Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

X-ray Crystallography

X-ray Crystallography

The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...

$X-ray Diffraction of Biological Samples$ 01:10

X-ray Diffraction of Biological Samples

X-ray diffraction or XRD is an analytical tool that utilizes X-rays to study ordered structures such as crystalline organic and inorganic samples, polycrystalline materials, proteins, carbohydrates, and drugs.
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are scattered by the electron clouds around the sample atoms. The X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal...

$Interference and Diffraction$ 02:18

Interference and Diffraction

Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a resulting wave with enhanced amplitude is produced. This is known as constructive interference. In this case, the two waves interacting are in phase with each other.

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same authorSame journal

Scotty: lattice coincidences for macromolecular crystallographic phasing.

Acta crystallographica. Section D, Structural biology·2026

Same authorSame journal

Scotty: lattice coincidences in the Protein Data Bank.

Acta crystallographica. Section D, Structural biology·2026

Same author

AlphaFold as a prior: experimental structure determination conditioned on a pretrained neural network.

Nature methods·2026

Same author

Xtricorder: a likelihood-enhanced self-rotation function and application to a machine learning-enhanced Matthews prediction of asymmetric unit copy number.

Acta crystallographica. Section D, Structural biology·2025

Same author

Model Quality Assessment for CASP16.

Proteins·2025

Same author

Highlights of Model Quality Assessment in CASP16.

Proteins·2025

Search research articles

Related Experiment Video

Updated: Oct 31, 2025

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Published on: October 2, 2017

Likelihood-based estimation of substructure content from single-wavelength anomalous diffraction (SAD) intensity

Kaushik S Hatti¹, Airlie J McCoy¹, Randy J Read¹

¹Cambridge Institute for Medical Research, Department of Haematology, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, United Kingdom.

Acta Crystallographica. Section D, Structural Biology

|July 1, 2021

Summary

This study introduces a new method to estimate anomalous signal strength in single-wavelength anomalous diffraction (SAD) phasing, improving substructure determination accuracy even with low signal-to-noise ratios.

Keywords:

likelihood phasing single-wavelength anomalous diffraction substructure

More Related Videos

Sample Preparation and Transfer Protocol for In-Vacuum Long-Wavelength Crystallography on Beamline I23 at Diamond Light Source

Sample Preparation and Transfer Protocol for In-Vacuum Long-Wavelength Crystallography on Beamline I23 at Diamond Light Source

Published on: April 23, 2021

$Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene$

Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

Published on: August 22, 2017

Related Experiment Videos

Last Updated: Oct 31, 2025

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Published on: October 2, 2017

Sample Preparation and Transfer Protocol for In-Vacuum Long-Wavelength Crystallography on Beamline I23 at Diamond Light Source

Sample Preparation and Transfer Protocol for In-Vacuum Long-Wavelength Crystallography on Beamline I23 at Diamond Light Source

Published on: April 23, 2021

$Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene$

Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

Published on: August 22, 2017

Area of Science:

Structural Biology
Crystallography
Biophysics

Background:

Single-wavelength anomalous diffraction (SAD) phasing is crucial for determining protein structures.
Low signal-to-noise ratios in experimental data present a significant challenge for SAD phasing.
Accurate estimation of substructure content is vital for successful SAD phasing outcomes.

Purpose of the Study:

To develop a novel method for accurately estimating the anomalous scattering contribution from measured intensities.
To provide a reliable measure of the intrinsic anomalous signal in SAD experiments.
To improve the accuracy of substructure determination in challenging low signal-to-noise conditions.

Main Methods:

Development of a likelihood-based target function to estimate anomalous scattering strength.
Determination of a complex correlation parameter relating Bijvoet mates as a function of resolution.
Accounting for correlated errors in intensity measurements, including those from radiation damage.

Main Results:

The proposed method provides a novel measure of the intrinsic anomalous signal.
Refined complex correlation parameters can be interpreted in terms of atomic content before substructure knowledge.
Maximum-likelihood estimation of substructure content showed high correlation (R=0.72) with phasing results in 357 SAD cases.

Conclusions:

The developed likelihood-based target function accurately estimates anomalous signal strength.
This method enhances the reliability of substructure determination in SAD phasing, especially in low SNR scenarios.
The approach offers a robust way to assess data quality and predict phasing success.