Time-Resolved Tryptophan Fluorescence as an Indicator of Alterations in Serum Proteins in Melancholic Depression

Abstract

Abstract—The goal of this work was to search for blood serum parameters that would be associated with the state of patients with mental disorders. Such indicators are needed for an objective assessment of this state versus the prevailing subjective evaluation methodologies. The kinetics of tryptophan fluorescence decay in the serum albumin fraction was compared in patients with melancholic depression (before treatment) and in healthy volunteers. Albumin fluorescence is mainly due to the tryptophan 214 residue, which is located in the immediate vicinity of the first drug-binding center of the molecule. The decay kinetics were described as a sum of three exponential functions with lifetimes τ_i (in the 6.5, 2.8 and 1.0 ns region) and the amplitudes A_i. The τ_i values were similar in both groups of individuals. In contrast, there was a significant difference between patients and controls in the A₁/A₃ amplitude ratio. It is suggested that the A₁/A₃ value can be considered as a potential marker indicating the presence or absence of melancholic depression in patients before treatment.