Transforming between discrete and continuous angle distribution models. Application to protein X1 torsions

Schmidt, Jürgen M. (2012) Transforming between discrete and continuous angle distribution models. Application to protein X1 torsions. Journal of Biomolecular NMR, 54 (1). pp. 97-114. ISSN 0925-2738. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Two commonly employed angular-mobility models for describing amino-acid side-chain <chi>1 torsion conformation, the staggered-rotamer jump and the normal probability density, are discussed and performance differences in applications to scalar-coupling data interpretation highlighted. Both models differ in their distinct statistical concepts, representing discrete and continuous angle distributions, respectively. Circular statistics, introduced for describing torsion-angle distributions by using a universal circular order parameter central to all models, suggest another distribution of the continuous class, here referred to as the elliptic model. Characteristic of the elliptic model is that order parameter and circular variance form complementary moduli. Transformations between the parameter sets that describe the probability density functions underlying the different models are provided. Numerical aspects of parameter optimization are considered. The issues are typified by using a set of <chi>1 related 3J coupling constants available for FK506-binding protein (FKBP). The discrete staggered-rotamer model is found generally to produce lower order parameters, implying elevated rotatory variability in the amino-acid side chains, whereas continuous models tend to give higher order parameters that suggest comparatively less variation in angle conformations. The differences perceived regarding angular mobility are attributed to conceptually different features inherent to the models.

Item Type: Article
Uncontrolled keywords: Circular statistics; Directional data; Probability density; Gaussian model; Elliptic model; Jinc function; Bessel function; Torsion angle conformation; Rotamer equilibria; Differential probability; 3 J; Vicinal coupling constants Amino-acid side chain; Protein structure; FKBP
Subjects: Q Science > QC Physics
Q Science > QD Chemistry
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Protein Science Group
Depositing User: Jurgen M Schmidt
Date Deposited: 08 Sep 2012 15:11
Last Modified: 06 Jun 2014 11:25
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