Temperature-dependent water structural transitions examined by near-IR and mid-IR spectra analyzed by multivariate curve resolution and two-dimensional correlation spectroscopy

2005 ◽  
Vol 544 (1-2) ◽  
pp. 15-25 ◽  
Author(s):  
Boguslawa Czarnik-Matusewicz ◽  
Sylwia Pilorz ◽  
Jerzy P. Hawranek
Keyword(s):  
Ir Spectra ◽  
Correlation Spectroscopy ◽  
Multivariate Curve Resolution ◽  
Two Dimensional ◽  
Structural Transitions ◽  
Temperature Dependent ◽  
Curve Resolution ◽  
Near Ir

Two-Dimensional Correlation Spectroscopy (2D-COS) of Gas-Phase Pyrrole Clusters in a Supersonic Jet: Treatment of Sharp Bands on a Broad Background

2020 ◽  
Vol 74 (4) ◽  
pp. 408-416
Author(s):  
Yoshiteru Matsumoto ◽  
Souichi Tezuka
Keyword(s):  
Ir Spectra ◽  
Gas Phase ◽  
Supersonic Jet ◽  
Correlation Spectroscopy ◽  
Cavity Ringdown Spectroscopy ◽  
Two Dimensional ◽  
Cavity Ringdown ◽  
Correlation Spectrum ◽  
Large Clusters ◽  
Small Clusters

Two-dimensional correlation spectroscopy (2D-COS) is a useful technique to analyze any intensity behavior of optical spectra that exhibit a complicated feature with overlapped bands. In this study, we apply 2D-COS to the infrared (IR) spectra of gas-phase pyrrole (Py) clusters. The NH stretching vibrations of the Py clusters are measured by cavity ringdown spectroscopy. The observed IR spectra of the Py clusters consist of sharp bands, full width half-maximum (FWHM) ∼1 cm−1, and a broad background (FWHM >50 cm−1). The 2D asynchronous correlation spectra reveal that the sharp bands and a broad background are assigned to small clusters of dimer to pentamer and large clusters with bulk-like structures, respectively, which support the results of our previous study. The sharp bands are also analyzed using another 2D asynchronous correlation spectrum, which is obtained by decomposing the observed IR spectra into sharp and broad components. Because the asynchronous signals are consistent with those obtained from the IR spectra without decomposition, the result would suggest that we need not to decompose the IR spectra into sharp and broad components before applying 2D-COS. However, our model simulations of 2D-COS showed a counterexample that gives an incorrect result without removing a broad background component from the IR spectra. This study strongly suggests that we need to undertake a careful treatment of the complicated IR spectrum with various widths of bands.

Two-Dimensional Infrared Spectroscopy and Principal Component Analysis Studies on a New Azobenzene Derivative Supramolecular System Based on Hydrogen Bonds

2003 ◽  
Vol 57 (8) ◽  
pp. 933-942 ◽  
Author(s):  
Yuqing Wu ◽  
Ya-Qiong Hao ◽  
Min Li ◽  
Chaowei Guo ◽  
Yukihiro Ozaki
Keyword(s):  
Principal Component Analysis ◽  
Hydrogen Bonds ◽  
Supramolecular Assembly ◽  
Principal Component ◽  
Correlation Spectroscopy ◽  
Supramolecular System ◽  
Two Dimensional ◽  
Temperature Dependent ◽  
2D Correlation Spectroscopy ◽  
2D Correlation Analysis

Infrared (IR) spectra of a supramolecular assembly with an azobenzene derivative and intermolecular hydrogen bonds have been measured in the temperature range from 30 to 200 °C to investigate heat-induced structural changes and thermal stability. Principal component analysis (PCA) and two kinds of two-dimensional (2D) correlation spectroscopy, variable–variable (VV) 2D and sample–sample (SS) 2D spectroscopy, have been employed to analyze the observed temperature-dependent spectral variations. The PCA and SS 2D correlation analyses have demonstrated that the complete decoupling of hydrogen bonds in the supramolecular assembly occurs between 110 and 115 °C, which is in good agreement with the results of a differential scanning calorimetry (DSC) study for the heating process. The PCA of the IR spectra in the region of 3600–3100 cm−1 has illustrated that there are at least four principal components for the different NH2 and CONH species in the present supramolecular system. The VV 2D correlation spectroscopy study has provided information about the structure and strength of hydrogen bonds of NH2 and CONH groups and their temperature-dependent variations. The different species of hydrogen-bonded NH2 and CONH groups in the supramolecular system can be clarified by the VV 2D correlation analysis. The VV 2D correlation analysis has also revealed the specific order of the temperature-induced changes in the hydrogen bonds of NH2 and CONH groups.

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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