Pressure effect on the nonradiative process of thioflavin-T.

The journal of physical chemistry. A (2011-05-19)
Nadav Amdursky, Rinat Gepshtein, Yuval Erez, Naum Koifman, Dan Huppert
ABSTRACT

Time-resolved emission techniques were employed to study the nonradiative process of thioflavin-T (ThT) in 1-propanol, 1-butanol, and 1-pentanol as a function of the hydrostatic pressure. Elevated hydrostatic pressure increases the alcohol viscosity, which in turn strongly influences the nonradiative rate of ThT. A diamond-anvil cell was used to increase the pressure up to 2.4 GPa. We found that the nonradiative rate constant, k(nr), decreases with pressure. We further found a remarkable linear correlation between a decrease in k(nr) (increase in the nonradiative lifetime, τ(nr)) and an increase in the solvent viscosity. The viscosity was varied by a factor of 1000 and k(nr) was measured at high pressures, at which the nonradiative rate constant of the molecules decreased from (7 ps)(-1) to (13 ns)(-1), (13 ps)(-1) to (17 ns)(-1) and (17 ps)(-1) to (15 ns)(-1) for 1-propanol, 1-butanol, and 1-pentanol, respectively. The viscosity-dependence of k(nr) is explained by the excited-state rotation rate of the two-ring systems, with respect to each other.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1-Pentanol, ReagentPlus®, ≥99%
Sigma-Aldrich
1-Pentanol, ACS reagent, ≥99%
Sigma-Aldrich
1-Pentanol, puriss. p.a., ACS reagent, ≥99.0% (GC)
Supelco
1-Pentanol, analytical standard
Sigma-Aldrich
Amyl alcohol, ≥99%, FG
Supelco
1-Pentanol, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
1-Pentanol-1-13C, 99 atom % 13C, 99% (CP)