Protein fluorescence decay of human serum with a very low density of lipoproteins exposed to synchrotron radiation

Abstract

Measurements of fluorescence decay of very low density lipoproteins (VLDL) excited by synchrotron radiation have been carried out with an excitation wavelength of 260±4 nm. Experimental curves of the fluorescence decay are well described by a biexponential law with τ₁ < 0.5 ns and τ₂ = 4.8 ns. The fast component is supposed to be responsible for tryptophane residues located near the surface of the lipoprotein particles (TRP-1) and the slow component for tryptophane residues in the hydrophobic environment (TRP-2). Analysis of the VLDL fluorescence quenching with the DSP-12 (the electron excitation energy acceptor) has demonstrated that the TRP-2 can either have entered the VLDL particle as deep as 2.4±0.2 nm or be located as far as 1.5±0.2 nm outside the particle.