Infrared Absorption and Ultraviolet-Circular Dichroism Spectral Studies of Thermally Induced Unfolding of Apomyoglobin

Mohney, Brian K.; Petri, Edward T.; Uvarova, Victoria; Walker, Gilbert C.

doi:10.1366/0003702001948303

Cited by 6 publications

(3 citation statements)

References 34 publications

(29 reference statements)

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“…Since DNA and protein lose their helicity by increasing temperature, we would expect PANI optical activity to also decrease when it is heated. In fact, the unraveling of chiral 32 or helical 33 polymer conformation at elevated temperature is commonly observed. To further examine the stability of our chiral nanocomposites, we carried out experiments to determine their thermal and chemical stability.…”

Section: Effect Of Templatementioning

confidence: 99%

Toward Understanding and Optimizing the Template-Guided Synthesis of Chiral Polyaniline Nanocomposites

McCarthy

Liu

et al. 2002

Macromolecules

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Previously we reported synthesis and characterization of water-soluble chiral conducting polymer nanocomposites via template-guided synthesis. Experimental procedures and parameters need to be carefully controlled to achieve synthesis of water-soluble nanocomposites. Here, we describe a modified synthetic procedure with higher molecular weight poly(acrylic acid) (PAA) (MW ∼ 250 000) as a template. This new system allows synthesis of chiral water-soluble nanocomposites over a more broad range of conditions making the synthesis more reproducible and easier to carry out at large scale. Another objective of this work is to further understand the underlying formation mechanism of chiral polyaniline nanocomposites. We carried out a detailed study of how temperature, template, and solvent affect the final morphology and properties of these nanocomposites. We found that the extent of interaction and stability of the template/monomer/acid adduct (nanocomposite precursor) and population density of monomer surrounding the template are crucial in determining the degree of nanocomposite chirality. Detailed characterization of the nanocomposites and their precursors was carried out by circular dichroism (CD), UV-vis, FTIR, NMR, and TEM spectroscopy. On the basis of experimental results and synthetic procedures, a simplified model for the formation mechanism of chiral polyaniline nanocomposite is proposed.

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Section: Effect Of Templatementioning

confidence: 99%

Toward Understanding and Optimizing the Template-Guided Synthesis of Chiral Polyaniline Nanocomposites

McCarthy

Liu

et al. 2002

Macromolecules

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“…Turbidity measurements, which detect the presence of macroscopic (1 mm or larger) aggregates, have shown that horse heart apoMb forms heavily self-associated species at moderate urea concentrations (22), reaching a minimum solubility at 2.4 M. However, the turbidity measurements carried out in this study do not allow detection of smaller soluble aggregates nor characterization of particle morphology. Horse heart apoMb is known to form large insoluble irreversible aggregates at temperatures above 50°C (23). Under more extreme conditions, i.e., at high pH and temperature, the protein irreversibly self-associates and forms amyloid fibrils, containing a significant amount of b-sheet secondary structure (24,25).…”

Section: Introductionmentioning

confidence: 99%

Structural Characterization of Apomyoglobin Self-Associated Species in Aqueous Buffer and Urea Solution

Chow

Kurt

Murphy

et al. 2006

Biophysical Journal

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The biophysical characterization of nonfunctional protein aggregates at physiologically relevant temperatures is much needed to gain deeper insights into the kinetic and thermodynamic relationships between protein folding and misfolding. Dynamic and static laser light scattering have been employed for the detection and detailed characterization of apomyoglobin (apoMb) soluble aggregates populated at room temperature upon dissolving the purified protein in buffer at pH 6.0, both in the presence and absence of high concentrations of urea. Unlike the beta-sheet self-associated aggregates previously reported for this protein at high temperatures, the soluble aggregates detected here have either alpha-helical or random coil secondary structure, depending on solvent and solution conditions. Hydrodynamic diameters range from 80 to 130 nm, with semiflexible chain-like morphology. The combined use of low pH and high urea concentration leads to structural unfolding and complete elimination of the large aggregates. Even upon starting from this virtually monomeric unfolded state, however, protein refolding leads to the formation of severely self-associated species with native-like secondary structure. Under these conditions, kinetic apoMb refolding proceeds via two parallel routes: one leading to native monomer, and the other leading to a misfolded and heavily self-associated state bearing native-like secondary structure.

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“…4 Since then, FT-IR spectroscopy has been applied in a number of qualitative and quantitative conformation studies. These have dealt with the denaturation/unfolding and aggregation of proteins induced by heat, [5][6][7][8][9] pH, 10 denaturants, 7 buffers, 8 etc., and with protein conformational changes upon enzymatic cleavage, 11 ligand binding, oligomerization, 9 etc. Also, a change in the secondary structure of human serum albumin (HSA) upon coordination of cis-platin to the protein backbone has been elucidated by FT-IR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Application of Near-Infrared and Fourier Transform Infrared Spectroscopy in the Characterization of Ligand-Induced Conformation Changes in Folate Binding Protein Purified from Bovine Milk: Influence of Buffer Type and pH

et al. 2006

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Fourier transform infrared (FT-IR) and near-infrared (NIR) spectroscopy have been applied to detect structural alterations in folate binding protein (FBP) induced by ligation in different buffer types. The amide I region pointed to a beta-sheet to alpha-helix transition upon ligation in acetate and phosphate buffers, and the formation of intermolecular beta-sheet was indicated at pH 5.0, in agreement with a dimerization of FBP taking place at this pH. The ligand-induced changes in the 2100-2300 nm NIR region were significant for FBP in acetate and phosphate buffers of pH 5.0, and the variations were interpreted as secondary structure changes, based on previous assignments of secondary structures to the combination bands in the NIR region. In the case of acetate buffer, variations in the amide combination bands agreed with the amide I analysis, but for the other buffer types some discrepancies were found and explained by side-chain contributions to the NIR, which could reflect the tertiary and quaternary structure differences. NIR spectra of FBP at pH 7.4 and 5.0 revealed contradictory effects on the side chains, reflecting different polymerization events at the two pH values, whereas the amide I region indicated similar changes at the two pH values. Therefore, we suggest that FT-IR and NIR spectroscopy may complement each other, such that the two techniques in combination may give information on all three types of protein conformational changes. While the secondary structure changes are revealed by FT-IR, the tertiary and quaternary structure changes are reflected in the NIR spectra, although the general influence of the latter changes on the NIR spectra remains to be confirmed.

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Infrared Absorption and Ultraviolet-Circular Dichroism Spectral Studies of Thermally Induced Unfolding of Apomyoglobin

Cited by 6 publications

References 34 publications

Toward Understanding and Optimizing the Template-Guided Synthesis of Chiral Polyaniline Nanocomposites

Toward Understanding and Optimizing the Template-Guided Synthesis of Chiral Polyaniline Nanocomposites

Structural Characterization of Apomyoglobin Self-Associated Species in Aqueous Buffer and Urea Solution

Application of Near-Infrared and Fourier Transform Infrared Spectroscopy in the Characterization of Ligand-Induced Conformation Changes in Folate Binding Protein Purified from Bovine Milk: Influence of Buffer Type and pH

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