TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Sahoo, Himansu S. A1 - Chand, Dillip Kumar T1 - Anisotropic effect of the nitrate anion-manifestation of diamagnetic proton chemical shifts in the 1H NMR spectra of NO3-coordinated complexes N2 - The anisotropic effect of the planar nitrate anion NO3- has been ab initio calculated employing the Nucleus- Independent Chemical Shift (NICS) concept of von Ragué Schleyer and visualized as Iso-Chemical-Shielding Surfaces (ICSSs) of various (de)shieldings. Complexation-induced shifts in the 1H NMR spectra of nitrate/metal complexes or nitrate/receptor supramolecules can be separated now into anisotropic influences of the suitably coordinated nitrate anions and effects originating from differential sources. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040402008005814 U6 - https://doi.org/10.1016/j.tet.2008.03.063 ER - TY - JOUR A1 - Devi, Lekshmi Sudha A1 - Al-Suti, Mohammed K. A1 - Dosche, Carsten A1 - Khan, Muhammad S. A1 - Friend, Richard H. A1 - Köhler, Anna T1 - Triplet energy transfer in conjugated polymers : I. Experimental investigation of a weakly disordered compound N2 - Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. Here, we have investigated triplet diffusion using a model compound that has weak energetic disorder. The Dexter-type triplet energy transfer is found to be thermally activated down to a transition temperature T- T, below which the transfer rate is only weakly temperature dependent. We show that above the transition temperature, Dexter energy transfer can be described within the framework of Marcus theory. We suggest that below T-T, the nature of the transfer changes from phonon-assisted hopping to quantum-mechanical tunneling. The lower electron-phonon coupling and higher electronic coupling in the polymer compared to the monomer results in an enhanced triplet diffusion rate. Y1 - 2008 ER - TY - JOUR A1 - Charbonnière, Loic J. A1 - Hildebrandt, Niko T1 - Lanthanide complexes and quantum dots : a bright wedding for resonance energy transfer N2 - In this microreview we describe the principle of Forster resonance energy transfer (FRET) occurring between closely spaced energy-donor and -acceptor molecules. The theoretical treatment is depicted in relation with the data extractable from spectroscopic measurements. We present the specific case of semiconductor nanocrystals (or quantum dots QDs) as energy donors in FRET experiments and a particular emphasis is put on the specific advantages of these fluorophores with regard to both their exceptional photophysical properties and their nanoscopic morphology. In a following section, the special attributes of luminescent lanthanide complexes (LLCs) are outlined with illustrations of properties such as their characteristic emission spectra, long-lived luminescence, and large "Stokes shift". Finally, the successful combination of LLCs and QDs in FRET experiments is demonstrated, showing the unrivaled benefits of this singular marriage, opening doors for energy transfer at very large distances and excellent sensitivity of detection within the frame of time-resolved fluoroimmunoassays. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008). Y1 - 2008 ER - TY - JOUR A1 - Tsukamoto, Junko A1 - Haebel, Sophie A1 - Valenca, Gustavo P. A1 - Peter, Martin G. A1 - FRanco, Telma T. T1 - Enzymatic direct synthesis of acrylic acid esters of mono- and disaccharides N2 - Background: There is an increased need to replace materials derived from fossil sources by renewables. Sugar- cane derived carbohydrates are very abundant in Brazil and are the cheapest sugars available in the market, with more than 400 million tons of sugarcane processed in the year 2007. The objective of this work was to study the prepn. of sugar acrylates from free sugars and free acrylic acid, thus avoiding the previous prepn. of protected sugar derivs., such as glycosides, or activated acrylates, such as vinyl acrylate. Results: Lipase catalyzed esterification of three mono- and two disaccharides with acrylic acid, in the presence or absence of mol. sieves was investigated. The reactions were monitored by high-performance liq. chromatog. (HPLC) and the products were analyzed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. The main products are mono- and diacrylates, while higher esters are formed as minor products. The highest conversion to sugar acrylates was obsd. for the D-glucose and D- fructose, followed by D-xylose and D-maltose. Mol. sieves had no pronounced effect on the conversion. Conclusions: A feasible method is described to produce and to characterize sugar acrylates, including those contg. more than two acrylate groups. The process for prodn. of these higher esters could potentially be optimized further to produce mols. for crosslinking in acrylate polymn. and other applications. The direct enzymic esterification of free carbohydrates with acrylic acid is unprecedented. [on SciFinder (R)]. Y1 - 2008 UR - http://www3.interscience.wiley.com/journal/117946200/grouphome/home.html SN - 0268-2575 ER - TY - JOUR A1 - López-Franco, Yolanda L. A1 - Calderón de la Barca, Ana M. A1 - Valdez, Miguel A. A1 - Peter, Martin G. A1 - Rinaudo, Marguerite A1 - Chambat, Gérard A1 - Goycoolea, Francisco M. T1 - Structural characterization of mesquite (Prosopis velutina) gum and its fractions N2 - Structural and physicochem. characteristics of mesquite gum (from Prosopis velutina) were investigated using FT- IR spectroscopic, mass spectrometric and chromatog. methods. Four fractions (F-I, F-IIa, F-IIb and F-III) were isolated by hydrophobic interaction chromatog. The samples were characterized and analyzed for their monosaccharide and oligomers compn. by high performance anion-exchange chromatog. with pulsed amperometric detection (HPAEC-PAD). L-Arabinose (L-Ara) and D-galactose (D-Gal) were found as the main carbohydrate constituent residues in the polysaccharides from mesquite gum and their ratio (L-Ara/D-Gal) varied within the range 2.54 to 3.06 among the various fractions. Small amts. of D- glucose (D-Glc), D-mannose (D-Man) and D-xylose (D-Xyl) were also detected, particularly in Fractions IIa, IIb and III. IR spectroscopy identified polysaccharides and protein in all the samples. Data from mass spectrometry (MALDI-TOF MS) was consistent with the idea that the structure corresponding to the periphereal chains of Fraction I is predominantly a chain of pentoses attached to uronic acid. [on SciFinder (R)]. Y1 - 2008 UR - http://www3.interscience.wiley.com/journal/77002860/home?CRETRY=1&SRETRY=0 U6 - https://doi.org/10.1002/mabi.200700285 SN - 1616-5187 ER - TY - JOUR A1 - Oliveira, Enio N. A1 - el Gueddari, Nour E. A1 - Moerschbacher, Bruno M. A1 - Peter, Martin G. A1 - Franco, Telma T. T1 - Growth of phytopathogenic fungi in the presence of partially acetylated chitooligosaccharides N2 - Four phytopathogenic fungi were cultivated up to six days in media contg. chitooligosaccharide mixts. differing in av. DP and F A. The three different mixts. were named Q3 (which contained oligosaccharides of DP2-DP10, with DP2-DP7 as main components), Q2 (which contained oligosaccharides of DP2-DP12, with DP2-DP10 as main components) and Q1 (which derived from Q2 and contained oligomers of DP5-DP8 with hexamer and a heptamer as the main components). The novel aspect of this work is the description of the effect of mixts. of oligosaccharides with different and known compn. on fungal growth rates. The growth rate of Alternaria alternata and Rhizopus stolonifer was initially inhibited by Q3 and Q2 at higher concns. Q1 had a growth stimulating effect on these two fungi. Growth of Botrytis cinerea was inhibited by Q3 and Q2, while Q1 had no effect on the growth of this fungus. Growth of Penicillium expansum was only slightly inhibited by higher concns. of sample Q3, while Q2 and Q1 had no effect. The inhibition of growth rates or their resistance toward chitooligosaccharides correlated with the absence or presence of chitinolytic enzymes in the culture media, resp. [on SciFinder (R)] Y1 - 2008 UR - http://www.springerlink.com/content/102966 SN - 0301-486X ER - TY - JOUR A1 - Bringmann, Gerhard A1 - Mutanyatta-Comar, Joan A1 - Maksimenka, Katja A1 - Wanjohi, John M. A1 - Heydenreich, Matthias A1 - Brun, Reto A1 - Müller, Werner E. G. A1 - Peter, Martin G. A1 - Midiwo, Jacob O. A1 - Yenesew, Abiy T1 - Joziknipholones A and B : the first dimeric phenylanthraquinones, from the roots of Bulbine frutescens N2 - From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P- configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells. Y1 - 2008 UR - http://www3.interscience.wiley.com/journal/26293/home?CRETRY=1&SRETRY=0 SN - 0947-6539 ER - TY - JOUR A1 - Rukunga, G. M. A1 - Muregi, F. W. A1 - Omar, S. A. A1 - Gathirwa, J. W. A1 - Muthaura, C. N. A1 - Peter, Martin G. T1 - Anti-plasmodial activity of the extracts and two sesquiterpenes from Cyperus articulatus N2 - Two sesquiterpenes, corymbolone and mustakone, isolated from the chloroform extract of the rhizomes of Cyperus articulatus, exhibited significant anti-plasmodial properties. Mustakone was approximately ten times more active than corymbolone against the sensitive strains of the Plasmodium falciparum. Y1 - 2008 SN - 0367-326X ER - TY - JOUR A1 - Haebel, Sophie A1 - Hejazi, Mahdi A1 - Frohberg, Claus A1 - Heydenreich, Matthias A1 - Ritte, Gerhard T1 - Mass spectrometric quantification of the relative amounts of C6 and C3 position phosphorylated glucosyl residues in starch N2 - The quantification of phosphate bound to the C6 and C3 positions of glucose residues in starch has received increasing interest since the importance of starch phosphorylation for plant metabolism was discovered. The method described here is based on the observation that the isobaric compounds glucose-6-phosphate (Glc6P) and glucose-3- phosphate (Glc3P) exhibit significantly different fragmentation patterns in negative ion electrospray tandem mass spectrometry (MS/MS). A simple experiment involving collision-induced dissociation (CID) MS2 spectra of the sample and the two reference substances Glc3P and Glc6P permitted the quantification of the relative amounts of the two compounds in monosaccharide mixtures generated by acid hydrolysis of starch. The method was tested on well-characterized potato tuber starch. The results are consistent with those obtained by NMR analysis. In contrast to NMR, however, the presented method is fast and can be performed on less than 1 mg of starch. Starch samples of other origins exhibiting a variety of phosphorylation degrees were analyzed to assess the sensitivity and robustness of the method. Y1 - 2008 UR - http://www.sciencedirect.com/science/journal/00032697 SN - 0003-2697 ER - TY - JOUR A1 - Roth, Martin M. A1 - Löhmannsröben, Hans-Gerd A1 - Kelz, A. A1 - Kumke, Michael Uwe T1 - innoFSPEC : fiber optical spectroscopy and sensing Y1 - 2008 SN - 978-0-819-47228-1 ER -