bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Imaging of Live Cancer Cells in the Natural Aqueous Environment
Authors: Kuimova Marina K. , Chan K. L. Andrew , Kazarian Sergei G.
Published: October 2009

Chemical imaging with Fourier transform infrared (FT-IR) spectroscopy allows the visualization of the distribution of chemical components in cells without the need for labels or added dyes. However, obtaining such images of living cells is difficult because of the strong absorption of water in the mid-infrared region. We report the use of attenuated total reflection (ATR) FT-IR spectroscopic imaging to study live human cancer cells in an aqueous environment, on a single cell level. Two complementary approaches have been used, providing flexibility with field of view and spatial resolution: (1) micro-ATR FT-IR imaging using a microscope objective with a Ge crystal, and (2) single-reflection diamond ATR-FT-IR imaging. Using both approaches, the ATR-FT-IR spectroscopic signatures allow the differentiation between several cellular organelles, e.g., the nucleus and the endoplasmic reticulum (ER). The overall cell shape can be defined by the distribution of the amide II band in the measured image, while the DNA-rich nucleus and glycogen-rich ER could be imaged using the spectral bands at 1084 cm−1 and 1023 cm−1, respectively. We also demonstrate the potential of ATR-FT-IR spectroscopic imaging for unraveling the details of the dynamics of biological processes, which are not accessible from cell ensemble studies, with high molecular specificity and satisfactory spatial resolution.
Tuning the Surface-Enhanced Raman Scattering Effect to Different Molecular Groups by Switching the Silver Colloid Solution pH
Authors: Kazanci Murat , Schulte Jean Pascal , Douglas Colin , Fratzl Peter , Pink David , Smith-Palmer Truis
Published: October 2009

Silver colloids were produced for surface-enhanced Raman scattering (SERS) experiments using hydroxylamine hydrochloride as the reduction agent. The roles of hydroxylamine hydrochloride and bulk solution pH values in the formation of functional groups on the surface of silver colloids and in determining the dimensions of silver colloids were examined using Raman, Fourier transform infrared (FT-IR) and ultraviolet–visible (UV-Vis) spectroscopy, atomic force microscopy (AFM), and zeta-size measurements. The spectrum of hydroxylamine hydrochloride reduced silver colloids was compared with the spectrum of sodium borohydride reduced colloids. The effect of colloid solution pH on SERS results was demonstrated using analyte molecules with biological significance, such as ribonucleic acid, egg albumin, L-α-phosphatidylcholine, and glucose. In general, it was shown that at high pH values the SERS effect was more pronounced due to the surface functional groups and colloid dimensions, and sharp, high spectral intensity values were obtained. At low pH values, protonation and rapid aggregation of colloids occurred and the surface chemistry was different. Depending on the analyte, bands were shifted, broadened, and/or the enhancement effect was reduced. Using Pseudomonas aeruginosa PAO1 and Streptococcus mutans it was also shown that by changing the solution bulk pH value, it was possible to enhance the response from different molecular groups in the bacteria and obtain different spectra from the same bacteria strain and the process was reversible. It was concluded that it is possible to produce site- or molecule-specific metal colloids and to tune the SERS effect to certain functional groups of analytes by means of the pH of colloidal suspension.
Digital Filtering and Model Updating Methods for Improving the Robustness of Near-Infrared Multivariate Calibrations
Authors: Kramer Kirsten E. , Small Gary W.
Published: October 2009

Fourier transform near-infrared (NIR) transmission spectra are used for quantitative analysis of glucose for 17 sets of prediction data sampled as much as six months outside the timeframe of the corresponding calibration data. Aqueous samples containing physiological levels of glucose in a matrix of bovine serum albumin and triacetin are used to simulate clinical samples such as blood plasma. Background spectra of a single analyte-free matrix sample acquired during the instrumental warm-up period on the prediction day are used for calibration updating and for determining the optimal frequency response of a preprocessing infinite impulse response time-domain digital filter. By tuning the filter and the calibration model to the specific instrumental response associated with the prediction day, the calibration model is given enhanced ability to operate over time. This methodology is demonstrated in conjunction with partial least squares calibration models built with a spectral range of 4700–4300 cm−1. By using a subset of the background spectra to evaluate the prediction performance of the updated model, projections can be made regarding the success of subsequent glucose predictions. If a threshold standard error of prediction (SEP) of 1.5 mM is used to establish successful model performance with the glucose samples, the corresponding threshold for the SEP of the background spectra is found to be 1.3 mM. For calibration updating in conjunction with digital filtering, SEP values of all 17 prediction sets collected over 3–178 days displaced from the calibration data are below 1.5 mM. In addition, the diagnostic based on the background spectra correctly assesses the prediction performance in 16 of the 17 cases.
Influence of Instrumental Parameters on the Kinetic Energy of Ions and Plasma Temperature for a Hexapole Collision/Reaction-Cell-Based Inductively Coupled Plasma Quadrupole Mass Spectrometer
Authors: Favre Georges , Brennetot René , Chartier Frédéric , Tortajada Jeanine
Published: October 2009

Inductively coupled plasma mass spectrometry (ICP-MS) is widely used in inorganic analytical chemistry for element and/or isotope ratio measurements. The presence of interferences, which is one of the main limitations of this method, has been addressed in recent years with the introduction of collision/reaction cell devices on ICP-MS apparatus. The study of ion–molecule reactions in the gas phase then became of great importance for the development of new analytical strategies. Knowing the kinetic energy and the electronic states of the ions prior to their entrance into the cell, i.e., just before they react, thereby constitutes crucial information for the interpretation of the observed reactivities. Such studies on an ICP-MS commonly used for routine analyses require the determination of the influence of different instrumental parameters on the energy of the ions and on the plasma temperature from where ions are sampled. The kinetic energy of ions prior to their entrance into the cell has been connected to the voltage applied to the hexapole according to a linear relationship determined from measurements of ion energy losses due to collisions with neutral gas molecules. The effects of the plasma forward power, sampling depth, and the addition of a torch shield to the ICP source were then examined. A decrease of the plasma potential due to the torch shielding, already mentioned in the literature, has been quantified in this study at about 3 V.
Systematic Method for the Kinetic Modeling of Temporally Resolved Hyperspectral Microscope Images of Fluorescently Labeled Cells
Authors: Cutler Patrick J. , Haaland David M. , Gemperline Paul J.
Published: October 2009

In this paper we report the application of a novel method for fitting kinetic models to temporally resolved hyperspectral images of fluorescently labeled cells to mathematically resolve pure-component spatial images, pure-component spectra, and pure-component reaction profiles. The method is demonstrated on one simulated image and two experimental cell images, including human embryonic kidney cells (HEK 293) and human A549 pulmonary type II epithelial cells. In both cell images, inhibitor kappa B kinase alpha (IKKα) and mitochondrial antiviral signaling protein (MAVS) were labeled with green and yellow fluorescent protein, respectively. Kinetic modeling was performed on the compressed images by using a separable least squares method. A combination of several first-order decays were needed to adequately model the photo-bleaching processes for each fluorophore observed in these images, consistent with the hypothesis that each fluorophore was found in several different environments within the cells. Numerous plausible mechanisms for kinetic modeling of the photo-bleaching processes in these images were tested and a method for selecting the most parsimonious and statistically sufficient model was used to prepare spatial maps of each fluorophore.
Improved Algorithm for Quantitative Analyses of Infrared Spectra of Multicomponent Gas Mixtures with Unknown Compositions
Authors: Gianella Michele , Sigrist Markus W.
Published: October 2009

We present a major improvement of an algorithm based on a spectral library search for the quantitative analysis of multicomponent gas samples with unknown compositions. A quantitative spectral database of infrared spectra is used as a training set to compute regression coefficients. Concentrations are computed in the principal component space via principal component regression (PCR). In addition to previous algorithms, we introduce a rating for each candidate substance depending on the concentration found with PCR and a filter that removes candidates that are predicted with negative concentrations if their rating is below a certain threshold. Negative concentrations arise when the measured spectrum contains components that are not contained in the database. The PCR is recomputed until all candidates have a rating above the threshold. Then an adaptive filter “subtracts” the substance with the highest rating from both the measured spectrum and the library and appends it to a hit list. The iteration of this procedure directly produces a list of substances in order of descending importance (i.e., contribution to the measured absorbance) with their corresponding concentrations. The algorithm is tested on spectra of multicomponent surgical smoke samples. The four main components (water, methane, ethane, and ethene) are identified correctly (within the top 5 of the hit list) for an appropriate choice of the rating threshold. The algorithm describes the composition of the smoke sample correctly despite the presence of features in the spectrum that cannot be explained by the spectrum of any single substance present in the database.
Hyperspectral Confocal Fluorescence Imaging: Exploring Alternative Multivariate Curve Resolution Approaches
Authors: Haaland David M. , Jones Howland D. T. , Van Benthem Mark H. , Sinclair Michael B. , Melgaard David K. , Stork Christopher L. , Pedroso Maria C. , Liu Ping , Brasier Allan R. , Andrews Nicholas L. , Lidke Diane S.
Published: October 2009

Hyperspectral confocal fluorescence microscopy, when combined with multivariate curve resolution (MCR), provides a powerful new tool for improved quantitative imaging of multi-fluorophore samples. Generally, fully non-negatively constrained models are used in the constrained alternating least squares MCR analyses of hyperspectral images since real emission components are expected to have non-negative pure emission spectra and concentrations. However, in this paper, we demonstrate four separate cases in which partially constrained models are preferred over the fully constrained MCR models. These partially constrained MCR models can sometimes be preferred when system artifacts are present in the data or where small perturbations of the major emission components are present due to environmental effects or small geometric changes in the fluorescing species. Here we demonstrate that in the cases of hyperspectral images obtained from multicomponent spherical beads, autofluorescence from fixed lung epithelial cells, fluorescence of quantum dots in aqueous solutions, and images of mercurochrome-stained endosperm portions of a wild-type corn seed, these alternative, partially constrained MCR analyses provide improved interpretability of the MCR solutions. Often the system artifacts or environmental effects are more readily described as first and/or second derivatives of the main emission components in these alternative MCR solutions since they indicate spectral shifts and/or spectral broadening or narrowing of the emission bands, respectively. Thus, this paper serves to demonstrate the need to test alternative partially constrained models when analyzing hyperspectral images with MCR methods.
Third-Harmonic Generation and Multi-Photon Excitation Fluorescence Imaging Microscopy Techniques for Online Art Conservation Diagnosis
Authors: Gualda Emilio J. , Filippidis George , Melessanaki Kristalia , Fotakis Costas
Published: October 2009

We present an appropriate methodology and results for using third-harmonic generation (THG) modality for nondestructive high resolution imaging measurements of varnished structures in model painted artifacts. Detection takes place in the reflection mode, demonstrating the ability of the technique to be applied to the evaluation of original artworks. Furthermore, multi-photon excitation fluorescence images were obtained, providing complementary information related to the identification of the chemical composition of the artifacts.
Near-Infrared Spectroscopy as a Useful Tool for Analysis in Solution in Common Organic Solvents
Authors: Iwamoto Reikichi
Published: October 2009

In the present paper we report that near-infrared spectroscopy is a useful tool for analyzing solutes in solution in common organic solvents. This is because the near-infrared absorptions of the solvent are not so strong as to disturb the separation of the characteristic near-infrared bands, by subtraction, of the solute. To demonstrate this capability, we first showed that the near-infrared absorptions of heptane and toluene, each of which represents aliphatic or aromatic solvents, do not significantly affect the noise level of the difference spectrum, in which the near-infrared spectrum of a solute is to be separated by subtraction. Second, we showed that the characteristic near-infrared absorptions of 1-heptene as a solute were well separated from the spectrum of the solution in heptane and toluene. Four of the five indicator bands of 1-heptene were recognizable and sufficiently detected at the almost limiting concentration of 0.1% (v/v) in both solvents. The minimum magnitude of the detectable signal is discussed in terms of the signal-to-noise ratios of the indicator bands. As an application, we investigated the interaction properties of a *CH group of 1-heptyne from the CH stretching fundamental, combination, and overtone bands in the pure liquid and in solution in three solvents at various concentrations.
A New Method for Performing Polarization Modulation Infrared Reflection-Adsorption Spectroscopy of Surfaces
Authors: Schennach Robert , Hirschmugl Carol , Gilli Eduard , Tysoe Wilfred T.
Published: October 2009

A new and relatively simple polarization modulation technique is presented and tested that enables the whole spectral range to be detected between 400 and 4000 cm−1. This experiment is conventionally carried out using a photoelastic modulator that modulates incident plane polarized light through 90°. This suffers from the drawback that it enables spectra to be collected only over a relatively narrow spectral range. As an alternative, a polarizer is placed in the beam and oriented at 45° to the sample normal. This produces incident radiation fluxes with identical intensities for both s- and p-polarized light. A second polarizer is then modulated through 90° and the surface spectrum is then extracted in the usual manner from the difference between these signals, normalized to their sum. The method is demonstrated for a self-assembled monolayer of 11-mercapto-undecanoicacid (11-MUA) on gold on mica, and it is shown that, while the resulting spectra are extremely sensitive to optical alignment, the method yields spectra that are in excellent agreement with published data.
Collisional Quenching of Erythrosine B as a Potential Reference Dye for Impulse Response Function Evaluation
Authors: Szabelski Mariusz , Ilijev Douglas , Sarkar Pabak , Luchowski Rafal , Gryczynski Zygmunt , Kapusta Peter , Erdmann Rainer , Gryczynski Ignacy
Published: October 2009

We studied the collisional quenching of the erythrosine B fluorophore by potassium iodide. The quenching follows a Stern–Volmer dependence up to the highest quencher concentration. The lifetime of erythrosine B decreases to 24 ps in 5.02 M of potassium iodide. The quantum yield of erythrosine B in the presence of 5.02 M KI is 0.0035. The relatively high brightness makes this compound attractive as an ultrashort reference in time-resolved measurements. In both frequency- and time-domain fluorescence techniques, there is a need for lifetime standards with extremely short decay times. Mimicking the instantaneous scattering at longer wavelengths allows color-effect-free measurements in the emission region. Another motivation is the problem of obtaining the impulse response function in the case of two-photon excitation. Time-resolved microscopy also benefits from fast-decaying dyes because the impulse response function can be evaluated at the emission wavelength of the investigated specimen without changing filters. We demonstrated that impulse response functions for commonly used detectors are practically the same for scattering as for quenched erythrosine B emission. We also analyzed a complex fluorescence decay using both elastic scattering and quenched erythrosine B emission as a response function.
Novel Micro-Cavity Substrates for Improving the Raman Signal from Submicrometer Size Materials
Authors: Misra Anupam K. , Sharma Shiv K. , Kamemoto Lori , Zinin Pavel V. , Yu Qigui , Hu Ningjie , Melnick Levi
Published: October 2009

A novel and simple method for improving the detection limit of conventional Raman spectra using a micro-Raman system and picoliter volumes is presented. A micro-cavity in a reflecting metal substrate uses various mechanisms that collectively improve the entire Raman spectrum from the sample. A micro-cavity with a radius of several micrometers acts as a very effective device that provides multiple excitation of the sample with the laser and couples the forward-scattered Raman photons toward the collection optics in the back-scattered Raman geometry. One of the important features of the micro-cavity substrate is that it enhances the entire Raman spectrum of the molecules under investigation and maintains the relative intensity ratios of the various Raman bands. This feature of maintaining the overall integrity of the Raman features during signal enhancement makes the micro-cavity substrate ideal for forensic science applications for chemical detection of residual traces and other applications requiring low sample concentrations. The spectra measured in these cavities are also observed to be highly reproducible and reliable. A simple method for fabricating micro-cavity substrates with precise sizes and shapes is described. It is further shown that micro-cavities coated with nanofilms of gold take advantage of both surface-enhanced Raman scattering (SERS) and micro-cavity methods and also significantly improve sample detection limits.
Transcutaneous Raman Spectroscopy of Murine Bone In Vivo
Authors: Schulmerich Matthew V. , Cole Jacqueline H. , Kreider Jaclynn M. , Esmonde-White Francis , Dooley Kathryn A. , Goldstein Steven A. , Morris Michael D.
Published: October 2009

Raman spectroscopy can provide valuable information about bone tissue composition in studies of bone development, biomechanics, and health. In order to study the Raman spectra of bone in vivo, instrumentation that enhances the recovery of subsurface spectra must be developed and validated. Five fiber-optic probe configurations were considered for transcutaneous bone Raman spectroscopy of small animals. Measurements were obtained from the tibia of sacrificed mice, and the bone Raman signal was recovered for each probe configuration. The configuration with the optimal combination of bone signal intensity, signal variance, and power distribution was then evaluated under in vivo conditions. Multiple in vivo transcutaneous measurements were obtained from the left tibia of 32 anesthetized mice. After collecting the transcutaneous Raman signal, exposed bone measurements were collected and used as a validation reference. Multivariate analysis was used to recover bone spectra from transcutaneous measurements. To assess the validity of the transcutaneous bone measurements cross-correlations were calculated between standardized spectra from the recovered bone signal and the exposed bone measurements. Additionally, the carbonate-to-phosphate height ratios of the recovered bone signals were compared to the reference exposed bone measurements. The mean cross-correlation coefficient between the recovered and exposed measurements was 0.96, and the carbonate-to-phosphate ratios did not differ significantly between the two sets of spectra ( p > 0.05). During these first systematic in vivo Raman measurements, we discovered that probe alignment and animal coat color influenced the results and thus should be considered in future probe and study designs. Nevertheless, our noninvasive Raman spectroscopic probe accurately assessed bone tissue composition through the skin in live mice.
Modified Local Straight-Line Screening to Detect Synthetic Drugs in Adulterated Herbal Medicines
Authors: Xueyi Zhu , Zhonghu Zhang , Feng Lu , Yutian Wu , Yunpeng Qi
Published: October 2009

A local straight-line screening (LSLS) algorithm was recently designed as a method to detect synthetic drug(s) in adulterated herbal medicines based on infrared spectroscopy. Some modifications are made in this paper to improve the existing LSLS algorithm, including interpolation, second derivation, and change of calculation regions from 3 to 7 data points. These modifications have decreased the effect of unpredicted noises and baseline shift on infrared spectroscopy, resulting in outstanding detailed spectral characteristics of the suspected synthetic drugs. The algorithm has been tested using five kinds of synthetic drugs (sibutramine, fenfluramine, lovastatin, sildenafil, and methyldopa) in 40 herbal medicine samples. The concentration of the synthetic drug(s) predicted by the modified LSLS algorithm is closer to those determined by high-performance liquid chromatography. Consequently, the correct results rise from 30 obtained using the original LSLS to 36 obtained using the modified LSLS in 40 samples, the false negative responses drop from 5 to 1, and the false positive responses drop from 5 to 3. The results obtained using the M-LSLS algorithm based on the sibutramine spectrum collected at different times and on different instruments also vary within acceptable ranges. These allow the method to be more appropriate for the preliminary screening of herbal medicines suspected of adulteration with synthetic drugs, with high rapidity, accuracy, and cost effectiveness.
Dual-Laser-Beam-Induced Breakdown Spectroscopy of Copper Using Simultaneous Continuous Wave CO2 and Q-Switched Nd:YAG Lasers
Authors: Shoursheini S. Z. , Parvin P. , Sajad B. , Bassam M. A.
Published: October 2009

In this work, we investigate the enhancement of Cu emission lines of a micro-plasma induced by a Nd:YAG laser due to the thermal effect of simultaneous irradiation by a continuous wave (CW) CO2 laser. The enhancement of the emission lines was achieved at a higher temperature with minimal distortion of the target when the focal point of the Nd:YAG laser was located approximately 1 mm away from the sample surface.
Raman Study of CeO2 Texture as a Buffer Layer in the CeO2/La2Zr2O7/Ni Architecture for Coated Conductors
Authors: Jiménez C. , Caroff T. , Bartasyte A. , Margueron S. , Abrutis A. , Chaix-Pluchery O. , Weiss F.
Published: October 2009

The CeO2/La2Zr2O7/Ni piled-up structure is a very promising architecture for YBa2Cu3O7 (YBCO) coated conductors. We have grown YBCO/CeO2/LZO/Ni epitaxial structures by metalorganic decomposition (MOD) and metalorganic chemical vapor deposition (MOCVD) methods. The crystallographic quality of the CeO2 layer is not well determined by conventional X-ray diffraction (XRD) due to the superposition of LZO and CeO2 reflections. An alternative simple Raman spectroscopy analysis of the crystalline quality of the CeO2 films is proposed. The F2g Raman mode of CeO2 can be quantified either by using two polarization configurations (crossed or parallel) or at two different rotation angles around the normal axis (0° and 45°) to obtain information about the sample texture. The sample texture can be determined via a quality factor (referred to as the Raman intensity ratio, RIR) consisting of calculating the ratio of the integrated intensity of the CeO2 F2g mode at 0° and 45° in parallel polarization. This factor correlates with superconducting performance and the technique can be used as an on-line nondestructive characterization method.
Measuring the Micro-Polarity and Hydrogen-Bond Donor/Acceptor Ability of Thermoresponsive N-Isopropylacrylamide/N-tert-Butylacrylamide Copolymer Films Using Solvatochromic Indicators
Authors: Szczupak Boguslaw , Ryder Alan G. , Togashi Denisio M. , Rochev Yuri A. , Gorelov Alexander V. , Glynn Thomas J.
Published: October 2009

Thin polymer films are important in many areas of biomaterials research, biomedical devices, and biological sensors. The accurate in situ measurement of multiple physicochemical properties of thin polymer films is critical in understanding biocompatibility, polymer function, and performance. In this work we demonstrate a facile spectroscopic methodology for accurately measuring the micro-polarity and hydrogen-bond donor/acceptor ability for a series of relatively hydrophilic thermoresponsive copolymers. The micro-polarity of the N-isopropylacrylamide (NIPAM) and N-tert-butylacrylamide (NtBA) co-polymers was evaluated by means of the ET(30), α, β, and π* empirical solvatochromic polarity parameters. The data shows that increasing the NtBA fraction in the dry copolymer film reduces polarity and hydrogen-bonding ability. Within the Kamlet–Taft polarity framework, the NIPAM/NtBA copolymer films are strong hydrogen-bond acceptors, strongly dipolar/polarizable, and rather moderate hydrogen-bond donors. This characterization provides a more comprehensive physicochemical description of polymers, which aids the interpretation of film performance. Comparison of the measured ET(30) values with literature data for other water-soluble polymers show that dry NIPAM/NtBA copolymers are slightly more polar than poly(ethylene oxide), less polar than polyvinyl-alcohol, and approximately the same polarity as poly( N-vinyl-2-pyrrolidone). These findings indicate that this spectroscopic method is a facile, rapid, and nondestructive methodology for measuring polymer properties in situ, suitable for most biomaterials research laboratories.
Automated Detection of Fingerprint Traces of High Explosives Using Ultraviolet Raman Spectroscopy
Authors: Jander Peter , Noll Reinhard
Published: October 2009

Ultraviolet (UV) resonance Raman spectroscopy is a promising technique for the detection of trace explosives. For real-world applications, it is necessary to develop data evaluation algorithms that automatically recognize the spectral features of explosives in a sample spectrum. We have developed a robust algorithm that can tolerate high levels of fluorescence background. We successfully demonstrated the detection of traces of ANFO and TNT explosives at surface coverage levels of 55 μg/cm2 in a blind test experiment. The sensitivity and selectivity is discussed in terms of receiver operating characteristics (ROC) curves.
Mid-Infrared and Near-Infrared Spectral Properties of Mycorrhizal and Non-Mycorrhizal Root Cultures
Authors: Calderón Francisco J. , Acosta-Martinez Veronica , Douds David D. , Reeves James B. , Vigil Merle F.
Published: October 2009

We investigated the Fourier-transformed mid-infrared (MIR) and near-infrared (NIR) spectroscopic properties of mycorrhizal (M) and non-mycorrhizal (NM) carrot roots with the goal of finding infrared markers for colonization by arbuscular mycorrhizal (AM) fungi. The roots were cultured with or without the AM fungus Glomus intraradices under laboratory conditions. A total of 50 M and NM samples were produced after pooling subsamples. The roots were dried, ground, and scanned separately for the NIR and MIR analyses. The root samples were analyzed for fatty acid composition in order to confirm mycorrhizal infection and to determine the presence of fatty acid markers. Besides the roots, fatty acid standards, pure cultures of saprophytic fungi, and chitin were also scanned in order to identify spectral bands likely to be found in M samples. Principal components analysis (PCA) was used to illustrate spectral differences between the M and NM root samples. The NIR analysis achieved good resolution with the raw spectral data and no pretreatment was needed to obtain good resolution in the PCA analysis of the NIR data. Standard normal variate and detrending pretreatment improved the resolution between M and NM in the MIR range. The PCA loadings and/or the spectral subtraction of selected samples showed that M roots are characterized by absorbances at or close to 400 cm−1, 1100–1170 cm−1, 1690 cm−1, 2928 cm−1, and 5032 cm−1. The NM samples had characteristic absorbances at or near 1734 cm−1, 3500 cm−1, 4000 cm−1, 4389 cm−1, and 4730 cm−1. Some of the bands that differentiate M from NM roots are prominent in the spectra of pure fungal cultures, chitin, and fatty acids. Our results show that mycorrhizal and nonmycorrhizal root tissues can be differentiated via MIR and NIR spectra with the advantage that the same samples can then be used for other analyses.
Multiple Perturbation Two-Dimensional Correlation Analysis of Cellulose by Attenuated Total Reflection Infrared Spectroscopy
Authors: Shinzawa Hideyuki , Morita Shin-Ich , Awa Kimie , Okada Mariko , Noda Isao , Ozaki Yukihiro , Sato Hidetoshi
Published: October 2009

An extension of the two-dimensional (2D) correlation analysis scheme for multi-dimensional perturbation is described. A simple computational form is provided to construct synchronous correlation and disrelation maps for the analysis of microscopic imaging data based on two independent perturbation variables. Sets of time-dependent attenuated total reflection infrared (ATR-IR) spectra of water and cellulose mixtures were collected during the evaporation of water from finely ground cellulose. The system exhibits complex behaviors in response to two independent perturbations, i.e., evaporation time and grinding time. Multiple perturbation 2D analysis reveals a specific difference in the rate of evaporation of water molecules when accompanied by crystallinity changes of cellulose. It identifies subtle differences in the volatility of water, which is related to the crystalline structure of cellulose.
A Novel Wire Mesh “Cell” for Studying Lipid Oxidative Processes by Fourier Transform Infrared Spectroscopy
Authors: García-González Diego L. , Van De Voort Frederik R.
Published: October 2009

A novel infrared (IR) sample handling accessory has been developed to monitor and study oxidation processes of edible oils under moderate temperature conditions by Fourier transform infrared (FT-IR) spectroscopy. A reusable stainless steel mesh IR “cell” was designed and evaluated from the standpoint of mesh size, transmission characteristics, its ability to entrap oil, and techniques to apply sample and normalize path length so as to obtain good quality, reproducible spectra. The concept is to entrap oil within the mesh by means of its inherent surface tension and to take advantage of the high surface area provided by the mesh to facilitate rapid oxidation of the oil by air at ambient or slightly elevated temperatures without having to resort to more extreme temperature conditions to track oxidative changes in real time. Changes taking place in canola oil at room temperature, in the dark and exposed to light, as well as at 50 °C are presented to illustrate the performance of the cell in monitoring oxidative changes in real time (e.g., formation of hydroperoxides, loss of cis and formation of trans double bonds). The mesh cell should be useful for comparing the relative performance of antioxidants as well as evaluating the oxidative stability of oils, among other applications.
Dual Function Surface-Enhanced Raman Active Extractor for the Detection of Environmental Contaminants
Authors: Bhandari Deepak , Walworth Matthew J. , Sepaniak Michael J.
Published: October 2009

Surface-enhanced Raman spectroscopy (SERS) has lagged behind other analytical techniques utilized in routine chemical analyses despite the information-rich spectra produced. This can be attributed in part to the difficulties in finding effective substrates that provide high sensitivity and highly reproducible SERS responses. Herein, we have developed a silver-coated polypropylene filter (AgPPF) as a highly sensitive and promising SERS substrate for the detection of environmentally significant chemicals, including selected pharmaceuticals, personal care products, and possible endocrine disruptors. The present approach involves preconcentration studies of selected environmental compounds with 3M's High Performance Extraction Disc Cartridges (HPEDCs) and characterization of the same HPEDC filters as a SERS substrate. The polypropylene microfiber prefilter that encloses the empore extraction medium is modified by physical vapor deposition with silver and used as the SERS substrate. The HPEDC itself is used to concentrate analytes into a desired concentration range, achieving maximum sensitivity. Surface roughness and nanoscale structure of silver films on the microfiber were characterized by atomic force microscopy (AFM). The mass thickness of the silver and volume were optimized for the highest SERS signal using rhodamine 6G as a model compound. A novel component of our HPEDC studies involves the hyphenation of the concentration protocol and SERS. The hyphenation of sample concentration and SERS allows more sensitive surface-enhanced detection. Mitoxanthrone dihydrochloride, crystal violet dye, 4-aminobenzoic acid, and rhodamine 6G were employed to study the sensitive SERS detection and were observed as low as 5 × 10−8 M to 1 × 10−10 M without any preconcentration step. Additionally, SERS signatures of some flavonoids, targeted as possible Endocrine Disrupting Chemicals by the US Environmental Protection Agency, such as Apigenin and Daidzein, are reported along with their sensitive detection down to ng/mL for the first time with preconcentration.
Control of Out-of-Focus Light Intensity in Confocal Raman Microscopy Using Optical Preprocessing
Authors: Pelletier Michael J.
Published: October 2009

Optical preprocessing, the manipulation of imaging-forming light prior to detection, is used in many forms of microscopy to enhance image information and interpretation. The rejection of out-of-focus light by a pinhole in confocal microscopy is an example of optical preprocessing, where spatial filtering is carried out in a plane conjugate to the object focal plane. The rejection efficiency afforded by this arrangement is, however, sometimes insufficient. Insufficient rejection of out-of-focus light intensity can lead to incorrect interpretations of confocal Raman depth and line maps. An alternative approach is to reject out-of-focus light by implementing spatial filtering in one of the several planes conjugate to the pupil plane. This paper shows that mapping enhanced by structured pupils (MESP) provides substantial additional rejection of out-of-focus intensity relative to traditional confocal microscopy, yielding a potential solution to the problem of misleading Raman maps. In addition, lossless MESP is proposed, wherein simple phase masks simultaneously direct in-focus and out-of-focus light intensity transmitted by confocal optics to different regions of a charge-coupled device (CCD) detector.
Principal Component Analysis Based Interconversion between Infrared and Near-Infrared Spectra for the Study of Thermal-Induced Weak Interaction Changes of Poly(N-Isopropylacrylamide)
Authors: Zhang Liping , Noda Isao , Wu Yuqing
Published: October 2009

The use of a novel spectral interconversion scheme, principal component analysis (PCA) based spectral prediction, to probe weak molecular interactions of a polymer film is reported. A PCA model is built based on a joint data matrix by concatenating two related spectral data matrices (such as infrared (IR) and near-infrared (NIR) spectra) along the variable direction, then the obtained loading matrix of the model is split into two parts to predict the desired spectra. For a better PCA-based prediction, it is suggested that the samples whose spectra are to be predicted should be as similar as possible to those used in the model. Based on the PCA model, the thermal-induced changes in the weak interaction of poly( N-isopropylacrylamide) (PNiPA) film is revealed by the interconversion between selected spectral ranges measured between 40 and 220 °C. The thermal-induced weak interaction changes of PNiPA, expressed as either the band shift or intensity changes at a specific region, have been probed properly. Meanwhile, the robustness of the spectral prediction is also compared with that achieved by a partial least squares (PLS2) model in detail, illustrating its advantages in predicting more subtle structural changes such as C–H groups.
Design Considerations for Near-Infrared Filter Photometry: Effects of Noise Sources and Selectivity
Authors: Tarumi Toshiyasu , Amerov Airat K. , Arnold Mark A. , Small Gary W.
Published: October 2009

Optimal filter design of two-channel near-infrared filter photometers is investigated for simulated two-component systems consisting of an analyte and a spectrally overlapping interferent. The degree of overlap between the analyte and interferent bands is varied over three levels. The optimal design is obtained for three cases: a source or background flicker noise limited case, a shot noise limited case, and a detector noise limited case. Conventional photometers consist of narrow-band optical filters with their bands located at discrete wavelengths. However, the use of broadband optical filters with overlapping responses has been proposed to obtain as much signal as possible from a weak and broad analyte band typical of near-infrared absorptions. One question regarding the use of broadband optical filters with overlapping responses is the selectivity achieved by such filters. The selectivity of two-channel photometers is evaluated on the basis of the angle between the analyte and interferent vectors in the space spanned by the relative change recorded for each of the two detector channels. This study shows that for the shot noise limited or detector noise limited cases, the slight decrease in selectivity with the use of broadband optical filters can be compensated by the higher signal-to-noise ratio afforded by the use of such filters. For the source noise limited case, the best quantitative results are obtained with the use of narrow-band non-overlapping optical filters.
Raman Spectroscopic Investigation of Peptide—Glycosaminoglycan Interactions
Authors: Ishwar Arjun R. , Jeong Kyung Jae , Panitch Alyssa , Akkus Ozan
Published: October 2009

Protein–glycosaminoglycan (GAG) interactions play a central role in tissue engineering and drug delivery. A rapid and efficacious method for screening these interactions is essential. Raman spectroscopy was used to identify chemical interactions and conformational changes occurring upon binding between a synthetic peptide (QRRFMQYSARRF) and two glycosaminoglycans (GAGs), heparin and chondroitin 6-sulfate (C6S). The results identify three main chemical groups that are involved in the binding of the synthetic peptide with heparin and C6S. Tyrosine formed hydrogen bonds with the GAGs via its hydroxyl group. The amide I band demonstrated substantial shifts in Raman wavenumbers when bound to heparin and C6S (Δω = —10.2 ± 0.7 cm−1 and Δω = —11.9 ± 0.3 cm−1, respectively), suggesting that the peptide underwent planar conformational changes after binding occurred. Upon binding to the peptide, the sulfate peak of heparin displayed a substantially greater shift in the Raman wavenumber (—7.5 ± 0.5 cm−1) than that of C6S (—2.6 ± 0.5 cm−1). The greater amide I and sulfate band shifts seen during peptide–heparin interactions are indicative of a stronger association compared to that between the peptide and C6S. This observation was confirmed by capillary electrophoresis, which demonstrated a lower dissociation constant ( KD) between the peptide and heparin ( KD of 19.2 ± 3.3 μM) than between the peptide and C6S (26.7 ± 2.5 μM). We conclude that the shift in the Raman wavenumbers of amide I and sulfate groups can be used for high-throughput screening of interaction affinities between libraries of peptides and GAGs.
Studying the Effect of pH Variation on the Incorporation of the Antipsychotic Drug Clozapine into Dyed and Non-Dyed Hair Samples Using Micro-Attenuated Total Reflection Spectroscopy
Authors: Koçak A. , Blanchard Z. S. , Hoffman D. B.
Published: October 2009

Antipsychotic drugs are among the mostly widely used medications and are usually taken for prolonged periods of time. Due to its accumulation and trapping of drugs, hair can provide a useful indication of long-term exposure. Of interest also is what if any changes in the structural components of hair occur as a result of the drug binding process. Micro-attenuated total reflection (ATR) spectroscopy is able to examine the structural changes of hair samples by the application of sufficient pressure and without microtoming the hair (A. Koçak and S. L. Berets, Appl. Spectrosc. 62, 803 (2008)). In this investigation, we examined changes resulting from exposure of dyed and undyed hair to external clozapine as a function of the pH of the exposing solution. Single samples from different individuals and in one case from different regions of the scalp from the same individual were analyzed. The results demonstrated that pH related differences exist between drug-exposed dyed and non-dyed samples.
Determination of the Absorption and Scattering Coefficients of Pigments: Application to the Identification of the Components of Pigment Mixtures
Authors: Latour Gaël , Elias Mady , Frigerio Jean-Marc
Published: October 2009

In most scattering media, the scattering centers have random shapes and sizes, preventing any theoretical approach for the determination of their absorption and scattering coefficients. Three different experimental protocols are here selected and briefly described. The obtained values are compared and then validated from a comparison with the most rigorous method. The Kubelka–Munk method, using a paint layer applied to both white and black backgrounds, is chosen to build a database of these coefficients for reference pigments. Using this database, the identification of the components of a pigment mixture using spectral measurements is realized and validated.
Light Tolerance of R-Phycoerythrin and a Tandem Conjugate Observed by Single Molecule Recrossing Events
Authors: Burrows Sean M. , Patel Payal , Pappas Dimitri
Published: October 2009

The recrossing of single molecules in a probe volume was used to investigate light harvesting and energy transfer between R-phycoerythrin (R-PE) and a tandem conjugate dye. The normalized recrossing ratio, Nr/Nt, was defined as the number of molecules that reenter the probe volume (Nr) to the total number of molecules detected (Nt). The energy transfer process in phycobiliproteins was studied as a function of excitation irradiation and irradiation time. This was achieved by investigating the average baseline-subtracted fluorescence intensity, normalized molecular recrossing ratio (Nr/Nt), and the number of molecules detected per second. The photon saturation irradiance of the R-PE and the tandem conjugate were compared with each other, showing that energy transfer to the tandem dye significantly improves photostability and light tolerance of the phycobiliprotein. The Nr/Nt ratio was used to study the photophysical properties of R-phycoerythrin and the tandem conjugate Streptavidin R-Phycoerythrin-AlexaFluor-647 (PE-647). Normalized molecular recrossings showed that energy transfer to a tandem conjugate could reduce the formation of triplet states in R-phycoerythrin and extend the light tolerance of certain phycobiliproteins.
Predicting Raman Spectra Using Density Functional Theory
Authors: Fairchild Steven Z. , Bradshaw Charles F. , Su Wansheng , Guharay Samar K.
Published: October 2009

Accurately computing molecular Raman spectra would enable rapid development of inexpensive and extensive Raman libraries. This is especially beneficial for chemicals that are regulated, toxic, or otherwise difficult to handle. Numerous quantum mechanical methods have been developed that enable computation of Raman spectra. Here, we study the B3LYP exchange correlation functional with various combinations of basis sets, polarization functions, and diffuse functions to determine which combination best computes the Raman spectra for explosive and nonexplosive molecules. In comparing spectra, three metrics were utilized: the root mean square error, the earth mover's distance, and the weighted cross-correlation average. The earth mover's distance and weighted cross-correlation metrics are shown to have significantly greater power at detecting spectral similarities and differences than the root mean square error. Across all methods and molecules examined, B3LYP/6-311++G(d,p) was found to provide the best match between measured and computed Raman spectra. Spectra generated at the B3LYP/6-311++G(d,p) level were found to be accurate enough to correctly identify each molecule out of a set of measured molecular spectra.
Simultaneous Neutron Scattering and Raman Scattering
Authors: Adams Mark A. , Parker Stewart F. , Fernandez-Alonso Felix , Cutler David J. , Hodges Christopher , King Andrew
Published: October 2009

The capability to make simultaneous neutron and Raman scattering measurements at temperatures between 1.5 and 450 K has been developed. The samples to be investigated are attached to one end of a custom-made center-stick suitable for insertion into a 100 mm-bore cryostat. The other end of the center-stick is fiber-optically coupled to a Renishawt® inVia Raman spectrometer incorporating a 300 mW Topticat® 785 nm wavelength stabilized diode laser. The final path for the laser beam is ∼1.3 m in vacuo within the center-stick followed by a focusing lens close to the sample. Raman scattering measurements with a resolution of 1 to 4 cm−1 can be made over a wide range (100–3200 cm−1) at the same time as a variety of different types of neutron scattering measurements. In this work we highlight the use of inelastic neutron scattering and neutron diffraction in conjunction with the Raman for studies of the globular protein lysozyme.