Biomedical Engineering Reference
In-Depth Information
22.6.2 Lipid/Surfactant Coabsorbants
While.genetic.modiication.can.be.used.to.modify.the.protein.itself.to.improve.surface.bind-
ing.or.charge.transfer.characteristics,.surfactant.molecules.can.be.used.to.pacify.the.excess.
energies.presented.at.the.protein-metal.oxide.interface..Fortunately,.inding.ways.to.main-
tain.the.protein's.integrity.has.long.been.a.topic.of.interest.for.those.performing.structural.
studies. on. them,. and. so. a. number. of. techniques. have. been. and. are. being. developed. to.
stabilize. biomacromolecules. for. spectroscopy. methods. such. as. X-Ray. Diffraction. (XRD),.
Fourier.Transform.Infrared.(FTIR),.and.NMR..Many.of.these.techniques.are.being.adapted.
as.interest.in.biomolecular.hybrid.technology.grows.
Crystallizing.transmembrane.proteins.for.x-ray.characterization.is.one.area.where.surfac-
tants.have.been.used.to.preserve.protein.integrity.outside.of.the.biological.membrane 51
ideally.through.a.selection.of.surfactants.and.liquid.crystal.phases.that.closely.mimic.the.
proteins'. native. surroundings.. It. is. not. unreasonable. to. apply. these. same. techniques. to.
stabilizing.proteins.onto.solid.surfaces..One.novel.application.of.this.scheme.is.forming.a.
lipid-protein.self-assembled.monolayer.onto.an.Attenuated.Total.Relectance.(ATR).sensor.
surface.for.FTIR,.making.it.possible.to.study.protein.orientation,.conformation,.and.dynam-
ics.in.the.presence.of.water. 53. Being.able.to.study.functioning.proteins.adsorbed.onto.a.solid-
state.crystal.has.far-reaching.implications.on.the.viability.of.BSSC.applications.
In.particular,.the.photosynthetic.systems.of.higher.plants,.such.as.PSs.I.and.II,.consist.
of. a. very. complicated. structure;. their. isolation. from. the. natural. environment. has. faced.
signiicant. challenges. due. to. the. tendency. to. aggregate,. denaturation,. and. alteration. of.
their. functional. conformation.. All. these. changes. impair. the. electron. transfer. ability. of.
the.light-harvesting.system.when.utilized.on.photosensitization.studies.of.DSSC.devices..
These.challenges.have.been.addressed.using.surfactants.(i.e.,.chemicals,.lipids,.peptides,.
and.peptide-chemical.hybrid.detergents)..Among.all.the.surfactants,.lipids.and.peptides.
have.been.found.to.have.the.highest.eficacy,.although.their.interactions.with.membrane.
proteins.are.still.under.investigation. 51,53 .Matsumoto.et.al.'s 19 .work.on.PS.I.stabilization.by.
peptide.surfactant.molecules.with.speciic.amino.acid.sequences.proposed.an.interaction.
of. those. molecules. with. the. PS. I. membrane.. They. also. proposed. that. while. the. peptide.
surfactants.act.like.the.standard.chemical.surfactants,.stabilizing.the.transmembrane.pro-
tein.by.aligning.themselves.around.the.membrane.protein,.they.also.encapsulate.the.PS.
I. complex. into. their. own. macrostructure. by. self-assembling. into. a. larger,. 3D. structural.
network,.protecting.PS.I.for.long.periods.of.time..In.accordance.with.their.observations,.
Matsumoto. et. al.. proposed. the. crucial. structural. features. that. are. needed. for. the. pep-
tides. to. be. effective. in. stabilization. of. the. transmembrane. system.. In. addition. to. their.
amphiphilic. properties,. peptide. surfactants. should. contain. an. acetylated. N-terminus,. a.
short. hydrophobic. tail. with. six. consecutive. hydrophobic. amino. acids,. one. or. two. posi-
tively.charged.amino.acids.(i.e.,.lysine.or.arginine).in.the.C-terminus.(not.the.N-terminus),.
and.lastly,.an.amidated.C-terminus.
Similarly,.advances.in.PS.II.structure.determination.in.the.past.several.decades.are.par-
tially.due.to.the.evolution.of.techniques.for.protein.isolation.and.crystallization..However,.
these.techniques.become.increasingly.challenging.to.implement.when.working.with.trans-
membrane.structures.that.have.portions.meant.to.be.stabilized.in.both.the.hydrophobic.
bilayer. interstitial. and. aqueous. intercellular. environments.. To. preserve. PS. II. structural.
integrity.and.functionality,.design.and.implementation.of.protein.isolation,.puriication,.
and.crystallization.will.have.to.take.these.heterogeneities.into.account. 54 .Since.the.1970s,.
detergent.molecules.have.been.a.major.tool.used.to.dissolve.the.cellular.lipid.bilayers.and.
Search WWH ::




Custom Search