Transitions profile

Finally, instmmental broadening results from resolution limitations of the equipment. Resolution is often expressed as resolving power, v/Av, where Av is the probe linewidth or instmmental bandpass at frequency V. Unless Av is significantly smaller than the spectral width of the transition, the observed line is broadened, and its shape is the convolution of the instrumental line shape (apparatus function) and the tme transition profile. 

The effect of organophosphorous insecticides such as methylbromfenvinfos on membrane fluidity has been studied using the fluorescence anisotropy of 1,6-diphenyl-l,3,5-hexatriene (DPH), a probe known to be located in the hydrophobic core of the bilayer, and 1,3-bis (1-pyrene) propane (Py(3)Py), a probe distributed in the outer layer region [54]. DPH revealed a broadening of the transition profile and a solidifying effect in the fluid phase of DMPC and DPPC in the presence of 50 pM insecticide. An ordering effect of the insecticide in the fluid state was revealed by Py(3)Py. In addition, the pretransition in DPPC and DMPC vesicles was abolished by the insecticide. The addition of cholesterol decreased the influence of the insecticide. It was also observed that the influence on native membranes (erythrocytes, lymphocytes, brain microsomes, and sarcoplasmic reticulum) depended on the cholesterol content of the membranes. 

Overall, the biased random walk, which places more emphasis on the motion toward the output end and less on the other directions, mimics more closely the transit profile of the experimental data. Both diffusion models, i.e., the blind and the myopic ant models, can reproduce the basic features of the real small-intestinal transit profile. 

The complexity of the SC membrane hinders such definitive interpretation, but, nevertheless, alterations in endotherms can be used to screen molecules suspected of altering membrane function. Conversely, one should note that the absence of additive-induced alterations in the phase transition profile does not rale out their perturbing effect, but rather indicates that the additive does not modify the gel phase. As described earlier, a DSC thermogram of hydrated but untreated human SC yields four endotherms, the first three of which can be identified as noncooperative lipid-associated phase transitions, while the high-temperature endotheim is attributed to keratin denaturation [33,37]. 

Although this classihcation is useful, not all small molecules produce one of these four types of DSC profiles. Whether a consistent relationship exists between the type of transition profile produced by a small molecule and its physiological effects remains to be determined. 

The transition profiles and temperatures derived from the temperature dependence of the N-H combination mode were found to strongly correlate with those derived from the temperature dependence of the C = 0 amide I band in the MIR region. The conclusion was that NIR may be used as a conformation-sensitive monitor of the thermally induced unfolding of proteins in H20 solutions. 

Figure 3.4.22 EtOH vapor adsorption istotherm curves at 5, 10, 15, 20 °C for [Cu2(bza)4(pyz)](a), Clausius-Clapeyron plot from ad- and desorption jumps (b), temperature difference between the curves at 10 and 20 °C (c), and the deduced mass-induced phase transition profile during a- 3 host crystal phase transition induced by the gas adsorption (d).

Figure 10 Solidjliquid state diagram of the sucrose-water system showing also the glass transition profile. Symbols correspond to data taken from diverse sources...

Figure 4 Optimal freeze-drying pathways for the preparation of a low-moisture sucrose preparation. AB is the glass transition profile and CD the softening temperature profile as observed by DSC. Wj is the composition of the maximally freezeconcentrated solution ab is the ice sublimation at constant temperature bed is the ideal secondary drying path (- ) data from Shalaev and (O) data from Shalaev and Franks. For details, see text...

The presence of the clotting factor II (prothrombin) at a lipid to protein molar ratio of 20, induces a shift in Tm of pure lipids such as PS, DMPC, DPPC, from 8 to 12 C for PS, from 21 to 23.5 C for DMPC and from 38 to 43°C for DPPC,as seen on Fig. 6a. These results are indicative of the binding of factor II with the pure lipids.With DMPC and DPPC, they further suggest that, at the very least, an aggregation of the vesicles does occur, the transition profile being... 

Lendero N, Vidic J, Brne P, Frankovic V, Strancar A, Podgornik A. Characterization of ion exchange stationary phases via pH transition profiles. J Chromatogr A 2008 1185(l) 59-70. 

Biological membranes arc composed of lipids and proteins, the lipids building up the bimolecular leaflet, which is the major permeability barrier, and the proteins providing the essential biological functions, The proteins can be either intrinsic proteins embedded in the lipid biiayers and having accessible polar surfaces on both sides of the bilayer, or they are mainly bound to the bilayer surface by electrostatic interactions. When proteins are incorporated into lipid bilayers or bound to the surface of the lamellae, the lipid packing in the gel phase is perturbed and the transition profiles obtained by DSC are changed in a characteristic way. Numerous studies of lipid-protein interactions have been performed in the past and the effects on the DSC transition curves have been modeled [99-104]. 

Simulations have shown that the maximum distortion of the DSC peak from the two-state transition profile occurs for [/-]tot / [rjtot = 0.5. Moreover, it has been observed that the complex shape of DSC profile does not depend on the value of the binding constant alone, but markedly depends on the product A b[r]iot at 7 d. 

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