Resolution types

P resolution type, where chirality occurs in the first substrate to enter and the product to leave the cycle. Similar profiles can be drawn for the reaction of the S-enantiomer and the deacylation reaction, F + — Q + E. 

At 6 A resolution, Type I crystals phased from derivatives prepared by soaking in PtCl2-, p-chloromercuribenzenesulfonic acid (PCMBS) and p-acetoxymercurianiline (PAMA) and using all the data within a 6 A sphere in reciprocal space. 

At high resolution, Type II crystals phased with iodine for methyl and barium for calcium ion substitutions using all the data to 4 A but only that 35% of the reflections from 4 to 2 A with the highest intensities. 

Fig. 2. (a) Front view of the conformation of the peptide chain of the inhibited nuclease at high resolution (Type II crystals), (b) Right side view of the chain conformation at high resolution. The curlicue at the upper left center represents the inhibitor pdTp. 

With the quadrupole instruments a low-resolution type spectrum is obtained. For a m/z = 200 for example, the minimum mass difference of two peaks that can be separated could be around 0.2 mass units (resolution 1000). The mass range for the quadrupoles can go as high as 2000 Dalton, but common commercial quadrupole instruments have a mass range between 2 and 1000 (some only up to 650). The quadrupoles can work in both scan mode or in SIM mode. 

The above has repercussions for component models. In component models, X is decomposed as X = X + E and in order to study the model, score plots are used. Such score plots only reflect the rows of X in the original domain (of X) if an orthonormal basis is used to express the scores. For curve resolution types of studies, it is usually more insightful to express the scores (e.g. concentrations) on the basis of the estimated spectra (Z). 

Figure 8.24 shows a scatter plot made according to Equation (8.2) for the peat example, matricized to 35 x 21, giving the particle area mode as V. The corresponding scatter plot for the PARAFAC C-loadings can be seen in Figure 8.15. The difference is not very big and the choice of using one plot or the other would often be a subjective one, but the plot in figure 8.24 has all the nice properties of a score plot from principal component analysis. In the case of the peat example, true spectral shape is not very important, but for the batch synthesis example, a true curve resolution type spectrum as in Figure 8.12 is needed for the interpretation. Loadings as in Equation (8.2) would not do as well.

Lipases are a family of enzymes that, in addition to their hydrolytic activity on triglycerides, also catalyze (trans)esterification reactions. They recognize a broad range of unnatural substrates in either aqueous or nonaqueous phase, have a high commercial availability, do not require expensive cofactors, and are easily recoverable. These factors make lipases especially interesting and they have been used extensively in, for example, asymmetric synthesis. The lipase from Pseudomonas cepacia was also targeted in a dynamic combinatorial resolution-type protocol [36]. Based on the efficient nitroaldol (Henry) reaction, DCLs of aldehydes, nitroal-kanes, and P-nitroalcohols could be easily generated (Scheme 5.9). 

As an illustration, a paraUel-consecutive asymmetric catalytic reaction of dynamic kinetic resolution type presented in Fig. 5.35 will be considered. 

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