The effect of nail polish on pulse oximetry.

A randomized, blind study examined the effect of nail polish color on measurement of oxygen saturation by pulse oximetry. Fourteen adult volunteers had blue, green, purple, black, and red nail polish applied to their finger nails. A strip-chart recording of oxygen saturation (Nellcor N100) was made in room air and later interpreted in a blinded fashion. The absorption spectra of the five polishes were determined by spectrophotometry. The spectra of nine other nail polishes and three intravenous dyes also were examined. Black, blue, and green nail polish significantly lowered oximeter readings of oxygen saturation. Blue and green produced greater decreases than purple and red; black produced an intermediate decrease. Some but not all nail polishes absorbed light at the wavelengths used by the pulse oximeter (660 nm and 940 nm). The degree of artifactual desaturation correlated best with the difference between absorbance at 660 nm and absorbance at 940 nm (r = 0.95). Spectrophotometric absorbance data suggest that other colors may interfere with pulse oximetry. On the basis of spectrophotometric data, brown-red nail polish was predicted to interfere with oximetry; subsequent pulse oximetry measurements confirmed the prediction. Nail polish should be removed routinely before pulse oximetry monitoring.

Discrepancies among published amino acid sequences of soybean leghemoglobins: experimental evidence against cultivar differences as the sources of the discrepancies.

Despite discrepancies among charged amino acid residues in published amino acid sequences, isoelectric focusing experiments failed to detect varietal differences in soybean leghemoglobins a, c1, c2, or c3. Leghemoglobins from 69 domesticated soybean (Glycine max) cultivars and plant introductions and 18 wild soybean (Glycine soja) plant introductions were compared; the sources included soybean cultivars used by research groups in obtaining amino acid sequences and most of the ancestors of North American soybean cultivars. Thus, at least some of the discrepancies among published amino acid sequences of soybean leghemoglobins are due to sequencing difficulties rather than structural differences among the leghemoglobins used by different research groups.

Separation and determination of the relative concentrations of the homogeneous components of soybean leghemoglobin by isoelectric focusing.

The multiple components of soybean ferric leghemoglobin are readily separated by analytical and preparative flat bed isoelectric focusing in both the presence and also the absence of the ligand nicotinate. In the presence of nicotinate the separation by isoelectric focusing is more rapid and results in sharper bands of the very stable ferric leghemoglobin nicotinate complexes. The separation is sensitive enough to permit analytical experiments on leghemoglobin from single nodules. Leghemoglobins a and c1 prepared by ion exchange chromatography are homogeneous by isoelectric focusing criteria. Leghemoglobin c2 prepared by ion exchange chromatography is an approximately 1:2 mixture of leghemoglobins c2 and c3. Leghemoglobin d consists of three components. The ratio of leghemoglobin a to leghemoglobin c3 content increases dramatically as very young nodules mature. The increase in relative leghemoglobin a content suggests that leghemoglobin a might be required for regulation of nodule O2 concentration only when the nodule structure is complex. The ratio of leghemoglobin c1 content to leghemoglobin c3 content increases somewhat during the early period of nodule development, while the ratio of leghemoglobin c2 content to leghemoglobin c3 content increases slowly throughout nodule development. Ratios of leghemoglobin b content to leghemoglobin a content and of total leghemoglobin d content to total leghemoglobin c content were almost independent of nodule age. Leghemoglobins a and b might be related biosynthetically, as might leghemoglobins c and d.

CO and O2 complexes of soybean leghemoglobins: pH effects upon infrared and visible spectra. Comparisons with CO and O2 complexes of myoglobin and hemoglobin.

The effects of pH upon infrared spectra [CO stretching frequency (vco) region] and visible spectra of the CO complexes of soybean leghemoglobins a, c1, and c2, sperm whale myoglobin, and human hemoglobin A are reported. The vco for leghemoglobin--CO complexes was 1947.5 cm-1 at neutral pH. At acid pH myoglobin-- and hemoglobin--CO complexes developed vco bands at 1966--1968 cm-1, whereas leghemoglobin--CO complexes developed vco bands at approximately 1957 cm-1. All pKapp co values determined by pH-dependent variation of vco fell in the range 4.0--4.6. The pKapp co values determined from visible spectra were consistent with vco-determined values except for that of myoglobin--CO (visible pKapp co = 5.8). The pKapp co values in the 4.0--4.6 range appear to be pK values of the distal histidines, while the visible pKapp co of myoglobin--CO appears to be the pK of a group other than the distal and proximal histidines. The data are consistent with a model in which protonation of the distal histidine permits protein-free heme FeCO geometry in leghemoglobin--CO complexes but not in myoglobin-- or hemoglobin--CO complexes. Thus the heme pockets of leghemoglobins appear to be more flexible than the heme pockets of myoglobin and hemoglobin. The effects of pH upon visible spectra of the O2 complexes of soybean leghemoglobins a, c1, and c2, sperm whale myoglobin, and human hemoglobin A also are reported. pKapp o2 values of approximately 5.5 (leghemoglobins) and 4.4 (hemoglobin) are probably the pK values of the distal histidines. Comparisons of pKapp o2 values with pKapp co values indicate a more flexible heme pocket in leghemoglobins than in hemoglobin. The O2 complex of leghemoglobin c2 differed significantly from the O2 complexes of leghemoglobins a and c1 in visible spectra and titration behavior. These differences might be associated with the small structural differences in the region between the E and F helixes of leghemoglobins.

An infrared probe of iro n porphyrin oxidation state and axial ligation.

Carbonyl stretching frequencies of acyl groups conjugated with porphyrin rings are useful probes of the effective electronegativities of corrdinated iron atoms in iron porphyrins. Acetyl carbonyl stretching frequencies for 2,4-diacetyldeuteroporphyrin IX dimethyl ester derivatives exhibit both metal oxidation state and axial ligand effects. Infrared spectra of chloroform and pyridine solutions, corrected for solvation, showed the sequences of acetyl carbonyl stretching frequencies: dipyridine iron(II) less than mu-oxo bisiron(III) less than bromo iron(III) approximately equal to chloro iron(III) and dipyridine nickel(II) less than nickel(II). Applications of the probe to the study of hemeproteins are indicated.

Magnetic and spectroscopic probes for FeOFe linkages in hemin systems.

Magnetic and spectroscopic properties of mu-oxo-bis-hemins from natural and structurally related porphyrins were investigated as probes for ascertaining the presence or absence of FeIII-O-FeIII linkages between hemin moieties of hemeproteins. Magnetic susceptibilities of solids from 2.2 to 293 degrees K were investigated. The data fit the temperature variations expected for a pair of antiferromagnetically coupled S = 5/2, iron (III) porphyrins with J values of 175, 190, 195, 205, and 210 degrees K for deuterohemins with hydrogen, vinyl, 2'-ethoxycarbonylcyclopropyl, acetyl, propionyl, and ethyl 2,4-substituents, respectively. This magnetic character is reflected in PMR spectra that exhibit resonances with far less broadening and paramagnetic shift than is the case for monomeric high-spin hemins. Only impurities are seen in EPR spectra, which serve effectively in monitoring the magnetic purity of preparations. An infrared active asymmetric stretching frequency characteristic of the FeOFe linkage can be identified by substitution of 160 by 180. Electronic spectra are highly characteristic with poorly resolved absorption bands. The substituents on the porphyrin ring exert significant, but usually not large, electronic and steric effects on these properties. Solvent effects were relatively small and no firm evidence for binding of ligands trans to bridging oxygen was found. The uniqueness of these physical properties and their low sensitivity to changes in porphyrin structure or medium facilitates the identification of mu-oxo linkage in hemins or oxidized hemeproteins.