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ABSTRACT: Highly sensitive Raman gas spectroscopy is introduced for simultaneous real time analysis of O(2), CO(2), CH(4), and N(2) in order to elucidate the dynamics of greenhouse gases evolving from climate-sensitive ecosystems. The concentrations and fluxes of this suite of biogenic gases were quantified in the head space of a water-saturated, raised peat bog ecotron. The intact peat bog, exhibiting various degradation stages of peat and sphagnum moss, was exposed to various light regimes in order to determine important ecosystem parameters such as the maximum photosynthesis rate of the sphagnum as well as the extent of soil and plant respiration. Miniaturized Raman gas spectroscopy was proven to be an extremely versatile analytical technique that allows for onsite multigas analysis in high temporal resolution. Therefore it is an urgently needed tool for elucidation of complex biochemical processes especially in climate-sensitive ecosystems and consequently for the estimation of climate-relevant gas budgets.
Analytical Chemistry 01/2013; · 5.86 Impact Factor
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Anna Rusznyák,
Denise M Akob,
Sándor Nietzsche,
Karin Eusterhues,
Kai Uwe Totsche,
Thomas R Neu, Torsten Frosch,
Jürgen Popp,
Robert Keiner,
Jörn Geletneky,
Lutz Katzschmann,
Ernst-Detlef Schulze,
Kirsten Küsel
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ABSTRACT: Karstic caves represent one of the most important subterranean carbon storages on Earth and provide windows into the subsurface. The recent discovery of the Herrenberg Cave, Germany, gave us the opportunity to investigate the diversity and potential role of bacteria in carbonate mineral formation. Calcite was the only mineral observed by Raman spectroscopy to precipitate as stalactites from seepage water. Bacterial cells were found on the surface and interior of stalactites by confocal laser scanning microscopy. Proteobacteria dominated the microbial communities inhabiting stalactites, representing more than 70% of total 16S rRNA gene clones. Proteobacteria formed 22 to 34% of the detected communities in fluvial sediments, and a large fraction of these bacteria were also metabolically active. A total of 9 isolates, belonging to the genera Arthrobacter, Flavobacterium, Pseudomonas, Rhodococcus, Serratia, and Stenotrophomonas, grew on alkaline carbonate-precipitating medium. Two cultures with the most intense precipitate formation, Arthrobacter sulfonivorans and Rhodococcus globerulus, grew as aggregates, produced extracellular polymeric substances (EPS), and formed mixtures of calcite, vaterite, and monohydrocalcite. R. globerulus formed idiomorphous crystals with rhombohedral morphology, whereas A. sulfonivorans formed xenomorphous globular crystals, evidence for taxon-specific crystal morphologies. The results of this study highlighted the importance of combining various techniques in order to understand the geomicrobiology of karstic caves, but further studies are needed to determine whether the mineralogical biosignatures found in nutrient-rich media can also be found in oligotrophic caves.
Applied and environmental microbiology 12/2011; 78(4):1157-67. · 3.69 Impact Factor
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ABSTRACT: Resonance Raman spectroscopy was applied for investigating the malaria pigment hemozoin, which is an important target structure of antimalarial drugs. Morphology-sensitive low wavenumber modes of hemozoin were selectively enhanced with help of excitation wavelengths at lambda = 633 nm and lambda = 647 nm. The assignment of the most prominent bands in the Raman spectra at 343 cm(-1) and 368 cm(-1) was assisted by DFT calculations of the hemozoin dimer. The mode at 343 cm(-1) in the Raman spectrum of hemozoin is strongly enhanced with lambda(exc.) = 647 nm and is represented by a combined, symmetric doming mode of the two hematin units in the hemozoin dimer. The enhancement of this vibration is stronger in the resonance Raman spectrum of hemozoin compared with less crystalline beta-hematin. The selective resonance enhancement of the morphology-sensitive Raman modes of hemozoin is caused by absorption bands in the UV-VIS-NIR spectrum. This absorption spectrum of the crystalline malaria pigment hemozoin shows a strong band at 655 nm. Another broad absorption band at 870 nm is the reason for the strong relative resonance enhancement of the mode at 1372 cm(-1) in the Raman spectrum of crystalline hemozoin with lambda(exc.) = 830 nm. In conclusion, resonance Raman micro-spectroscopy with lambda(exc.) = 647 nm was shown to have great potential as an analytical tool to probe the morphology of hematin samples.
The Analyst 07/2009; 134(6):1126-32. · 4.23 Impact Factor
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ABSTRACT: We report on the great advantages of using deep UV Raman system for in situ planetary applications. Among them are to be mentioned: (I) higher scattering efficiency compared to VIS-IR Raman excitation wavelengths, (II) electronic resonance effects which increase the intrinsically weak Raman signal thus improving the S/N ratio of the detected Raman signals and (III) spectral separation of Raman and fluorescence signals. All these advantages are making UV Raman a valuable technique for in situ planetary applications. Mineral as well as biological samples were analyzed using Raman deep UV excitation and the results are presented. For the mineral samples a comparison with excitation in the NIR-VIS spectral regions is made. The impact of fluorescence on Raman data acquisition at different laser excitation wavelengths is assessed. Making use of the resonance effects, spectra of microorganisms were recorded with a high S/N ratio, allowing afterwards a very precise identification and classification (to the strain level) of the measured samples.
Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 01/2008; 68(4):1029-35. · 2.10 Impact Factor
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ABSTRACT: Methods to probe the molecular structure of living cells are of paramount importance in understanding drug interactions and environmental influences in these complex dynamical systems. The coupling of an acoustic levitation device with a micro-Raman spectrometer provides a direct molecular probe of cellular chemistry in a containerless environment minimizing signal attenuation and eliminating the affects of adhesion to walls and interfaces. We show that the Raman acoustic levitation spectroscopic (RALS) approach can be used to monitor the heme dynamics of a levitated 5 microL suspension of red blood cells and to detect hemozoin in malaria infected cells. The spectra obtained have an excellent signal-to-noise ratio and demonstrate for the first time the utility of the technique as a diagnostic and monitoring tool for minute sample volumes of living animal cells.
Lab on a Chip 10/2007; 7(9):1125-31. · 5.67 Impact Factor
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ABSTRACT: Raman microspectroscopy was applied for an in situ localization of the malaria pigment hemozoin in Plasmodium falciparum-infected erythrocytes. The Raman spectra (lambdaexc=633 nm) of hemozoin show very intense signals with a very good signal-to-noise ratio. These in situ Raman signals of hemozoin were compared to Raman spectra of extracted hemozoin, of the synthetic analogue beta-hematin, and of hematin and hemin. beta-Hematin was synthesized according to the acid-catalyzed dehydration of hematin and the anhydrous dehydrohalogenation of hemin which lead to good crystals with lengths of about 5-30 microm. The Raman spectra (lambdaexc=1064 nm) of hemozoin and beta-hematin show almost identical behaviors, while some low wavenumber modes might be used to distinguish between the morphology of differently synthesized beta-hematin samples. The intensity pattern of the resonance Raman spectra (lambdaexc=568 nm) of hemozoin and beta-hematin differ significantly from those of hematin and hemin. The most striking difference is an additional band at 1655 cm(-1) which was only observed in the spectra of hemozoin and beta-hematin and cannot be seen in the spectra of hematin and hemin. Raman spectra of the beta-hematin dimer were calculated ab initio (DFT) for the first time and used for an assignment of the experimentally derived Raman bands. The calculated atomic displacements provide valuable insight into the most important molecular vibrations of the hemozoin dimer. With help from these DFT calculations, it was possible to assign the Raman band at 1655 cm(-1) to a mode located at the propionic acid side chain, which links the hemozoin dimers to each other. The Raman band at 1568 cm(-1), which has been shown to be influenced by an attachment of the antimalarial drug chloroquine in an earlier study, could be assigned to a C=C stretching mode spread across one of the porphyrin rings and is therefore expected to be influenced by a pi-pi-stacking to the drug.
The Journal of Physical Chemistry B 10/2007; 111(37):11047-56. · 3.70 Impact Factor
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ABSTRACT: A new layout of a versatile Raman difference setup is presented. The new device combines the advantages of the rotating cell for exploitation of the resonance Raman enhancement and the high precision of Raman difference spectroscopy together with the multiplex advantages and very high quantum efficiency offered by a CCD detector. While Raman difference spectroscopy is the most accurate method for the detection of very small band shifts, the method requires the strict prevention of any environmental perturbation of one of the two spectra, which are used for the difference spectra calculation. The presented device satisfies this requirement by implementing a double-beam layout, where the simultaneously detected Raman signals of two sample cells are combined within a Y-fiber bundle and imaged together onto the CCD detector. The accuracy of the new apparatus in detecting frequency shifts and minor sample components is greatly increased compared to conventional Raman spectroscopy as shown by studying binary mixtures of CHCl3 and CCl4. Hereby it was possible to resolve a formerly undetected shift of <0.02 cm(-1) of the CCl4 band at 218 cm(-1). The new RDS setup has a very versatile design. The device can take advantage of the high sensitivity and selectivity of the resonance Raman enhancement applying excitation wavelengths from the UV to NIR and can be used for a variety of samples with only minor changes in the optical arrangement. The new device will be of utmost importance for a fast, gentle, sensitive, selective, and precise investigation of biomolecules and their interactions. Some first results are shown concerning the interaction of the antimalarial chloroquine with hematin in a hydrous environment.
Analytical Chemistry 09/2007; 79(16):6159-66. · 5.86 Impact Factor
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ABSTRACT: Deep UV resonance Raman micro-spectroscopy (lambda(exc) = 244 nm) was applied for a highly sensitive, selective, and gentle localization of the antimalarial quinine in situ in cinchona bark. The high potential of the method was demonstrated by the detection of small amounts of the alkaloid in the plant material without any further sample preparation, where conventional (non-resonant) Raman microscopy was unsuccessful due to a strong fluorescence background. The resonance Raman spectrum of cinchona bark corresponds well with that of quinine; it can be distinguished from its diastereomer quinidine via the mode at 831 cm(-1), which is shifted to 843 cm(-1) in the case of quinidine. This vibration involves a bending motion within the side chain around the chiral center of quinine. Vibrations belonging to the quinoline ring (important for its antimalarial activity in forming pi-pi-interactions to hemozoin) and the vinyl group are resonantly enhanced in the UV Raman spectra. A convincing mode assignment is derived by means of a combination of NIR Raman spectroscopy and DFT calculations. The Raman spectra of quinine in cinchona bark are modeled by considering a hydrous environment that causes a shift of the band at 1362 compared with 1371 cm(-1) in anhydrous quinine. This intense vibration is therefore sensitive to the presence of an aqueous environment and is assigned mostly to a stretching motion within the quinoline ring. The presented results nicely show the sensitivity of Raman spectroscopy to monitor subtle differences within the molecular structure and the influence of a biological relevant hydrous environment and trace low concentrated pharmaceutical relevant active agents in plant material.
The Journal of Physical Chemistry B 04/2007; 111(16):4171-7. · 3.70 Impact Factor
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ABSTRACT: The antimalarial agent mefloquine was investigated using Fourier transform near-infrared (FT NIR) Raman and FT IR spectroscopy. The IR and Raman spectra were calculated with the help of density functional theory (DFT) and a very good agreement with the experimental spectra was achieved. These DFT calculations were applied to unambiguously assign the prominent features in the experimental vibrational spectra. The calculation of the potential energy distribution (PED) and the atomic displacements provide further valuable insight into the molecular vibrations. The most prominent NIR Raman bands at 1,363 cm(-1) and 1,434 cm(-1) are due to C=C stretching (in the quinoline part of mefloquine) and CH(2) wagging vibrations, while the most intense IR peaks at 1,314 cm(-1); 1,147 cm(-1); and 1,109 cm(-1) mainly consist of ring breathings and deltaCH (quinoline); C-F stretchings; and asymmetric ring breathings, C-O stretching as well as CH(2) twisting/rockings located at the piperidine moiety. Since the active agent (mefloquine) is usually present in very low concentrations within the biological samples, UV resonance Raman spectra of physiological solutions of mefloquine were recorded. By employing the detailed non-resonant mode assignment it was also possible to unambiguously identify the resonantly enhanced modes at 1,619 cm(-1), 1,603 cm(-1) and 1,586 cm(-1) in the UV Raman spectra as high symmetric C=C stretching vibrations in the quinoline part of mefloquine. These spectroscopic results are important for the interpretation of upcoming in vitro and in vivo mefloquine target interaction experiments.
Analytical and Bioanalytical Chemistry 04/2007; 387(5):1749-57. · 3.78 Impact Factor
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ABSTRACT: UV resonance Raman spectroscopy was applied for a selective enhancement of molecular vibrations of the important antimalarial chloroquine under physiological conditions. The resonance Raman spectra of chloroquine at pH values resembling the pH value of blood and the pH value of the acid food vacuole of plasmodium can unambiguously be distinguished via Raman resonantly enhanced mode at 721 cm(-1). These vibrations are assigned to -(CH2)n- rocking mode of the chloroquine side chain and are expected to be influenced by protonation of chloroquine. Furthermore, vibrations belonging to the quinoline ring (important for pi-pi-interactions to hemozoin) are resonantly enhanced and can be studied selectively. A convincing mode assignment was performed by means of DFT calculations. These calculations proved that the different protonation states of chloroquine remarkably influence various vibrational modes, the molecular geometry, and molecular orbitals. The presented results are of significant relevance for a Raman spectroscopical localization of chloroquine inside the acid food vacuole of plasmodium, the study of pi-pi-interactions of chloroquine to the biological target molecules hematin and hemozoin and the protonation state of chloroquine during this docking process. The protonation of the weak base chloroquine is considered to be crucial for an accumulation inside the acid food vacuole of plasmodium and an object for resistances against this drug.
The Journal of Physical Chemistry B 03/2007; 111(7):1815-22. · 3.70 Impact Factor
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ABSTRACT: UV resonance Raman microspectroscopy was applied for a localization of the antiplasmodial naphthylisoquinoline alkaloid dioncophylline A in very low concentrations in different parts of the samples (e.g., in the roots) of the tropical liana Triphyophyllum peltatum. The application of resonance Raman microspectroscopy was characterized by a very high sensitivity and selectivity. It was possible to assign the resonance Raman spectra of dioncophylline A, dioncophylline C, and dioncopeltine A by means of a combination of NIR Raman spectroscopy and DFT calculations. The UV resonance Raman spectra of T. peltatum are very well resembled by the spectra of dioncophylline A, while they can be clearly distinguished from the spectra of dioncophylline C and dioncopeltine A. This distinction between the various naphthylisoquinolines was possible by the two modes at 1356 and 1613 cm-1. These two modes were assigned to C=C stretching and CH bending vibrations. The presented results of a highly sensitive and selective in situ localization of the active agent dioncophylline A in different parts of the plant material of T. peltatum are of high importance for the acquisition of new antimalarials and for plant science in general.
Analytical Chemistry 03/2007; 79(3):986-93. · 5.86 Impact Factor
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ABSTRACT: The great capabilities of UV Raman imaging have been demonstrated on the three Martian meteorites: Sayh al Uhaymir, Dar al Gani, and Zagami. Raman spectra without disturbing fluorescence and with high signal-to-noise-ratios and full of spectral features were derived. This result is of utmost importance for the development of powerful instruments for space missions. By point scanning the surfaces of the meteorite samples, it was possible for the first time to construct UV-Raman images out of the array of Raman spectra. Deep-UV Raman images are to the best of our knowledge presented for the first time. The images were used for a discussion of the chemical-mineralogical composition and texture of the meteorite surfaces. Comparative Raman studies applying visible and NIR Raman excitation wavelengths demonstrate a much better performance for UV Raman excitation. This comparative study of different Raman excitation wavelengths at the same sample spots was done by constructing a versatile, robust sample holder with a fixed micro-raster. The overall advantages of UV resonance Raman spectroscopy in terms of sensitivity and selectivity are demonstrated and discussed. Finally the application of this new technique for a UV Raman instrument for envisaged astrobiological focused space missions is suggested.
Analytical Chemistry 03/2007; 79(3):1101-8. · 5.86 Impact Factor
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ABSTRACT: Near infrared Fourier transform (NIR FT) micro Raman spectroscopy in combination with density functional theory (DFT) calculations has been applied for an in vivo localization of the antiplasmodial naphthylisoquinoline alkaloid dioncophylline A (1) in the tropical liana Triphyophyllum peltatum. Fluorescence microscopy images suggest finding this active agent in 10 mum big inclusions located in the cortex of the stem or the beginning of the leaves. By means of spatially resolved FT Raman micro spectroscopy, we could detect dioncophylline A (1) in these inclusions. FT Raman spectroscopy is an extremely selective tool capable of differentiating between various structurally similar naphthylisoquinoline alkaloids. With the help of DFT calculations, we succeeded in assigning the differences found in the FT Raman spectra of the various naphthylisoquinolines to nuC=C vibrations of the naphthyl ring. The presented results are of relevance for the investigation and extraction of new antimalarial active agents.
Biopolymers 08/2006; 82(4):295-300. · 2.87 Impact Factor
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ABSTRACT: The structure of the antimalarial drug halofantrine is analyzed by means of density functional theory (DFT) calculations, IR, and Raman spectroscopy. Strong, selective enhancements of the Raman bands of halofantrine at 1621 and 1590 cm(-1) are discovered by means of UV resonance Raman spectroscopy with excitation wavelength lambda(exc)=244 nm. These signal enhancements can be exploited for a localization of small concentrations of halofantrine in a biological environment. The Raman spectrum of halofantrine is calculated by means of DFT calculations [B3LYP/6-311+G(d,p)]. The calculation is very useful for a thorough mode assignment of the Raman bands of halofantrine. The strong bands at 1621 and 1590 cm(-1) in the UV Raman spectrum are assigned to combined C[Double Bond]C stretching vibrations in the phenanthrene ring of halofantrine. These bands are considered as putative marker bands for pipi interactions with the biological target molecules. The calculation of the electron density demonstrates a strong distribution across the phenanthrene ring of halofantrine, besides the electron withdrawing effect of the Cl and CF(3) substituents. This strong and even electron density distribution supports the hypothesis of pipi stacking as a possible mode of action of halofantrine. Complementary IR spectroscopy is performed for an investigation of vibrations of polar functional groups of the halofantrine molecule.
Journal of Biomedical Optics 15(4):041516. · 3.16 Impact Factor
