Spectral pattern reproducibility

Spectral pattern reproducibility (ionization mode dependent). 

D. Ballon, F. A. Howe, J. A. Koutcher, M. O. Leach, J. R. Griffiths A. Heerschap, et ah, In vivo P MR spectral patterns and reproducibility in cancer patients studied in a multi-institutional trial. NMR Biomed., 2006,19,504 512. 

Unlike in the case of non-halide complexes, TDDFT and CASSCF/CASPT2 techniques lead to different results for the halide substituted molecules. As inferred from Table 14, where the representative case of [Ru(C1)(CH3) (CO)2(Me-DAB)] is illustrated, TDDFT systematically underestimates the transition energies of the halide complexes, although it reproduces the general spectral pattern well and also the increase in molar absorptivity of the main visible absorption band on going from the halide to the non-halide... 

In 1973, a few attempts were made to analyze paper in the forms of documents, prints, and watercolors. In spite of the low signal levels obtained at that time, definite reproducible spectral patterns were found... 

Fig. 33. Directions of the principal axes of the l3C chemical shift tensor of the C=0 group, helical axis, and static magnetic field, B0, and 13C NMR spectral patterns of the C=0 carbons corresponding to the orientation of the a-helix with respect to the surface of the magnetically oriented lipid bilayers. Simulated spectra were calculated using 5, =241 ppm, 22 =189 ppm, and < 33 =96 ppm for the rigid case (a), rotation about the helical axis (slow MAS) (b), fast MAS (c), magnetic orientation parallel to the magnetic field (d), an angle 8 with the magnetic field (e), and the direction perpendicular to the magnetic field (f).11 Reproduced with permission from the Biophysical Society.

The electron capture method, although very sensitive, does suffer from reproducibility problems, the ionization efficiency and mass spectral patterns being influenced by small changes in operating parameters such as the mass spectrometer ion source temperature. 

Great resemblance was found between the B3LYP/3-21G infrared spectrum of BMA-IT and the experimental spectrum [85]. The actual Raman spectral pattern was nicely reproduced, both in peak positions... 

Figure 5.13 shows the results of PCA analysis of cells exfoliated from normal patients and patients diagnosed with LSIL/HSIL [50]. Here, the results of the oral cytology are reproduced in that most of the cells from patients with dysplasia exhibit spectral abnormalities, although the cell morphology is normal (see cell images in Figure 5.13). Even more surprising is the fact that the cells from a patient with a prior diagnosis of HSIL, and subsequent treatment, still exhibit abnormal spectral patterns and cluster with the abnormal spectra.

Figure 6 Spectral pattern and relative intensities of C3S transition lines. Reproduced with permission from Tang J and Saito S (1995) Microwave spectrum of the C3S molecule in the vibrationally excited states of bending modes V4 and Vg. Journal of Molecular Spectroscopy 92.

Figure 4 Schematic view of the cylindrical (A), ribbon (B) and lamellar (C) lyotropic aggregates along with their corresponding 2 H NMR spectral patterns recorded for a potassium palmitate-ds in a mixture with 7 wt% potassium laurate and 30 wt% water. Reproduced with kind permission from Kluwer Academic Publishers from Doane JW (1985) In Emsiey JW (ed) NMR of Liquid Crystals, p414. Dordrecht Reidel.

The identification of the lipids is a very challenging task. The lack of comprehensive mass spectral libraries often limits the identification of compounds in LC-MS and shotgun methods. Some spectral libraries are available, such as the Human Metabolome Database (http /www.hmdb.ca), the METLIN Metabolite Database (http /metlin.scripps.edu) (24), and the MassBank (http /www. massbank.jp) (25). However, construction of universal spectral databases for API-MS is challenging due to the poor reproducibility and high interinstru-ment variability of fragmentation patterns. 

Standard exciton analyses (Ref. 16 also unpublished calculations by R.E. Fenna and independently by L,L. Shipman) based on the atomic coordinates published by Fenna et al. [44] produce calculated absorption and CD spectra with multiline features that resemble observed spectra in multiplicity and splitting energies. However, the observed overall spectral red-shift is not reproduced theoretically, nor is the pattern of intensity borrowing in the Qy absorption spectrum or the magnitudes and signs of Qy CD bands. These are the aiionialies that continue to plague all exciton-analytical efforts in photosynthesis. 

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