Peptide-based short single β-strand mimics without hydrogen bonding or aggregation

Article abstract of DOI:10.1039/c9cc08378b

Generation of short peptides with a single β-strand structure in solution is difficult. Herein, we design a new class of single β-strand peptidic mimics that are stable without self-aggregation in protic and non-protic solvents. Introduction of one presen

Full text of DOI:10.1039/c9cc08378b

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January 2018
Pages 1-112
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S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
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Pleaseꢀd oC ꢀhn e omt ꢀCa od mj u ms tꢀmarginsꢀ
ꢀ
ꢀ
ꢀ
View Article Online
DOI: 10.1039/C9CC08378B
COMMUNICATIONꢀ
Peptide-basedꢀShortꢀSingleꢀβ-StrandꢀMimicsꢀwithoutꢀHydrogenꢀ
BondingꢀorꢀAggregationꢀ
ꢀ
ꢀ
a
aꢀ
ꢀb
ꢀb
ꢀ a
LuhanꢀZhai, ꢀYukoꢀOtani,* YukikoꢀHori, ꢀTaisukeꢀTomita ꢀandꢀTomohikoꢀOhwada * ꢀ
Receivedꢀ00thꢀJanuaryꢀ20xx,ꢀ
Acceptedꢀ00thꢀJanuaryꢀ20xxꢀ
DOI:ꢀ10.1039/x0xx00000xꢀ
ꢀ
Generationꢀ ofꢀ shortꢀ peptidesꢀ withꢀ singleꢀ β-strandꢀ structureꢀ inꢀ β-α-αꢀtetrapeptide,ꢀandꢀα-α-β-α-αꢀpentapeptideꢀinꢀproticꢀandꢀ
solutionꢀ isꢀ difficult.ꢀ Herein,ꢀ weꢀ designꢀ aꢀ newꢀ classꢀ ofꢀ singleꢀ β- aproticꢀ solvents.ꢀ Unexpectedly,ꢀ theseꢀ β-strandꢀ mimicsꢀ formꢀ
strandꢀpeptidicꢀmimicsꢀthatꢀareꢀstableꢀwithoutꢀself-aggregationꢀinꢀ neitherꢀintermolecularꢀhydrogenꢀbondingꢀnorꢀaggregation,ꢀandꢀ
proticꢀ andꢀ non-proticꢀ solvents.ꢀ Introductionꢀ ofꢀ oneꢀ presentꢀ β- areꢀ stableꢀ inꢀ anꢀ isolatedꢀ state.ꢀ Non-interactingꢀ β-strandꢀ
strandꢀmimicꢀcanꢀinduceꢀandꢀpropagateꢀβ-strandꢀstructureꢀforꢀatꢀ sequenceꢀ inducedꢀ byꢀ aꢀ singleꢀ replacementꢀ ofꢀ Abh-AAꢀ mayꢀ
leastꢀaꢀpenta-peptideꢀsequence.ꢀꢀ
weakenꢀintermolecularꢀβ-strandꢀinteractions,ꢀwhichꢀcanꢀprobeꢀ
theꢀ importanceꢀ ofꢀ β-strand/β-sheetꢀ structuresꢀ inꢀ PPIꢀ orꢀ
β-Strandꢀ isꢀ aꢀ keyꢀ structuralꢀ featureꢀ ofꢀ manyꢀ protein-proteinꢀ aggregation.ꢀ
1
interactionsꢀ(PPIs)ꢀrelevantꢀtoꢀhumanꢀdisease. ꢀAlso,ꢀtheꢀactiveꢀ
sitesꢀofꢀproteaseꢀclasses,ꢀe.g.ꢀaspartic,ꢀserine,ꢀmetallo,ꢀcysteine,ꢀ
andꢀ threonineꢀ endopeptidases,ꢀ wereꢀ foundꢀ toꢀ recognizeꢀ
peptidicꢀ andꢀ non-peptidicꢀ ligandsꢀ inꢀ anꢀ extendedꢀ β-strandꢀ
ꢀ
ꢀ
ꢀ
Aꢀ
Bꢀ
H
Cꢀ
N
O
N
N
R
H
H
ꢀ
O
R
2
H
R
N
H
conformation. ꢀBothꢀsingleꢀβ-strandꢀandꢀβ-sheetꢀsegmentsꢀcanꢀ
R
O
Hꢀ
Hꢀ
NꢀH
N
N
O
O
N
O
mediateꢀPPIs,ꢀwhichꢀmayꢀformꢀhydrogen-bondingꢀinteractionsꢀ
withꢀtheꢀpartnerꢀproteinꢀorꢀinteractꢀexclusivelyꢀwithꢀsideꢀchainꢀ
functionality. ꢀManyꢀofꢀtheꢀreportedꢀworksꢀareꢀfocusingꢀonꢀtheꢀ
H
N
R
OMe
R
O
N
O
N
H
N
H
O
O
O
3
Haoꢀ
H
N
R
R
O
ꢀ
H-bond
N
H
molecularꢀ designꢀ ofꢀ mimickingꢀ hydrogen-bondingꢀ dimericꢀ β-
sheetꢀ structuresꢀ (Figureꢀ 1a),ꢀ stabilizedꢀ byꢀ artificialꢀ hydrogen-
bondꢀ lockꢀ molecules (eg.ꢀ Hao)ꢀ (Figureꢀ 1b).ꢀ However,ꢀ thereꢀ
O
Lockꢀ
ꢀ
4,5
ꢀ
6,7
Single
β-Strand
Mimicꢀ
areꢀfewꢀexamplesꢀofꢀisolatedꢀsingleꢀβ-strandꢀpeptide. ꢀShortꢀ
peptideꢀ segmentsꢀ (3-10ꢀ aminoꢀ acids)ꢀ mediateꢀ manyꢀ
ꢀ
ꢀ
β-Sheet
Mimicꢀ
Native β-sheetꢀ
biomolecularꢀ recognitionꢀ events,ꢀ butꢀ shortꢀ peptidesꢀ Figureꢀ1.ꢀGeneralꢀstrategiesꢀtoꢀstabilizeꢀandꢀformꢀβ-strandꢀstructures:ꢀ
themselvesꢀ rarelyꢀ adoptꢀ well-definedꢀ structuresꢀ inꢀ solution,ꢀ A:ꢀNativeꢀDimericꢀꢀβ-sheetꢀB:ꢀDimericꢀꢀβ-sheetꢀMimicꢀwithꢀhydrogen-
bondingꢀlock;ꢀC:ꢀSingleꢀβ-strandꢀenforcementꢀandꢀpropagation.ꢀ
andꢀ inꢀ particularꢀ aꢀ singleꢀ β-strandꢀ conformationꢀ ofꢀ shortꢀ
peptidesꢀ isꢀ notꢀ stableꢀ inꢀ water. ꢀ Inꢀ thisꢀ work,ꢀ weꢀ foundꢀ thatꢀ
8
Conformationalꢀ studyꢀ ofꢀ C-terminalꢀ substitutedꢀ β((R)/(S)-Abh)-αꢀ
3
α
N
dipeptides.ꢀTheꢀtemperatureꢀdependenceꢀofꢀtheꢀ J(H ,ꢀH )ꢀcouplingꢀ
bothꢀ R-ꢀ orꢀ S-ꢀ bridgehead-substitutedꢀ β-prolineꢀ analogueꢀ (7-
azabicyclo[2.2.1]heptane-2-carboxylicꢀ acid, ꢀ Abhꢀ aminoꢀ acidꢀ
9
constantsꢀ ofꢀ amideꢀ protonsꢀ providesꢀ aꢀ goodꢀ indexꢀ forꢀ evaluatingꢀ
ꢀ
10-11
theꢀ conformationsꢀ ofꢀ peptides.
ꢀ Aminoꢀ acidꢀ dipeptidesꢀ areꢀ inꢀ
(
Abh-AA))ꢀ canꢀ workꢀ asꢀ aꢀ newꢀ scaffoldꢀ forꢀ singleꢀ β-strandꢀ
3
equilibriumꢀ mainlyꢀ amongꢀ α-helixꢀ (αR,ꢀ φꢀ =ꢀ -60°,ꢀ Jꢀ =ꢀ 5.07ꢀ Hz),ꢀ β-
strandꢀ(β,ꢀφꢀ=ꢀ-120°,ꢀ Jꢀ=ꢀ8.5ꢀHz),ꢀandꢀpolyprolineꢀIIꢀ(PII,ꢀφꢀ=ꢀ-75°,ꢀ Jꢀ=ꢀ
.24ꢀHz)ꢀconformations. ꢀExperimentally,ꢀtheꢀ J(H ,ꢀH )ꢀvaluesꢀforꢀ
enforcementꢀ andꢀ propagationꢀ (Figureꢀ 1c).ꢀ Theꢀ bicyclicꢀ β-
prolineꢀaminoꢀacidꢀisꢀhighlyꢀconformationallyꢀconstrainedꢀdueꢀ
toꢀtheꢀtightꢀrestrictionsꢀonꢀalmostꢀallꢀtheꢀmain-chainꢀdihedralꢀ
anglesꢀ(φ,ꢀθꢀandꢀψ,ꢀseeꢀFigureꢀ3(a)),ꢀandꢀtheꢀconformationalꢀ
constraintꢀ inꢀ thisꢀ wayꢀ promotesꢀ andꢀ propagateꢀ β-strandꢀ
formationꢀofꢀβ-αꢀdipeptide,ꢀα-βꢀdipeptide,ꢀα-β-αꢀtripeptide,ꢀα-
3
3
1
2
3
α
N
5
5
β-strandꢀ conformationsꢀ fallꢀ inꢀ theꢀ rangeꢀ fromꢀ 8ꢀ toꢀ 10ꢀ Hz. ꢀ Theꢀ
3
α
N
followingꢀ relationshipꢀ betweenꢀ theꢀ J(H ,ꢀ H )ꢀ couplingꢀ constantꢀ
J(φ))ꢀandꢀtheꢀdihedralꢀangleꢀφꢀofꢀtheꢀrespectiveꢀaminoꢀacidꢀresidueꢀ
(
1
3
2
wasꢀusedꢀinꢀthisꢀstudy:ꢀ ꢀJ(φ)ꢀ=ꢀAꢀcos (φ-60)ꢀ+Bꢀcos(φ-60)ꢀ+ꢀCꢀ,ꢀAꢀ=ꢀ
6
1
.51,ꢀBꢀ=ꢀ-1.76ꢀandꢀCꢀ=ꢀ1.60.ꢀWeꢀperformedꢀ HꢀNMRꢀspectroscopyꢀtoꢀ
obtainꢀresidue-levelꢀdetailsꢀofꢀtheꢀconformationalꢀpreferencesꢀofꢀallꢀ
theꢀhetero-peptides.ꢀꢀ
WeꢀfocusedꢀonꢀAla,ꢀLeuꢀandꢀIleꢀasꢀtheꢀC-terminallyꢀplacedꢀα-aminoꢀ
acids,ꢀ asꢀ theirꢀ sideꢀ chainꢀ bulkinessꢀ increasesꢀ fromꢀ smallꢀ toꢀ largeꢀ
3
o
(
1
Figureꢀ 2).ꢀ Theꢀ Jꢀ couplingꢀ constantꢀ wasꢀ measuredꢀ atꢀ 25 Cꢀ inꢀ d -
ꢀ
ꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Pleaseꢀd oC ꢀhn e omt ꢀCa od mj u ms tꢀmarginsꢀ
Page 2 of 5
COMMUNICATIONꢀ
JournalꢀNameꢀ
3
chloroform.ꢀ Asꢀ shownꢀ inꢀ Figureꢀ 2,ꢀ theꢀ Jꢀ couplingꢀ constantsꢀ ofꢀ C- ForꢀdetailedꢀconformationꢀstudyꢀdataꢀandꢀaꢀdiscussioVniꢀeowfAꢀtrhticeleꢀoOrniglinine ꢀ
terminalꢀsubstitutedꢀanalogues,ꢀBoc-(R)-Abh(OMe)-Leu-OMeꢀ1bꢀandꢀ ofꢀtheꢀrestrictionꢀofꢀ(S)-Abh-α-aminoꢀacid, ꢀD s Oe eI :ꢀ1 t0h . 1e 0ꢀ 3S 9u /pC p9 l Ce Cm 0e 8 n3 t7 a8 r By ꢀ
Boc-(R)-Abh(OMe)-Ile-OMeꢀ 1cꢀ areꢀ largerꢀ thanꢀ 8ꢀ Hz,ꢀ soꢀ 1bꢀ andꢀ 1cꢀ informationꢀ(FigureꢀS2).ꢀ
3
takeꢀ β-strandꢀ conformations.ꢀ Theꢀ Jꢀ couplingꢀ constantꢀ ofꢀ Boc-(R)-
O
Abh(OMe)-Ala-OMeꢀ1aꢀ isꢀaꢀlittleꢀsmallerꢀthanꢀ8ꢀHz,ꢀsuggestingꢀanꢀ
extendedꢀconformation.ꢀ
!
1
O
N
H
N
(a)
O
#1
R
H3C
CH3
N
H
*
"
1
"
!
O
O
HN !2
Boc
N
Boc
N
O
Boc
N
OMe 3J C!-H-NH
=
CH
2
OMe
CH
2
OMe
O
"2
CH
2
2b
1
b’
R
Ac-Leu-NHMe
(in CDCl3 at 298K)
* S
N
* S
N
Ac-Abh(OMe)-Leu-OMe
*
ΔG: kcal/mol
H
H
ΔG: kcal/mol
β:
α:
H
(R)-Abh(OMe)-
O
O
H
ΔG=0.00 (0.00)a
β: ΔG=0.18 min1
PPII: ΔG=0.29 min2
N
O
R= Me 1a 7.4Hz
H
min1
Ala-OMe
O
O
ΔG=0.59 (0.93)a
H
γ:
ΔG=0.00 min3
O
R
(R)-Abh(OMe)-
Leu-OMe
OMe
OMe
1
b
8.4Hz
CHCl3 298K
CHCl3 298K
OMe
8
.1Hz
8.4Hz
4b
PPIIꢀ
1
c
8.4Hz (R)-Abh(OMe)-
βꢀ
3
b
βꢀ
Ile-OMe
ψꢀ2
ψꢀ
Boc-(S)-Abh(OMe)- Boc-(S)-Abh(OMe)-
L)-Leu-OMe
(D)-Leu-OMe
(
conf 6
X
γ-turn
3
αꢀ
Figureꢀ2,ꢀ JꢀCouplingꢀconstantsꢀofꢀC-terminalꢀsubstitutedꢀdipeptides.ꢀ
conf 5
X
Weꢀ nextꢀ examinedꢀ (S)-Abhꢀ aminoꢀ acid-coupledꢀ α-aminoꢀ acidꢀ
dipeptidesꢀBoc-(S)-Abh(OMe)-(L)-Leu-OMeꢀ3b.ꢀWeꢀfoundꢀthatꢀtheꢀ Jꢀ
3
kcal/molꢀ
ϕꢀ
ϕ
ϕ
ꢀ
ꢀ
kcal/molꢀ
2
couplingꢀconstantꢀofꢀ3bꢀinꢀchloroformꢀ(8.1ꢀHz)ꢀisꢀaꢀlittleꢀsmallerꢀthanꢀ
thatꢀofꢀtheꢀcorrespondingꢀ(R)-Abhꢀderivativeꢀ1bꢀ(8.4ꢀHz)ꢀ(Figureꢀ2),ꢀ
suggestingꢀaꢀslightlyꢀhigherꢀpopulationꢀofꢀPPIIꢀconformationꢀ(Figureꢀ
a: calculated by B3LYP 6-31G(d)
(SMD=chloroform)
steric
replusion
steric
replusion
3
),ꢀthoughꢀ3bꢀstillꢀfavorsꢀβ-strandꢀconformation.ꢀToꢀconfirmꢀthatꢀtheꢀ
changeꢀ ofꢀ chiralityꢀ ofꢀ theꢀ Abhꢀ aminoꢀ acidꢀ causesꢀ aꢀ slightꢀ
conformationalꢀchangeꢀofꢀtheꢀC-terminalꢀaminoꢀacid,ꢀweꢀmeasuredꢀ
theꢀ JꢀcouplingꢀconstantsꢀofꢀBoc-(S)-Abh(OMe)-(D)-Leu-OMeꢀ4b,ꢀinꢀ
ꢀ
3
whichꢀtheꢀC-terminalꢀaminoꢀacidꢀisꢀ(D)-Leu,ꢀanꢀenantiomerꢀofꢀ 1b.ꢀ
Theꢀ largeꢀ Jꢀ couplingꢀ constantꢀ valueꢀ ofꢀ 4bꢀ wasꢀ 8.4ꢀ Hzꢀ (Figureꢀ 2),ꢀ
whichꢀisꢀidenticalꢀwithꢀthatꢀofꢀ1b.ꢀꢀ
(b)
3
Boc
H
"
N
*
H
!
N
Boc
!
O
"
H
O
H
H
N
H
N
O
O
*
S
R
Simulationꢀ studyꢀ Toꢀ obtainꢀ moreꢀ detailedꢀ structuralꢀ information,ꢀ
weꢀ carriedꢀ outꢀ molecularꢀ dynamicsꢀ simulationsꢀ ofꢀ Ac-(R)-
Abh(OMe)-Leu-OMeꢀ 1b’ꢀ (forꢀ convenience,ꢀ theꢀ Bocꢀ groupꢀ ofꢀ theꢀ
originalꢀstructureꢀ1bꢀisꢀsimplifiedꢀtoꢀanꢀAcꢀgroupꢀinꢀ1b’).ꢀToꢀevaluateꢀ
theꢀ restrictingꢀ effectꢀ ofꢀ theꢀ bicyclicꢀ scaffoldꢀ (Abh-AA)ꢀ onꢀ theꢀ C-
terminalꢀ side,ꢀ weꢀ comparedꢀ theꢀ energyꢀ landscapeꢀ ofꢀ Ac-(R)-
Abh(OMe)-Leu-OMeꢀ 1b’ꢀ (Figureꢀ 3(a))ꢀ withꢀ respectꢀ toꢀ theꢀ main-
chainꢀ dihedralꢀ anglesꢀ ψꢀ andꢀ φ,ꢀ obtainedꢀ byꢀ metadynamicsꢀ
simulations,ꢀ withꢀthatꢀofꢀtheꢀsimpleꢀLeuꢀdipeptideꢀ(Ac-Leu-NHMe)ꢀ
O
OMe
O
OMe
Boc-Val-(R)-AbhOMe-COOMe
Boc-Val-(S)-AbhOMe-COOMe
5
a’
5b’
parallel
β sheet
parallel
β sheet
anti-parallel
β sheet
anti-parallel
β sheet
ψꢀ
ψꢀ
ψꢀ
kcal/mol
kcal/mol
ϕꢀ
ϕꢀ
ꢀ
Figureꢀ 3.ꢀ Atomꢀ color:ꢀ C:ꢀ green;ꢀ H:ꢀ purple;ꢀ N:ꢀ blue;ꢀ O:ꢀ red.ꢀ (a)ꢀ Energyꢀ
landscapeꢀ ofꢀ 1b’ꢀ andꢀ Ac-Leu-NHMeꢀ 2b’ꢀ withꢀ respectꢀ toꢀ theꢀ main-chainꢀ
2
bꢀ (Figureꢀ 3ꢀ (a),ꢀ seeꢀ alsoꢀ Figureꢀ S1,ꢀ Supportingꢀ graphics,ꢀ withꢀ aꢀ
differentꢀ energyꢀ level).ꢀ Fromꢀ theꢀ energyꢀ map,ꢀ 1b’ꢀ showedꢀ aꢀ highꢀ
dihedralꢀ anglesꢀ ψꢀ andꢀ φ.ꢀ (b)ꢀ Energyꢀ landscapeꢀ ofꢀ Boc-Val-(R)-AbhOMe-
populationꢀ inꢀ oneꢀ energyꢀ minimumꢀ region,ꢀ correspondingꢀ toꢀ β-
2 2
CO Meꢀ5a’ꢀandꢀBoc-Val-(S)-AbhOMe-CO Meꢀ5b’ꢀinꢀchloroformꢀatꢀ298K.ꢀTheꢀ
strandꢀconformationꢀ(φ2=ꢀ-150°~ꢀ-90°,ꢀψ2=ꢀ150°)ꢀꢀ(Figureꢀ3ꢀ(a)).ꢀOnꢀ redꢀarrowsꢀshowꢀtheꢀproximityꢀbetweenꢀtheꢀα-protonꢀofꢀValꢀandꢀbridgeheadꢀ
theꢀ otherꢀ hand,ꢀ 2bꢀ showsꢀ threeꢀ energyꢀ minima,ꢀ reflectingꢀ anꢀ protonꢀofꢀAbhꢀaminoꢀacid.ꢀꢀ
equilibriumꢀamongꢀβ,ꢀPPIIꢀandꢀγ-turn,ꢀwithꢀtheꢀgreatestꢀpopulationꢀ
inꢀtheꢀγ-turnꢀconformationꢀ(Figureꢀ3(a)).ꢀAsꢀcomparedꢀwithꢀ2b,ꢀ1b’ꢀ Conformationalꢀ studyꢀ ofꢀ N-terminalꢀ substitutedꢀα-β((R)/(S)-Abh-
hasꢀ aꢀ limitedꢀ numberꢀ ofꢀ energyꢀ minima,ꢀ i.e.,ꢀ fewerꢀ accessibleꢀ AA)ꢀ dipeptidesꢀ Weꢀ examinedꢀ theꢀ conformationꢀ ofꢀ α-aminoꢀ acidsꢀ
minimumꢀconformations,ꢀindicatingꢀthatꢀtheꢀbicyclicꢀscaffoldꢀ(Abh- coupledꢀwithꢀ(R)-ꢀorꢀ(S)-AbhꢀaminoꢀacidꢀonꢀtheꢀN-terminalꢀside.ꢀWeꢀ
AA)ꢀ imposesꢀ conformationalꢀ restrictionsꢀ onꢀ theꢀ C-terminalꢀ conductedꢀ metadynamicsꢀ simulationsꢀ ofꢀ Boc-Val-(R)-AbhOMe-
substitutedꢀα-aminoꢀacid.ꢀꢀ
COOMeꢀ5a’ꢀandꢀBoc-Val-(S)-AbhOMe-COOMeꢀ5b’ꢀ(Figureꢀ3(b),ꢀseeꢀ
alsoꢀ Supportingꢀ graphics,ꢀ Figureꢀ S3ꢀ withꢀ aꢀ differentꢀ energyꢀ level).ꢀꢀ
Originꢀ ofꢀ theꢀ conformationalꢀ restrictionsꢀ Toꢀ seeꢀ howꢀ theꢀ C- Theꢀ resultsꢀ suggestedꢀ thatꢀ 5a’ꢀ andꢀ 5b’ꢀ bothꢀ favorꢀ β-strandꢀ
terminalꢀ restrictionꢀ isꢀ induced,ꢀ weꢀ analyzedꢀ twoꢀ possibleꢀ high- conformations,ꢀ butꢀ 5a’ꢀ favorsꢀ parallelꢀ β-strandꢀ conformationꢀ toꢀ aꢀ
o
energyꢀconformationsꢀ(confꢀ5ꢀandꢀconfꢀ6)ꢀinꢀFigureꢀ3(a).ꢀInꢀfoldedꢀ greaterꢀ extentꢀ (φ=-120 ,ꢀ ψ=115°),ꢀ whileꢀ 5b’ꢀ favorsꢀ anti-parallelꢀ β-
o
conformerꢀ5,ꢀthereꢀisꢀstericꢀhindranceꢀbetweenꢀtheꢀsideꢀchainꢀofꢀtheꢀ strandꢀ conformationꢀ toꢀ aꢀ greaterꢀ extentꢀ (φ=-140 ,ꢀ ψ=135°).ꢀ
3
C-terminalꢀaminoꢀacidꢀandꢀprotonsꢀonꢀtheꢀbicyclicꢀringꢀ(conformerꢀ5,ꢀ Experimentally,ꢀ thisꢀ isꢀ supportedꢀ byꢀ theꢀ magnitudesꢀ ofꢀ theꢀ Jꢀ
3
Figureꢀ3(a)).ꢀꢀInꢀtheꢀotherꢀfoldedꢀconformerꢀ6ꢀ(Figureꢀ3(a)),ꢀthereꢀisꢀ couplingꢀconstants:ꢀtheꢀ JꢀcouplingꢀconstantsꢀofꢀtheꢀValꢀresidueꢀinꢀ
stericꢀhindranceꢀbetweenꢀtheꢀmainꢀchainꢀofꢀtheꢀC-terminalꢀaminoꢀ 5aꢀinꢀchloroformꢀatꢀ25°Cꢀandꢀ0ꢀ°Cꢀ(9.2ꢀHz,ꢀ9.2ꢀHz)ꢀareꢀaꢀlittleꢀsmallerꢀ
acidꢀandꢀprotonsꢀonꢀtheꢀbicyclicꢀring.ꢀTherefore,ꢀonlyꢀextendedꢀβ- thanꢀ thoseꢀ ofꢀ 5bꢀ inꢀ chloroformꢀ atꢀ 25°Cꢀ andꢀ 0ꢀ °Cꢀ (9.5ꢀ Hz,ꢀ 9.4ꢀ Hz)ꢀ
strandꢀ conformationꢀ isꢀ favored,ꢀ andꢀ theꢀ bulkierꢀ theꢀ sideꢀ chainꢀ is,ꢀ (Figureꢀ4).ꢀThus,ꢀ(R)/(S)-Abhꢀaminoꢀacidsꢀcanꢀbothꢀenforceꢀβ-strandꢀ
theꢀ strongerꢀ theꢀ restrictionꢀ onꢀ theꢀ C-terminalꢀ aminoꢀ acidꢀ willꢀ be.ꢀ conformationꢀonꢀtheꢀα-aminoꢀacidꢀatꢀtheꢀN-terminalꢀside.ꢀTheꢀNMRꢀ
2
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
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Pleaseꢀd oC ꢀhn e omt ꢀCa od mj u ms tꢀmarginsꢀ
JournalꢀNameꢀ
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studyꢀindicatedꢀthatꢀtheꢀbridgeheadꢀprotonꢀisꢀcloseꢀtoꢀtheꢀα-protonꢀ betweenꢀ-3ꢀtoꢀ-5ꢀppb/K,ꢀindicatingꢀaꢀweakꢀhydrogenꢀVbieownAdr.tꢀicTlehOeꢀnVlinTe-
ofꢀ theꢀ α-aminoꢀ acid,ꢀ dueꢀ toꢀ theꢀ characteristicꢀ upward-projectingꢀ NMRꢀspectraꢀofꢀ6aꢀandꢀ6bꢀareꢀshownꢀinꢀFigu Dr eO sI :ꢀ S1 50 ꢀ. (1 a0 )3ꢀ a9 /n Cd 9ꢀ (Cb C) .0ꢀ 8378B
directionꢀ ofꢀ theꢀ bridgeheadꢀ proton,ꢀ andꢀ thisꢀ proximityꢀ wouldꢀ
1
4
3
J H#-NH 3J H#-NH 3J H#-NH
at 0oC at 10oC
3J H#-NH 3J H#-NH 3J H#-NH
influenceꢀtheꢀmainꢀchainꢀrotationꢀofꢀtheꢀadjacentꢀα-aminoꢀacid. ꢀ
Tripeptides
o
at 25oC at 0oC at 10oC
at 25 C
NHBoc in CDCl3 in CDCl3in CD OH
NHBoc in CDCl3 in CDCl3in CD OH
3
3
H
H
O
(Hz)
(Hz)
(Hz)
O
(Hz)
(Hz)
(Hz)
Conformationalꢀ studyꢀ ofꢀ α-β-αꢀ tripeptidesꢀ Sinceꢀ β-strand-likeꢀ
extendedꢀconformationꢀisꢀstabilizedꢀonꢀbothꢀC-ꢀandꢀN-sidesꢀofꢀtheꢀ
Abhꢀaminoꢀacid,ꢀweꢀnextꢀsynthesizedꢀα-β-αꢀtripeptides,ꢀꢀBoc-Val-(R)-
Abh-Leu-OMeꢀ5aꢀandꢀBoc-Val-(S)-Abh-Leu-OMeꢀ5bꢀ(Figureꢀ4),ꢀandꢀ
Val 9.2
9.2
9.3
Val 9.5
9.4
8.6
N
N
O
O
*
S
*
R
O
O
HN
O
Leu
8.1
3
HN
O
Leu 8.0
7.9
7.2
8
.5
O
8.4
H
O
J H#-NH
o
H
O
at 25 C
in CDCl3
(Hz)
examinedꢀtheirꢀstructureꢀandꢀconformationalꢀrigidityꢀ(Figureꢀ4).ꢀInꢀ
NHBoc
H
5
a
5b
!-strand
3
O
5
a,ꢀ theꢀ Jꢀ couplingꢀ constantsꢀ ofꢀ theꢀ Valꢀ andꢀ Leuꢀ moietiesꢀ inꢀ d
1
-
!-strand
N
Leu 9.4
chloroformꢀareꢀ9.2ꢀHzꢀandꢀ8.4ꢀHzꢀ(atꢀ0°C)ꢀandꢀ9.2ꢀHzꢀandꢀ8.5ꢀHzꢀꢀ(atꢀ
*
S
o
o
2
5°C),ꢀ respectively.ꢀ Bothꢀ areꢀ largerꢀ thanꢀ 8ꢀ Hzꢀ atꢀ 0ꢀ Cꢀ andꢀ 25ꢀ C,ꢀ
O
HN
D-Leu 8.3
suggestingꢀthatꢀtheꢀValꢀandꢀLeuꢀmoietiesꢀadoptꢀβ-strandꢀstructures.ꢀ
O
H
3
Inꢀ5b,ꢀtheꢀ JꢀcouplingꢀconstantsꢀofꢀtheꢀValꢀandꢀLeuꢀmoietiesꢀinꢀd
1
-
O
5c !-strand
Tetrapeptides
chloroformꢀareꢀ9.4ꢀHzꢀandꢀ7.9ꢀHzꢀ(atꢀ0°C)ꢀandꢀ9.5ꢀHzꢀandꢀ8.0ꢀHzꢀꢀ(atꢀ
3
3
3
3
J H#-NH ∆ $/∆T
J H#-NH
J H#-NH ∆ $/∆T
J H#-NH
o
o
o
o
o
at 0 C
in CD3OH
(Hz)
at 0 C
2
5°C),ꢀrespectively,ꢀwhichꢀareꢀlargerꢀthanꢀorꢀcloseꢀtoꢀ8ꢀHzꢀatꢀ0ꢀ Cꢀ
at 25 C (ppb/ K)
in CDCl3 in CDCl3
at 25 C (ppb/ K)
o
NHBoc
O
H
N
NHBoc
in CDCl3 in CDCl3 in CD OH
3
andꢀ 25ꢀ C,ꢀ indicatingꢀ β-strand-likeꢀ extendedꢀ structuresꢀ ofꢀ bothꢀ
moieties.ꢀWeꢀalsoꢀmeasuredꢀtheꢀ H-NMRꢀspectraꢀofꢀ5aꢀandꢀ5bꢀinꢀaꢀ
polarꢀsolvent,ꢀd
(Hz)
O
(Hz)
(Hz)
1
Ala 1 8.4
-3.7
6.7
H
Ala 1 6.6
-2.7
-8.3
6.3
N
H
3
O
O
N/A
*
S
!-Ala N/A
3
-methanol.ꢀTheꢀ JꢀcouplingꢀconstantsꢀofꢀtheꢀValꢀandꢀ
O
NH
O
NH
Leuꢀmoietiesꢀinꢀ5aꢀareꢀ9.3ꢀHzꢀandꢀ8.1ꢀHzꢀ(atꢀ10°C)ꢀrespectively.ꢀTheyꢀ
Ala 2 7.4
Val 8.7
-11.7
-5.4
6.4
8.4
-6.7
6.2
8.3
O
Ala 2 6.5
O
O
H
HN
H
Val
areꢀstillꢀlargerꢀthanꢀ8ꢀHz,ꢀsupportingꢀaꢀgoodꢀβ-strand-formingꢀability.ꢀ
HN
9.1
-5.5
3
H
O
Inꢀ theꢀ caseꢀ ofꢀ 5b,ꢀ theꢀ Jꢀ couplingꢀ constantsꢀ ofꢀ theꢀ Valꢀ andꢀ Leuꢀ
H
O
O
6a !-strand
3
J H#-NH ∆ $/∆T
at 25 C (ppb/ K) at 10 C
in CDCl3 in CDCl3 in CD OH
3
Hz)
3
J H#-NH
o
6b Random coil
moietiesꢀ areꢀ 8.6ꢀ Hzꢀ andꢀ 7.2ꢀ Hzꢀ (atꢀ 10°C),ꢀ respectively,ꢀ suggestingꢀ
thatꢀ β-strand-likeꢀ extendedꢀ structure.ꢀ Forꢀ bothꢀ 5aꢀ andꢀ 5b,ꢀ theꢀ
solventꢀ dependencyꢀ wasꢀ weak.ꢀ Theseꢀ resultsꢀ suggestꢀ thatꢀ theꢀ
overallꢀconformationalꢀconstraintꢀinducedꢀbyꢀtheꢀAbhꢀaminoꢀacidꢀisꢀ
essentiallyꢀ independentꢀ ofꢀ theꢀ polarityꢀ ofꢀ theꢀ solvent.ꢀ Next,ꢀ weꢀ
o
Pentapeptide
NHBoc
(
(Hz)
H
Val 1
O
8
.6
-2.9
-4.3
8.7
HN
O
H
Ala 1
7.8
7.3
N
3
O
examinedꢀ5c,ꢀwhichꢀcontainsꢀbothꢀD-ꢀandꢀL-Leuꢀ(Figureꢀ4).ꢀTheirꢀ Jꢀ
R
O
*
couplingꢀ constantsꢀ areꢀ 9.4ꢀ andꢀ 8.3ꢀ Hz,ꢀ respectively,ꢀ suggestingꢀ β-
strandꢀconformation.ꢀThus,ꢀtheꢀAbhꢀaminoꢀacidꢀcanꢀalsoꢀstabilizeꢀβ-
strandꢀstructureꢀofꢀD-ꢀandꢀL-ꢀaminoꢀacid-containingꢀsequences.ꢀAllꢀ
theꢀchemicalꢀshiftsꢀofꢀα-protonsꢀofꢀtheꢀα-aminoꢀacidꢀresiduesꢀforꢀ1a,ꢀ
HN
Ala 2 7.7
-8.1
-5.0
7.0
8.9
H
O
NH
Val 2
8.8
H
O
O
7a
!
-strand
1
b,ꢀ1c,ꢀ3b,ꢀ4b,ꢀ5a,ꢀ5bꢀandꢀ5cꢀareꢀdownꢀfieldꢀshifted,ꢀasꢀcomparedꢀ
3
Figureꢀ4.ꢀ Jꢀcouplingꢀconstantꢀofꢀ5a,ꢀ5b,ꢀ5c,ꢀ6a,ꢀ6bꢀandꢀ7a.ꢀ
withꢀtheꢀrandomꢀcoil,ꢀindicatingꢀextendedꢀstructuresꢀ(seeꢀTableꢀS1).ꢀꢀꢀ
Conformationꢀ studyꢀ ofꢀ α-α-β-α-αꢀ pentapeptidesꢀ Theꢀ extendedꢀ
structureꢀofꢀα/βꢀpeptidesꢀcanꢀbeꢀreadilyꢀelongatedꢀtoꢀpentapeptideꢀ
Conformationꢀstudyꢀofꢀα-β-α-αꢀtripeptidestetrapeptidesꢀNext,ꢀtwoꢀ
tetrapeptideꢀ sequencesꢀ Boc-Ala-(S)-Abh-Ala-Val-OMeꢀ 6aꢀ andꢀ Boc-
Ala-β-Ala-Ala-Val-OMeꢀ6b,ꢀwereꢀsynthesizedꢀ(Figureꢀ4),ꢀtheꢀlatterꢀasꢀ
(
α-α-β-α-α).ꢀ (Figureꢀ 4)ꢀ Inꢀ pentapeptideꢀ 7aꢀ (Boc-Val1-Ala1-(R)-Abh-
3
Ala2-Val2-OMe),ꢀweꢀalsoꢀobserveꢀlargeꢀ Jꢀcouplingꢀconstantsꢀforꢀα-
3
aꢀreferenceꢀcompound.ꢀInꢀ6a,ꢀtheꢀ Jꢀcouplingꢀconstantsꢀofꢀα-aminoꢀ
aminoꢀacidꢀresiduesꢀVal1,ꢀAla1,ꢀAla2ꢀandꢀVal2,ꢀwhichꢀisꢀ8.6,ꢀ7.8,ꢀ7.7ꢀ
acidꢀresiduesꢀinꢀCDCl
suggestingꢀaꢀβ-strand-likeꢀextendedꢀconformation.ꢀHowever,ꢀtheꢀ Jꢀ
couplingꢀ constantꢀ valuesꢀ ofꢀ theꢀ α-aminoꢀ acidꢀ residuesꢀ inꢀ CD OHꢀ
becomeꢀsmallerꢀ(6.7,ꢀ6.4ꢀandꢀ8.4ꢀHz),ꢀindicatingꢀsomeꢀsolventꢀeffect.ꢀ
3
ꢀatꢀ25ꢀ°Cꢀareꢀ8.4,ꢀ7.4ꢀandꢀ8.7ꢀHz,ꢀ(Figureꢀ4),ꢀ
o
andꢀ8.8ꢀHzꢀrespectively,ꢀatꢀ60ꢀ Cꢀinꢀchloroformꢀ(seriousꢀoverlappingꢀ
3
o
o
ofꢀNHsꢀisꢀdetectedꢀatꢀ25ꢀ C)ꢀandꢀ8.7,ꢀ7.3,ꢀ7.0ꢀandꢀ8.9ꢀHzꢀatꢀ10ꢀ Cꢀinꢀ
methanol,ꢀ suggestingꢀ aꢀ β-strand-likeꢀ extendedꢀ structureꢀ andꢀ littleꢀ
solventꢀeffect.ꢀTheꢀtemperatureꢀcoefficientꢀvaluesꢀforꢀα-aminoꢀacidꢀ
residuesꢀVal1,ꢀAla1,ꢀAla2ꢀandꢀVal2,ꢀwhichꢀisꢀ-2.9ꢀppb/K,ꢀ-4.3ꢀppb/K,ꢀ-
3
5
3
Accordingꢀtoꢀaꢀpreviousꢀreportꢀ ,ꢀ Jꢀcouplingꢀconstantꢀvaluesꢀforꢀanꢀ
unstructuredꢀrandomꢀcoilꢀrangeꢀfromꢀ5.8ꢀtoꢀ7.3ꢀHz.ꢀInꢀ6b,ꢀbasedꢀonꢀ
8
.1ꢀppb/Kꢀandꢀ-5.0ꢀppb/Kꢀrespectively,ꢀmayꢀindicateꢀweakꢀhydrogenꢀ
3
theꢀ Jꢀ couplingꢀ constantꢀ valuesꢀ ofꢀ theꢀ α-aminoꢀ acidꢀ residuesꢀ inꢀ
bondingꢀformingꢀability,ꢀparticularlyꢀofꢀVal1.ꢀInꢀtheꢀVT-NMRꢀofꢀ7aꢀ
o
CDCl
3
ꢀatꢀ25ꢀ Cꢀ(6.6,ꢀ6.5ꢀandꢀ9.1ꢀHz,ꢀFigureꢀ4),ꢀtetrapeptideꢀ6bꢀmayꢀ
3
(
Figureꢀ 5ꢀ (a)),ꢀ theꢀ temperature-dependentꢀ changeꢀ ofꢀ Jꢀ couplingꢀ
takeꢀ aꢀ randomꢀ coilꢀ structure.ꢀ Theꢀ chemicalꢀ shiftꢀ ofꢀ amideꢀ NHꢀ
protonsꢀgenerallyꢀdisplaysꢀaꢀtemperatureꢀdependenceꢀthatꢀcanꢀbeꢀ
usedꢀ toꢀ getꢀ informationꢀ onꢀ theꢀ presenceꢀ andꢀ theꢀ stabilityꢀ ofꢀ
constantsꢀ ofꢀ theꢀ α-aminoꢀ acidꢀ residuesꢀ isꢀ smallꢀ overꢀ aꢀ 15-degreeꢀ
temperatureꢀrange,ꢀexceptꢀAla1.ꢀTheꢀconcentrationꢀofꢀ6a,ꢀ6bꢀandꢀ7aꢀ
inꢀ thisꢀ temperature-dependencyꢀ experimentꢀ wasꢀ aroundꢀ 60ꢀ mM,ꢀ
whichꢀwouldꢀbeꢀsufficientlyꢀhighꢀtoꢀdetectꢀintermolecularꢀhydrogenꢀ
bondꢀ formation,ꢀ ifꢀ itꢀ occurred.ꢀ Weꢀ alsoꢀ carriedꢀ outꢀ ROESYꢀ
measurement,ꢀ becauseꢀ inꢀ anꢀ antiparallel-sheetꢀ structure,ꢀ
interstrandꢀ NOE/ROEꢀ effectsꢀ areꢀ generallyꢀ observedꢀ betweenꢀ theꢀ
sideꢀchainsꢀandꢀbetweenꢀtheꢀamideꢀhydrogenꢀatomsꢀofꢀtheꢀpairingꢀ
1
5
hydrogenꢀbonds.ꢀInꢀnon-polarꢀsolventsꢀsuchꢀasꢀchloroform, ꢀifꢀtheꢀ
coefficientꢀ ofꢀ theꢀ temperatureꢀ dependenceꢀ ofꢀ theꢀ chemicalꢀ shiftꢀꢀ
changeꢀofꢀtheꢀamideꢀNHꢀprotonsꢀliesꢀbetweenꢀ0ꢀandꢀ-3ꢀppb/K,ꢀthisꢀisꢀ
suggestiveꢀ ofꢀ theꢀ presenceꢀ ofꢀ aꢀ strongꢀ intramolecularꢀ hydrogenꢀ
bond.ꢀ Temperatureꢀ coefficientsꢀ betweenꢀ -5ꢀ andꢀ -3ꢀ ppb/Kꢀ areꢀ
indicativeꢀ ofꢀ aꢀ weakꢀ intramolecularꢀ hydrogenꢀ bond.ꢀ Temperatureꢀ
coefficientsꢀsmallerꢀthanꢀ-5ꢀppb/Kꢀimplyꢀtheꢀlackꢀofꢀanyꢀintra-ꢀ(orꢀ
inter-)ꢀmolecularꢀhydrogenꢀbond.ꢀInꢀtheꢀcaseꢀofꢀ6a,ꢀtheꢀtemperatureꢀ
coefficientꢀvaluesꢀforꢀAla2ꢀandꢀValꢀareꢀ-11.7ꢀandꢀ-5.4ꢀppb/Kꢀ(Figureꢀ
5
residues ,ꢀ butꢀ weꢀ couldꢀ notꢀ detectꢀ anyꢀ suchꢀ correlation.ꢀ Theꢀ
concentrationꢀ dependencyꢀ ofꢀ circularꢀ dichroismꢀ (CD)ꢀ (Figureꢀ 5(b))ꢀ
representsꢀ additionalꢀ evidenceꢀ forꢀ theꢀ absenceꢀ ofꢀ intermolecularꢀ
hydrogenꢀ bondingꢀ andꢀ aggregation.ꢀ Theꢀ CDꢀ spectrumꢀ forꢀ 7aꢀ inꢀ
methanolꢀshowsꢀoneꢀbandꢀofꢀpositiveꢀellipticityꢀatꢀ202ꢀnmꢀandꢀoneꢀ
minimaꢀofꢀnegativeꢀellipticityꢀatꢀ224ꢀnm,ꢀwhichꢀcorrespondsꢀtoꢀβ-
4
),ꢀexcludingꢀtheꢀpossibilityꢀthatꢀaꢀstableꢀhydrogenꢀbondꢀisꢀformed.ꢀ
Theꢀ temperatureꢀ coefficientꢀ valueꢀ forꢀ Ala1ꢀ ofꢀ 6aꢀ isꢀ -3.7,ꢀ whichꢀ isꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ3ꢀ
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Pleaseꢀd oC ꢀhn e omt ꢀCa od mj u ms tꢀmarginsꢀ
Page 4 of 5
COMMUNICATIONꢀ
JournalꢀNameꢀ
strandꢀ conformation.ꢀ Theꢀ solventꢀ effectꢀ andꢀ temperatureꢀ theꢀ C-terminusꢀ foundꢀ inꢀ 40-aminoꢀ acidꢀ residueꢀ β-amyloidꢀ fibril,ꢀ
View Article Online
1
6
dependencyꢀofꢀCDꢀisꢀshownꢀinꢀFiguresꢀS9-S11.ꢀꢀ
determinedꢀbyꢀNMRꢀanalysisꢀ(PDBꢀcode:ꢀ2L DM OP I ): 1 0. ꢀ. T1 0h 3e 9ꢀ /p Cr 9e Cd Co m0 8i 3n 7a 8nB tꢀ
structureꢀ ofꢀ 7aꢀ showsꢀ veryꢀ goodꢀ extensionꢀ ability.ꢀ Further,ꢀ theꢀ
lengthꢀ ofꢀ theꢀ five-amino-acidꢀ unitꢀ (Nꢀ toꢀ Cꢀ terminal)ꢀ ofꢀ theꢀ
representativeꢀstructureꢀofꢀ7aꢀisꢀcloseꢀtoꢀtheꢀβ-strandꢀstructureꢀofꢀ
Aβ-peptide,ꢀwhichꢀmayꢀreproduceꢀtheꢀdistance,ꢀangularꢀprojectionꢀ
ofꢀ theꢀ proteinꢀ surface.ꢀ Theꢀ mostꢀ populatedꢀ structureꢀ forꢀ 7aꢀ inꢀ
methanolꢀisꢀshownꢀinꢀFigureꢀS4ꢀ(b).ꢀ
NHBoc
(a)
H
Val 1
9
.3ꢀ
HN
O
O
8.8ꢀ
8.3ꢀ
7.8ꢀ
H
Ala 1
N
Vla1-NHꢀ
Ala1-NHꢀ
Ala2-NHꢀ
Val2-NHꢀ
O
R
*
O
HN
7
.3ꢀ
Ala 2
Val 2
H
Finally,ꢀinꢀtheꢀpresenceꢀofꢀtheꢀpenta-peptideꢀresidues,ꢀaggregationꢀ
O
1
7
NH
6.8ꢀ
6.3ꢀ
ofꢀAmyloidꢀisꢀnotꢀaffected ꢀ(FigureꢀS6,ꢀaꢀresultꢀforꢀ7aꢀandꢀ7bꢀwasꢀ
shown),ꢀwhichꢀisꢀatꢀleastꢀpartiallyꢀconsistentꢀwithꢀtheꢀideaꢀthatꢀtheꢀ
presentꢀsingleꢀβ-strandꢀmimicsꢀareꢀindependentꢀofꢀaggregationꢀandꢀ
inter-strandꢀ hydrogenꢀ bonding.ꢀ Thusꢀ ourꢀ newꢀ “pointꢀ mutationꢀ
strategy”ꢀ byꢀ introductionꢀ ofꢀ aꢀ singleꢀ Abhꢀ aminoꢀ acidꢀ inꢀ anꢀ
appropriateꢀstrandꢀsequenceꢀisꢀexpectedꢀtoꢀbeꢀaꢀpotentialꢀprobeꢀtoꢀ
identifyꢀwhichꢀaminoꢀacidꢀisꢀcrucialꢀforꢀβ-sheet/β-strandꢀinteractionꢀ
inꢀ PPIꢀ orꢀ aggregation,ꢀ becauseꢀ itꢀ isꢀ notꢀ easyꢀ toꢀ identifyꢀ theꢀ keyꢀ
interactionꢀsite(s)ꢀinꢀPPIꢀandꢀaggregation.ꢀꢀ
H
O
O
59ꢀ
64ꢀ
69ꢀ
74ꢀ
o
T( C)ꢀ
7
a
(b)
15000ꢀ
1
0000ꢀ
000ꢀ
5
0ꢀ
190ꢀ
5000ꢀ
210ꢀ
230ꢀ
250ꢀ
270ꢀ
290ꢀ
-
ꢀꢁ
7
a
2ꢀ2mM
3ꢀ1mM
1ꢀ100"M
-
-
-
-
10000ꢀ
15000ꢀ
20000ꢀ
25000ꢀ
Conflictsꢀofꢀinterestꢀ
ꢀ
ꢁ
7a
ꢀ
ꢁ
7a
Thereꢀareꢀnoꢀconflictsꢀtoꢀdeclare.ꢀ
wavenumber (nm)
ꢀ
Acknowledgementsꢀꢀ
3
Figureꢀ5ꢀ(a)ꢀTemperatureꢀdependencyꢀofꢀ Jꢀcouplingꢀconstantsꢀinꢀchloroformꢀ
AꢀpartꢀofꢀcomputationsꢀwereꢀperformedꢀatꢀtheꢀResearchꢀCenterꢀforꢀ
ComputationalꢀScience,ꢀOkazaki,ꢀJapan.ꢀThisꢀworkꢀwasꢀsupportedꢀbyꢀ
JSPSꢀKAKENHIꢀGrantꢀNumbersꢀJPꢀ26104508ꢀandꢀ16K08157ꢀ(YO)ꢀandꢀ
(
CDCl -d )ꢀ forꢀ 7aꢀ (60mM).ꢀ (b)ꢀ Concentrationꢀ dependencyꢀ ofꢀ 7aꢀ ofꢀ CDꢀ inꢀ
3 1
o
MeOHꢀatꢀ20 C.ꢀꢀ
2
6293002ꢀandꢀ18H02552ꢀ(TO).ꢀ
N
Lys
Notesꢀandꢀreferencesꢀ
Val (α)
N
1
W.ꢀA.ꢀLoughlin,ꢀJ.ꢀA.ꢀTyndall,ꢀM.ꢀP.ꢀGlennꢀandꢀD.ꢀP.ꢀFairlie,ꢀChem.ꢀRev.ꢀ
004,ꢀ104,ꢀ6085–6118.ꢀ
2
Leu
Ala (α)
R)-Abh (β) 16.46Å
2
3
4
J.ꢀA.ꢀTyndall,ꢀT.ꢀNallꢀandꢀD.ꢀP.ꢀFairlie,ꢀChem.ꢀRev.ꢀ2005,ꢀ105,ꢀ973-999.ꢀ
A.ꢀM.ꢀWatkinsꢀandꢀP.ꢀS.ꢀArora,ꢀACSꢀChem.ꢀBiol.ꢀ2014,ꢀ9,ꢀ1747-1754.ꢀ
J.ꢀS.ꢀNowick,ꢀD.ꢀL.ꢀHolmes,ꢀG.ꢀMackin,ꢀG.ꢀNoronha,ꢀA.ꢀJ.ꢀShakaꢀandꢀE.ꢀ
M.ꢀSmith,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.ꢀ1996,ꢀ118,ꢀ2764–2765.ꢀ
S.ꢀT.ꢀPhillips,ꢀM.ꢀRezac,ꢀU.ꢀAbel,ꢀM.ꢀKossenjansꢀandꢀP.ꢀA.ꢀBartlett,ꢀJ.ꢀ
Am.ꢀꢀChem.ꢀꢀSoc.ꢀ2002,ꢀ124,ꢀ58–66.ꢀ
C.ꢀKang,ꢀY.ꢀSunꢀandꢀJ.ꢀR.ꢀDelꢀValle,ꢀOrg.ꢀLett.ꢀ2012.ꢀ14,ꢀ6162-6165.ꢀ
C.ꢀKang,ꢀM.ꢀP.ꢀSarnowski,ꢀS.ꢀRanatunga,ꢀL.ꢀWojtas,ꢀR.ꢀS.ꢀMetcalf,ꢀW.ꢀC.ꢀ
GuidaꢀandꢀJ.ꢀR.ꢀDelꢀValle,ꢀChem.ꢀCommun.ꢀ2015,ꢀ51,ꢀ16259-16262.ꢀꢀ
R.ꢀC.ꢀReid,ꢀM.ꢀJ.ꢀKelso,ꢀM.ꢀJ.ꢀScanlonꢀandꢀD.ꢀP.ꢀFairlie,ꢀJ.ꢀAm.ꢀChem.ꢀ
Soc.ꢀ2002,124,ꢀ5673–5683.ꢀ
1
6.51Å
(
Val
Phe
5
Ala (α)
Val (α)
PDB:2LMP
6
7
Phe
C
C
8
9
!
-Strand Structure (X-ray)
penta-peptides in A!40-K16L17V18F19F20
Pentamer 7a
Population : 66%
-
M.ꢀHosoya,ꢀY.ꢀOtani,ꢀM.ꢀKawahata,ꢀK.ꢀYamaguchiꢀandꢀT.ꢀOhwada,ꢀJ.ꢀ
Am.ꢀChem.ꢀSoc.ꢀ2010,ꢀ132,ꢀ14780–14789.ꢀ
ꢀ
Figureꢀ6.ꢀRepresentativeꢀstructureꢀofꢀ7a,ꢀtogetherꢀwithꢀβ-strandꢀstructureꢀofꢀ 10 S.ꢀToal,ꢀO.ꢀAmidiꢀandꢀR.ꢀSchweitzer-Stenner,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.ꢀ2011,ꢀ
partꢀofꢀanꢀAβꢀpeptideꢀfibril.ꢀOxygenꢀisꢀshownꢀinꢀred,ꢀnitrogenꢀinꢀblue,ꢀcarbonꢀ
133,ꢀ12728–12739.ꢀ
inꢀgreyꢀandꢀpolarꢀhydrogenꢀinꢀgreenꢀ(onlyꢀpolarꢀhydrogenꢀatomsꢀareꢀshown).ꢀ 11 A.ꢀBundiꢀandꢀK.ꢀWüthrich,ꢀBiopolymers.ꢀ1979,ꢀ18,ꢀ285–297.ꢀ
Lengthsꢀofꢀaminoꢀacidꢀresiduesꢀareꢀshown.ꢀ
12 F.ꢀAvbelj,ꢀS.ꢀG.ꢀGrdadolnik,ꢀJ.ꢀGrdadolnikꢀandꢀR.ꢀL.ꢀBaldwin,ꢀProc.ꢀNatl.ꢀ
Acad.ꢀSci.ꢀ2006,ꢀ103,ꢀ1272–1277.ꢀꢀꢀG.ꢀW.ꢀVuisterꢀandꢀA.ꢀBax,ꢀJ.ꢀAm.ꢀ
Chem.ꢀSoc.ꢀ1993,ꢀ115,ꢀ7772–7777.ꢀ
Molecularꢀdynamicsꢀcalculations:ꢀInꢀorderꢀtoꢀgainꢀaꢀmoreꢀdetailedꢀ
insightꢀintoꢀtheꢀstructuralꢀdynamicsꢀofꢀtheꢀtetrapeptidesꢀ6a,ꢀ6bꢀandꢀ
pentapeptideꢀ 7a,ꢀ molecularꢀ dynamicsꢀ (MD)ꢀ simulationsꢀ wereꢀ
performedꢀwithꢀtheꢀOPLS3ꢀforceꢀfieldꢀinꢀchloroformꢀatꢀ298ꢀKꢀforꢀ100ꢀ
ns.ꢀFinally,ꢀ3334ꢀstructuresꢀwereꢀobtainedꢀandꢀclustered.ꢀTheꢀmostꢀ
populatedꢀclustersꢀforꢀ6aꢀshowꢀextendedꢀstructuresꢀ(FigureꢀS4ꢀ(a))ꢀ
andꢀ 6bꢀ takesꢀ randomꢀ coilꢀ structuresꢀ (dataꢀ notꢀ shown).ꢀ Theꢀ mostꢀ
populatedꢀ(66%)ꢀclusterꢀforꢀ7aꢀareꢀshownꢀinꢀFigureꢀ6,ꢀtogetherꢀwithꢀ
theꢀβ-strandꢀstructureꢀofꢀpentaꢀamino-acid-residueꢀofꢀAβ-peptideꢀinꢀ
1
1
3 G.ꢀW.ꢀVuisterꢀandꢀA.ꢀBax,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.ꢀ1993,ꢀ115,ꢀ7772–7777.ꢀ
4 L.ꢀZhai,ꢀS.ꢀWang,ꢀM.ꢀNara,ꢀK,ꢀTakeuchi,ꢀI,ꢀShimada,ꢀY.ꢀOtaniꢀandꢀT.ꢀ
Ohwada,ꢀJ.ꢀOrg.ꢀChem.ꢀ2018,ꢀ83,ꢀ13063–13079.ꢀ
1
1
1
5 A.ꢀAlex,ꢀD.ꢀS.ꢀMillan,ꢀM.ꢀPerez,ꢀF.ꢀWakenhutꢀandꢀG.ꢀA.ꢀWhitlock,ꢀꢀ
Medchemcomm.ꢀ2011,ꢀ2,ꢀS3.ꢀ
6 A.ꢀK.ꢀParavastu,ꢀR.ꢀD.ꢀLeapman,ꢀW.ꢀYauꢀandꢀR.ꢀTycko,ꢀProc.ꢀNatl.ꢀ
Acad.ꢀSci.ꢀ2008,ꢀ105,ꢀ18349–18354.ꢀ
7 Y.ꢀHori,ꢀT.ꢀHashimoto,ꢀH.ꢀNomoto,ꢀB.ꢀT.ꢀHymanꢀandꢀT.ꢀIwatsubo,ꢀJ.ꢀ
Biol.ꢀChem.ꢀ2015,ꢀ290,ꢀ15163–15174.ꢀꢀ
4
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
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ChemComm
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DOI: 10.1039/C9CC08378B
Both (R- and S-) enantiomers of the bridgehead-substituted β-proline analogue (i.e., 7-
azabicyclo[2.2.1]heptane-2-carboxylic acid or Abh amino acid (Abh-AA)) can work as
a new scaffold for single β-strand enforcement and propagation.
Single
β-Strand
N
Mimicꢀ
H
O
R
H
N
O
R
N
H
O