Deconvolution efficiency

Enantioresolution in capillary electrophoresis (CE) is typically achieved with the help of chiral additives dissolved in the background electrolyte. A number of low as well as high molecular weight compounds such as proteins, antibiotics, crown ethers, and cyclodextrins have already been tested and optimized. Since the mechanism of retention and resolution remains ambiguous, the selection of an additive best suited for the specific separation relies on the one-at-a-time testing of each individual compound, a tedious process at best. Obviously, the use of a mixed library of chiral additives combined with an efficient deconvolution strategy has the potential to accelerate this selection. 

An advantage of the microbore gas chromatrography/time-of-flight mass spectrometry (GC/TOFMS) method over the other two approaches is that separation efficiency need not be compromised for speed of analysis. The rapid deconvolution of spectra ( scan rate ) with TOFMS makes it the only MS approach to achieve several data points across a narrow peak in full-scan operation. However, the injection of complex extracts deteriorates performance of microbore columns quickly, and an increased LOD and decreased ruggedness result. Microbore columns may be used in water analysis if the LOD is sufficiently low, but they can rarely be used in real-life applications to complicated extracts. 

If we consider only a few of the general requirements for the ideal polymer/additive analysis techniques (e.g. no matrix interferences, quantitative), then it is obvious that the choice is much restricted. Elements of the ideal method might include LD and MS, with reference to CRMs. Laser desorption and REMPI-MS are moving closest to direct selective sampling tandem mass spectrometry is supreme in identification. Direct-probe MS may yield accurate masses and concentrations of the components contained in the polymeric material. Selective sample preparation, efficient separation, selective detection, mass spectrometry and chemometric deconvolution techniques are complementary rather than competitive techniques. For elemental analysis, LA-ICP-ToFMS scores high. 

To process the LC/MS data more efficiently, we have automated this deconvolution functionality using a Visual Basic macro (termed AutoME or Automated Maximum... 

The copolymer prepared without DEZ is clearly shown to be bimodal by GPC, with MJMn = 13.8 (Fig. 16). The GPC trace was deconvoluted into components of Mw 240,000 and 9600 g mol reflecting the differing propensities for hydrogen-induced termination between the two catalysts. The molecular weight distribution narrows as DEZ is added, as expected for an efficient chain shuttling polymerization ... 

An extensive mutagenesis protocol was used to probe the contribution of these observed changes in the STS fold towards cyclization specificity in CHS. Initially, an 18X mutant of alfalfa CHS was created to probe the mechanistic relevance of the structural differences observed in STS. Introduction of the pine STS primary sequence, consisting of 18 amino acid changes in areas 1-3, into alfalfa CHS results in an enzyme with similar kinetic efficiency to wild-type CHS. However, the mutant now produces resveratrol as the major product by using coumaroyl-CoA and malonyl-CoA in assays (Fig. 12.9B). Further deconvolution of the necessary... 

An efficient way of overcoming this difficulty is to use a reference fluorophore (instead of a scattering solution) (i) whose fluorescence decay is a single exponential, (ii) which is excitable at the same wavelength as the sample, and (iii) which emits fluorescence at the observation wavelength of the sample. In pulse fluorometry, the deconvolution of the fluorescence response can be carried out against that of the reference fluorophore. In phase-modulation fluorometry, the phase shift and the relative modulation can be measured directly against the reference fluorophore. 

Figure 14.2 Evolution of the photoluminescence spectra from the QDs and Cy3 dyes in the QD-MBP-Cy3 assemblies versus increasing dye-to-QD ratio n (a), along with the corresponding fractional donor loss, acceptor enhancement, donor-based efficiency, and a fit of Equation (8) versus n (b). Spectra shown were corrected for direct excitation and deconvoluted. Case of 510 nm emitting QDs is shown. Adapted from reference 28 and reprinted by permission of the American Chemical Society.

The first two sections of Chapter 5 give a practical introduction to dynamic models and their numerical solution. In addition to some classical methods, an efficient procedure is presented for solving systems of stiff differential equations frequently encountered in chemistry and biology. Sensitivity analysis of dynamic models and their reduction based on quasy-steady-state approximation are discussed. The second central problem of this chapter is estimating parameters in ordinary differential equations. An efficient short-cut method designed specifically for PC s is presented and applied to parameter estimation, numerical deconvolution and input determination. Application examples concern enzyme kinetics and pharmacokinetic compartmental modelling. 

Another problem is quantitative analysis of a multicomponent mixture, because we have to take into account the fact that only a small fraction of the components will appear as isolated peaks, in spite of using extremely efficient columns. For this reason, different deconvolution techniques have been elaborated. 

The lower half of the insert shows the heterodyne diffraction efficiency as seen by the detector. It has a random character, but the influence of the memory function is obvious when compared to the excitation. The main part of Fig. 26 shows the concentration part of the memory function g(t) h(t) after deconvolution according to Eq. (61). The amplitude of the contribution from the temperature grating is normalized to unity and contributes only to the very first data point. 

Maximum length binary sequences (MLBSs) of length N = 2l-l, where I is a positive integer, have a perfectly flat power spectrum [77]. The deconvolution in Eq. (61) can be computed very efficiently by means of a fast Hadamard transform, and they have, for example, been employed for Hadamard NMR spectroscopy [78]. 

Compared to the simplicity of the relative method, with its simple measurement equation, there is a hidden complexity in the k0 method complex algorithms, dedicated software for reactor neutron fluxes and gamma ray measurement efficiency and many problems associated with spectrum deconvolution. The method relies on a complex set of written standards which are not always fully understood by the average user. It uses non-transparent instrumentation and measurement processes. In short the method becomes, forgive the terminology, non-traceable to the user and this is, I believe, worse than non-traceable to SI units. 

Although not identical, both the orthogonal and positional scan formatted libraries share the features that all mixtures are made at the start of the library process and only individual compound synthesis is required after the first screening of mixtures. This is an extra initial effort with regard to the synthesis of mixtures when compared to an iterative method. The advantage is that no intermediate mixture syntheses will be required. If prepared in sufficient quantity, the library can be screened over a large number of assays, and the added effort of initial mixture syntheses will be translated into an efficiency in deconvolution relative to the continual resynthesis of mixtures with iterative deconvolution. 

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