Relaxation component

Fig. 12.2. Free energy data for electron transfer between the protein cytochrome c and the small acceptor microperoxidase-8 (MP8), from recent simulations [47]. Top Gibbs free energy derivative versus the coupling parameter A. The data correspond to solvated cytochrome c the MP8 contribution is not shown (adapted from [47]) Bottom the Marcus diabatic free energy curves. The simulation data correspond to cyt c and MP8, infinitely separated in aqueous solution. The curves intersect at 77 = 0, as they should. The reaction free energy is decomposed into a static and relaxation component, using the two steps shown by arrows a static, vertical step, then relaxation into the product state. All free energies in kcalmol-1. Adapted with permission from reference [88]...

The non-mono-exponentiality of the transverse relaxation in muscle and meat has most often been solved by decomposing the relaxation decay into two or three exponential components. In general, this has resulted in the detection of a major relaxation component characterised by a time constant around 35-50 ms, which corresponds to approximately 80-95% of the relaxation, and a slower relaxing component characterised by a time constant around 100-250 ms, which represents approximately 5-15% of the relaxation. In addition, a fast relaxing component with a time constant between 0 and 10 ms, which corresponds to about 5% of the relaxation, has been observed.9,11 The presence of three relaxation components in the... 

Ad. 3. Manipulation of intra-f extra-cellular ration. Le Rumear et al24 manipulated intra-/extra-cellular ratios and showed that an increase in vascular volume induced by nerve stimulation increased the fraction of the slow relaxation component, while reduced intra-cellular/interstitial volume induced by osmotic diuresis decreased the fraction of the fast relaxing component and increased the fraction of the slow relaxing component, which indicates that the fast and slow relaxing component can be ascribed to the intra- and extra-cellular space, respectively. 

The major relaxation component, characterised by a time constant of approximately 35-50 ms, accounting for 80-95% of the relaxation, and in the following referred to as T2i, represents water trapped within the protein-dense myofibrillar network. 

The fastest relaxing component sometimes reported, characterised by a time constant between 0 and 10 ms,9,11,28,41 and in the following referred to as T2b, is ascribed to water tightly associated with macromolecules. 

In summary, the above studies on the relationship between meat structure, composition, and transverse relaxation are consistent with the ascription assignment of the T2i relaxation component to water located in the myofibrillar protein matrix. In addition, the studies confirm that transverse relaxation is an excellent tool for obtaining information about structural features in meat. 

ST2-PT thus results in a 2D [15N, H]-correlation spectrum that contains only the most slowly relaxing component of the 2D 15N- H multiplet. The data are processed as described by Kay et al. [44] in an echo/antiecho manner. Water saturation is minimized by keeping the water magnetization along the z-axis during the entire experiment, which is achieved by the application of the water-selective 90° rf pulses indicated by curved shapes on the line H. It was reported that on some NMR instruments the phase cycle mentioned above does select the desired multiplet component. On these instruments, the replacements of S, with S, = y, x for the first FID and 9, =... 

To describe the impact of the x-values distribution type on the relative precision of relaxation rate estimates, we shall use a phenomenological factor fd. We expect it to be independent of all the other factors, but dependent upon the type of relaxation rate quantity to be determined (for example, the fastest- or the slowest-relaxing component in a multi-component mixture). 

ID 13C NMR N/A Can provide a quantitative overview as to the carbon distribution. In the case of NOM, often 2D NMR is central to the interpretation of the ID NMR, which often contains considerable overlap. For quantitative data, the recycle delay (dl) should be >5 x T1 for the slowest relaxing component in the sample and inverse gated decoupling should be carried out, to prevent the transfer of XH NOE to the BC nuclei. 

Figure 10.2 The relaxation rate (1/T2s)max measured for a cured mixture of a poly(ethylene glycol) diacrylate (Mn = 700 g/mol) and 2-ethylhexyl acrylate as a function of the storage modulus at 273 K (-0.1 °C) [52]. The rubbery plateau was observed for all samples at 273 K (-0.1 °C). (1/T2s)max corresponds to the relaxation component with short decay time that was measured at 323 K (50 °C) for partially swollen in 1,1,2,2-C2D2C14 samples. This relaxation component corresponds to the relaxation of network chains. The line represents the result of a linear regression analysis intercept = 1.1 0.3 ms-1 slope = 0.34 0.02 ms MPa)"1. The correlation...

Distinct T2 relaxation components with widely differing mean decay times suggest molecular or macroscopic heterogeneity of the material. In such cases the submolecule concept can be used to describe the relaxation behaviour [20]. In a simplified interpretation, the overall T2 relaxation decay of a heterogeneous elastomer is the weighted sum of the decays originating from the submolecules, which are defined as the network... 

T2 relaxation of oil-extended EPDM revealed two distinct relaxation components whose characteristic decay times are comparable with those of initial rubber and paraffinic oil (Figure 10.7) [74]. This suggests that the components with a short and long decay time mainly originate from the relaxation of rubbery chains and oil molecules, respectively. 

The amount of radicals in carbon black filled rubbers decreases significantly upon extraction of free rubber with the aid of a solvent containing a free radical scavenger. The extraction nevertheless causes a substantial increase in the fraction of the T2 relaxation component with the decay time of about 0.02-0.03 ms [62], This increase is apparently caused by an increase in the total rubber-carbon black interfacial area per volume unit of the rubber due to the removal of free rubber. The T2 relaxation component with a short decay time is also observed in poly(dimethyl siloxane) (PDMS) filled with fumed silicas [88], whose particles contain a minor amount of paramagnetic impurities. Apparently, free radicals hardly influence the interpretation of NMR data obtained for carbon-black rubbers in any drastic way [62, 79]. 

Figure 10.15 The decay of the transverse magnetisation (points) for ethylene-octene copolymer at different temperatures [136]. The decay was measured using the solid-echo pulse sequence. The solid lines represent the result of a least-squares adjustment of the decay using a linear combination of Weibull and exponential functions. The dotted lines represent the relaxation component with a long decay time. In the experiments the sample was heated from room temperature to 343 K (70 °C)...

Figure 15.2 2H NMR relaxation function obtained in a PDMS model network in the relaxed state, showing the two components the fast relaxing component (the curve with alternatively long and short dashes) is pseudo-solid and belongs to elastic chains (which have restricted motions), the slowly relaxing, exponential component (dashed line), is liquid-like and belongs to dangling chains. The total signal (black points) is a superposition of both contributions, which gives the fraction of dangling chains...

The relaxation dynamics (W7 in Fig. 38) is the response of the environment around Trp7 to its sudden shift in charge distribution from the ground state to the excited state. Under this perturbation, the response can result from both the surrounding water molecules and the protein. We separately calculated the linear-response correlation functions of indole-water, indole-protein, and the sum of the two. The results for isomer 1, relative to the time-zero values, are shown in Fig. 42a. The linear response correlation function is accumulated from a 6-ns interval indicated in Fig. 41a during which the protein was clearly in the isomer 1 substate. All three correlation functions show a significant ultrafast component 63% for the total response, 50% for indole-water, and nearly 100% for indole-protein. A fit to the total correlation function beyond the ultrafast inertial decrease requires two exponential decays 1.4 ps (3.6kJ/mol) and 23 ps (2.0kJ/mol). Despite the 6-ns simulation window for isomer 1, the 23-ps long component is not well determined on account of the noise apparent in the linear response correlation function (Fig. 42a) between 30 and 140 ps. The slow dynamics are mainly observed in the indole-water relaxation and the overall indole-protein interactions apparently make nearly no contributions to the slowest relaxation component. 

Since an ion is subject to a resuitant or net force, its drift velocity also must be a net drift veiocity resolvable into components. Furthermore, since each component force shouid produce a component of the overaii drift velocity, there must be three components of the net drift veiocity. The first component, which will be designated v°, is the direct result of the externally applied field only and excludes the influence of interactions between the ion and the ionic cloud the second is the electrophoretic component Vg and arises from the participation of the ion in the electrophoretic motion of its cioud finaiiy, the third component is the reiaxation field component originating from the reiaxation force that retards the drift of the ion. Since the electrophoretic and reiaxation forces act in a sense opposite to the externally applied eiectric field, it follows that the electtophoretic and relaxation components must diminish the overall drift velocity (Fig. 4.91), i.e.,... 

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