Fluorescence intensity quenching of tyrosine residues by iodide

Fluorescence intensity quenching of tyrosine residues by iodide 

Fluorescence intensity quenching of tyrosine residues by iodide is analyzed with the Stem-Volmer formula 

The Stem-Volmer plots of the fluorescence quenching of the aminoteiminal residue in dermenkephalin and [L-Met ] deimenkephalin by iodide ai e shown in Fig. 5.13. Fluorescence of Tyr in (L-Met ] DREK and that of free L-tyrosine are quenched identically by iodide (Ksv = 19.817 0.025 and 19.298 0.030 M for L-tyrosine and [L-Met ] DREK), respectively (Fig. 5.13a and b). Since iodide quenches tyrosine residue fluorescence within a spatial proximity, the similar values found for Ksv indicates the absence of any matrix siuTounding the tyrosyl side chain. By contrast, the dynamic constant is lower for DREK (Ksv = 13.37 0.02 M (Fig. 5.13c.). 

In the presence of 6 M guanidine, difflision of iodide was foiuid homogeneous for the 

Ksv characterizes the accessibility of the fluorophore to the quencher while the bimolecular quenching constant kq characterize the diffusion properties of the quencher. 

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