Abstract the Future of Science Ep. 42 – Counteracting CRISPR ft. Ada McVean

39 minute read

Our guest this week, Ada McVean, is pursuing a Master’s of Chemistry at McGill University in the Damha Lab (alongside our good friend James Thorpe from Ep. 30!). Her current research is focused on creating small modified nucleic acid-based inhibitors (or SNuBs) of Cas9 using click chemistry, to interrupt the normal functioning of the CRISPR complex. Questions Answered Why might we want to prevent a CRISPR complex from editing our genes? How do SNuBs interrupt a ribunucleic threesome? If gene editing is a play, who are the characters and what sorts of hijinx do they get themselves into? Can Turtles breathe out of their butts? How do lava lamps produce their magically entrancing goopy light show? Will wearing a hat speed up the balding process? and many, many, many more!

Listen here: https://open.spotify.com/episode/5OCtjggihVNQVNQckMgsdx?si=U3V5arJnQeODCw_DR9kVsw&utm_source=copy-link&nd=1

What is Aquafaba?

Originally published here: https://mcgill.ca/oss/article/nutrition-you-asked/what-aquafaba

Aquafaba (literally the amalgamation of the Latin words for water and bean) is the liquid that remains after boiling legumes. In 2014 a French musician discovered this liquid’s ability to create a foam similar to egg whites, and started a vegan revolution of sorts.

See, for those who do not consume eggs (whether by choice or necessity) certain foods become really difficult to make. Meringues, angel food cake, marshmallows, macarons and some cocktails all rely on eggs for their creation. Egg replacers are common at this point, but they aren’t all the same, and not all of them work for all things. Aquafaba may be just another egg replacer, but it’s got some unique properties that other replacers don’t possess.

The problem is that eggs don’t serve only one purpose in a food. They are what’s called a polyfunctional ingredient, since they serve three distinct and culinarily important functions outside of their taste and nutritional roles: emulsifying, coagulating and foaming. Each of these functions is affected by different conditions like temperature and pH, and each relies on different chemical processes.

Eggs as emulsifiers are the simplest to emulate. In this role the egg serves to stabilize a mixture between two immiscible liquids. Silken tofuflax or chia seeds, bananasmustard (for savoury recipes) or applesauce can all be used as egg substitutes in recipes in which the egg functions only as an emulsifier. The main factor affecting emulsifiers is concentration, with dilute ingredients emulsifying poorly. I really enjoy baking but have largely stopped baking with eggs since eggs mostly function as emulsifiers in my recipes, and substituting them for bananas or “flax eggs” is much cheaper and works just as well!

Eggs as coagulators are more difficult to replace. Eggs coagulate when either heat, strong acids or strong bases cause the proteins in them to denature (lose their structure). The rate and efficiency at which this happens depends on the salt, sugar, and acid content of the food. In eggs the main proteins that coagulate are conalbumin and ovalbumin in the white, and lipoproteins in the yolk. Lots of other proteins coagulate but under different conditions than typically occur during cooking. Egg replacers for coagulation have been attempted. They were made from lupini beanswhey protein, various gums and wheat products, but they haven’t really worked. Replacers made with chia seeds or soy have been a bit better, while replacers made with proteins isolated from whole bovine blood plasma have debatably worked the best but using cow’s blood isolates as an egg replacer probably wouldn’t sit well with most people who use egg replacers.

The foaming ability of eggs is the hardest to replicate. An ingredient’s ability to foam is affected by the method of beating, temperature, pH and water content. Some foods such as soy milk or whey protein can create foams, but these foams are not stable at high temperatures, which is what you need to make angel food cake or meringues.

That’s where aquafaba comes in! It’s vegan, temperature resistant, and made from what would otherwise be waste.

Legumes, like chickpeas, are usually bought either canned and precooked, or dry and uncooked. To cook dry chickpeas you simply boil them for about an hour and a half (pre-soaking dried beans doesn’t actually made them cook faster, so stop wasting your time doing it). During the cooking process the water-soluble proteins and sugars inside the chickpeas are able to travel into the cooking water. The longer you cook the legumes, the more of this migration will occur, as up to about 5% of the dry weight of each chickpea moves into the water. Once you remove your cooked chickpeas, what you’re left with is aquafaba, a sort of protein- and sugar-enriched water.

study has found that the main components of aquafaba are polysaccharides, sucrose, and various proteins. Chemically, this mixture has many of the same components as egg whites, so it makes sense that it can function in many of the same ways. The study also found that some of the compounds most important for aquafaba’s foaming ability are saponins. Saponins, as the name suggests, are characterized by the soap-like foam they produce when shaken.

So how do you actually use aquafaba in a recipe? You basically just whip it up! Using a hand or stand mixer, whip the liquid from your can of legumes or your cooking water for about 3-6 minutes to get semi-firm peaks. You can add some cream of tartar to make the peaks firmer for use in macarons or meringues, or skip the whipping and use it as a binder to make vegan mayonnaise or vegan muffins. The application I’m most excited to try? Aquafaba as a replacement for egg whites in cocktails!

What the Heck Is the Uncertainty Principle?

Originally published here: https://mcgill.ca/oss/article/did-you-know/uncertainty-principle

If you’ve watched the Big Bang theoryor taken some science classes you’ve probably heard of something called the Uncertainty Principle. This theory, which looks like this in formula form: ΔpΔx = h basically states that we cannot know both the speed and the position of a subatomic molecule. Now, at least to me, that has always sounded a little bit like witchcraft. It just doesn’t quite sound real- we can’t both know the position and the speed of a molecule? But recently, in the fourth year of my chemistry degree, I’ve finally had a textbook explain this principle in a way that makes sense. 

You see, to measure a particle’s anything- speed, momentum, position- we need to detect it, or see it, or sense it. In some way, with a machine or our eyes, we need to measure it. And this act of measuring changes the parameter it measures. To ‘see’ a molecule, light (or some other molecule) needs to interact with it.  The photon of light that allows us to see the subatomic particle hits it,and bounces back to our retinas, but some of the energy and momentum of the photon is transferred to the molecule, like when 2 cars collide. So by any means we have of measuring a particle’s position or speed, we influence that parameter. This means that if we want to measure the position of a molecule, we can do so, but the photon we use to do so will change that molecule’s speed, so we can’t ever know the exact speed and position of a molecule.

But this is only true of subatomic particles, right? Nope! This effect actually occurs with everything, from a baseball flying through the air at the Skydome to your dad’s van driving down the road. Why don’t we notice this effect then? Simply because it’s too small.

You’re Not Imagining That Chocolate Sludge at the Bottom of Your Hot Cocoa

Originally posted here: https://mcgill.ca/oss/article/did-you-know/hot-cocoas-black-sludge

If you’ve made hot cocoa with powder, you’ve probably experienced the dark sludge at the bottom of the cup. This chocolate goop seems unavoidable, despite being absolutely certain that you dissolved all the powder when you first stirred your drink. For years I thought I was just a bad stirrer, but it turns out that the sludge actually forms as the drink cools down. As the hot cocoa cools, the solubility of the hot chocolate powder is reduced. This means that the amount of powder you can dissolve in a mug full of water or milk is lessened. So, as the temperature falls, the powder precipitates and collects at the bottom of your mug leaving the hard-to-clean but delicious chocolate goop.

What is this “isobutylene” I keep hearing pop up in the news?

Originally posted here: https://mcgill.ca/oss/article/did-you-know/i-keep-hearing-isobutylene-newswhat-heck-it

An explosion and fire at a Texas chemical plant fuelled by the extremely flammable gas isobutylene has killed one employee and left the public wondering why such a dangerously flammable gas is produced in such large quantities.

Isobutylene (also called 2-methylpropene, isobutene, and γ-butylene because chemists aren’t wonderful at sticking to a one naming system) is a colourless, gaseous hydrocarbon at room temperature.

Its flash point is -80 ˚C meaning that above this temperature, if an ignition source is present, isobutylene will ignite. Since the coldest temperature ever recorded on Earth was -89 ˚C, isobutylene is only a spark away from flames nearly everywhere on earth at all times.

Isobutylene is widely used in the synthesis of many things, largely because it contains a double bond which can be easily reacted to form other products. It can, for example, react with ethanol to form ethyl tert-butyl ether (ETBE), a gasoline additive that raises the octane number, making the fuel more resistant to knocking, or spontaneous combustion. Or it can be combined with itself in a long chain to form a polymer, butyl rubber.

Butyl rubber is hugely useful. It’s airtight, so it can be used to make seals like O-rings, window seals or cling film, as well as bottle stoppers, kickballs and tires. It’s tasteless and odourless, so it can be added to chewing gum, which, once chewed, can be collected and recycled to recover the isobutylene.

Like other forms of rubber, butyl rubber will break down when exposed to solvents like ammonia but will do so much slower than other rubbers. This has led to its widespread use in protective articles of clothing and gas masks.

Where do we get all this isobutylene from? Natural gas. Butane (the fuel that’s in your Zippo lighter) can be derived from mined natural gas and turned into tert-Butyl alcohol, which can then be turned into isobutylene.

So, while it’s not the most sustainable chemical around, isobutylene’s many varied uses can explain its mass production. Unfortunately, due to its extremely flammable nature, precautions do need to be taken to avoid fires like the one that occurred in Texas.

The key to cleaning your teapot is chemistry

Originally published here: https://mcgill.ca/oss/article/did-you-know-general-science/key-cleaning-your-teapot-chemistry

Do you ever try to wash a mug only to be confronted by tea stains that just won’t budge? A little bit of chemistry may be just what you need to get your mugs back to white.

Brewed tea, green or black, contains many compounds, including many polyphenols. These are compounds found naturally in tea leaves that have antioxidant properties and contribute to the taste of tea. However, they are also responsible for the stains left in your mugs and teapots.

Polyphenols are a large group of complex molecules that are structurally similar in that they all contain simpler components known as phenols. Tannins are a class of polyphenols that provide tea with its characteristic hue, and are responsible for those annoying stains. Being largely impervious to scrubbing, how can these stains be removed?

A little bit of chemistry.

Black tea has a pH of 4.9, meaning that it is slightly acidic. While tannins encompass a wide variety of compounds, they all tend to be slightly acidic. As such, to remove them from the sides of your mug, you need to neutralize them with a base. the most readily available of which tends to be baking soda.

Just make a paste of baking soda and water, rub it onto your stained crockery, leave it for 20 minutes or so, and then wipe it off with a sponge. It certainly worked wonders on my now much-cleaner teapot.