Raman study of cation effect on sulfate vibration modes in solid state and in aqueous solutions

International audienceRaman spectra of potassium, sodium, and ammonium sulfates (K2SO4, Na2SO4, and (NH4)2SO4) are reported and analyzed. These sulfates have been investigated under two states: solid (anhydrous and hydrated) salts and aqueous solutions. The effects of monovalent ions (K+ , Na+ , and NH4+) and hydration on the position of Raman lines assigned to internal vibrations of sulfate anion SO42- are discussed. In solid salts, the line position of each Raman peak is shown to decrease with increasing radius of the cation. The main ν1 mode of sulfate molecule is particularly affected. It is emphasized that this sensitivity in solid sulfates vanishes in aqueous solutions. As a consequence, this mode can be probed by Raman spectroscopy as the main signature of SO42- to determine its concentration within a single calibration

Improving the surface brightness-color relation for early-type stars using optical interferometry

The aim of this work is to improve the SBC relation for early-type stars in the $-1 \leq V-K \leq 0$ color domain, using optical interferometry. Observations of eight B- and A-type stars were secured with the VEGA/CHARA instrument in the visible. The derived uniform disk angular diameters were converted into limb darkened angular diameters and included in a larger sample of 24 stars, already observed by interferometry, in order to derive a revised empirical relation for O, B, A spectral type stars with a V-K color index ranging from -1 to 0. We also took the opportunity to check the consistency of the SBC relation up to $V-K \simeq 4$ using 100 additional measurements. We determined the uniform disk angular diameter for the eight following stars: $\gamma$ Ori, $\zeta$ Per, $8$ Cyg, $\iota$ Her, $\lambda$ Aql, $\zeta$ Peg, $\gamma$ Lyr, and $\delta$ Cyg with V-K color ranging from -0.70 to 0.02 and typical precision of about $1.5\%$. Using our total sample of 132 stars with $V-K$ colors index ranging from about $-1$ to $4$, we provide a revised SBC relation. For late-type stars ($0 \leq V-K \leq 4$), the results are consistent with previous studies. For early-type stars ($-1 \leq V-K \leq 0$), our new VEGA/CHARA measurements combined with a careful selection of the stars (rejecting stars with environment or stars with a strong variability), allows us to reach an unprecedented precision of about 0.16 magnitude or $\simeq 7\%$ in terms of angular diameter.Comment: 13 pages, 5 figures, accepted for publication in A&

CPPsite: a curated database of cell penetrating peptides

Delivering drug molecules into the cell is one of the major challenges in the process of drug development. In past, cell penetrating peptides have been successfully used for delivering a wide variety of therapeutic molecules into various types of cells for the treatment of multiple diseases. These peptides have unique ability to gain access to the interior of almost any type of cell. Due to the huge therapeutic applications of CPPs, we have built a comprehensive database ‘CPPsite’, of cell penetrating peptides, where information is compiled from the literature and patents. CPPsite is a manually curated database of experimentally validated 843 CPPs. Each entry provides information of a peptide that includes ID, PubMed ID, peptide name, peptide sequence, chirality, origin, nature of peptide, sub-cellular localization, uptake efficiency, uptake mechanism, hydrophobicity, amino acid frequency and composition, etc. A wide range of user-friendly tools have been incorporated in this database like searching, browsing, analyzing, mapping tools. In addition, we have derived various types of information from these peptide sequences that include secondary/tertiary structure, amino acid composition and physicochemical properties of peptides. This database will be very useful for developing models for predicting effective cell penetrating peptides

Line-mixing effect on NH3line intensities

Line intensities belonging to nine branches of the \uce\ubd2, 2\uce\ubd2and \uce\ubd4vibrational bands of ammonia have been measured between 1000 and 2000cm-1. The laboratory spectra at room temperature (T=295K) were recorded using a high-resolution Fourier transform spectrometer Bruker IFS 120 HR.More than 460 lines with J\ue2\u89\ua412 were analyzed using a non-linear least-squares multi-pressure fitting procedure. The fits were performed with and without including the line mixing effects using 11 experimental spectra recorded at different pressures of pure NH3. On average the line intensities uncertainty is estimated to be 2%. The dependence of the line intensities on the J and K quantum numbers is discussed. The effect of line mixing on the line intensities is analyzed as a function of the rotational quantum numbers, of the branches, and of the bands.On average the values of line intensities obtained in the \uce\ubd4band when taking into account line mixing have been found to be 6% smaller than those obtained using the Voigt profile.The transition dipole moments squared, determined for each line from the measured intensities, exhibit significant rotational dependencies which are mainly caused by vibration-rotation interactions. These moments are discussed as a function of vibrational and rotational states. Finally the measurements are compared with previous measurements and with values from spectroscopic databases.The whole set of line intensities and transition dipole moments are given as supplementary data for use in spectroscopic databases. \uc2\ua9 2013 Elsevier Ltd

Thermal behavior of high-frequency optical phonons in tetragonal BaTiO3 single crystal

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Pressure broadening and shift coefficients in the ν1 and ν3 bands of NH3

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Determination of anion concentration in mixtures solutions by Raman spectrometry and chemometric methods

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