Intact system, characterization

Systemic Behavior That Must be Accounted For A Representation That Accounts for Systemic Behavior Characterization of Molecular Elements Characterization of the Intact System Steady-State Behavior Dynamic Behavior... 

The dynamic behavior of the intact system is characterized by the solution of Eqn. (30). In some cases this can be obtained as an explicit solution in terms of elementary mathematical functions (e.g., Voit and Savageau, 1984). However, in most instances there is no solution of this type, and one must rely on computer-generated solutions in which particular numbers for rate constants, kinetic orders, and initial values of the concentration variables must be specified. Even if some of these numbers are unknown for a particular system, one can explore the potential repertoire of dynamic behavior by systematically varying the values of the parameters and solving the resulting equations for the system (e.g., see Irvine and Savageau, I985a,b). 

The Power-Law Formalism possesses a number of advantages that recommend it for the analysis of integrated biochemical systems. As discussed above, we saw that estimation of the kinetic parameters that characterize the molecular elements of a system in this representation reduces to the straightforward task of linear regression. Furthermore, the experimental data necessary for this estimation increase only as the number of interactions, not as an exponential function of the number of interactions, as is the case in other formalisms. The mathematical tractability of the local S-system representation is evident in the characterization of the intact system and in the ease with which the systemic behavior can be related to the underlying molecular determinants of the system (see above). Indeed, the mathematical tractability of this representation is the very feature that allowed proof of its consistency with experimentally observed growth laws and allometric relationships. It also allowed the diagnoses of deficiencies in the current model of the TCA cycle in Dictostelium and the prediction of modifications that led to an improved model (see above). 

A 2D system coupled with a TOF-MS detector provides not only resolution for a large number of protein components, but also yields accurate intact molecular weight information (e.g., Opiteck et al., 1997 Liu et al., 2002 Millea et al., 2005). Moreover, by splitting the effluent just prior to the MS interface, a small portion can be diverted for MS analysis, whereas the bulk of the sample can be collected for subsequent analysis, following enzymatic digestion, to provide positive identification and characterization of the proteins present in the fraction. 

Craig S, Staehelin LA. High pressure freezing of intact plant tissues. Evaluation and characterization of novel features of the endoplasmic reticulum and associated membrane systems. Eur J Cell Biol 1988 46 81-93. 

Let us consider first lipid-lipid interaction. Urry et al, showed the existence of a positive CD band at 218 m/x and a negative CD band at about 192 m/z in phosphatidyl choline and phosphatidyl ethanolamine dissolved in trifluoroethanol (86). The 192-m/z band was not characterized in detail, but the 218-m/z band is of such position and shape that the addition of lipid and protein CD bands could produce a composite CD band, and hence an ORD Cotton effect, which is red shifted. As noted by Urry, the 218-m/z CD extremum of lecithin must arise from n — 7T transitions in the fatty acid ester groups. Although the optical activities of solutions of deproteinized membrane phospholipids determined at the same concentration as in the intact membrane are negligibly small, in membranes an ordered array of lipids could greatly enhance rotation. Such an effect could yield information on the nature of lipid-lipid association. This can be tested experimentally. Halobacterium cutirubrum offers a unique system since Kates has shown that the lipids in this extreme halophile contain ether bonds rather than ester bonds (43, 44), Hence, the n — tt transition essential to the CD band at 218 m/z in phospholipids does not exist. Nevertheless, we found that the ORD... 

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