Understanding Membrane Biology and Surface Tension with Meringue

I am particularly interested in Molecular Gastronomy.  As a biophysicist and amateur chef I love thinking how each protein is becoming denatured, how there is a change in the hydrophobic properties of pasta, or how the phase properties of chocolate changes in a double boiler.  It is amazing and scientific.  People are still exploring new ways to make and manufacture food.  In fact we do have a lot of interesting things to discover in food properties that we never thought imaginable unless science and experimentation is introduced.  Things like eating new kinds of species (e.g grasshoppers), discovering a new process to make something e.g. space icecream or using a different kind of bacteria or yeast for Kimchi or beer production.   We have a lot of things to discover in food since for me making  

Inside-Out Proteins Bubbles

At some point people (possibly French people I should check in Jen Gardner's book Meringue) started beating egg whites, a pinch of sugar and some vinegar so much that they foamed.  The hydrogen bonds were broken then reformed repeatedly until they made a new kind of structure.  The ovalbumin and lysozyme in egg are normally in a water soluble medium so they have their 'water-loving' part on the outside and their 'water-hating' parts on the inside.  This is also their minimal energy state.

However, when you beat these proteins into submission half the proteins are formed with water and the other half are exposed to air.  A new minimum energy configuration is made where you 'water-hating/hydrophobic' proteins are on the outside and the 'water-loving/hydrophilic' proteins are on the inside.  It is as if you were to blow a soap bubble and one part of the soap is exposed to the water in the middle whereas the other part is exposed to the air.  Meringue is these bubbles with two layers of protein separated by water in the same way as the soap bubbles.  Sugar is also mixed into the egg whites to increase their viscoscity.  Cooking helps remove some of the water so the layers become stiff with the sugar forming the hydrogen bonds both sides of the proteins.  If one were to look at a a cross section of a meringue bubble you would see: air outside, hydrophobic amino acids of outside protein, hydrophilic amino acids, sugar, hydrophilic amino acids of inside protein, hydrophobic amino acids, inside air.




Colloidal Mediums 


So we understood the actual molecules (the proteins) behave but let's look at the bubbles as a whole.
The surface tension in the layers of water molecules on the inner and outer surfaces of membranes, hold the water and protein bubble membranes together to create a foam.  The foams are called colloids.  A colloid consists of a  dispersed phase (protein) and a continuous phase (water).

From a thermodynamic point of view,  all emulsions and food colloids are unstable e.g. the free energy of food is higher in the emulsion or colloidal state than it would be if the food were to separate fully into two (or more) macroscopic regions. For example, a meringue is only in a medium of the proteins and the sugar for a certain period of time before the foam breaks down (baking it makes the colloid more stable).

Once you stop whipping the eggs and leave the foam you will see it separate.  The internal interface area of the system creates the excess free energy of an emulsion.  The excess Gibbs free energy of creating a surface of area, dA, can be written as dG ) γ(dA), where γ is the surface free energy density or the surface tension γ ) ((∂G)/(∂A))T,p.  Mixing other ingredients like sugar, emulsifiers or surfactants can help to change the free energy of the system and potentially stabilize the colloid mixture so it won't separate so you can get the Meringue Pie for whatever occasion!


 

Read more at Suite101: Teaching Membrane Biology with Meringue: Egg White Bubbles and Cell Membranes | Suite101.com http://suite101.com/article/teaching-biology-with-meringue-a192409#ixzz27a8tZM4l

Molecular Gastronomy: A New Emerging Scientific Discipline Peter Barham et. al  (2010) Chem. Rev. 110, 2313–2365

http://boingboing.net/2012/09/04/the-history-and-science-of-mer.html

Oil Spills Part III: fluoroPOSS

There is a race to clean up the oil spills.  So many different research groups are covering this.  And the video pretty much explains it all. These researchers from the University of Michigan show that an ordinary polymer and a nanoparticle called fluoroPOSS can help to separate oil.  They make a coated filter and then dipped it into the water mixed with oil.  What happens is some kind of magic.  The nanoparticles (think like putting oil into your teflon pan it is a similar material) have a low surface energy causing the oil droplets to strongly attach to eachother.  The oil droplets for beads on the surface of the filter (which was seen as strange).  The opposite happens to the water.  The capillary action governed by the surface tension is different so oil beads up and the water is washed away.  The best part of the process is that it happens with gravity (so no special machines) and  can reuse the material for 100 hours before getting clogged..

How did the real life tests pan out?  The group has a 99.9 percent efficiency! 

Cleaning up oil spills with ferric fluids part II

I talked about ferrofluids soaps that was researched at the University of Bristol and how they could be used  for oil spills and the like.  These researchers at MIT tried it out. They used magnets really, really tiny magnets to transform oil like oil polluting the Gulf of Mexico into trapping it with a ferrofluid that can be manipulated.  This could separate the oil from the water then could be recycled and the oil stored.  Simple?  Well it sounds simple but that is why they are still researching it.

[Via MIT and Tim McDonell and the Guardian and Robert T. Gonzalez at Via Io9 ]

Why is it 72 dynes?

Really the surface tension of water is 72 dynes?  Yes.  As the name of this blog suggests it is only 72 dynes.  However, according to a study by Angus Gray-Weale and colleagues this could be even larger depending on the attraction between hydroxide dipoles but is reduced by a 'layer of hydroxide-enriched water extends up to a nanometre'.  The results are controversial but interesting as they still try to understand surface tension at different levels.  Still more understanding is needed on both macroscopic and microscopic levels to understand what is happening at the air-water interface.  For a summary of the article it is here:

 
http://www.rsc.org/chemistryworld/2012/08/getting-under-skin-water

References

1. M Liu, J K. Beattie and A Gray-Weale, J. Phys. Chem. B, 2012, 116, 8981 (DOI: 10.1021/jp211810v)

How to Improve Teaching about Surface Science in Schools?

Two people asked me a couple of questions in the last couple of years that got me thinking about teaching surface chemistry and surface tension better in schools.  After hearing these questions I thought that there could be a lot of improvements........


Question 1:
I was at the Biophysical Society Conference a couple of years ago.  A researcher from Seattle asked me: Why aren't there any monolayer devices in undergrad university labs?

This question surprised me.  I studied biochemistry and never really got into to biophysics until after my undergrad years.  I looked into it further and it seemed that there were not a lot of university teaching laboratories with good monolayer facilities.  Several of the teaching of monolayer happens in academic research labs.  However, several simple systems could be understood in physics, biophysics and surface chemistry laboratories using simple, inexpensive, student proof instruments.

One student proof instrument for measuring films could be the MTX.  I have seen this instrument used and abused by students in our lab.  Even after 7 years it still runs and allows our group to make interesting advances in surface science.

2) Question 2:

This was asked by colleague after saying, 'in Spain we had this really really ancient Du Nuöy ring that was all bent and we had to teach a lab with this.  The surface tension of water would come up to be 52 dynes/cm2.  I was the teacher.  Then a student asked me, 'but isn't it supposed to be 72 dynes/cm2'.  In which I replied while sweating, 'Yeah well somethings wrong with the instrument'. 

This has likely happened to many teaching assistants and professors in trying to demonstrate how to measure the surface tension of water or some other liquid.  It is a pain to actually teach using devices that are destroyed, difficult to use and difficult to calibrate.  So teachers forgo teaching about interesting fun systems like beer foam, the films covering devices like the iphone, why certain body soaps (eg. Axe vs. L'Oreal ) are better.

One student proof instrument for teaching surface tension in a lab is the AquaPi.  I have heard  from the Aalto University's chemistry teaching lab that the instrument is fast and reliable.  The students can understand surface chemistry instead of trying to make difficult measurements.

Overall buying a studentproof instrument makes everybody's lives easier!

Spiderman Sticking to a Submarine: New Bionic Material Even Sticks To Surfaces Underwater

New Bionic Material Even Sticks To Surfaces Underwater

I was always wondering how Spiderman could climb walls and whether his webbing could work underneath the water say if he was to stick to a submarine or something.  Bugs as you know can crawl everywhere.  I found some insects upside down on my plants and I wondered: 'How did they get there?'  Well surface tension is at play (also insects have a weight strength distribution that is beyond our imagination just look at Antman).  Insects use capillary forces with oil-covered adhesive called setae.  But what happens when the it rains and the properties of the surface of the plant change.

Well scientists Gorb and Honosa published: 'Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces', Proceedings of the Royal Society B to describe this.  The terrestrial leaf beetle. The cool thing about the leaf beetle is it uses air bubbles trapped between their adhesive setae producing a boundary between the air, the liquid and the solid which ultimately produces capillary adhesion under water.  One necessary requirement would be for the surface of the leaf but as you know many leaves (including the lotus) have hydrophobic property.

But what is this solid material (the Spiderman webbing) for the beetle.  The solution was a micro structure they designed which is an 'artificial silicone polymer structure with underwater adhesive properties'..  One could think of any field of application for underwater technologies like optics or perhaps even allowing Spiderman to stick to a submarine better.

Citation: Naoe Hosoda and Stanislav N. Gorb, 'Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces', Proceedings of the Royal Society B, Published online before print August 8, 2012, doi: 10.1098/rspb.2012.1297

Spiderman Sticking to a Submarine: New Bionic Material Even Sticks To Surfaces Underwater

New Bionic Material Even Sticks To Surfaces Underwater

I was always wondering how Spiderman could climb walls and whether his webbing could work underneath the water say if he was to stick to a submarine or something.  Bugs as you know can crawl everywhere.  I found some insects upside down on my plants and I wondered: 'How did they get there?'  Well surface tension is at play (also insects have a weight strength distribution that is beyond our imagination just look at Antman).  Insects use capillary forces with oil-covered adhesive called setae.  But what happens when the it rains and the properties of the surface of the plant change.

Well scientists Gorb and Honosa published: 'Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces', Proceedings of the Royal Society B to describe this.  The terrestrial leaf beetle.

The cool thing about the leaf beetle is it uses air bubbles trapped between their adhesive setae producing a boundary between the air, the liquid and the solid which ultimately produces capillary adhesion under water.  One necessary requirement would be for the surface of the leaf but as you know many leaves (including the lotus) have hydrophobic property.

But what is this solid material (the Spiderman webbing) for the beetle.  The solution was a micro structure they designed which is an 'artificial silicone polymer structure with underwater adhesive properties'..  One could think of any field of application for underwater technologies like optics or perhaps even allowing Spiderman to stick to a submarine better.

Citation: Naoe Hosoda and Stanislav N. Gorb, 'Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces', Proceedings of the Royal Society B, Published online before print August 8, 2012, doi: 10.1098/rspb.2012.1297

Breaking Bad Crazy Blue Meth

I am a huge fan of the series Breaking Bad (some spoilers).   I love the Brian Cranston's acting as well as the other characters in the show.  The main characters tragic demise into a world of making crystal meth is astonishing from the first show until the fifth season.  Besides the characters and the plot, I also love the science.  There are several science scenes that would put McGuiver to shame since they help the bad guys (Mr. White and Jesse) get out of situations from making a rudimentary battery, making ricin from beans, building a powerful electromagnet to making better quality methamphetamine. 

Although I do not condone making illicit drugs, the process behind making them and the effects of these drugs is quite interesting..One scene in the episode where Jesse and Mr. White are making meth under the tent in the house that is being fumigated (in Hazard Pay).  It was a beautiful scene where the reactions happening are visualized with sparks and you can see the flow of the reaction.  It makes me want to do more chemistry.

Artists illustration of what chemical reactions look like.  Probably just ink in water.

 It got me thinking of what the surface tension of this blue meth is and how it can help to make better drugs. The surface tension does help in forming the crystalline solids. Crystalline solids are formed by cooling and solidification from the molten (or liquid) state. If you made chocolate this property can be seen easily when the chocolate cools it forms small cocoa butter crystals on the surface after you cook a molten chocolate. This is a first order phase transition. The crystal and melt have an interfacial discontinuity due to a surface tension with a positive surface energy. A metastable parent phase is stable with respect to the nucleation of small embryos or droplets from a daughter phase if their is a positive surface tension. Positive surface tension in this case means the surface of the meth between that of the molten liquid. The surface tension is not a property of the liquid alone but a property of the liquid's interface with another medium. Also the walls of the containers are part of this interface. Where the three surfaces meet (the container wall, the molten meth and the surface) gives a certain contact angle which is the angle the tangent of the surface makes with the solid surface. This surface tension between the liquid-solid surface needs to be positive in order to make crystals.

If one were to make any kind of crystals of a pure substance you would see crystals form at this boundary between the container wall, molten liquid the liquid surface. In you have a smooth surface you can always take a glass stirring rod and scratch this surface. This would allow you to start the nucleation process. Perfect crystals as in Walter White's blue meth would likely grow exceeding slowly. Unlike, Jesse's chilipepper meth (in the first season) he does not add any impurities to the process.  This allows Jesse and Walter to make Heisenberg's Blue stuff.  

Psychonaught Wikicommons

(Surface tension described here would also be good for crystallizing proteins in a better way.  In fact protein crystallographers can use surface tension devices to make better looking crystals).