High resolution INS

Due to the rather stringent requirements placed on the monochromator, a double or triple monocln-omator is typically employed. Because the vibrational frequencies are only several hundred to several thousand cm and the linewidths are only tens of cm it is necessary to use a monochromator with reasonably high resolution. In addition to linewidth issues, it is necessary to suppress the very intense Rayleigh scattering. If a high resolution spectrum is not needed, however, then it is possible to use narrow-band interference filters to block the excitation line, and a low resolution monocln-omator to collect the spectrum. In fact, this is the approach taken with Fourier transfonn Raman spectrometers. 

One variation in dye laser constmction is the ring dye laser. The laser cavity is a reentrant system, so that the laser light can circulate in a closed loop. The ring stmcture provides a high degree of stabiUty and a narrow spectral width. The spectral width of a conventional dye laser on the order of 40 GH2 is narrowed to a value as small as a few MH2. Such systems offer very high resolution in spectroscopic appHcations. 

The protein-DNA interactions have been analyzed in detail at high resolution in the complex between the 434 repressor fragment and the ORl containing 20mer DNA. A pseudo-twofold symmetry axis relates the halves of this complex. The symmetry is not exact since the nucleotide sequence of the DNA is slightly different in each half (see Table 8.2). However, the interactions between one protein subunit and one half of the DNA are very similar to those between the second subunit and the other half of the DNA since most of the bases that interact with the protein are identical in both halves. Details of the interaction are very similar to those in the complex with the palindromic synthetic 14mer of DNA shown in Figures 8.14 and 8.15. The base pairs at one end of the DNA, 1-14, 2-13, etc. are called base pairs 1, 2, etc. 

Despite considerable efforts very few membrane proteins have yielded crystals that diffract x-rays to high resolution. In fact, only about a dozen such proteins are currently known, among which are porins (which are outer membrane proteins from bacteria), the enzymes cytochrome c oxidase and prostaglandin synthase, and the light-harvesting complexes and photosynthetic reaction centers involved in photosynthesis. In contrast, many other membrane proteins have yielded small crystals that diffract poorly, or not at all, using conventional x-ray sources. However, using the most advanced synchrotron sources (see Chapter 18) it is now possible to determine x-ray structures from protein crystals as small as 20 pm wide which will permit more membrane protein structures to be elucidated. 

Fig. 4. The normal nocturnal migrating motor complex (MMC) recorded in the duodenum (upper tracing) and proximal jejunum (lower tracing) of a 91-year-old healthy woman. A short period is shown in high resolution in the lower panel. Phase III is preceded by phase II with some contractile activity, usually limited during sleep, and succeeded by contractile quiescence, phase I. The sequence of phase III-I-II-III constitutes one MMC cycle, and recurs during fasting (modified with permission from Husebye and Engedal [79]).

Tetramethylplumbane mixtures with tetramethylstannane were studied at 2 K by high resolution INS (inelastic neutron scattering), revealing rotational tunnelling transitions for the methyl groups146. 

Direct heteronuclear chemical shift correlation Conceptually, the 2D J-resolved experiments lay the groundwork for heteronuclear chemical shift correlation experiments. For molecules with highly congested 13C spectra, 13C rather than XH detection is desirable due to high resolution in the F% dimension [40]. Otherwise, much more sensitive and time-efficient proton or so-called inverse -detected heteronuclear chemical shift correlation experiments are preferable [41]. 

Collectors are placed at the focal points. At sufficiently high vacuum genuinely large separation factors are obtained in electromagnetic separators (high resolution in the language of the mass spectroscopist), but this important advantage is offset by sev-... 

Baldino F, Chesselet MF, Lewis ME. 1989. High resolution in situ hybridization histochemistry. Methods Enzymol 168 761-778. 

Since both the bubble cell and the Z-cell need high resolution in order to observe the sensitivity increase, test whether you can avoid the use by a clever injection procedure such as sample stacking or transient ITP (isotachophoresis) instead. Further information on detection approaches is provided in Chapters 3, 5, and 15. 

It should be noted that the experimental set of structure amplitudes for Ge was obtained up to sinOA = 1.72 A. This allowed not only to refine more exactly the scale and temperature factors but also provided high resolution in the electron density, the ESP maps and the Laplacian of the electron density. For example the inner electron shells of the core in Ge can be seen in figure 11. 

Yamanaka, K. (1995). New approaches in acoustic microscopy for noncontact measurement and ultra high resolution. In Advances in acoustic microscopy, Vol. 1 (ed. G. A. D. Briggs), pp. 301-42. Plenum Press, New York. [226,292]... 

With long acquisition times and a correspondingly high resolution in F2, the experiment may be particularly useful in cases where the H spectrum is overcrowded. The corresponding "C spectra are usually well resolved and the separation of the cross peaks in FI of such 2D experiments can be used to extract the corresponding H subspectra (rows of the 2D matrix) which may then be analysed separately and allow to obtain H chemical shifts and H/ H coupling constants even for such demanding cases. 

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