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[Music]

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so I'm going to be continuing the lipid

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discussion a little bit although I'm

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going to take a bit of a step back and

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talk about how we can make potential

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lipids I think maybe what we're learning

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most of all is that we're not

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particularly creative picking wikimedia

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slides but the great news is i can skip

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all of my intro and focus on the

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detailed or mechanistic organic

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chemistry um I won't do that um anyway

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so lipids are important membranes are

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important when I'm talking about lipids

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and surfactants we already had a really

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good explanation of this but I tend to

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think about polar head groups and

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nonpolar fatty tails which will

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partition preferentially to the air

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water interface and will also form

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through dimensional structures as we've

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just seen this has a lot of the same

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information that we just thought but

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essentially you've got your simple fatty

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acids that are used as your prebiotic

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irrelevant model systems and then you

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can also make vesicles out of

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phospholipids which are much more

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complex but not particularly prebiotic

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irrelevant a few other things about the

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vesicles that these two systems make

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fatty acids make vesicles but they tend

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to be very pH and salt dependent and

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very sort of conditionally dependent and

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also tend to be a little bit leaky ER

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than phospholipids do whereas

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phospholipid best vesicles form at much

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lower concentrations and are stable

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under many sort of a much wider range of

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conditions but in the absence of the

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inclusions and things that modern life

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has they tend to not allow a lot they

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tend to be very impermeable so one of

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the things that we're thinking about is

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what if we had something that sort of

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explored the chemical space in between

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these two things so you can think about

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phospholipids being robust but not very

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permeable fatty acid vesicles being

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permeable but not very robust but

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there's sort of this wide range of other

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possibilities that we're looking to

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explore and in particular obviously we

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know that the head group of the

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phospholipids is very important but also

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the fact that you can have single tailed

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or double tailed lipids is also

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important so we're

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sort of looking for ways of making

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double tailed lipids and that's where

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prebiotic chemical synthesis comes into

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play and looking at a simple abiotic

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synthesis of multi tailed lipids so when

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we're thinking about this we have to

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pick environmental conditions and as

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many people in this room know our lab

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tends to like to use sunlight and water

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and so the Sun is a really good energy

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source because it is the largest energy

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source even on a prebiotic earth with

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the faint young Sun and all of that it's

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also a low entropy source so you know

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you're not giving off a lot of it tends

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to be very specific and then in terms of

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environments we like water and air water

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interfaces in particular because they

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would have been widely available and

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relatively gentle um so just to talk a

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little bit about the young Sun many

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people know that when we're talking in

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the period of sort of prebiotic chemical

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evolution when we're talking the Sun was

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quite a bit less luminous about 25% less

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luminous than it is today but there was

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still plenty of the UV radiation that is

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sort of high-energy and useful UV

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radiation and more of that high-energy

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UV radiation so not the super

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high-energy stuff we were talking about

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before but the sort of nice near UV

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energy more of that would have reached

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the surface of earth because we didn't

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have oxygen and because we didn't have

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the ozone layer shielding it and so

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we've heard a lot about how that UV

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radiation can destroy things but my

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point is it can also build things up um

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yeah okay and besides the fact that the

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Sun was the largest energy source

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available photochemistry is also

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fundamentally different from thermal

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chemistry thermal chemistry you can

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think about just shaking molecules and

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cooking them to a point where they react

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whereas with photochemistry it's very

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molecule specific and you can excite one

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molecule and the molecule next to it can

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be very can be completely unaffected so

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you don't have to heat stuff up and you

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can get much sort of more high energy

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and out of equilibrium reactions to

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occur than you would get with thermal

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chemistry um and it's also molecule

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specific so you can start with three ml

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fuels that look very similar so you have

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hexanol hexanoic acid and tuoc so

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hexanoic acid and you can see that only

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the two oXXO hexanoic acid with the

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extra carbonyl is absorbing light in the

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near UV region and so it's very molecule

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specific it's also incredibly

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environment specific so these molecules

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so pyruvic acid which may be more

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familiar to biologists as pyruvate when

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it's deprotonated is in the gas phase

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absorbs light about 350 nanometers but

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as soon as you put it in water it blue

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shifts slightly and absorbs at about 320

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nanometers instead so there's a shift

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that occurs but you'll notice that as we

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add an alkyl tail there really isn't

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much shift in the absorption

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cross-section and so it's very much more

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dependent on the functional group than

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it is on the alkyl tail and the

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photochemistry

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that these molecules follow the

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mechanism is completely different in the

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aqueous phase than in the gas phase and

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i'm happy to talk all of the details

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about not going to stick photo chemistry

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if you want but i'm only going to go

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into some of it and so what we've been

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doing over the last few years is going

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through a whole set of these alpha keto

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acids or oxoacids as I will call them

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starting with the shortest which is

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pyruvic acid which just has this little

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methyl tail and then a series of other

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molecules going up to the 12 carbon to

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oxygen ohmic acid I'll be talking mostly

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about 2ak so after Noack acid just

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because you can purchase it from sigma

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and it doesn't have to be custom

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synthesized and so we have a very simple

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photochemical reactor we use a xenon arc

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lamp which is a good solar simulator and

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we just shine light on a solution of our

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molecule in water we can control the

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atmosphere the gas composition of the

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reactor as well but it's a very simple

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setup um but I like a simpler picture of

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what's going on so you have and here I'm

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just showing pyruvic acid because it's

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the easiest one and so you've got

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pyruvic acid floating around in your

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solution but one of the things to keep

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in my

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mind is that pyruvic acid isn't just

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pyruvic acid in solution you also get

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hydration reactions to form the geminal

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diol

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light because you've removed the

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carbonyl chromophore so you have to keep

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in mind that there's an equilibrium

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between the two of these and it's

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dependent on the pH and the

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concentration of the molecules in

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solution what the exact ratio is but you

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still unlike many die carbonyls you

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still retain a lot of your absorptive

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feature and so you can still do lots of

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photo chemistry with your Axio acids

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where you wouldn't with an aldehyde or a

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ketone and so your simple picture looks

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a little bit more like you've got

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pyruvic acid and then the dial floating

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around in solution but if we hit that

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with sunlight we can excite these

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molecules and the excited state so you

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excite to the singlet you undergo inter

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system crossing and internal conversion

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to the triplet state for those of you

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who care and then those molecules can

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react the excited molecule can react

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with the other molecules that are

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floating around in solution and so you

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can undergo a process called hydrogen

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abstraction and you can do this from

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either the dial form or the carbonyl

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form and essentially what you're doing

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is you're making organic radicals in

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solution and there's a series of

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different radicals you can make you can

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hydrogen abstract from the carboxyl

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group or you can hydrogen abstract from

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this methyl group which is something

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we've just shown can happen but you get

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a series of organic radicals and luckily

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we've already heard a lot about radicals

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and essentially what you need to know is

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radicals are really reactive they like

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to run into things and react and here

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I'm showing the oxoacids with their

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alkyl tails back again and it's worth

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noting that I'm demonstrating that the

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hydrogen abstraction has occurred at

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this bethe ch2 group but in theory it

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could occur anywhere along this alkyl

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chain but just for fries the

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presentation I'm showing it that way and

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so if you have a solution where oxygen

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is present or other species you can get

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quenching of these radicals or quenching

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of the triplet state which will

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regenerate your own

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oxoacids so that tends to cut down on

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how much of the product formation you

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see but luckily prebiotic ly we've

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established there isn't a lot of oxygen

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around and so what you get instead is

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recombination to form oligomers

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dominating and they are actually

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oligomers because I've got both divers

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and trimers um and you get this even

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especially in low oxygen environments

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and so if we look at some actual data

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this is just electrospray ionization

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mass spec for to oxygen oeq acid

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so before fatalis we see the oxy

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autonomic acid and it's dial and then

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after Fatah lysis the sort of major peak

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that we see showing up over here is this

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are our tartaric acid derivative so a

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double tailed so a double tailed lipid

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being formed but you'll notice that

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that's not the only product we're

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forming so we we did a quite a bit of

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mechanistic work to figure out what some

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of the other products we were making

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were and so there's other possibilities

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that can happen so instead of just

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getting these radicals you can also have

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an intramolecular reaction that

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essentially kicks off the alkyl tail and

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you regenerate pyruvic acid from your

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longer tailed oXXO acid and essentially

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there are a couple of different

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processes that it can occur where you're

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generating multiple photoactive

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molecules and these oligomeric

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intermediates that are themselves

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photoactive so you've started from a

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single simple molecule in solution but

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you're starting to generate all of these

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molecules that can go and do photo

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chemistry and cross react with each

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other as you as you go and so like this

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is one of one of the very simple

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examples but you can have the pyruvic

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acid that you generated via the norrish

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type ii reaction and it can react with

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the oxygen oeq acid and you could get

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this guy which is still your tartaric

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acid derivative but this time you've got

276
00:10:57,410 --> 00:10:54,600
a six carbon tail and a methyl group and

277
00:10:59,630 --> 00:10:57,420
so there are series of reactions that

278
00:11:01,670 --> 00:10:59,640
can happen like that and so this is as

279
00:11:04,819 --> 00:11:01,680
close to messy chemistry as a physical

280
00:11:07,120 --> 00:11:04,829
chemist is willing to get but you end up

281
00:11:10,810 --> 00:11:07,130
with a series of different isomers

282
00:11:14,680 --> 00:11:10,820
with sing or different different

283
00:11:19,750 --> 00:11:14,690
molecules with one to two to three multi

284
00:11:24,700 --> 00:11:19,760
tails tails for your oligomers that are

285
00:11:26,020 --> 00:11:24,710
forming and all of these and I should

286
00:11:27,490 --> 00:11:26,030
say that all of these could be slightly

287
00:11:28,630 --> 00:11:27,500
different isomers because with mass spec

288
00:11:33,850 --> 00:11:28,640
you you can't tell the difference

289
00:11:35,650 --> 00:11:33,860
between the two but yeah and so we've

290
00:11:37,510 --> 00:11:35,660
got this series of multi tailed

291
00:11:41,230 --> 00:11:37,520
photochemical products and it's sort of

292
00:11:43,420 --> 00:11:41,240
very easy to see this ready formation of

293
00:11:48,220 --> 00:11:43,430
multi tailed lipids even from a simple

294
00:11:50,140 --> 00:11:48,230
single single tailed precursor and then

295
00:11:52,810 --> 00:11:50,150
of course we also have this tartaric

296
00:11:54,370 --> 00:11:52,820
acid derivative which is the main the

297
00:11:57,910 --> 00:11:54,380
main product that we see in the mass

298
00:11:59,290 --> 00:11:57,920
spec and then those of you who are

299
00:12:02,890 --> 00:11:59,300
keeping track at home this is the fourth

300
00:12:04,540 --> 00:12:02,900
year I've put this slide up but as we do

301
00:12:07,120 --> 00:12:04,550
this photo chemistry we also see

302
00:12:08,740 --> 00:12:07,130
self-assembly and so we start with a

303
00:12:10,930 --> 00:12:08,750
clear solution that's below the

304
00:12:14,350 --> 00:12:10,940
aggregation concentration of the lipids

305
00:12:17,410 --> 00:12:14,360
and as fatah lysis proceeds the solution

306
00:12:19,120 --> 00:12:17,420
gets cloudy and we're forming we're

307
00:12:21,130 --> 00:12:19,130
forming aggregates that are spherical in

308
00:12:25,090 --> 00:12:21,140
shape and mono disbursement size and

309
00:12:26,500 --> 00:12:25,100
they're too big to be well so they're

310
00:12:27,960 --> 00:12:26,510
they're too big to sort of be what you

311
00:12:31,150 --> 00:12:27,970
would classically think of as a micelle

312
00:12:33,640 --> 00:12:31,160
and so we have posited in the past that

313
00:12:36,640 --> 00:12:33,650
they are vesicles we've been working to

314
00:12:38,500 --> 00:12:36,650
characterize those more I think it's

315
00:12:39,670 --> 00:12:38,510
worth pointing out that even if they

316
00:12:42,670 --> 00:12:39,680
aren't vesicles it's an interesting

317
00:12:44,350 --> 00:12:42,680
regime of self-assembly where you're

318
00:12:46,750 --> 00:12:44,360
getting these colloidal aggregates that

319
00:12:48,820 --> 00:12:46,760
are mono dispersed in size and spherical

320
00:12:51,160 --> 00:12:48,830
and that lasts for years

321
00:12:53,740 --> 00:12:51,170
in solution so we're sort of working on

322
00:12:56,290 --> 00:12:53,750
that I can add that this happens even

323
00:12:58,360 --> 00:12:56,300
for you're really short to oXXO hexanoic

324
00:13:00,580 --> 00:12:58,370
acid which only has a four carbon tail

325
00:13:02,260 --> 00:13:00,590
as you do Fatah lysis and get these

326
00:13:04,120 --> 00:13:02,270
double tailed or multi tailed products

327
00:13:07,780 --> 00:13:04,130
you see this aggregation occurring as

328
00:13:10,000 --> 00:13:07,790
well and and you see that for the

329
00:13:12,790 --> 00:13:10,010
mixture of oxygen - ox o decanoic acid

330
00:13:15,120 --> 00:13:12,800
we don't see this for pyruvic for for

331
00:13:18,460 --> 00:13:15,130
obvious reasons it's just too short and

332
00:13:20,090 --> 00:13:18,470
I'm working on getting some more

333
00:13:23,000 --> 00:13:20,100
information

334
00:13:24,410 --> 00:13:23,010
about this and I should have if I come

335
00:13:25,700 --> 00:13:24,420
back next year this shouldn't be the

336
00:13:27,260 --> 00:13:25,710
same slide anymore because we've got

337
00:13:31,070 --> 00:13:27,270
some good stuff coming it's just not

338
00:13:33,830 --> 00:13:31,080
quite ready to to share yet um and yeah

339
00:13:36,320 --> 00:13:33,840
and so basically we've been making a

340
00:13:39,350 --> 00:13:36,330
we're sort of exploring this path to

341
00:13:41,450 --> 00:13:39,360
making other molecules with with

342
00:13:45,050 --> 00:13:41,460
sunlight and sort of a very ready

343
00:13:48,200 --> 00:13:45,060
synthesis of multi tailed lipids from

344
00:13:50,150 --> 00:13:48,210
simple periodically relevant precursors

345
00:13:53,060 --> 00:13:50,160
so with that I just like to acknowledge

346
00:14:06,380 --> 00:13:53,070
a group and all of the funding and I'm

347
00:14:08,030 --> 00:14:06,390
happy to take any questions well I got a

348
00:14:09,410 --> 00:14:08,040
question on the way you have any idea

349
00:14:11,510 --> 00:14:09,420
what sort of yields are getting from

350
00:14:13,220 --> 00:14:11,520
this um so we think we're getting so

351
00:14:15,530 --> 00:14:13,230
it's a little hard to tell with it's

352
00:14:19,040 --> 00:14:15,540
easier to tell with pyruvic because the

353
00:14:22,730 --> 00:14:19,050
NMR is much simpler and so with pyruvic

354
00:14:25,340 --> 00:14:22,740
acid under anaerobic conditions for five

355
00:14:28,550 --> 00:14:25,350
hours we get about 90% of the pyruvic

356
00:14:30,530 --> 00:14:28,560
acid is consumed for the oxoacids itself

357
00:14:34,280 --> 00:14:30,540
for the longer tailed ones it's probably

358
00:14:36,050 --> 00:14:34,290
closer to about 30% but it's also harder

359
00:14:39,350 --> 00:14:36,060
to tell so the error bars on that yield

360
00:14:40,880 --> 00:14:39,360
are yeah yeah and that we can really

361
00:14:43,070 --> 00:14:40,890
only monitor the decrease in the

362
00:14:45,320 --> 00:14:43,080
starting material so I don't know the I

363
00:14:48,970 --> 00:14:45,330
don't know the ratio other than relative

364
00:14:52,550 --> 00:14:48,980
mass spec of the products we're making

365
00:14:55,910 --> 00:14:52,560
yeah so the first question is related to

366
00:15:00,010 --> 00:14:55,920
our PWR proposal so if you have ever

367
00:15:03,350 --> 00:15:00,020
experienced the any sort of UV effect on

368
00:15:05,780 --> 00:15:03,360
vesicles so if you know if something

369
00:15:08,000 --> 00:15:05,790
happens on vesicles already formed when

370
00:15:10,310 --> 00:15:08,010
you shine light on them and then I have

371
00:15:13,880 --> 00:15:10,320
another question so we have seen that

372
00:15:16,730 --> 00:15:13,890
phospholipids have two tails so I was

373
00:15:19,850 --> 00:15:16,740
wondering do you think that we

374
00:15:22,850 --> 00:15:19,860
envisioned it was for elation reaction

375
00:15:25,910 --> 00:15:22,860
happening after the formation of a

376
00:15:29,350 --> 00:15:25,920
double tail fatty acid or would you

377
00:15:33,410 --> 00:15:29,360
consider do you think that it first

378
00:15:36,080 --> 00:15:33,420
first a fatty acid is phosphorylated and

379
00:15:38,120 --> 00:15:36,090
it forms the second day yeah so with the

380
00:15:40,010 --> 00:15:38,130
with the sort of first question I

381
00:15:41,870 --> 00:15:40,020
haven't done any work sort of on

382
00:15:44,960 --> 00:15:41,880
vesicles and doing photochemistry on

383
00:15:47,120 --> 00:15:44,970
sort of preformed vesicles although it

384
00:15:48,830 --> 00:15:47,130
it would be interesting and I have some

385
00:15:51,440 --> 00:15:48,840
results that I didn't talk about where

386
00:15:55,070 --> 00:15:51,450
you can also get the cross reaction with

387
00:15:57,230 --> 00:15:55,080
the photoactive oxyacid and a fatty acid

388
00:15:58,370 --> 00:15:57,240
and you can get that cross cross product

389
00:16:00,470 --> 00:15:58,380
as well

390
00:16:02,150 --> 00:16:00,480
so I don't really have an answer to your

391
00:16:04,580 --> 00:16:02,160
first question because I haven't really

392
00:16:09,770 --> 00:16:04,590
done anything with it as to the second

393
00:16:12,620 --> 00:16:09,780
one um let's see uh what was it again

394
00:16:13,880 --> 00:16:12,630
scar I had an answer that it disappeared

395
00:16:15,470 --> 00:16:13,890
yeah if you think that the

396
00:16:18,980 --> 00:16:15,480
phosphorylation reaction happened oh

397
00:16:20,930 --> 00:16:18,990
right right um so I think it would be

398
00:16:22,520 --> 00:16:20,940
hard to phosphorylate the starting

399
00:16:23,870 --> 00:16:22,530
material of the oxoacids because it is

400
00:16:25,490 --> 00:16:23,880
so molecule specific you're going to

401
00:16:27,730 --> 00:16:25,500
change the electronic structure and so

402
00:16:29,750 --> 00:16:27,740
the the mechanistic you know the

403
00:16:33,140 --> 00:16:29,760
excitation and then the photochemistry

404
00:16:34,610 --> 00:16:33,150
that happens may not be the same Bradley

405
00:16:37,430 --> 00:16:34,620
would know more about phosphorylating

406
00:16:39,320 --> 00:16:37,440
the products I think even if you could

407
00:16:40,970 --> 00:16:39,330
phosphorylate the products as we were

408
00:16:42,860 --> 00:16:40,980
talking about earlier the issue is going

409
00:16:44,930 --> 00:16:42,870
to be adding the choline group um I

410
00:16:47,870 --> 00:16:44,940
think because I don't really know how

411
00:16:51,860 --> 00:16:47,880
that would happen yeah

412
00:16:54,880 --> 00:16:51,870
hi I'm just curious about the whether

413
00:16:58,040 --> 00:16:54,890
there is any published or unpublished

414
00:17:01,520 --> 00:16:58,050
robotically available pathways for the

415
00:17:04,580 --> 00:17:01,530
alpha keto acids yeah you proposed

416
00:17:08,900 --> 00:17:04,590
that's my first question and the second

417
00:17:12,170 --> 00:17:08,910
question is when you talk about the

418
00:17:13,790 --> 00:17:12,180
alpha keto acids forming these vesicle

419
00:17:17,060 --> 00:17:13,800
like structure do you know if they're

420
00:17:20,300 --> 00:17:17,070
multilamellar or uni lam lore type of

421
00:17:23,330 --> 00:17:20,310
vesicles yeah yeah okay so the the first

422
00:17:25,400 --> 00:17:23,340
part um so pyruvic acid is a very

423
00:17:28,160 --> 00:17:25,410
probiotic lis relevant molecules at the

424
00:17:29,390 --> 00:17:28,170
shortest one and you can make it in

425
00:17:31,520 --> 00:17:29,400
hydrothermal vents you can make it a

426
00:17:32,990 --> 00:17:31,530
bunch of different ways um and it's been

427
00:17:36,050 --> 00:17:33,000
seen in meteorites and things like that

428
00:17:36,860 --> 00:17:36,060
I believe other oxoacids have also been

429
00:17:38,720 --> 00:17:36,870
seen in meteorites

430
00:17:40,610 --> 00:17:38,730
perhaps not these ones with the alkyl

431
00:17:42,470 --> 00:17:40,620
tails but they are also the right length

432
00:17:45,660 --> 00:17:42,480
for sort of a fisher fisher Tropes

433
00:17:46,980 --> 00:17:45,670
type synthesis as well so i

434
00:17:49,050 --> 00:17:46,990
say a hundred percent that these

435
00:17:50,070 --> 00:17:49,060
specific oxoacids have been seen

436
00:17:53,910 --> 00:17:50,080
periodically but they're certainly

437
00:17:57,780 --> 00:17:53,920
probiotic ly reasonable and then the

438
00:17:59,280 --> 00:17:57,790
second question was oh just talking

439
00:18:01,020 --> 00:17:59,290
about whether we know that they're

440
00:18:06,090 --> 00:18:01,030
lamellar or not we haven't been able to

441
00:18:08,130 --> 00:18:06,100
characterize well we we've been trying

442
00:18:10,140 --> 00:18:08,140
for a long time to get access to a cryo

443
00:18:11,730 --> 00:18:10,150
em2 to see the lamellar structure so we

444
00:18:17,340 --> 00:18:11,740
I don't have any information for you

445
00:18:20,310 --> 00:18:17,350
about that um yeah I don't know I I want

446
00:18:24,900 --> 00:18:20,320
talks about a time of exposure in the

447
00:18:27,690 --> 00:18:24,910
photochemical reaction yeah so of for

448
00:18:30,900 --> 00:18:27,700
how many seconds or minutes or hours you

449
00:18:33,240 --> 00:18:30,910
exposed these biomolecules for further

450
00:18:36,450 --> 00:18:33,250
activation because in evolutionary

451
00:18:39,960 --> 00:18:36,460
history earth was our biomolecules are

452
00:18:43,170 --> 00:18:39,970
we're exposed for the that kind of

453
00:18:45,840 --> 00:18:43,180
physical things for a long period so

454
00:18:48,210 --> 00:18:45,850
what is a probable effect of in we

455
00:18:50,880 --> 00:18:48,220
expose biomolecules for that kind of

456
00:18:53,280 --> 00:18:50,890
physical parameters yeah so so these

457
00:18:56,280 --> 00:18:53,290
particular experiments are five hours

458
00:18:58,800 --> 00:18:56,290
long in the 450 watt xenon arc lamp

459
00:19:01,620 --> 00:18:58,810
that's picked mainly because I can do

460
00:19:03,720 --> 00:19:01,630
that reaction in a day um because it

461
00:19:05,900 --> 00:19:03,730
just works out better um the the

462
00:19:08,220 --> 00:19:05,910
interesting thing to note is that

463
00:19:11,070 --> 00:19:08,230
because stability of your products is

464
00:19:14,790 --> 00:19:11,080
always going to be a question so these

465
00:19:16,620 --> 00:19:14,800
products here with the oxoacids absorb

466
00:19:18,690 --> 00:19:16,630
light but you'll notice that that Axio

467
00:19:20,220 --> 00:19:18,700
acid functionality is not in the

468
00:19:21,420 --> 00:19:20,230
products so they're they don't have

469
00:19:23,820 --> 00:19:21,430
chromophore so they're not going to

470
00:19:26,550 --> 00:19:23,830
absorb light in that near UV region so

471
00:19:28,830 --> 00:19:26,560
they ought to be relatively stable and

472
00:19:30,600 --> 00:19:28,840
UV protected I mean not from really

473
00:19:35,670 --> 00:19:30,610
high-intensity UV light from but at

474
00:19:39,190 --> 00:19:35,680
least from sort of near UV light no no