[october]

Hi guys, I'm not a chemist. I'm a researcher in a neurobiology lab.

I'm currently working on a project attempting to both block GABA synthesis and antagonize the GABA receptor simultaneously. I've been working with bicuculline methiodide and 3-thiolpropanoic acid individually in their own saline solutions, and I've just started a new experiment combining low doses of both simultaneously. But it dawned on me today the 3-thiolpropanoic acid might accelerate the decomposition of bicuculline, or there might be a reaction.

I don't have access to an analytical chemistry toys, otherwise I would just run a before and after to note changes.

The concentrations I'm working with are 100uM BMI and 1000uM 3-MPA in a single solution.

http://en.wikipedia.org/wiki/Bicuculline
http://webbook.nist.gov/cgi/cbook.cgi?ID=107-96-0&Units=SI

I tried dragging out some old chem books and working this out on paper, but that proved to be waste of time.



Thanks for any insight!

[nj_bartel]

Just a quick look leads me to think maybe just an acid-base reaction.  You have several basic sites in your bicuculline (all the oxygens and your nitrogen) and you've got a pretty decent strength acid in your thiolpropanoic acid (the carboxylic acid group in particular, and to a lesser extent the thiol goup)

[october]

Any speculation as to what the products might be?


Also, might I be able to make better use of these together in a phosphate buffered saline (pH 7.4)?

You know what? Since I have no idea what the pka of 3-MPA is, I'm going to test the pH of my solution right now.

Be back in 10-20 minutes.

[october]

Alright guys, here's some more data for you:

1000uM 3-MPA: pH 5.9-6.0

1000uM 3-MPA + 100uM BMI: pH 5.8-5.9


I don't understand why the solution containing BMI would have a lower pH, but it does. I tested the machine against the control buffers of pH 4.0, pH 7.0 and pH 10.0, and they are all within 0.05 of dead-on, so.... These are the real values I'm working with.


Thanks again, guys.

[october]

I have a little update:

The BMI as part of the 3MP + BMI solution didn't work in my trial-run experiment. The BMI prevents the maturation of a juvenile behavior by blocking GABA inhibition signaling. But in solution with 3MP left at room temperature for several days, the drug had no effect.

I know the BMI is light sensitive, so I kept it in a light-sealed container. But I firmly believe now the 3MP accelerated its decomposition. I don't know how, nor know it's byproducts, but that is my working hypothesis.

I am repeating the experiment in a hepes buffered solution (pH 7.2). I am also adding BMI into the pre-made 3MP solution daily, just before daily solution exchanges are performed. So in theory, there will be some BMI present in the beginning of the 24 hour period, if only transiently.

Any feel like interjecting anymore input here? Anyone feel like taking a wild guess as to what the reaction may be?