Maximum Occurrence: Difference between revisions
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New page: Maximum Occurrence (MO)<ref>doi:10.1021/ja1063923</ref> refers to a method for making rigorous numerical assessments about the maximum percent of time that a conformer of a flexible macrom... |
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Maximum Occurrence (MO)<ref>doi:10.1021/ja1063923</ref> refers to a method for making rigorous numerical assessments about the maximum percent of time that a conformer of a flexible macromolecule can exist and still be compatible with the experimental data. Maximum Occurrence of a conformer is defined as the maximum weight that it can have in one ensemble that matches the average experimental data. | Maximum Occurrence (MO)<ref name='jacs_rav'>doi:10.1021/ja1063923</ref> refers to a method for making rigorous numerical assessments about the maximum percent of time that a conformer of a flexible macromolecule can exist and still be compatible with the experimental data. Maximum Occurrence of a conformer is defined as the maximum weight that it can have in one ensemble that matches the average experimental data. | ||
== Background == | == Background == | ||
Flexible proteins, even in the simplest case of two rigid domains linked by a flexible region, may sample a wide conformational space. Such variety makes their study by X-ray crystallography difficult, because a single conformation is trapped in the crystal, if crystals are obtained at all. Solution techniques such as Nuclear Magnetic Resonance (NMR) and Small-Angle Scattering of both X-rays and Neutrons (SAXS and SANS), provide experimental observables averaged over many conformation with different weights. | Flexible proteins, even in the simplest case of two rigid domains linked by a flexible region, may sample a wide conformational space. Such variety makes their study by X-ray crystallography difficult, because a single conformation is trapped in the crystal, if crystals are obtained at all. Solution techniques such as Nuclear Magnetic Resonance (NMR) and Small-Angle Scattering of both X-rays and Neutrons (SAXS and SANS), provide experimental observables averaged over many conformation with different weights. | ||
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The Maximum Occurrence is the maximum percent of time that a conformer of a macromolecule can exist and still be compatible with the experimental data (see Figure 1). In this case, the quantitative assessment is rigorous, since only one conformer of the ensemble is considered while the completing conformers are not artificially endowed of physical relevance that they may not have. | The Maximum Occurrence is the maximum percent of time that a conformer of a macromolecule can exist and still be compatible with the experimental data (see Figure 1). In this case, the quantitative assessment is rigorous, since only one conformer of the ensemble is considered while the completing conformers are not artificially endowed of physical relevance that they may not have. | ||
[[Image:MO_profiles.png|thumbnail|350px|Figure 1: Maximum Occurrence profiles for some conformers of Calcium-loaded calmodulin. Dashed line indicates the maximum allowed disagreement between experimental and calculated data.]] | [[Image:MO_profiles.png|thumbnail|350px|Figure 1: Maximum Occurrence profiles for some conformers of Calcium-loaded calmodulin. Dashed line indicates the maximum allowed disagreement between experimental and calculated data.]] | ||
Recently, an implementation of this method based on distributed computing was presented to evaluate the MO profiles for a large number of conformers: this represents an evolution of a previous approach where few conformations with maximum allowed probability (MAP) were looked for<ref>DOI:10.1021/ja0726613</ref>. | Recently, an implementation of this method based on distributed computing was presented to evaluate the MO profiles for a large number of conformers<ref name='jacs_rav'/>: this represents an evolution of a previous approach where few conformations with maximum allowed probability (MAP) were looked for<ref>DOI:10.1021/ja0726613</ref>. | ||
== Methods for determination of Maximum Occurrence== | == Methods for determination of Maximum Occurrence== | ||
