bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organometallic alkane and noble-gas complexes in conventional and supercritical fluids
Authors: Childs Gavin I. , Grills David C. , Sun Xue Z. , George Michael W. 
Published: October 2007

Abstract
Fast time-resolved infrared (TRIR) spectroscopy has been used to study a wide range of organometallic alkane and noble-gas complexes at ambient temperature. We have shown that the reactivity of the n-heptane complexes decreases both across and down Groups V, VI, and VII, and that the corresponding xenon complexes have similar reactivities.
Long-distance charge transport through DNA. An extended hopping model
Authors: Giese Bernd , Spichty Martin , Wessely Stefan 
Published: October 2007

Abstract
Long-distance transfer of a positive charge through DNA can be described by a hopping model. In double strands where the (A:T)n bridges between the guanines are short (n 3), the charge hops only between guanines, and each hopping step depends strongly upon the guanine to guanine distances. In strands where the (A:T)n sequences between the guanines are rather long (n 4), also the adenines act as charge carriers. To predict the yields of the H2O-trapping products one has to take into account not only the charge-transfer rates but also the rates of H2O-trapping reactions.
New approach to silver halide photography using radical cation chemistry
Authors: Gould I. R. , Lenhard J. R. , Muenter A. A. , Godleski S. A. , Farid S. Y. 
Published: October 2007

Abstract
A new mechanism for spectral sensitization of silver halide is described, which can potentially double the sensitivity of photographic emulsions. The photooxidized sensitizing dye is trapped using an organic donor molecule, which fragments to form a cation and a reducing radical, which injects an electron into the conduction band of the silver halide. In this way, two conduction-band electrons can be produced for each absorbed photon.
Electron-transfer dyads suitable for novel self-assembled light-harvesting antenna/electron-transfer devices
Authors: Holzwarth Alfred R. , Katterle Martin , Müller Marc G. , Ma Ying-Zong , Prokhorenko Valentin 
Published: October 2007

Abstract
The synthesis and photophysical and photochemical characterization of four novel bacterio-chlorin-fullerene dyads with fullerene C60 coupled at various positions and by various bridges to the chlorin ring are described. All dyads undergo rapid charge separation in the sub-picosecond to picosecond time range as characterized by time-resolved fluorescence and transient absorption spectroscopy.
Vital role of entropy in photochirogenesis
Authors: Inoue Yoshihisa , Sugahara Norimitsu , Wada Takehiko 
Published: October 2007

Abstract
The effects of temperature, pressure, solvent, and substrate concentration upon several enantio- and diastereodifferentiating photochemical reactions have been investigated and discussed in detail. These entropy-related external factors, which manipulate the weak electronic and steric interactions in the excited state, dynamically control the stereochemical outcome of asymmetric photochemical reactions, and even switch the product chirality. A global view on the "entropy chemistry" and its potential applications are also discussed.
Photosensitization by drugs
Authors: Miranda Miguel A. 
Published: October 2007

Abstract
Certain drugs are known to elicit photosensitivity side effects. A satisfactory understanding of the involved mechanistic aspects is necessary to anticipate the photosensitizing potential. We have used tiaprofenic acid (TPA), a photosensitizing nonsteroidal antiinflammatory drug, to illustrate the methodology followed to address this problem. After studying the photophysical and photochemical properties of TPA, the attention has been directed towards the reactivity of its lowest lying p-p* triplet with biomolecules. Photosensitized lipid peroxidation occurs by a mixed type I (radicals) and type II (singlet oxygen) mechanism. In the case of proteins, the photosensitized reactions include Tyr, Trp, and His photodegradation, protein­protein photocrosslinking and drug­protein photobinding. This involves direct quenching of the drug triplet by the amino acid residues (Tyr and Trp) or by oxygen, followed by singlet oxygen oxidation (His and Trp). With DNA, the studies have included comet assay, induction of single-strand breaks in supercoiled DNA, and reaction with 2'-deoxyguanosine and thymidine. Product studies, together with time-resolved measurements, have shown that the fastest reaction occurs with purine bases, by a mechanism involving both radical and singlet oxygen processes. The employed methodology can be of general use to investigate the mechanistic aspects of photosensitization by drugs.
New polymeric photosensitizers
Authors: Nowakowska Maria , Kepczynski Mariusz , Szczubialka Krzysztof 
Published: October 2007

Abstract
Novel polymeric photosensitizers for singlet oxygen production in water are described. The polymers contain rose bengal (4,5,6,7-tetrachloro-2',4',5',7'­tetraiodo-fluorescein) chromophores covalently attached to the polymer chain. The quantum yields of singlet oxygen formation and photooxidation of phenol in water have been determined. The methods of separation of photosensitizer from the reactants after completion of reaction have been established.
Luminescent sensors and photonic switches
Authors: de Silva A. Prasanna , Fox David B. , Moody Thomas S. , Weir Sheenagh M. 
Published: October 2007

Abstract
The principles of photochemistry continue to fuel progress in luminescent sensors and photonic switches. Examples of sensors based on photoinduced electron transfer (PET) are discussed, including those which form the basis of successful systems used in physiology and medicine. More complex formats usually involve multiple receptors. One progression takes us to lanthanide complexes enabled with sensory capabilities. Another path takes us to molecular-scale implementation of logic gates such as AND and INHIBIT. Such luminescent switches can be enriched by combination with nonluminescent cousins. The latter are based on internal charge-transfer excited states (ICT). An example of rudimentary arithmetic at the molecular scale is presented by running a luminescent AND gate in parallel with a nonluminescent XOR gate. Thus, small molecules can process small numbers for the first time outside of our brains.
Quinone methide intermediates in organic photochemistry
Authors: Wan Peter , Brousmiche Darryl W. , Chen Christy Z. , Cole John , Lukeman Matthew , Xu Musheng 
Published: October 2007

Abstract
Quinone methides are widely encountered reactive intermediates in the chemistry of phenols and related compounds. This paper summarizes our recent progress in uncovering new and general photochemical methods for forming quinone methides of various structural types in aqueous solution. Their mechanism of formation and subsequent chemistry are also discussed. New examples of excited-state intramolecular proton transfer (ESIPT) have been uncovered in these studies. We have also discovered that appropriately designed biphenyls and terphenyls display photochemistry that is best rationalized by highly polarized and planar excited states of these ring systems, which can efficiently lead to the corresponding extended quinone methides.
Molecular design of luminescent metal-based materials
Authors: Yam Vivian Wing-Wah 
Published: October 2007

Abstract
A series of soluble di- and polynuclear transition-metal acetylides with rich luminescence behavior have been designed and successfully isolated. The photophysical and photochemical properties have been studied. Luminescent polynuclear metal complexes have also been obtained based on the metal chalcogenide building block. These high-nuclearity transition-metal chalcogenide complexes have been structurally characterized and shown to display rich luminescence behavior. Various approaches and strategies to design and synthesize luminescent polynuclear metal complexes that may find potential applications as chemosensors and luminescence signalling devices will also be described.
Bioactive natural products as a potential source of new pharmacophores. A theory of memory
Authors: Atta-ur-Rahman  , Choudhary M. Iqbal 
Published: October 2007

Abstract
The plant kingdom offers a rich source of structural biodiversity in the form of a variety of natural products. Our work on new bioactive compounds from medicinal plants has led to the isolation and structure elucidation of a number of exciting new pharmacophores. Bioassay-guided fractionation has recently led to the discovery of a series of new acetylcholinesterase, urease and a-glucosidase inhibitors, antioxidants and other classes of bioactive compounds, which will be presented. A theory based on hydrogen bonding on the chemical basis of memory storage in the brain is presented.
Gains achieved by molecular approaches in the area of lignification
Authors: Boudet Alain-M. , Chabannes Matthieu 
Published: October 2007

Abstract
In this article we highlight the contribution of molecular biology and lignin genetic engineering toward a better understanding of lignin biosynthesis and spatio-temporal deposition of lignin. Specific examples from the literature and from our laboratory will serve to underline the chemical flexibility of lignins, the complexity of the regulatory circuits involved in their synthesis, and the specific behavior of different cell types within the xylem. We will also focus on strategies aiming to reduce the lignin content or to modify the lignin composition of plants and present their impact on plant development. We will show that the ectopic expression of a specific transgene may have a different impact, depending on the genetic background, and that plants with a severe reduction in lignin content may undergo normal development. Lignification is currently benefiting enormously from recent developments in molecular biology and transgenesis, and the progress made opens the way for future developments to study how the walls of lignified plant cells are built and organized.
Efficient stereoselective syntheses of piperidine, pyrrolidine, and indolizidine alkaloids
Authors: Enders Dieter , Thiebes Christoph 
Published: October 2007

Abstract
Recent advances in the diastereo- and enantioselective synthesis of piperidine, pyrrolidine, and indolizidine alkaloids, based on the highly stereoselective 1,2-addition to the CN double bond of chiral aldehyde-SAMP/RAMP hydrazones, are described. The enantioselective syntheses of the pyrrolidine alkaloids bgugaine and (2S,12¢R)-2-(12¢-aminotridecyl)-pyrrolidine, a defense alkaloid of the Mexican bean beetle are reported. Furthermore, the SAMP/RAMP-hydrazone method was applied to the syntheses of two 5,8-disubstituted indolizidine alkaloids that have been extracted from neotropical poison-dart frogs. The a-alkylation of aldehyde-SAMP/RAMP hydrazones has been used in the enantioselective synthesis of two epimers of stenusine, a 3-substituted piperidine alkaloid and spreading reagent of the beetle Stenus comma.
Chemistry and biotransformations in the Scrophulariaceae family
Authors: Garbarino J. A. , Fraga B. M. , Hernandez M. G. , Chamy M. C. , Piovano M. 
Published: October 2007

Abstract
One of our research lines has been the chemical studies among Calceolaria species (Scrophulariaceae), from which have been isolated 77 new diterpenes of various skeleton types (labdanes, pimaranes, stemaranes, and stemodanes), all coming from a common bicyclic intermediate, having H-9 and C-20 as a cis relationship and C-11 becomes trans with respect to C-20. Another line of research is bringing out chemical changes on diterpenes obtained from this family, using biological systems as the fungus Giberella fujikuroi and Mucor plumbeus.
Quantitative chemobiology
Authors: Gottlieb Otto R. , de M. B. Borin Maria Renata , de Brito Nei Regis S. 
Published: October 2007

Abstract
One of the mysteries of man's contact with nature concerns the question why shamanism and science so often lead to consistent results in the search for useful natural products. To find clues toward an answer via a coherent chemobiological language, structural and functional information is taken into account. The functional information, given by ethnobotanical codes based on traditional knowledge (via number of useful dicotyledon species), is confronted with the structural information, given by metabolic codes based on micromolecular diversification (via number of occurrences in dicotyledons). The challenge to integrate these databases implies in the development of qualitative (via dahlgrenograms) and quantitative (via Sporne indices) models into an evolutionary framework. The follow-up of ethnobotanical qualifications reveals systematic and evolutionary patterns, susceptible to juxtaposition into a phytochemical background based on gallates (GAL) and caffeates (CAF), regulators of intermediate metabolism. Comparison of the two models of information suggests that the "spectral" features of the GAL and CAF-models are coincident with the ethnobotany-guided food- and medicine-plants respectively. Hence, the complementary nature of food and medicine species can be rationalized by oscillations between GAL/CAF. Analyses of these indicators of toxicity would allow advances in the understanding of mechanisms regulating the production of bioactive products.
Bioactive compounds from coral reef invertebrates
Authors: Higa Tatsuo , Tanaka Junichi , Ohtani Ikuko I. , Musman Musri , Roy Michael C. , Kuroda Ikuma 
Published: October 2007

Abstract
Manzamine A (1) known as a cytotoxin exhibited potent antimalarial activity with 40% recovery 60 days after single intraperitoneal (i.p.) injection against mice infected with the malaria parasite Plasmodium berghei. Pachastrisamine (6), a simple derivative of a sphingosine, isolated from a sponge, Pachastrissa sp. showed a high level of cytotoxicity. New sesquiterpene carbonimidic dichlorides and related aldehydes (8­12) have been isolated as cytotoxic constituents of the sponge Stylotella aurantium and shown to have moderate cytotoxicity. Cyclic undecapeptides, barangamides A­D (13­16), have been isolated from the sponge Theonella swinhoei. Their structures were established by spectroscopic analysis and chemical reaction.
Biodiversity conservation and drug discovery in Suriname. Explorations in nature's combinatorial library
Authors: Kingston David G. I. 
Published: October 2007

Abstract
The preservation of tropical rain forests is an important goal both for the intrinsic value of their cultural and biological diversity and for the well-being of the forest peoples who make these forests their home. In addition, tropical forests are potential sources of new pharmaceutical products which can only be found by chemical prospecting in nature's genetically encoded combinatorial library. A collaborative program to discover potential pharmaceuticals in the rain forest of Suriname is described as part of an effort to integrate biodiversity conservation and drug discovery with economic development. Progress on this project will be reported, including results obtained on the isolation of bioactive diterpenoids, quinones, alkaloids, and polyketides, and the benefits of this general approach to biodiversity and drug discovery will be discussed.
Recent results in the synthesis of ecologically important bioregulators
Authors: Mori Kenji 
Published: October 2007

Abstract
Absolute configuration was established for the following semiochemicals: (S)-polyzonimine (1), (S)-9-methylgermacrene-B (2) and (1S,3S,7R)-3-methyl-a-himachalene (3). The stereoisomers of 2,6-dimethylheptane-1,7-diol monotetrahydropyranyl ether served as useful building blocks for the synthesis of syn- or anti-1,5-dimethylated aliphatic pheromones such as 4 and 5. Synthesis of analogs of the Israeli pine bast scale pheromone 6, which exhibits both pheromonal and kairomonal activities, enabled us to find a strong pheromone mimic 7 without any kairomonal activity.
Molecules and macromolecules involved in chemical communication of scarab beetles
Authors: Leal Walter Soares 
Published: October 2007

Abstract
Chemical communication involves the production and release of specific chemicals (pheromones and other semiochemicals) by the emitter, and the detection and olfactory processing of these signals leading to appropriate behavioral responses in the receiver. In contrast to most of the scarab species investigated to date, the Japanese and Osaka beetles have the ability to detect the allospecific pheromone, which plays a pivotal role in the isolation mechanism between these two species. Each species produces a single enantiomer of japonilure [(Z)-5-(dec1-enyl)oxacyclopentan-2-one], but they have evolved the ability to detect both enantiomers, one as an attractant and the other as a behavioral antagonist (stop signal). There is growing evidence in the literature that the inordinate sensitivity and selectivity of the insect olfactory system is achieved by a combination of various olfactory-specific proteins, namely, odorant-binding proteins (OBPs), odorant receptors (ORs), and odorant-degrading enzymes. The relationship between the pheromone structures and the primary sequences of the proteins suggest that OBPs play a part in the selectivity of the olfactory system in scarab beetles by "filtering" chemical signals during the early olfactory processing (perireceptor events). Nevertheless, it is unlikely that pheromone-binding proteins are "chiral filters" as the Japanese and Osaka beetles each possess only one single binding protein. Upon interaction with negatively charged membranes, OBPs undergo conformational changes that may lead to the release of the ligands.
Strategies for the isolation and identification of trypanocidal compounds from the Rutales
Authors: Vieira Paulo C. , Mafezoli Jair , Pupo Mônica T. , Fernandes João B. , da Silva M. Fátima das G. F. , de Albuquerque Sérgio , Oliva Glaucius , Pavão Fernando 
Published: October 2007

Abstract
Crude extracts of Rutales species were tested in vitro against the trypomastigote form of Trypanosoma cruzi at 4 mg/mL, and 20% of them showed significant activity (80%). Their inhibitory activity against the glycolytic enzyme GAPDH from T. cruzi has also been evaluated at the concentrations of 100 and 200 mg/mL. Additionally, the inhibitory activity of 13 purified coumarins were also assayed against T. cruzi-GAPDH. Chalepin was the most active substance with IC50 = 64 mM. The 3D structure of the complex chalepin-enzyme was elucidated by X-ray crystallography, revealing the architecture of the interactions between the inhibitor and the enzyme active site.
Studies directed toward the preparation of key intermediates for the synthesis of trisporic acids and cassiol
Authors: Colombo María I. , Zinczuk Juan , Mischne Mirta P. , Rúveda Edmundo A. 
Published: October 2007

Abstract
An enantioselective synthesis and resolution of the key White intermediate (3) for the synthesis of trisporic acids are described. Attempts to develop a synthetic route toward the antiulcerogenic compound cassiol (2) by an olefination reaction of 3 and an alternative sequence involving a Michael addition followed by an aldol condensation of an open substrate, are also reported.
Figures-of-merit for the technical development and application of advanced oxidation technologies for both electric- and solar-driven systems (IUPAC Technical Report)
Authors: Bolton James R. , Bircher Keith G. , Tumas William , Tolman Chadwick A. 
Published: October 2007

Abstract
Advanced oxidation technologies (AOTs), which involve the in situ generation of highly potent chemical oxidants, such as the hydroxyl radical (áOH), have emerged as an important class of technologies for accelerating the oxidation (and hence removal) of a wide range of organic contaminants in polluted water and air. In this report, standard figures-of-merit are proposed for the comparison and evaluation of these waste treatment technologies. These figures-of-merit are based on electric-energy consumption (for electric-energy-driven systems) or collector area (for solar-energy-driven systems). They fit within two phenomenological kinetic order regimes: 1) for high contaminant concentrations (electric energy per mass, E
EM, or collector area per mass, A
CM) and 2) for low concentrations (electric energy per order of magnitude, E
EO, or collector area per order of magnitude, A
CO). Furthermore, a simple understanding of the overall kinetic behavior of organic contaminant removal in a waste stream (i.e., whether zero- or first-order) is shown to be necessary for the description of meaningful electric- or solar-energy efficiencies. These standard figures-of-merit provide a direct link to the electric- or solar-energy efficiency (lower values mean higher efficiency) of an advanced oxidation technology, independent of the nature of the system, and therefore allow for direct comparison of widely disparate AOTs. These figures-of-merit are also shown to be inversely proportional to fundamental efficiency factors, such as the lamp efficiency (for electrical systems), the fraction of the emitted light that is absorbed in the aqueous solution, and the quantum yield of generation of active radicals.
Organic photochromism (IUPAC Technical Report)
Authors: Bouas-Laurent Henri , Dürr Heinz 
Published: October 2007

Abstract
This technical report is a general introduction to organic photochromism. The definition of photochromism (PC) is given together with that of words with the ending "chromism", such as thermo-, electro-, piezo-, and tribochromism. Important concepts such as two-photon, gated, dual-mode PC and chirochromism are illustrated. The concept of fatigue (chemical degradation) and the determination of the main photochromic parameters (number of cycles, cyclability, half-life), and the spectrokinetic and mechanistic aspects are discussed. The main families of PC (organic compounds and biological receptors) are illustrated with chemical formulae, and the different types of reactions involved in the photochromic processes (pericyclic reactions, E/Z isomerization, group transfer, etc.) are listed. Some examples of applications to "optical power limiting" substances, photoresponsive materials, and photoswitchable biomaterials are considered.
Atomic weights of the elements 1999 (IUPAC Technical Report)
Authors: Coplen Tyler B. 
Published: October 2007

Abstract
The biennial review of atomic-weight, A
r(E), determinations and other cognate data have resulted in changes for the standard atomic weights of the following elements:

element

From
To

nitrogen

14.006 74 ± 0.000 07
14.0067 ± 0.0002

sulfur

32.066 ± 0.006
32.065 ± 0.005

chlorine

35.4527 ± 0.0009
35.453 ± 0.002

germanium

72.61 ± 0.02
72.64 ± 0.01

xenon

131.29 ± 0.02
131.293 ± 0.006

erbium

167.26 ± 0.03
167.259 ± 0.003

uranium

238.0289 ± 0.0001
238.028 91 ± 0.000 03

Presented are updated tables of the standard atomic weights and their uncertainties estimated by combining experimental uncertainties and terrestrial variabilities. In addition, this report again contains an updated table of relative atomic-mass values and half-lives of selected radioisotopes. Changes in the evaluated isotopic abundance values from those published in 1997 are so minor that an updated list will not be published for the year 1999.
Many elements have a different isotopic composition in some nonterrestrial materials. Some recent data on parent nuclides that might affect isotopic abundances or atomic-weight values are included in this report for the information of the interested scientific community.