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papers from the latest issue:
Ultrafast vibrational dynamics of parallel excited state proton transfer reactions in the Green Fluorescent Protein
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Jasper J. van Thor, Craig N. Lincoln, Brendon Kellner, Konstantinos N. Bourdakos, Lee M. Thompson, Michael J. Bearpark, Paul M. Champion, J. Timothy Sage
We present a brief review of the current understanding and analysis of the photocycle of the Green Fluorescent Protein (GFP). GFP is unique to show directed excited state proton transfer (ESPT) in a protein environment, which provides a directional coordinate for the ultrafast proton transfer reactions in contrast with disordered liquids. ESPT proceeds on a picosecond time scale and we consider details of the vibrational response of the chromophore and the protein environment during the course of this reaction. In addition we discuss both experimental and computational methodology and corrections that measure and model vibrational dichroism from polarised pump-probe infrared measurements. For the GFP photocycle, a direct relationship between equilibrium protein side-chain conformation of glutamate 222 and reaction kinetics has been established for the ultrafast ESPT in the fluorescence photocycle. We have resolved the infrared spectral differences between heterogeneous ESPT reaction dynamics that were assigned to the carboxylate of the Glutamate 222 side chain. We additionally discuss photoselection measurements for the molecular interpretation of the vibrational transition dipole moments placed in the X-ray frame as a sensitive probe of the mode character and assess the assignments based on frequency calculations from the analytical second derivative for the isolated chromophore. Dipole gradients can be calculated analytically, or numerically by finite difference. An older software release that displays analytical dipole gradients incorrectly is identified.
Source:Vibrational Spectroscopy, Volume 62
Jasper J. van Thor, Craig N. Lincoln, Brendon Kellner, Konstantinos N. Bourdakos, Lee M. Thompson, Michael J. Bearpark, Paul M. Champion, J. Timothy Sage
We present a brief review of the current understanding and analysis of the photocycle of the Green Fluorescent Protein (GFP). GFP is unique to show directed excited state proton transfer (ESPT) in a protein environment, which provides a directional coordinate for the ultrafast proton transfer reactions in contrast with disordered liquids. ESPT proceeds on a picosecond time scale and we consider details of the vibrational response of the chromophore and the protein environment during the course of this reaction. In addition we discuss both experimental and computational methodology and corrections that measure and model vibrational dichroism from polarised pump-probe infrared measurements. For the GFP photocycle, a direct relationship between equilibrium protein side-chain conformation of glutamate 222 and reaction kinetics has been established for the ultrafast ESPT in the fluorescence photocycle. We have resolved the infrared spectral differences between heterogeneous ESPT reaction dynamics that were assigned to the carboxylate of the Glutamate 222 side chain. We additionally discuss photoselection measurements for the molecular interpretation of the vibrational transition dipole moments placed in the X-ray frame as a sensitive probe of the mode character and assess the assignments based on frequency calculations from the analytical second derivative for the isolated chromophore. Dipole gradients can be calculated analytically, or numerically by finite difference. An older software release that displays analytical dipole gradients incorrectly is identified.
Ultralow concentration β-carotene molecule detection by liquid-core optical fiber resonance Raman spectroscopy
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Jian-Hua Yin, Zhi-Yan Xiao, Zuo-Wei Li
Liquid-core optical fiber-based resonance Raman scattering (LCOF-RRS) that can enhance Raman intensity 109 times has been used to measure β-carotene in CS2 with the concentration ranging from 10−7 to 10−16 M. The 514.5nm excited resonance Raman spectra (ν 1 band) of β-carotene superimposed on a fluorescence background are clearly distinct. The corresponding Raman scattering cross sections (RSCS) were evaluated by comparing the intensity of LCOF-RRS with the intensity of solution fluorescence of β-carotene. Due to the resonance Raman effect and dilution effect, the RSCS enhances remarkably and is comparable with the fluorescence cross section of β-carotene. This work shows that ultralow concentration molecules can be detected by the LCOF-RRS technique. The extreme sensitivity attainable and related structure information of molecule detected by the LCOF-RRS make it a potential analytical tool at ultralow concentration.
Source:Vibrational Spectroscopy, Volume 62
Jian-Hua Yin, Zhi-Yan Xiao, Zuo-Wei Li
Liquid-core optical fiber-based resonance Raman scattering (LCOF-RRS) that can enhance Raman intensity 109 times has been used to measure β-carotene in CS2 with the concentration ranging from 10−7 to 10−16 M. The 514.5nm excited resonance Raman spectra (ν 1 band) of β-carotene superimposed on a fluorescence background are clearly distinct. The corresponding Raman scattering cross sections (RSCS) were evaluated by comparing the intensity of LCOF-RRS with the intensity of solution fluorescence of β-carotene. Due to the resonance Raman effect and dilution effect, the RSCS enhances remarkably and is comparable with the fluorescence cross section of β-carotene. This work shows that ultralow concentration molecules can be detected by the LCOF-RRS technique. The extreme sensitivity attainable and related structure information of molecule detected by the LCOF-RRS make it a potential analytical tool at ultralow concentration.
Quantitative analysis of thiamine hydrochloride in tablets—Comparison of infrared attenuated total reflection, diffuse reflectance infrared and Raman spectroscopy
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Sylwester Mazurek, Roman Szostak
The application of FTIR ATR (Fourier transform infrared attenuated total reflection), DRIFT (diffuse reflectance infrared Fourier transform) and FT Raman spectroscopy for the quantification of thiamine hydrochloride, or vitamin B1, in tablets was compared. PLS (partial least squares) calibration models were built and validated using the spectra of 40 samples containing vitamin B1 and excipients. To evaluate the predictive ability of these models, the relative standard errors of prediction (RSEP) were calculated. In the case of vitamin B1 determination from the Raman data, RSEP error values of 1.5 % and 2.1 % were obtained for the calibration and validation data sets, respectively. When DRIFT spectra were applied, the respective RSEP errors were found to be 2.1 % and 2.2 %. For ATR models, these errors amounted to 3.1 % and 3.2 %, respectively. Commercial tablets containing 25mg of thiamine hydrochloride were quantified using the developed models. Derived concentrations correlated strongly with the results of the reference analysis and yielded recoveries of 99.2–100.8 %. Each of the three applied spectroscopic techniques can be employed as fast and reliable alternatives to the standard pharmacopeial methods of vitamin B1 quantification in tablets. DRIFT spectroscopy has the highest potential to become a routine technique for the quantification of solid mixtures within the pharmaceutical industry.
Source:Vibrational Spectroscopy, Volume 62
Sylwester Mazurek, Roman Szostak
The application of FTIR ATR (Fourier transform infrared attenuated total reflection), DRIFT (diffuse reflectance infrared Fourier transform) and FT Raman spectroscopy for the quantification of thiamine hydrochloride, or vitamin B1, in tablets was compared. PLS (partial least squares) calibration models were built and validated using the spectra of 40 samples containing vitamin B1 and excipients. To evaluate the predictive ability of these models, the relative standard errors of prediction (RSEP) were calculated. In the case of vitamin B1 determination from the Raman data, RSEP error values of 1.5 % and 2.1 % were obtained for the calibration and validation data sets, respectively. When DRIFT spectra were applied, the respective RSEP errors were found to be 2.1 % and 2.2 %. For ATR models, these errors amounted to 3.1 % and 3.2 %, respectively. Commercial tablets containing 25mg of thiamine hydrochloride were quantified using the developed models. Derived concentrations correlated strongly with the results of the reference analysis and yielded recoveries of 99.2–100.8 %. Each of the three applied spectroscopic techniques can be employed as fast and reliable alternatives to the standard pharmacopeial methods of vitamin B1 quantification in tablets. DRIFT spectroscopy has the highest potential to become a routine technique for the quantification of solid mixtures within the pharmaceutical industry.
Discrimination of the geographical origin of Codonopsis pilosula using near infrared diffuse reflection spectroscopy coupled with random forests and k-nearest neighbor methods
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Boxia Li, Yuhui Wei, Haogang Duan, Lili Xi, Xinan Wu
The combination of near infrared (NIR) spectroscopy with chemometrics provides an approach to study Codonopsis pilosula according to its geographical origin. Firstly, principle component analysis (PCA) was used to group samples based on their spectral differences. Random forests (RF) and k-nearest neighbor (KNN) were applied to build the classification models and predict the geographical origins of test samples. Raw and SNV first derivative NIR spectra were compared to develop a robust classification rule. Feature selection by RF using the variable importance returned 4 selected features, and the selected effective wavenumbers were put into KNN to establish the classification model. For independent test set, same total accuracy rate 94% could be achieved using RF and KNN. These results showed that NIR combined with chemometrics might be a suitable method that can be easily implemented to classify C. pilosula.
Source:Vibrational Spectroscopy, Volume 62
Boxia Li, Yuhui Wei, Haogang Duan, Lili Xi, Xinan Wu
The combination of near infrared (NIR) spectroscopy with chemometrics provides an approach to study Codonopsis pilosula according to its geographical origin. Firstly, principle component analysis (PCA) was used to group samples based on their spectral differences. Random forests (RF) and k-nearest neighbor (KNN) were applied to build the classification models and predict the geographical origins of test samples. Raw and SNV first derivative NIR spectra were compared to develop a robust classification rule. Feature selection by RF using the variable importance returned 4 selected features, and the selected effective wavenumbers were put into KNN to establish the classification model. For independent test set, same total accuracy rate 94% could be achieved using RF and KNN. These results showed that NIR combined with chemometrics might be a suitable method that can be easily implemented to classify C. pilosula.
Infrared and Raman spectroscopic studies of alkali bismuth borate glasses: Evidence of mixed alkali effect
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
M. Subhadra, P. Kistaiah
Mixed alkali bismuth borate glasses of composition xLi2O–(30− x) K2O–10 Bi2O3–55 B2O3:5 V2O5 (LK-series) were prepared by melt quench technique. The amorphous nature of these samples was confirmed from their X-ray diffraction. The density of the samples was measured using Archimedes principle and the molar volumes were determined from the density data. The glass transition temperature of the samples was found to vary non-linearly with the Li2O content (x). The spectroscopic properties of glass samples were studied using infrared (IR) and Raman spectroscopic techniques. IR measurements indicate that the network structure of the studied glasses is based on the BiO3 pyramidal and BiO6 octahedral units and also on BO3 and BO4 units. Raman spectra of these alkali combinations with V2O5 present drastic changes in the intensity of various Raman bands. The observation of disappearance and reappearance of some IR and Raman bands and non-linear variation of the peak positions of some of these bands with x is an important result pertaining to the mixed alkali effect in this glass system. Acting as complimentary spectroscopic techniques, both types of measurements IR and Raman revealed that the network structure of the studied glasses is mainly based on BO3 and BO4 units placed in different structural groups, BO3 units being dominant and bismuth exists as BiO3 and BiO6 octahedral units.
Source:Vibrational Spectroscopy, Volume 62
M. Subhadra, P. Kistaiah
Mixed alkali bismuth borate glasses of composition xLi2O–(30− x) K2O–10 Bi2O3–55 B2O3:5 V2O5 (LK-series) were prepared by melt quench technique. The amorphous nature of these samples was confirmed from their X-ray diffraction. The density of the samples was measured using Archimedes principle and the molar volumes were determined from the density data. The glass transition temperature of the samples was found to vary non-linearly with the Li2O content (x). The spectroscopic properties of glass samples were studied using infrared (IR) and Raman spectroscopic techniques. IR measurements indicate that the network structure of the studied glasses is based on the BiO3 pyramidal and BiO6 octahedral units and also on BO3 and BO4 units. Raman spectra of these alkali combinations with V2O5 present drastic changes in the intensity of various Raman bands. The observation of disappearance and reappearance of some IR and Raman bands and non-linear variation of the peak positions of some of these bands with x is an important result pertaining to the mixed alkali effect in this glass system. Acting as complimentary spectroscopic techniques, both types of measurements IR and Raman revealed that the network structure of the studied glasses is mainly based on BO3 and BO4 units placed in different structural groups, BO3 units being dominant and bismuth exists as BiO3 and BiO6 octahedral units.
Temperature-dependent Raman and infrared spectroscopy study on iron–magnesium tourmalines with different Fe content
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Changchun Zhao, Libing Liao, Zhiguo Xia, Xiaoni Sun
Tourmalines with different Fe content have been analyzed by using Raman spectra polarized parallel to b and c-axis at −195°C, 25°C, 250°C, and 450°C and infrared spectroscopy at 25°C, 150°C, and 250°C, respectively. The Raman spectra show that the intensities of both the stretching bands of FeO5(OH) and the deformation bands of [BO3]3− in b direction increase with the total Fe content, and the spectra polarized along c direction of [Si6O18]12− ring and [OH]− shift to lower frequencies. With increasing temperature, the stretching bands of FeO5(OH) in c direction shift to higher frequencies. Meanwhile, the deformation vibration bands of [Si6O18]12− ring enhance significantly, and the asymmetric stretching bands of [Si6O18]12− ring merge into a broad one. The deformation bands of [BO3]3− and the asymmetric stretch bands of [Si6O18]12− ring are weakened at (bb) polarization. The intensities of infrared absorption peak of tourmalines are weakened, and some peaks shift to lower frequencies with the increase of the total Fe content. With the increase of temperature, most infrared absorption peaks shift to lower frequencies. The variation of the Raman and infrared spectra of tourmalines with temperature and Fe content indicate that more replacement of Fe for Mg in Y–O5(OH) octahedron, leads to the deformation of Y–O5(OH) octahedron, and further the deformation of [BO3]3− polyhedron and [Si6O18]12− ring which are connected with Y–O5(OH) octahedron. Further, Mg(Fe)(OH) bonds extend with increasing temperature, leading to the deformation of [SiO4] tetrahedra connected with Y octahedra.
Source:Vibrational Spectroscopy, Volume 62
Changchun Zhao, Libing Liao, Zhiguo Xia, Xiaoni Sun
Tourmalines with different Fe content have been analyzed by using Raman spectra polarized parallel to b and c-axis at −195°C, 25°C, 250°C, and 450°C and infrared spectroscopy at 25°C, 150°C, and 250°C, respectively. The Raman spectra show that the intensities of both the stretching bands of FeO5(OH) and the deformation bands of [BO3]3− in b direction increase with the total Fe content, and the spectra polarized along c direction of [Si6O18]12− ring and [OH]− shift to lower frequencies. With increasing temperature, the stretching bands of FeO5(OH) in c direction shift to higher frequencies. Meanwhile, the deformation vibration bands of [Si6O18]12− ring enhance significantly, and the asymmetric stretching bands of [Si6O18]12− ring merge into a broad one. The deformation bands of [BO3]3− and the asymmetric stretch bands of [Si6O18]12− ring are weakened at (bb) polarization. The intensities of infrared absorption peak of tourmalines are weakened, and some peaks shift to lower frequencies with the increase of the total Fe content. With the increase of temperature, most infrared absorption peaks shift to lower frequencies. The variation of the Raman and infrared spectra of tourmalines with temperature and Fe content indicate that more replacement of Fe for Mg in Y–O5(OH) octahedron, leads to the deformation of Y–O5(OH) octahedron, and further the deformation of [BO3]3− polyhedron and [Si6O18]12− ring which are connected with Y–O5(OH) octahedron. Further, Mg(Fe)(OH) bonds extend with increasing temperature, leading to the deformation of [SiO4] tetrahedra connected with Y octahedra.
Quantification of captopril disulphide as a degradation product in captopril tablets using near infrared spectroscopy and chemometrics
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Julia Aparecida L. Souza, Miracy Muniz Albuquerque, Severino Grangeiro, Maria Fernanda Pimentel, Davi Pereira de Santana, Simone S. Simões
Captopril disulphide (CD) is the major impurity upon captopril degradation. Besides a reduction of the active principle by degradation, the presence of a high amount of CD in a captopril tablet gives a metallic taste to the tablet, which reduces the therapeutic adhesion. Thus, it is important to quantify this impurity in captopril tablets. This work proposes a new methodology to determine this degradation product through near infrared spectroscopy (NIR) and chemometrics. To conduct this study, tablets of a recently manufactured batch were subjected to accelerated degradation using an environmental chamber to enlarge the range of CD in tablets. Tablets with their batch dates expired were also used. Near infrared (NIR) diffuse reflectance spectra of these tablets were recorded in the region between 14,000 and 3800cm−1. The same tablets were also analysed using high performance liquid chromatography (HPLC). Partial least squares (PLS) models were constructed using different pre-processing techniques. The performances of the models were evaluated using an external validation set. In this step, a root mean square error of prediction (RMSEP) of 0.074mg per tablet was obtained, using Savitzky–Golay 1st derivative spectra (15 points windows and 2nd order polynomial). The value of relative standard error (RSD) under repeat conditions was 12%, which is within the limits of the RSD required to determine traces or impurities (20%). The methodology was validated and can easily be used for routine analysis.
Source:Vibrational Spectroscopy, Volume 62
Julia Aparecida L. Souza, Miracy Muniz Albuquerque, Severino Grangeiro, Maria Fernanda Pimentel, Davi Pereira de Santana, Simone S. Simões
Captopril disulphide (CD) is the major impurity upon captopril degradation. Besides a reduction of the active principle by degradation, the presence of a high amount of CD in a captopril tablet gives a metallic taste to the tablet, which reduces the therapeutic adhesion. Thus, it is important to quantify this impurity in captopril tablets. This work proposes a new methodology to determine this degradation product through near infrared spectroscopy (NIR) and chemometrics. To conduct this study, tablets of a recently manufactured batch were subjected to accelerated degradation using an environmental chamber to enlarge the range of CD in tablets. Tablets with their batch dates expired were also used. Near infrared (NIR) diffuse reflectance spectra of these tablets were recorded in the region between 14,000 and 3800cm−1. The same tablets were also analysed using high performance liquid chromatography (HPLC). Partial least squares (PLS) models were constructed using different pre-processing techniques. The performances of the models were evaluated using an external validation set. In this step, a root mean square error of prediction (RMSEP) of 0.074mg per tablet was obtained, using Savitzky–Golay 1st derivative spectra (15 points windows and 2nd order polynomial). The value of relative standard error (RSD) under repeat conditions was 12%, which is within the limits of the RSD required to determine traces or impurities (20%). The methodology was validated and can easily be used for routine analysis.
X-ray structure analysis and vibrational spectra of Furosemide
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Olcay Bolukbasi, Ayberk Yilmaz
In this study, FT-IR, FAR-IR, and FT-Raman spectra of Furosemide were recorded between 4000 and 650cm−1, 700 and 150cm−1 and 4000 and 150cm−1 regions, respectively. In addition, the single crystal, X-ray structure is determined for this molecule. The X-ray analysis showed two alternative orientations; E and Z-form which formed dimer structure by OH…O hydrogen bonds. The theoretical analysis of probable stable conformers of Furosemide was carried out by using DFT method with 6-31G(d,p) basis set while density functional theory (DFT/B3LYP) method with 6-31G(d,p), 6-31G(d) and Sadlej PVTZ as basis sets was used for quantum chemical calculations of geometrical structure and vibrational wavenumbers. Additionally, the anharmonic wavenumbers were calculated by using the same theory with 6-31G(d,p) basis set. A detailed interpretation of the infrared and Raman spectra of Furosemide was made based on total energy distribution (TED). Finally, probable donor–acceptor interactions of E and Z form of the molecule were examined by using NBO analysis.
Source:Vibrational Spectroscopy, Volume 62
Olcay Bolukbasi, Ayberk Yilmaz
In this study, FT-IR, FAR-IR, and FT-Raman spectra of Furosemide were recorded between 4000 and 650cm−1, 700 and 150cm−1 and 4000 and 150cm−1 regions, respectively. In addition, the single crystal, X-ray structure is determined for this molecule. The X-ray analysis showed two alternative orientations; E and Z-form which formed dimer structure by OH…O hydrogen bonds. The theoretical analysis of probable stable conformers of Furosemide was carried out by using DFT method with 6-31G(d,p) basis set while density functional theory (DFT/B3LYP) method with 6-31G(d,p), 6-31G(d) and Sadlej PVTZ as basis sets was used for quantum chemical calculations of geometrical structure and vibrational wavenumbers. Additionally, the anharmonic wavenumbers were calculated by using the same theory with 6-31G(d,p) basis set. A detailed interpretation of the infrared and Raman spectra of Furosemide was made based on total energy distribution (TED). Finally, probable donor–acceptor interactions of E and Z form of the molecule were examined by using NBO analysis.
Raman and IR spectroscopy of manganese superoxide dismutase, a pathology biomarker
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Catalina David, Cristiano d’Andrea, Eloïse Lancelot, Jörg Bochterle, Nicolas Guillot, Barbara Fazio, Onofrio M. Maragò, Angela Sutton, Nathalie Charnaux, Frank Neubrech, Annemarie Pucci, Pietro G. Gucciardi, Marc Lamy de la Chapelle
The vibrational spectrum, Raman and infrared, of manganese superoxide dismutase (MnSOD), is presented. Both Raman and Fourier-Transform (FT) IR spectra of the lyophilised powder of MnSOD strongly suggest that its secondary structure composition is dominated by α-helix and β-sheet which is in good agreement with the crystallographic data. In order to obtain more results on the protein vibrational characterisation and to highlight the suitable experimental conditions a multiwavelength Raman detection was performed at 532, 632.8, 638, 660 and 785nm. Moreover, we studied the protein behaviour during the lyophilisation process in the presence of the phosphate buffer. Our results show significant differences in the protein conformation and stability during freeze drying of the buffered protein solution compared to the aqueous solution.
Source:Vibrational Spectroscopy, Volume 62
Catalina David, Cristiano d’Andrea, Eloïse Lancelot, Jörg Bochterle, Nicolas Guillot, Barbara Fazio, Onofrio M. Maragò, Angela Sutton, Nathalie Charnaux, Frank Neubrech, Annemarie Pucci, Pietro G. Gucciardi, Marc Lamy de la Chapelle
The vibrational spectrum, Raman and infrared, of manganese superoxide dismutase (MnSOD), is presented. Both Raman and Fourier-Transform (FT) IR spectra of the lyophilised powder of MnSOD strongly suggest that its secondary structure composition is dominated by α-helix and β-sheet which is in good agreement with the crystallographic data. In order to obtain more results on the protein vibrational characterisation and to highlight the suitable experimental conditions a multiwavelength Raman detection was performed at 532, 632.8, 638, 660 and 785nm. Moreover, we studied the protein behaviour during the lyophilisation process in the presence of the phosphate buffer. Our results show significant differences in the protein conformation and stability during freeze drying of the buffered protein solution compared to the aqueous solution.
Temperature-induced phase transition in methyldopa sesquihydrate revealed via X-ray diffraction, thermal analysis and Raman spectroscopy
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
P.F. Façanha Filho, P.T.C. Freire, G.P. De Sousa, F.E.A. Melo, A.O. dos Santos, P.R.S. Ribeiro, A.J.D. Moreno, R.J.C. Lima
Methyldopa sesquihydrate (C10H13NO4·1.5H2O) is a substance used in the treatment of hypertension being one of the most widely used drugs in the world. In this work we have studied the stability of this drug as a function of temperature using four different techniques: X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and Raman spectroscopy. From the combination of these techniques we were able to infer about a set of phase transitions during the loss of water from the crystal around the temperatures of 388K (changes only in the lattice modes) and between temperatures 393 and 423K, when all water leaves the crystal and changes in some lattice modes and in some internal modes occur.
Source:Vibrational Spectroscopy, Volume 62
P.F. Façanha Filho, P.T.C. Freire, G.P. De Sousa, F.E.A. Melo, A.O. dos Santos, P.R.S. Ribeiro, A.J.D. Moreno, R.J.C. Lima
Methyldopa sesquihydrate (C10H13NO4·1.5H2O) is a substance used in the treatment of hypertension being one of the most widely used drugs in the world. In this work we have studied the stability of this drug as a function of temperature using four different techniques: X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and Raman spectroscopy. From the combination of these techniques we were able to infer about a set of phase transitions during the loss of water from the crystal around the temperatures of 388K (changes only in the lattice modes) and between temperatures 393 and 423K, when all water leaves the crystal and changes in some lattice modes and in some internal modes occur.
Interaction of quercetin, genistein and its derivatives with lipid bilayers – An ATR IR-spectroscopic study
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Katarzyna Cieślik-Boczula, Jadwiga Maniewska, Grzegorz Grynkiewicz, Wiesław Szeja, Aleksander Koll, Andrzej B. Hendrich
Genistein, a main soy isoflavone, is well known as phytoestrogen and antioxidant but details of its interactions with lipid membranes are poorly understood. The aim of this work was to elucidate the interaction of genistein, its derivatives and quercetin with lipid bilayers using attenuated total reflection infrared spectroscopy technique. Measurements performed mainly on liposomes and assistantly on dehydrated lipid films enabled us to find that studied flavonoids intercalate into phospholipid bilayers. The temperature of chain-melting phase transition for isoflavone-mixed DPPC liposomes was determined. The changes of population of the trans/gauche conformers of lipid chains were studied. They exert rigidifying effect in hydrophobic core of bilayer and due to the formation of hydrogen bonds induce a new spatial arrangement of lipid molecules.
Source:Vibrational Spectroscopy, Volume 62
Katarzyna Cieślik-Boczula, Jadwiga Maniewska, Grzegorz Grynkiewicz, Wiesław Szeja, Aleksander Koll, Andrzej B. Hendrich
Genistein, a main soy isoflavone, is well known as phytoestrogen and antioxidant but details of its interactions with lipid membranes are poorly understood. The aim of this work was to elucidate the interaction of genistein, its derivatives and quercetin with lipid bilayers using attenuated total reflection infrared spectroscopy technique. Measurements performed mainly on liposomes and assistantly on dehydrated lipid films enabled us to find that studied flavonoids intercalate into phospholipid bilayers. The temperature of chain-melting phase transition for isoflavone-mixed DPPC liposomes was determined. The changes of population of the trans/gauche conformers of lipid chains were studied. They exert rigidifying effect in hydrophobic core of bilayer and due to the formation of hydrogen bonds induce a new spatial arrangement of lipid molecules.
A portable 671nm Raman sensor system for rapid meat spoilage identification
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Kay Sowoidnich, Heinar Schmidt, Heinz-Detlef Kronfeldt, Fredi Schwägele
This paper presents a portable Raman sensor system based on a miniaturized optical bench with integrated 671nm microsystem diode laser as excitation light source for the rapid in situ detection of meat spoilage. The system comprises three main components. A handheld measurement head with a dimension of 210mm×240mm×60mm containing a laser driver electronics board, the Raman optical bench, and a battery pack as power supply serves for excitation as well as collection of the Raman signals in backscattering geometry. The signal detection is realized by a custom-designed miniature spectrometer with an optical resolution of 8cm−1 and a dimension of 200mm×190mm×70mm which is fiber-optically connected to the measurement head. To control the spectrometer as well as for data storage a netbook is applied. To point out the ability of the sensor system for the rapid identification of meat spoilage porcine musculus longissimus dorsi (LD) and musculus semimembranosus (SM) were used as test samples. Stored refrigerated at 5°C the meat cuts were investigated in time-dependent measurement series up to 3 weeks after slaughter. Meat Raman spectra with an integration time of 10s can be detected with an excitation laser power of 100mW at the sample. The spectral changes of the Raman data set during storage were analyzed by principal components analysis. Specific periods of age could be discriminated in the Raman spectra which correlate very well with bacterial growth kinetics determined by microbial reference analyses. Thus, fresh meat with low bacterial load can be identified and a discrimination of spoiled samples exceeding the threshold of 106 cfu/cm2 around day 7 post-mortem for both examined meat cuts was possible.
Source:Vibrational Spectroscopy, Volume 62
Kay Sowoidnich, Heinar Schmidt, Heinz-Detlef Kronfeldt, Fredi Schwägele
This paper presents a portable Raman sensor system based on a miniaturized optical bench with integrated 671nm microsystem diode laser as excitation light source for the rapid in situ detection of meat spoilage. The system comprises three main components. A handheld measurement head with a dimension of 210mm×240mm×60mm containing a laser driver electronics board, the Raman optical bench, and a battery pack as power supply serves for excitation as well as collection of the Raman signals in backscattering geometry. The signal detection is realized by a custom-designed miniature spectrometer with an optical resolution of 8cm−1 and a dimension of 200mm×190mm×70mm which is fiber-optically connected to the measurement head. To control the spectrometer as well as for data storage a netbook is applied. To point out the ability of the sensor system for the rapid identification of meat spoilage porcine musculus longissimus dorsi (LD) and musculus semimembranosus (SM) were used as test samples. Stored refrigerated at 5°C the meat cuts were investigated in time-dependent measurement series up to 3 weeks after slaughter. Meat Raman spectra with an integration time of 10s can be detected with an excitation laser power of 100mW at the sample. The spectral changes of the Raman data set during storage were analyzed by principal components analysis. Specific periods of age could be discriminated in the Raman spectra which correlate very well with bacterial growth kinetics determined by microbial reference analyses. Thus, fresh meat with low bacterial load can be identified and a discrimination of spoiled samples exceeding the threshold of 106 cfu/cm2 around day 7 post-mortem for both examined meat cuts was possible.
Water soluble complexes of curcumin with cyclodextrins: Characterization by FT-Raman spectroscopy
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
P.R. Krishna Mohan, G. Sreelakshmi, C.V. Muraleedharan, Roy Joseph
Many recent reports on curcumin, a polyphenol from Curcuma longa, provide mounting evidence on the pharmacological activity of this natural product. However, the pharmaceutical use of this molecule is hampered due to its poor solubility in the aqueous media. Inclusion complex formation with cyclodextrins has been reported as a means to enhance its aqueous solubility. Most of these studies provide infrared (IR) spectroscopic data as an evidence to support inclusion complex formation. However, characterization of the solid inclusion complexes using IR spectroscopy is hindered due to interfering vibrations of cyclodextrin. In this study, fully water soluble complexes of curcumin with three hydroxypropyl derivatives of cyclodextrins were isolated and characterized. Decrease in the intensity of aromatic ring vibrations and shift in peak position from 1626cm−1 observed in Raman spectrum provided fresh insights into the type of interactions occurring in the water soluble complex. A new structure for the inclusion complex has been proposed. From the results it was demonstrated that Raman spectroscopy would provide clearer and better evidence of inclusion complex formation.
Source:Vibrational Spectroscopy, Volume 62
P.R. Krishna Mohan, G. Sreelakshmi, C.V. Muraleedharan, Roy Joseph
Many recent reports on curcumin, a polyphenol from Curcuma longa, provide mounting evidence on the pharmacological activity of this natural product. However, the pharmaceutical use of this molecule is hampered due to its poor solubility in the aqueous media. Inclusion complex formation with cyclodextrins has been reported as a means to enhance its aqueous solubility. Most of these studies provide infrared (IR) spectroscopic data as an evidence to support inclusion complex formation. However, characterization of the solid inclusion complexes using IR spectroscopy is hindered due to interfering vibrations of cyclodextrin. In this study, fully water soluble complexes of curcumin with three hydroxypropyl derivatives of cyclodextrins were isolated and characterized. Decrease in the intensity of aromatic ring vibrations and shift in peak position from 1626cm−1 observed in Raman spectrum provided fresh insights into the type of interactions occurring in the water soluble complex. A new structure for the inclusion complex has been proposed. From the results it was demonstrated that Raman spectroscopy would provide clearer and better evidence of inclusion complex formation.
Graphical abstract
Investigation of the phonon band gap effect on Raman-active optical phonons in BaWO4 crystal
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Jun Suda, Petr G. Zverev
The phonon-dispersion relations of BaWO4 crystal are calculated using the lattice dynamical calculations approach. Spontaneous Raman spectra in the BaWO4 were measured in the temperature range from 10K to 295K, and the temperature dependence of the linewidth of the E g (72cm−1) and A g (926cm−1) Raman modes were analyzed using the lattice dynamical perturbative approach. We found that different behaviors of these two modes in the case of temperature broadening could be attributed to the large energy band gap in the one-phonon density of states (PDOS) resulting in different anharmonic interactions. This phonon band gap limits the number of relaxation mechanisms for internal vibronic modes, i.e., anharmonic processes between the A g (926cm−1) Raman modes and lower energy modes in BaWO4. This leads to a dephasing effect on the A g (926cm−1) mode and the dephasing processes are increased only at high temperatures.
Source:Vibrational Spectroscopy, Volume 62
Jun Suda, Petr G. Zverev
The phonon-dispersion relations of BaWO4 crystal are calculated using the lattice dynamical calculations approach. Spontaneous Raman spectra in the BaWO4 were measured in the temperature range from 10K to 295K, and the temperature dependence of the linewidth of the E g (72cm−1) and A g (926cm−1) Raman modes were analyzed using the lattice dynamical perturbative approach. We found that different behaviors of these two modes in the case of temperature broadening could be attributed to the large energy band gap in the one-phonon density of states (PDOS) resulting in different anharmonic interactions. This phonon band gap limits the number of relaxation mechanisms for internal vibronic modes, i.e., anharmonic processes between the A g (926cm−1) Raman modes and lower energy modes in BaWO4. This leads to a dephasing effect on the A g (926cm−1) mode and the dephasing processes are increased only at high temperatures.
Core–shell structure in copper ferrite–polyaniline nanocomposite: Confirmation by laser Raman spectra
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
M. Balaji, P. Chithra Lekha, D. Pathinettam Padiyan
Laser Raman spectroscopy was used to investigate the presence of core–shell structure in copper ferrite–polyaniline nanocomposites prepared by in situ polymerization method. Laser beams with two excitation powers, 0.3mW and 3mW, were employed to study the ferrite–polyaniline interaction and its changes by the laser induced heating effects. Low energy Raman spectra distinctly displayed polyaniline bands only without bands for CuFe2O4 in all the nanocomposites. This observation attributes polyaniline shell over the CuFe2O4 core particle, since the low energy was not sufficient for the beam to penetrate the polyaniline shell. However, with higher incident energy due to the induced heating effect, there was disturbance of polyaniline shell and the Raman frequencies were shifted depending on the shell thickness. Raman spectra of copper ferrite–polyaniline nanocomposites recorded using higher energy beam were consistent with the low energy Raman spectra of polyaniline samples annealed at three different temperatures of 200, 300 and 400°C respectively for 2h. High-resolution scanning electron microscope study also supports the formation of core–shell structure. It revealed that the average particle size increases with increase of shell thicknesses.
Source:Vibrational Spectroscopy, Volume 62
M. Balaji, P. Chithra Lekha, D. Pathinettam Padiyan
Laser Raman spectroscopy was used to investigate the presence of core–shell structure in copper ferrite–polyaniline nanocomposites prepared by in situ polymerization method. Laser beams with two excitation powers, 0.3mW and 3mW, were employed to study the ferrite–polyaniline interaction and its changes by the laser induced heating effects. Low energy Raman spectra distinctly displayed polyaniline bands only without bands for CuFe2O4 in all the nanocomposites. This observation attributes polyaniline shell over the CuFe2O4 core particle, since the low energy was not sufficient for the beam to penetrate the polyaniline shell. However, with higher incident energy due to the induced heating effect, there was disturbance of polyaniline shell and the Raman frequencies were shifted depending on the shell thickness. Raman spectra of copper ferrite–polyaniline nanocomposites recorded using higher energy beam were consistent with the low energy Raman spectra of polyaniline samples annealed at three different temperatures of 200, 300 and 400°C respectively for 2h. High-resolution scanning electron microscope study also supports the formation of core–shell structure. It revealed that the average particle size increases with increase of shell thicknesses.
Highlights
► Core–shell structure of CuFe2O4–polyaniline corroborated using laser Raman. ► Laser induced heating effect on the shell is in consistent with annealing effect. ► Particle size increases with shell thickness and supports core–shell formation.A study of 18th century Coptic icons of Ibrahim Al-Nasekh using Raman microscopy and gas chromatography–mass spectrometry: Indigo as an organic pigment in Egyptian panel paintings
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
M. Abdel-Ghani, B. Stern, H.G.M. Edwards, R. Janaway
Two Coptic icons were studied, these date from the 18th century and were painted by IbrahimAl-Nasekh and are currently to be found in Saint Mercurius Church, Saint Mercurius Monastery in Old Cairo, Egypt. The analytical techniques used were Raman microscopy, optical microscopy and gas chromatography–mass spectrometry in order to determine the stratigraphy of the artworks, to identify the pigments used and to determine the type of protective varnishes applied. Along with commonly used pigments in Egyptian artefacts such as orpiment (As2S3), vermilion (HgS), red lead (Pb3O4), white lead (2PbCO3·Pb(OH)2) and lamp black (C), the pigment indigo (C16H10N2O2) has been detected for the first time in Egyptian panel paintings. Gypsum (CaSO4·2H2O) was used as a white ground layer and the protective varnish applied is found to be Pinaceae resin.
Source:Vibrational Spectroscopy, Volume 62
M. Abdel-Ghani, B. Stern, H.G.M. Edwards, R. Janaway
Two Coptic icons were studied, these date from the 18th century and were painted by IbrahimAl-Nasekh and are currently to be found in Saint Mercurius Church, Saint Mercurius Monastery in Old Cairo, Egypt. The analytical techniques used were Raman microscopy, optical microscopy and gas chromatography–mass spectrometry in order to determine the stratigraphy of the artworks, to identify the pigments used and to determine the type of protective varnishes applied. Along with commonly used pigments in Egyptian artefacts such as orpiment (As2S3), vermilion (HgS), red lead (Pb3O4), white lead (2PbCO3·Pb(OH)2) and lamp black (C), the pigment indigo (C16H10N2O2) has been detected for the first time in Egyptian panel paintings. Gypsum (CaSO4·2H2O) was used as a white ground layer and the protective varnish applied is found to be Pinaceae resin.
Raman spectroscopic study of the effects of dissolved NaCl on water structure
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Qiang Sun
Raman spectroscopy was utilized to investigate the effects of dissolved NaCl on water structure. For aqueous NaCl solutions, the difference spectra indicate a clear isosbestic point at 3345cm−1 and a weak isosbestic point around 3625cm−1. According to our explanation on Raman OH stretching band of water, it can be inferred that the addition of NaCl primarily breaks the tetrahedral hydrogen bonding and promotes formation of the donor hydrogen bonding in water, and slightly lowers the amount of free OH bonds. This is different from the effects of pressure and temperature on water structure. For liquid water, a water molecule interacts with neighboring water molecules through various local hydrogen bonded networks. Additionally, the enthalpy change of hydrogen bonding in water can be determined to be 11.35kJ/mol.
Source:Vibrational Spectroscopy, Volume 62
Qiang Sun
Raman spectroscopy was utilized to investigate the effects of dissolved NaCl on water structure. For aqueous NaCl solutions, the difference spectra indicate a clear isosbestic point at 3345cm−1 and a weak isosbestic point around 3625cm−1. According to our explanation on Raman OH stretching band of water, it can be inferred that the addition of NaCl primarily breaks the tetrahedral hydrogen bonding and promotes formation of the donor hydrogen bonding in water, and slightly lowers the amount of free OH bonds. This is different from the effects of pressure and temperature on water structure. For liquid water, a water molecule interacts with neighboring water molecules through various local hydrogen bonded networks. Additionally, the enthalpy change of hydrogen bonding in water can be determined to be 11.35kJ/mol.
SE(R)RS excitation profile of free-base 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin on immobilized gold nanoparticles
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Natália Hajduková-Šmídová, Marek Procházka, Minoru Osada
Surface-enhanced (resonance) Raman scattering – SE(R)RS – excitation profile (dependence of SE(R)RS intensity on excitation wavelength) is a key point for optimizing of electromagnetic enhancement of particular SE(R)RS system. In this paper, we measured SE(R)RS excitation profile of free-base 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin (TMPyP) on immobilized Au nanoparticles using confocal Raman microspectrometer with six excitation wavelengths (457.9, 488.0, 514.5, 530.9, 568.2 and 647.1nm). Au colloidal nanoparticles were immobilized to a glass slide via a self-assembled monolayer of 3-aminopropyltrimethoxysilane. SE(R)RS excitation profile is correlated with the corresponding surface plasmon extinction (SPE) spectrum of immobilized Au nanoparticles although the maximum of SE(R)RS intensity is slightly shifted from maximum of SPE. In our case of resonant molecule, SE(R)RS enhancement is coupled with molecular resonance enhancement and SE(R)RS excitation profile for particular vibrational mode depends on its TMPyP molecular resonance contribution. SE(R)RS excitation profile shows that maximal SE(R)RS intensity is obtained for 568.2nm excitation that provides limit of detection (LOD) of TMPyP 2×10−8 M in soaking solution.
Source:Vibrational Spectroscopy, Volume 62
Natália Hajduková-Šmídová, Marek Procházka, Minoru Osada
Surface-enhanced (resonance) Raman scattering – SE(R)RS – excitation profile (dependence of SE(R)RS intensity on excitation wavelength) is a key point for optimizing of electromagnetic enhancement of particular SE(R)RS system. In this paper, we measured SE(R)RS excitation profile of free-base 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin (TMPyP) on immobilized Au nanoparticles using confocal Raman microspectrometer with six excitation wavelengths (457.9, 488.0, 514.5, 530.9, 568.2 and 647.1nm). Au colloidal nanoparticles were immobilized to a glass slide via a self-assembled monolayer of 3-aminopropyltrimethoxysilane. SE(R)RS excitation profile is correlated with the corresponding surface plasmon extinction (SPE) spectrum of immobilized Au nanoparticles although the maximum of SE(R)RS intensity is slightly shifted from maximum of SPE. In our case of resonant molecule, SE(R)RS enhancement is coupled with molecular resonance enhancement and SE(R)RS excitation profile for particular vibrational mode depends on its TMPyP molecular resonance contribution. SE(R)RS excitation profile shows that maximal SE(R)RS intensity is obtained for 568.2nm excitation that provides limit of detection (LOD) of TMPyP 2×10−8 M in soaking solution.
Thermal, dielectric and vibrational properties of allylammonium chloroantimonates(III) and chlorobismuthates(III): [C3H5NH3]3[BiCl6] and [C3H5NH3]3[SbCl5]Cl
30 August 2012,
08:51:52
Publication year:
2012
Source:Vibrational Spectroscopy, Volume 62
Iwona Płowaś, Grażyna Bator, Ryszard Jakubas, Jan Baran
The allylammonium hexachlorobismuthate(III), [C3H5NH3]3[BiCl6], and the allylammonium pentachloroantimonate(III), [C3H5NH3]3[SbCl5]Cl, compounds have been synthesized and studied by means of differential scanning calorimetry, thermal expansion, dielectric and infrared (IR) techniques. [C3H5NH3]3[BiCl6] exhibits three solid–solid structural phase transitions (PTs) at: 304/304K (I↔II) (upon cooling/heating), 195/197K (II↔III) and 155/156K (III↔IV). In turn [C3H5NH3]3[SbCl5]Cl exhibits two PTs at: 221/221K (I↔II) and 181/185K (II↔III). The dielectric studies have been made in the frequency range of 2kHz–1MHz between 100 and 350K. The dielectric relaxation processes are observed in both crystals. The activation energy (E A) value of the dielectric relaxation process for [C3H5NH3]3[BiCl6] amounts to about 43 and 72kJmol−1 for the low- and high-temperature relaxation, respectively, whereas for [C3H5NH3]3[SbCl5]Cl E A =15kJmol−1. The infrared spectra of [C3H5NH3]3[BiCl6] and [C3H5NH3]3[SbCl5]Cl have been recorded over the wavenumber range between 3800 and 40cm−1 at selected temperatures (10–310K). The mechanisms of PTs in the title compounds are discussed.
Source:Vibrational Spectroscopy, Volume 62
Iwona Płowaś, Grażyna Bator, Ryszard Jakubas, Jan Baran
The allylammonium hexachlorobismuthate(III), [C3H5NH3]3[BiCl6], and the allylammonium pentachloroantimonate(III), [C3H5NH3]3[SbCl5]Cl, compounds have been synthesized and studied by means of differential scanning calorimetry, thermal expansion, dielectric and infrared (IR) techniques. [C3H5NH3]3[BiCl6] exhibits three solid–solid structural phase transitions (PTs) at: 304/304K (I↔II) (upon cooling/heating), 195/197K (II↔III) and 155/156K (III↔IV). In turn [C3H5NH3]3[SbCl5]Cl exhibits two PTs at: 221/221K (I↔II) and 181/185K (II↔III). The dielectric studies have been made in the frequency range of 2kHz–1MHz between 100 and 350K. The dielectric relaxation processes are observed in both crystals. The activation energy (E A) value of the dielectric relaxation process for [C3H5NH3]3[BiCl6] amounts to about 43 and 72kJmol−1 for the low- and high-temperature relaxation, respectively, whereas for [C3H5NH3]3[SbCl5]Cl E A =15kJmol−1. The infrared spectra of [C3H5NH3]3[BiCl6] and [C3H5NH3]3[SbCl5]Cl have been recorded over the wavenumber range between 3800 and 40cm−1 at selected temperatures (10–310K). The mechanisms of PTs in the title compounds are discussed.
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