lab technique

Hack your inkjet printer and turn it into a lab robot

If you stop and think about it for a moment, you will realise what an astonishing feat of precision engineering your colour printer is. It can take the primary colours – cyan, yellow, magenta and black – and mix them together carefully enough to achieve more than a million different hues and shades. Not only that but the drops of colour are mere nanolitres (billionths of a litre) in volume, each of which is then placed on the paper – assuming its not jammed in the feeder tray – with better than pinpoint accuracy.

Now a group of enterprising chemists from Tsinghua University are exploiting that precision engineering, which normally results in high-resolution colour prints, to screen millions of different chemical reactions. Their results have been published in the journal Chemical Communications.

Yifei Zhang and colleagues have been trying to understand reaction pathways in living things. Every chemical process that goes on in living organisms is controlled by a cascade of reactions. The steps in a cascade are mediated by protein molecules called enzymes. Each enzyme makes a small chemical alteration, like workers on a production line, to a molecule before passing its product onto the next enzyme. In this way, for example, plants build sugars from carbon dioxide and your food gets broken down and then reconstructed into other useful chemicals for your body.

The problem is that to understand these complicated processes by reconstructing them outside of a living cell is difficult. The concentrations of an enzyme relative to the next in the line is key. Get this wrong and bottle necks are formed in the production line, as one enzyme works faster than the next.

To figure out what are the right conditions to replicate a living cell’s workings, chemists must set up and monitor a vast number of reactions. Screening large numbers of reactions like this is often done using “96-well plates”, which are 96 tiny containers with a unique combination of chemicals in each. These reactions might be set up manually or, if the lab is well-funded, by an expensive robot. But even with the best robots available it can still be a slow process.

Colour printers are a lot cheaper than robots. And if the inks are replaced by solutions of enzymes then suddenly you have a device that has the potential to dispense more than a million different reaction mixtures.

That is just want Yifei and colleagues have done. Their printers were loaded with a series of enzymes that, when they work together in the correct ratios, produce coloured reaction products. These were printed directly onto paper where it was immediately obvious, from the intensity of a coloured dot, which reaction mixtures worked best.

In the test cases reactions were deliberately chosen that resulted in colour changes. This made for a nice quick visual indication of whether the system worked well. So for example one test started with glucose and a chemical called ABTS in the magenta cartridge, then the enzymes glucose oxidase (GOx) and horse-radish peroxidase (HRP) in the yellow and cyan cartridges. When they are mixed together the GOx removes a hydrogen from the glucose and adds it to oxygen, producing hydrogen peroxide. Next the HRP reacts this with the ABTS, which results in a green chemical.

The potential applications for these printer-based mixtures extend beyond curiosity-driven research on biological pathways. Yifei and colleagues have already shown that by loading the printer cartridges with the right enzymes they can use the set up to indicate the presence of glucose in a sample. Glucose in urine is a indication of diabetes, so their printer-based chemistry already has the potential to diagnose diabetes.

The result then could be a future where a trip to the doctors results in a printout of, quite literally, your urine and some enzymes alongside, after 30 seconds or so, a diagnosis and the prescription.

The Conversation

Mark Lorch does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published on The Conversation.
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By September 16, 2014 5 comments lab technique

TedED: Increasing Reaction Rates, or How to Get A Date

From the Chemistry Reddit, a TedED animation by Aaron Sams describing 5 ways to increase the rate of a chemical reaction. I’m not following all the analogies, but it’s still a pretty good teaching tool.

Nitroolefins – The Crying Game

(This post was written for the ‘Toxic Chemicals’ carnival, over at ScienceGeist)

Let me tell you about the time I broke down crying in lab. No, it wasn’t an epic breakup, or even a death in the family. It was…a nitroolefin.

Many summers ago, I worked as a pharma intern, a small flywheel in a then-huge drugmaking machine. My supervisor, a kind, safety-conscious scientist, begged me to come straight to him if I had any questions about my reactions.

We were synthesizing a small nitroolefin – 2-nitropropene, to be exact – for some nitro-Michael additions. If you look at the Org. Syn. prep, it warns, right at the top in red letters, that the compound is a potent lachrymator. The term, from the Latin word for “teardrop,” describes compounds that irritate the eyes to such an extent that tears freely flow.

I carefully piloted the reaction, distilled the greenish-yellow product, and then watched it run up my TLC plate. Beautiful! Now, I just needed an NMR sample.

Gingerly, I dissolved a drop into some chloroform. Forgetting for an instant, I pulled the NMR tube out of the hood to cap it, and within seconds crumpled to the bench. It felt as if someone had stabbed smoldering iron toothpicks into my eyes. I stumbled around until my labmates dragged me over to the eyewash; later, I became well acquainted with our local safety officer. My eyes remained bloodshot for the rest of the day. Lesson learned: Lachrymators are not to be taken lightly! (I’ve experienced similar, though milder, reactions to benzyl bromide and thionyl chloride).

For those younger chemists thinking about summer lab work, take a few minutes to find out if your reagents might cause uncontrollable crying. Cautious handling, and a well-fit respirator, can go a long way towards your future safety and comfort.

What’s in Lemi Shine? – UPDATED


Lemi Shine is magical.  We must have the hardest water ever. Any harder and I’d be able to walk on it. Our dishes had the grossest white film on it that just kept getting thicker and grittier and grosser.  I thought we were going to have to wash dishes by hand or buy new dishes.  Then we tried adding Lemi Shine.  No joke, after 2 or 3 cycles, the dishes look like new.  I wish I had before and after pictures.  Imagine an opaque drinking glass next to a crystal clear drinking glass. Actually, the picture on the bottle could have been taken in our kitchen.

So I wanted to know what voodoo powder is in Lemi Shine that allows for such magical transformations to happen.  Looking on the innertubes, people making home-made dishwasing detergent often have a line like ‘add Lemi Shine or lemon Kool-Aid packets.’ So that’s weird. The label on the bottle says it contains ‘natural fruit acids and citric oils.’ Ok, so maybe the lemon Kool-Aid isn’t so weird. Here’s a list of natural fruit acids.

So I turned to the MSDS in hopes that it would divulge the ingredient list.  The Lemi Shine MSDS was really easy to find, but the composition section reads:

Well, thanks.  That could not be less informative.  So my bottle contains between 61-105% of something? (maybe the rest is chemical free. oooooh!) The only actual quantitative information the MSDS provides is a pH of 3 and some LD50 data: Compound1: 3000 mg/kg (rat, oral); Compound2: 2840 mg/kg (rat, oral), 5000 mg/kg (rabbit, dermal – what did that experiment look like?)

So I guess since I’m a chemist, I should bring some into lab and figure it out myself, eh? So I did.

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By May 18, 2012 99 comments lab technique