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Various Spectroscopic Methods (various + spectroscopic_methods)
Selected AbstractsFour New Lignans with a Bicyclo[3.3.1]nonadienemethanol Skeleton from Cunninghamia lanceolataHELVETICA CHIMICA ACTA, Issue 10 2009Ching-Kuo Lee Abstract Four unique bicyclo[3.3.1]nonadienemethanol lignans, designated lanceolatanins A (1), B (2), C (3), and D (4), along with one previously known compound, isolariciresinol (5), were isolated from the MeOH extracts of the heartwood of Cunninghamia lanceolata. Their structures were elucidated by application of various spectroscopic methods, including 1D- and 2D-NMR techniques, to their acetylated derivatives 1a, 2a, 3a, and 4a. Their possible biosynthetic formations are also discussed. [source] Poly(styrene- co -glycerol dimethacrylate): Synthesis, characterization, and application as a resin for gel-phase peptide synthesisJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2005Michael Roice Abstract An efficient cross-linked polymer support for solid-phase synthesis was prepared by introducing glycerol dimethacrylate cross-linker to polystyrene network using free radical aqueous suspension polymerization. The support was characterized by various spectroscopic methods. Morphological feature of the resin was analyzed by microscopy. The polymerization reaction was investigated with respect to the effect of amount of cross-linking agent, which in turn vary the swelling, loading, and the mechanical stability of the resin. The solvent uptake of the polymer was studied in relation to cross-linking and compared with Merrifield resin. The stability of the resin was tested in different synthetic conditions used for solid-phase peptide synthesis. Hydroxy group of the support was derivatized to chloro and then amino groups using different reagents and reaction conditions. Efficiency of the support was tested and compared with TentaGelÔ resin by following different steps involved in the synthesis of the 65,74 fragment of acyl carrier protein. The results showed that the poly(styrene- co -glycerol dimethacrylate) (GDMA-PS) is equally efficient as TentaGel resin in peptide synthesis. The purity of the peptides was analyzed by HPLC and identities were determined by mass spectroscopy and amino acid analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4382,4392, 2005 [source] Identification of flurbiprofen and its photoproducts in methanol by gas chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 5 2007Su-Hui Chao Abstract A sample of 10 mm flurbiprofen in methanol (or ethanol) was photoirradiated with sixteen 8 W low-pressure quartz mercury lamps irradiated at 306 nm in a Panchum PR-2000 photochemical reactor. In total, four major photoproducts derived from each sample were observed from the HPLC chromatogram. The photoproducts were separated and their structures elucidated by various spectroscopic methods. Alternatively, using GC-MS, 11 major photoproducts were observed. A reaction scheme of flurbiprofen in methanol is proposed: the photochemical reaction routes occur mainly via esterification and decarboxylation, followed by oxidation with singlet oxygen to produce a ketone, alcohols and other derivatives. Copyright © 2007 John Wiley & Sons, Ltd. [source] Low versus high molecular weight poly(ethylene glycol)-induced states of stem bromelain at low pH: Stabilization of molten globule and unfolded statesBIOPOLYMERS, Issue 5 2006Basir Ahmad Abstract The effect of low, medium, and high molecular weight poly(ethylene glycol) (e.g., PEG-400, -6000, and -20,000) on the structure of the acid unfolded state of unmodified stem bromelain (SB) obtained at pH 2.0 has been studied by various spectroscopic methods. The conformation of stem bromelain at pH 2.0 exhibits substantial loss of secondary structure and almost complete loss of native tertiary contacts and has been termed the acid unfolded state (AU). Addition of PEG-400 to AU led to an increase in the mean residue ellipticity (MRE) value at 222 nm, indicating formation of ,-helical structure. On the other hand, PEG-6000 and 20,000 led to a decrease in the MRE value at 222 nm, indicating unfolding of the AU state. Interestingly, at 70% (w/v) PEG-400 and 40% (w/v) PEG-20,000, MRE values at 222 nm almost approach the native state at pH 7.0 and the unfolded state (6 M GnHCl) of stem bromelain, respectively. The probes for tertiary structure showed formation of nonnative tertiary contacts in the presence of 70% (w/v) PEG-400, while 40% (w/v) PEG-6000 and 20,000 were found to stabilize the unfolded state of SB. An increase in binding of 1-anilino 8-naphthalene sulfonic acid and a decrease in fractional accessibility of tryptophan residues (fa) compared to AU in the presence of 70% PEG-400 indicate that the PEG-400,induced state has a significant amount of exposed hydrophobic patches and is more compact than AU. The results imply that the PEG-400,induced state has characteristics of molten globule, and higher molecular weight PEGs led to the unfolding of the AU state. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 350,359, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Metallocyclo- and Polyphosphazenes Containing Gold or Silver: Thermolytic Transformation into Nanostructured MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 48 2009Josefina Jiménez Dr. Abstract A cyclotriphosphazene bearing two 4-oxypyridine groups on the same phosphorus atom, gem -[N3P3(O2C12H8)2(OC5H4N-4)2] (I), and its analogous polymer [{NP(O2C12H8)}0.7{NP(OC5H4N-4)2}0.3]n (II), have been used to prepare gold or silver, cyclic and polymeric, metallophosphazenes. The following complexes, gem -[N3P3(O2C12H8)2(OC5H4N-4{ML})2] (ML=Au(C6F5) (1) or Au(C6F5)3 (2)), [N3P3(O2C12H8)2(OC5H4N-4{AuPPh3})2][NO3]2 (3), and [N3P3(O2C12H8)2(OC5H4N-4{AgPPh2R})2][SO3CF3]2 (R=Ph (4) or Me (5)) have been obtained. Complexes 1 and 4 are excellent models for the preparation of the analogous polymers [{NP(O2C12H8)}0.7{NP(OC5H4N-4{ML})2}0.3]n (ML=Au(C6F5) (P1), Ag(OSO2CF3)PPh3 (P2)). All complexes have been characterized by elemental analysis, various spectroscopic methods, and mass spectrometry. The polymers were further investigated by thermochemical methods (thermogravimetric analysis) and differential scanning calorimetry. For compounds 1,5 and for the starting phosphazene I, a mixture of different stereoisomers may be expected. The stereochemistry in solution has been studied by variable-temperature NMR spectroscopy studies, which provided evidence for interconversion processes that involve changes in the chirality of a 2,2,-dioxybiphenyl group. A single-crystal X-ray analysis of the gold complex 2 confirmed not only the proposed structure, but also S,S and R,R configurations at the two biphenoxy-substituted phosphorus centers, in contrast to those observed for the precursor I. Pyrolysis of these new metallophosphazenes was also studied. Notably, pyrolysis of the gold derivatives gave macroporous metallic gold sponges without the requirement of either an external reducing agent or a porous support. These materials were all characterized by XRD, TEM, SEM, and energy-dispersive X-ray spectroscopy. En este trabajo se ha usado el ciclotrifosfazeno que tiene dos grupos 4-oxipiridina en el mismo átomo de fósforo, gem -[N3P3(O2C12H8)2(OC5H4N-4)2] (I), y su polímero análogo, [{NP(O2C12H8)}0.7{NP(OC5H4N-4)2}0.3]n(II), para preparar nuevos compuestos de oro o plata, cíclicos o polímeros. Se han obtenido los siguientes complejos, gem -[N3P3(O2C12H8)2(OC5H4N-4{ML})2] [ML=Au(C6F5) (1), Au(C6F5)3 (2)], [N3P3(O2C12H8)2(OC5H4N-4{AuPPh3})2][NO3]2 (3) and [N3P3(O2C12H8)2(OC5H4N-4{AgPPh2R})2][SO3CF3]2 [R=Ph (4) or Me (5)], que a su vez han resultado ser excelentes modelos para preparar los polímeros análogos de oro o plata, [{NP(O2C12H8)}0.7{NP(OC5H4N-4{ML})2}0.3]n[ML=Au(C6F5)(P1), Ag(OSO2CF3)PPh3 (P2)]. Todos los complejos, cíclicos o polímeros, se han caracterizado por análisis elemental, por métodos espectroscópicos y por espectrometría de masas. Los polímeros, además, se han caracterizado por métodos termoquímicos (TGA y DSC). Para 1,5 y para el fosfazeno de partida (I) puede esperarse una mezcla de varios estereoisómeros. Se ha estudiado su estereoquímica en disolución por RMN a temperatura variable, lo que ha indicado la presencia de un proceso de interconversión que implica cambios de quiralidad del grupo 2,2,-dioxibifenilo. La resolución de la estructura cristalina del complejo 2, por difracción de Rayos X, no sólo ha confirmado la estructura propuesta sino que, además, indica una configuración (S,S)- y (R,R)- , a diferencia de lo observado para el precursor I. Se ha estudiado también la pirólisis de estos nuevos metalofosfazenos. Cabe destacar que la pirólisis de los derivados de oro, trímero (1) y polímero (P1), dio esponjas macroporosas de oro metálico sin utilizar un agente reductor externo ni un soporte poroso. Todos estos materiales se han caracterizado por XRD, TEM, SEM y EDAX. [source] | ||||||||||