Electric susceptibility of unsolvated glycine-based peptides.
The DC electric susceptibilities of unsolvated glycine-based peptides, WGn (W = tryptophan and G = glycine) with n = 1-5, have been measured by deflection of a molecular beam in an electric field. These are the first electric deflection measurements performed on peptides. At 300 K the susceptibilities are in the range of 200-400 A(3). By far the largest contribution to the susceptibilities is from the permanent dipole moment of the peptides. The results indicate that the peptides do not have rigid conformations with fixed dipoles. Instead the dipole is averaged as the peptides explore their energy landscape. For a given WGn peptide, all molecules have almost the same average dipole, which suggests that they all explore a similar energy landscape on the microsecond time scale of the measurement. The measured susceptibilities are in good overall agreement with values calculated from the average dipole moment deduced from Monte Carlo simulations.
Antoine
Rodolphe
R
Laboratoire de Spectrométrie Ionique et Moléculaire, UMR No. 5579, Université Lyon I et CNRS, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
Compagnon
Isabelle
I
Rayane
Driss
D
Broyer
Michel
M
Dugourd
Philippe
P
Breaux
Gary
G
Hagemeister
Frederick C
FC
Pippen
David
D
Hudgins
Robert R
RR
Jarrold
Martin F
MF
D004563:Electrochemistry; D005998:Glycine / Q000737:chemistry*; D013058:Mass Spectrometry; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry
D010455:Peptides; D014364:Tryptophan; D005998:Glycine