Pyrene fluorescence titration

ATP and GTP as compared to other nucleotides, whereas neghgible selectivity is found for 117 and 119. Compounds 116, 117, and 118 exhibited significant binding interactions with the fluorescent, water-soluble dye 8-hydroxyl-l,3,6-pyrene trisulfonate (HPTS) yielding a quenching of the fluorescence. Titration of the adducts with the nucleotides produces the displacement of the dye and the revival of the fluorescence. 

Fluorescence titrations (Fig. 13.12d,e) were subsequently carried out by adding small aliquots (5 jjlL, 17 mM, l lMeCN/H20) of various potential guests into a solution of pyrene-functionalized pillar-[5]arene(57.2 jxM, 1 1 MeCN/ H2O). The peak excitation X (355 nm) was used, and the fluorescence intensity was monitored at the peak mission X (395 nm). The association constant between the guests and pyrene-functionalized pillar-[5]arene was calculated using the software Dynafit [106], which is based on nonlinear least-sqnaies regression analysis. 

The fluorescence titrations of 140( =3)-145( =8) and 146(pyrene) (1-0 x 10 mol dm ) with different saccharides were carried out in a pH 8.21 aqueous methanolic buffer solution, as described above (see page 86). The fluorescence intensity of sensors 140( =3)-145( =g) and 146(pyrene) increased with increasing saccharide concentration. The observed stability eonstants (.Kobs) of PET sensors 140( =3)-145( =g) and 146(pyrene) were ealeulated by fitting the emission intensity at 397 nm V5. saccharide concentration and are given in Table 3. 

Fig. 58a and b. Titration of P-448 with pyrene 159). The indicated amounts of pyrene were added to 1.92 pM P-448 in 0.3 M potassium phosphate buffer, pH 7.25, containing 20% glycerol. CD spectra and fluorescence emission spectra with excitation at 335 nm were measured. 

Fig. 10.3 (a) Direct titration of a fluorescent RNP complex (0.1 pM) of the A28 RNA subunit and a Rev peptide modified with pyrene at the amino terminal (Pyr-Rev) with ATP (1,3, 10, 30, 100, 300, 1,000, and 3,000 iM) shows an increase in fluorescence intensity. A spectrum in the absence of ATP is shown in bold line, (b) A saturation curve for the fluorescence emission intensity of A28/Pyr-Rev to ATP (open circles), UTP (filled squares), CTP (filled triangles), or GTP (filled circles) indicates A28/Pyr-Rev responds selectively to the addition of ATP... 

The fluoreseence titrations of sensor 147(phenanthrene pyrene) (2.5 X 10 mol dm , Xex=299 nm for phenanthrene and Xex=342 nm for pyrene) with different saccharides were carried out in a pH 8.21 aqueous methanolic buffer, as described above (page 86). Absorption V5. concentration plots of sensor 147(phenanthrene pyrene) and the monoboronic add reference compounds 146(pyrene) and 153(phenanthiene) Confirmed that the Jt-Jt stacking of sensor 147(piienanthrene pyrene) was solely iotramolecular. The fluorescence intensity of sensor 147(phenanthrene pyrene) at 417 nm increased with added saccharide when excited at both 299 and 342 nm, while the excimer emission at 460 nm decreased with added saccharide. The change in excimer emission indicates that the Jt-Jt interaction between phenanthrene and pyrene is disrupted on saccharide binding. 

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