Seeing oxidation and reduction

Why do our cosmetics change over time?

Sometimes it’s because of oxidation, the loss of electrons. Ascorbic acid is easily oxidized, losing two electrons, becoming dehydroascorbic acid. Enzymes and antioxidants in our body can give dehydroascorbic acid back those two electrons, reducing it back into ascorbic acid.⁣⁣

Your foundation getting darker after it dries isn’t oxidation, even though it’s often called that. It’s just the water or solvent in the foundation evaporating. If you’ve ever painted, you’ll know that wet paints tend to dry darker.

Methylene blue is a deeply blue organic dye. It is can be used in analytical chemistry as a redox (reduction-oxidation) indicator.⁣⁣
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In oxidizing environments, methylene blue is a bright blue, in reducing environments the methylene blue accepts electrons and becomes leukomethylene blue which is colourless.⁣⁣
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In the vial is an alkaline solution of glucose. Glucose is a reducing sugar, which means it can donate electrons. This creates a reducing environment for methylene blue, so the methylene blue is reduced to leukomethylene blue.⁣⁣
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When the vial is shaken, oxygen is dissolved into the solution – this oxidizes the leukomethylene blue causing it to lose electrons, turning it back into bright blue methylene blue. In turn, the oxygen is reduced to water.⁣

As the oxygen is consumed by the reaction, the glucose reduces the methylene blue – turning it back into the clear and colourless leukomethylene blue. In turn, the glucose is oxidized to gluconic acid.⁣
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In the video, you’re seeing excess oxygen dissipating out of the solution, as well as oxygen being consumed by the reaction.⁣

This experiment is repeatable by shaking in more oxygen, but won’t go on forever – eventually, all of the glucose will have been oxidized to gluconic acid and the glucose is needed to reduce the methylene blue.⁣

Oxidation was first observed with oxygen, hence its name. However, the modern definition of oxidation is the loss of electrons. Anything that can gain electrons, causing something else to lose electrons, is an oxidizing agent.⁣⁣
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Some common oxidizing agents that aren’t oxygen are elemental halogens like fluorine, chlorine, bromine, and iodine. Fluorine (F2) is such a strong oxidizer it can oxidize water into oxygen! ⁣⁣
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2F2 + 2H2O → 4HF + O2

Yes Virginia, vegan collagen is real!

When Algenist launched the Genius Liquid Collagen with “vegan collagen” my first thought was, “What? Only animals have collagen!”⁣

Well, you’re looking at a vial of collagen that has been produced by yeast.⁣

Collagen is the main structural protein in animals, there are over 28 types of collagen. Type I collagen makes up about 90% of the collagen found in humans.

Collagen gives our skin its strength, flexibility, structure, and durability. Collagen is a triple helix, made of three coils of amino acids wrapped around each other. This coiled structure allows collagen to be stretched without breaking.⁣ Check out an earlier post I wrote about collagen for more information.

Plants and microbes don’t normally make collagen, but turns out they can! With some help from science, of course.⁣

Vegan collagen is often produced from modified yeast and bacteria, scientists have been doing this for decades. Collagen can also be produced by modified plants, like the tobacco plant.⁣

In one method, 4 genes that encode for the building blocks of collagen were added into a yeast’s genetic structure. The human genes were expressed in the modified yeast and they started producing the building blocks of human collagen type I. These building blocks were collected and treated with pepsin (a digestive enzyme), which assembled them into collagen and broke down any material that didn’t form properly.⁣

Why make microbe or plant-based collagen? It’s often purer and it doesn’t rely on animals. Though it occurs rarely, animal collagen can cause foreign body or allergic reactions. Animal sources of collagen are fish, pigs, and cows.⁣

Collagen is useful as a moisturizer for the skin, but also has medical applications. Collagen is used as a material for cosmetic filler, as carriers in drug delivery, as sutures, and as scaffolds for tissue engineering. Collagen can also be modified and used for neuron regeneration, blood vessel repair, bone regeneration, wound healing, and more!⁣

M Nokelainen, High‐level production of human type I collagen in the yeast Pichia pastoris, Yeast, 2001. DOI: 10.1002/yea.730

Paperview: Air quality and relative humidity in commercial aircrafts

Why is airplane air so dry?

Outside air at a plane’s altitude is very cold and less dense. Cold air can hold less water compared to warmer air. At a plane’s flight height (around 10 km) the outside air can hold about 10% what it can at ground-level.

Outside air is warmed, filtered, and then cycled through the cabin air about 20 times an hour, depending on the plane model. Air inside the cabin is also filtered and recycled. The mix between outside air and recycled inside air is about 50/50.

Below, the solid black line shows the measured relative humidity inside an airplane’s cabin during a flight. You’ll see that about 15 minutes after take-off the relative humidity drops quickly to its low of about 10% – which is maintained until close to landing.

Why can’t they humidify the cabin air?

That does happen! But let’s go over some of the issues with humidifying a cabin.

As warm air cools, we know that the amount of water it can hold drops as well and that water it can’t hold anymore will condense on surfaces. We’ve all experienced this when we see condensation or “sweat” on a cold glass during a hot, humid day.

The outer layers of a plane are much, much colder than the inside of the plane and that change in temperature can cause condensation. That condensed water can be absorbed into the plane’s insulation which adds weight and more fuel costs, cause corrosion of metal parts, and even affect electrical wiring.

OK so, what about these humidified planes?

Newer plane models, like the Airbus A350 and Boeing 787, can be ordered with on-board humidifiers. They work by passing the cabin air over a water-moistened pad, as the water evaporates – it humidifies the air. That’s not all though, to prevent some of the mentioned problems above, the humidifying system is also paired with a drying system. The drying system warms incoming air and passes it through a silica gel – which absorbs excess water and dries the air. This reduces condensation as cabin air passes through to the outer areas of the plane – where water can cause problems.

These humidified areas aren’t available to everyone though. They’re often standard for areas that the crew members are in, but when it’s available to passengers it often comes with a premium. CTT, one manufacturer of these humidifying/drying systems, says that they’re often only found in business class and other luxury sections.

So what can you do about the dry air in a plane?

While the dry air can feel uncomfortable for our skin, it’s not likely to cause long-term problems.

Trans-epidermal water loss (TEWL) from the skin does seem to increase because of the low humidity, which can lead to dryer skin – especially on longer flights. One experiment found that TEWL increased from 13.0 ± 2.2 g/m²h at 60% humidity to 20.1 ± 4.9 g/m²h during a simulation of a 6-hour flight.

Applying a moisturizer before or during a flight could be of great help. Whether that’s a sheet mask, mist, lotion, balm, or potion. Or if you’re lazy like me and don’t feel like doing anything, your skin will naturally recover once you’re off the plane and back at a normal humidity.

Based on experiments with crew members, we tend to feel the low humidity the most in our eyes (10.8%), mouth and throat (7.0%), and nose (5.0%). Sinus congestion was also a common complaint, occurring in 29.0% of those surveyed.

Moisturizing eye drops (I like the Systane Ultra drops) can help with the eyes. A light-swipe of petrolatum (Vaseline) or another balm inside the nostrils can help with the nose. As for the mouth and throat, keep some water handy! You don’t need to guzzle gallons though, there’s little evidence that low humidity leads to your body becoming dehydrated. One experiment found that for a 6 hour flight, a 60 kg person would need about 450 ml of extra water.

Source: Giaconia, C., Orioli, A., & Di Gangi, A. Air quality and relative humidity in commercial aircrafts: An experimental investigation on short-haul domestic flights. Building and Environment (2013). DOI: 10.1016/j.buildenv.2013.05.006

Source: Lindgren, T., Norbäck, D., & Wieslander, G. Perception of cabin air quality in airline crew related to air humidification, on intercontinental flights. Indoor Air (2007). DOI: 10.1111/j.1600-0668.2006.00467.x

Hashiguchi, N., Takeda, A., Yasuyama, Y., Chishaki, A., & Tochihara, Y. Effects of 6-h exposure to low relative humidity and low air pressure on body fluid loss and blood viscosity. Indoor Air (2013). DOI: 10.1111/ina.12039

Paperview: Sunscreen application to the face persists beyond 2 hours in indoor workers

What happens to your sunscreen throughout a work day? I often get this question, especially from people who work inside for most of the day. A group of researchers at Mahidol University in Thailand did an experiment that may provide us with some guidance.

The researchers took 20 people (15 women) with mostly skin phototype III and up. Skin phototype III means that they tan, but sometimes get mild burns.

The participants were asked to apply 1 gram of sunscreen to their face. The sunscreen was mixed with a blue fluorescent dye that would glow under UV light. This glow allowed the researchers to see the sunscreen on the skin and note changes in its brightness throughout the day.

The people only wore the sunscreen and were asked not to reapply. They weren’t allowed to use makeup or other skincare. They were also allowed up to 1 hour outside. The temperature outside was between 23 and 35 degrees Celsius throughout the day and described as humid. The indoor condition was inside the air conditioned Siriraj Hospital.

Every 2 hours, the researchers took a photo of the people and measured the glow of the sunscreen under a UV light. They looked at the cheeks, forehead, nose, moustache area, and the chin. They used a Visia device to help make sure the photos were consistent.

Sunscreen brightness reduction every 2 hours by percent. The bars indicate the range in measurement values.

The researchers found that the fluorescent glow on the people’s faces decreased the most in the first 2 hours after applying the sunscreen. On average the areas of the face were 16.3% less bright.

Between 2 hours and 4 hours after application, the brightness decreased by a further 7.4 percentage points on average. Between 4 hours and 8 hours, there was an average 4.5 percentage point decrease in brightness.

At the end of the day, there was about a 30% decrease in brightness on average compared to just after applying the sunscreen.

A 30% decrease in brightness in this experiment doesn’t necessarily mean a 30% decrease in sunscreen on the skin. There are ways to model this more accurately, but they did not have the tools in this experiment.

So what does this mean for you? At the end of the day, you’ll still have to use your best judgement.

If you pigment easily, are very concerned about photoaging, or have a family history of skin cancer – I think the best recommendation is to be on the safe side and reapply at least once around 2 hours.

If don’t care that much, consider the opposite, about 70% of the glow from the sunscreen still remained after 8 hours.

In either case, that first application is important. I’d recommend choosing a sunscreen with a high SPF and UVA protection and aiming for a 2 mg/cm² layer. An easy way to make it more likely you’ve applied that amount is to apply your sunscreen in two layers.

Source: Rungananchai, C., Silpa-archa, N., Wongpraparut, C., Suiwongsa, B., Sangveraphunsiri, V., & Manuskiatti, W. (2018). Sunscreen Application to the Face Persists Beyond 2 Hours in Indoor Workers: An Open Label Trial. Journal of Dermatological Treatment, 1–14. doi: 10.1080/09546634.2018.1530440

A quick look at collagen

Collagen, you’ve seen it in your skincare products and have probably eaten it at some point (Yay for artificially-coloured and jiggly gelatin). But what is it?

Collagen is composed of a triple helix, three strands of proteins made up of joined amino acids wrapped around each other. The main amino acid constituents of these proteins are glycine, proline, hydroxyproline, lysine, and hydroxylysine. The unique chemical structure of the amino acids helps form the shape and structure that their compounds make.

There are many types of collagen, which differ in their amino acid composition. Type I collagen is the most abundant in the human body, and Type I, III, IV, and others are found in our skin. In our body, multiple strands of collagen are found bundled together in fibrils.

You may have heard that ascorbic acid or Vitamin C is crucial in the formation of collagen, but how? Ascorbic acid is used in the conversion of proline to hydroxyproline along with oxygen, and alpha-ketoglutarate. The reaction is catalyzed or sped up by the enzyme prolyl hydroxylase and an iron. Similarly, it is needed in the hydroxylation of lysine to hydroxylysine by the enzyme lysyl hydroxylase.

Collagens are naturally glycosylated, meaning they have sugar molecules bound to them – they are found attached to the lysine and hydroxylysine molecules by the enzymes galactosyltransferase and glucosyltransferase. While this glycosylation is not fully understood, they seem important in forming and retaining the structure of the collagen. You may have heard of glycation or advanced glycation endproducts (AGEs), this happens when excessive sugar molecules are bound to the collagen non-enzymatically and can affect its structure, function, and flexibility.

The additional -OH (hydroxy) group on the hydroxyproline helps water molecules bind tightly to collagen. The coiled structure of collagen’s triple helix gives it impressive tensile strength and allows it to stretch when forces are applied. When too much force is applied the triple helix structure can become disorganized and damaged, no longer able to return to its triple helix form.

Experiments, where collagen was exposed to UV radiation in vitro, have shown that free radicals generated from the UV energy can cleave or break apart some of the bonds holding the amino acids together. When enough bonds are broken the triple helix structure can no longer be maintained and the collagen fibre loses its shape and function. Adding ascorbic acid to the solution of collagen, when it was exposed to UV, reduced some of the free radicals produced – leading to fewer bonds breaking and structure disruption. This may highlight one of the ways naturally present antioxidants in the skin help us defend against the environment.

N. Metreveli, L. Namicheishvili, K. Jariashvili, G. Mrevlishvili, A. Sionkowska. Mechanisms of the influence of UV irradiation on collagen and collagen-ascorbic acid solutions. International Journal of Photoenergy (2006), DOI: 10.1155/IJP/2006/76830

Duer Research Group. Collagen glycation and diabetes. Website, URL: https://www.ch.cam.ac.uk/group/duer/research/collagen-glycation-and-diabetes

A. Masic, L. Bertinetti, R. Schuetz, S.W. Chang, T.H. Metzger, M.J. Buehler, P. Fratzl. Osmotic pressure induced tensile forces in tendon collagen. Nature Communications (2015), DOI: 10.1038/ncomms6942

J.M. Waller, H.I. Maibach. ge and skin structure and function, a quantitativeapproach (II): protein, glycosaminoglycan, water, andlipid content and structure. Skin Research and Technology (2006), DOI: 10.1111/j.0909-752X.2006.00146.x

The enzyme lysozyme and xanthan gum

These are crystals of lysozyme, an enzyme which can break apart cell wall peptidoglycan of certain bacteria. It is part of our and other animals’ immune systems. Lysozyme is more effective against gram-positive bacteria, as gram-negative bacteria have additional cell membranes that make it harder for the lysozyme to reach the peptidoglycan.

Lysozyme is often used in the processing of xanthan gum. Xanthomonas campestris, a gram-negative bacteria, produce an exopolysaccharide which is a gooey, thick, and sticky slime. This slime may help the bacteria create a comfortable environment for itself and also act as camouflage from other organism’s immune systems.

The slime (aka xanthan gum) is used in cosmetics because it imparts viscosity, lubricity, and acts as a humectant water-binding film former. It also increases the yield stress of water, meaning things suspended in it don’t settle as fast. “Raw” xanthan gum can resemble snot and be cloudy.

In a series of processing steps, the Xanthomonas campestris’ cells are stripped of their membranes and broken apart – this can be done by heating in alkaline water then by treatment with lysozyme and protease. The xanthan gum becomes less gloopy and crystal clear.

Lysozyme can be sourced from a variety of things, but most commonly hen egg whites. It’s not often clear what the source of lysozyme is, so depending on the transparency of the supplier, it’s possible that products labelled ‘Vegan’ may have used animal lysozyme treated xanthan gum.

Plant-based lysozymes do exist, but their structures and functions often differ from animal lysozymes. Genetically modified organisms have been created to produce lysozymes more closely resembling animal lysozymes, but GMOs can be an issue for those who choose vegan products.

I first encountered this conundrum during a meeting with a supplier when they were promoting their vegan xanthan gum, which was slightly less clear than their regular grades. I’d always assumed xanthan gum was vegan, since it was made from bacteria. Sadly, the product line has been discontinued, but one of the largest chemical companies in the world recently launched a clear vegan xanthan gum that’s also GMO-free.

To see more images of lysozyme crystals, check out Dr. Kalju Kahn’s gallery created by students at UCSB.