Circular dichroism spectra of short, fixed-nucleus alanine helices
AUTOR(ES)
Chin, Der-Hang
FONTE
National Academy of Sciences
RESUMO
Very short alanine peptide helices can be studied in a fixed-nucleus, helix-forming system [Siedlicka, M., Goch, G., Ejchart, A., Sticht, H. & Bierzynski, A. (1999) Proc. Natl. Acad. Sci. USA 96, 903–908]. In a 12-residue sequence taken from an EF-hand protein, the four C-terminal peptide units become helical when the peptide binds La3+, and somewhat longer helices may be made by adding alanine residues at the C terminus. The helices studied here contain 4, 8, or 11 peptide units. Surprisingly, these short fixed-nucleus helices remain almost fully helical from 4 to 65°C, according to circular dichroism results reported here, and in agreement with titration calorimetry results reported recently. These peptides are used here to define the circular dichroism properties of short helices, which are needed for accurate measurement of helix propensities. Two striking properties are: (i) the temperature coefficient of mean peptide ellipticity depends strongly on helix length; and (ii) the intensity of the signal decreases much less rapidly with helix length, for very short helices, than supposed in the past. The circular dichroism spectra of the short helices are compared with new theoretical calculations, based on the experimentally determined direction of the NV1 transition moment.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=137731Documentos Relacionados
- Circular dichroism spectra of twelve short DNA restriction fragments of known sequence: a comparison of measured and calculated spectra.
- Circular dichroism spectra show that repeating dinucleotide DNAs may form helices in which every other base is looped out.
- Circular dichroism spectra show that repeating dinucleotide DNA may form helices in which every other base is looped out
- Circular Dichroism Spectra of Granal and Agranal Chloroplasts of Maize
- Investigation of huge negative circular dichroism spectra of some nucleoproteins