Search results for "Spectroscopy"
showing 10 items of 10293 documents
Synthesis and photophysical properties of hyperbranhced polyfluorenes containing 2,4,6-tris(tiophen-2-yl)-1,3,5-triazine as the core
2011
A series of new hyperbranched polymers containing a 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine core unit and polyfluorene chain arms have been synthesized via Suzuki coupling, and characterized by NMR, IR and GPC. All the polymers exhibit good thermal stability with a high decomposition temperature. By changing the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine/fluorene ratio the UV-vis absorption and emission spectra can be partially tuned. It has been found that the polymers containing a low ratio of 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine units (P1-P3) have an absorption maximum around 385 nm, localized in the polyfluorene chain, and a shoulder around 425 nm ascribable to a charge transfer stat…
Peptide–Membrane Interactions Monitored by Fluorescence Lifetime Imaging: A Study Case of Transportan 10
2021
The interest on detailed analysis of peptide-membrane interactions is of great interest in both fundamental and applied sciences as these may relate to both functional and pathogenic events. Such interactions are highly dynamic and spatially heterogeneous, making the investigation of the associated phenomena highly complex. The specific properties of membranes and peptide structural details, together with environmental conditions, may determine different events at the membrane interface, which will drive the fate of the peptide-membrane system. Here, we use an experimental approach based on the combination of spectroscopy and fluorescence microscopy methods to characterize the interactions …
A spectrofluorimetric study of binary fluorophore-cyclodextrin complexes used as chiral selectors
2005
Abstract Six binary complexes between three fluorophores (pyrene, xanthone and anthraquinone) and β-cyclodextrin (β-CD) or heptakis-(6-amino)-(6-deoxy)-β-cyclodextrin (am-β-CD) were tested at two pH values (8.0 and 9.0) as chiral selectors for three α-amino acids chosen as model. The conditional constant (β2T) values for ternary complexes (fluorophore-CD-amino acid), determined by means of fluorescence spectroscopy, showed that the binary complexes are suitable receptors for chiral recognition. The effect of α-amino acids on stability and stoichiometric ratio of the binary complexes has also been studied. The binary complexes were in most cases stabilized by adding the ternary agent. The tr…
Fast proton conduction in hydrogen bonded microheterogeneous systems: Bis(2-ethylhexyl)phosphoric acid/N-methyl formamide liquid mixtures
2009
Structural and dynamical properties of bis(2-ethylhexyl)phosphoric acid (HDEHP)/N-methyl formamide (NMF) liquid mixtures in the whole composition range have been investigated by Fourier Transform Infrared spectroscopy (FT-IR), X-rays Diffraction (XRD), and AC complex impedance spectroscopy. Driven by hydrogen bond interactions among HDEHP PO(4)H group and NMF CO and NH groups, and also by steric effects among the HDEHP alkyl chains, the system microstructure is mainly characterized by the coexistence of spatially separated hydrophilic and hydrophobic nanodomains showing local organization and short-range order. The evolution of this structural feature with system composition has been highli…
<title>Iodine and mercury resonance lamps and their spectrum in far UV</title>
2001
Electrodeless iodine, mercury iodide, and mercury radio- frequency discharge lamps have been made to provide effective sources of atomic spectra for analytical spectroscopy providing powerful resonance radiation of iodine and mercury in the 120-253 nm region. The lamps are required and can be used for spectral calibration, resonance absorption, and fluorescence detection techniques, for investigation of atomic characteristics (e.g., branching ratios) and other purposes where intense monochromatic spectra are needed. Production technology, development, and investigation of the UV and VUV emission are described.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downlo…
Synthesis, infrared and M�ssbauer characterization and X-ray crystal structure of 1,10-phenanthrolinium tetrachloromethoxy phenylantimonate(V)
1991
The compound has been characterized by X-ray crystal structure determination, Mossbauer and i.r. spectroscopy. It crystallizes in the monoclinic space groupP21/c (No. 14) witha=24.228(4),b=8.335(2),c=23.975(4) A,β=117.83(3)° andZ=8. Least-squares refinement on 3749 observed reflections gave finalR=0.034 (Rw=0.037). The compound is constituted by [(C6H5)SbCl4OMe]− anions andphenH+cations. The coordination polyhedron about Sb is an octahedron (Sb-Cl 2.416(3), Sb-O 1.962(7) and Sb-C 2.138(9) A). The whole structure is characterized by two short contacts (O(1)⋯N(2) 2.76(1) O(2)⋯N(4) 2.75(1) A) involving the methoxy oxygens of the two independent anionic units [(C6H5)SbCl4OMe]− and two nitrogens…
13C NMR spectra of eudesmanolides I—eudesman-12,6-olides
1987
The 13C NMR spectra of 26 eudesmanolides of natural and synthetic origin have been measured, including the naturally occurring sesquiterpene lactones artemisin, torrentin, rothin-A and rothin-B and several semi-synthetic eudesman-12,6-olides obtained from artemisin. The chemical shift values of the different compounds are compared and the effects of the substituents are discussed.
A novel germacranolide-aminoacid adduct dimer from centaurea aspera
1991
Abstract The novel germacronolide-valine adduct dimer 1 has been isolated from aerial parts of Centaurea aspera var. aspera . Its structure has been determined by spectroscopic methods.
Dunham coefficients of 14N2 from CARS measurements of high vibrational states in a low-pressure discharge
1988
Spectroscopic constants of the X1Σg+ ground state of 14N2 are deduced from CARS spectra recorded in a 4 Torr d.c. N2 glow discharge. Vibrational states up to ν = 14 have been observed but only the 11 lower levels which have a good signal-to-noise ratio have been processed. The Dunham constants that were deduced yield vibrational band centre positions in good agreement with those of Lofthus and Krupenie.
Structure analysis of acetylated and non-acetylated O-linked MUC1-glycopeptides by post-source decay matrix-assisted laser desorption/ionization mass…
1997
We have investigated the potential of structural elucidation of O-linked glycopeptides by post-source decay matrix-assisted laser desorption ionization mass spectrometry (PSD-MALDI-MS). In order to establish detailed fragmentation patterns and to dissect fragment ions with and without carbohydrate content, the same O-linked MUC1-derived glycopeptides with acetylated and non-acetylated sugars were analysed and compared. Furthermore, we were interested to examine possible differences in the fragmentation between glycopeptides with acetylated and non-acetylated sugars. The obtained PSD-MALDI-MS spectra showed a rather complete set of fragmentation data which allows us to localize the glycan on…