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A biophysical model for calculating the effective parameters of low-frequency magnetic fields was developed by Lednev based on summarized empirical data. According to this model, calcium ions as enzyme cofactors can be the primary target of low-frequency magnetic fields with different parameters tuned to calcium resonance. However, the effects of calcium-resonant combinations of static and alternating magnetic fields that correspond to Lednev's model and differ by order in frequency and intensity were not studied. It does not allow for confidently discussing the primary targets of low-frequency magnetic fields in terms of the magnetic influence on ions-enzyme cofactors. To clarify this issue, we examined the response of freshwater crustaceans Daphnia magna to the impact of combinations of magnetic fields targeted to calcium ions in enzymes according to Lednev's model that differ in order of magnitude. Life-history traits and biochemical parameters were evaluated. Exposure of daphnids to both combinations of magnetic fields led to a long-term delay of the first brood release, an increase in the brood size, a decrease in the number of broods, and the period between broods. The amylolytic activity, proteolytic activity, and sucrase activity significantly decreased in whole-body homogenates of crustaceans in response to both combinations of magnetic fields. The similarity in the sets of revealed effects assumes that different magnetic fields tuned to calcium ions in biomolecules can affect the same primary molecular target. The results suggest that the low-frequency magnetic fields with parameters corresponding to Lednev's model of interaction between biological molecules and ions can remain effective with a significant decrease in the static magnetic background. [ABSTRACT FROM AUTHOR]

Sucrases can modify numerous carbohydrates, and short-chain oligosaccharides produced by the unique transfructosylation activity of levansucrases are promising candidates for the growing sugar substitute market. These compounds could counteract the increasing number of diseases associated with the consumption of high-calorie sugars. Thus, there is great interest in the characterization of novel levansucrases. The commonly used method for sucrase activity determination is to quantify d -glucose released in the sucrose-splitting reaction. This is usually done in a discontinuous mode, i.e., several samples taken from the sucrase reaction are applied to a separately performed d -glucose determination (e.g., GOPOD assay). Employing the newly isolated levansucrase LevS KK21 from Pseudomonas sp. KK21, the feasibility of a one-pot sucrase characterization was investigated by combining sucrase reaction and GOPOD-based d -glucose determination into a single, continuous assay (Real-time GOPOD). The enzyme was characterized with respect to kinetic parameters, ion dependency, pH value, and reaction temperature in a comparative approach employing Real-time GOPOD and HPLC. High data consistency for all investigated enzyme parameters demonstrated that current processes for sucrase characterization can be considerably accelerated by the continuous assay while maintaining data validity. However, the assay was not applicable at acidic pH, as decolorization of the quinoneimine dye formed during the GOPOD reaction was observed. Overall, the study presents valuable data on the potentials of real-time sucrase activity assessment for an accelerated discovery and characterization of interesting enzymes such as the hereby introduced levansucrase LevS KK21. Progress in sucrase discovery will finally foster the development of health-promoting sucrose substitutes. [Display omitted] • A novel levansucrase (LevS KK21) from a sugar beet isolate was investigated. • To simplify sucrase characterization a new activity detection assay was developed. • Real-time GOPOD enables continuous assessment of sucrase activity in microplate format. • Real-time GOPOD is highly reliable, rapid, inexpensive, and high throughput-compatible. • Sucrase characterization and bioprocess monitoring are simplified by Real-time GOPOD. [ABSTRACT FROM AUTHOR]