Skip to main content
PMC home page
Biophysical Journal logoLink to Biophysical Journal
. 2000 May;78(5):2499–2510. doi: 10.1016/S0006-3495(00)76795-6

Orientation of the infrared transition moments for an alpha-helix.

D Marsh 1, M Müller 1, F J Schmitt 1
PMCID: PMC1300840  PMID: 10777747

Abstract

Appropriate values for the orientation of the amide transition dipoles are essential to the growing use of isotopically edited vibrational spectroscopy generally in structural biology and to infrared dichroism measurements on membrane-associated alpha-helices, in particular. The orientations of the transition moments for the amide vibrations of an alpha-helix have been determined from the ratio of intensities of the A- and E(1)-symmetry modes in the infrared spectra of poly(gamma-methyl-L-glutamate)(x)-co-(gamma-n-octadecyl-L-glutamate)( y) oriented on silicon substrates. Samples possessing a high degree of alignment were used to facilitate band fitting. Consistent results were obtained from both attenuated total reflection and transmission experiments with polarized radiation, yielding values of Theta(I) = 38 degrees, Theta(II) = 73 degrees, and Theta(A) = 29 degrees, relative to the helix axis, for the amide I, amide II, and amide A bands, respectively. The measurements are discussed both in the context of the somewhat divergent older determinations, and in relation to the helix geometry and results on model amide compounds, to resolve current uncertainties in the literature.

Full Text

The Full Text of this article is available as a PDF (145.8 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Arkin I. T., Rothman M., Ludlam C. F., Aimoto S., Engelman D. M., Rothschild K. J., Smith S. O. Structural model of the phospholamban ion channel complex in phospholipid membranes. J Mol Biol. 1995 May 12;248(4):824–834. doi: 10.1006/jmbi.1995.0263. [DOI] [PubMed] [Google Scholar]
  2. Arnott S., Dover S. D. Refinement of bond angles of an alpha-helix. J Mol Biol. 1967 Nov 28;30(1):209–212. doi: 10.1016/0022-2836(67)90253-7. [DOI] [PubMed] [Google Scholar]
  3. Axelsen P. H., Citra M. J. Orientational order determination by internal reflection infrared spectroscopy. Prog Biophys Mol Biol. 1996;66(3):227–253. doi: 10.1016/s0079-6107(97)00007-2. [DOI] [PubMed] [Google Scholar]
  4. Axelsen P. H., Kaufman B. K., McElhaney R. N., Lewis R. N. The infrared dichroism of transmembrane helical polypeptides. Biophys J. 1995 Dec;69(6):2770–2781. doi: 10.1016/S0006-3495(95)80150-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. BRADBURY E. M., BROWN L., DOWNIE A. R., ELLIOTT A., FRASER R. D., HANBY W. E. The structure of the omegaform of poly-Beta-benzyl-L-aspartate. J Mol Biol. 1962 Aug;5:230–247. doi: 10.1016/s0022-2836(62)80086-2. [DOI] [PubMed] [Google Scholar]
  6. Bechinger B., Ruysschaert J. M., Goormaghtigh E. Membrane helix orientation from linear dichroism of infrared attenuated total reflection spectra. Biophys J. 1999 Jan;76(1 Pt 1):552–563. doi: 10.1016/S0006-3495(99)77223-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Citra M. J., Axelsen P. H. Determination of molecular order in supported lipid membranes by internal reflection Fourier transform infrared spectroscopy. Biophys J. 1996 Oct;71(4):1796–1805. doi: 10.1016/S0006-3495(96)79380-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Draheim J. E., Gibson N. J., Cassim J. Y. Dramatic in situ conformational dynamics of the transmembrane protein bacteriorhodopsin. Biophys J. 1991 Jul;60(1):89–100. doi: 10.1016/S0006-3495(91)82033-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Luecke H., Schobert B., Richter H. T., Cartailler J. P., Lanyi J. K. Structure of bacteriorhodopsin at 1.55 A resolution. J Mol Biol. 1999 Aug 27;291(4):899–911. doi: 10.1006/jmbi.1999.3027. [DOI] [PubMed] [Google Scholar]
  10. Marsh D. Dichroic ratios in polarized Fourier transform infrared for nonaxial symmetry of beta-sheet structures. Biophys J. 1997 Jun;72(6):2710–2718. doi: 10.1016/S0006-3495(97)78914-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Marsh D. Nonaxiality in infrared dichroic ratios of polytopic transmembrane proteins. Biophys J. 1998 Jul;75(1):354–358. doi: 10.1016/S0006-3495(98)77519-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Marsh D. Spin-label electron spin resonance and Fourier transform infrared spectroscopy for structural/dynamic measurements on ion channels. Methods Enzymol. 1999;294:59–92. doi: 10.1016/s0076-6879(99)94007-7. [DOI] [PubMed] [Google Scholar]
  13. Nabedryk E., Breton J. Orientation of intrinsic proteins in photosynthetic membranes. Polarized infrared spectroscopy of chloroplasts and chromatophores. Biochim Biophys Acta. 1981 May 13;635(3):515–524. doi: 10.1016/0005-2728(81)90110-9. [DOI] [PubMed] [Google Scholar]
  14. Reisdorf W. C., Jr, Krimm S. Infrared dichroism of amide I and amide II modes of alpha I- and alpha II-helix segments in membrane proteins. Biophys J. 1995 Jul;69(1):271–273. doi: 10.1016/S0006-3495(95)79898-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Rothschild K. J., Clark N. A. Polarized infrared spectroscopy of oriented purple membrane. Biophys J. 1979 Mar;25(3):473–487. doi: 10.1016/S0006-3495(79)85317-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Tamm L. K., Tatulian S. A. Infrared spectroscopy of proteins and peptides in lipid bilayers. Q Rev Biophys. 1997 Nov;30(4):365–429. doi: 10.1017/s0033583597003375. [DOI] [PubMed] [Google Scholar]

Articles from Biophysical Journal are provided here courtesy of The Biophysical Society

RESOURCES