bluuebunny/crossref_metadata_2025 huggingface dataset:
Humic matter and contaminants. General aspects and modeling metal ion binding
Authors: Koopal Luuk K. , van Riemsdijk Willem H. , Kinniburgh David G.
Published: October 2007

Humic substances are soil and fresh-water components that play an important role in the binding and transport of both organic and inorganic contaminants. Transport of the contaminants due to ground- and fresh-water dynamics is directly related to the risks associated with contaminations. The mobility of soluble humic substances is related to their interaction with soil mineral particles. Some key references for the binding of organic and inorganic contaminants and for the binding of humics to mineral particles are presented. Humic substances also play a role in the analysis of the contaminants in natural waters and with remediation of water or soil polluted with pesticides, heavy metal ions, and radionuclides. These aspects are illustrated with some examples. The problems that are encountered with the modeling of the binding of contaminants to humics and of heavy metal ions in particular are illustrated by considering the nonideal competitive adsorption model (NICA) extended with electrostatic interactions. The NICA-Donnan model gives quite good results for the description of metal ion binding, as is illustrated for metal ion binding to purified peat humic acid (PPHA). Finally, some remarks are made with respect to the use of the NICA-Donnan model in general purpose speciation programs and of simplified versions of the model for predictions under restricted environmental conditions.
Effect of colloids on radionuclide migration for performance assessment of HLW disposal in Japan
Authors: Kurosawa S. , Ueta S.
Published: October 2007

Colloidal effect is one of the major factors to enhance the migration of radionuclides in groundwater. The experimental and theoretical studies of colloid mobility and colloid-facilitated radionuclide transport for the performance assessment of high-level radioactive waste (HLW) geological disposal is presented in this paper. The major aims of the study are (1) to study the filtration effect on colloids by the engineered barrier system, (2) to study bentonite colloid generation by erosion of the engineered barrier system, and (3) to calculate radionuclide migration with groundwater colloids through fractured rock systems.

Alternative coagulants based on prehydrolyzed forms of aluminium or iron can be more effective than the traditional materials in many cases, but their mode of action is not completely understood, especially with regard to the role of charge neutralization and hydroxide precipitation.

Basic principles of colloid stability and metal ion hydrolysis are briefly reviewed, and the action of hydrolyzing metal coagulants is then discussed, with some examples from recent experimental studies. Although it is possible to interpret results reasonably well in terms of established ideas, there are still some uncertainties that need to be resolved
Toward development of environmentally benign processes catalyzed by transition-metal complexes
Authors: Yamamoto Akio
Published: October 2007

On the basis of fundamental studies on the carbon­oxygen bond cleavage of various carboxylic acid derivatives, novel, atom-efficient, and environmentally benign catalytic processes to convert them into acids, aldehydes, and ketones have been developed.
Ruthenium catalysis in organic synthesis
Authors: Murahashi Shun-Ichi , Takaya Hikaru , Naota Takeshi
Published: October 2007

Ruthenium, rhodium, iridium, and rhenium hydride complexes are highly useful redox Lewis acid and base catalysts. Various substrates bearing hetero atoms are activated by these catalysts and undergo reactions with either nucleophiles or electrophiles under neutral conditions. These types of catalytic reactions are described together with their application to the preparation of various biologically active compounds.
Toward the ideal synthesis. New transition metal-catalyzed reactions inspired by novel medicinal leads
Authors: Wender Paul A. , Bi F. Christopher , Gamber Gabriel G. , Gosselin Francis , Hubbard Robert D. , Scanio Marc J. C. , Sun Robert , Williams Travis J. , Zhang Lei
Published: October 2007

Studies in our laboratory are directed at the advancement of synthesis, biology, and medicine. This lecture will focus on new transition metal-catalyzed reactions that have been inspired by biologically potent targets such as phorbol and Taxol® and by the more general interest in producing syntheses that are concise, efficient, cost- and resource-effective, environmentally benign, quick, and simple to conductin essence, ideal. A special emphasis in our program is placed on new transition metal-catalyzed reactions that, in the absence of catalyst, would be forbidden or difficult to achieve. We have thus far reported the first examples of intramolecular metal-catalyzed [4+2], [5+2], and [4+4] cycloadditions, reactions that produce 6-, 7-, and 8-membered rings, respectively. Recent advances in our [5+2] cycloaddition studies will be presented, including new catalysts for relative and absolute stereochemical control. We will also describe recyclable catalysts that can be used in water, thereby minimizing cost and environmental concerns about solvent waste streams. New multicomponent reactions will also be presented. Finally, we will report a new [6+2] cycloaddition that produces an 8-membered ring.
Arene chromium complexes with functionalized anellated rings. Selective formation of highly substituted polycycles
Authors: Butenschön Holger
Published: October 2007

Tricarbonylchromium complexes of benzocyclobutenone, benzocyclobutenedione, and 1,3-indandione are readily prepared by hydrolysis of the complexes of the corresponding acetals. Reduction of the benzocyclobutenone complex gives rise to an oxy-anion-driven ring opening to the corresponding ortho-quinodimethane intermediate, which can be trapped with dienophiles. Addition of 1-ethoxy-1-lithioethene allows a stereoselective ring expansion followed by an anionic ketol rearrangement with complete diastereoselectivity. Addition of 1-lithio-1-methoxyallene gives rise to a rare anionic 1-vinylcyclobutenol-cyclohexadienol rearrangement. Diaddition of alkenylmetal reagents at both keto groups in benzoyclobutenedione complexes causes dianionic oxy-Cope rearrangements to occur at ­78 °C, which are followed by diastereoselective intramolecular aldol additions. In some cases, a completely regioselective mono hydrolysis of di(enolates) was observed. Dianionic oxy-Cope rearrangements can also be realized with unstrained benzil derivatives giving 1,6-hexanediones and the corresponding aldol adducts. The 1,2,3-indantrione complex is obtained by oxidation of the 1,3-indandione complex with dimethyldioxirane in good yield and reacts with its central ketone group in hetero Diels­Alder cycloadditions.
Selective organometallic syntheses from molecular pools
Authors: Catellani Marta
Published: October 2007

A new methodology is described, consisting of the use of molecular pools in palladium-catalyzed sequential processes occurring under mild conditions with high selectivity. These reactions involve palladacycle formation from aryl iodide, palladium, and norbornene, the latter behaving as a second catalyst that is first incorporated into the metallacycle and expelled at the end of the process. Selective alkylation or arylation of the arene nucleus occurring by oxidative addition/reductive elimination of palladacycles are coupled, after norbornene expulsion, with C­H or C­C bond-forming reactions such as hydrogenolysis, olefin insertion, arylboronic coupling, etc. The variety of possible combinations offers a powerful tool for the selective synthesis of unusual and not readily accessible aromatics.
Recent studies on asymmetric hydrogenation. New catalysts and synthetic applications in organic synthesis
Authors: Genet Jean Pierre
Published: October 2007

CODRu(h3methylallyl)2 is a versatile starting material for the preparation of a wide range of chiral bisphosphines ruthenium(II) complexes: (P*P)Ru(h3methylallyl)2 2, Ru[X4(P*P)2] 3, and cationic monohydride ruthenium complex 4. A facile synthesis of new C2 electron-rich chiral phosphines, bis(phosphetano)benzene 8 and 1,1¢bis(phosphetano)ferrocene 10 is presented. Dynamic kinetic resolution was used for efficient syntheses of key components of the hexahydroazepane core 16 of balanol and of optically pure Boc-(2S,3R,3S)-iso-dolaproïne 19. Catalyst 4 was used in asymmetric hydrogenation of 22 to give (+)-cis-methyl dihydrojasmonate in high enantioselectivity.
Oxidative polycyclizations with rhenium(VII) oxides
Authors: Keinan Ehud , Sinha Subhash C.
Published: October 2007

The consecutive oxidative polycyclization reaction with rhenium(VII) oxides represents a highly stereoselective synthetic tool by which polyenes that contain a bis-homoallylic alcohol can be transformed into poly-THF products in a single step. On the basis of a detailed study with model substrates, a set of rules is proposed to predict product configurations in the polycyclization reactions with trifluoroacetylperrhenate. This methodology is exceptionally useful for the synthesis of polyoxygenated carbon skeletons that contain many stereogenic centers, and for the Annonaceous acetogenins in particular. Many of these potent antitumor agents, including solamin, reticulatacin, asimicin, bullatacin, trilobin, trilobacin, squamotacin, rolliniastatin, uvaricin, rollidecins C and D, mucocin, goniocin, and cyclogoniodenin T, as well as chemical libraries of non-natural analogs, were synthesized using the oxidative polycyclization reaction in combination with the Sharpless AD and AE reactions.
Toward the understanding of the mechanism and enantioselectivity of the Pauson­Khand reaction. Theoretical and experimental studies
Authors: Pericàs Miquel A. , Balsells Jaume , Castro Jaume , Marchueta Iolanda , Moyano Albert , Riera Antoni , Vázquez Jordi , Verdaguer Xavier
Published: October 2007

Semiempirical and density functional theory (DFT) calculations have been performed on the key steps of the commonly accepted mechanism of the Pauson­Khand reaction (PKR). In this context, the high reactivity of ynamine complexes in the cycloaddition process has been rationalized on the basis of an anomerically assisted dissociation of CO. Moreover, an explanation has been provided for the correlation between olefin strain and reactivity in the PKR. Inspired by these results, new selective syntheses of cyclopentanones and phenols based on PKR with cyclopropene have been developed. On the other hand, the theoretical analysis of phosphine-substituted dicobalt carbonyl complexes of alkynes has helped in the development of efficient chelating (P,N) and bridging (P,S) ligands for the stereochemical control of the reaction and in the understanding of their action modes.
Addition reactions of heteroatom-COX (X = OR, NR2, COOR) species with alkynes
Authors: Tanaka Masato , Hua Ruimao
Published: October 2007

Heteroatom-COX species where the heteroatom is Cl, S, or Sn and X is alkoxy, amino, or alkoxycarbonyl group were found to add to the triple bond of alkynes regio- and stereoselectively in the presence of Rh, Pd, or Ni catalyst. Scope and limitation of these synthetic reactions were disclosed. Mechanistic study revealed that oxidative addition of these heteroatom-COX bonds readily took place and the resulting adducts were isolable and characterized by X-ray diffraction analysis. Synthetic applications of the catalytic reactions were also demonstrated.
Energy transfers by long-lived species in glows and afterglows
Authors: De Benedictis Santolo , Dilecce Giorgio
Published: October 2007

An overview of the current literature on diagnostics and modeling of energy transfers by long-lived species in N2­CO, He­NO, He­N2­O2, N2­O2, and N2­H2O plasma is given. Energy transfers by vibrationally excited ground-state long-lived species and by electronic molecular and atomic metastables will be highlighted.
New approaches in thermal plasma technology
Authors: Heberlein Joachim
Published: October 2007

Thermal plasmas offer unique advantages for materials processing, such as high fluxes of heat and of reactant species. Recent developments have concentrated on improving control of these fluxes across the boundaries surrounding the thermal plasma. Secondary discharges (hybrid plasma generators) and pulse modulation of the plasma have been some of the approaches for this end. The use of such methods is described for selected applications. Plasma characterization through advanced models and diagnostics are concentrating on description of plasma instabilities and various nonequilibrium conditions. Understanding of these effects will allow their use for enhanced processing methods.
Nonequilibrium discharges in air and nitrogen plasmas at atmospheric pressure
Authors: Kruger Charles H. , Laux Christophe O. , Yu Lan , Packan Denis M. , Pierrot Laurent
Published: October 2007

Diffuse glow discharges were produced in low temperature (<2000 K) atmospheric pressure air and nitrogen plasmas with electron number densities in excess of 1012 cm­3, more than six orders of magnitude higher than in thermally heated air at 2000 K. The measured discharge characteristics compare well with the predictions of a two-temperature kinetic model. Experimental and modeling results show that the steady-state electron number density exhibits an S-shaped dependence on the electron temperature, a behavior resulting from competition between ionization and charge-transfer reactions. Non-Maxwellian effects are shown to be unimportant for the prediction of steady-state electron number densities. The power requirements of DC discharges at atmospheric pressure can be reduced by several orders of magnitude using short repetitive high-voltage pulses. Between consecutive pulses, the plasma is sustained by the finite rate of electron recombination. Repetitive discharges with a 100-kHz, 12-kV, 10-ns pulse generator were demonstrated to produce over 1012 electrons/cm3 with an average power of 12 W/cm3, 250 times smaller than a DC discharge at 1012 cm­3.
Plasma sterilization. Methods and mechanisms
Authors: Moisan Michel , Barbeau Jean , Crevier Marie-Charlotte , Pelletier Jacques , Philip Nicolas , Saoudi Bachir
Published: October 2007

Utilizing a plasma to achieve sterilization is a possible alternative to conventional sterilization means as far as sterilization of heat-sensitive materials and innocuity of sterilizing agents are concerned. A major issue of plasma sterilization is the respective roles of ultraviolet (UV) photons and reactive species such as atomic and molecular radicals. At reduced gas pressure (£10 torr) and in mixtures containing oxygen, the UV photons dominate the inactivation process, with a significant contribution of oxygen atoms as an erosion agent. Actually, as erosion of the spore progresses, the number of UV photons successfully interacting with the genetic material increases. The different physicochemical processes at play during plasma sterilization are identified and analyzed, based on the specific characteristics of the spore survival curves.
Plasma production of nanocrystalline silicon particles and polymorphous silicon thin films for large-area electronic devices
Authors: i Cabarrocas Pere Roca , i Morral Anna Fontcuberta , Lebib Sarra , Poissant Yves
Published: October 2007

Powder formation in silane plasmas has been considered as a technology drawback because it might lead to the formation of macroscopic defects in the deposited layers. Here we summarize our recent efforts in controlling the formation of powder precursors, in particular, nanocrystalline silicon particles, aiming at their incorporation in the films. Indeed, the incorporation of clusters and crystallites along with SiHx radicals allows production of polymorphous silicon films with improved structure and transport properties with respect to standard amorphous silicon films.
Diagnostics and insights on PECVD for gas-barrier coatings
Authors: Creatore Mariadriana , Palumbo Fabio , d'Agostino Riccardo
Published: October 2007

In this work, we report on our last results concerning the polyethyleneterephtalate barrier performance optimization as a function of the chemistry of the SiOx coating, deposited by means of hexamethyldisiloxane/oxygen-fed plasmas ignited in an RF capacitively coupled parallel plates reactor. The influence of the gas feed composition and power on the plasma phase/coating chemistry and on the O2 gas transmission rate has been investigated. The plasma phase has been studied by means of Fourier transform infrared absorption (FT-IR) and optical emission spectroscopies (OES), and the results have been coupled to the film chemistry investigated by means of FT-IR spectroscopy. These techniques show excellent potentialities in the correlation of the plasma phase and film chemistries with the barrier properties of the SiOx-coated polymer, especially when a very good barrier level is required.
Ion-induced damage and annealing of silicon. Molecular dynamics simulations
Authors: Humbird David , Graves David B.
Published: October 2007

A study of the interactions of energetic argon ions with silicon surfaces using molecular dynamics simulations is reported. A dynamic balance between ion-induced damage and recrystallization of the surface is detected. By manipulating ion energy, argon ions are able to both create disordered regions near the surface, and recrystallize these disordered regions.
Plasma treatment of textile fibers
Authors: Höcker Hartwig
Published: October 2007

Low-temperature plasma technologyboth glow discharge under reduced pressure as well as barrier discharge under normal pressureare well established in different industrial applications. Since recently, however, the plasma technology is being introduced in textile industry as well. Fields of application are desizing, functionalizing, and design of surface properties of textile fibers. Plasma technology is suitable to modify the chemical structure as well as the topography of the surface of the material.

Examples of natural as well as man-made fibers prove the enormous potential of plasma treatment of textile materials. It has proven to be successful in shrink-resist treatment of wool with a simultaneously positive effect on the dyeing and printing.

Not only the chemical structure of the surface is modified using different plasma gases but also the topography of the surface. A highly hydrophobic surface with a particular surface topography in contact with water is extremely dust- and dirt-repellent and hence should be also repellent to bacteria and fungi.

Man-made fibers to be used under chemical stress are modified with diffusion-barrier layers on their surfaces without modifying the bulk properties; hence, the stability of those fibers is significantly improved.
Splat formation in plasma-spray coating process
Authors: Mostaghimi Javad , Chandra Sanjeev
Published: October 2007

The paper describes recent developments in modeling formation of plasma-spray coatings. This is a stochastic process in which particle-impact conditions, thermophysical properties, substrate topology, and temperature all play important roles in determining the structure of coating. Specific attention is paid to the simulation of droplet impact and solidification under plasma-spraying conditions. Results of 3-dimensional models show that on a flat surface solidification may cause splashing and break-up of the impacting particle. Undercooling effects result in faster solidification and, thus, smaller extent of spreading. More recent works investigate the effect of surrounding gas on dynamics of impact. It is shown that this could result in entrapment of a bubble under the droplet.
Comparative characterization of high-density plasma reactors using emission spectroscopy from VUV to NIR
Authors: Pu Yi-Kang , Guo Zhi-Gang , Kang Zheng-De , Ma Jie , Guan Zhi-Cheng , Zhang Guang-Yu , Wang En-Ge
Published: October 2007

Emission spectroscopy is used to investigate the effect of inert gas mixing in nitrogen plasmas generated in inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) plasma sources. Vacuum ultraviolet (VUV) emission of resonance lines is used to determine concentration of atomic nitrogen while electron temperature is obtained from optical emission spectra. It is found that electron temperature can be either raised or reduced effectively by mixing helium or argon in a nitrogen discharge. Electron-electron collisions and superelastic collisions involving metastable species are key factors in electron temperature tuning.
Plasma synthesis of catalytic thin films
Authors: Thomann A.-L. , Rozenbaum J. P. , Brault P. , Andreazza C. , Andreazza P. , Rousseau B. , Estrade-Szwarckopf H. , Berthet A. , Bertolini J. C. , Aires F. J. Cadete Santos , Monnet F. , Mirodatos C. , Charles Christine , Boswell R.
Published: October 2007

Plasma sputter deposition is introduced in the field of catalyst preparation. It is shown that growth kinetics and morphologies are determined by ion to neutral flux ratio and kinetic energies of sputtered atoms. Catalytic activity of such catalysts compares very well with classical catalysts.
Genetic diversity and conservation of endangered animal species
Authors: Zhang Ya-ping , Wang Xiao-xia , Ryder Oliver A. , Li Hai-peng , Zhang He-ming , Yong Yange , Wang Peng-yan
Published: October 2007

The loss of biodiversity resulting from extinctions is receiving increasing attention. Over several thousands of animal species have been evaluated and recognized as endangered species. Inbreeding depression has been demonstrated in many wild animal species. Here we sequenced 655-978 bp mitochodrial D-loop region of 32 individuals from four regional giant panda populations. Sixteen haplotypes were observed. AMOVE analysis demonstrated that genetic differentiation was not significant in the overall population, except the Qingling population. The current panda population may recover from a recent severe bottleneck that occurred about 43 000 years ago. Combining with our results on two endangered snub-nosed monkey species and one common hare species, different scenarios for low genetic variation have been discussed. Our results suggest that low genetic variation does not necessary result from a recent bottleneck, and it is not necessarily an indication of the level of endangerment.
Information essential for characterizing a flow-based analytical system (IUPAC Technical Report)
Authors: Zagatto Elias A. G. , van Staden Jacobus F. , Maniasso Nelson , Stefan Raluca I. , Marshall Graham D.
Published: October 2007

Essential aspects for characterization of a flow-based analytical procedure or system are discussed in order to permit the composition of a checklist that will lead to a protocol for reporting results and systems in flow analysis. Aspects more related to chromatographic procedures are not considered. The intent is to present normalized proposals in the field of flow analysis for practitioners and developers.
Future requirements in the characterization of continuous fiber-reinforced polymeric composites (IUPAC Technical Report)
Authors: Moore D. R. , Cervenka A. J.
Published: October 2007

Characterization of continuous fiber-reinforced composites is examined in terms of processing, properties, and structure. Five processing and five property topics are then examined in terms of reviewing some of the historic background in these areas with the aim of identifying current issues and requirements for the future. The topics covered in the processing section are: polymeric matrix, impregnation, interfacial effects, residual stresses, and pre-preg tack. In the mechanical properties section the topics are: choice of standard, recycling and reusability, durability, environmental strength, and toughness. The paper provides a ten-point plan for future requirements.
Nomenclature for the C60-Ih and C70-D5h(6) fullerenes (IUPAC Recommendations 2002)
Authors: Powell W. H. , Cozzi F. , Moss G. P. , Thilgen C. , Hwu R. J.-R. , Yerin A.
Published: October 2007

Fullerenes are a new allotrope of carbon characterized by a closed-cage structure consisting of an even number of three-coordinate carbon atoms devoid of hydrogen atoms. This class was originally limited to closed-cage structures with 12 isolated five-membered rings, the rest being six-membered rings.

Although it was recognized that existing organic ring nomenclature could be used for these structures, the resulting names would be extremely unwieldy and inconvenient for use. At the same time it was also recognized that established organic nomenclature principles could be used, or adapted, to provide a consistent nomenclature for this unique class of compounds based on the class name fullerene. However, it was necessary to develop an entirely new method for uniquely numbering closed-cage systems.

This paper describes IUPAC recommendations for naming and uniquely numbering the two most common fullerenes with isolated pentagons, the icosahedral C60 fullerene and a D
5h-C70 fullerene. It also describes recommendations for adapting organic nomenclature principles for naming fullerenes with nonclosed-cage structures, heterofullerenes, derivatives formed by substitution of hydrofullerenes, and the fusion of organic rings or ring systems to the fullerene cage. Finally, this paper suggests methods for describing structures consisting of two or more fullerene units and for denoting configurations of chiral fullerenes and their derivatives.
Harmonized guidelines for single-laboratory validation of methods of analysis (IUPAC Technical Report)
Authors: Thompson Michael , Ellison Stephen L. R. , Wood Roger
Published: October 2007

Method validation is one of the measures universally recognized as a necessary part of a comprehensive system of quality assurance in analytical chemistry. In the past, ISO, IUPAC, and AOAC International have cooperated to produce agreed protocols or guidelines on the "Design, conduct and interpretation of method performance studies" [1], on the "Proficiency testing of (chemical) analytical laboratories" [2], on "Internal quality control in analytical chemistry laboratories" [3], and on "The use of recovery information in analytical measurement" [4]. The Working Group that produced these protocols/guidelines has now been mandated by IUPAC to prepare guidelines on the single-laboratory validation of methods of analysis. These guidelines provide minimum recommendations on procedures that should be employed to ensure adequate validation of analytical methods.

A draft of the guidelines has been discussed at an International Symposium on the Harmonization of Quality Assurance Systems in Chemical Laboratory, the proceedings from which have been published by the UK Royal Society of Chemistry.
Studies on biodegradable poly(hexano-6-lactone) fibers. Part 3. Enzymatic degradation in vitro (IUPAC Technical Report)
Authors: Hayashi Toshio , Nakayama Kazuo , Mochizuki Masatsugu , Masuda Toshiro
Published: October 2007

Poly(hexano-6-lactone) (PCL*) fibers were enzymatically degraded by a hydrolase in vitro. The extent of degradation of PCL fibers was examined by weight loss, mechanical properties loss such as tensile strength and ultimate elongation decreases, and visual observations by scanning electron microscopy. The in vitro degradation of PCL fibers was carried out using a lipoprotein lipase

(Lipase-PS) as a hydrolase. The kinetic study on the weight loss of PCL fiber accompanying the enzymatic degradation suggested that the degradation of PCL fibers gradually takes place from the surface, not bulk degradation. The rate of degradation was found to depend on draw ratio and crystallinity of the PCL fibers. The strength loss of PCL fibers in the course of degradation took place faster than the weight loss of PCL fibers. Sonic velocity measurements as well as dynamic mechanical properties of PCL fibers were also examined as a function of weight loss of sample fibers with Lipase-PS treatments. It was shown that sonic velocity and value of loss tangent d changed steeply for undrawn PCL fiber in the first step with enzymatic digestion.
Cascade mechanism in a self-regulatory endocrine system. Modeling pulsatile hormone secretion
Authors: Dumrongpokaphan Thongchai , Lenbury Yongwimon
Published: October 2007

Many endocrine systems have been found to incorporate some form of cascade mechanism into their operation. Such a mechanism involves an amplification system where an initial reaction gives rise to the generation of multiple second reactions, each of which sets off multiple third reactions, and so on. Examples will be presented, with special attention paid to the hypothalamus­pituitary­testicular axis. The production and secretion of luteinizing hormone (LH) is governed by the medial-basal region of the hypothalamus. It is well known that the release of LH is a highly regulated process determined by negative and positive feedback, as well as neural components. The presence of gonadatropin-releasing hormone (GnRH) on specific adenohypophyseal cell membrane receptors results in the release of LH, which is then transported systemically to the Leydig cells of the testes. All the factors governing the release of these hormones, as well as a biochemical description of their actions, have not been completely elucidated, nor is the mechanism behind the pulsatile fashion in which the decapeptide GnRH and LH are released clearly explained. We describe how such a cascade mechanism in a self-regulatory system may be modeled and analyzed by a singular perturbation approach, identifying conditions that give rise to episodic hormone secretion or activity. Insightful and valuable interpretations can be made from such analysis of the cascade system.
Microbial computational genomics of gene regulation
Authors: Collado-Vides Julio , Moreno-Hagelsieb Gabriel , Medrano-Soto Arturo
Published: October 2007

Escherichia coli is a free-living bacterium that condensates a large legacy of knowledge as a result of years of experimental work in molecular biology. It represents a point of departure for analyses and comparisons with the ever-increasing number of finished microbial genomes. For years, we have been gathering knowledge from the literature on transcriptional regulation and operon organization in E. coli K-12, and organizing it in a relational database, RegulonDB. RegulonDB contains information of 20­25 % of the expected total sets of regulatory interactions at the level of transcription initiation. We have used this knowledge to generate computational methods to predict the missing sets in the genome of E. coli, focusing on prediction of promoters, regulatory sites, regulatory proteins, operons, and transcription units. These predictions constitute separate pieces of a single puzzle. By putting them all together, we shall be able to predict the complete set of regulatory interactions and transcription unit organization of E. coli. Orthologous genes in other genomes of known co-regulated sets of genes in E. coli, along with their corresponding predicted operons, and their predicted transcriptional regulators, shall permit the extension of the previous goal to many more microbial genomes.
Modeling genome structure and function
Authors: Samudrala Ram
Published: October 2007

The ongoing genomics revolution has led to the creation and enumeration of all the genes encoded within several organisms. The next steps are to catalog all proteins, their structures, and their functions in different contexts. At the same time, scientists have been pursuing experimental and theoretical approaches to integrate this information to gain understanding of the behavior of entire systems. In this work, we provide a framework for obtaining structures for all tractable protein sequences encoded by a genome, and using the resulting structures to aid in understanding function. Our aim is to integrate the output produced with other genomic and proteomic data to create a comprehensive picture of systems and organismal biology.
Molecular basis of sweet taste in dipeptide taste ligands
Authors: Goodman M. , Valle J. R. Del , Amino Y. , Benedetti E.
Published: October 2007

In this presentation, we describe an integrated approach for the molecular basis for sweet taste among dipeptide-based ligands. By comparing the results obtained from X-ray diffraction studies with the conformations from NMR analysis and molecular modeling, we have observed recurring topochemical motifs that agree with previous models for sweet taste. In our examination of the unexplored D zone of the Tinti­Nofre model, we have uncovered a sweet potency enhancing effect of a new set of aralkyl-substitutions on dipeptide ligands, which reveals the importance of aromatic­aromatic interactions in maintaining high potency.
Genetics of sweet taste preferences
Authors: Bachmanov Alexander A. , Reed Danielle R. , Li Xia , Beauchamp Gary K.
Published: October 2007

Inbred mouse strains display marked differences in avidity for sweet solutions due in part to genetic differences among strains. Using several techniques, we have located a number of regions throughout the genome that influence sweetener acceptance. One prominent locus regulating differences in sweetener preferences among mouse strains is the saccharin preference (Sac) locus on distal chromosome 4. Afferent responses of gustatory nerves to sweeteners also vary as a function of allelic differences in the Sac locus, suggesting that this gene may encode a sweet taste receptor. Using a positional cloning approach, we identified a gene (Tas1r3) encoding the third member of the T1R family of putative taste receptors, T1R3. Introgression by serial back-crossing of a chromosomal fragment containing the Tas1r3 allele from the high sweetener-preferring strain onto the genetic background of the low sweetener-preferring strain rescued its low sweetener-preference phenotype. Tas1r3 has two common haplotypes, one found in mouse strains with elevated sweetener preference and the other in strains relatively indifferent to sweeteners. This study, in conjunction with complimentary recent studies from other laboratories, provides compelling evidence that Tas1r3 is equivalent to the Sac locus and that the T1R3 receptor (when co-expressed with taste receptor T1R2) responds to sweeteners. However, other sweetness receptors may remain to be identified.
Discovery of terpenoid and phenolic sweeteners from plants
Authors: Kinghorn A. Douglas , Soejarto Djaja Djendoel
Published: October 2007

Several plant-derived compounds of the terpenoid and phenolic types have commercial use as sweeteners. In our research program directed toward the discovery of additional sweet compounds of these chemical classes, candidate sweet plants for laboratory investigation may be selected after scrutiny of the available literature, as a result of making inquiries in the field, and/or from a limited amount of organoleptic testing. Sweet-tasting plants are extracted according to a standard protocol, and preliminary safety testing is conducted before crude extracts or pure compounds are tasted. The practicality of using Mongolian gerbil electrophysiological and behavioral assays to monitor plant extracts and pure isolates has been examined. A number of sweet-tasting, plant-derived terpenoids and phenolics have been isolated and characterized, including the bisabolane sesquiterpenoids, hernandulcin and

4β-hydroxyhernandulcin, the labdane diterpene glycoside, gaudichaudioside A, the oleanane triterpenoid glycoside, periandrin V, the cycloartane triterpene glycosides, abrusosides A­E, the 3,4-seco-dammarane triterpene glycosides, pterocaryosides A and B, the semisynthetic dihydroflavonol, dihydroquercetin 3-acetate (4'-methyl ether), and the proanthocyanidin, selligueain A. Most of these new compounds are prototype "high-intensity" sweeteners that may be worthy targets for chemical synthesis or for semi-synthetic modification to produce substances with enhanced sweetness properties.
Licorice root. A natural sweetener and an important ingredient in Chinese medicine
Authors: Kitagawa Isao
Published: October 2007

This paper reviews our investigations on the chemical constituents of several kinds of botanically identified licorice roots, which led to the characterization of 13 then-new glucuronide-saponins named licorice-saponins (A­L), apioglycyrrhizin, and araboglycyrrhizin, together with glycyrrhizin and 18α-glycyrrhizin and also of 49 kinds of phenolic compounds and their glycosides (11 then-new). The restoration-promoting activity of licorice-saponin B2 for CCl4-intoxicated hepatocyte function and the structure­sweetness relationship of saponins were discussed. Biologically interesting, but isolable in minor quantities, several licorice-saponins were favorably synthesized from abundantly available glycyrrhizin. With 15 saponins and 49 phenolic compounds (including their glycosides) at hand, chemical evaluation of licorice root processings was undertaken. It was shown that the cortex contained a rich amount of phenolic compounds, whereas the xylem was rich in phenolic glycosides and the saponins contained were richer in the xylem than in the cortex. It was also found that roasted licorice root contained an increased amount of glycyrrhetic acid monoglucuronide, which was secondarily formed from glycyrrhizin through thermal hydrolysis and was known to taste 5 times sweeter than glycyrrhizin.
Chemistry of phenolic compounds of licorice (Glycyrrhiza species) and their estrogenic and cytotoxic activities
Authors: Nomura Taro , Fukai Toshio , Akiyama Toshiyuki
Published: October 2007

The genus Glycyrrhiza consists of about 30 species in which G. glabra, G. uralensis, G. inflata, G. aspera, G. korshinskyi, and G. eurycarpa are generally recognized as licorice because of their sweet taste. Except G. korshinskyi, we examined isoprenoid-substituted phenols of these licorices. Each plant could be characterized by some isoprenoid phenols. We also investigated the biological activities of the Glycyrrhiza phenols. In the course of screening phytoestrogen in medicinal plants, six Glycyrrhiza phenols exhibited the binding affinities for the bovine uterine estrogen receptor. The affinity of a dihydrostilbene with two 3-methyl-2-butenyl (prenyl) groups, gancaonin R, was higher than those of isoflavone phytoestrogens (genistein and daidzein) in dietary foods. The affinities of the other five phenols, a flavanone (liquiritigenin), two prenylflavanones (isobavachin and sigmoidin B), a prenylated coumestan (glycyrol), and a pyranoisoflav-3-ene (glabrene), were similar to that of the dietary isoflavone, genistein or daidzein. Cytotoxic activities of the Glycyrrhiza phenols against human oral tumor cell lines and HIV-infected MT-4 cells were also reviewed.
Design and synthesis of new sweeteners
Authors: Machinami Tomoya , Fujimoto Takashi , Takatsuka Aya , Mitsumori Takeshi , Toriumi Takako , Suami Tetsuo , Hough Leslie
Published: October 2007

Sweet taste induction by alkyl 2,3-di-O-(l-aminoacyloxy)-α-d-glucopyranosides requires a combination of hydrophobic α-alkoxy and hydrophilic vicinal, diequatorially oriented, l-aminoacyloxy units. Pyranoside chair conformations afford the preferred stereochemical arrangements of these residues for optimum interaction with the receptor. For the design of new sweeteners based on sweetness inhibitors, the introduction of a di-O-aminoacyloxy unit as the hydrogen-bonding component was applied to effect their intertransformation. Thus, the known sweetness inhibitor, methyl 4,6-dichloro-4,6-dideoxy-α-d-galactopyranoside, was successfully transformed into sweet-tasting 2,3-di-O-(l-aminoacyl) derivatives. The inhibition of the 4,6-dichloro derivative is therefore competitive. Amongst the related amino-chloro-deoxysugars, methyl 6-chloro-6-deoxy-2,3-di-O-(l-alanyl)-α-d-gluco-pyrano side was found to be a full agonist. Our studies were then extended to disaccharide derivatives based on trehalose. This approach led to new highly intense sweeteners, as dimeric forms of the full agonist 2,3,2',3'-tetra-O-(l-alanyl)-6,6'-dichloro-6,6' -dideoxytrehalose. The derivatives with effective hydrophobic groups on the C-6 and C-6' positions, were found to be up to 800­1000 times sweeter than sucrose.
Novel functions and applications of trehalose
Authors: Higashiyama Takanobu
Published: October 2007

Trehalose is a disaccharide with important functional properties. Although these properties have been recognized for many years, trehalose was not produced on an industrial scale. Recently, a novel enzymatic system for the production of trehalose was developed, and the cost has been dramatically reduced enough to permit widespread application. In the present study, the stabilization mechanism of unsaturated fatty acids by trehalose was found. Furthermore, possible suppressive effects of trehalose on osteoporosis development emerged from our experiments. Trehalose is also expected to be used for various applications in the fields of cosmetics and pharmaceuticals.
Erythritol. Functionality in noncaloric functional beverages
Authors: de Cock Peter , Bechert Claire-Lise
Published: October 2007

Noncaloric functional beverages are a key segment in the rapidly growing functional food market. Erythritol, an all-natural bulk sweetener, offers sensorial as well as functional benefits for use in such beverages. It can improve taste quality by adding body and mouthfeel, and it is capable of masking unwanted off-flavors often associated with intense sweeteners. In addition, erythritol can strengthen the functional concept since it is noncaloric, noncariogenic, and nonglycemic, and it has antioxidant properties.
Fischer carbene complexes. A new tool for heterocyclic synthesis
Authors: Barluenga José
Published: October 2007

This short review covers our contribution in the field of the application of group 6 Fischer carbene complexes toward the synthesis of heterocyclic compounds. Alkenyl and alkynyl carbene complexes are suitable partners in [2+2], [3+2], [4+2], and [4+3] cycloaddition reactions. Moreover, chiral alkenyl carbene complexes react in sequential processes involving an initial Michael addition of a ketone lithium enolate to afford lactones with up to five consecutive stereogenic centers. Based on this strategy, we have devised a new method for the enantioselective synthesis of eight-membered carbocycles.
Development of a general process for the synthesis of highly substituted imidazoles
Authors: Sisko Joseph , Mellinger Mark
Published: October 2007

Several highly substituted imidazoles have been under investigation at GlaxoSmithKline as potential therapies for the treatment of rheumatoid arthritis and have spawned the need for a general synthetic method for their preparation on a multikilogram scale. We describe herein the optimization of a general method for the preparation of aryl-substituted TosMIC reagents and the ease with which they undergo [3+2] cycloadditions with a host of imines, prepared in situ, to generate densely functionalized imidazoles with various substitution patterns in a completely regioselective manner.
Development of a practical synthesis of sumanirole
Authors: Wuts Peter G. M. , Gu Rui Lin , Northuis Jill M. , Kwan Tricia A. , Beck Doris M. , White Michael J.
Published: October 2007

A new synthesis of sumanirole that is being developed to treat Parkinson's disease is described. The basic skeleton is constructed from 8-hydroxyquinoline and elaborated to the key tricylic intermediate 14. Further elaboration affords a 1,2-amino alcohol, which is converted to an aziridine by a new process. Finally, dissolving metal reduction to open the aziridine and protecting group removal affords sumanirole.
Chemical synthesis project. A new yellow carotenoid
Authors: Giger Alfred
Published: October 2007

Naturally occurring colorants have been used in food processing for centuries to give meals an appealing color. In the first half of the 20th century, the newly discovered brilliant azo dyes, amongst other artificial colorants (indol, triphenylmethane, and methine dyes), were used as pigments for food coloration. The toxicity and/or allergenic potential of some of these colorants were discovered much later. One of these pigments with a critical safety profile is the azo dye tartrazine, which exhibits a nicely fresh greenish-yellow color. The use of tartrazine is now banned in several countries and restricted in others due to its unfavorable safety profile.

With the aim of extending the color fan of nature-identical food colorants offered by Roche and therefore offering a less critical colorant to the food industry, a project was initiated at Roche. The goal was to find a safer, naturally occurring pigment with a color hue similar to tartrazine.

This paper discusses the process of how such a project is addressed in industry, as well as how promising candidates were selected from the wide variety of the naturally occurring carotenoids. The syntheses of some of these carotenoids will also be described.
Photoisomerization by Hula-twist. Photoactive biopigments
Authors: Liu Robert S. H.
Published: October 2007

A review of literature on photoisomerization of bilirubin and photoactive yellow protein suggests possible involvement of the volume-conserving Hula-twist (HT) reaction mechanism in their primary photochemical processes. Additional definitive experiments to verify their involvement are proposed. Information related to photoproducts of bacteriorhodopsin, rhodopsin, and phytochrome are reviewed. For carotenoids, because of participation of the longer lived triplet state in, for example, the photosynthetic apparatus, the involvement of HT is probably less likely.

With the aim of extending the color fan of nature-identical food colorants offered by Roche and therefore offering a less critical colorant to the food industry, a project was initiated at Roche. The goal was to find a safer, naturally occurring pigment with a color hue similar to tartrazine.

This paper discusses the process of how such a project is addressed in industry, as well as how promising candidates were selected from the wide variety of the naturally occurring carotenoids. The syntheses of some of these carotenoids will also be described.
New insights into the role of the macular carotenoids in age-related macular degeneration. Resonance Raman studies
Authors: Bernstein Paul S.
Published: October 2007

The human macula uniquely concentrates extraordinarily high levels of two xanthophyll carotenoids, lutein and zeaxanthin. The function, metabolism, and physiology of these yellow pigments are incompletely understood, but they are likely to prevent age-related damage to the foveal region by virtue of their ability to act as free-radical quenching antioxidants and to absorb phototoxic blue light with high efficiency. A wealth of circumstantial evidence suggests that high macular levels of these two carotenoids may protect against age-related macular degeneration (AMD), but definitive prospective clinical studies still remain to be conducted. It is imperative to gain a greater knowledge of the basic biochemical and physiological mechanisms underlying the specific uptake and metabolism of lutein and zea-xanthin in the macula and to develop improved methods of quantifying macular carotenoid levels noninvasively in order to facilitate the rational design of successful interventions against the leading cause of irreversible blindness in the elderly in the developed world. The development of resonance Raman spectroscopic methods for the objective measurement of macular carotenoid levels in living humans with and without AMD will be reviewed.