Generalized Two-Dimensional Attenuated Total Reflection/Infrared and Near-Infrared Correlation Spectroscopy Studies of Real-Time Monitoring of the Initial Oligomerization of Bis(hydroxyethyl terephthalate)

2002 ◽  
Vol 35 (21) ◽  
pp. 8020-8028 ◽  
Author(s):  
Toru Amari ◽  
Yukihiro Ozaki
Keyword(s):  
Real Time ◽  
Near Infrared ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Correlation Spectroscopy ◽  
Two Dimensional ◽  
Real Time Monitoring ◽  
Spectroscopy Studies

Two-Dimensional Attenuated Total Reflection Infrared and Near-Infrared Correlation Study of the Structure of Butyl Alcohol/Water Mixtures

2007 ◽  
Vol 61 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Dagmara Wojtków ◽  
Mirosław A. Czarnecki
Keyword(s):  
Near Infrared ◽  
Correlation Study ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Effect Of Temperature ◽  
Two Dimensional ◽  
Experimental Conditions ◽  
Oh Groups ◽  
Alcohol Water ◽  
Anharmonicity Constants

The effect of temperature on attenuated total reflection infrared (ATR-IR) and near-infrared (NIR) transmission spectra of pure butan-1-ol, butan-2-ol, 2-methyl-propan-1-ol, 2-methyl-propan-2-ol, and mixtures with a small water content (XH2O ≤ 0.1) have been examined. The spectra were analyzed using a two-dimensional (2D) correlation approach. Two kinds of correlation analysis were performed: IR–IR and NIR–NIR homo-correlation and IR–NIR hetero-correlation. Our results reveal that the addition of small to moderate amounts of water does not destroy the structure of alcohol. The presence of water stabilizes the structure of alcohols and this effect is more evident for sec-butanol and tert-butanol. The ATR-IR spectra provide information on the most associated species, whereas absorption of the smaller associates and the free OH group is hardly seen. On the contrary, in the NIR spectra the absorption of the free OH groups dominates. The ability of resolution enhancement in the hetero-correlation asynchronous spectra is reduced as compared to that in the homo-correlation spectra. On the other hand, peaks may appear in the hetero-correlation synchronous spectra that are not observed in the homo-correlation contour plots. The positions of the synchronous peaks were used for evaluation of anharmonicity constants. These values for the free OH group do not depend on the experimental conditions. In contrast, the anharmonicity constants for the bonded OH groups determined from the spectra of pure alcohols may significantly differ from those obtained from diluted solutions.

Two-Dimensional Attenuated Total Reflection/Infrared Correlation Spectroscopy Studies on Concentration and Heat-Induced Structural Changes of Human Serum Albumin in Aqueous Solutions

2002 ◽  
Vol 56 (9) ◽  
pp. 1186-1193 ◽  
Author(s):  
Yuqing Wu ◽  
Koichi Murayama ◽  
Boguslawa Czarnik-Matusewicz ◽  
Yukihiro Ozaki
Keyword(s):  
Secondary Structure ◽  
Human Serum Albumin ◽  
Serum Albumin ◽  
Aqueous Solutions ◽  
Ir Spectra ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Correlation Spectroscopy ◽  
Random Coil ◽  
Two Dimensional

Attenuated total reflection (ATR)/FT-IR spectra were measured for human serum albumin (HSA) in aqueous solutions (pH 6.6) with concentrations of 1.0, 2.0, 3.0, 4.0, and 5.0 wt % over a temperature range of 45–80 °C. Generalized two-dimensional (2D) correlation spectroscopy was employed to explore concentration and heat-induced structural variations of HSA in aqueous solutions. To generate 2D correlation spectra, the raw spectra were subjected to the appropriate pretreatment procedure involving ATR correction, subtraction of the spectrum of an aqueous solution, and smoothing. The synchronous and asynchronous correlation spectra were calculated for the concentration-dependent IR spectral variations in the amide I region at various temperatures. The two-dimensional ATR/IR correlation spectra greatly enhance band separation in the region and provide information about the correlation between the amide bands of HSA arising from the same and different secondary structure components. Based on the correlation investigated and previously proposed relationship between the secondary structure elements and the amide band frequencies, we have proposed the detailed assignments in the amide I region at 45 and 80 °C. The proposed assignments are compared with those based on the results of second derivative and Fourier self-deconvolution (FSD) of the ATR/IR spectra. The asynchronous spectrum generated from the concentration-dependent spectral variations at 45 °C show that side chains, the random coil, and extended chains are more sensitive than the α-helices and β-turns to the concentration change. On the other hand, the corresponding spectrum at 80 °C reveals that the conformation changes in side chains and β-turns (or β-strands) of HSA start before those in extended chain, random coil structures, and α-helices.

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