Micro-Raman spectroscopy study on the allosteric regulation of inositol hexakisphosphate on hemoglobin

Abstract

Inositol hexakisphosphate (IHP) is an important allosteric factor, which could affect the quaternary conformational equilibrium of hemoglobin (Hb) toward the T state. In this study, micro-Raman spectroscopy was used to analyze the Hb allosteric effect of IHP. Raman spectra of Hb by IHP of different molar ratios under different oxygen partial pressure (PO₂) levels were obtained; linear fits and peak values for the Raman intensity of Hb/IHP sodium salt of different ratios at 1357 cm⁻¹, 1377 cm⁻¹, 1545 cm⁻¹, 1585 cm⁻¹, 1606 cm⁻¹, and 1640 cm⁻¹ were analyzed. With the increase of molality of IHP sodium salt, the intensities and peak ratio values of 1357 cm⁻¹, 1545 cm⁻¹, and 1606 cm⁻¹ decreased while the intensities and peak ratio values of 1377 cm⁻¹, 1587 cm⁻¹ and 1640 cm⁻¹ obviously increased. There is a good linear relationship between the proportion of IHP sodium salt and its function of promoting the release of oxygen in oxygenated hemoglobin under 10, 20, and 30 mmHg, with the R² all more than 0.910. The results confirmed that the interactions of Hb with IHP could promote the release of oxygen in the oxygenated Hb, especially in lower PO₂ levels. It is promising that the results could provide a reference for allosteric regulation of IHP and other allosteric factors on hemoglobin oxygen affinity by Raman spectroscopy.