Microwave Patch Antenna-Based Dielectric Characterization of Protein Denaturation: Correlation With Established Analytical Techniques

The study of protein denaturation is essential for understanding the relationship between protein structure and function, with significant implications in biotechnology, pharmaceuticals, and food science. This work introduces a microwave-based technique for real-time measurement of the dielectric constant of protein samples utilizing the Maxwell-Garnett mixing formula to isolate protein permittivity from complex media. Proteins, such as insulin, hemoglobin, bovine serum albumin (BSA), and papain, were analyzed, revealing dielectric constants between 2.5 and 3.5. Our findings indicate insulin’s higher dielectric constant, attributed to its distribution of charged groups. The effects of denaturing agents (papain and urea) were evaluated, showing significant decreases in dielectric constants, corresponding to structural changes. These results were cross-validated using Fourier transform infrared (FTIR), UV-Vis spectroscopy, fluorescence microscopy, and molecular dynamics (MDs) simulations, providing complementary insights into molecular interactions and structural alterations induced by denaturation. Furthermore, sensitivity analysis demonstrated that the dielectric method was more responsive to denaturation compared to FTIR and UV-Vis, highlighting its superior detection capability. The novel microwave technique offers a rapid, noninvasive, and efficient approach for studying protein denaturation, with potential applications in diverse scientific and industrial fields.