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hello my name is ella mullikin and i'm a

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graduate student at penn state

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university in the united states

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the work i'm going to describe to you

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today concerns the possibility of the

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origin of life

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at hydrothermal events involving metal

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sulfide catalysts

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as well as coastal droplets which may

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act as prebiotic compartments

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the premise for this idea is the

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well-accepted concept that

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compartmentalization is essential for

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prebiotic chemistry

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in general increasing the concentration

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of chemical reactants will increase

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reaction kinetics and speed up the rate

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of reaction

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compartmentalization is a way of

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decreasing volume and therefore

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increasing concentration

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making reactions between probiotic

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precursors for example more likely

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liquid liquid phase separation or liquid

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phase condensation is one way of forming

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a compartment

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if prebiotic precursors are dispersed

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throughout the entire early earth ocean

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it would be much too dilute for

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biochemistry-like reactions to be

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feasible

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on the other hand compartments like

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coastervates could sequester prebiotic

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molecules and gather a small volume

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the coastal rates that i'm interested in

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specifically are associative or complex

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coaster rates

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meaning that the constituents associate

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with each other through electrostatic

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interactions

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and form a dense polyelectrolyte rich

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phase within a dilute aqueous phase

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due to the release of counter ions when

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the two polyelectrolytes come together

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to form a complex

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this process is entropy driven and

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occurs spontaneously under the right

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conditions including ph

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coastervates were first proposed as a

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player in the origins of life by oparin

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in the early 20th century

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aparra noted the ability of coastervase

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to sequester molecules

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which could then undergo reactions

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within the corrosivate and the ability

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of coastervates to increase in size

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he compared these metabolism and

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growth-like properties to the protoplasm

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of modern cells

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which is not a very good comparison and

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caused the idea of coaster rates in

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origins of life scenarios

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to be discarded for a while however we

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now know that while coaster bates are

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not similar to salt protoplasm

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they are similar to biomolecular

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condensates or membraneless organelles

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also there are features of corrosivates

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which make them worthwhile to consider

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as players in the origins of life

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including varying behavior in different

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environmental conditions like

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temperature or salt concentration

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sequestration of biomolecules and the

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ability to harness natural gradients and

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act as reaction and organizational

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now we will return to the environment

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that this project is focused on which is

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hydrothermal vents

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the images here are from the lost city

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vents which have moderate temperatures

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compared to white smoker and black

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smoker vents

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which get up to hundreds of degrees

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celsius the reason the lost city vents

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are cooler is because they're off axis

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so the vent fluid does not come into

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direct contact with magma

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in contrast to black smoke events which

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have acidic effluent

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losses events are alkaline finally the

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mineral composition of the chimneys is

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different

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with velocity events being ultramafic

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and mostly magnesium and iron olivine

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these minerals undergo serpentinization

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and produce hydrogen gas

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in contrast to the vent fluid the early

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earth ocean was cool and slightly acidic

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containing dissolved co2 and metal ions

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one important feature of black smoker

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vents in particular is that they contain

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hydrogen sulfide in vent fluid

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which can react with aqueous iron in the

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early earth ocean

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to form iron sulfide minerals

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in the late 80s vectors housing proposed

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an iron sulfur world hypothesis of the

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origins of life

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where pyrite minerals catalyze prebiotic

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reactions

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and allow early biomolecules to arrange

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and associate on the mineral surfaces

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the other feature of hydrothermal vent

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chimneys that is interesting for this

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project is pores

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which you can see in this image and they

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can be tens or hundreds of microns in

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diameter

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these pores can facilitate reactions

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within small volumes

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which mix through diffusion rather than

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turbulent mixing due to the geometry of

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the pores

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and due to this also a large amount of

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the fluid is in close proximity to the

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minerals that make up the pore walls

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and may catalyze reactions because of

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the ph

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temperature and solute differences

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between vent fluid and ocean fluid

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these pores would also have ph

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temperature and chemical gradients that

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could provide energy for prebiotic

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reactions

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the different aspects of this scenario

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are represented in this small diagram

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where the acidic ocean fluid and

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alkaline vent fluid enter a microfluidic

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channel and travel with laminar flow

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reactants in the fluids undergo

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reactions catalyzed by the iron sulfur

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minerals

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and may produce polypeptides which can

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then form corrosivates within the force

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the pores have ph and temperature

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gradients due to the different

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conditions of the ocean and vent fluids

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which can further encourage reactions

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within the vent or within the

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corrosorates there

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the first aspect of this i'll focus on

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is the production of crosstalk

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components

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in order to look at the feasibility of

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producing these polypeptides in a

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hydrothermal vent setting

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we return to the iron sulfur world

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hypothesis of vector sauser

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and the iron nickel sulfide cluster

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catalyzed peptide bond formation

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mechanism shown here in the past this

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mechanism has been tested mainly with

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glycine and phenylalanine

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and starting with the simplest amino

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acid glycine we replicated the

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production of glycine dimers

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the next step is to use arginine and

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aspartic acid

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for the associative complex corrosivates

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that i'm interested in

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the constituents need to be oppositely

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charged so they will interact

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electrostatically

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commonly we work with a tender of a

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cationic amino acid

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like arginine and a tender of an anionic

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amino acid like aspartic acid

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here you can see the different charged

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states of arginine which has amine

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groups in its side chain and can have a

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maximum charge of plus two

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we work at a slightly basic ph where it

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has a single positive charge

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and then below you can see four

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different charge states of aspartic acid

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which can have at most a net charge of

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minus two but at slightly basic ph it

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has a single negative charge

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an interesting note for production of

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classified components

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is that the peptide bond formation

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mechanism that we are taking advantage

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of

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amino acid since arginine has extra

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amine groups in its side chain compared

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to something like glycine

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which only has a hydrogen instead of a

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true side chain it may be possible for

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this reaction to form branched

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peptides with arginine although this

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would be undesirable if when we're

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trying to produce biological peptides

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since we're interested in

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polyelectrolytes for coastal rate

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formation

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the next part of this research is an

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investigation into how polypeptide

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coastal rates

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and iron sulfur minerals interact these

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microscope images are of equal charge

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ratios of arginine tender and aspartic

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acid temer

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with iron sulfur mineral the salt is

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relatively high to mimic ocean fluid and

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the solutions were mixed under argon gas

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to replicate

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the anoxic conditions of early earth as

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you can see

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the minerals seem to be encompassed

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within the corrosivates

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with higher mineral concentrations this

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scenario changes so mineral structures

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dominate

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and the coast surveys associate at the

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mineral surfaces

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this is a particularly interesting

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result from the next part of the project

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which is microfluidics an important part

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of the environment that we

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envision these interactions taking place

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in is the micron scale pores of the

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hydrothermal vents

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to replicate and study this in the lab

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we are using microfluidics

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currently we use simple y-shaped

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channels from one inlet we introduce the

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acidic ocean-like fluid containing

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iron-two cations

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and the cationic coastal a constituent

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which is arginine tenomer

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and from the other inlet we introduced

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the alkaline vent like fluid containing

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sulfur anions

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and the anionic coacific constituent

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which is aspartic acid tender

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the microfluidic devices are made of

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pdms and solutions are flowed through

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using a syringe pump

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due to the fluid dynamics and micron

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scale channels there is laminar flow

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which is important for us

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because the solutions will only mix by

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diffusion rather than turbulent mixing

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because of the charge on the pms wall

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and the parabolic nature of the flow

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speeds in such a channel charged species

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will be somewhat more concentrated at

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the walls

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also as the iron and sulfur ions happen

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to meet at the fluid interface at the

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center of the channel

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a metal membrane forms at the interface

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of the two solutions

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this will also be charged and will

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divide the channel into two again

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creating two new parabolic flows and

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concentration patterns

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because of the different ph's of the two

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solutions a ph gradient should form

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to get really close to what might happen

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in hydrothermal vent pores

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i also intend to design a device with a

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temperature gradient

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where the ocean fluid is cold and the

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vent fluid is warm

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as for crossovates if the fluorescence

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microscopy results i showed earlier or

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any indication

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the coaster base should also stick to

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that membrane and become a location for

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other interesting molecules such as rna

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in solution

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to accumulate near a mineral catalyst

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currently we are working on protocols to

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keep samples anoxic

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for a study with confocal microscopy

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raman microscopy x-ray diffraction and

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scanning electron microscopy

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to understand how they classify

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constituents and minerals interact

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in micron scale channels moving forward

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with this project

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the first aim is to produce charge

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polyelectrolytes through the iron sulfur

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mineral catalyzed peptide bond formation

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particularly using arginine and aspartic

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acid

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with both bulk and microfluidic

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experiments we need to characterize the

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iron sulfide minerals that are forming

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and determine their actual surface

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properties such as charge and catalytic

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activity

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part of the difficulty of this step is

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maintaining anoxic conditions

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since iron sulfides will quickly oxidize

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to iron oxides and hydroxides

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under ambient atmospheric conditions

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knowing the surface charge of the

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mineral particles or clusters

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we can then change the charge ratios of

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the polycations and anions that make up

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the phosphates

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to manipulate how they coastavate sweat

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to the minerals

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finally in the microfluidic system we

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will introduce and monitor ph

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redox and thermal gradients to more

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closely mimic hydrothermal vent pores

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and introduce prebiotic and biotic

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molecules like rna

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to see how these conditions combined

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with the presence of cross-servate

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compartments

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can create a type of functional system

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i'd like to conclude by returning to the

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bigger picture of how corrosivates can

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be an important piece of the origins of

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life at hydrothermal vents

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their ability to respond to

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environmental conditions and sequester

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specific prebiotic molecules

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allows for something akin to a selection

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process or at least transient processes

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involving uptake and release

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by becoming enriched in biotic

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precursors and by associating and

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interacting with mineral catalysts like

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pyrite

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they can enhance reaction rates by

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associating with minerals and

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hydrothermal vents particularly

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these corrosivates could prevent the

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escape of prebiotic reaction products

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into the dilute ocean

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and also take advantage of ph redox and

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temperature gradients found in vent

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pores

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coaster vapes may well have been one

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form of an early protocell

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within a larger system of prebiotic

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chemistry co-evolving with biomolecules

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of course none of this work would be

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possible without support from the

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keating group and the house group at

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penn state

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and i particularly want to acknowledge

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seihan che and andrew hyde for their

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direct

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involvement with the work presented here