X-ray Diffraction

X-ray diffraction is a technique for studying the characteristics of matter such as macro molecules, crystals, powders, polymers, fibers, etc. When X-rays pass through matter, they interact with the electrons in the atoms and become scattered. If the atoms are organized in planes (i.e., the matter is crystalline) and the distances between the atoms are of the same magnitude as the wavelength of the X-rays, constructive and destructive interference occurs and a diffraction pattern forms. For studying a wide variety of matter, different types of X-rays, i.e., monochromatic, pink beam (narrow band of X-rays), or white beam (wide band of X-rays), are used.  

X-ray Crystallography

The theory of crystallography was developed soon after X-rays were first discovered by W. C. Roentgen in 1895. Since then the theory has gone through continual development in data collection instrumentation and data reduction methods. In recent years, the advent of synchrotron radiation sources, micro-focus X-ray tubes, high-efficiency optics, area detector-based data collection instruments, and high-speed computers have dramatically enhanced the efficiency of crystallographic structural determination.  

For crystal structure determination, the integrated intensities of the diffraction peaks (as shown in the image), which are created using monochromatic X-rays, are used to reconstruct the electron density map within the unit cell in the crystal. To achieve high-accuracy in the reconstruction, which is achieved by Fourier transforming the diffraction intensities with the appropriate phase assignment, a high-degree of completeness and redundancy in diffraction data is necessary. In other words, all possible reflections are measured multiple times in order to reduce systematic and statistical errors.

The most efficient way to do this is by using a CCD detector, which can collect diffraction data in a large solid angle. Today X-ray crystallography is widely used in materials and biological research. Structures of very large biological machinery (e.g., protein and DNA complexes, virus particles) have been solved using this method.

Recommended products include:

Quad-RO

• Compact detector design with Industry standard firewire (IEEE 1394a) interface
• Electronically balanced quadrants to deliver extremely uniform raw image
• Two readout speeds / port
• Four port and single port readout options
• On board memory to guarantee loss free image

PI-SCX

• Patented fiberoptic-coupling preserves highest possible resolution
• 16-bit digitization provides wide dynamic range and signal-to-noise ratio
• High sensititivty provides the ability to image very faint diffracting samples

PIXIS-XF

• Proprietary fiber-optic coupling preserves highest resolution
• Flexible design allows phosphor removal for system optimization
• Compact design with USB 2.0 interface and LINUX support