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PubMed1994

Mini-myoglobin: native-like folding of the NO-derivative.

Mini-myoglobin is a polypeptide fragment (residues 32-139) obtained by limited proteolysis of horse heart apomyoglobin and reconstituted with the natural heme. Its functional properties are very similar to those of native myoglobin and therefore it may represent a model for testing the functional role of the protein fragment encoded by the central exon of myoglobin gene (residues 31-105). Here we have investigated some properties of the nitric oxide derivative of mini-myoglobin in comparison with those of NO-myoglobin, to provide more structural information on the heme pocket residues in addition to that already acquired by electron paramagnetic resonance of the cobalt-substituted mini-myoglobin. At pH 7.0, optical and circular dichroism Soret spectra, as well as electron paramagnetic resonance spectra reveal that the heme orientation in the pocket and the coordination state of the ferrous iron in NO-mini-myoglobin are similar to those of the whole protein. The spectra of the NO-mini-myoglobin complex are very sensitive to pH changes at variance to what is observed for the NO-myoglobin derivative in the same pH range (5.5-9.5). In particular, increasing or decreasing pH from 7.0, results in a decrease of the extinction coefficient and of the ellipticity in the Soret region and in a change of the shape of the electron paramagnetic resonance signal. The spectral changes are diagnostic for a transition from a hexa-coordinated (at pH 7.0) to a penta-coordinated heme (at pH 5.5 or 9.5), with the proximal histidine-iron bond either broken or stretched dramatically. Thus, although mini-myoglobin is able to bind NO in a geometry similar to that of the native protein, the resulting NO derivative shows a much higher pH dependence, suggesting that the two lacking side domains are mainly involved in enhancing the stability of the hemoprotein core.

Animals↗

PubMed2002

Elimination kinetics of myoglobin and creatine kinase in rhabdomyolysis: implications for follow-up.

OBJECTIVE: Creatine kinase and myoglobin are markers of muscular damage in rhabdomyolysis. Whereas myoglobin is considered to be the principal compound causing tubular damage, serum creatine kinase level is presently guiding therapeutic interventions in clinical practice to prevent acute renal failure. Because differences in elimination kinetics of these two compounds may influence therapeutic decisions, we studied elimination kinetics of myoglobin and creatine kinase in patients with rhabdomyolysis. DESIGN: Open, noncomparative study. SETTING: Intensive and intermediary care units in a university hospital. PATIENTS: A total of 13 consecutive patients with rhabdomyolysis whose baseline serum creatine kinase exceeded 5000 IU/L. Ten of 13 patients were treated with forced alkaline diuresis, and none were dialyzed. RESULTS: Myoglobin had faster elimination kinetics than creatine kinase (p <.01), and the average times to reach the 50% level of initial values were 12 hrs for myoglobin and 42 hrs for creatine kinase. Elimination of myoglobin was not affected by glomerular filtration rate. Compared with creatinine clearance (mean, 102 mL/min), myoglobin clearance was low (mean, 3 mL/min), both in patients with preserved renal function (n = 11) and in those with acute renal failure (n = 2). CONCLUSION: Serum myoglobin has faster elimination kinetics than creatine kinase in patients treated with forced alkaline diuresis for rhabdomyolysis. Considering the etiologic role of myoglobin, our data suggest that serum myoglobin level, rather than that of creatine kinase, should be used to guide therapy in patients with rhabdomyolysis.

Adolescent↗

PubMed1993

Trimethylphosphine binding to horse-heart and sperm-whale myoglobins. Kinetics, proton magnetic resonance assignment and nuclear Overhauser effect investigation of the heme pocket.

Two-dimensional nuclear magnetic resonance techniques have been used to assign resonances corresponding to the heme pocket and several other residues of horse heart and sperm whale myoglobins ligated by trimethylphosphine. The assignment procedure was based mainly on the nuclear Overhauser effect connectivities with the ligand and the heme substituents. For quantitative measurements of Overhauser effects, application of truncated driven techniques between a proton from distal residues and methyl groups from the ligand was used to determine internuclear distances. These new results have permitted us to map the heme pockets and to investigate the conformational differences in the heme pockets between horse heart and sperm whale myoglobins. The interproton distances between distal amino acid residues and trimethylphosphine were found to be longer in horse heart myoglobin relative to those in sperm whale myoglobin. This result suggests that the size of the heme pocket is larger in horse heart myoglobin. Association and dissociation rate constants were measured for trimethylphosphine binding to myoglobins. Both values were four times larger for horse heart myoglobin than those for sperm whale myoglobin. This observation confirms the structural results obtained with NMR studies and is rationalized by a greater stabilization of a larger pocket in horse heart myoglobin relative to sperm whale myoglobin.

Animals↗

PubMed1988

Measurement of myoglobin diffusivity in the myoplasm of frog skeletal muscle fibres.

1. Experiments were carried out on intact, single skeletal muscle fibres from frog in order to estimate the apparent diffusion constant of myoglobin (denoted DAPP) in the myoplasm of living muscle cells. An optical technique was employed to measure myoglobin concentration along the fibre axis following injection of metmyoglobin (denoted metMb) at a point source. The concentration profiles were fitted by the one-dimensional diffusion equation to give estimates of DAPP. The method relied on the fact that myoglobin is normally absent from these frog fibres, thus permitting resolution of the myoglobin-related absorbance above the intrinsic absorbance of the fibre. 2. One complication in the method was that metMb became significantly reduced to oxymyoglobin (denoted MbO2) during the elapsed time before measurement of the concentration profile. The rate of reduction was evaluated by fitting myoglobin-related absorbance spectra, measured at different times following injection of metMb, with in vitro absorbance spectra of metMb and MbO2. Results from four experiments indicated that reduction could be described by a first-order, irreversible reaction having an average rate constant of 0.0164 min-1 (22 degrees C). The effect of reduction on the fitting of DAPP was taken into account. 3. DAPP was determined under three fibre conditions: (1) long sarcomere spacing (3.6-3.8 microns) at 16 degrees C, (2) long sarcomere spacing at 22 degrees C, and (3) normal sarcomere spacing (2.4-2.7 microns) at 22 degrees C. The average values for DAPP under these conditions were: (1) 0.12 (n = 5); (2) 0.17 (n = 5); and (3) 0.15 (n = 7) x 10(-6) cm2 s-1. The average value at 22 degrees C, 0.16 x 10(-6) cm2 s-1, is about 4 times smaller than values for myoglobin diffusivity at 20 degrees C commonly assumed in models of facilitated transport of oxygen by myoglobin. 4. In order to test the possibility that the unexpectedly low value of DAPP found in intact fibres might be due to the binding of myoglobin to relatively immobile sites in myoplasm, experiments were carried out in a cut-fibre preparation using a technique described by Maylie, Irving, Sizto & Chandler (1987 b) for determining the diffusion constants and degree of myoplasmic binding of absorbance dyes. Values for DAPP and the factor (denoted 1 + beta) by which the total myoglobin concentration exceeded the free myoglobin concentration were obtained by fitting the absorbance data by solutions of the one-dimensional diffusion equation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Analysis of creatine kinase, CK-MB, myoglobin, and troponin T time-activity curves for early assessment of coronary artery reperfusion after intravenous thrombolysis.

BACKGROUND: Thrombolysis has become the standard therapeutic approach in patients with acute myocardial infarction. To identify patients who may benefit from early invasive procedures, reliable noninvasive assessment of success or failure of thrombolytic therapy is mandatory. METHODS AND RESULTS: In a prospective study in 63 consecutive patients undergoing thrombolysis for their first myocardial infarction, serial measurements of creatine kinase (CK), its isoenzyme CK-MB, myoglobin, and troponin T were done to determine their value for noninvasive prediction of coronary artery patency. Blood samples were drawn every 15 minutes during the first 90 minutes, every 30 minutes during the first 4 hours, every 4 hours during the first 24 hours, and every 8 hours during the first 72 hours. The perfusion status of the infarct-related artery was assessed angiographically 90 minutes after initiation of thrombolysis. For each marker, time to its peak concentration and its early initial slope (start of thrombolysis to 90 minutes thereafter) were determined. Areas under receiver operator characteristic (ROC) curves were 0.83, 0.76, 0.82, and 0.80 for maxima of CK, CK-MB, myoglobin, and troponin T, respectively (p = NS by univariate Z test). The corresponding values for early slopes of CK, CK-MB, myoglobin, and troponin T were 0.79, 0.82, 0.89, and 0.80 (p = 0.23 for comparison between myoglobin and CK-MB; p = 0.07 between myoglobin and CK). Sensitivity, specificity, and positive and negative predictive values regarding noninvasive prediction of coronary artery patency after 90 minutes were 80%, 82%, 95%, and 61% for time to CK maximum; 91%, 77%, 91%, and 77% for time to myoglobin maximum; 87%, 71%, 89%, and 67% for early CK slope; and 94%, 88%, 94%, and 82% for myoglobin slope, respectively. When myoglobin slope was assessed together with other clinical reperfusion markers (resolution of chest pain or ST segment elevation, occurrence of reperfusion arrhythmias) by logistic regression analysis, only the myoglobin slope was an independent predictor of coronary artery patency (p < 0.0001). CONCLUSIONS: With regard to noninvasive prediction of coronary artery patency after thrombolytic therapy, measurement of the early initial slopes of the serum markers within only 90 minutes after the initiation of therapy is as accurate as the determination of the time to their peak concentration. Compared with the other markers examined, myoglobin appears to have advantages because of its earlier rise, yielding a better negative predictive value and a higher area under the ROC curve for determination of its early initial slopes.

Adult↗

PubMed1979

Radioimmunoassays of human myoglobin in serum and urine.

Two solid-phase radioimmunoassays have been developed for the detection of myoglobin in serum and urine. The sensitivity of the methods is 0.1 and 0.5 microgram/l, respectively, with a coefficient of variation of the respective method of 7-8%. The mean serum concentration of myoglobin in ninety-nine healthy blood donors was 44.3 microgram/l +/- 18.0 microgram/l (SD) with a significant difference (P less than 0.001) between men (50.6 +/- 19.8) and women (35.7 +/- 10.4). Serum myoglobin was positively correlated to age (P less than 0.05), body weight (P less than 0.02), serum creatine kinase (P less than 0.001), and serum creatinine (P less than 0.001) to galactose elimination rate. Serum myoglobin levels were not influenced by exhaustive short time dynamic exercise. The mean urinary excretion of myoglobin in twenty-four healthy students was 1.2 microgram/24 h (range 0.1-4 microgram/24 h). Myoglobin excretion was correlated to excretion of beta 2-microglobulin (P less than 0.02) but not to serum levels of myoglobin. No indications of circulating antibodies to myoglobin were obtained when assaying sixty-seven rheumatoid arthritis and thirteen myastenia gravis sera. Presence of other myoglobin binding substances in serum, which would interfere with the assays also seemed unlikely. Determination of myoglobin in serum by sensitive and specific method might be of clinical value in the diagnosis of diseases involving muscle tissues.

Adult↗

PubMed1990

New transient species of sperm whale myoglobin in photodissociation of dioxygen from oxymyoglobin.

We carried out the flash photolysis of oxy complexes of sperm whale myoglobin, cobalt-substituted sperm whale myoglobin, and Aplysia myoglobin. When the optical absorption spectral changes associated with the O2 rebinding were monitored on the nanosecond to millisecond time scale, we found that the transient spectra of the O2 photoproduct of sperm whale myoglobin were significantly different from the static spectra of deoxy form. This was sharply contrasted with the observations that the spectra of the CO photoproduct of sperm whale myoglobin and of the O2 photoproducts of cobalt-substituted sperm whale myoglobin and Aplysia myoglobin are identical to the corresponding spectra of their deoxy forms. These results led us to suggest the presence of a fairly stable transient species in the O2 photodissociation from the oxy complex of sperm whale myoglobin, which has a protein structure different from the deoxy form. We denoted the O2 photo-product to be Mb*. In the time-resolved resonance Raman measurements, the nu Fe-His mode of Mb* gave the same value as that of the deoxy form, indicating that the difference in the optical absorption spectra is possibly due to the structural difference at the heme distal side rather than those of the proximal side. The structure of Mb* is discussed in relation to the dynamic motion of myoglobin in the O2 entry to or exit from the heme pocket. Comparing the structural characteristics of several myoglobins employed, we suggested that the formation of Mb* relates to the following two factors: a hydrogen bonding of O2 with the distal histidine, and the movement of iron upon the ligation of O2.

Animals↗

PubMed1989

[Changes in myoglobin localization in the skeletal muscle of neuromuscular diseases demonstrated by immunohistochemistry and immunoelectron microscopy].

The changes of myoglobin localization in the skeletal muscle cells in Duchenne muscular dystrophy (DMD), myotonic dystrophy (MyD), and amyotrophic lateral sclerosis (ALS) were studied by immunohistochemistry and immunoelectron microscopy. In normal skeletal muscle cells, myoglobin was found in I band, Z line, mitochondrial outer membrane and inner membrane structures of sarcoplasmic reticulum and T tube. In contrast, the myoglobin staining of the I bands in degenerative muscle-cells of DMD and MyD was found rather diminished, and A bands, intraluminal spaces of the inner membrane system and intermyofibrillar spaces were myoglobin positive. Moreover, the I band of a myofibril which slipped out of other normally arranged myofibrils showed no myoglobin staining, but the distended intermyofibrillar spaces adjacent to the slipped myofibril showed a definite staining. In addition, there were dilated sarcoplasmic reticula showing the staining in their lumina, but the I bands neighboring them revealed a diminished staining. In DMD muscle, no staining was found in opaque fibers and some small sized fibers. In ALS muscle, myoglobin was usually positive in the I bands, but the small angulated fibers showed a variable staining. In the target fibers, central zone was not stained but intermediate zone showed altered myoglobin localization. These data indicate that (1) myoglobin localization in the muscle cells varies depending on the sorts of diseases and the grades of muscle cell degeneration, (2) myoglobin in dystrophic muscles fluxes from the muscle cells to extracellular spaces through the dilated sarcoplasmic reticula, T tubes and intermyofibrillar spaces, and (3) in DMD muscle, myoglobin also fluxes directly through the deteriorated plasma membrane in opaque fibers or through the plasma membrane altered due to dystrophin deficiency.

Adolescent↗

PubMed1978

Myoglobin turnover--influence of renal and extrarenal factors.

The serum level of myoglobin, an LMW constituent of striated and myocardial muscle, has been studied in various clinical situations in order to obtain information about factors influencing myoglobin turnover. The myoglobin level was significantly correlated to different variables of GFR such as serum beta2-microglobulin, serum creatinine, and 51Cr-EDTA clearance. Following a successful renal transplantation rapid decrease in serum myoglobin was found parallel to increase in GFR's. In patients with advanced long-standing uremia, comparatively small elevations of serum myoglobin were seen when correlated to the degree of GFR reduction, demonstrating an influence of extrarenal factors on the myoglobin levels. The importance of extrarenal factors on the actual serum level of LMW proteins was also illustrated by serial studies on SLE patients receiving corticosteroid therapy. In these patients, elevations of serum myoglobin levels were found, but serum beta2-microglobulin levels gradually decreased during therapy. Finally, calculations based on curves of serum disappearance of myoglobin in patients with acute myocardial infarction indicate that only about 0.3 mg of myoglobin per day is released from the muscle pool during normal conditions, which suggests that myoglobin catabolism mainly occurs within the muscle tissue.

Adolescent↗

PubMed1983

Interaction of ligands with the distal glutamine in elephant myoglobin.

The effects of distal glutamine (E7) replacement in elephant myoglobin were studied by comparing the temperature-dependent nitrosyl electron spin resonance spectra, redox potentials, and the acid-alkaline equilibria of elephant and human myoglobins. For myoglobins containing a distal histidine, the nitrosyl ESR spectra do not exhibit superhyperfine splitting until near liquid helium temperatures (Yoshimura, T., Ozaki, T., Shintani, Y., and Watanabe, H. (1979) Arch. Biochem. Biophys. 193, 301-313). Studies presented here show that the ESR spectra of nitrosyl elephant myoglobin exhibit 9-line superhyperfine splitting well above liquid nitrogen temperatures, similar to the temperature profiles of isolated heme complexes (Morse, R.H. (1980) Fed. Proc. 39, 2006). It is concluded that the shift in the spectral equilibrium to higher temperature indicates a diminished interaction between NO and the distal position in elephant myoglobin. In addition, the redox potential of elephant myoglobin was found to be nearly 100 mV greater than that of human myoglobin, and the pKa of the acid-alkaline equilibrium (oxidized myoglobin) was 8.5, being 0.4 unit less than that of other vertebrate myoglobins. These different reactivities between elephant and human myoglobins are discussed based on the nature of charge interactions between polar ligands and distal glutamine and histidine.

Animals↗

PubMed1982

Usefulness of myoglobin radioimmunoassay determintion in CCU.

In 112 patients with an acute coronary event, admitted to the CCU of Assaf-Harofeh Hospital, myoglobin radioimmunoassay was determined at 0 (time of admission), 12 and 24 hours. In 77 patients with acute myocardial infarction (M.I.) (64 patients with acute transmural and 13 with acute subendocardial M.I.), the myoglobin values were significantly increased. Appearing in blood 3-4 hours after the onset of chest pains, myoglobin represents the earliest marker of acute M.I. known until know. In 12 of 23 cases diagnosed at first as acute coronary insufficiency according to clinical, biological and E.C.G. criteria, significantly increased values of myoglobin were found, as an expression of micro-necroses which were not detected by conventional methods (SGOT, CPK, LDH). This finding has important practical, prognostic and therapeutical implications, showing that myoglobin radioimmunoassay may detect myocardial micronecroses which are not discovered by usual methods. Myoglobin radioimmunoassay assessment offers a valuable indication of necrosis extent. Values above 800 ng/ml were accompanied in 65% of our cases with symptoms and signs of left heart failure, the highest values of myoglobin being found in extensive anterior M.I. associated with acute pulmonary edema. In 9 non cardiac patients with repeated intra-muscular injections with antibotics, the myoglobin was at the upper normal limit, demonstrating that intra-muscular injections, at least with antibiotics, have no influence on myoglobin values. From our experience it appears that the myoglobin radioimmunoassay determination is a useful tool for the early establishment of M.I. diagnosis and the assessment of myocardial necrosis extent.

Adult↗

PubMed1997

Reduction of myocardial myoglobin in bovine dilated cardiomyopathy.

Myoglobin levels are decreased in various animal models of heart failure, a change that has been associated with compromised energy supply. The underlying mechanisms by which myoglobin content decreases in failing myocardium are unknown. Bovine hereditary cardiomyopathy (bCMP) displays several characteristics of human dilated cardiomyopathy with a marked desensitization of the beta-adrenoceptor signal cascade. The aim of the present study was to investigate whether a similar reduction of myoglobin can be seen in this animal model, and to elucidate the possible mechanism of this reduction. Myoglobin protein concentration was decreased by 46-47% (P < 0.05) in left and right ventricular myocardium of failing hearts (n = 9) compared to control hearts (n = 11). No difference was found between atria of diseased and control animals. Immunohistochemistry with a polyclonal antibody against myoglobin revealed a strong and uniform labeling in cardiomyocytes of non-failing hearts. Using microscopic densitometry, immunosignals were significantly decreased in ventricular myocytes of bCMP hearts (168 +/- 5.3 v 118 +/- 8.6 arbitrary units, P < 0.05). Moreover, myoglobin was heterogeneously distributed in bCMP hearts, with single myocytes showing no staining. Slot blot analysis of total RNA demonstrated a 40-50% reduction (P < 0.05) of myoglobin mRNA levels in ventricular but not in atrial myocardium of bCMP hearts. The results support the view that a decrease of myocardial myoglobin is a general phenomenon in end-stage heart failure. It appears to be primarily due to reduced gene expression but may be aggravated by leaking from single myocytes. The decrease of myoglobin may contribute to the imbalance between energy production and energy expenditure in heart failure.

Animals↗

PubMed1984

Variations in serum myoglobin after a 2-min isokinetic exercise test and the effects of training.

Serum-myoglobin was measured after the completion of three different types of exercise i.e., dynamic, isometric, and isokinetic. The maximal rises in serum-myoglobin levels were 20%, 70%, and 300%, respectively. On the basis of this finding a 2-min isokinetic test was developed and standardized for the purpose of studying conditions in vivo that may affect myoglobin leakage from skeletal muscle cells. Fourteen healthy men performed the 2-min isokinetic test. Blood lactate increased on average eight times with maximal levels obtained 4 min after completed work. S-Myoglobin levels obtained 4 min after completed work. S-Myoglobin was raised approximately five times after 2 h. The rise in S-myoglobin was significantly (P less than 0.01) related to the loss in muscle strength (torque decline) during the test. After a training period of 3 weeks comprising 4 min of maximal isokinetic exercise three times a week the rise in S-myoglobin after a 2-min isokinetic test was reduced from on average 240 micrograms X 1(-1) to 96 micrograms X 1(-1) (P less than 0.001). The rise in blood lactate was not related to the variations in S-myoglobin or affected by training. The 2-min isokinetic exercise test is an easily standardized exercise test which in combination with measurements of serum-myoglobin should prove valuable in the study of conditions affecting leakage from muscle cells.

Adenosine Triphosphate↗

PubMed1992

Effects of amino acid substitutions outside an antigenic site on protein binding to monoclonal antibodies of predetermined specificity obtained by peptide immunization: demonstration with region 145-151 (antigenic site 5) of myoglobin.

Monoclonal antibodies of predetermined specificity were prepared by immunization with a free (i.e., without coupling to any protein carrier) synthetic peptide representing region 145-151 of sperm whale myoglobin (SpMb) and their cross-reactions with eight Mb variants were determined. Five Mbs--bottle-nose dolphin myoglobin (BdMb), pacific common dolphin myoglobin (PdMb), horse myoglobin (HsMb), dog myoglobin (DgMb), and badger myoglobin (BgMb)--have an identical sequence in that region. Nevertheless, these Mbs exhibited very different cross-reactivities. BdMb and PdMb exhibited cross-activities which were comparable to that of the reference antigen, SpMb; while the reactivity of HsMb was remarkedly decreased, DgMb and BgMb showed almost no cross-reactions with these mAbs. Since the region 145-151 has an identical sequence in all the five Mbs, it is concluded that the differences in their antigenic reactivities with anti-region 145-151 mAbs are due to the effects of amino acid substitutions outside the region 145-151. Another pair of myoglobins, echidna myoglobin (EdMb) and chicken myoglobin (ChMb), have the same sequence in that region, but reacted very differently with anti-region 145-151 mAbs. The reactivity and affinity of EdMb were substantially decreased while those of ChMb were almost completely absent, relative to SpMb. It is concluded, contrary to popular assumptions, that when an amino acid substitution influences the binding of a protein variant to a mAb, it is not necessary for that substitution to be an actual contact residue (i.e., a residue within the antigenic site where the mAb binds). Such effects, which are often very drastic, could be due to indirect influences of the substitution on the chemical and binding properties of the site residues. Furthermore, residues which had been postulated, on the basis of these assumptions, to constitute discontinuous antigenic sites in SpMb, were found [from the present studies and those recently reported with mAbs against the other four antigenic site of Mb (regions 15-22, 56-62, 94-100, and 113-120 of SpMb)] to merely be exerting indirect effects on the known five antigenic sites of Mb. The effects of substitutions, which can happen even in the absence of conformational changes, are determined by many factors, such as the chemical nature of the substitution, its environment, its distance from the site, and the nature of the site residue(s) being affected.

Amino Acid Sequence↗

PubMed1977

Serum myoglobin in myocardial infarction: the "staccato phenomenon." Is acute myocardial infarction in man an intermittent event?

When serum was sampled frequently and soon after acute myocardial infarction, myoglobinemia was extremely common, occurring in 12 of 13 selected patients. Myoglobin first appeared in the serum within a few hours after infarction, but not consistently earlier than creatine phosphokinase. The peak level of serum myoglobin was reached appreciably earlier than the peak values of serum creatine phosphokinase activity. Time of earliest myoglobin appearance in the serum, peak level of myoglobin measured, and duration of detectable myoglobin release all correlated poorly with clinical and biochemical estimates of severity of myocardial infarction. There was no correlation between myoglobin levels and infarct size as estimated from creatine phosphokinase kinetics. Myoglobin appeared in the serum in multiple short "staccato" bursts, or episodes, often lasting only one to two hours. The hypothesis is suggested that the pattern of myoglobin appearance is a reflection of the episodic nature of acute myocardial infarction. Although isolated myoglobin determination may not be useful at present, for quantification of total myocardial damage, its pattern of release may be a sensitive marker for studying the time course of infarction, and may be useful to evaluate therapeutic interventions designed to interrupt an ongoing syndrome of myocardial necrosis.

Acute Disease↗

PubMed1976

Infrared magnetic circular dichroism of myoglobin derivatives.

By use of a newly constructed CD instrument, infrared magnetic circular dichroism (MCD) spectra were observed for various myoglobin derivatives. The ferric high spin myoglobin derivatives such as fluoride, water and hydroxide complexes, commonly exhibited the MCD spectra consisting of positive A terms. Therefore, the results reinforced the assignment that the infrared band is the charge transfer transition to the degenerate excited state (eg (dpi)). Since the fraction of A term estimated was approximately 80% for myoglobin fluoride and approximately 35% for myoglobin water, the effective symmetry for myoglobin fluoride is determined to be as close as D4h, while that for myoglobin water seems to have lower symmetry components. The ferric low spin derivatives such as myoglobin cyanide, myoglobin imidazole and myoglobin azide showed positive MCD spectra which are very similar to the electronic absorption spectra. These MCD spectra were assigned to the charge transfer transitions from porphyrin pi to iron d orbitals on the ground that they were observed only for the ferric low spin groups and insensitive to the axial ligands. The lack of temperature dependence in the MCD magnitude indicated that the MCD spectra are attributable to the Faraday B terms. Deoxymyoglobin, the ferrous high spin derivative, had fairly strong positive MCD around 760 nm with an anisotropy factor (delta epsilon/epsilon) of 1.4-10(-4). It shows some small MCD bands from 800 to 1800 nm. Among the ferrous low spin derivatives, carbonmonoxymyoglobin did not give any observable MCD in the infrared region while oxymyoglobin seemed to have significant MCD in the range from 700 to 1000 nm.

Animals↗

PubMed1978

Oxygenation and EPR spectral properties of Aplysia myoglobins containing cobaltous porphyrins.

Cobalt myoglobins (Aplysia) have been reconstituted from apo-myoglobin (Aplysia) and proto-, meso-, and deutero-cobalt porphyrins. Each of them showed the 30--60 times lower oxygen affinity than those of the corresponding cobalt myoglobins (Sperm whale). Kinetic investigation of their oxygenation by the temperature-junp relaxation technique showed that the low oxygen affinity of cobalt myoglobin (Aplysia) is due to a large dissociation rate constant. the electron paramagnetic resonance (EPR) spectrum of oxy cobalt myoglobin (Aplysia) is affected by the replacement of H2O with D2O, suggesting a possible interaction between the bound oxygen and the neighboring hydrogen atom. A low temperature photodissociation study showed that the product of photolysis of oxy cobalt myoglobin (Aplysia) gives an EPR spectrum different from that of the deoxy-cobalt myoglobin (Aplysia) and from that of the photolysed form of oxy-cobalt myogloin (Sperm whale). These observations suggest that in oxy-cobalt myoglobin (Aplysia) the bound oxygen might interact with amino acid adjacent to it, but the interaction is weaker than that in oxy cobalt myoglobin (Sperm whale).

Animals↗

PubMed1996

Serial myoglobin quantitation in the early assessment of myocardial damage: a clinical study.

OBJECTIVES: (a) To evaluate serial serum myoglobin pattern as an early marker of myocardial damage and compare it to conventional enzyme markers, and (b) to test the hypothesis that a patient admitted within 6 h of the onset of chest pain who has normal myoglobin concentrations that do not increase significantly in the first 2 h has not suffered a myocardial infarction (MI). DESIGN AND METHODS: A clinical study was conducted including 98 patients (62 males, 36 females) who presented to our Emergency Department with a diagnosis of possible MI. Patients with chest discomfort were selected to participate in the trial if their ECG was equivocal, their diagnosis was not obvious, and their treatment in hospital was to be the same as a MI patient until proven otherwise. Myoglobin measurements were made on admission and at 1 and 2 h thereafter. Quantitative myoglobin assays were performed by fluorometric enzyme immunoassay (STRATUS). Traditional cardiac enzymes were also measured. RESULTS: The myoglobin assay had good precision with CVs less than 10%. The sensitivity and specificity for MI of the myoglobin assay were 0.77 and 1.00 at 1 h and 0.93 and 1.00 at 2 h, respectively. Of positive diagnoses, 90% were clear 1 h after admission. Serial myoglobin assays provided better predictive efficiency (0.96) than baseline ECG (0.70) or CK-MB (0.62) in the admission assessment of possible MI patients. CONCLUSIONS: Negative myoglobin serial assays can be used effectively to rule out MI. Positive myoglobin serial assays help in the early diagnosis of MI in uncomplicated patients.

Adult↗