[corneliez]

Hello there, I am doing my research on certain chemicals and I am stuck with Tryptophan. Does anybody familiar with this chemical? I am looking for the physical and chemical properties for it and unable to find any in most papers that i have read (I could have missed tho). By the way, what I am really looking for is the half-life of Tryptophan. Or can anybody point me to the right direction of calculating one. Thank you.

[Arkcon]

Tryptophan is a very commonly known nutrient.  http://en.wikipedia.org/wiki/Tryptophan  I suspect you're going to take this personally but, you really have to try harder when trying to find information -- this is such a common nutrient for living things, there's no way you "just missed" any reference to it.

Now the half-life of tryptophan, that may require a little more work on your part.  You will have to define in what sense you mean it, in what sort of living thing, etc.

[corneliez]

Thank you for your reply. I wont take it personally  . I understand your concerns. My apology if my sentences made me sound lazy.

Actually, my study of Tryptophan is on Tryptophan as a carcinogenic contaminants in waste water treatment plant. Right now I am working on a model to evaluate this chemical fate and transport in the environment. In order for me to run the model, I need certain properties which includes the half-life of Tryptophan in air, water, and soil. I got all the other properties except for the half-life.

I agree with you about Tryptophan being a very common nutrient. However, that's the problem. Most article I read only mentioned Tryptophan on that sense. Only a handful discussed Tryptophan as a environment contaminant and mostly will mentioned the need for further research on this. That's what I am trying to do  . So I really appreciate it if you or anybody can shed me some light on this.

[fledarmus]

To determine the half-life of the compound, you are going to have to find out what happens to the compound. You need to know at least the major chemical pathway of decomposition, and it may be very different depending on whether it is in air, water, or soil. In particular, organisms living in those environments my regard tryptophan as a food source, as alluded to by Arkcon.

Once you know the chemical pathway of decomposition, you can analyze the kinetics of that pathway. Only then will you be able to calculate a half-life.

It is possible that somebody has already done this research, but a couple of quick Google searches haven't turned up that information (which I suspect you have also tried). The only kinetic work I have ever run across with tryptophan is in living organisms and has to do with metabolic pathways. That won't help you much for soil, air, and water decomposition.

Good luck

[Arkcon]

Like fledarmus: said, this topic is unusual, 'tho I'd say its positively strange.  Tryptophan as a carcinogen?  Surely anything in excess is toxic, but the amino acid cause cancer?  As an environmental source?  Meaning it isn't consumed by the biota in the environment?   If you have even one source, let alone a handful of sources, supporting this -- I'd really like to see them.  You may well be on the threshold of an incredibly significant global discovery.  Or someone is making a very big mistake.

[Arkcon]

Whoops.  This fact is a little more well known than I'd thought.  I will have to look up these papers the next time I'm at the university library.

http://www.ncbi.nlm.nih.gov/pubmed/3591519

http://www.ncbi.nlm.nih.gov/pubmed/1920545

http://www.tandfonline.com/doi/abs/10.1080/10934529109375707

From the previews, it appears that tryptophan itself is only implicated in enhancing other carcinogenic effects.  But tryptophan's decomposition products are worse.  So you may have to investigate the entire pathway to get a good picture.

[corneliez]

Thank you Fledarmus, Arkcon. Yes, frankly I am quite surprised when I first told about this since my knowledge on Tryptophan is limited to Tryptophan as an amino acid. "someone is making a very big mistake". That is my exact thought at that moment!

Investigating the whole pathway as you both mentioned is not really a preferred choice for me right now (Unless that is the only way  ). My colleague is actually working on that but that will take some time. My concerns is to run Tryptophan on the model. I tried my best not to spend too much time on the chemical. But this one has set me back for quite a while.

Anyway, Is there really no way to calculate half-life mathematically?

[fledarmus]

Anyway, Is there really no way to calculate half-life mathematically?

Yes, there are a number of ways of calculating half life - see http://en.wikipedia.org/wiki/Half_life . Unfortunately, they require that you have some information about the rate at which the compound is disappearing; at the very least, the amount present at two time points and the assumption of first order rate kinetics. It looks like what you are really looking for is some mathematical way of PREDICTING the half life, rather than calculating it. Even a mathematical prediction would require some idea of what the decomposition pathway was, and what rates could be expected from those mechanisms.

[billnotgatez]

I was of the impression that Tryptophan was the precursor to the neurotransmitter Serotonin. Does that imply that one of the 20 standard amino acids that is also necessary for body function is also carcinogenic? Or a compound that it breaks down into naturally is carcinogenic?