Protein-protein and ligand-protein interactions as well as the effect of temperature and applied pressure on protein conformation were investigated by Fourier transform infrared (FTIR) spectroscopy with the use of Fourier self-deconvolution, Fourier derivative, and two-dimensional correlation techniques. The effect of the binding of biotin to avidin on the conformation of the protein was examined. At a biotin concentration of 0.05% (w/v), avidin was stabilized against thermal and pressure-induced denaturation. The IR spectra of avidin recorded as a function of increasing hydrostatic pressure in the presence and the absence of biotin indicated that, in the presence of biotin, avidin adopts a very compact structure in solution. The 2D correlation analysis of the infrared spectra of avidin recorded as a function of increasing temperature over the range of 25--95°C revealed that the protein unfolded via different pathways in the presence and the absence of biotin. Furthermore, the thermally induced conformational changes observed in the absence of biotin were irreversible upon cooling of the protein solution, owing to aggregation of the thermally unfolded protein, whereas in the presence of biotin the protein unfolded and refolded via the same pathway. Variable-temperature FTIR spectroscopy and 2D correlation analysis were also employed to examine correlations between absorptions in the amide I and amide III regions in the spectra of four proteins. The results suggested that the band at 1284 cm-1 in the amide III region may be tentatively assigned to the intermolecular beta-sheet structure formed upon aggregation of thermally unfolded protein. FTIR studies were also conducted to investigate the interaction between the catalytic and regulatory subunits of the enzyme ATCase. The secondary structure of the ATCase holoenzyme was stable up to 60°C. The isolated regulatory subunit denatured at approximately 47°C while the isolated catalytic subunit was thermall

Variable-temperature Fourier transform infrared (VT-FTIR) and circular dichroism (far-UV CD) spectroscopy were employed to investigate the sequence of structural changes responsible for the thermally induced formation of myosin gels with various rheological properties, as measured by dynamic oscillatory rheology, as well as the effects of prior high-pressure processing (HPP) on thermally induced gel formation. The viscoelastic properties of the protein gels were monitored as a function of temperature and were also measured at three fixed temperatures (44, 48, and 68°C). Examination was done of changes in the secondary structure-sensitive amide l'band in the FTIR spectra of the protein in D2O buffer (0.6M KCl, pH 6.4) as a function of temperature, as well as far-UV CD spectra. Myosin solutions were exposed to increasing hydrostatic pressure (100--400 MPa for 10 min at 16°C). The extent of unfolding of the tail was shown to be proportional to the pressure treatment, suggesting that the slight increase of gel strength may partly originate from the facilitated tail-tail interaction. (Abstract shortened by UMI.)

Fourier transform infrared (FTIR) spectroscopy was employed to monitor the oxidation of edible oils in the absence and presence of antioxidants. Three synthetic antioxidants (butylated hydroxyanisole, propyl gallate and tert-butylhydroxyquinone) were added to menhaden oil at three different concentrations (1%, 0.1%, and 0.01%), and the FTIR spectra of the oils under conditions of oxidative stress were recorded as a function of time. The efficacy of each antioxidant was assessed by monitoring bands at 3444 cm$ sp{-1}$, characteristic of hydroperoxide formation, 971 cm$ sp{-1}$ for trans double bond formation, and 3008 cm$ sp{-1}$ for cis depletion. An FTIR spectroscopic method was also developed for the determination of the peroxide value of edible oils undergoing oxidation, based on the measurement of the 3444-cm$ sp{-1}$ band. The results of the FTIR method were compared to those from both the iodometric chemical method and the enzymatic hemoglobin-methylene blue assay for the determination of hydroperoxide content. The FTIR predictions were within $ pm$3% of the values obtained by both the chemical and the enzymatic method. Finally, the determination of the hydroxyl value of emulsifiers by FTIR spectroscopy was investigated. Both attenuated total reflectance (ATR) and transmission flow cell techniques were used to record the spectra of commercial monoglycerides. Calibration models for the prediction of hydroxyl value from the FTIR spectra were developed using partial-least-squares (PLS) regression for both the ATR and transmission spectra. Cross-validation of the calibration models yielded an overall average error in the predicted hydroxyl values of $ sim$3% for both the ATR and transmission flow cell methodologies. Linear regression of the FTIR-predicted versus the hydroxyl values determined by the reference chemical method yielded r = 0.998 for the ATR and r = 0.997 for the transmission flow cell method.

No description available.

The purpose of this research was to develop a more convenient method to distinguish bacteria using Fourier transform infrared (FT-IR) spectroscopy. The specular reflectance infrared spectra of bacterial colonies were obtained in-situ, without removing them from the agar growth media. The spectra of a variety of bacterial species were obtained by the infrared microscope and then were analyzed by factor analysis. Using this statistical method in conjunction with in-situ sampling we evaluated how well Grampositive species were sorted from Gram-negative species. Also, how the type of agar used and how the age of bacterial colonies affects the results of Gram stain predictions were evaluated; our experiments showed that the influence of those various conditions can be decreased. The suitability of various sets of standard spectra for predicting Gram stain, including sets constructed with and without Kramers-Kronig transformation and those constructed using partial regions verses the complete mid-infrared region, was evaluated.The effect that water on the surface of the colonies has been studied in distinguishing bacteria. Furthermore, the original method was improved and the method's suitability to differentiate a larger number of different bacterial species was examined. / Department of Chemistry

The wavelet transform technique has been frequently used in time-frequency analysis as a relatively new concept. Compared to the traditional technique Short-time Fourier Transform (STFT), which is theoretically based on the Fourier transform, the wavelet transform has its advantage on better locality in time and frequency domain, but not significant as the solutions in spectrum. Wavelet transform has dynamic ‘window functions’ to represent time-frequency positions of raw signals, and can get better resolutions in time-frequency analysis. In this report, we shall first briefly introduce fuzzy sets and related concepts. And then we will evaluate their similarities and differences by not only the theoretic comparisons between STFT and wavelet transform, but also the process of the de-nosing to a noisy recorded signal.

New techniques in Fourier transform nuclear magnetic resonance spectroscopy are introduced with chemical applications to the study of molecules in the liquid state. Recently a theoretical description of magnetic resonance in terms of single transition operators has been introduced which provides a geometric interpretation of the behaviour of a spin system. This formalism is developed further and extended to the general description of a system of nonequivalent spin-1/2 nuclei. Operator combinations are introduced which allow extension of the convenient geometric representation to the concerted behaviour of coupled spins. The operator formalism is applied to the excitation and detection of multiple quantum transitions, providing a description of the processes in terms of rotating vectors. The process of coherence transfer in two-dimensional Fourier transform experiments is studied in detail and single transition operators are used to derive a general expression for the tip angle dependence of the detection process. A method of discriminating the sense of precession of double quantum coherence is presented and applied to the correlation of chemical shifts of carbon-13 spins in natural abundance. A new technique is presented for the correlation of chemical shift information in coupled proton spin systems in which excitation and indirect detection of double quantum transitions is used to assign coupling patterns in complex spectra. The tip angle dependence of the detection process is used to suppress all but direct correlation of spins. Methods for the measurement of heteronuclear coupling constants in proton spectra are introduced which discriminate the heteronuclear satellites from the parent proton resonance. The technique provides a sensitivity advantage over direct measurement of coupling in the heteronuclear spectrum. Ambiguities are encountered when the protonproton and proton-heteronuclear coupling constants are of the same order of magnitude. This problem is overcome by extension of the basic experiment to its two-dimensional analogue.

In this work, a rapid Fourier transform near infrared (FT-NIR) spectroscopic peroxide value (PV) method was developed and a prototype Continuous Oil Analysis and Treatment (COAT) system was assessed for monitoring and analytical purposes. High erucic acid rapeseed oil, a principle representative of triglyceride based oils suitable for biodegradable lubricating applications and mineral oil were used to test the methodology developed. / The FT-NIR PV method is based on a well defined stoichiometric reaction of triphenylphospine (TPP) with hydroperoxides to form triphenylphospine oxide (TPPO). A partial least squares calibration model for the prediction of PV was developed using the NIR spectral region where TPP and TPPO co-absorb. The resulting calibration was highly linear over the analytical range of 100PV. Validation of the method carried out by comparing the PV of PLS prediction to the results of AOCS iodometric procedures indicated an excellent concurrence between the two methods. By programming the FT-NIR spectrometer, the analytical procedure simply consists of the addition of TPP stock solution to oil sample, mixing, taking its spectrum and predicting PV value. Through selected testing procedures, the prototype COAT system utilizing FTIR spectroscopy, advanced sample handling system designs, and computer programming was proved to be effective in monitoring the oil quality and behavior of antioxidants in real time. / Both approaches offer combined advantages of speed, accuracy, low labor cost, automation, and environmental friendliness mainly derived from FTIR spectroscopy, and can serve as convenient means for routine quality control applications in oils and fats industry. Potential application based on the joint usage of the two methods in the obtaining of true value of oil stability was also presented in this text. (Abstract shortened by UMI.)

The process by which foods are browned during baking and roasting is attributed to the Maillard reaction. The interaction of the $ alpha$-hydroxycarbonyl moiety of a reducing sugar with an amino compound can result in a complex series of changes. The identification and isolation of the key intermediates, known as the Amadori rearrangement product (ARP) and Heyns rearrangement product (HRP), can provide a greater understanding of the browning process. / Fourier transform infrared (FTIR) analysis of 1-hydroxyacetane provided qualitative and quantitative information of the behavior of this $ alpha$-hydroxycarbonyl compound in various aqueous and non-aqueous solutions. / The carbonyl peaks (in the 1750-1700 $ rm cm sp{-1}$ absorption region) due to the keto and aldehydo forms of 1-hydroxyacetone (acetol) in the pure state and in deuterium oxide $ rm(D sb2O)$ were assigned. Upon addition of the acid-base catalysts (triethylamine, 5% NaOD and 5% DCl) additional peaks were detected in the alkene region (1700-1650 $ rm cm sp{-1})$ due to the formation of enediols by enolization. The examination of analogous hydroxycarbonyl structures (1-hydroxy-2-butanone, glyceraldehyde, glycoaldehyde and dihydroxyacetone) provided the means to confirm the assignments of the carbonyl and enediol bands. / The integrated intensity of the carbonyl peak of 1-hydroxyacetone centered at 1720 $ rm cm sp{-1}$ was determined for dilute solutions in $ rm D sb2O.$ The integrated molar absorptivity of the carbonyl band was calculated to be 3674 L/mol/cm. In addition, the effect of concentration and temperature on dimer dissociation was investigated. The effect of solvent and temperature on enolization was also studied. Time run analysis of the carbonyl-amine reaction of 1-hydroxyacetone with pyrrolidine provided the basis for a kinetic study of the rearrangement process in the early stage of Maillard reaction.

The application of Fourier transform infrared (FTIR) spectroscopy in the assessment of oil quality and stability and the determination of the degree and type (cis or trans) of unsaturation of fats and oils was investigated. FTIR spectroscopy was shown to provide a rapid means of monitoring changes in oils undergoing oxidation or subjected to thermal stress. Absorption bands associated with common primary and secondary oxidation products were identified by relating them to those of spectroscopically representative reference compounds, and a quantitative approach based on the use of oils spiked with these reference compounds as calibration standards was proposed. A sample-handling accessory based on a heated 25-mum transmission flow cell and heated input and output lines was developed to facilitate the rapid analysis of oils and premelted fats in their neat form. Using this system, an FTIR edible oil analysis package was developed to simultaneously analyze for trans content, cis content, iodine value (IV), and saponification number (SN) of neat fats and oils, using partial-least-squares (PLS) calibrations based on pure triglycerides. An automated transmission-based peak height method for isolated trans isomer determination using the characteristic trans absorption band at 967 cm -1 in the spectrum of a neat fat or oil, ratioed against the spectrum of a trans-free oil, was also developed. A subsequent validation study involving the analysis of more than 100 oil samples demonstrated concurrence between the trans data obtained by the PLS and peak height FTIR methods as well as between IV results obtained by FTIR analysis and gas chromatography. In addition, the internal consistency of the IV, cis, and trans FTIR predictions provided strong experimental evidence that the FTIR edible oil analysis package measures all three parameters accurately. A PLS-based IV/trans method was developed for a heated single-bounce horizontal attenuated total reflectance (SB-HATR) sample-