Aggregation irreversible

It is assumed that irreversible aggregation occurs on contact. The rate of coagulation is expressed as the aggregation flux J of particles towards a central particle. Using a steady-state approximation, the diffusive flux is derived to be... 

Coagulation a relatively irreversible aggregation often associated with the primary minimum of a potential energy diagram of two approaching particles. Particles are held together closely. 

Analytical approaches to obtain the agglomerate size distribution are possible for well-mixed systems and when the rate of aggregation of clusters is defined by simple functions. In general, irreversible aggregation in well-mixed systems is described by Smoluchowski s coagulation equation, which... 

Fig. 15. Thermal denaturation of triosephosphate isomerase with FTIR (upper left), second-derivative FTIR (upper right), and VCD (bottom) showing irreversible aggregation effects. The IR shift from a simple maximum at 1650-1640 cm-1 to a lower frequency distorted to low wavenumber is seen to be irreversible when the original spectrum is not recovered. The second-derivative result makes the changes more dramatic and shows the original native state spectrum to be more complex (negative second derivatives correspond to peak positions). Loss of structure is even more evident in the VCD, which loses most of its intensity at 60°C.

From the equation (1) p decrease at Df reduction follows, as always Djmacromolecular coil inner regions and results to the fuller chemical transformations, i.e., to conversion degree Q increase. Besides, it is known [4], that at macromolecular coil formation by irreversible aggregation mechanisms in its central part... 

It should be emphasized that the assembly of histone fibers is a completely reversible process (Sperling and Bustin, 1975). We attribute the irreversible aggregates obtained in some pair preparations (Nicola et al., 1978 Lewis, 1976) to failure to follow a preparation technique similar to that described in Section II,D,1. 

It should be noted that the unfolding kinetics can sometimes involve quite complex unfolding schemes of different substates in equilibrium with the native state. Staphylococcal nuclease is an example of such behavior, known to unfold with three different substates that exhibit an equilibrium that does not appear to shift with temperature.49 Irreversible aggregation processes of proteins have been known to involve first- or second-order reactions.132141 The mechanism of recombinant human interferon-y aggregation is an example where thermodynamic and kinetic aspects of the reaction provided a powerful tool for understanding the pathway of instability and permitted a rationale for screening excipients that inhibited the process.141... 

White clot syndrome - Rarely, patients may develop new thrombus formation in association with thrombocytopenia resulting from irreversible aggregation of platelets induced by heparin, the so-called white clot syndrome. The process may lead to severe thromboembolic complications. Monitor platelet counts before and during therapy. If significant thrombocytopenia occurs, immediately... 

Age gelation is an aggregation phenomenon that affects shelf-stable, sterilized dairy products, such as concentrated milk and UHT milk products. After weeks to months of storage of these products, there is a sudden sharp increase in viscosity, accompanied by visible gelation and irreversible aggregation of the micelles into long chains forming a three-dimensional network. The actual cause and mechanism is not yet clear however, some theories exist. 

Fig. 24.4 Mechanism of enzyme inactivation at an aqueous-organic interface. Step 1 reversible enzyme adsorption to the interface and concomitant enzyme structural rearrangement at the interface. Step 2 unfolding of enzyme molecule at the interface. Step 3 desorption of inactivated/un-folded enzyme molecules from the interface. Step 4 irreversible aggregation and precipitation of inactivated enzyme. (From [34])...

These products can be viewed most simply and. in most cases, with sufficient as two-phase systems in which the dispersed panicles are steadily and irreversibly aggregating according to a second-order rale law. Thus, where C is the number of particles per cubic centimeter Ian aggregate of many primary particles being counted as one panicle) at time I. and where Co is the number of particles per cubic centimeter al zero time, and A is a constant. C depends on t according to... 

In conclusion, we should mention that in the description of the behavior of distinct alkoxides it appears very difficult to distinguish the influence of each of the two factors — the inhomogeneity of the molecular composition and the presence of oxoderivatives. In certain cases the reversibility of transformations and reproducibility of the properties of the oligomeric forms can be used as criterion (as for Al(OPr )3) indicating the constant chemical composition and the dominance of the first factor. At the same time, an irreversible aggregation/ polymerization can result from the both factors. 

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