Resolution case studies

One of the most striking results that has emerged from the high-resolution crystallographic studies of these icosahedral viruses is that their coat proteins have the same basic core structure, that of a jelly roll barrel, which was discussed in Chapter 5. This is true of plant, insect, and mammalian viruses. In the case of the picornaviruses, VPl, VP2, and VP3 all have the same jelly roll structure as the subunits of satellite tobacco necrosis virus, tomato bushy stunt virus, and the other T = 3 plant viruses. Not every spherical virus has subunit structures of the jelly roll type. As we will see, the subunits of the RNA bacteriophage, MS2, and those of alphavirus cores have quite different structures, although they do form regular icosahedral shells. 

CASE STUDY ENZYME KINETIC MODELS FOR RESOLUTION OF RACEMIC IBUPROFEN ESTERS IN A MEMBRANE REACTOR... 

In this case study, an enzymatic hydrolysis reaction, the racemic ibuprofen ester, i.e. (R)-and (S)-ibuprofen esters in equimolar mixture, undergoes a kinetic resolution in a biphasic enzymatic membrane reactor (EMR). In kinetic resolution, the two enantiomers react at different rates lipase originated from Candida rugosa shows a greater stereopreference towards the (S)-enantiomer. The membrane module consisted of multiple bundles of polymeric hydrophilic hollow fibre. The membrane separated the two immiscible phases, i.e. organic in the shell side and aqueous in the lumen. Racemic substrate in the organic phase reacted with immobilised enzyme on the membrane where the hydrolysis reaction took place, and the product (S)-ibuprofen acid was extracted into the aqueous phase. 

Progress in defining new treatments for C. difficile infection has been hindered by the heterogeneous nature of hospital-acquired diarrhea, and in particular by whether colitis and/or pseudomembranous colitis is present in individual cases. Study groups have usually been poorly defined in this context, and given the spontaneous resolution of symptoms in a proportion of cases the true efficacy of treatment approaches often remains uncertain. Enthusiasm to explore new treatment possibilities for C. difficile has been largely fuelled by the apparently high relapse rate of conventional (metronidazole or vancomycin) treatment [138],... 

The following case study contains examples of several topics discussed in previous sections, including some aspects of laser technology, laser spectroscopy and laser chemistry. A variety of lasers and laser techniques are applied in a straightforward manner to the problem of ascertaining structural and dynamical information on an excited electronic state of wide chemical interest. This information is obtained rather simply, illustrating the potential of laser techniques in the resolution of problems in solution chemistry. 

The diversity and depth of these technological advances in the field of NMR are invaluable for a wide variety of applications. Prudent decision-making is necessary to select the most advantageous NMR technologies and approaches specific for each individual application. Such selections are often made in order to overcome limitations in sensitivity or resolution, or both. The following case studies demonstrate representative examples of how modern NMR technologies and techniques have been employed to solve real-life scientific challenges. 

The geographical resolution is on the basis of NUTS (Nomenclature of Territorial Units for Statistics) areas, the regional classification of the European Union. For the German case study the NUTS3 classification (439 districts) has been used to analyse the demand allocation and fuelling station distribution as well as the regional infrastructure development. 

An extreme example of the reduction in radiation damage is that of data collection at the SRS on purine nucleoside phosphorylase. On a conventional source usually a crystal can give only one 3 A resolution still photograph before the crystal suffers serious damage. At the synchrotron three crystals will give a comptete set of 4 equivalent reflections to a resolution limit of 3 A (see case study below)... 

Case Study A High Resolution Data Collection from 6-phosphogluconate Dehydrogenase (6-PGDH) Crystals. 

Case Study B High Resolution Data from DPI on the FAST. 

Heterogenization of homogeneous metal complex catalysts represents one way to improve the total turnover number for expensive or toxic catalysts. Two case studies in catalyst immobilization are presented here. Immobilization of Pd(II) SCS and PCP pincer complexes for use in Heck coupling reactions does not lead to stable, recyclable catalysts, as all catalysis is shown to be associated with leached palladium species. In contrast, when immobilizing Co(II) salen complexes for kinetic resolutions of epoxides, immobilization can lead to enhanced catalytic properties, including improved reaction rates while still obtaining excellent enantioselectivity and catalyst recyclability. 

Shintu, L., Ziarelli, F., and Caldarelli, S. (2004). Is high-resolution magic angle spinning NMR a practical speciation tool for cheese samples Parmigiano Reggiano as a case study. Magn. Res on. Chem. 42, 396-401. 

The three case studies outlined here give some indication of the worst difficulties that have been experienced with peak resolution, and have one factor in common the presence of an additional amorphous or paracrystalline peak was suspected in each case. All three optimization programs worked well when the input parameters were well chosen, but constraints were necessary in the more difficult cases and when broad peaks were present. Judicious choice of input parameters always speeds the ultimate solution and the use of BASELINE is most helpful. 

A Case Study of a resolution of a commercial drug highlights the procedural steps of the entire resolution process. 

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