X-Ray Crystallography: The Past and Present of the Phase Problem

2015 ◽  
pp. 3-18
Author(s):  
David Sayre
Author(s):  
Н.Л. Лунина ◽  
N.L. Lunina

Advances in the methodology of the X-ray diffraction experiments leads to a possibility to register the rays scattered by large isolated biological particles (viruses and individual cells) but not only by crystalline samples. The experiment with an isolated particle provides researchers with the intensities of the scattered rays for the continuous spectrum of scattering vectors. Such experiment gives much more experimental data than an experiment with a crystalline sample where the information is limited to a set of Bragg reflections. This opens up additional opportunities in solving underlying problem of X-ray crystallography, namely, calculating phase values for the scattered waves needed to restore the structure of the object under study. In practice, the original continuous diffraction pattern is sampled, reduced to the values at grid points in the space of scattering vectors (in the reciprocal space). The sampling step determines the amount of the information involved in solving the phase problem and the complexity of the necessary calculations. In this paper, we investigate the effect of the sampling step on the accuracy of the phase problem solution obtained by the method proposed earlier by the authors. It is shown that an expected improvement of the accuracy of the solution with the reducing the sampling step continues even after crossing the Nyquist limit defined as the inverse of the double size of the object under study.


Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 854
Author(s):  
Ki Hyun Nam

Radiation damage and cryogenic sample environment are an experimental limitation observed in the traditional X-ray crystallography technique. However, the serial crystallography (SX) technique not only helps to determine structures at room temperature with minimal radiation damage, but it is also a useful tool for profound understanding of macromolecules. Moreover, it is a new tool for time-resolved studies. Over the past 10 years, various sample delivery techniques and data collection strategies have been developed in the SX field. It also has a wide range of applications in instruments ranging from the X-ray free electron laser (XFEL) facility to synchrotrons. The importance of the various approaches in terms of the experimental techniques and a brief review of the research carried out in the field of SX has been highlighted in this editorial.


2015 ◽  
Vol 10 (9) ◽  
pp. 975-989 ◽  
Author(s):  
Heping Zheng ◽  
Katarzyna B Handing ◽  
Matthew D Zimmerman ◽  
Ivan G Shabalin ◽  
Steven C Almo ◽  
...  

1993 ◽  
Vol 26 (1) ◽  
pp. 49-125 ◽  
Author(s):  
Axel T. Brünger ◽  
Michael Nilges

Macromolecular structure determination by X-ray crystallography and solution NMR spectroscopy has experienced unprecedented growth during the past decade.


1993 ◽  
Vol 7 (1) ◽  
pp. 25-49 ◽  
Author(s):  
C.-S. Chang ◽  
G. DeTitta ◽  
H. Hauptman ◽  
R. Miller ◽  
P. Thuman ◽  
...  

2021 ◽  
Author(s):  
Keith J Flanagan ◽  
Maximilian Paradiz Dominguez ◽  
Zoi Melissari ◽  
Hans-Georg Eckhardt ◽  
René M Williams ◽  
...  

The use of halogens in the crystal engineering of porphyrin scaffolds has been a topic of strong interest over the past decades. Previously, this was focused on the introduction of a variety of halogens on the meso-phenyl groups of the porphyrin. However, investigations into the effects of direct halogenation of porphyrins at the meso-position on their crystalline architectures have not been conducted to date. Herein we have characterized a series of direct meso-halogenated porphyrins using single crystal X-ray crystallography. This is accompanied by a detailed conformational analysis of all deposited meso-halogenated porphyrins in the CCDC. In this study we have used the Hirshfeld fingerprint plots together with normal-coordinate structural decomposition and determined crystal structures to elucidate the conformation, present intermolecular interactions, and compare respective contacts within the crystalline architectures. Additionally, we have used density functional theory calculations to determine the structure of several halogenated porphyrins. This contrasts conformational analysis with existing X-ray structures and gives a method to characterize samples that are difficult to crystallize.


Physics Today ◽  
1989 ◽  
Vol 42 (11) ◽  
pp. 24-29 ◽  
Author(s):  
Herbert A. Hauptman

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