Investigation of effect of albumin aggregation on NMR relaxation in D2O solutions

This study was carried out to explain the effect of albumin aggregation to T1 and T2 relaxation times and mechanisms leading to relaxation. Existence of albumin aggregation was investigated in terms of Inversion Recovery (IR)-T1 FID 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. Albumin solutions for concentration studies were prepared in two groups by adding different amount of albumin to 1 ml D2O. In the first group, albumin was added as 0.02 g up to 0.1 g, while in the second group, it was added as 0.1 g up to 0.5 g. Measurements were performed by using a Bruker Avance 400 MHz NMR spectrometer. T1 measurements were conducted by Inversion Recovery method, whereas T2 measurements were carried out by Carr-Purcell-Meibon-Gill Method. FID and SE qatars of D2O exhibit a single exponential change, which has seen from FID, Echo sets and IR-T1, SE-T2 curves. On the other hand, when albumin was added, exponential appearance of FID and SE qatars changed, which shows that protein aggregation increases at high concentrations. Concentrations of up to 10 % of the samples of IR-FID, SE-T1 qatars and IR-T1 , SE-T2 curves fit perfectly with related formulas, which shows that T1, T2 experiments can be performed by using albumin up to % 10 concentrations. Signal decays after 20 % concentration on the 1/T1 ve 1/T2 curves become apparent, which shows that protein aggregation is very effective at 20 % and higher concentrations.