Near-Infrared Spectroscopic Measurement of Myoglobin Oxygen Saturation in the Presence of Hemoglobin Using Partial Least-Squares Analysis

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Abstract
Myoglobin is an important intracellular protein found in cardiac and skeletal muscle. It is involved in the intracellular transport of oxygen from the cell membrane to the mitochondria where oxidative phosphorylation takes place. The optical absorbance characteristics of myoglobin are similar to those of hemoglobin in the near-infrared spectral region. Distinguishing spectral information of myoglobin from hemoglobin should allow for determination of intracellular oxygen availability in muscle. Partial least-squares analysis is used in this report to determine the oxygen saturation of myoglobin, in the presence of hemoglobin, in vitro. Studies were performed with the use of both transmission and reflectance spectroscopic techniques. Transmission spectra of myoglobin solutions were determined with varying degrees of oxygen saturation achieved by deoxygenating the solution using E. coli. Calibration spectral data sets were developed with the use of varying concentrations of hemoglobin interference, and with varying degrees of myoglobin oxygen saturation. Reflectance spectra were obtained from myoglobin and hemoglobin solutions containing a scattering agent to mimic muscle tissue conditions. Predicted myoglobin saturation values were within 2% of the known saturation values from the use of this analysis. Partial least-squares analysis allows for accurate prediction of myoglobin oxygen saturation in the presence of hemoglobin from either transmission of reflectance near-infrared spectra.