Determination of the amide I Raman tensor for the antiparallel β‐sheet: application to silkworm and spider silks

Abstract

The amide I Raman tensor corresponding to the antiparallel b-sheet structure in proteins has been determined by polarized Raman microspectroscopy of fowl feather rachis using polarized Raman spectra excited in the near-infrared (785 nm). For a Raman tensor principal axis system (XYZ), in which X is perpendicular to the plane of the pleated b-sheet, Y is in the plane of the sheet and perpendicular to the direction of the polypeptide chain, and Z is parallel to the direction of the polypeptide chain, the principal tensor components (a XX , a YY , a ZZ ) are found to satisfy the following relationships: R 1 ≡ a XX /a ZZ = 0.32 and R 2 ≡ a YY /a ZZ = 3.48. With this Raman tensor determination, we show that semiquantitative estimates of the total antiparallel b-sheet content in b-rich proteins can be extracted from polarized Raman intensity measurements on the amide I marker of the b-sheet occurring near 1664 cm −1 . We demonstrate this approach for the b-rich silk proteins of the silkworm and spider. INTRODUCTIONThe antiparallel chain, pleated-sheet conformation (ˇ-sheet) is a fundamental structural component of native proteins. 1 The silk of both silkworms and spiders and the rachis keratins of fowl feather barbs are examples of native proteins in which the antiparallelˇ-sheet is the major structural element. 2 A key property of theˇ-sheet structure in both silk and feathers is a high degree of polypeptide chain orientation. Thě -sheet conformation is also prevalent in nonnative and misfolded proteins and has been implicated in polypeptide † Presented as part of a commemorative issue for Wolfgang Kiefer on the occasion of his 65th birthday.

Probing the Cross-β Core Structure of Amyloid Fibrils by Hydrogen−Deuterium Exchange Deep Ultraviolet Resonance Raman Spectroscopy

“…Approximate D 2 symmetry of the antiparallel -sheet gives rise to four vibrational modes in the amide I region, A (1675 cm -1 ), B (∼1690 cm -1 , not observed), B 2 (1633 cm -1 ), and B 3 (unknown). 17 Two of them, A (1675 cm -1 ) and B 2 (1635 cm -1 ), are well resolved in the cross-core spectrum indicating that the antiparallel -sheet structure dominates the lysozyme fibril core. The other two amide I bands may be obscured by the strong 1675 cm -1 band resonantly enhanced via Albercht A term.…”

“…The other two amide I bands may be obscured by the strong 1675 cm -1 band resonantly enhanced via Albercht A term. 17 The C R -H band is composed of at least three narrow sub-bands centered at Figure 1. DUVRR spectra of (a) thermally denatured hen egg white lysozyme in H2O (blue) and D2O (red), and (b) lysozyme fibrils in H2O (blue), 50% D2O/H2O mixture (green), and 100% D2O (red).…”

Raman Tensors and their application in structural studies of biological systems

“…The tensor components r 1 = α xx / α zz and r 2 = α yy / α zz are denoted by blue and red numerals, respectively. References to the original literature, where details of the tensor calculations are described, are as follows: (A) Ueda et al ; 9) (B) Benevides et al ; 16) (C) Tsuboi et al ; 3),47) (D1) Benevides et al ; 44) (D2) Thomas et al ; 10) (E1) Ushizawa et al ; 14) (E2) Benevides et al ; 44) (F1) Tsuboi et al ; 3) (F2) Tsuboi et al ; 3) (G1) Overman et al ; 25) (G2) Tsuboi et al ; 57) (G3) Yokote et al ; 41) (G4) Yokote et al ; 41) (H1)(H2)(H3) Tsuboi et al ; 8) (I1)(I2)(I3) Tsuboi et al ; 15) (J1) Thomas et al ; 10) (J2) Benevides et al ; 16) (K1)(K2) Benevides et al ; 44) (L1) Thomas et al ; 10) (L2)(L3) Tsuboi et al ; 12) (L4) Kumakura et al ; 49) (M1) Thomas et al ; 10) (M2) Benevides et al ; 44) (M3) Ushizawa et al ; 46) (N1) Ueda et al ; 51) (N2) Benevides et al ; 44) (N3) Ushizawa et al ; 55) (O1) Thomas et al ; 10) (O2)(O3)(O4) Benevides et al ; 16) (O5)(O6) Benevides et al 44) …”

Raman spectroscopy at the beginning of the twenty‐first century

“…This technique was used by Tsuboi et al 30 to determine the amide I Raman tensor for the antiparallelˇ-sheet structure in proteins of fowl feather rachis. The Raman tensor determined in this way is also applied to Raman studies of other naturalˇ-sheet structures, and it is successfully shown that in this way the relative contribution ofˇ-turns can be determined.…”