[bennettb6]

Hi guys,

I am doing an independent research study with my professor involving spectroscopy and Thioflavin T. I have prepared 10 concentrations of thioflavin t (1e-4 to 1e-7 M) and run absorption, emission, and excitation spectra on them. What was expected was that as the concentration was higher the absorption would become less than the theoretical amount determined by Beer's law, because dimers would begin to form. However, just the opposite appears to have happened. The high concentrations are very close to the theoretical values and the lowest concentrations have slightly lower absorption values than expected.

Also, the excitation spectrum shows the first peak at 330 nm when parked at 475 but begins to show a more and more dramatic second peak at about 412 as the concentrations get very low.

Everything seems to be happening in the opposite direction. So here's my hypothesis, tell me if it holds any water whatsoever. I believe that the formation of this dimer is a spontaneous reaction in one direction but not spontaneous in the reverse direction. This means that dimers are being formed at high concentrations, but as I dilute the solutions the dimers from the high concentrations stay in solution instead of turning back into monomers. This is causing the absorption at the monomer peak to be lower at low concentrations and making the dimer peak at low concentrations more significant.

This is the only explanation I can think of. What do you think?

[Honclbrif]

Does it happen if you cook up a batch of the more dillute stuff without doing serial dillution? *warning, may require hyperfine balances and/or enormous glassware*

What have you read about the solution phase dimerization of thioflavin T? Have you looked into excimers or exciplexes?

What absorbance values are you looking at? Beer's law gets wonky when things get too dillute or too concentrated.

If irreversible dimerization is occuring, how could you confirm this?