Infrared spectroscopy of biomolecules is one of the few methods, which combine a relatively simple measurements and a possibility of highly informative structural analysis. The most high-demand field of such investigations is the identification of various pathologies accompanied by changes in the biomolecular structure. In this study the comparative analysis of the secondary structure of blood serum proteins from patients with multiple myeloma and healthy donors was performed using infrared spectroscopy. There is a tendency for reduce the proportion of a-helices in the secondary structure of blood serum proteins in patients with multiple myeloma compared to healthy donors. Thus, infrared spectroscopy reveals difference in the secondary structure of blood serum proteins in patients with multiple myeloma and healthy donors.

A combination of high-resolution agarose gel protein electrophoresis, refractometric analysis, and infrared spectroscopy was applied to investigate the blood serum in patients with multiple myeloma (MM). Analysis of the FTIR spectra of the serum obtained from MM patients and healthy donors revealed a decreased amount of α-helixes and increased content of β-sheets in serum proteins from MM patients compared to healthy donors. These findings suggest an interaction between serum proteins and stabilization of the resulting complexes, accompanied by the formation of associated β-sheets.

The serum of patients with multiple myeloma was examined by refractometric methods before and after the course of antitumor therapy. It was found that the amount of protein in the serum of patients with multiple myeloma, determined by the value of the serum refractive index, tended to decrease after the course of treatment. The value of the refractive index of blood serum can be used as an additional criterion for assessing the dynamics of changes in blood-serum properties during antitumor therapy.

Subject of Research. Application of refractometric analysis in multiple myeloma diagnostics is proposed for the first time. Multiple myeloma (MM) is a disease of the hematopoietic system characterized by active monoclonal protein synthesis being detected in blood serum and/or in urine. Method. The essence of method consists in measuring of the sample refractive index. The value of refractive index depends on physicochemical characteristics of the optical mediums. Differences between refractive index of patients with multiple myeloma and donor blood serum connected with typical protein and electrolyte imbalance were researched. Main Results. Refractometric analysis data have shown strong correlations between protein concentrations in serum of patients with multiple myeloma and serumrefractive index. Refractive index of serum of patients with multiple myeloma firstly depends on protein concentration rather than on an electrolyte imbalance. The main tendency for patients with multiple myeloma is a higher level of both protein and electrolytes concentration in serum, in contrast to healthy people. Practical Relevance. According to the obtained data, refractometric analysis is considered as one of the suitable methodsfor express-diagnostics of diseases, in particular, multiple myeloma.