Biomedical subjects
L C Dickinson
Publications and source records attributed to L C Dickinson.
Electron paramagnetic resonance study of carp methemoglobin.
The g anisotropy of the EPR spectra of carp azidomethemoglobin is found to be pH-dependent, whereas, the spectra of human azidomethemoglobin are not. The two hemoglobins have the same g values at alkaline pH values. Crystal field analysis yielded values of 2.25 and 3.31, respectively, for the rhombic distortion, V/lambda, and the tetragonal distortion, delta/lambda. The spin orbit coupling constant is lambda. At pH 4.0 the values of V/lambda and delta/lambda for carp azidomethemoglobin became 1.95 and 4.76, respectively, whereas those for the human hemoglobin are virtually unchanged. The results are interpreted to mean an increase of out-ofplane displacement of the iron atom and stabilization of the T form of carp azidomethemoglobin by high proton concentration. At pH 6.0 and lower, the EPR spectra of carp azidomethemoglobin showed the presence of about 1.5% of high spin species, the amount is not affected by excess of either inositol hexaphosphate or sodium azide. The EPR spectra of aquo- and fluoroderivatives of carp methemoglobin were not affected by pH changes.
Nonequivalence of subunits in [15N]nitrosylhemoglobin Kansas. A single crystal electron paramagnetic resonance investigation.
EPR spectra of Hb15NO crystals of mutant Kansas (Asn G4(102) beta leads to Thr) have been recorded at every 5' intervals and in three orthogonal planes. The nitrosylhemes are nonequivalent for the alpha and beta subunits, their assignments are made possible by comparison with the powder EPR specrtra of Hb15NO of mutant Iwate (His F8(87)alpha leads to Tyr) (Trittelvitz, E., Gersonde, K., and Winterhalter, K.H. (1975) Eur. J. Biochem. 51, 33-42). The EPR parameters for the beta-nitrosylhemes of Hb Kansas are: gxx=2.094 gyy=2.031, gzz=2.00, Azetazeta=11 G, Azetazeta=32.5 G, Aetaeta=12.5 G; the Fe-N-O bond angle is about 105 degrees. The paramters for the alpha-nitrosyl hemes are: gxx=2.058, gyy=2.021, gzz=1.977, Azetazeta=24.5 G, Azetazeta less than or equal to 5G, Aetaeta=23 G; the Fe-N-O bond angle is about 167 degrees. Hyperfine splittings of 7 to 8 gauss with 14Nepsilon atom of His(F8) were observed for the beta-nitrosylhemes; none was resolved for the alpha-nitrosylhemes. The results were interpreted to mean that the tension on the iron of the beta subunits is not large in the unliganded state and this tension was not greatly increased by the binding of nitric oxide in the strongly bent configuration. The tension at the iron in the deoxyhemoglobin is dominant at the alpha subunits. Binding of nitric oxide in this case causing either the breaking or great weakening of the Fe-His(F8) bond. The nitrosyl is in a nearly linear configuration. The unpaired electron densities at the nitrogen atom of the bound nitric oxide is about 63% for the beta-nitrosylheme and 37% for the alpha-nitrosylhemes.
Metal replaced hemoproteins. A review with introductory laboratory preparation of cobaltmyoglobin.
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Cobalt-cytochrome c. I. Preparation, properties, and enzymic activity.
An improved procedure for the preparation of cobalt-cytochrome c has been developed. Various factors influencing the cobalt insertion process are discussed. The optical spectra of cobalt-cytochrome c suggest a six-coordinated species. The spectral shifts occurring with oxidation-reduction are compared with those observed for deoxy-cobaltohemoglobin and ferrocytochrome c and attributed to the effect of d(z2) electron on stereoelectronic interactions between the axial ligands and the porphyrin pi systems. Cobalt-cytochrome c has Em,7 = -140 +/- 20 mV as compared to an Em,7 of +250mV for ferrocytochrome c. An explanation for this negative Em,7 is offered. Cobaltocytochrome c is oxidized by cytochrome oxidase at about 45% of the rate for native cytochrome c. On the other hand cobalticytochrome c was not reduced by microsomal NADH or NADPH cytochrome c reductase nor by mitochondrial NADH or succinate cytochrome c reductase. It appears that the integrity of the reductase binding site is destroyed and the oxidase binding site has been modified by cobalt substitution.
Cobalt-cytochrome c. II. Magnetic resonance spectra and conformational transitions.
Between pH approximately 4 and 10 cobaltocytochrome c (Cocyt-c) gives an electron paramagnetic resonance (EPR) spectrum with g parallel = 2.035, g the perpendicular = 2.223, CoA PARALLEL = 61.4 G, CoA the perpendicular = 49.8 G, NA parallel = 15.3 G, and NA THE PERPENDICULAR = 12.5 G. Comparisons with the EPR spectra of deoxycobaltomyoglobin, deoxycobaltohemoglobin, and model compounds and together with other evidence showed cobaltocytochrome c to have Met-80 and His-18 as its axial ligands. The protons of these ligands are seen as resonances shifted by the ring-current field of the porphyrin in the 300-MHZ 1H nuclear magnetic resonance (NMR) spectra of cobalticytochrome c (Cocyt-c+). The methyl and gamma-methylene protons of Met-80 in this molecule occupy positions with respect to heme c which are somewhat different from those in ferrocytochrome c. The 1H NMR spectra also showed that the methyl groups of Leu-32, Ile-75, Thr-63, thioether bridges, and the porphyrin ring in the cobalt protein are in the same state as in native enzyme; the same is also true for Tyr-59, His-26, and His-33 and also possibly Tyr-67, Tyr-74, and Phe-82. Above pH 11, Cocyt-c is converted to a five-coordinated form having g parallel = 2.026, g the perpendicular = 2.325, CoA parallel = 80 G, CoA the perpendicular approximately 10 G, NA parallel = 17.5 G, and NA the perpendicular not resolved. Below pH 1.0 the EPR spectrum of Cocyt-c is also five-coordinated with g parallel = 2.014, g the perpendicular = 2.359, CoA parallel = 93.8 G, and CoA the perpendicular = 38.8 G. The axial ligands in the alkaline and the acidic forms of Cocyt-c are His-18 and Met-80, respectively. New prominent proton resonance peaks are observed in cobalt-cytochrome c which are either absent or weak in native cytochrome c. These are situated at 3.0, 1.7, and 1.44 ppm, attributable, respectively, to the epsilon-CH2, DELTA-CH2 + beta-CH2, and gamma-CH2 of lysyl residues in random-coil-peptides. From the areas of these peaks, it is estimated that one-two lysyl residues in Cocyt-c have been modified; four-five lysyl residues in Cocyt-c+ have been modified. These alterations of surface charged groups are probably responsible for the lowered reactivity of Cocyt-c with cytochrome oxidase and the lack of reactivity of Cocyt-c+ with several cytochrome reductase systems.
Electron transfer between hemoglobin and coboglobin mediated by methylene blue.
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Cobalt cytochrome c: enzymic assays.
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Electron paramagnetic resonance of single crystal 15N-nitrosyl-57Fe-myoglobin.
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Cobalt cytochrome C: preparation of characterization.
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Comparative biological chemistry of cobalt hemoglobin.
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Electron paramagnetic resonance of single crystal deoxycobaltohemoglobin.
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Electron paramagnetic resonance of single crystal oxycobaltmyoglobin and deoxycobaltmyoglobin.
Single crystals of oxycobaltmyoglobin and deoxycobaltmyoglobin have been prepared and found to be isomorphous. The paramagnetic resonance spectra of deoxycobaltmyoglobin yield g(xx) = 2.33(0), g(yy) = 2.32(3), g(zz) = 2.02(8) with the z-axis parallel to the "heme" normal. The A(Co) and g tensors share the same principal axes with|A(Co) parallel| = 79 G and|A(Co)[unk]| = 6 G. A value of A(N) = 17.5 G was also obtained for the epsilon-N atom of the F8 histidine. There are two paramagnetic species in oxycobaltmyoglobin having apparently identical g-tensors (gxixi = 2.08(3), getaeta = 2.00(6), and gzetazeta = 1.98(9)) but different A(Co)-tensors. Furthermore, g values A(Co) do not share the same principal axes. The A(Co)-values for one of the species are (A(xx) = 16.7 G, A(yy) = 5.95 G, A(zz) = 9.3 G), they are all 40% larger for the other species. The two species are oriented 90 degrees to each other in the crystal. The results from electron paramagnetic resonance studies are consistent with a pi-bounded structure for (Co)MbO(2).
Crystallization of reconstituted sperm whale myoglobins.
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An electron paramagnetic resonance study of nitrosylmyoglobin.
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Accuracy of recumbent height measurement.
Since many patients requiring specialized nutritional support are bedridden, measurement of height for purposes of nutritional assessment or prescription must often be done with the patient in bed. This study examined the accuracy of measuring body height in bed in the supine position. Two measurements were performed on 108 ambulatory inpatients: (1) standing height using a standard height-weight scale, and (2) bed height using a flexible tape. Patients were divided into four groups based on which of two researchers performed each of the two measurements. Each patient was also weighed and self-reported height, weight, sex, and age were recorded. Bed height was significantly longer than standing height by 3.68 cm, but the two measurements were equally precise. It was believed, however, that this 2% difference was probably not clinically significant in most circumstances. Bed height correlated highly with standing height (r = 0.95), and the regression equation was standing height = 13.82 +/- 0.09 bed height. Patients overestimated their heights. Heights recorded by nurses were more accurate when patients were measured than when asked about their heights, but the patients were more often asked than measured.
The effects of the rapid strep test on physician management of streptococcal pharyngitis.
Management of pharyngitis remains an important and controversial subject. A retrospective chart review at the University of South Alabama Family Practice Center was undertaken to assess changes in physician prescribing and testing patterns since the advent of rapid testing of streptococcal pharyngitis (rapid strep tests [RST]). Charts for study were identified by encounter form coding of a diagnosis of streptococcal pharyngitis or pharyngitis not otherwise specified. Control and test groups were formed based on the availability of the RST, and a stratified sample was drawn from each group. In the group of patients studied after the RST became available, data analysis showed a significantly increased likelihood that patients received antibiotics with a positive RST (odds ratio [OR] = 6.42), whereas those patients with a negative or no RST were significantly less likely to receive antibiotics (OR = 2.50 and 2.48, respectively). Group assignment was a significant predictor of test-ordering behavior (P less than 0.05). A higher than expected rate of streptococcal pharyngitis was noted in the group of patients who had the RST available to them. The RST plays an important though not fully defined role in the current management of pharyngitis.