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Biophysik der Moleküle
kl. Phys. HS Mo 14:00-15:15 u. Do 9:00-10:00
2. Vorlesung Rädler WS 2010
Tutorials: Do 10-11 od. Do 11-12 od. Do 18-19
protein-conformation- the peptide bond
21. Oct. 2010
Monomer/ Oligomere Polymer/Aggregat
Zucker Glucose, Energie, Zellmarker
PolysaccharideStrukturbausteine
Fettsäuren Lipide, FettEnergiespeicher
MembranenKompartmentisierung
Nukleinsäuren ATP, cAMPEnergie, Signalsubstanzen
RNA, DNAInformationsspeicher
Aminosäuren PeptideHormone
Proteine, Enzyme. Motoren, molekulare
Erkennung
Op#scheAk#vitätEsgibtStoffe(z.B.Weinsäure),diediePolarisa#onsebenedeseinfallendenlinearpolarisiertenLichtsbeiDurchgangdurcheineSchichtdicke,l,drehen.
αs:spezifischerDrehwinkel
c:Konzentra#onl:Probenlänge
DerDrehwinkel,α,istbes#mmtdurch:
(Pasteur,1843)
BiologischeRelevanzvonStereoisomerie
Rechts/LinksNatrium‐Ammoniumtartrat
WirkungvonThalidomid(Contergan)
Links‐undrechtsdrehendeAminosäuren
Enan1omere:MolekülediesichzueinanderwieSpiegelbilderverhalten
Optical Rotation Dispersion and Circular Dichroism
210
,lo
m
_ 0
(c)
Schhati. sp.c\a Iot ü ottaeed roronrbi. (r) Ab@rption sF.l.um.(ü) CD Golz li@) ard oRD (dasr.l ti@) sperm ror a positi!€ corlon .flcct.(c) CD and ORD sFclm for. rcgaile Co(on.frccr.
C : lEol(nl - nJ/t dogr€es
d = 2.303(,{L -,4r)180/4,t d€Crees ellipticityoptical rotation
positiveCotton effect
negativeCotton effect
CD spectrum of poly-L-alanin (in a-helix conformation)
9
primarystructure
secondarystructure
tertiarystructure
quarternarystructure
There are 20Amino Acids
• hydrophobicity• polarity• charge
• aromaticity• size and shape
Properties of Amino Acids effect on protein structure
„subnanometerbuilding blocks“sorted by:
side groups:H, methyl, methylene, phenylene
aromatic
usually located on the interior of the protein
forms disulfide bridges
polar groups which cannot ionize easily
smallest amino acid
cyclic ringcreates fixedkink
polar hydoxyl groupsform H-bonds
polar amine groupsform H-bonds
Gly and Pro of particularconformational importance
+
+
- -
-
acidic
basic
imidazolside chain(pH sensitive)
Glu & Asp carboxyl groups
all mainly located at the hydrophilic surface of proteins
Lys & Arg amino groups
21. AA: Selenocystein
22. AA: Pyrrolysine
Selenocystein wird über einen als Rekodierung bezeichneten Mechanismus während der Translation eingebaut
Es gibt mehr als 20 Aminosäuren !
Pyrrolysin kommt in Methan umsetzenden Archaea Bakterien vor
The mesomeric effect 1) forces the atoms of the peptide bond to lie in one plane 2) leads to a strong dipol moment
The petide backbone prefers the trans-conformation
19
20
Steric repulsion limits the freedom of rotation
Ramachandra Plot
green: regime of sterically allowed anglesorange: location of secondary structures
22
primarystructure
secondarystructure
tertiarystructure
quarternarystructure
we need to studythe sterical constraintsand molecular interactions
The structure of the alpha helixis determined by H-bridges
24
The beta-sheet structure
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26
Next challenge -understanding protein folding
Minimization of G=E-TS+PV
Minimize the solvation energy.Decrease the conformational entropy.