Investigation of the Effects of Albumin Aggregation in D2O Solutions on NMR Relaxation Times

This study was conducted in order to reveal the effects of protein aggregation on T1 and T2 relaxation times and to clarify the mechanisms leading to relaxation. The presence of protein aggregation was examined in terms of Inversion Recovery (IR)-T1 signals, Spin Echo (SE) - T2 signals and decay curves. In the experiment, Human serum albumin and Deuterium Oxide (D2O) solvent, which includes 0, 1 % residual water, were used. The albumin solutions used for the analysis of concentration were prepared in two groups by adding different amounts of albumin to 1 ml of D2O. The measurements were performed by using Bruker Avance 400 MHz NMR spectrometer. T1 measurements were carried out with the Inversion Recovery method and T2 measurements were carried out with the Carr-Purcell-Meibon-Gill method. With the acquisition of FID and Echo sets and of IR-T1 and SE-T2 curves, it was observed that FID and SE sets were changed as a single exponential. However, as protein was added, the exponential appearance of the FID and SE sets was changed. This presents that the protein aggregation begins to increase in advanced concentrations. IR-FID and SE-FID sets of the samples that are up to 10 % concentration and IR-T1 and SE-T2 curves fit perfectly with the related formulas. This shows that NMR T1, T2 measurements can be performed by using albumin up to 10 % of concentration.