Thermostabilization of BSA in TMAO Water Mixtures by Infrared Spectroscopy

Abstract

Background: Trimethylamine-N-Oxide (TMAO) is a small organic molecule derived from the metabolism of L-carnitine and choline after ingestion of animal food. TMAO has many functions such as electron acceptor, an osmolyte, stabilizer of macromolecules folding. It seems that TMAO plays an important role in nature but, in humans, it is a remnant of the evolution of the osmolyte system. Objective: The present paper is addressed on the study of thermal stability of hydrated Bovine Serum Albumins (BSA) in the presence of water and TMAO water solution by means of InfraRed spectroscopy. In particular, this work has investigated the protein amide I spectral regions, which is sensitive to protein secondary structure, and the intramolecular OH stretching region. Methods: The analysis has been performed by different approaches, namely by evaluating the Thermal Spectral Distance (SDT), the spectral shift (Δω), the spectral Fractal Dimension (FD) and the Wavelet Cross Correlation temperature variation (ΔTCXWT). Results: The obtained results revealed for BSA in TMAO, in respect to BSA, smaller values of SDT, Δω, FD and ΔTCXWT. Furthermore, the SDT, Δω and ΔTCXWT temperature trends to follow sigmoid trends that have been modeled by means of logistic functions; in all the above three cases BSA in TMAO shows a higher value of the inflection point temperature. Conclusion: These results can be interpreted by hypothesizing that TMAO influences the hydrogen bond network of water. In particular, the strengthening of the network intermolecular O-H interactions reduces the protein dynamic fluctuations and in turn leads to the stabilization of the protein tertiary structure.