NMR data base

The software and the comprehensive NMR data base are both stored on a CD-ROM. A corresponding drive is therefore required and a hard disk with at least 100 MB spare capacity is advisable.The use of floppy diskettes for importing ID NMR data sets is possible, but this is not feasible for 2D data sets because of their size. 

The volumes in the series of Spectroscopic Techniques An Interactive Course are delivered with special versions of ID WIN-NMR and 2D WIN-NMR. They are a supplement for this course to be installed on a stand-alone PC and to be used exclusively for processing the experimental data supplied in the NMR data base. They cannot be used to process the users personal NMR data. The full version of ID WIN-NMR and 2D WIN-NMR software must be installed for this purpose and a special copy protection dongle (a WIBU key for the single user mode, or a Net-HASP key for the multi-user/network mode) must be used. Note also that for 2D WIN-NMR a standard 16-bit and a more powerful 32-bit version exist. Please refer to the description in the corresponding Bruker manuals [2.1, 2.2]. 

Note To deinstall the teaching software versions and the NMR data base activate the MS deinstallation system, select the item Bruker WIN-NMR Processing Strategies 1.1 and follow the instructions of the deinstallation program. 

Together with the WIN-NMR software a comprehensive NMR data base is delivered. The data base contains the experimental NMR data of two peracetylated carbohydrate compounds obtained from a series of ID and 2D NMR experiments. 

For the peracetylated P-D-glucose, raw and processed data is available, whereas for the oligosaccharide only the raw data for the same experiments is stored in the NMR data base on your CD- ROM. 

Fig. 2.9 shows the main directory structure and the structure of two subdirectories of the NMR data base stored on your CD-ROM as displayed by the WINDOWS File manager. If it is planned to copy the NMR data from your CD-ROM onto your hard disk to speed up further processing, the same directory structure should be established there (see 2.5.5). Note, however, that ID WIN-NMR generates additional auxiliary subdirectories (AU, DAT, NMR, PC, TMP) in the directory DEMOID on your harddisk. 

Fig. 2.9 Main directory structure of the NMR data base NMRDATA (left), of the GLUCOSEMD (middle) and of the GLUCOSBCD subdirectory (right).

The type of the Fourier transformation depends upon a series of parameters AQ mod, FT mod and MC2, which are usually adjusted either before data acquisition or are automatically adjusted to suit the acquisition parameters. Nevertheless these parameters should be inspected in the General parameter setup dialog box and adjusted if necessary, before a 2D FT is initialized. For all the data available in the NMR data base, AQ mod in t2 is qsim (the two quadrature detected signals are sampled... 

Attention With spectra measured on spectrometers equipped with digital filters (DMX, DRX spectrometers), the automatically performed phase correction (DMX Phase Corr.) will be applied twice when the newly created FID is Fourier transformed again. This will introduce the baseline roll characteristic for the data of these type of spectrometers. A first order phase correction must then be performed manually by setting the PHCl value close to -22000 for the data available in the NMR data base. 

The following guideline is restricted to H- and C NMR data and is based on the series of NMR experiments outlined in chapter 3. The same experiments have been used to obtain the data in the NMR data base. The experimental set up of these popular experiments is relatively straightforward and their combined application ha.s proved to be a very efficient and informative way of solving structural problems. A variety of additional experiments exist and these should be used if and when appropriate in solving special problems. 

It is this combination of written text, the software tools and data supplied, that make it different from other books on NMR spectroscopy and which should draw your attention to the many possibilities and the enormous potential of modem NMR. Sitting in front of your PC, which becomes your personal PC-NMR spectrometer , you experience in a very direct and practical way, how modern NMR works. According to the approved rule Learning by Doing you perform NMR experiments without wasting valuable spectrometer time, handle experimental data in different ways, plot ID and 2D spectra, analyse spectra and extract NMR parameters and learn to build up and use NMR data bases. 

To establish a CP/MAS C NMR data base for curdlan, partially crystalline solid samples were first analyzed. As shown in Table I, curdlan exists... 

The molecular model was generated using only NMR data based on the assignment of at least a major portion of all 59 residues." The cluster structure, moreover, was generated as part of the NMR structure. In addition to the conventional NOESY, NHC 3 spin coupling and H-bond (based on NH lability) constraints, the structure of the cluster and its environment benefited from the use of relaxation times [Eq. (1)] and the Cys Fe-S-Cp-H dihedral angle, < >, deduced fiom the contact shift pattern via Eq. (6), as well as short mixing time NOESY and steady-state NOEs, as structural constraints. The nature of the constraints... 

The M —H distances are approximately equal to the sum of covalent radii as shown by neutron and X-ray studies. In order to find out the precise structure of metal hydrides, both neutron and X-ray studies are needed. The distances obtained from NMR studies in the solid state based on the second moment calculated from the line shape are too small. This results from the inaccuracy of the Van Vleck equation. The Mn-H distance in [MnH(CO)5] calculated from the second moment of the Van Vleck equation is 128 pm. The longer distance (144 pm) was calculated from NMR data based on the modified Van Vleck equation. " A similar distance was calculated from electron diffraction studies in the gas phase. All these distances are lower than the sum of covalent radii which equals 157 pm. The Mn-H distance in [MnH(CO)5] obtained from neutron diffraction studies equals 160.1 pm. Similar distances were found for other hydride complexes. 

A sample of polytetrafluoroethylene, Aflon G80 (Product of Asahi Glass Company), was y-irradiated up to 40Mrad at room temperature under vacuum of 10 Pa. The irradiated sample was heated at 500 K for 40 min in order to observe only the trapped stable fluorinated alkyl radicals. The sample for the NMR study was irradiated in the same way as the sample for the ESR study. Line widths of ESR spectra of alkyl radicals at various temperatures were measured by a X-band spectrometer, and the line width and second moment of broad-line NMR spectra at various temperatures were obtained at 40 MHz. The temperature dependences of line widths (second moment) of ESR and NMR spectra are shown in Fig. 8.5., from which relaxation spectra I(t) can be obtained both from ESR and NMR data based on Eq. (8.3). values can be estimated by use of Eq. (8.7) both for ESR and NMR observations. 

---