Denaturation Of Myoglobin Research Articles

Determining globular protein stability: guanidine hydrochloride denaturation of myoglobin.

Determining globular protein stability: guanidine hydrochloride denaturation of myoglobin.

Changes in tryptophan microenvironment in horse heart myoglobin due to γ-irradiation

Changes in microenvironment of the two tryptophan residues of horse heart myoglobin subjected to γ-irradiation at concentration of 1 mg/ml and doses of 25–100 krad when no aggregation took place were studied by ultraviolet fluorescence spectrometry. Increase in fluorescence of irradiated myoglobin accompanied by a long wavelength shift from 335 to 340 nm of fluorescence maximum indicated unfolding leading to greater exposure of tryptophan to solvent. Fluorescence quenching by NO 2 − and I − was also more for irradiated myoglobin than for myoglobin. But the degree of exposure of tryptophan in irradiated myoglobin was not complete as evidenced by a further shift of fluorescence maximum to 350 nm in 6 M guanidine hydrochloride (GuHCl). Also, in GuHCl relative fluorescence of both native and irradiated myoglobin increased considerably though the increase for irradiated protein was comparatively less. The Stern-Volmer constants for iodide quenching showed that the amount of fluorescence in native myoglobin accessible to the quencher (55%) increased upon irradiation to 74%. The two tryptophan residues are about equal in their degree of exposure to the solvent. But denaturation of native or irradiated myoglobin rendered the fluorescence of both tryptophan residues completely accessible to I −. The data suggest that the enhanced exposure of tryptophans caused by radiation-induced unfolding of myoglobin makes them susceptible to destruction.

Isolation and Purification of Turkey Heme Proteins

Turkey heme proteins, myoglobin, hemoglobin and cytochrome c were isolated and their interactions were studied. This report describes procedures for the chromatography of myoglobins on CM cellulose, DEAE cellulose and Sephadex columns. DEAE cellulose was used to separate hemoglobin and cytochrome c.Turkey metmyoglobin was shown to display a heterogeneity as demonstrated in CM cellulose column chromatography, polyacrylamide gel electrophoresis, and isoelectric fractionation. Three electrophoretically distinct myoglobins were observed in gel electrophoresis, and seven myoglobins were separated by isoelectric fractionation. The major myoglobin fraction was found to have an isoelectric point of 7.99.Turkey myoglobin was similar to chicken myoglobin, but different from mammalian myoglobin in amino acid composition and molecular weight. Molecular weight of turkey myoglobin was determined to be 18,199.The autoxidation rate of turkey myoglobin exhibited a 6-fold slower rate in the presence of cytochrome c. The cytochrome c reduction of metmyoglobin to reduced myoglobin was the probable mechanism.The heat denaturation of turkey myoglobin is quite similar to myoglobins from other species (1/2 D = 78.0° C.). The denaturation temperature increased by approximately 1° C. as the other heme proteins were added to myoglobin, indicating a protein-protein interaction, thus allowing myoglobin to resist heat denaturation. The heat denaturation study revealed that cytochrome c resists denaturation at 105° C.

Denaturation of Aplysia myoglobin. Equilibrium study

The effect of temperature and solvent composition on the reversible denaturation of Aplysia myoglobin is reported here. The denaturation is accompanied by changes in the haem absorption spectrum, in the intrinsic fluorescence of the protein and in its optical activity in the Soret and ultraviolet regions. Under all conditions examined (i.e. different temperatures, different concentrations of various alcohols and different concentrations of proteins) the system appears to be in a state of true equilibrium and good agreement is found between thermally-induced and solvent-induced transitions. The equilibrium behaviour is consistent with a simple all-or-none model. The same transition is observed when different physical parameters are monitored. The effect of the various alcohols appears to be essentially entropic, since the van't Hoff ΔH∘ is nearly independent of the relative concentration of ethanol (from 0 to ~25% v v ). Moreover, within the errors of the measurements, the van't Hoff heat is independent of temperature, indicating that the Δ Cp cannot be very large. The destabilizing effect of alcohols, dealt with in the framework of a minimum scheme, is considered in terms of differential interaction of the third component with the two forms of the protein. A minimum estimate of the number of alcohol molecules differentially bound by the native and denatured conformations, based on linkage treatment, is found to be nearly independent of the type of alcohol used.

Partial molar volume and gel electrophoretic studies of sperm whale myoglobin and apomyoglobin: Native and urea denatured

The reaction of urea with sperm whale myoglobin and apomyoglobin generates changes in their volumes which are unique and characteristic for these proteins. The partial molar volume of myoglobin exhibited a positive concave functional dependence on urea concentration reaching a maximum at 6.5 M urea. In contrast, the corresponding parameter for apomyoglobin obeyed a negative curvilinear relationship with increasing urea concentration. Gel electrophoretic analysis revealed a similar dichotomy in the kinetics, products, and reaction mechanism(s). Even though the mechanisms for urea denaturation of myoglobin and apomyoglobin differ, both systems were characterized by the operation of a series of reactions which produce several forms of denatured proteins. The singular partial molar volume relationship observed for myoglobin as a function of urea concentration indicates the occurrence of not only a helix to coil transition, but also additional structural transformations. The negative asymptotic relationship found for the apomyoglobin-urea systems is in accord with a helix to coil conversion. The volume decrease resulting from the transformation of myoglobin from a water-free crystalline state to the completely hydrated state is — 0.039 ml/g protein. The dependence of this parameter on the water content of the crystalline protein indicates that electrostriction is the dominant factor involved.

Contribution of Aromatic Residue Interactions to the Stability of Myoglobin: V. Enhancement by Aromatic Compounds of the Rate of Heat Denaturation

Aromatic compounds like chlorpromazine and benzoate and its homologs strongly enhance the rate of heat denaturation of myoglobin. The latter apparently exert their action by complexing with a single kind of site in the hemeprotein. Both charge-transfer and hydrophobic interactions are implicated in complex formation, most probably with the heme moiety.

Formation of a Green Pigment from Tuna Myoglobins

SUMMARY: A green pigment was produced when yellowfin (and other) tuna myoglobins, trimethylamine oxide (TMAO), and cysteine were heated together in 0.1 M phosphate buffer pH 5.7. The green product could not be produced with mammalian myoglobins, which contain no cysteine residues. The roles of myoglobin, cysteine, and TMAO in the production of off‐color (green) cooked tuna were investigated. Denaturation of myoglobin, apparently exposing a sulfhydryl group, was necessary for the greening reaction to occur. TMAO acted as a mild oxidizing agent to promote the formation of a disulfide bond between cysteine and the sulfhydryl group on the denatured myoglobin. TMAO could be replaced by oxygen (air), but cysteine appeared to be specific for the reaction. The green color could be reversed by sodium sulfite, but not by other reducing agents tested.

Structural stability and solvent denaturation of myoglobin.

As judged from the midpoints of the denaturation transition of 31 water-miscible alcohols, ureas, and amides, the effectiveness of these denaturing agents on sperm-whale myoglobin increases with increasing chain length and hydrocarbon content, as expected in view of the disorganization of the hydrophobic interior of this protein. Increase in the hydroxyl content, blocking of the functional amino groups of the ureas and amides by alkyl substitution, and branching of the hydrocarbon portion of the denaturants are of less importance in determining the effectiveness of the denaturants.

Thermal denaturation of myoglobin. I. Kinetic resolution of reaction mechanism

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermal denaturation of myoglobin. I. Kinetic resolution of reaction mechanismElias S. Awad and David A. DeranleauCite this: Biochemistry 1968, 7, 5, 1791–1795Publication Date (Print):May 1, 1968Publication History Published online1 May 2002Published inissue 1 May 1968https://doi.org/10.1021/bi00845a025RIGHTS & PERMISSIONSArticle Views407Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (477 KB) Get e-Alerts Get e-Alerts

Spectral studies on the denaturation of myoglobin

Absorption and fluorescence spectroscopy and optical rotation measurements have been used to follow the denaturation of sperm whale skeletal muscle and horse heart myoglobins by urea and guanidine hydrochloride. The spectral properties of the metmyoglobin forms of each of these proteins change concomitantly during denaturation, and the transitions are compatible with a one-step, cooperative denaturation process. The apomyoglobins from sperm whale and horse undergo transitions at lower concentrations of denaturants than do their respective metmyoglobins, and the data are again compatible with a one-step process. For both metmyoglobins and apomyoglobins, the protein from the sperm whale is significantly more stable than that from the horse. These results are discussed with respect to the chemical bases of the spectral properties, the location and relationship of the chromophores in the atomic model of the protein, and the forces which lead to structural stability.

Heat of ionization and denaturation of sperm-whale myoglobin determined with a microcalorimeter.

Heat of ionization and denaturation of sperm-whale myoglobin determined with a microcalorimeter.

Alkali denaturation of myoglobin and hemoglobin. Studies on the kinetics of the reaction

Denaturation curves by alkali of hemoglobin and myoglobin have been determined under different experimental conditions. Components having different denaturation rates have been found in both pigments. The experimental data are discussed.