Journal
JOURNAL OF BIOMOLECULAR NMR
Volume 65, Issue 3-4, Pages 143-156Publisher
SPRINGER
DOI: 10.1007/s10858-016-0045-x
Keywords
Conformational exchange; CPMG; CEST; Spin relaxation; Boundary conditions
Categories
Funding
- Canadian Institutes of Health Research
- Natural Sciences and Engineering Research Council of Canada
Ask authors/readers for more resources
Transient excursions of native protein states to functionally relevant higher energy conformations often occur on the mu s-ms timescale. NMR spectroscopy has emerged as an important tool to probe such processes using techniques such as Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion and Chemical Exchange Saturation Transfer (CEST). The extraction of kinetic and structural parameters from these measurements is predicated upon mathematical modeling of the resulting relaxation profiles, which in turn relies on knowledge of the initial magnetization conditions at the start of the CPMG/CEST relaxation elements in these experiments. Most fitting programs simply assume initial magnetization conditions that are given by equilibrium populations, which may be incorrect in certain implementations of experiments. In this study we have quantified the systematic errors in extracted parameters that are generated from analyses of CPMG and CEST experiments using incorrect initial boundary conditions. We find that the errors in exchange rates (k(ex)) and populations (p(E)) are typically small (<10 %) and thus can be safely ignored in most cases. However, errors become larger and cannot be fully neglected (20-40 %) as k(ex) falls near the lower limit of each method or when short CPMG/CEST relaxation elements are used in these experiments. The source of the errors can be rationalized and their magnitude given by a simple functional form. Despite the fact that errors tend to be small, it is recommended that the correct boundary conditions be implemented in fitting programs so as to obtain as robust estimates of exchange parameters as possible.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available