A study of cysteamine ionization in solution by Raman spectroscopy and theoretical modeling

Different cysteamine (H2N-CH2-CH2-SH) ionization forms have been studied by polarized Raman spectroscopy in solutions prepared with H2O and D2O and by DFT calculations at the B3LYP/6-31++G(d,p) level. To account for solvation effects, we employed the integral equation formalism polarizable continuum model (IEFPCM) option and explicit water molecules. Calculated relative energies and Raman spectra revealed that gauche rotamers around the C-C bond are the most stable conformers in solution. The experimental pKa values and Raman spectra of various ionization forms were best predicted by using a model with three explicit water molecules and the IEFPCM option. In general, the use of IEFPCM tends to lower the calculated frequencies for a few bands, but in some cases (S-H stretching mode) this effect is expressed very strongly. Potential energy distribution (PED) analysis of gauche conformers of various cysteamine ionization forms provided the possibility of discriminating spectroscopically methylene groups adjacent to sulfur, (CH2)S, and nitrogen, (CH2)N, sites. In general, stretching and scissoring modes as well as wagging and twisting vibrations of the (CH2)N group were found to be at higher frequencies. The influence of ionization of SH and NH2 groups on the vibrational spectrum is discussed, and Raman markers for further amine group ionization studies are suggested.     

A highly regular hexapod structure of lead sulfide: solution synthesis and Raman spectroscopy

A highly regular hexapod-like structure of PbS with six symmetric arms has been synthesized by a simple and mild chemical solution route. The hexapod-like PbS structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). The results show that each arm is perpendicular to the other four, and opposite to the last one. The arms are about 0.3-0.6 microm long, which have about 40-60 nm tips and 150-200 nm base. And the arm shows an icicle-like structure and some clear steps, and grows along 100 directions. The most possible growth mechanism discussed herein is based on the characterization results. The Raman spectra of the hexapod-like PbS structure were investigated. The results show that our products are sensitive to the laser and can be photodegraded easily.     

Photoelectron emission spectroscopy of inorganic cations in aqueous solution

Threshold energies (6.1 <E_t ? 8.6 eV) are determined for photoelectron emission by 16 inorganic cations in aqueous solution E_t values are correlated with gas-phase ionization potentials, solvation and reorganization free energies, standard reduction potentials and ligand field stabilization energies (five transition metals). Dielectric saturation is shown to drastically lower threshold energies.     

Photoelectron emission spectroscopy of inorganic anions in aqueous solution

Threshold energies E_t are determined for photoelectron emission by 20 inorganic anions in aqueous solution (7.1 < E_t < 9.1 eV). Calculated values of E_t for Cl^?, Br^?, I^? agree with experiment. The E_t are correlated with charge-transf absorption spectra.     

Performance monitoring of a mammalian cell based bioprocess using Raman spectroscopy

Being able to predict the final product yield at all stages in long-running, industrial, mammalian cell culture processes is vital for both operational efficiency, process consistency, and the implementation of quality by design (QbD) practices. Here we used Raman spectroscopy to monitor (in terms of glycoprotein yield prediction) a fed-batch fermentation from start to finish. Raman data were collected from 12 different time points in a Chinese hamster ovary (CHO) based manufacturing process and across 37 separate production runs. The samples comprised of clarified bioprocess broths extracted from the CHO cell based process with varying amounts of fresh and spent cell culture media. Competitive adaptive reweighted sampling (CoAdReS) and ant colony optimization (ACO) variable selection methods were used to enhance the predictive ability of the chemometric models by removing unnecessary spectral information. Using CoAdReS accurate prediction models (relative error of predictions between 2.1% and 3.3%) were built for the final glycoprotein yield at every stage of the bioprocess from small scale up to the final 5000 L bioreactor. This result reinforces our previous studies which indicate that media quality is one of the most significant factors determining the efficiency of industrial CHO-cell processes. This Raman based approach could thus be used to manage production in terms of selecting which small scale batches are progressed to large-scale manufacture, thus improving process efficiency significantly.     

A modified glow-discharge source for emission spectroscopy

A glow-discharge emission source of the type described by Grimm for spectrochemical analysis has been modified to incorporate a secondary discharge of     

Raman spectroscopy of p-hydroxybenzoic acid aqueous solution and surface-unenhanced Raman scattering on silver colloid with ultraviolet excitation

A high-quality Raman spectrum of p-hydroxybenzoic acid (PHBA) aqueous solution (10(-2) M) under ultraviolet (UV) excitation at 325 nm was obtained, which could not be observed with visible and near infrared (NIR) excitations due to the low concentration in aqueous solution. However, the surface-unenhanced Raman scattering of PHBA in silver colloid excited by ultraviolet was unexpectedly observed, which was quite different from the cases excited with NIR and visible light, by which the SERS effect was very remarkable. This indicated that the SERS of the PHBA-silver colloid system showed selectivity to excitation wavelength. The enhancement mechanisms at different excitation wavelength regions are discussed.     

Surface-enhanced Raman spectrometry for detection in liquid chromatography using a windowless flow cell

A windowless flow cell has been developed for surface-enhanced Raman (SER) detection in liquid chromatography. Using colloidal silver as an active substrate, SER spectrometry of banned drugs in sport is presented. The experimental factors of primary influence on the analytical performance of the cell have been studied. The results of SER detection with the proposed cell have been compared to UV detection.     

Polymer-capped fiber-optic Raman probe for non-invasive Raman spectroscopy

Advances in fiber optic probe design are moving Raman spectroscopy into the clinic, although there remain important practical problems. While much effort has been devoted to minimizing Raman and fluorescence background from fibers, less attention has been given to the need to generate reference Raman signals that can correct for variations in tissue albedo, which is important in quantifying changes in tissue composition. To address this shortcoming, we have developed a fiber optic probe that incorporates a fluorinated ethylene-propylene copolymer (FEP) cap at the end of each excitation fiber. Transmission of laser light through the transparent cap generates a 732 cm(-1) Raman band whose intensity scales linearly with the laser power delivered to the tissue of interest. In our first design, the FEP cap functions as a waveguide with only a small insertion loss (~5%). Laser transmission through 1 mm of the polymer is sufficient to generate a usable reference Raman signal. We show the application of the probe to quantitative non-invasive Raman spectroscopy of animal tissues using rat leg phantoms as models. Ex-vivo Raman spectroscopy of excised rat tibia supports the use of the probe for spectroscopy of various tissues. These results provide proof of principle that the Raman probe can be used in multiple spectroscopic applications.     

Microwaves spark emission spectroscopy for the analysis of cations:A simple form of atomic emission spectroscopy

A novel method for the cation analysis was investigated.The analysis is based on the sparking of the salts of metals in a microwave oven after placing in a graphite cell.The graphite cell absorbs microwaves and produces high temperature which converts the salt into light emitting species.The colour of light was found to dependent on the nature of cation,however,the intensity of the emitted light was found to be depending upon the form and shape of the graphite assembly in addition to the concentration of the salt.This communication presents explanation for all these observations and for the systematic and quantitative analysis using microwave spark emission technique.     

Effect of pressure on rotational isomers in solution: infrared and Raman spectroscopy

The effect of pressure on the conformational equilibria between rotational isomers in solution has been studied by the infrared and Raman spectroscopy. The experimental volume changes for the transformation are explained theoretically by the three effects contributing to these volume changes, namely the overlap of the atoms with the internal rotation angle, the change of local packing of the solute and solvent, and the change of the electrostatic interaction with the solvent. The purpose of this paper is to review what is known about the volume changes for small molecules with internal rotation angles.     

Assessment of an osteoblast-like cell line as a model for human primary osteoblasts using Raman spectroscopy

Raman spectroscopy is employed to determine the suitability of the U20S osteoblast-like cell line for use as a model for human primary osteoblasts, with emphasis on the ability of these cell types to replicate their tissue of origin. It was found that both cell types demonstrated early stage mineral deposition that followed significantly different growth patterns. Analysis of the growth pattern and spectral data from primary cells revealed increasing bone quality ratios and a high crystallinity, consistent with previous reports. Conversely the investigation of the U20S osteoblast-like cell line provided evidence of dense multilayered mineralised regions that corresponded more closely to native bone in terms of its crystallinity and bone quality ratios. This finding contradicts previous reports on U20S osteoblast-like cells which have consistently described them as non-osteoinductive when cultured in various conditions on a number of substrates. This work demonstrates the successful application of Raman spectroscopy combined with biological and multivariate analysis for the investigation of osteoblast-like U20S cells and human primary osteoblasts, specifically with focus on the osteoinductive ability of the osteoblast-like cell line and the comparative differences in relation to the primary osteoblasts.     

High-temperature Raman spectroscopy of solid oxide fuel cell materials and processes

Chemical and material processes occurring in high temperature environments are difficult to quantify due to a lack of experimental methods that can probe directly the species present. In this letter, Raman spectroscopy is shown to be capable of identifying in-situ and noninvasively changes in material properties as well as the formation and disappearance of molecular species on surfaces at temperatures of 715 degrees C. The material, yttria-stabilized zirconia or YSZ, and the molecular species, Ni/NiO and nanocrystalline graphite, factor prominently in the chemistry of solid oxide fuel cells (SOFCs). Experiments demonstrate the ability of Raman spectroscopy to follow reversible oxidation/reduction kinetics of Ni/NiO as well as the rate of carbon disappearance when graphite, formed in-situ, is exposed to a weakly oxidizing atmosphere. In addition, the Raman active phonon mode of YSZ shows a temperature dependent shift that correlates closely with the expansion of the lattice parameter, thus providing a convenient internal diagnostic for identifying thermal gradients in high temperature systems. These findings provide direct insight into processes likely to occur in operational SOFCs and motivate the use of in-situ Raman spectroscopy to follow chemical processes in these high-temperature, electrochemically active environments.     

Micromachined impedance spectroscopy flow cytometer for cell analysis and particle sizing

A new cytological tool, based on the microCoulter particle counter (microCPC) principle, aimed at diagnostic applications for cell counting and separation in haematology, oncology or toxicology is described. The device measures the spectral impedance of individual cells or particles and allows screening rates over 100 samples s(-1) on a single-cell basis. This analyzer is intended to drive a sorting actuator producing a subsequent cell separation. Size reduction and integration of functions are essential in achieving precise measurements and high throughput. 3D finite element simulations are presented to compare various electrode geometries and their influence on cell parameters estimation. The device is based on a glass-polyimide microfluidic chip with integrated channels and electrodes microfabricated at the length scale of the particles to be investigated (1-20 microm). A laminar liquid flow carries the suspended particles through the measurement area. Each particle's impedance signal is recorded by a differential pair of microelectrodes using the cell surrounding media as a reference. The micromachined chip and processing electronic circuit allow simultaneous impedance measurements at multiple frequencies, ranging from 100 kHz to 15 MHz. In this paper, we describe the microfabrication and characterisation of an on-chip flow-cytometer as the first building block of a complete cell-sorting device. We then discuss the signal conditioning technique and finally impedance measurements of cells and particles of different sizes and types to demonstrate the differentiation of subpopulations in a mixed sample.     

A Rheumatoid arthritis study using Raman spectroscopy

Rheumatoid arthritis (RA) is characterized by chronic inflammation of the joints and can lead to a progressive destruction of articular cartilage and bone. In this study, the specificity and sensitivity of the RA diagnostic methods based on the receiver-operating characteristic curves for monitoring C-reactive protein (CRP) and rheumatoid factor (RF) were compared with the Raman spectroscopic diagnostic method developed in this work. Sera from 24 patients with rheumatoid arthritis and from 16 healthy individuals were analyzed to assess the biochemical composition and presence of inflammatory activity by the aforementioned methods. By comparing with the clinical results for specificity and sensitivity from the RF and CRP tests, we show that the overall results from the newly developed Raman method were significantly better, with a specificity of 96%, a sensitivity of 88%, and correctly identifying 92% of the RA and healthy individuals, while the RF test gave a specificity of 100% and a sensitivity of 54%, and the CRP test gave a specificity of 87% and a sensitivity of 58%, respectively.     

Simultaneous Raman and infrared spectroscopy: a novel combination for studying bacterial infections at the single cell level

Sepsis is a life-threatening clinical condition responsible for approximately 11 million deaths worldwide. Rapid and accurate identification of pathogenic bacteria and its antimicrobial susceptibility play a critical role in reducing the morbidity and mortality rates related to sepsis. Raman and infrared spectroscopies have great potential to be used as diagnostic tools for rapid and culture-free detection of bacterial infections. Despite numerous reports using both methods to analyse bacterial samples, there is to date no study collecting both Raman and infrared signatures from clinical samples simultaneously due to instrument incompatibilities. Here, we report for the first time the use of an emerging technology that provides infrared signatures via optical photothermal infrared (O-PTIR) spectroscopy and Raman spectra simultaneously. We use this approach to analyse 12 bacterial clinical isolates including six isolates of Gram-negative and six Gram-positive bacteria commonly associated with bloodstream infection in humans. To benchmark the single cell spectra obtained by O-PTIR spectroscopy, infrared signatures were also collected from bulk samples via both FTIR and O-PTIR spectroscopies. Our findings showed significant similarity and high reproducibility in the infrared signatures obtained by all three approaches, including similar discrimination patterns when subjected to clustering algorithms. Principal component analysis (PCA) showed that O-PTIR and Raman data acquired simultaneously from bulk bacterial isolates displayed different clustering patterns due to the ability of both methods to probe metabolites produced by bacteria. By contrast, signatures of microbial pigments were identified in Raman spectra, providing complementary and orthogonal information compared to infrared, which may be advantageous as it has been demonstrated that certain pigments play an important role in bacterial virulence. We found that infrared spectroscopy showed higher sensitivity than Raman for the analysis of individual cells. Despite the different patterns obtained by using Raman and infrared spectral data as input for clustering algorithms, our findings showed high data reproducibility in both approaches as the biological replicates from each bacterial strain clustered together. Overall, we show that Raman and infrared spectroscopy offer both advantages and disadvantages and, therefore, having both techniques combined in one single technology is a powerful tool with promising applications in clinical microbiology.

O-PTIR was used for simultaneous collection of infrared and Raman spectra from clinical pathogens associated with bloodstream infections.     

Raman and surface Raman spectroscopy with ultraviolet excitation

We record the accurate and reliable Raman spectra of benzoic acid (BA), p-nitrobenzoic acid (PNBA) and o-nitrobenzoic (ONBA) in aqueous solution with ultraviolet excitation. And we find that the ultraviolet (UV) Raman spectrum of aqueous BA solution has one-to-one correspondence to that of BA solid whereas the others are less resemble to the solid counterparts. We also report surface Raman spectroscopy of them in silver colloid without any enhancement in UV region and call it surface-unenhanced Raman spectroscopy (SUERS) while the surface-enhanced Raman scattering (SERS) effects are perfect in near infrared or visible regions. It demonstrates the SERS effects are strongly dependent on the excitation wavelength. On the basis of the experiments, we discuss the mechanism of SERS excited in different regions.     

Raman spectroscopy for the analysis of biomolecules

Spurred on by technological advances, Raman spectroscopy is becoming an important tool in the analysis of biological materials. It can provide unique information on composition and molecular structure. For biological chromophores resonance Raman effectively transforms absorption spectroscopy into a high information technique.