ja0457462_si_001.pdf (395.83 kB)
Water-Solubilized, Cap-Stabilized, Helical Polyalanines: Calibration Standards for NMR and CD Analyses
journal contribution
posted on 2005-02-16, 00:00 authored by Björn Heitmann, Gabriel E. Job, Robert J. Kennedy, Sharon M. Walker, Daniel S. KempNMR and CD studies are reported for two length series of solubilized, spaced, highly helical
polyalanines that are N-capped by the optimal helix stabilizer βAsp-Hel and C-capped by β-aminoalanine
beta and that are studied in water at 2 °C, pH 1−8. NMR analysis yields a structural characterization of the
peptide AcβAspHelAla8betaNH2 and selected members of one βAspHelAlanbeta series. At pH > 4.5 the
βAspHel cap provides a preorganized triad of carboxylate anion and two amide residues that is
complementary to the helical polyalanine N-terminus. The C-terminal β-aminoalanine assumes a helix-stabilizing conformation consistent with literature precedents. H(N)CO NMR experiments applied to capped,
uniformly 13C- and 15N-labeled Ala8 and Ala12 peptides define Alan hydrogen bonding signatures as α-helical
without detectable 310 character. Relative NH→ND exchange rates yield site protection factors PFi that
define uniquely high fractional helicities FH for the peptide Alan regions. These Alan calibration series,
studied in water and lacking helix-stabilizing tertiary structure, yield the first 13C NMR chemical shifts, 3JHNHα
coupling constants, and CD ellipticities [θMolar]λ,n characteristic of a fully helical alanine within an Alan context.
CD data are used to assign parameters X and [θ]λ,∞, required for rigorous calculation of FH values from
CD ellipticities.
History
Usage metrics
Categories
Keywords
13 C NMR chemical shiftslength series13 Cβ AspHel capFH valuesCD studiesCD dataCD Analyses NMR3 J HNH αpreorganized triad3 10 characterpeptide Ala n regionscarboxylate anionliterature precedentsamide residueshelical alanineAla n calibration seriesAla n contexthelical polyalaninesAla n hydrogenparameters XCD ellipticitiessite protection factors PF ipeptide Ac β AspHelAla 8 beta NH 2β AspHelAla n beta seriesAla 12 peptideshelicities FH
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC