After several months of fighting with a laser system I am finally getting back to slightly firmer ground (at lease educationally, for me) of chemistry. Last year I did some work on a sensor system which could be switched by external light sources, and the time has come to write it up as a paper.

Prepping work for a paper almost immediately means one thing – returning to the lab to repeat everything because I’ve just spotted an annoying flaw/weakness in the original. So back I went to the lab to coat some sensors with mysterious secret thing X.

Unfortunately for me, mysterious secret thing X was not looking quite as friendly as before and the vial where it lived now also housed a small Kracken (that I’ve nicknamed ‘Expi’), or at least something that looked a lot like it.

Toptip: If your mysterious chemical has gone off, don't open it

Top tip: If your mysterious chemical has gone off, don’t open it

Now that I think about it, a more likely explanation is that it was mould. But these things happen, especially because one big problem with mysterious secret things is that they are, err… mysterious. Strange chemicals that only 3 people in the world have ever used, don’t tend to come with very accurate use-by-dates.

This is actually a pretty serious problem in Biochemistry. I buy for example, an enzyme preparation from a company, which has been specially made for me – how exactly does that company produce a use by date? Hell, how does the company even start with the very concept of a use by date…

Gone off teaFor comparison, consider milk. Milk is pretty well understood – it’s been around a while, we’ve got pretty good data on milk spoiling. You can even do experiments at home for kids, where you leave a small glass of milk out on the side and one in the fridge and see how long each takes to go off. But even before you start the experiment, you are already way ahead of what you can do with a random chemical because you have a pretty good idea of what not-good-milk is.

Going back the enzyme for a moment, when has it gone-off? It is when it loses its activity? Possibly, but some enzymes break down multiple things, it might lose activity to one thing very quickly but another very slowly depending on its structure and function. Going-off might affect other aspects of the enzyme that are not obviously measurable, like its ability to function with co-factors or its thermal sensitivity.

But at least with enzymes it actually has a measurable function. What about proteins – how do you tell if a giant ball of amino acids is degraded? Short of periodically running x-ray crystallography you have no real way of knowing how its changed.

The same is true of a number of synthetic chemicals. I work a lot with Calixarenes, which are custom made-to-order molecules. I have more than a few chemicals in my lab that ONLY exist in my lab, with sensitivities and functionalities I could only guess at. What if some of them only work after a certain amount of time post-synthesis? Heamatoxylin for example, is a very common stain used in PAP smears and only works when the ratio of oxidised heamatoxylin molecules in the solution is right. It sounds mad but I have seen current hospital path lab procedures that read “leave solution in open container in the window for 2-4 hours before staining” (that method originates from around 1886 btw).

But to bring it back to my material. Sadly I only had a small sample so I couldn’t do what I normally do with new materials which is run my own little trials where I periodically repeat my experiment to see how the material changes and behaves. Although I am guessing ‘lumpy bits’ won’t help my sensors one bit. But even this is tricky to do most of the time because when I first get a material I have no idea what to expect of it or how I’ll end up using it. By the time I figure out how to measure it it might have already started to turn.

So now I’ve replaced my material and this time I’ve got bucketfulls and have broken it up in to little samples and stashed it away in a very very cold feezer. Which is at least 50% likely to reduce the rate at which it starts becoming sentient and allow me a little more time to run some experiments and finish my all important paper.

It could be worse I suppose, a long time ago in a job far away (when I worked at Mediwatch) we had an inspection by the regulatory people to ensure that we were up to code for CE marking our produce. I was thrilled to bits that our entire lab got through without a single mark against us… except we had to throw away 2 whole batches of lovingly prepared PBS buffer because the inspector found that our pot of Sigma Brand Salt was 1 week expired. How the hell does salt go out of date!!! %$£$.

*ahem*

I still may not be over that.


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