Borzova V.A. has completed her graduation from Moscow State University, Department of Biochemistry. She is 28 years old now and is working currently on her PhD thesis at A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Laboratory of Structural Biochemistry of Proteins, as a Research Scholar. She has published 4 papers in international journals with impact factor > 3.
Thermal aggregation of bovine serum albumin (BSA) was studied at fixed temperatures (60 °C, 65 °C, 70 °C and 80 °C) using dynamic light scattering (DLS), asymmetric-flow field flow fractionation and analytical ultracentrifugation (AUC). Thermal denaturation of the protein was characterized by differential scanning calorimetry. Analysis of the experimental data allowed us to propose the mechanism of thermal aggregation of BSA. Protein unfolding results in the formation of three forms of the non-native protein with different propensity to aggregation. Highly reactive form (Uhr) is characterized by a high rate of aggregation. Aggregation of Uhr leads to the formation of the primary aggregates. Lowly reactive form (Ulr) possesses a low ability for self-aggregation. The Ulr form is able to participate in the aggregation process by attachment to the primary aggregates produced by the Uhr form. Non-reactive form (Unr) remains in the non-aggregated state during prolonged heating. The Unr form was purified and characterized by fluorescent spectroscopy, AUC and DLS. Thermal aggregation of BSA was proposed as a test-system for quantification of the anti-aggregation activity of arginine and its derivatives. The dual effect of arginine derivatives on the initial rate of aggregation was observed. The determination of the order of aggregation with respect to the protein at 70 C shows that the rate-limiting state of the general process of BSA aggregation is the stage of aggregation of the denatured protein molecules. Thus, the observed effects of arginine and its derivatives demonstrate their direct action on the stage of aggregation.
Bronopol (2-bromo-2-nitropropane-1,3-diol) is an effective preservative employed in cosmetic formulations. However, under specific conditions, bronopol can decompose releasing low levels of formaldehyde and nitrites . These last compounds can react with any secondary amines or amides to produce significant levels of carcinogenic nitrosamines. The production of nitrosamines in cosmetic products has to be avoided. For this reason, although the use of bronopol is authorized in the current European Regulation, the maximum allowed concentration of bronopol in cosmetic products is 0.1%. Nevertheless, there is still no official method of analysis for the determination of this compound. The aim of this work is to propose a fast and simple analytical method to determine bronopol in cosmetic products. The proposed method is based on a vortex-assisted emulsification extraction, as one-step solution extraction process to prepare cosmetic samples, followed by liquid chromatography with spectrophotometric detection at 250 nm. The best results were achieved by using a C18 column at the following optimized conditions: Temperature, 40ºC; Flow rate, 0.5 mL min-1; Mobile phase, ethanol and a 1% acetic acid aqueous solution were used to perform the separation by elution gradient. Satisfactory results were obtained for the analysis of 19 cosmetic samples including creams, shampoos and bath gels, with good recoveries and repeatability. Limits of detection and quantification were at the low Bg mL−1 levels. These good analytical features, as well as its environmentally-friendly characteristics, make the presented method suitable for the determination of bronopol in cosmetic products.