BCH 261 Lecture Notes - Lecture 14: Enzyme Kinetics, Linear Form, Zanamivir
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BCH 261 – 121 – Biochemistry
Professor Gagan Gupta
April 12, 2018
Lecture: Review
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Reminders!from!Dr.!Gupta’s!Section!of!the!course.!
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(See!slide)!
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DNA!sequence!manipulation!–!question!on!the!midterm!–!how!do!I!design!PCR!primers?!
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Mutations!–!what’s!happening!at!the!level!of!DNA!and!what!are!the!consequences!of!
different…!
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Protein!purification!–!pi!in!proteins!and!peptides!–!how!do!we!use!that!information?!
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Slide:!!
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How!do!I!design!a!pair!of!PCR!primers?!Many!of!you!had!trouble!with!this.!It!takes!practice.!
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Generically!speaking,!how!would!we!amplify!this!whole!piece!of!DNA?!First,!think,!if!I!have!a!
single!stranded!piece!of!DNA,!!that’s!got!to!be!5’!and!that!3’.!If!only!given!one!strand,!you!can!
assume!it!goes!from!5!to!3’.!
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One!is!easy!to!make!and!the!other!requires!translation.!You!start!with!a!double!stranded!
DNA!that!has!this!polarity.!In!order!to!amplify!it!you!need!one!primer!to!bind!to!each!strand.!
Need!to!amplify!strands!independently.!It’s!the!easiest!because!if!you!design!a!primer!that!
contains!sequence,!10!nucleotides,!that!will!be!complimentary!to!the!bottom!strand.!This!
primer!amplifies!the!bottom!strand.!!
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(See!slide)!
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Slide:'Proteins'and'Peptides'
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Slide:''Immunoglobulin’s'and'Functional'regions'
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You!won’t!have!to!look!at!a!picture!and!interpret!domains!because!I!couldn’t!find!a!good!
printer!to!print,!but!that!doesn’t’!mean!you!don’t!have!to!know!about!domains.!
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This!is!an!example!of!a!heterotetramer!(spelling).!There!are!four!chains,!two!heavy!and!two!
light.!At!the!end!of!the!chains!we!have!a!small!region!called!the!variable!domain!where!the!
antigen!binding!takes!place.!It’s!possible!to!take!an!antibody!and!cleave!it!into!bits!that!still!
retain!function.!These!Fab!fragments!are!still!functional.!There’s!a!single!binding!site!here…!
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Slide:'Protein-Ligand…'
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I!gave!you!serotonin!and!said!if!you!had!to!have!amino!acid!side!chains!to!bind,!where!
would!they!be!and!where!would!they!bind?!All!the!choices!came!from!this!non-polar!
interactions.!Talked!about!ring!stacking.!Could!have!had!the!side!chain!of!losing!stacking!
against!the!chain!–!hydrophobic!interaction.!We!have!the!charge-charge!interactions!and!
the!hydrogen!bonds!is!always!important.!
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Anything!that!binds!a!ligand!must!have!some!way!to!hold!onto!it.!These!are!the!three!
choices.!
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Slide:'Binding'to'Proteins:'Graphical'Analysis'
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Kd!is!the!dissociation!constant!fort!he!protein!ligand!interaction.!Showed!these!two!plots.!
Talked!about!value!θ,!said!that!Kd!=!.5!θ.!That!means!Kd!is!the!concentration!of!ligand!
where!the!protein!is!half!occupied.!
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It’s!hard!to!estimate!a!Kd!from!a!plot!where!you’ve!got!the!linear!plot.!Can!take!your!value!of!
.5!and!if!you!use!the!semi-log!plot!it’s!easy!because!you!just!draw!your!line!across!then!come!
down!to!calculate!the!values.!
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Plots!are!used!to!compare!different!proteins!or!a!single!protein!with!different!kinds!of!
ligand.!
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Slide:!Myoglobin!versus!Hemoglobin!
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Spent!quite!a!bit!of!time!talking!about!oxygen!binding.!Two!proteins!do!that,!hemoglobin!
and!myoglobin.!!Myoglobin!is!the!oxygen!molecule!we!need!in!the!tissue!–!hemoglobin!does!
that!–!the!handoff!is!possible!because!those!two!proteins!bind!oxygen!with!very!different!
affinities.!Partly!has!to!do!with!the!structure!of!protein.!Myoglobin!is!a!monomer!and!
hemoglobin!is!a!tetramer.!
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Slide:'Hemoglobin'Shows…'
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We!looked!at!this!plot!of!concentration!of!oxygen!binding!to!the!protein!as!a!function!of!….5!
would!be!the!point!where!the!protein!is!50%!saturated.!
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If!we!look!at!the!concentration!of!oxygen!in!the!lungs,!it’s!relatively!high,!both!proteins!
would!be!completely!saturated…if!we!go!backwards!and!follow!the!curves…the!lung!
concentration!of!oxygen!is!fully!saturated,!the!tissue!concentration!is!almost!completely!
saturated.!Have!to!get!to!really!low!concentration!of!myoglobin!before!it!gives!up!it’s!
oxygen.!!
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Hemoglobin!is!different.!It’s!our!transporter.!Has!to!take!oxygen!from!lungs!and!transport!to!
the!tissue!where!myoglobin!can!pick!it!up.!Green!line!–!by!the!time!you!get!to!the!
concentration!of!oxygen!in!the!tissue,!hemoglobin!is!only!at!60%!concentration.!Myoglobin!
ready!to!pick!it!up.!
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Why!do!these!binding!curves!look!different?!Concept!of!cooperativity.!In!hemoglobin!a!
tetramer,!as!soon!as!oxygen!binds…sigmoidal!curve.!At!very!low!oxygen!concentrations!it’s!
sluggish,!then!as!soon!as!we!hit!some!threshold!value,!the!affinity!goes!up!and!it’s!easy!to!
Document Summary
Reminders from dr. gupta"s section of the course. (see slide) Mutations what"s happening at the level of dna and what are the consequences of different . First, think, if i have a single stranded piece of dna, that"s got to be 5" and that 3". If only given one strand, you can assume it goes from 5 to 3". One is easy to make and the other requires translation. In order to amplify it you need one primer to bind to each strand. It"s the easiest because if you design a primer that contains sequence, 10 nucleotides, that will be complimentary to the bottom strand. This primer amplifies the bottom strand. (see slide) You won"t have to look at a picture and interpret domains because i couldn"t find a good printer to print, but that doesn"t" mean you don"t have to know about domains. This is an example of a heterotetramer (spelling).