Difference Patterson map - Revision history

MassimoNespolo: Lang (Fr, It)

2019-06-18T14:51:07Z

Lang (Fr, It)

BrianMcMahon: Added German and Spanish translations (U. Mueller)

2017-11-10T13:38:20Z

Added German and Spanish translations (U. Mueller)

BrianMcMahon at 12:55, 13 May 2017

2017-05-13T12:55:22Z

BrianMcMahon at 12:36, 9 April 2008

2008-04-09T12:36:44Z

New page

== Definition ==

An application of [[Patterson methods]] for solution of crystal structures, typically proteins with heavy-atom derivatives, where the Patterson function is calculated using structure-factor coefficients based on the difference between the heavy-atom derivative and the native molecule.

== Discussion ==

[[Patterson methods]] for determining diffraction phases depend on the symmetries of interatomic vectors that show up as peaks in a three-dimensional map of the Patterson function. For small molecules containing a [[heavy-atom method|heavy atom]], the heavy-atom positions can be determined directly from the Patterson function calculated using measured structure-factor amplitudes. For proteins, there are too few heavy atoms for this approach to be successful. However, if an isomorphous derivative crystal is available (''i.e.'' one whose symmetry and dimensions and contents, with the exception of heavy-atom addition, are minimally changed), a Patterson map of derivative (<math>F_{PH}</math>) minus native (<math>F_P</math>) structure factors will be dominated by the vectors between the heavy atoms, and thus allow a solution of the coordinates of the heavy atoms.

A true difference Patterson function, representing the difference between the Patterson of the derivative minus the Patterson of the native protein, should be calculated using as coefficients <math>|F^2_{PH} - F^2_P|</math>.

In practice, protein crystallographers normally calculate a '''modulus difference-squared synthesis''', also known as an '''isomorphous difference Patterson''', using coefficients <math>(|F_{PH}| - |F_P|)^2</math>.

== See also ==

Patterson and molecular-replacement techniques.
M. G. Rossmann and E. Arnold. ''International Tables for Crystallography'' (2006). Vol. B, ch. 2.3, pp. 235-263 [http://dx.doi.org/10.1107/97809553602060000556 doi:10.1107/97809553602060000556]

[[Category:Biological crystallography]]
[[Category:Structure determination]]

← Older revision		Revision as of 14:51, 18 June 2019
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−	<font color="red">Differenz-Patterson-Karte</font> (''Ge''). <font color="green">Mapa de Patterson de diferencia</font> (''Sp'').	+	<font color="blue">Carte de différence de Patterson</font> (''Fr''). <font color="red">Differenz-Patterson-Karte</font> (''Ge''). <font color="black">Mappa di differenza di Patterson</font> (''It''). <font color="green">Mapa de Patterson de diferencia</font> (''Sp'').

	== Definition ==		== Definition ==

← Older revision		Revision as of 13:38, 10 November 2017
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		+	<font color="red">Differenz-Patterson-Karte</font> (''Ge''). <font color="green">Mapa de Patterson de diferencia</font> (''Sp'').
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	== Definition ==		== Definition ==

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 == See also ==
-Patterson and molecular-replacement techniques.
+*Patterson and molecular-replacement techniques, and the use of noncrystallographic symmetry in phasing. L. Tong, M. G. Rossmann and E. Arnold. ''International Tables for Crystallography'' (2008). Vol. B, [https://doi.org/10.1107/97809553602060000765 ch. 2.3, pp. 244-281  ]
 [[Category:Biological crystallography]]
 [[Category:Structure determination]]