S.COSY

Baldini F., Bechi P., Bracci S., Cosi F., Pucciani F., In vivo optical-fibre pH sensor for gastro-oesophageal measurements, Sensors Actuators 1995 B29 164-168. 

Statistical analysis, such as a two-way analysis of variance may be used to test whether differences between values at various times are significant. However, statistical analyses do not provide any information about the shape, phase, amplitude, or mean level of the rhythm they merely indicates whether the data are different from random variation. In order to quantify rhythm parameters, other mathematical techniques, such as Halberg s cosi-nor model, are required. Our hypothesis assumes that the measured data follow a deterministic series model. Deterministic series are obtained when successive observations are dependent variables and any future values may be predicted firom past observations (Chatfield, 1975). 

Baldini, F. Bracci, S. Cosi, F. An extended-range fiber-optic pH sensor. Sens. Actuators, A 1993, 37-38, 180-186. 

But wait We are not quite finished. The desired payoff of all this complicated analysis is to make the answer simple, right Early in this chapter we pointed out the difficulty in fitting the coupling constant between neighboring spins. Jab- In the spectrum mentioned earlier from Prof. Hoffman s COSY spectrum of ethyl benzene, we realize the peaks along the diagonal are just what we would... 

One kind of 2D NMR is called COSY, which stands for correlated spectroscopy With a COSY spectrum you can determine by inspection which signals correspond to spin coupled protons Identifying coupling relationships is a valuable aid to establishing a molecule s connectivity... 

The CH fragment which is linked to the OH group (Sh = 5.45 ) can easily be located in the H and NMR spectra. The chemical shift values Sc =74.2 for C and Sh = 3.16 for //are read from the CH COSY plot. The H signal at S,i = 3.16 splits into a triplet (11.0 Hz) of doublets (4.0 Hz). The fact that an antiperiplanar coupling of 11 Hz appears twice indicates the diequatorial configuration (trans) of the two substituents on the cyclohexane ring 5. If the substituents were positioned equatorial-axial as in 4 or 5, then a synclinal coupling of ca 4 Hz would be observed two or three times. 

The weighting functions used to improve line shapes for such absolute-value-mode spectra are sine-bell, sine bell squared, phase-shifted sine-bell, phase-shifted sine-bell squared, and a Lorentz-Gauss transformation function. The effects of various window functions on COSY data (absolute-value mode) are presented in Fig. 3.10. One advantage of multiplying the time domain S(f ) or S(tf) by such functions is to enhance the intensities of the cross-peaks relative to the noncorrelation peaks lying on the diagonal. 

Figure 6.11 A 3D heteronuclear HMQC-COSY spectrum of a tripepiide. The o),-axis represents N chemical shifts, whereas the (Or and 88, copyright (1988), with permission from Academic Pre.ss, Inc.)...

The pulse sequences for HMQC-COSY and HMQC-NOESY experiments are presented in Fig. 6.10. The 3D HMQC-COSY spectrum of a N labeled tripeptide is shown in Fig. 6.11. Since the coherence transfer involved in this experiment is N([Pg.362]

Fig. 2.5.8 COSY spectra of 300 mM D-xylose plus 400 mM borate at pD = 10. The spectra were recorded at 300 MHz with a single NMR microcoil using the instrumentation shown in Figure 2.5.5. (a) Continuous-flow. Flow rate = 2 pL min-1, corresponding to a reaction time t 165 s. The on-flow COSY is highlighted by the presence of intense reactant peaks in the region of 3.0-3.5 ppm. (b) Stopped-flow. The spectrum shows very weak reactant cross...

Figure 18. A 0.2-s delayed COSY spectrum of the aliphatic region of 10 (2mg, CDCLj). Long-range "W-type" coupling of 19 and 21 axial protons to 30-CHj and coupling across the gem dimethyls from I9eq to 21 eq establish the position of oxidation at C-22. The spectrum was obtained under conditions similar to those in Figure 1, except that 32 transients were acquired for each of 128 x 512 data point spectra (17).

Whereas spin decoupling, COSY and TOCSY techniques are used to establish connectivities between protons through bonds, techniques that make use of the nuclear Overhauser effect (NOE), such as 1-D NOE and NOESY, 1- and 2-D GOESY, 1- and 2-D ROESY, can establish connectivities through space. Before looking at these techniques in detail, it s worth spending a little time considering the NOE phenomenon itself - in a nonmathematical manner, of course ... 

Figure 18 Quantitative

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