Spectrum, absolute-value,

Comment on the phasing of die transform and produce a graph of the absolute value spectrum. 

Figure 1 Two-pulse or primary ESEEM data collected for the type-1 Cu(II) site of the Fet3p enzyme. Figure 1(a) shows the time domain data recorded under the following conditions microwave frequency, 9.6883 GHz field strength, 337.0 mT pulse power, 250 W 90° pulse length, 16 ns full width at half maximum (FWHM) sample temperature, 10 K. Figure 1(b) shows the ESEEM spectrum derived from the data of Figure 1(a) by subtraction of a biexponential decay function, application of a Hamming window function, and Fast Fourier Transformation (FFT). The absolute value spectrum is displayed...

It is therefore possible to display either one of the four real components S (o)i,0)2) etc., or to plot an absolute value spectrum S (o)i,co2) defined by ... 

In addition to the example of a single NMR line, the spectra C(w), S(cn) and the absolute-value-spectrum are shown for two more complicated systems (doublet and quartet) in Fig. 11. 

Figure 5 Contour plot of the NOESY spectrum at 360 MHz of the basic pancreatic trypsin inhibitor. The protein concentration was 0.02 M, solvent D2O, pD = 3.8, T = 18°C. The spectral width was 4000 Hz 512 data points were used in each dimension 56 transients were accumulated for each value of U. The mixing time was 100 ms. The absolute value spectrum, obtained after digital filtering in both dimensions with a shifted sine bell, is shown. NOE connectivities for selected amino acid residues are indicated by the broken lines. Reproduced with permission of Academic Press from Kumar A, Ernst RR and Wuthrich K (1980) Biochemistry and Biophysics Research Communications 95 1.

Xl.4.7 It is absolutely essential that the q>ectrum, whether collected on a pulse FT or CW spectrometer, be phased correctly before e integrals are measured. Consult the instrument manufiuturer s instructions for proper and improper spectrum phasing. Power spectrum or absolute value spectrum options must not be us. ... 

Fig. 14. (Left) Heteronuclear, correlated absolute-value spectrum of guanosine 2 -monophosphate. The p2 dimension contains the H-coupled P spectrum and the F, dimension contains the P-coupled H spectrum. The large peaks at 4.6 ppm (F,) are unsuppressed axial peaks. (Right) Phase-sensitive slices for each phosphorus transition b and c in the 2 -GMP two-dimensional spectrum. Spectra a and d are simulated for comparison with the experimental slices b and c. From Bolton and Bodenhausen (1979). Copyright 1979 American Chemical Society.

Although this eliminates negative contributions, since the imaginary part of the spectrum is also incorporated in the absolute-value mode, it produces broad dispersive components. This leads to the broadening of the base of the peaks ( tailing ), so lines recorded in the absolute-value mode are usually broader and show more tailing than those recorded in the pure absorption mode. 

In homonuclear 2D /-resolved spectra, couplings are present during <2 in heteronuclear 2D /-resolved spectra, they are removed by broad-band decoupling. This has the multiplets in homonuclear 2D /-resolved spectra appearing on the diagonal, and not parallel with F. If the spectra are plotted with the same Hz/cm scale in both dimensions, then the multiplets will be tilted by 45° (Fig. 5.20). So if the data are presented in the absolute-value mode and projected on the chemical shift (F2) axis, the normal, fully coupled ID spectrum will be obtained. To make the spectra more readable, a tilt correction is carried out with the computer (Fig. 5.21) so that Fi contains only /information and F contains only 8 information. Projection... 

Absolute-value-mode spectrum The spectrum is produced by recording the square root of the sum of the squares of the real R) and imaginary (/) parts of the spectrum R + f). 

Absorption-mode spectrum The spectrum in which the peaks appear with Lorentzian line shapes. NMR spectra are normally displayed in absolute-value mode. 

With h 6) - 1/sin 0)5(0 — Oq), one obtains the same result as given by (4.58), which implies that the anisotropy of the/factor cannot be derived from the intensity ratio of the two hyperfine components in the case of a single crystal. It can, however, be evaluated from the absolute/value of each hyperfine component. However, for a poly-crystalline absorber (0(0) = 1), (4.66) leads to an asymmetry in the quadrupole split Mossbauer spectrum. The ratio of l-Jh, as a function of the difference of the mean square amplitudes of the atomic vibration parallel and perpendicular to the y-ray propagation, is given in Fig. 4.19. 

Figure 15 HMBC and broadband HMBC spectra of cyclosporine in C6D6 recorded with the pulse sequence shown in Figure 14. (A) HMBC spectrum recorded with A = 65.0 ms and 32 scans. (B) HMBC spectrum where two subspectra of 16 scans each recorded with A = 65.0 ms and 120 ms, and co-added in absolute-value mode. (C) broadband HMBC spectrum where four subspectra of eight scans each were recorded with A = 96.7, 84.4, 81.8, and 80.8 ms, respectively, and co-added in absolute-value mode.

Figure 16 u/tro-HMBC spectrum of cyclosporine in C6D6 recorded with the pulse sequence shown in Figure 14 where four subspectra of eight scans each were recorded with A = 181.1,160.0,115.0, and 99.3 ms, respectively, and co-added in absolute-value mode. 

The intensity of absorption gives the product G , where G is the observed yield and is the molar extinction coefficient. The absolute value of was determined by Fielden and Hart (1967) using an H2-saturated alkaline solution and an alkaline permanganate-formate solution, where all radicals are converted into Mn042. They thus obtained = 1.09 x 104 M- cm1 at 578 nm, which is almost identical with that obtained by Rabani et al. (1965), who converted the hydrated electron into the nitroform anion in a neutral solution of tetrani-tromethane. From the shape of the absorption spectrum and the absolute value of at 578 nm, one can then find the absolute extinction coefficient at all wavelengths. In particular, at the peak of absorption, (720)/ (578) = 1.7 gives at 720 nm as 1.85 X 104 M 1cm 1. 

The relative intensities of the bands, i.e. the band-area ratios, are very meaningful for the interpretation of a PE spectrum since they are proportional to the relative probabilities of ionization. The absolute value of the area of a spectral band depends, among other factors to be discussed shortly, also on the density of the target, which is quite difficult to measure, so that usually the spectral intensities are given in arbitrary units. For the purpose of the analysis of the electronic structure of a molecule, the intensity ratio between the different bands is sufficient to give valuable indications. 

There are several ways to plot the impedance spectrum Z(uj) or Z(u). A common procedure is to plot the absolute value Z of the... 

FIGURE 4.14 Absorption spectrum of HONO at 277 K (adapted from Bongartz et al., 1991). Note that the absolute values of the cross sections shown here should be multiplied by 0.855 as recommended by Bongartz et al. (1994). 

---