Indexed on: 01 Jun '07Published on: 01 Jun '07Published in: Biophysics
Absorption, fluorescence, and fluorescence excitation spectra in UV and visible regions are studied for alpha-1-microglobulin preparations isolated from human urine by gel chromatography and immunoaffinity chromatography with charcoal adsorption. The possible nature of low-molecular-weight compounds that impart yellow-brown color to alpha-1-microglobulin preparations and their role in the stabilization of the structure of protein globule is discussed. The effect of urea (1–10 M) and guanidine hydrochloride (0.25–6 M) on the conformational state and fast internal dynamics of alpha-1-microglobulin is studied by tryptophan fluorescence. The unfolding of the protein under the action of denaturants is attended with pronounced activation of its nanosecond internal dynamics. Alpha-1-microglobulin can regain the initial conformation and internal dynamics typical of native protein after denaturation unfolding of the globule with 10 M urea or 6 M guanidine hydrochloride. Alpha-1-microglobulin isolated by gel chromatography can exist in a partially folded thermodynamically stable state in 4–6 M urea.