Charge-coupled device, plate

One very important device is the plate reader, which can be rate limiting in HTS. Most laboratories use multimodal readers that can detect various forms of fluorescence as well as luminescence and absorbance. The traditional readers are photomultiplier-based devices that usually read from one well to the next. This process can take considerable time for 384-well and higher-density plates. A more desirable HTS reader type images the entire plate with a charge-coupled device (CCD) camera. The latter device is usually a faster reader for 384-well and higher-density plates. Imagers can capture significant cross talk from one well to another, but with proper set up, they can produce data of equal quality. 

Except for in house preliminary studies, the intensities of X-rays diffracted by hydrogenase crystals are now usually obtained with synchrotron radiation (Fig. 6.2) and detected by image plate or charge coupled device (CCD) detectors. To limit the damage induced by the powerful photon flux of synchrotrons, the crystals are usually mounted in a small loop, flash cooled in either liquid propane or nitrogen and stored... 

Charge injection device (CID) and charge-coupled device (CCD) detectors can be used to monitor large portions of the spectrum in multiple orders by taking an electronic photograph. They are analogous to photographic plates which were used in the earliest spectrometers. A typical... 

So far, we have seen that if we measure the Bragg angle of the reflections and successfully index them, then we get information on the size of the unit cell and, if it possesses any translational symmetry elements, also on the symmetry. In addition, we have seen that the intensity of each reflection is different and this too can be measured. In early photographic work, the relative intensities of the spots on the film were assessed by eye with reference to a standard, and later a scanning microdensitometer was used. In modern diffractometers, the beam is intercepted by a detector, either a charge coupled device (CCD) plate or a scintillation counter, and the intensity of each reflection is recorded electronically. 

FIGURE 11.2 Photomultiplier tube (PMT) and charge-coupled device (CCD) imaging systems, (a) In PMT-based readers, the excitation beam travels through an excitation filter and is reflected to the sample well via a dichroic mirror. The emission beam travels through the dichroic mirror and emission filter, and is then read by the detector. This sequence repeats for each sample well, (b) For CCD-based readers, a camera records an image of an entire plate. 

Chemiluminescent assays are conventionally monitored using photomultiplier-based instruments. However, portable instruments are becoming available that use as photodetectors silicon photodiodes, charge-coupled devices, and instant photographic or x-ray film (58, 63-68). Spacially resolved, quantitative light measurements are pcirticularly advantageous for assays based on membranes or microtiter plates. 

Alongside improvements in synchrotron sources, X-ray detectors have improved enormously. Up to the early 1990s X-ray film was the detector of choice at synchrotrons because of its high spatial resolution, despite its poor efficiency and low dynamic range. Imaging plate and charge coupled device (CCD) detectors swept film aside in the early-to-mid 1990s. 

Charge-coupled devices have been used as detectors in planar chromatography, although more applications have been found in quantitative analysis. Videodensitometers have been used to measure the absorption or the fluorescence of a separated spot on a TLC plate. 

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