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Translational diffusion measured by PFG‐NMR on full length and fragments of the Alzheimer Aβ(1–40) peptide. Determination of hydrodynamic radii of random coil peptides of varying length
Author(s) -
Danielsson Jens,
Jarvet Jüri,
Damberg Peter,
Gräslund Astrid
Publication year - 2002
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1132
Subject(s) - chemistry , hydrodynamic radius , random coil , scaling , diffusion , peptide , radius , monomer , pentamer , radius of gyration , exponent , analytical chemistry (journal) , aqueous solution , crystallography , polymer , thermodynamics , chromatography , organic chemistry , physics , circular dichroism , biochemistry , geometry , mathematics , computer security , linguistics , philosophy , computer science , micelle
PFG‐NMR methods were used to measure the translational diffusion coefficients for the Aβ peptide involved in Alzheimer's disease and also for a series of fragments of this peptide. The peptides ranged from a pentamer to the full length Aβ(1–40). They were studied at 25° C and physiological pH in aqueous solution. The measured diffusion coefficients, including those of known monomeric peptides, were fitted without systematic deviations to a scaling law function of the molecular mass. We concluded that under these conditions Aβ(1–40) is in monomeric form. From the diffusion coefficient data, hydrodynamic radii r H were evaluated for the peptides. When combining our results on non‐ or weakly structured peptides with previously reported results on denatured proteins, we found that the hydrodynamic radii for the combined dataset could be well described by the same scaling law relating them to the molecular weight. The same law would even encompass data on single amino acids and di‐ and tripeptides measured by classical methods. From the above‐mentioned experimental data, scaling law parameters were determined. The relation between the measured hydrodynamic radius ( r H ) and the molecular weight of the polypeptide chain ( M r ) for amino acids, peptides and denatured proteins is r H = 0.27M r 0.50 Å. There is a remarkably good fit to this function for the measured hydrodynamic radii in a large range, almost three orders of magnitude, of molecular weights. The numerical value of the exponent, 0.5, is an indication that these polymers behave as Gaussian chains. Copyright © 2002 John Wiley & Sons, Ltd.