We investigate functional role of the P⁷⁶GTKMIFA⁸³ fragment of the primary structure of cytochrome c. Based on the data obtained by the analysis of informational structure (ANIS), we propose a model of functioning of cytochrome c. According to this model, conformational rearrangements of the P⁷⁶GTKMIFA⁸³ loop fragment have a significant effect on conformational mobility of the heme. It is suggested that the conformational mobility of cytochrome c heme is responsible for its optimal orientation with respect to electron donor and acceptor within ubiquinol–cytochrome c oxidoreductase (complex III) and cytochrome c oxidase (complex IV), respectively, thus, ensuring electron transfer from complex III to complex IV. To validate the model, we design several mutant variants of horse cytochrome c with multiple substitutions of amino acid residues in the P⁷⁶GTKMIFA⁸³ sequence that reduce its ability to undergo conformational rearrangements. With this, we study the succinate–cytochrome c reductase and cytochrome c oxidase activities of rat liver mitoplasts in the presence of mutant variants of cytochrome c. The electron transport activity of the mutant variants decreases to different extent. Resonance Raman spectroscopy (RRS) and surface-enhanced Raman spectroscopy (SERS) data demonstrate, that all mutant cytochromes possess heme with the higher degree of ruffling deformation, than that of the wild-type (WT) cytochrome c. The increase in the ruffled deformation of the heme of oxidized cytochromes correlated with the decrease in the electron transport rate of ubiquinol–cytochrome c reductase (complex III). Besides, all mutant cytochromes have lower mobility of the pyrrol rings and methine bridges, than WT cytochrome c. We show that a decrease in electron transport activity in the mutant variants correlates with conformational changes and reduced mobility of heme porphyrin. This points to a significant role of the P⁷⁶GTKMIFA⁸³ fragment in the electron transport function of cytochrome c.

The review briefly describes various types of infrared (IR) and Raman spectroscopy methods. At the beginning of the review, the basic concepts of biological methods of environmental monitoring, namely bioanalytical and biomonitoring methods, are briefly considered. The main part of the review describes the basic principles and concepts of vibration spectroscopy and microspectrophotometry, in particular IR spectroscopy, mid- and near-IR spectroscopy, IR microspectroscopy, Raman spectroscopy, resonance Raman spectroscopy, Surface-enhanced Raman spectroscopy, and Raman microscopy. Examples of the use of various methods of vibration spectroscopy for the study of biological samples, especially in the context of environmental monitoring, are given. Based on the described results, the authors conclude that the near-IR spectroscopy-based methods are the most convenient for environmental studies, and the relevance of the use of IR and Raman spectroscopy in environmental monitoring will increase with time.

With the laser interference microscopy (LIM) technique, one can measure phase height of cells—a variable proportional to the cell thickness and the difference in the refractive indices of the cell and the surrounding medium. This makes functional optical cell imaging possible, and estimation of shape, thickness, and area of erythrocytes feasible. In this paper, we studied changes in erythrocyte shape and volume with osmolarity and $p\text{H}$ . Obtained from the LIM technique, erythrocyte phase heights and area values, as well as the hematocrit-measured erythrocyte volume, were used to estimate changes in the refractive index with osmolarity and $p\text{H}$ . A comparison between the estimated refractive index with the refractive index, calculated in the assumption that it can only depend on the hemoglobin concentration in the cell, indicates that these two estimates are identical in the range of osmolarity (250–1000 mOsm) and $p\text{H}$ (4.5–10.0) values. Thus, refractive index changes result exclusively from the changes in hemoglobin concentration with the changes in erythrocyte volume. Under these conditions, it is possible to estimate the amount of hemoglobin in an erythrocyte from its phase height and area, obtained from LIM.