Folding equilibrium curves

We will compare the change in the free energy per macromolecule in the formation of folded-chain (curve 1) and fibrillar (curve 2) crystals as a function of /J. Figure 8 b shows these curves calculated for the corresponding equilibrium values [a]. The increase... 

The severe headache accompanied by slight loss of equilibrium in one of several sensitive equilibrium tests after a 6.25-h (rounded down to 6 h) exposure at 0.5 ppm was considered the threshold for inability to escape and was used to derive the AEGL-2 values. A UF of 3 was used to adjust the value as no susceptible populations were identified and the threshold for narcosis for most anesthetics does not differ among individuals by more than a factor of 2 (Kennedy and Longnecker 1996 Marshall and Longnecker 1996). The intraspecies UF of 3 is supported by the steep dose-response curve for the induction of headaches namely, a 2-fold difference in the threshold concentration of PGDN and the concentration that induces headache in the majority of healthy individuals (Stewart et al. 1974). The 6-h 0.5-ppm concentration was... 

The third test is deviations from the simple V-shaped curves of rate constants versus [denaturant] that were shown in Figure 18.1 for CI2. An intermediate was detected from the denaturant dependence of the single phase for the folding of bamase (Figure 18.6) because of downward curvature. This is sometimes called rollover. The rate constant for folding for the two-state transition for bamase can be calculated as a function of [urea] from the equilibrium and rate constants... 

Fig. 5.21 The effect of PEO and PBO block lengths on the extent of chain folding of the PEO block in the equilibrium states of crystalline PEO,.PBO copolymers (o) unfolded, ( ) one fold, ( ) two folds, ( ) three folds (Mai et al. 1997). The dashed curves approximately delineate the four regions. The data points at m = 0 indicate the equilibrium state (unfolded) of low-molar-mass poly(oxyethylene)s.

It is recommended to carry out a set of SV measurements of the unfolded and the folded state ensembles as a function of RNA concentration as described earlier before collecting the data points for the entire equilibrium transition. The shape of the apparent sedimentation coefficient distribution curves (discussed in Section 5) derived from such measurements, indicate whether the initial and the final states are conformationally homogeneous. Appearance of more than one peak in such distributions would indicate the existence of distinct structural states with different hydrodynamic properties. 

Plotting the absorption at a specific wavenumber as a function of temperature produces a melt curve. By fitting the curves to a mathematical model, the melting temperature and other thermodynamic parameters can be determined. In the equilibrium limit, folding exhibits two-state behavior and the fraction unfolded fu at any temperature is related to the absorption by... 

Fig. 14 Binary phase diagram for C246H494 in octacosane. The top curve shows the equilibrium liquidus for extended-chain crystals, and the bottom line the metastable liquidus for once-folded crystals. Experimental dissolution temperatures are fitted to the Flory-Huggins equation with / = 0.15 (solid lines). Vertical dotted lines (a) and (b) indicate the concentrations at which the growth rates were determined as a function of Tc in [29]. Horizontal dotted lines indicate the temperatures at which the rates were determined in [45] as a function of concentration. G(c) at Tc = 106.3 °C, measured along line (c), is shown in Fig. 12. The shading indicates schematically the crystal growth rate (black = fast), and the dashed line the position of the growth rate minimum...

Fig. 17 Simulation of two dilution waves initiated by a small, localized perturbation. There is a fixed time period between each of the curves. The parameter is the scaled difference between concentrations of saturated solutions cE and cp2 in equilibrium with, respectively, extended and folded-chain crystals at temperature Tc, such that c = cE + (cp2 - cE) (from [46] by permission of American Institute of Physics)...

Figure 3 Dependence of the equilibrium concentration [A] of the analyte on the initial concentration [B0] (indicated by (B) in the text) of ligand added to the reaction mixture before CZE analysis. The curves are calculated for different values of the dissociation constants (between 1CT5- and 103-fold of the initial concentration of A). Reaction between analyte and ligand is according to A + B = AB. The initial concentration (A) is kept constant, and increasing initial concentrations (B) are added to the reaction mixture. All concentrations are given in arbitrary units (including the dimension of KD). (Reprinted from Ref. 22.)...

The dimer—> tetramer assembly constant Masm is very sensitive to O2 binding by human Hb, which ranges over 130,000-fold among the intermediates, in comparison with the 400-fold change in O2 binding constant under conditions of this study (pH 7.4, 21.5°C) (9). The equilibrium between free dimer and assembled tetramer is an integral property of Hb in solution, and has a marked impact on the O2 binding curve observed experimentally. 

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