Search results for "Spectrum Analysi"
showing 10 items of 287 documents
SDS-facilitated in vitro formation of a transmembrane B-type cytochrome is mediated by changes in local pH.
2011
Abstract The folding and stabilization of α-helical transmembrane proteins are still not well understood. Following cofactor binding to a membrane protein provides a convenient method to monitor the formation of appropriate native structures. We have analyzed the assembly and stability of the transmembrane cytochrome b 559 ′, which can be efficiently assembled in vitro from a heme-binding PsbF homo-dimer by combining free heme with the apo-cytochrome b 559 ′. Unfolding of the protein dissolved in the mild detergent dodecyl maltoside may be induced by addition of SDS, which at high concentrations leads to dimer dissociation. Surprisingly, absorption spectroscopy reveals that heme binding and…
Electrochemical impedance spectroscopy of polyelectrolyte multilayer modified gold electrodes: influence of supporting electrolyte and temperature.
2005
Electrochemical impedance spectroscopy and cyclic voltammetry are employed to characterize poly(styrenesulfonate)/poly(allylamine hydrochloride) multilayers assembled onto cysteamine-modified gold surfaces. The influence of the supporting electrolyte and temperature on the impedance response is studied because of both its practical interest and the need to test further the capillary membrane model recently developed by Barreira et al. [J. Phys. Chem. B 2004, 108, 17973]. The results obtained are interpreted quite satisfactorily in terms of this model, thus providing additional support to its usefulness for the description of ionic transport through polyelectrolyte multilayers. It is observe…
Concurrent fast and slow synchronized efferent phrenic activities in time and frequency domain.
1990
Abstract In urethane-anesthetized or decerebrated vagotomized rabbits efferent multifiber activity of the phrenic nerve was investigated for synchronized activities both in time and frequency domains. When respiratory drive was steadily increased by either an elevation of end-tidal CO2 concentration or i.v. administration of 4-aminopyridine, medium-frequency oscillations (MFO) first increased, then decreased and finally became absent. The power of high-frequency oscillations (HFO) steadily rose with increasing respiratory drive. In contrast to HFO which revealed a unimodal spectral peak of mostly small bandwidth, the MFO spectrum in most cases consisted of a broad complex. This complex in s…
Structure, Spectroscopy, and Spectral Tuning of the Gas-Phase Retinal Chromophore: The β-Ionone "Handle" and Alkyl Group Effect
2005
The low-lying singlet states (i.e. S0, S1, and S2) of the chromophore of rhodopsin, the protonated Schiff base of 11-cis-retinal (PSB11), and of its all-trans photoproduct have been studied in isolated conditions by using ab initio multiconfigurational second-order perturbation theory. The computed spectroscopic features include the vertical excitation, the band origin, and the fluorescence maximum of both isomers. On the basis of the S0-->S1 vertical excitation, the gas-phase absorption maximum of PSB11 is predicted to be 545 nm (2.28 eV). Thus, the predicted absorption maximum appears to be closer to that of the rhodopsin pigment (2.48 eV) and considerably red-shifted with respect to that…
Comparative Studies on IR, Raman, and Surface Enhanced Raman Scattering Spectroscopy of Dipeptides Containing ΔAla and ΔPhe
2012
Three dipeptides containing dehydroresidues (\DeltaAla, \Delta (Z)Phe, and \Delta (E)Phe) were examined by IR, Raman, and surface-enhanced Raman techniques for the first time. The effect of the size and isomer type of the β -substituent in the dehydroresidue on the conformational structure of the peptide was evaluated by using the analysis of IR and Raman bands. Additionally, SERS spectroscopy provided insight into the adsorption mechanism of these species on the metal surface. SERS spectra were recorded at alkaline pH on the silver sol using visible light excitation. The dehydroresidues studied here strongly influenced the SERS profile of the peptides. The most pronounced SERS signal for a…
Transverse chemical interface detection with coherent anti-Stokes Raman scattering microscopy
2011
International audience; Transverse "chemical" interfaces are revealed with a conventional two beam narrowband coherent anti-Stokes Raman scattering microscopy setup in a collinear configuration. The exciting "pump" and "Stokes" beams are focused on the sample in two opposite directions. The subtraction of the two generated anti-Stokes signals gives rise to a signal that is directly proportional to the pure Raman spectrum of the resonant medium. This property is used to highlight an interface between glass and N,N-dimethylformamide (DMF) and recover the pure Raman spectrum of DMF around its 1408 cm−1 vibrational band.
Prediabetes is associated with the modulation of antigen-specific Th1/Tc1 and Th17/Tc17 responses in latent Mycobacterium tuberculosis infection.
2017
Type 2 diabetes mellitus (DM) is associated with the down modulation of Th1, Th2 and Th17 responses in latent Mycobacterium tuberculosis infection but the role of prediabetes (PDM) in this setting is not well understood. To examine the role of CD4+ and CD8+ T cell cytokines in latent tuberculosis (LTB) with coincident PDM, we studied the baseline, mycobacterial, control antigen and mitogen-stimulated T cell cytokine responses in LTB individuals with (LTB-PDM; n = 20) or without (LTB-NDM; n = 20) concomitant prediabetes. LTB-PDM is characterized by diminished frequencies of mono-and dual-functional CD4+ Th1 and Th17 cells and mono-functional Th2 cells at baseline and/or following mycobacteri…
Joziknipholones A and B: The First Dimeric Phenylanthraquinones, from the Roots ofBulbine frutescens
2007
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-co…
IL-21 Regulates the Differentiation of a Human γδ T Cell Subset Equipped with B Cell Helper Activity
2012
Vγ9Vδ2 T lymphocytes recognize nonpeptidic antigens without presentation by MHC molecules and display pleiotropic features. Here we report that coculture of Vγ9Vδ2 cells with phosphoantigen and IL-21 leads to selective expression of the transcription repressor Bcl-6 and polarization toward a lymphocyte subset displaying features of follicular B-helper T (T(FH)) cells. T(FH) like Vγ9Vδ2 cells have a predominant central memory (CD27(+)CD45RA(-)) phenotype and express ICOS, CD40L and CXCR5. Upon antigen activation, they secrete IL-4, IL-10 and CXCL13, and provide B-cell help for antibody production in vitro. Our findings delineate a subset of human Vγ9Vδ2 lymphocytes, which, upon interaction w…
On the impact of side methyl groups on the structure and vibrational properties of β-carotenoids. The case of butadiene and isoprene
2021
Abstract Theoretical consideration about the impact of methyl groups on the structure and vibrational properties of β-carotenoids, using medium size molecules of trans-butadiene and trans-isoprene, are reported. Density functional theory (DFT) calculations with correlation-consistent and polarization-consistent basis sets were applied to trans-1,3-butadiene and trans-isoprene as the smallest building bricks of β-carotenoids. Their structure and harmonic vibrations were estimated in the complete basis set limit (CBS) using the non-linear least square fit. Optimized geometries and harmonic frequencies, obtained with B3LYP and BLYP density functionals and large basis sets, were favorably repro…