Resolution of crystals

The principal cause of poor image quality using CLSM is poor dissolution of the dyes, especially Nile Blue. In the method as described, Nile Red co-crystallizes with the fat crystals and, thus, a higher resolution of crystal surface is obtained. However, it is difficult to distinguish solid from liquid fat with only Nile Red. Nile Blue is necessary because it is dissolved in the liquid phase and provides fluorescence for contrast. As a result, the quality of images is very much improved. The disadvantage of Nile Blue is its low solubility. Special attention should be paid to sufficiently dissolving the dye at 60°C. 

Several reaction mechanisms, alternative to the retro-aldol cleavage, have been proposed on the basis of kinetic, stereochemical, and reaction specificity studies and exhaustively reviewed. However, only the relatively recent resolution of crystal structures of the enzyme from several sources " and characterization of site-specific mutants have resolved some of the crucial questions concerning the catalytic mechanism of SHMT. 

The resolution of crystal spectrometers is traditionally expressed as the resolving power, which is the inverse of the energy resolution ... 

In the subsequent sections, we will leam how to cormect to databases using java or web-based programming methods. For example, it is easy to list all the PDB ID, authors, title, and resolution of crystal stractures from PDB database entries. 

Thus, such limitations together with the requirement of high resolution certainly lower the expectations linked to future differential crystal structures of modified reaction centers, in particular of those from Rb. sphaeroides, as long as the native structure is only resolved to Furthermore, the resolution of crystals from modified reaction centers might suffer from additional complications, such as an increase of structural or energetic inhomogeneity and stability problems, as previously encountered in e.g. borohydride treated reaction centers from Rb. sphaeroides (Allen et al., private communication). 

The resolution of the y-camera is determined by both the collimator and the crystal/photomultipher tube combination. In general, the resolution is significantly poorer than that of other modaUties such as magnetic resonance imaging (mri) and x-ray computerized tomography (ct). For single-photon... 

The resolution of sec.-octyl alcohol was first described by Pickard and Kenyon. The method employed by these authors differed from the foregoing in the following respects. The brucine salt of sec.-octyl hydrogen phthalate was crystallized several times from acetone until it reached optical purity and was then decom-... 

Wark, Whitlock, and co-workers [72]-[75] extend these ideas in shock compression of < 111 >-oriented silicon single crystals. The method of producing the shock wave differs from previous X-ray diffraction studies, but the basic concepts are the same. Higher X-ray fluences result in a time resolution of 0.05-0.1 ns. This permits a sequence of exposures at various irradiances and delay times, thus mapping the interatomic spacing of the shock-compressed surface as a function of time. 

The crystallographic world was stunned when at a meeting in Erice, Sicily, in 1982, Hartmut Michel of the Max-Planck Institute in Martinsried, Germany, displayed the x-ray diagram shown in Figure 12.12. Not only was this the first x-ray picture to high resolution of a membrane protein, but the crystal was... 

The amplitudes and the phases of the diffraction data from the protein crystals are used to calculate an electron-density map of the repeating unit of the crystal. This map then has to be interpreted as a polypeptide chain with a particular amino acid sequence. The interpretation of the electron-density map is complicated by several limitations of the data. First of all, the map itself contains errors, mainly due to errors in the phase angles. In addition, the quality of the map depends on the resolution of the diffraction data, which in turn depends on how well-ordered the crystals are. This directly influences the image that can be produced. The resolution is measured in A... 

As time goes on, the ultimate resolution of the SEM operated in these modes will probably level out near 1 nm. The major growth of SEMs now seems to be in the development of specialized instruments. An environmental SEM has been developed that uses differential pumping to permit the observation of specimens at higher pressures. Photographs of the formation of ice crystals have been taken and the instrument has particular application to samples that are not vacuum compatible, such as biological samples. 

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