Combination of multiple isomorphous replacement and anomalous dispersion data for protein structure determination. III. Refinement of heavy atom positions by the least-squares method

1965 ◽  
Vol 19 (6) ◽  
pp. 883-885 ◽  
Author(s):  
G. Kartha
Keyword(s):  
Protein Structure ◽  
Least Squares ◽  
Structure Determination ◽  
Least Squares Method ◽  
Heavy Atom ◽  
Protein Structure Determination ◽  
Anomalous Dispersion ◽  
Isomorphous Replacement ◽  
Dispersion Data

Progress on the direct-methods solution of macromolecular structures using single-wavelength anomalous-dispersion (SAS) data

1999 ◽  
Vol 55 (4) ◽  
pp. 755-760 ◽  
Author(s):  
David A. Langs ◽  
Robert H. Blessing ◽  
Dongyao Guo
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Heavy Atom ◽  
Direct Methods ◽  
Anomalous Dispersion ◽  
Correct Solution ◽  
Phase Ambiguity ◽  
Practical Applications ◽  
The Past

In the past few years, a number of strategies have been outlined to resolve the SAS phase ambiguity given that unique estimates \omega(h, k) of the triple invariants are available. A new least-squares method is described that can in principle resolve the phase ambiguity to determine macromolecular phases provided that \omega(h, k) estimates are unbiased. Limitations of the method in practical applications are discussed. An example is given where the correct solution can be identified by use of the SAS tangent formula in the instance that traditional SAS phasing methods have lead to an incorrect heavy-atom substructure.

Triplet phase invariants from single isomorphous replacement or one-wavelength anomalous dispersion data, given heavy-atom information

1986 ◽  
Vol 42 (4) ◽  
pp. 246-253 ◽  
Author(s):  
J. Karle
Keyword(s):  
Structural Information ◽  
Heavy Atom ◽  
Anomalous Dispersion ◽  
Isomorphous Replacement ◽  
Dispersion Data ◽  
Predominant Type ◽  
Insight Into

Certain general algebraic formulas for computing triplet phase invariants become accessible when structural information is available concerning the replacement atoms in isomorphous replacement or the predominant type of anomalously scattering atoms in one-wavelength anomalous dispersion experiments. The formulas of interest are presented and subjected to a number of test calculations to obtain insight into their accuracy and to determine the effects of errors in the data. The formulas are simple to calculate and some possible strategies for their use are discussed.

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