Order Matrix Analysis of Residual Dipolar Couplings Using Singular Value Decomposition

• Published in: Journal of magnetic resonance (1997) 1999-06, Vol.138 (2), p.334-342
• Main Authors: Losonczi, Judit A, Andrec, Michael, Fischer, Mark W.F, Prestegard, James H
• Format: Article
• Language: English
• Subjects: anisotropic spin interactions; Anisotropy; barley lectin protein; domain–domain orientation; Hordeum; Hydrogen Bonding; Lectins - chemistry; Mathematics; Nitrogen Isotopes; Nuclear Magnetic Resonance, Biomolecular - methods; Plant Lectins; Protein Conformation; Protein Folding; Saupe order matrix; singular value decomposition; Spin Labels
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1006/jmre.1999.1754

The measurement of anisotropic spin interactions, such as residual dipolar couplings, in partially ordered solutions can provide valuable information on biomolecular structure. While the information can be used to refine local structure, it can make a unique contribution in determining the relative orientation of remote parts of molecules, which are locally well structured, but poorly connected based on NOE data. Analysis of dipolar couplings in terms of Saupe order matrices provides a concise description of both orientation and motional properties of locally structured fragments in these cases. This paper demonstrates that by using singular value decomposition as a method for calculating the order matrices, principal frames and order parameters can be determined efficiently, even when a very limited set of experimental data is available. Analysis of 1H–15N dipolar couplings, measured in a two-domain fragment of the barley lectin protein, is used to illustrate the computational method.