Silkmoth Chorion: A Natural Protective Amyloid - The Functional Fold: Amyloid Structures in Nature - page 59

TheX-raydifractionpatternofasilkmothchorionshownin
Fig.4.4indicatesthat

β

-sheetisthedominantsecondarystructure
ofitsconstituentproteins.FT-Ramanspectroscopy(Fig.4.5)and
attenuatedtotalreflectanceFouriertransforminfrared(ATR-FTIR)
spectroscopy(Fig.4.6)suggestthatthe

β

12

-sheetsareantiparallel.

------- outer side
------- inner side

a b

1100 1200 1300 1400 1500 1600 1700 1800

Wavenumber (cm -1 )

FT-Raman(450-1800cm -1 )spectrumof

Figure 4.5 (a) asilkmothchorion

of Thesecondderivativespectrumisincluded.

Errorbarequalsto0.5

A. polyphemus.

σ

.ThepositionsoftheamideIat

-1 -1

1673cm bandsintheRaman

spectrumarewellknownindicatorsof

andamideIIIat1235cm

-sheetsecondary
structureforsilkmothchorionproteins(Hamodrakas

β

et al.,

β

1982).The -sheetsareveryuniformandverywellorganised

ascanbejudgedbytherathernarrowbandwidth(~30cm -1 ),
athalfmaximumintensity,oftheamideIbandat1673cm -1 .
(b)ATR-FTIRspectratakenfromtheouter(magenta)and
inner(green)surfacesofan silkmothchorion.

Thesecondderivativesareincluded.TheamideIandIIIbands
at1626and1230cm -1 ,respectively,clearlyindicatea

A. polyphemus

β

-sheet
typeofstructureforsilkmothchorionproteins.Theshoulderin
theamideIregion,at1694cm -1 ,suggeststhatthe -sheetsare

anti-parallel.ReprintedfromBiopolymers(Biospectroscopy),
72,185-192,copyright(2003),withpermissionfromJohn
WileyandSons.SeealsoColourInsert.

β

About200proteinshavebeendetectedinthesilkmothchorion.

13

10

Theseproteinshavebeenclassifiedintotwomajorclasses,AandB.

Thegenefamiliesencodingtheseproteinsarerelatedandconstitute
asuperfamilywithtwobranches,the

14

α

-branchandthe

β

-branch.