Study of Protein Conformation and Orientation in Silkworm and Spider Silk Fibers Using Raman Microspectroscopy
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- 作者：Marie-Eve Rousseau ; Thierry Lefè ; vre ; Lilyane Beaulieu ; Tetsuo Asakura ; and Michel Pé ; zolet
- 刊名：Biomacromolecules
- 出版年：2004
- 出版时间：November 2004
- 年：2004
- 卷：5
- 期：6
- 页码：2247 - 2257
- 全文大小：224K
- 年卷期：v.5,no.6(November 2004)
- ISSN：1526-4602
文摘
Raman microspectroscopy has been used for the first time to determine quantitatively the orientation of the
-sheets in silk monofilaments from Bombyx mori and Samia cynthia ricini silkworms, and from the spiderNephila edulis. It is shown that, for systems with uniaxial symmetry such as silk, it is possible to determinethe order parameters <P2> and <P4> of the orientation distribution function from intensity ratios of polarizedRaman spectra. The equations allowing the calculation of <P2> and <P4> using polarized Ramanmicrospectroscopy for a vibration with a cylindrical Raman tensor were first derived and then applied tothe amide I band that is mostly due to the C=O stretching vibration of the peptide groups. The shape of theRaman tensor for the amide I vibration of the -sheets was determined from an isotropic film of Bombyxmori silk treated with methanol. For both the Bombyx mori and Samia cynthia ricini fibroin fibers, thevalues of <P2> and <P4> obtained are equal to -0.36 ± 0.03 and 0.19 ± 0.02, respectively, even though thetwo types of silkworm fibroins strongly differ in their primary sequences. For the Nephila edulis draglinesilk, values of <P2> and <P4> of -0.32 ± 0.02 and 0.13 ± 0.02 were obtained, respectively. These resultsclearly indicate that the carbonyl groups are highly oriented perpendicular to the fiber axis and that the-sheets are oriented parallel to the fiber axis, in agreement with previous X-ray and NMR results. Themost probable distribution of orientation was also calculated from the values of <P2> and <P4> using theinformation entropy theory. For the three types of silk, the -sheets are highly oriented parallel to the fiberaxis. The orientation distributions of the -sheets are nearly Gaussian functions with a width of 32
and 40for the silkworm fibroins and the spider dragline silk, respectively. In addition to these results, the comparisonof the Raman spectra recorded for the different silk samples and the polarization dependence of severalbands has allowed to clarify some important band assignments.
-sheets in silk monofilaments from Bombyx mori and Samia cynthia ricini silkworms, and from the spiderNephila edulis. It is shown that, for systems with uniaxial symmetry such as silk, it is possible to determinethe order parameters <P2> and <P4> of the orientation distribution function from intensity ratios of polarizedRaman spectra. The equations allowing the calculation of <P2> and <P4> using polarized Ramanmicrospectroscopy for a vibration with a cylindrical Raman tensor were first derived and then applied tothe amide I band that is mostly due to the C=O stretching vibration of the peptide groups. The shape of theRaman tensor for the amide I vibration of the -sheets was determined from an isotropic film of Bombyxmori silk treated with methanol. For both the Bombyx mori and Samia cynthia ricini fibroin fibers, thevalues of <P2> and <P4> obtained are equal to -0.36 ± 0.03 and 0.19 ± 0.02, respectively, even though thetwo types of silkworm fibroins strongly differ in their primary sequences. For the Nephila edulis draglinesilk, values of <P2> and <P4> of -0.32 ± 0.02 and 0.13 ± 0.02 were obtained, respectively. These resultsclearly indicate that the carbonyl groups are highly oriented perpendicular to the fiber axis and that the-sheets are oriented parallel to the fiber axis, in agreement with previous X-ray and NMR results. Themost probable distribution of orientation was also calculated from the values of <P2> and <P4> using theinformation entropy theory. For the three types of silk, the -sheets are highly oriented parallel to the fiberaxis. The orientation distributions of the -sheets are nearly Gaussian functions with a width of 32 and 40for the silkworm fibroins and the spider dragline silk, respectively. In addition to these results, the comparisonof the Raman spectra recorded for the different silk samples and the polarization dependence of severalbands has allowed to clarify some important band assignments.