![]() ![]() Also this effect can be quantified by XRD measurements. Microstrain in the sample also results in peak broadening. This can be used to extract information about the size of the crystallites. Crystallites that are smaller than ~120 nm give broader peaks. Crystallite Size and Strain: The crystallite size of the powder has an influence on the width of the obtained peaks.This can be especially interesting under non-ambient conditions. XRD allows characterizing the dimensions of this unit cell. The smallest building block of such a regular arrangement is the unit cell of the material. Unit Cell Lattice Parameters: As mentioned above crystalline materials are regularly arranged.Quantitative Analysis: If the sample is not a pure substance, but consists of several components, it is also possible to calculate the relative amounts of the individual phases. ![]() Comparison of the obtained data with databases results in the identification of the material. This can be seen as the fingerprint of the sample. Qualitative Analysis: Every crystalline material produces a specific diffractogramm.Obtainable information from a diffractogramm: This is a plot of X-ray intensity on the y-axis versus the angle 2θ (2θ is defined as the angle between the incident and the diffracted beam) on the x-axis. The result of the measurement is a so called diffractogramm. As the wavelength in XRD experiments is known and the angles at which constructive interference occurs are measured, the use of the Bragg equation allows determining the distance between the lattice planes of the material. In words this equation can be described as follows: constructive interference occurs only if the path difference (given by 2d sinθ) is a multiple (n=1,2.) of the used wavelength of the X-ray beam. This is summarized in the famous Bragg – Equation: The magnitude of this path length only depends on the distance between the crystal planes and the incident angle of the X-ray beam. The resulting diffracted X-rays therefore have a different optical path length to travel. The incident X-ray beam is scattered at different planes of the material. Due to the crystalline nature, the atoms are arranged periodically. The dots in the graph correspond to the building blocks of a crystalline material. This is schematically shown in the next picture. This means that detectors can read-out a signal only at angles where constructive interference occurs. The higher intensity MetalJet X-rays typically extend the angular resolution limit of the visible protein data collected and provide more precise reflection positions and intensities, leading to higher resolution protein structures.The scattered X-rays from the sample interfere with each other either constructively or destructively. The narrow, focused X-ray beam is ideally suited to measuring even the smallest protein crystals, providing compact and well-defined reflections. Using the high brilliance MetalJet X-ray source makes weak diffraction data stronger, reducing experiment times and potentially reducing sample degradation. High brilliance X-ray sources, such as the Excillum MetalJet have made a greater number of protein structures and experiments possible in the home laboratory, thereby accelerating research with ease of access and convenience. Traditionally, a high brilliance synchrotron has been used to measure full protein data leading to protein structure determination, whilst home laboratory instruments have been used for protein screening to identify the preferred crystals for measurement at the synchrotron. Protein crystallographers rely on the strongest X-ray sources to combat the issues of air sensitivity, small crystals, low diffraction and densely packed reflections. At the same time, the number of atoms present in a protein structure is extremely large and the data (Bragg reflections) to be collected is very closely packed together. ![]()
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