis of the relative cohesive energy and the LUMO energy, the T2 site is shown to be the most favorable site for the substitution Sn atoms in the BEA framework.
Self‐Assembly of Dialkyltin Moieties and Mercaptobenzoic Acid into Macrocyclic Complexes with Hydrophobic “Pseudo‐Cage” or Double‐Cavity Structures: Supramolecular Infrastructures Involving Intermolecular CH⋅⋅⋅S Weak Hydrogen Bonds and π–π Interactions
Authors: Ma Chunlin , Zhang Qingfu , Zhang Rufen , Wang Daqi
Published: September 2005

Four novel organotin complexes of two types—[R2Sn(o‐SC6H4CO2)]6(R=Me,1⋅H2O;nBu,2) and {[R2Sn(m‐CO2C6H4S)R2Sn(m‐SC6H4CO2)SnR2]O}2(R=Me,3;nBu,4)—have been prepared by treatment ofo‐ orm‐mercaptobenzoic acid and the corresponding R2SnCl2(R=Me,nBu) with sodium ethoxide in ethanol (95 %). All the complexes were characterized by elemental analysis, FT‐IR and NMR (1H,13C,119Sn) spectroscopy, TGA, and X‐ray crystallography diffraction analysis. The molecular structure analyses reveal that both1and2are hexanuclear macrocycles with hydrophobic “pseudo‐cage” structures, while3and4are hexanuclear macrocycles with double‐cavity structures. Furthermore, the supramolecular structure analyses show that looser and more intriguing supramolecular infrastructures were also found in complexes1–4, which exist either as one‐dimensional chains of rings or as two‐dimensional networks assembled from the organometallic subunits through intermolecular CH⋅⋅⋅S weak hydrogen bonds (WHBs) and π–π interactions.
Photoinduced Oxygen Transfer and Double‐Linkage Isomerism in a cis‐(NO)(NO2) Transition‐Metal Complex by Photocrystallography, FT‐IR Spectroscopy and DFT Calculations
Authors: Kovalevsky Andrey Yu , King Graham , Bagley Kimberly A. , Coppens Philip
Published: September 2005

Photocrystallographic experiments show that laser exposure of crystals of [Ru(bpy)2(NO)(NO2)](PF6)2 at 90 K produces a double isonitrosyl–nitrito linkage isomer and provide the detailed geometry of the metastable species generated. The analysis indicates that the isomerization is accomplished through an intramolecular redox reaction involving oxygen transfer from the nitro to the nitrosyl group. At 200 K only a single (nitrito) linkage isomer is formed with a U‐shaped conformation of the nitrito group rather than the Z conformation observed at 90 K. A mechanism for the isomerization is proposed based on the crystallographic results and FTIR data collected at low temperatures during the isomerization process. The study presents the first structural evidence for double linkage isomerization in transition‐metal complexes.
Synthesis of Nitrogen‐ and Oxygen‐Containing Macrocycles—Derivatives of Lithocholic Acid
Authors: Averin Alexei D. , Ranyuk Elena R. , Lukashev Nikolai V. , Beletskaya Irina P.
Published: September 2005

Palladium‐catalyzed amination of 3,24‐bis(3‐bromophenoxy)cholane (4) with various polyamines and polyoxadiamines 5 taken in 1:1 ratio was used for the synthesis of the macrocycles 6, which contain steroidal and polyamine moieties and were obtained in 38–65 % yields. The same reaction with excess polyamine (2.2–3 equiv) provided bis(polyamino) derivatives of 3,24‐diphenoxycholane 7 in excellent yields, whereas the diarylation of polyamines with two equivalents of 3,24‐bis(3‐bromophenoxy)cholane afforded their bis(steroidal) derivatives 8. Compounds 7 and 8 were employed in the syntheses of cyclodimers 9, which possess two steroidal and two polyamine fragments; the efficiency of two methods was compared.
Recognition‐Induced Polymersomes: Structure and Mechanism of Formation
Authors: Uzun Oktay , Xu Hao , Jeoung Eunhee , Thibault Raymond J. , Rotello Vincent M.
Published: September 2005

Random polystyrene copolymers grafted with complementary recognition elements were combined in chloroform producing vesicular aggregates, that is, recognition‐induced polymersomes (RIPs). Reflection interference contrast microscopy (RICM) in solution, coupled with optical microscopy (OM) and atomic force microscopy (AFM) on solid substrates, were used to determine the wall thickness of the RIPs. Rather than a conventional mono‐ or bilayer structure (∼10 or ∼20 nm, respectively) the RIP membrane was 43±7 nm thick. Structural arrangement of the polymer chains on the RIP wall were characterized by using angle‐resolved X‐ray photoelectron spectroscopy (AR‐XPS). The interior portion of the vesicle membrane was found to be more polar, containing more recognition units, than the exterior part. This gradient suggests that a rapid self‐sorting of polymers takes place during the formation of RIPs, providing the likely mechanism for vesicle self‐assembly.
Synthesis, Liquid‐Crystalline Properties, and Supramolecular Nanostructures of Dendronized Poly(isocyanide)s and Their Precursors
Authors: Tian Yanqing , Kamata Kaori , Yoshida Hirohisa , Iyoda Tomokazu
Published: September 2005

A series of novel dendronized π‐conjugated poly(isocyanide)s were synthesized successfully by using a PdPt μ‐ethynediyl dinuclear complex ([ClPt{P(C2H5)3}2CCPt{P(C2H5)3}2Cl]) as the initiator. The polymerizations of the dendronized monomers follow first‐order kinetics, indicating that living polymerization takes place. The obtained polymers exhibit narrow polydispersities in the range of 1.03–1.20. Thermal properties of the poly(isocyanide)s as well as their isocyanide monomers and precursors with formamido (HCONH‐) moieties as apexes were investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide‐angle X‐ray diffraction (WAXD). Both the peripheries and the apex groups of the dendrons affect the formation of supramolecular column and/or cubic phases of the precursors and monomers. The formamido precursor forms a liquid‐crystalline phase due to intermolecular hydrogen bonding. The isocyanide monomer lacks this hydrogen‐bonding ability and does not display an organized mesophase. All of the rigid poly(isocyanide)s with the monodendrons exhibit columnar liquid‐crystalline phases. Interestingly, cylindrical structures of a poly(isocyanide) were directly visualized by using transmission electron microscopy (TEM).
Investigations of molecular recognition aspects related to the enantiomer separation of 2‐methoxy‐2‐(1‐naphthyl)propionic acid using quinine carbamate as chiral selector: An NMR and FT‐IR spectroscopic as well as X‐ray crystallographic study†
Authors: Akasaka Kazuaki , Gyimesi‐Forrás Krisztina , Lämmerhofer Michael , Fujita Takuma , Watanabe Masataka , Harada Nobuyuki , Lindner Wolfgang
Published: September 2005

The chiral recognition mechanism of a cinchona alkaloid‐based chiral stationary phase (CSP) showing high enantiomer discrimination potential for 2‐methoxy‐2‐(1‐naphthyl)propionic acid (MαNP acid) was investigated. Conformational and structural analyses of the 1:1 complexes of 9‐O‐(tert‐butylcarbamoyl) quinine selector (SO) and MαNP acid (selectand, SA) were carried out employing NMR spectroscopy in solution, Fourier‐transform infrared (FT‐IR) spectroscopy, and solid‐state X‐ray diffraction analysis. Intramolecular NOEs of a soluble analogue of the CSP afforded the conformational states of the free and complexed form of the selector. The 1H‐NMR spectra revealed that the free form of the SO constitutes anti‐open as well as anti‐closed and/or syn‐closed conformers. Upon complexation with the (S)‐MαNP acid enantiomer to form the more stable diastereomeric associate, a conformational transition of the selector takes place, resulting in the synthesis of the anti‐open conformer nearly exclusively. FT‐IR spectra reveal that, besides the primary ion‐pairing interaction, stereoselective hydrogen bonding stabilizes the more stable complex via the amide hydrogen of the SO. X‐ray diffraction analysis of 9‐O‐(tert‐butylcarbamoyl)quinine and (S)‐MαNP acid complex further revealed the occurrence of a bidentate H‐bond‐mediated ionic interaction between SO and SA as well as the lack of π–π interaction in the 1:1 complex, and corroborated the conclusions derived from spectroscopic and chromatographic studies. © 2005 Wiley‐Liss, Inc. Chirality 17:544–555, 2005.
β‐cyclodextrin‐immobilized (4S)‐phenoxy‐(S)‐proline as a catalyst for direct asymmetric aldol reactions
Authors: Shen Zongxuan , Ma Jimei , Liu Yanhua , Jiao Chongjun , Li Ming , Zhang Yawen
Published: September 2005

β‐Cyclodextrin‐immobilized (4S)‐phenoxy‐(S)‐proline was prepared conveniently by simply heating the amino acid and β‐cyclodextrin in ethanol–water (1/1, v/v) and removal of the solvent. This proved to be an efficient catalyst for direct asymmetric aldol reactions, and the catalyst could be recycled four times without loss of enantioselectivity. © 2005 Wiley‐Liss, Inc. Chirality 17:556–558, 2005.
Inversely Polarized Phosphaalkenes as Phosphinidene‐ and Carbene‐Transfer Reagents
Authors: Weber Lothar , Lassahn Ulrich , Stammler Hans‐Georg , Neumann Beate
Published: September 2005

The reaction of the inversely polarized phosphaalkenes RP=C(NMe2)2[R =tBu (1a), Cy (1b), 1‐Ad (1c), Ph (1d), Mes (1e)] with an excess of diphenyl ketene inn‐pentane affords the zwitterionic adduct (Me2N)2C–C(O)=CPh2(2) and the 3,5‐dibenzhydrylidene‐1,4,2‐dioxaphospholanes4a–e. The reaction of1awith Ph2C=C=O in concentrated acetonitrile solution gives4aand 5‐benzhydrylidene‐2‐tert‐butyl‐4,4‐diphenyl‐1,2‐oxaphospholan‐3‐one (6a) as a by‐product. In contrast, treatment of Me3SiP=C(NMe2)2(1i) with the ketene leads to the formation of 2‐phospha‐1,3‐butadiene (5). The thermolabile phosphaalkene8decomposes into an imidazolylidene and (tBuP), the latter species spontaneously oligomerizes to (tBuP)n(n= 3, 4). Obviously, compounds1a–eserve as a convenient source of phosphinidenes and the carbene C(NMe2)2. A Wanzlick‐type equilibrium between these species, however, must be excluded according to exchange and cross‐coupling experiments. The molecular structures of2,4eand6awere determined by X‐ray structure analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis and Thermal Denaturation Studies of Conformationally Restricted 3′‐C‐Ethynyl‐3′‐O,4′‐C‐methyleneribonucleotides
Authors: Hrdlicka Patrick J. , Kumar T. Santhosh , Wengel Jesper
Published: September 2005

Incorporation of conformationally restricted 3′‐C‐ethynyl‐3′‐O,4′‐C‐methyleneribonucleotide X monomers into oligodeoxyribonucleotides results in large decreases in affinity towards complementary DNA, whereas significantly more stable duplexes are formed with RNA complements. RNA selectivity becomes more pronounced upon multiple incorporations of X monomers. Increased thermal stability is observed upon positioning of two X monomers in a +1 zipper interstrand motif. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Wood storage in a wide mountain river: case study of the Czarny Dunajec, Polish Carpathians
Authors: Wyżga Bartłomiej , Zawiejska Joanna
Published: September 2005

Storage of large woody debris in the wide, mountain, Czarny Dunajec River, southern Poland, was investigated following two floods of June and July 2001 with a seven‐year frequency. Within a reach, to which wood was delivered only by bank erosion and transport from upstream, wood quantities were estimated for eighty‐nine, 100 m long, channel segments grouped into nine sections of similar morphology. Results from regression analysis indicated the quantity of stored wood to be directly related to the length of eroded, wooded banks and river width, and inversely related to unit stream power at the flood peak. The largest quantities of wood (up to 33 t ha−1) were stored in wide, multi‐thread river sections. Here, the relatively low transporting ability of the river facilitated deposition of transported wood while a considerable length of eroded channel and island banks resulted in a large number of trees delivered from the local riparian forest. In these sections, a few morphological and ecological situations led to the accumulation of especially large quantities of wood within a small river area. Very low amounts of wood were stored in narrow, single‐thread sections of regulated or bedrock channel. High stream power facilitated transport of wood through these sections while the high strength of the banks and low channel sinuosity prevented bank retreat and delivery of trees to the channel.

Considerable differences in the character of deposited wood existed between wide, multi‐thread channel sections located at different distances below a narrow, 7 km long, channellized reach of the river. Wood deposited close to the downstream end of the channellized reach was highly disintegrated and structured into jams, whereas further downstream well preserved shrubs and trees prevailed. This apparently reflects differences in the distance of wood transport and shows that in a mountain river wider than the height of trees growing on its banks, wood can be transported long distances along relatively narrow, single‐thread reaches but is preferentially deposited in wide, multi‐thread reaches. Copyright © 2005 John Wiley & Sons, Ltd.
Till deposition by glacier submarginal, incremental thickening
Authors: Evans David J. A. , Hiemstra John F.
Published: September 2005

Macro‐ and micro‐scale sedimentological analyses of recently deposited tills and complex push/squeeze moraines on the forelands of Icelandic glaciers and in a stacked till sequence at the former Younger Dryas margin of the Loch Lomond glacier lobe in Scotland are used to assess the depositional processes involved in glacier submarginal emplacement of sediment. Where subglacial meltwater is unable to flush out subglacial sediment or construct thick debris‐rich basal ice by cumulative freeze‐on processes, glacier submarginal processes are dictated by seasonal cycles of refreezing and melt‐out of tills advected from up‐ice by a combination of lodgement, deformation and ice keel and clast ploughing. Although individual till layers may display typical A and B horizon deformation characteristics, the spatially and temporally variable mosaic of subglacial processes will overprint sedimentary and structural signatures on till sequences to the extent that they would be almost impossible to classify genetically in the ancient sediment record. At the macro‐scale, Icelandic tills display moderately strong clast fabrics that conform to the ice flow directions documented by surface flutings; very strong fabrics typify unequivocally lodged clasts. Despite previous interpretations of these tills as subglacial deforming layers, micro‐morphological analysis reveals that shearing played only a partial role in the emplacement of till matrixes, and water escape and sediment flowage features are widespread. A model of submarginal incremental thickening is presented as an explanation of these data, involving till slab emplacement over several seasonal cycles. Each cycle involves: (1) late summer subglacial lodgement, bedrock and sediment plucking, subglacial deformation and ice keel ploughing; (2) early winter freeze‐on of subglacial sediment to the thin outer snout; (3) late winter readvance and failure along a decollement plane within the till, resulting in the carriage of till onto the proximal side of the previous year's push moraine; (4) early summer melt‐out of the till slab, initiating porewater migration, water escape and sediment flow and extrusion. Repeated reworking of the thin end of submarginal till wedges produces overprinted strain signatures and clast pavements. Copyright © 2005 John Wiley & Sons, Ltd.
Effect of dyke construction on water dynamics in the flooding savannahs of Venezuela
Authors: Smith J. K. , Chacón‐Moreno E. J. , Jongman R. H. G. , Wenting Ph. , Loedeman J. H.
Published: September 2005

In the flooded savannahs water is the main factor determining the ecosystem and its change. During flooding, the level of water and the duration of flooding are highly dependent on the relative height position of the ecosystem unit. To understand the spatial processes in the ecosystem one must know the water dynamics in the area. In order to quantify the water content during the year, a digital elevation model (DEM) is needed.

Several areas in the Llanos de Orinoco have been dyked (modulos). A digital elevation model has been developed on a level of the dyked area of the modulo of Hato el Frio. Flooding has been studied at the regional level and a DEM has been developed for the modulo area. For the construction of the DEM various sources were explored for height information. Field measurements with GPS were necessary.

After the high flooding period downstream of the dykes the area is totally dry. In the transition period between the dry and the wet season the distribution of water shows a clear influence of the dyke. In the natural situation the natural height differences create a complex system of sinks. The dyke construction has created a large artificial sink. Modulos form sinks by their banks preventing the outflow of the water. With the help of a DEM, inundation can be modelled with relatively little field research. Copyright © 2005 John Wiley & Sons, Ltd.
Incipient weathering rind development on introduced machine‐polished granite discs in an Arctic alpine environment, northern Scandinavia
Authors: Dixon John C. , Campbell Sean W. , Thorn Colin E. , Darmody Robert G.
Published: September 2005

Weathering rinds, zones of alteration on the exterior surfaces of rock outcrops and coarse unconsolidated surficial debris are widely used by geomorphologists and Quaternary geologists as indicators of the relative age of landforms and landscapes. Additionally they provide unique insights into the earliest stages of rock and mineral weathering, yet the origin of these alteration zones is relatively poorly understood. This lack of understanding applies especially to the initial stages of rind formation. The study reported in this paper has two principal objectives. The first is to use lightly polished granite discs inserted in soil profiles under several different plant communities in an Arctic alpine environment for a period of four or five years to investigate the nature of incipient weathering rind development. The second is to investigate the factors responsible for spatial variability in the nature and rates of rind formation.

Incipient weathering rind development on the outer edges of the granite discs is observable and measurable over a period of time as short as four years in the mild Arctic alpine environment of Swedish Lapland. The earliest stages of rind development involve the development of a porous structure consisting of a combination of pits and fractures which have been solutionally enlarged and modified. Solution appears to be preferentially concentrated on the surfaces of feldspars and, to a lesser extent, quartz. In addition, iron oxides are present along grain boundaries and in grain interiors and are interpreted to have been derived from the oxidation of ferromagnesian minerals. Spatial variability in weathering rind development appears to be particularly driven by differences in moisture but is not related to soil pH. Copyright © 2005 John Wiley & Sons, Ltd.
A learning rule for place fields in a cortical model: Theta phase precession as a network effect
Authors: Scarpetta Silvia , Marinaro Maria
Published: September 2005

We show that a model of the hippocampus introduced recently by Scarpetta et al. (2002, Neural Computation 14(10):2371–2396) explains the theta phase precession phenomena. In our model, the theta phase precession comes out as a consequence of the associative‐memory‐like network dynamics, i.e., the network's ability to imprint and recall oscillatory patterns, coded both by phases and amplitudes of oscillation. The learning rule used to imprint the oscillatory states is a natural generalization of that used for static patterns in the Hopfield model, and is based on the spike‐time‐dependent synaptic plasticity, experimentally observed.

In agreement with experimental findings, the place cells' activity appears at consistently earlier phases of subsequent cycles of the ongoing theta rhythm during a pass through the place field, while the oscillation amplitude of the place cells' firing rate increases as the animal approaches the center of the place field and decreases as the animal leaves the center. The total phase precession of the place cell is lower than 360°, in agreement with experiments. As the animal enters a receptive field, the place cells' activity comes slightly less than 180° after the phase of maximal pyramidal cell population activity, in agreement with the findings of Skaggs et al. (1996, Hippocampus 6:149–172). Our model predicts that the theta phase is much better correlated with location than with time spent in the receptive field. Finally, in agreement with the recent experimental findings of Zugaro et al. (2005, Nature Neuroscience 9(1):67–71), our model predicts that theta phase precession persists after transient intrahippocampal perturbation. © 2005 Wiley‐Liss, Inc.
Silica sol‐gel monolithic materials and their use in a variety of applications
Authors: Kato Masaru , Sakai‐Kato Kumiko , Toyo'oka Toshimasa
Published: September 2005

Sol‐gel technology was first discovered in the late 1800s, but it was not until the early 1970s that renewed interest in the technique was generated, when monolithic inorganic gels were formed at low temperature. In this review, we introduce the sol‐gel reaction and the properties of the gel matrix in the first half and the applications of the matrix in the latter half.
Relationship between damaged fraction and reflected spectra of denaturing tissues
Authors: Yoshimura Hiroyuki , Viator John A. , Jacques Steven L.
Published: September 2005

Background and Objectives

During thermal therapy of tissue, such as induced by microwave heating, the initiation of denaturation should be monitored for proper thermal dosage. Additionally, denaturation should be confined to the pathologic volume, while preserving surrounding healthy tissue. The relationship between the damaged fraction and reflected spectra of denaturing tissues was investigated for a variation of the temperature of the tissues.

Study Design/Materials and Methods

Denaturation of muscle, liver, and milk was studied in vitro by measuring the temperature‐varying reflectance spectrum as heating occurs. A high‐resolution fiber optic spectrometer was used to measure the reflectance changes. Temperature was monitored using a thermocouple embedded within the tissue along the side of the optical fiber probe.

Results

The values of average free energy to initiate denaturation in muscle and liver at about 60°C were 94.8 and 96.3 kJ/mole, respectively. The reflectance spectra increased in amplitude for muscle and liver, and the peak shifted from approximately 700 to 720 nm in accordance with the damage fraction of tissue. The reflectance spectrum for milk was essentially unchanged.

Conclusions

Spectral changes from heated muscle and liver reflect denaturation of proteins contained therein. The spectral information at 800 nm can be used to determine the average free energy for the initiation of denaturation. Lasers Surg. Med. © 2005 Wiley‐Liss, Inc.