Multi-wavelength thermal-lens spectrometry for high-accuracy measurements of absorptivities and quantum yields of photodegradation of a hemoprotein–lipid complex

Abstract

Accurate measurements of absorptivities and quantum yields of biochemical species under various conditions are an important task of applied photonics and analytical chemistry. In this work, we provide a comparison of the capabilities of thermal-lens spectrometry to measure these parameters of various samples. Measurements of relevant model substances, biologically active substituted 2-thiohydantoins and their complexes of copper(I,II) and heme proteins (forms of hemoglobin and cytochrome c), showed negligible differences in apparent molar absorptivities for thermal-lens spectrometry and optical-absorption (spectrophotometric) data. The values for tabletop and microscale thermal-lens measurements under batch conditions differ insignificantly. The precision of measurements of molar absorptivities by thermal-lens spectrometry is no less than in the case of spectrophotometry or the precision is even higher in the cases of low absorptivities. For cardiolipin–cytochrome c-NO complex, the difference between absorptivity values calculated from thermal-lens data and acquired by spectrophotometry is significant due to complex photodegradation. The quantum yield of its photolysis reaction calculated from optical absorption and thermal-lens data altogether at two wavelengths for 0.4–360 s of the reaction, 0.46 ± 0.04, was estimated.

Keywords

• Multispectral photothermal spectroscopy
• Thermal-lens spectrometry
• 2-thiohydantoins (2-thioxo-imidazolidin-4-ones)
• Cytochrome c
• Hemoglobin
• Absorptivity