Showing papers on "Myoglobin published in 1978"

Role of iron in bacterial infection.

Abstract: Iron is essential for most living things. The importance of the metal lies in its remarkable capacity to engage in electron transport reactions in biological systems (Neilands, 1974). From the point of view of infection, a clear distinction must be made between the quantity of iron present in body fluids and its availability to bacteria. In the living body, iron is not freely available. The bulk of the metal is locked up in ferritin, hemosiderin, myoglobin, and in the hemoglobin in red cells (Lanzkowsky, 1976). The iron-binding proteins, transferrin and lactoferrin, which possess only a minute fraction of the total body iron, are normally only partly saturated with Fe and have an exceptionally high association constant of about 1036 for the metal. This means that the amount of free iron in equilibrium with these proteins is only about 10−8 M, which is far too low for normal bacterial growth. To obtain Fe from normal tissue, bacteria must therefore possess iron chelating agents with association constants similar to those of transferrin and lactoferrin. In injured or dead tissue the situtation may be very different. For example, the lysis of red cells can provide large amounts of Fe for those bacteria that can assimilate heme compounds.

Oxygen binding to cobalt porphyrins

Abstract: The thermodynamic constants of oxygen binding to cobalt "picket fence" porphyrin complexes, meso-tetra(a,o,a,o- o-pivalamidophenyl)porphyrinatocobalt(II)- 1 -methylimidazole and 1,2-dimethylimidazole, are reported. In contrast to pre- viously studied cobalt porphyrins, these complexes bind oxygen with the same affinity as cobalt substituted myoglobin and he- moglobin. Solvation effects are discussed as the source of this difference. The use of sterically hindered axial bases as models of T state hemoglobin is discussed. In studies of myoglobin (Mb) and hemoglobin (Hb), the replacement of the neutral iron porphyrin prosthetic group with different metalloporphyrins has proved to be a useful tech- nique.2 Artificial hemoglobins containing ~inc,~.~ manga- ne~e,~-* ~opper,~ and nickel9 have been reconstituted, and their properties compared with those of the native iron proteins. These artificial systems, however, are incapable of reversible oxygenation. In contrast, cobalt substituted hemoglobin and myoglobin (CoHb and CoMb)l0 are functional,I1-l3 although their oxygen affinities are 10-100 times less than those of native Hb and Mb. CoHb exhibits cooperativity in oxygen binding, though to a lesser degree than Hb. The extent of this cooperativity is conveniently expressed as AG;, , the free energy difference between the intrinsic binding of the first and the fourth 02 to Hb.13b,c For CoHb, AG:l is roughly one-third that of Hb under comparable condition^.'^^ Because of the different stereo- chemical and electronic factors involved in binding oxygen to a cobalt porphyrin, the observation of cooperativity in CoHb has been variously used either to que~tion~9~~J~ or s~pport'~~,'~ the elegant proposal of Perutz concerning the molecular mechanism of cooperativity in natural Hb.16 At the heart of this proposal is the assumption, based on earlier ideas of Hoard" and Williams,18 that the high-spin iron in the unli- gated, low 02 affinity form of Hb (T state) lies out of the porphyrin plane, and that on binding 02, the iron becomes low spin and moves into the plane. The resulting motion of the proximal imidazole (0.6 A) then causes conformational changes in the protein which produce a higher 02 affinity quaternary form of the protein (R state). In the deoxy form of coboglobin, cobalt is low spin rather than high spin and the best estimates from simple cobalt model systems indicate that the proximal imidazole in CoHb moves -0.4 A upon oxygen- ation'4,'9,20 as opposed to the 0.6 8, for Hb. The resulting motion of the proximal histidine upon binding 02 will therefore only be two-thirds as great. This seems to be qualitatively consistent with the lowered AGil of CoHb.

Structure of oxymyoglobin

Abstract: MYOGLOBIN (Mb) consists of a single polypeptide chain of 153 residues and one haem. It combines reversibly with molecular oxygen which it takes up from the blood and passes on to mitochondria in muscle. In vivo its iron atom remains ferrous, but in vitro it autoxidises to the ferric metmyoglobin (metmb) in which the sixth ligand at the iron is water. Metmb of sperm whale was the first protein structure to be determined1. Takano recently determined the closely related structure of deoxymb by X-ray analysis, while that of COmb has been determined by neutron diffraction (refs 2, 3 and B. P. Schoenborn, personal communication). The most interesting structure, that of oxymb, has proved elusive. Watson and Nobbs tried to determine it by rapid crystallisation and collection of X-ray data at 4 °C, but even so autoxidation obscured the results4. Recent advances in low temperature techniques encouraged me to try again, especially in view of the wide interest in the nature of the iron–oxygen bond5–7.

Binding of carbon monoxide to isolated hemoglobin chains.

Abstract: Binding of carbon monoxide to the separated alpha and beta chains of hemoglobin, with and without bound p-mercuribenzoate, has been measured at temperatures from 5 to 340 K for times 2 mus to 1 ks using flash photolysis. All four proteins exhibit three different rebinding processes. The data are interpreted by a model in which the carbon monoxide, moving from the solvent to the binding site at the ferrous heme iron, encounters three barriers. The temperature dependences of the three processes yield activation enthalpies and entropies for the three barriers for all four proteins. Binding at temperatures below about 200 K is nonexponential, implying that the innermost barrier has a distribution of activation enthalpies. The distributions for the four proteins have been determined. At temperatures below 30 K, the CO binding rates approach finite low-temperature limits; binding thus proceeds by quantum-mechanical tunneling. Invoking a simple model, the widths of the innermost barriers are extracted from the measured tunneling rates. The experimental parameters are correlated with structural features of the hemoglobin chains and compared with previously published data on myoglobin and protoheme. A correlation is established between the height of the innermost barrier and the equilibrium CO pressure.

Model compounds for the T state of hemoglobin.

Abstract: O2 binding to a series of ferrous and cobaltous "picket fence" porphyrins is reported N-Methylimidazole and covalently attached imidazoles gives O2 binding to ferrous porphyrins with deltaH degrees =-162 kcal/mol (-677 kJ/mol) and deltaS degrees =-40 eu (standard state, 1 atmosphere O2) Similar studies with cobaltous porphyrins yield deltaH degrees =- 128 kcal/mol (-535 kJ/mol) and deltaS degrees =- 39 eu These values match well those of myoglobin and isolated subunits of hemoglobin and their cobalt reconstituted analogues 1,2-Dimethylimidazole has been successfully used to mimic the presumed restraint of T state hemoglobin In direct analogy to the decreased cooperativity shown by cobalt-substituted hemoglobin, model cobalt porphyrins show a smaller decrease in O2 affinity than the analogous iron porphyrins when the axial base is hindered Thermodynamic data are presented The molecular mechanism of cooperativity in hemoglobin is discussed

[50] Physical methods for the study of myoglobin

Abstract: Publisher Summary This chapter outlines the methods of isolation and characterization of myoglobins, spectral properties in different heme ligand states, titration and stability properties, oxygen binding equilibrium, and analysis of dynamic phenomena related to myoglobins. The full interpretation of the dynamic processes requires close analysis of the properties of myoglobins from related species to correlate both functional and evolutionary relationships with other carriers and enzymes in the oxidative pathway of muscle. Myoglobins are isolated from skeletal muscle, and sometimes from heart muscle, of a considerable number of animal species. The close structural similarity to the individual hemoglobin chains in the characteristic globin fold has served to maintain the focus of attention on this protein. Similar to hemoglobin, myoglobin was early recognized to have structural similarities among species and has contributed to the important concepts of the preservation of secondary structure in protein evolution and the development of functional domains.

Time-Resolved Resonance Raman Spectroscopy of Hemoglobin Derivatives: Heme Structure Changes in 7 Nanoseconds

Abstract: Resonance Raman spectra of oxyhemoglobin, deoxyhemoglobin, carboxyhemoglobin, and the corresponding myoglobin derivatives have been obtained with 7-nanosecond laser pulses at 531.8 nanometers. The results suggest that no transient constraint of the heme group by the globin structure occurs on this time scale, and thus establish a temporal sequence for the early events that may participate in the stereochemical trigger mechanism of hemoglobin cooperativity.

Iron availability from meat.

Abstract: 1. The distribution of radioactive iron in 59Fe-labelled rat muscle extract was determined using gel filtration. This showed that most (approximately 70%) of the radioactivity was associated with the heamatin compounds; myoglobin and haemoglobin. 2. Raw beef and freeze-dried rat muscle were digested in vitro, under simulated physiological conditions, and after centrifugation the supernatants fractionated by gel filtration. The soluble products were haematin Fe complexes of molecular weight above 10,000 and non-haematin Fe compounds of molecular weight below 6000, the major products being the non-haematin Fe complexes. The soluble compounds were also separated by dialysis and, in rat muscle, it was found that the low-molecular-weight non-haematin compounds accounted for more than 80% of the total soluble iron. 3. In vivo absorption studies with rats showed the Fe in a digested muscle dialysate to be more readily absorbed than that from an aqueous muscle extract which itself was more readily absorbed than the Fe from whole blood. 4. It may not, therefore, be the haemoproteins per se which are responsible for the high availability of Fe in meat, but rather the nature of their degradation products, formed by digestion within the meat environment.

Myoglobin, creatine kinase and its isoenzyme MB in serum after acute myocardial infarction.

Abstract: Serum creatine kinase, creatine kinase MB and myoglobin were determined in patients suffering from acute myocardial infarction (AMI) with shorter duration of symptoms than 6 h. At admission 83% had increased concentrations of myoglobin while 28% had creatine-kinase value above the reference limit. After onset of symptoms peak levels were found after 9.4 h (myoglobin) and 23.0 h (creatine kinase). Maximal levels of myoglobin and creatine kinase divided by upper reference limits correlated and were approximately of the same sensitivity. Compared to myoglobin, there was no difference in behavior between creatine kinase and its isoenzyme. In conclusion the study demonstrates myoglobin to be an early and sensitive indication of AMI.

Device and method for detecting myoglobin

Abstract: A test device and method for detecting myoglobin in the presence of hemoglobin in a fluid test sample. The test device comprises a chromatographic medium incorporating serum, haptoglobin and/or antiserum which binds or retards hemoglobin while permitting myoglobin to traverse the length of the test device. A test sample of body fluid is placed in contact with an appropriate portion of the chromatographic medium of said test device; hemoglobin in the body fluid is retained or retarded by the serum, haptoglobin and/or antiserum; and myoglobin in the sample traverses the length of the medium and contacts reagent means at a predetermined location thereon, resulting in a detectable response thereat.

Radioimmunoassay for human myoglobin. Initial experience in patients with coronary heart disease.

Abstract: A radioimmunoassay for human myoglobin has been used to study the serum myoglobin level in 13 normal individuals and 68 patients admitted to a Coronary Care Unit because of chest pain. Values in normal individuals ranged from 3 to 75 and averaged 25 +/- 23 (SD) ng/ml. Thirty-two patients with myocardial infarction initially examined within 12 hours of the onset of chest pain all showed clear-cut elevations in serum myoglobin, peak values ranging from 200 to 5500 and averaging 1368 +/- 1357 ng/ml. Seventeen patients with clinically atypical chest pain and no subsequent evidence of myocardial necrosis had myoglobin levels in the normal range, as did 11 of 19 patients with chest pain thought clinically to represent myocardial ischemia but no subsequent evidence of myocardial necrosis by conventional criteria. The final eight patients in the latter group showed mild elevations of serum Mb, peak values ranging from 102 to 280 and averaging 162 +/- 52 ng/ml; the basis for these elevations remains to be clarified.

Myoglobin function in the isolated fluorocarbon-perfused dog heart

Abstract: An isolated dog heart preparation perfused with hemoglobin-free fluorocarbon suspension has been developed to study the role of myoglobin in myocardial function. The coronary vasculature was perfus...

Factors affecting the autoxidation of lipids in mechanically deboned fish

Abstract: Hemoglobin, myoglobin, total heme pigments, and nonheme iron concentrations were measured in phosphate buffer (pH 7.1) extracts of mechanical and hand deboned mullet, Mugil cephalus, to determine the factors which induce a greater prooxidant activity in mechanically deboned fish. Mechanical deboning increased the hemoglobin and nonheme iron contents but had very little influence on the amount of myoglobin in the deboned fish flesh. Oxygen uptake studies using oleic acid as a substrate revealed that the hemoprotein content had an influence on the prooxidant activity of the buffer extracts of the deboned fish. Studies using purified myoglobin and hemoglobin as prooxidants indicated that myoglobin had a greater catalytic effect than hemoglobin on the oxidation of oleic acid. It was concluded that, in addition to the concentration of total heme pigments, the hemoglobin to myoglobin ratio should be considered when determining the influence of hemoproteins on the oxidative stability of deboned fish.