Fluorescence lifetime distribution of folded and unfolded proteins

Abstract

Time-resolved fluorescence of single tryptophan proteins have demonstrated the complexity of protein dynamic and protein structure. In particular, for some single tryptophan proteins, their fluorescence decay is best described by a distribution of fluorescence lifetimes rather than one or two lifetimes. Such results have provided further confirmation that the protein system is one which fluctuates between a hierarchy of many conformational substates. With this scenario as a theoretical framework, the correlations between protein dynamic and structure are investigated by studying the time-resolved fluorescence and anisotropy decay of holo and apo human superoxide dismutase (HSOD) at different denaturant concentrations. As a function of guanidine hydrochloride (GdHCI), the width of the fluorescence lifetime distribution of HSOD displays a maximum which is not coincident with the fully denatured form of HSOD at 6.5M GdHCI. Furthermore, the width of the fluorescence lifetime distribution for the fully denatured forms of holo and apo HSOD is greater than that of the native forms.

Time‐resolved fluorescence studies on site‐directed mutants of human serum albumin

“…1). Gratton and coworkers [26–30]have demonstrated that the widths of the lifetime distributions recovered in the cases of single tryptophan proteins can be related to the extent of motion of the fluorophore, namely, decreasing as the rate of motion increases. Our observations show an increased rate of local mobility of Trp‐214 in FDH‐HSA and Met‐218 HSA over that of Trp‐214 in normal HSA and, hence, correlate well with the decreased widths of the recovered lifetime distributions for FDH‐HSA and Met‐218 HSA.…”

Synthesis, Characterization, Cytotoxic Activity, and Interactions with CT-DNA and BSA of Cationic Ruthenium(II) Complexes Containing Dppm and Quinoline Carboxylates

“…For fluorescence measurements, the BSA concentration was kept constant in all samples, while the complex concentration was increased from 3.125 to 150  μ M, and quenching of the emission intensity of the tryptophan residues of BSA at 320 nm (excitation wavelength 280 nm) was monitored at different temperatures (300 and 310 K). The experiments were carried out in triplicate and analyzed using the classical Stern-Volmer equation$\begin{array}{c}T1\frac{F_0}{F}=\mathrm{1}+k_q{\tau }_o\left[Q\right]=\mathrm{1}+K_{\mathrm{s}\mathrm{v}}\left[Q\right],\end{array}$where F 0 and F are the fluorescence intensities in the absence and presence of quencher, respectively, [ Q ] is the quencher concentration, and K sv is the Stern-Volmer quenching constant, which can be written as$\begin{array}{c}T1K_q=\frac{K_{\mathrm{s}\mathrm{v}}}{{\tau }_o},\end{array}$where K q is the biomolecular quenching rate constant and τ o is the average lifetime of the fluorophore in the absence of quencher (6.2 × 10 −9  s) [20]. Therefore, (2) was applied to determine K sv by linear regression of a plot of F 0 / F versus [ Q ].…”

Cytotoxicity of Ru(II) piano–stool complexes with chloroquine and chelating ligands against breast and lung tumor cells: Interactions with DNA and BSA

“…[Q] is the quencher concentration, and Ksv Stern-Volmer the quenching constant, which can be written as K q = K sv /τ o , where K q is the biomolecular quenching rate constant and τ o is the average lifetime of the fluorophore in the absence of quencher (6.2x10 -9 s) [26]. Therefore, Eq.…”