Dynamics modifications

Mixing the additive in the eluent used as a mobile phase can also modify the chromatographic system (dynamic modification), but the use of modified adsorbents has led to an improvement of resolution. Example works include that by Armstrong and Zhou [11], who used a macrocyclic antibiotic as the chiral selector for enantiomeric separations of acids, racemic drugs, and dansyl amino acid on biphenyl-bonded silica. 

The fact that px is a semidirect product of these two subalgebras is a necessary condition to support such an interpretation. Indeed, since we have [p,p] = p, we see that the role played by the generators of symmetries p is to impress dynamical modification on the observables p giving rise to other observables. As a consequence, the non-commutativity between the observables is a matter of measurement. In the case we are studying in this section we have [p,p] = p resulting in a quantum theory. For the sake of consistency, we expect to derive a classical TFD theory with an algebra similar to pr but in which [p,p] = 0. (This result has been explored in Ref.(L.M. Silva et.al., 1997))... 

The potential substrates for histone phosphorylation include N-terminal serine and threonine hydroxyl groups of H2A, H3, and H4 the N- and C-terminal tails of HI and the unique C-terminal of H2AX [19,29] (see Fig. 6). Similar to acetylation, phosphorylation appears to be a dynamic modification that transduces on/off signals to nuclear modulators. Enzymes implicated in regulating this pathway include the cyclin-dependent kinases and mitogen activated protein kinases, and the antagonistic phosphatase 1 [158,159]. 

Similarly, the authors also examined the stabilization effect of dynamic modification of a U-NH -appended RNA aptamer that forms a kissing complex with the HIVl transactivation-responsive RNA element TAR. In this dynamic library, 2-chloro-6-methoxy-3-quinofinecarboxaldehyde (Rd) was incorporated in place of benzaldehyde (Ra). After equilibration of the U-NHj-substituted aptamer and aldehydes Rb-Rd in the presence of the TAR RNA target, it was found that the nalidixic aldehyde Rc-appended RNA was amplified 20%, and accompanied by an increased (Fig. 3.17). Interestingly, the nalidixic aldehyde Rc was selected in both DNA and RNA complexation experiments. 

As discussed for N-myristoylation and S-prenylation, even S-acylation of proteins with a fatty acid which in the vast majority of cases is the C16 0 palmitic acid, plays a fundamental role in the cellular signal-transduction process (Table l). 2-5 14 While N-myristoylation and S-prenylation are permanent protein modifications due to the amide- and sulfide-type linkage, the thioester bond between palmitic acid and the peptide chain is rather labile and palmi-toylation is referred to as a dynamic modification. 64 This reversibility plays a crucial role in the modulation of protein functions since the presence or absence of a palmitoyl chain can determine the membrane localization of the protein and can also be used to regulate the interactions of these proteins with other proteins. Furthermore, a unique consensus sequence for protein palmitoylation has not been found, in contrast to the strict consensus sequences required for N-myristoylation and S-prenylation. Palmitoylation can occur at N- or C-terminal parts of the polypeptide chain depending on the protein family and often coexists with other types of lipidation (see Section 6.4.1.4). Given the diversity of protein sequences... 

Bouvier M, et al. Palmitoylation of G protein-coupled receptors a dynamic modification with functional consequences. Biochem Soc Trans 1995 23(1) 116-120. 

Dynamic modification (using extreme values of pH or competing ions)... 

Some information on various buffer additives was given in Section III.C. A more detailed discussion of dynamic modification of fused silica capillaries is provided here. This entails transitory modification of the capillary wall by utilizing certain buffer additives. Some examples are... 

Wilson CJ (1995a) Dynamic modification of dendritic cable properties and synaptic transmission by voltagegated potassium channels. J Comput Neurosci 2 91-115. 

Covalent dynamers may also present a range of unusual properties such as crossover component recombination between neat films in dynamic polymer blends [61], soft-to-hard transformation of polymer mechanical properties through component incorporation [62], and dynamic modification of optical properties (Fig. 6) [63],... 

Fig. 20 Stabilization of triple helices via dynamic modification of uridine...

Bouvier, M., Moffett, S., Loisel, T. P., Mouillac, B., Hebert, T, Chidac, P. Palmitoylation of G-protein coupled receptors A dynamic modification with functional consequences. Bio. Chem. Soc. Trans., 1995, 23, 116-120. 

Hermansson, J., Hermansson, 1. Dynamic modification of the chiral bonding properties of a CHIRAL-AGP column by organic and inorganic additives. Separation of enantiomers of anti-inflammatory drugs, J. Chromatogr. A, 1994,... 

Hoglund, P. Nilsson, L.G. Liquid chromatographic determination of diltiazem and its metabohtes using trans isomers as internal standards, with dynamic modification of the solid phase by addition of an amine to the mobile phase. J.Chromatogr., 1987, 414, 109-120 Johnson, S.M. Wahba Khalil, S.K. An HPLC method for the determination of diltiazem and desacetyldiltiazem in human plasma. J.Liq.Chromatogr., 1987,10, 673—685 [plasma extracted desacetyld-... 

Hermansson, J. Grahn, A. Optimization of the separation of enantiomers of basic drugs. Retention mechanisms and dynamic modification of the chiral bonding properties on an Ui-acid glycoprotein column. J.Chromatogr.A, 1995, 694, 57-69... 

As mentioned above ion-pair partition is automatically involved in chromatography of anionic solutes on dynamically coated phases using long chain quaternary ammonium ions. The possibility of ion-pair partition of cationic solutes, however, has not been investigated and problems might occur due to the apparent possibility of ion-pair formation between the counterion and surfactant ions, as well as the solute in question. A dynamic modification of the support surface (alumina), using... 

A simulation exercise can show the distillation column has more effect on the response than the reactor, because of higher order dynamics. Modifications on reactor, as increasing the kinetics and simultaneously reducing the volume, will improve only... 

The three Trp residues in NSCP can be used to monitor structural and / or dynamical modifications with the state of ligation of the protein. 

Modifiers of EOF Two approaches can be taken to modify EOF in an attempt to enhance resolution covalent coverage or dynamic modification of the capillary wall. Many examples of both covalent " and dynamic coatings are found in the literature, and... 

Note an important specific feature of GSC, namely that the retention of compounds depends on the nature of the mobile phase. The replacement of light carrier gases by heavy gases leads to dynamic modification of the adsorbent surface, to a decrease in the coefficients of distribution of the compounds being analyzed in the solid adsorbent-gas system, and, hence, to a decrease in retention times. 

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