Publications

Abstract: Far- and mid-infrared photoacoustic (PA) spectra of tetracene, pentacene, perylene and pyrene were acquired in this study. Far-infrared data were obtained at wavenumbers down to ∼80 cm⁻¹ using largeamplitude phase modulation in a step-scan spectrometer; many previously unreported bands were observed in these spectra. For each compound, the fingerprint region of the mid-infrared spectrum (approximately 400–2000 cm⁻¹) contained a large number of bands correlated with vibrations that are predicted to be either infrared or Raman active. In addition, numerous combination and overtone bands appeared in the mid-infrared spectra. This PA investigation provides the most detailed spectral data known for these four aromatic compounds

Abstract: Crystallization is commonly used in the production of many products such as ice cream, butter and chocolates. Due to the practical limits of the equipment, crystallization in the industry occurs non-isothermally. Currently, there are a limited number of models which can characterize the crystallization behaviour under such conditions. Crystallization under non-isothermal cooling conditions was studied by using molecules with a stearic acid moiety. These stearic acid containing molecules were selected for their different dimensional crystal growths. 12-hydroxystearic acid (12HSA) was selected to represent one-dimensional crystal growth, stearic acid for twodimensional crystal growth and trihydroxystearin for three-dimensional crystal growth.

In study 1, the modified Avrami model was experimentally validated to model crystallization using non-isothermal cooling conditions. Four techniques were tested which included: small deformation rheology, differential scanning calorimetry, polarized light microscopy and Fourier transform infrared spectroscopy (FT-IR). The experimental validation of the model was done by accurately fitting the parameters of the modified Avrami model; such as induction time, maximal phase change and the Avrami exponent; to the data. FT-IR was the most accurate method because the data collected fitted well to the modified Avrami model. The Avrami exponent obtained from FT-IR was the only technique to be sensitive to both the mode of nucleation as well as the dimensionality of crystal growth. By using the modified Avrami model to characterize crystallization under non-isothermal cooling conditions, the apparent rate constant obtained from the model gave further insights to the kinetics of crystallization under these conditions.

Study 2 investigated the nature of crystallographic mismatches in 12HSA fibres which causes branching due to the imperfect incorporation of 12HSA molecules into the crystal lattice. FT-IR was used to monitor the changes during crystallization in the 1700 cm -1 and 3200 cm -1 peaks which corresponded to the dimerization of carboxylic acid monomers and the formation of non-specific hydrogen bonding, respectively. When FTIR data was fitted to the modified Avrami model, the rate constants obtained increased linearly with the cooling rate for hydrogen bonding while the dimerization of carboxylic iii acid monomers plateaued at cooling rates above 5 °C/min. Therefore at cooling rates above 5 °C/min, 12HSA does not effectively dimerize when incorporating into the crystal lattice which causes crystal imperfections leading to branching in 12HSA fibres.

In study 3, the activation energy for nucleation under non-isothermal cooling conditions was determined using a statistical method. The activation energies for stearic acid, 12HSA, trihydroxystearin and triglycerides were 1.52 kJ/mol, 5.40 kJ/mol (Rogers & Marangoni, 2009), 7.87 kJ/mol and 24.8 kJ/mol (Marangoni, Tang, & Singh, 2006); respectively. The activation energy for nucleation for a molecule is partially affected by its polarity relative to the solvent such that an increase in polarity would result in a decrease in activation energy. However, this was not always observed as the activation energy for stearic acid was less than that for 12HSA. Since the polarity of the molecule does not fully explain the activation energy, a specific interaction was used to account for the larger activation energy observed in 12HSA. The specific interaction describes how molecules are arranged in a nucleus and its ability to hide the polar groups away from the crystal-solvent interface. When the polar groups were not effectively hidden, an increase in the activation energy for nucleation was observed.

Abstract: Fungi are one of the serious causes of spoilage in stored grain including wheat. Aspergillus spp. is one of the most common storage fungi that spoils stored wheat. The damage caused by fungi adversely affects the quality of wheat and reduces its nutritional composition. Present methods of analysing chemical composition of wheat and other cereals using wet chemistry are destructive and use bulk grain and thus rely on bulk analysis. Grains, similar to other biological materials, are highly non-homogenous, hence, bulk analysis which causes damage to intrinsic structure of kernels, cannot be used for characterization of single kernels and studying the compositional distribution within a single kernel. In the present work, synchrotron based high resolution infrared imaging was used to study the compositional changes in stored wheat due to fungal damage. Clear differences between healthy and damaged wheat endosperm spectra were observed at peaks around 1740, 1595, and 1250 cm⁻¹. The difference in the absorption of infrared radiation was likely caused due to reduced lipid (1740 cm⁻¹), lignin (1595 cm−1) and cellulose (1250 cm⁻¹) content in damaged wheat endosperm.

Abstract: Synchrotron infrared radiation has been successfully coupled through an IR microscope to a thin-cavity external reflectance cell to study the diffusion controlled redox of a ferrocyanide solution. Excellent signal to noise was achieved even at aperture settings close to the diffraction limit. Comparisons of noise levels as a function of aperture size demonstrate that this can be attributed to the high brilliance of synchrotron radiation relative to a conventional thermal source. Time resolved spectroscopic studies of diffusion controlled redox behaviour have been measured and compared to purely electrochemical responses of the thin-cavity cell. Marked differences between the two measurements have been explained by analysing diffusion in both the axial (linear) and radial dimensions. Whereas both terms contribute to the measured current and charge, only species that originate in the volume element above the electrode and diffuse in the direction perpendicular to the electrode surface are interrogated by IR radiation. Implications for using ultramicroelectrodes and synchrotron IR (SIR) to study electrochemical processes in the sub millisecond time domain are discussed.

Abstract: A description of a coupled electrochemical and spectrometer interface using synchrotron infrared radiation is provided. The interface described allows for the precise and accurate timing needed for time-resolved IR spectroscopic studies of electrochemical systems. The overall interface uses a series of transistor-transistor logic trigger signals generated from the commercial FTIR spectrometer to regulate the recording of control, electrochemical, and IR signals with reproducible and adjustable timing. The instrument has been tested using a thin-layer electrochemical cell with synchrotron light focused through microscope optics. The time-resolved response of the benzoquinone/dihydroxybenzoquinone redox couple is illustrated as an example of the instrument’s capability.

Abstract: Over the years Fourier-Transform Infrared (FTIR) spectroscopy has been widely employed in the structural and functional characterization of biomolecules. The introduction of infrared (IR) microscopes and of synchrotron light sources has created expectations that FTIR could become a generally viable technique to study both structure and reactivity in vivo, inside single cells, by performing measurements that up to a few years ago were the preserve of in vitro experiments on purified macromolecules. In this review we present the state-of-the-art in the application of FTIR spectromicroscopy as a technique for the study of structure and dynamics in single cells, we discuss the performance requirements for this application and review developments in sample handling methods.

Abstract: The gelating abilities of enantiopure, racemic, and different enantio-enriched mixtures of 12-hydroxystearic acid (12HSA) have been compared in order to clarify conflicting reports in the literature (1) concerning their ability to gelate organic liquids. Less than 1.0 wt % of optically pure (D)-12HSA was found to gelate mineral oil. The gel matrix was comprised of high aspect ratio fibers in which the 12HSA molecules were organized as head-to-head dimers and the 12-hydroxyl groups formed an H-bonding network along the axis transverse to the longitudinal growth. Below 2 wt %, racemic 12HSA in mineral oil did not reach the percolation threshold. Its organogels were comprised of platelet-like crystals with a molecular arrangement of single, in-plane, hydrogen-bonded acyclic dimers that prevent longitudinal growth and limit the ability of the polar groups to phase separate during nucleation.

Abstract: The modified Avrami model was found to accurately predict the induction time, maximum phase volume and dimensionality of crystal growth for stearic acid containing molecules when the experimental method employed measures as a function of phase volume. Four methods were examined to validate the model including: Fourier transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), small deformation rheology and polarized light microscopy (PLM). PLM and FT-IR were able to detect the nucleation event prior to DSC and rheology. FT-IR and PLM provided the most accurate data due to the similarities between the experimental and fitted induction times (x0), maximal phase change (ymax) and the Avrami exponent (n). Further, the Avrami exponent, obtained from FT-IR, was sensitive to both the mode of nucleation and the dimensionality of crystal growth. Therefore, the apparent rate constants (kapp) obtained by FT-IR and PLM are useful in providing further insights into the kinetics of non-isothermal crystallization. The calculated apparent rate constants suggest a diffusion limited crystallization at slow cooling rates (i.e., below 5–7

Abstract: The possibility of performing FT-IR spectromicroscopy experiments on individual living cells is the focus of considerable attention. Among the applications of interest, the obtainment of structural information in rapid measurements, with a time resolution of the minute or better, is a prized goal. In this work, we show that the use of synchrotron FT-IR spectromicroscopy allows one to extract weak spectral changes, of less than 10–3 au per minute, in the absorption spectrum of single rod cells following photostimulation. We also show that absorption changes are accompanied by other optical effects due to changes in the real part of the refractive index of the cell. The use of two-dimensional correlation spectroscopy allows us to assign bands to specific molecular chromophores and to extract weak spectral variations in the presence of a noisy background.

Abstract: The liquid crystal morphologies of symmetrical diacy phosphatidylcholine liposomes examined in this research study were found to be dependent on saturated hydrocarbon chain length. Both powder x-ray diffraction and synchrotron mid-IR spectromicroscopy indicate that phosphatidylcholines with short hydrocarbon tails (i.e. ten and twelve carbons) are more likely to form unilamellar liposomes while those with long hydrocarbon tails (i.e. eighteen and twenty carbons) are more likely to form multilamellar liposomes. Hydrocarbon chain lengths of fourteen and sixteen represent a transitional zone between these two liquid crystal morphologies. The FTIR spectra where a shoulder develops on the peak at wavenumber 1750 cm−1 particularly highlights the change in the packing of adjacent molecules in the transitional zone

Abstract: Cholesterol and gamma-oryzanol co-crystallization occurs when equal ratios of the two compounds or excess gamma-oryzanol is present in the solution. Excess cholesterol produces macroscopic fibrillar crystals from the melt prior to the co-crystallization and formation of radial fine fibers under slow cooling conditions. The cholesterol fibrillar crystals then facilitate cholesterol-gamma-oryzanol co-crystallization producing fine fibers that nucleate from the surface of the cholesterol crystals. Equal ratios of cholesterol and gamma-oryzanol or excess gamma-oryzanol allow the radial fine fibers to nucleate from the melt without the need of an internal crystal template.

Abstract: Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24 eV to 48 eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5–0.8 nm for α-C:H and 0.35 nm for α-C:H:N films. When the ion energy was increased from 24 eV to 48 eV, the fraction of sp3 bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8 GPa to 12.5 GPa, and the Young's modulus increased from 100 GPa to 130 GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145 GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.

Abstract: Femoral bone degeneration has been recognized as an important cause of lameness in broiler chickens for many years, but the pathogenesis of this condition has not been completely elucidated. The current work presents comprehensive analyses of changes associated with femoral bone degeneration based on findings from gross pathology, histopathology, biochemistry, and synchrotron-based imaging techniques. Gross lesions were predominantly seen in epiphysis and metaphysis of the proximal femur, and infrequently in distal femur, but we did not observe gross lesions in the diaphysis. Bone fractures were observed occasionally, but the most common lesions involved separation of articular cartilage of the femoral bone head, with progressive erosions of the subchondral bone. In advanced cases, on histopathological examination, changes in femoral bone were indicative of chondronecrosis and osteonecrosis. Computed tomography revealed that the degenerative process involves loss of trabecular bone. The course of the lesion development in the mineralized matrix appears to be coupled with increased bone resorption associated with excessive proliferation of pathologically altered osteoclasts. Light microscopy, Fourier transform infrared spectroscopy, and biochemical analysis provided consistent evidence that lowered protein content of the bone organic matrix is an integral component of femoral bone pathology, but these changes do not appear to be associated with excessive activity of matrix metalloproteinases. Taken together, our findings indicate that femoral bone degeneration is associated with structural changes occurring in both inorganic and organic matrix of the bone, but insufficiency in protein metabolism is most probably a primary aetiological factor in the natural history of femoral bone degeneration. However, it is important to stress that our findings do not negate the importance of bacterial infection in the evolution of this condition. Pathogens play a critical role in the progressive pathogenesis of this condition, which ultimately is manifested, in most instances, as femoral head necrosis.

Abstract: Unlike traditional “wet” analytical methods which during processing for analysis often result in destruction or alteration of the intrinsic protein structures, advanced synchrotron radiation-based Fourier transform infrared microspectroscopy has been developed as a rapid and nondestructive and bioanalytical technique. This cutting-edge synchrotron-based bioanalytical technology, taking advantages of synchrotron light brightness (million times brighter than sun), is capable of exploring the molecular chemistry or structure of a biological tissue without destruction inherent structures at ultra-spatial resolutions. In this article, a novel approach is introduced to show the potential of the advanced synchrotron-based analytical technology, which can be used to study plant-based food or feed protein molecular structure in relation to nutrient utilization and availability. Recent progress was reported on using synchrotron-based bioanalytical technique synchrotron radiation-based Fourier transform infrared microspectroscopy and diffused reflectance infrared Fourier transform spectroscopy to detect the effects of gene-transformation (Application 1), autoclaving (Application 2), and bio-ethanol processing (Application 3) on plant-based food and feed protein structure changes on a molecular basis. The synchrotron-based technology provides a new approach for plant-based protein structure research at ultra-spatial resolutions at cellular and molecular levels.

Abstract: formation kinetics of self-assembling tubules composed of phytosterol:gamma-oryzanol mixtures were investigated at the Canadian Light Source on the mid-IR beamline using synchrotron radiation and Fourier transform infrared spectroscopy (FT-IR). The Avrami model was fitted to the changing hydrogen bonding density occurring at 3450 cm(-1). The nucleation process was found to be highly dependent on the molecular structure of the phytosterol. The nucleation event for cholesterol:gamma-oryzanol was determined to be sporadic whereas 5 alpha-cholestan-3 beta-ol:gamma-oryzanol and beta-sitosterol:gamma-oryzanol underwent instantaneous nucleation. One-dimensional growth occurred for each phytosterol:gamma-oryzanol mixture and involved the evolution of highly specific intermolecular hydrogen bonds. More detailed studies on the cholesterol:gamma-oryzanol system indicated that the nucleation activation energy, determined from multiple rate constants, obtained using the Avrami model, was at a minimum when the two compounds were at a 1:1 weight ratio. This resulted in drastic differences to the microscopic structures and affected the macroscopic properties such as turbidity. The formation of the phytosterol:gamma-oryzanol complex was due to intermolecular hydrogen bonding, which was in agreement with the infrared spectroscopic evidence.

Abstract: We have tested an approach to identify putative cancer stem cells that involves measurement of the infrared absorption spectrum of individual cells in an aqueous environment, and their subsequent classification using multivariate data analysis techniques. Two primary esophageal cell lines were characterized: the immortalized normal esophageal epithelial cell line, Het-1A, and the esophageal adenocarcinoma cell line, OE33. In addition, we also evaluated spheroids, reflecting stem-like cell populations, which were derived from each parent cell line when grown in serum-free media. As differences in cell size appeared to be a strong discriminating factor, a correction needs to be performed to allow a reliable classification based on infrared absorption spectra. We demonstrated that stem-like cells derived from Het-1A could easily be discriminated on the basis of absorbance differences in the 10001200 cm(-1) spectral interval, whereas this was not possible for OE33. Furthermore, we found that changes due to aging of OE33 cells in culture dominated the infrared absorption spectra and somewhat limited the potential of this approach to identify stem-like cell populations using this in vitro model system.

Abstract: Barley varieties have similar chemical composition but exhibit different rumen degradation kinetics and nutrient availability. These biological differences may be related to molecular, structural, and chemical makeup among the seed endosperm tissue. No detailed study was carried out. The objectives of this study were: (1) to use a molecular spectroscopy technique, synchrotron-based Fourier transform infrared microspectroscopy (SFTIRM), to determine the microchemical-structural features in seed endosperm tissue of six developed barley varieties; (2) to study the relationship among molecular-structural characteristics, degradation kinetics, and nutrient availability in six genotypes of barley. The results showed that inherent microchemical-structural differences in the endosperm among the six barley varieties were detected by the synchrotron-based analytical technique, SFTIRM, with the univariate molecular spectral analysis. The SFTIRM spectral profiles differed (P < 0.05) among the barley samples in terms of the peak ratio and peak area and height intensities of amides I (ca. 1650 cm(-1)) and II (ca. 1550 cm(-1)), cellulosic compounds (ca. 1240 cm(-1)), CHO component peaks (the first peak at the region ca. 1184-1132 cm(-1), the second peak at ca. 1132-1066 cm(-1), and the third peak at ca. 1066-950 cm(-1)). With the SFTIRM technique, the structural characteristics of the cereal seeds were illuminated among different cultivars at an ultraspatial resolution. The structural differences of barley seeds may be one reason for the various digestive behaviors and nutritive values in ruminants. The results show weak correlations between the functional groups' spectral data (peak area, height intensities, and ratios) and rumen biodegradation kinetics (rate and extent of nutrient degradation). Weak correlations may indicate that limited variations of these six barley varieties might not be sufficient to interpret the relationship between spectroscopic information and the nutrient value of barley grain, although significant differences in biodegradation kinetics were observed. In conclusion, the studies demonstrated the potential of ultraspatially resolved synchrotron based technology (SFTIRM) to reveal the structural and chemical makeup within cellular and subcellular dimensions without destruction of the inherent structure of cereal grain tissue.