Комбінація електрофоретичних систем для визначення фракційного складу протеїнів у препаратах лактоферину

The object of this study is three lactoferrin (LF) preparations used as bioactive supplements. The problem of determining the fractional composition of proteins in lactoferrin preparations was solved. The molecular weights of proteins in LF preparations have been determined by gel filtration on Sephadex G-25 and G-100. It was established that all three preparations contain proteins which molecular weights, including LF, are in the range from 5000 to 100000 Da. Low-molecular-weight (about 1000 Da) peptides were found in one preparation, which constitute 9 ± 3% of all protein impurities. Four different electrophoretic systems in polyacrylamide gel (PAG) were used to identify proteins in LF preparations. It was found that in order to detect whey protein fractions in preparations it is advisable to combine electrophoretic systems under native conditions with a disc electrophoresis system in the presence of sodium dodecylsulfate. Casein fractions can be detected by combining electrophoresis in the presence of urea and disc electrophoresis with SDS. Quantitative analysis of the relative content of impurity proteins was performed by the densitometry of PAG plates after disc electrophoresis in the presence of SDS. In the studied preparations (LF1, LF2, LF3), in addition to LF, β-lactoglobulin (β-Lg), blood serum albumin (BSA), and αS1-casein (αS1-CN) were detected. The relative content of these fractions from all proteins in the preparations is as follows: in LF1 – β-Lg (3 ± 0.4%), αS1-CN (< 1%), BSA (< 1%); in LF2 – β-Lg (3 ± 0.3%), αS1-CN (1 ± 0.2%), BSA (1 ± 0.3%) and in LF3 – β-Lg (3 ± 0.4%), αS1-CN (1 ± 0.2%), BSA (5 ± 0.6%). All the studied LF preparations differ in the content and ratio of protein fractions, which may indicate the need to analyze the protein composition of each batch of the preparation