Aggregation/precipitation

Peptides can undergo a variety of degradation reactions (Fig. 6.4) [6-9], Pathways of physical degradation include aggregation, precipitation, and adsorption. Denaturation, i. e., an often-irreversible alteration of the tertiary structure of a peptide, is also considered a type of physical degradation. These physical reactions fall outside the scope of this work. 

Anions counterion binding, counterion exchange, aggregation, precipitation... 

Anionic surfactants complexation, charge neutralization, aggregation, precipitation, structure formation... 

Nonionic surfactants tend to show the opposite temperature effect As the temperature is raised, a point may be reached at which large aggregates precipitate out into a distinct phase. The temperature at which this happens is referred to as the cloud point. It is usually less sharp than the Krafft temperature.2 The phenomenon that nonionic surfactants become less soluble at elevated temperature will be important when we discuss the phase behavior of emulsions. 

Spatial variability in the abundance of phytoplankton exudates, uptake of DOM by bacteria, chemical removal processes (e.g., flocculation, deflocculation, adsorption, aggregation, precipitation), inputs from porewaters during resuspension events, and atmospheric inputs can all contribute to nonconservative behavior in estuaries. 

Such cases have been occasionally reported, but appear to the author to be not established. The polymolecular films of Harkins and Morgan (Proc. Nat. Acad. Set., II, 637 (1925)) were with substances which spread very badly and are almost certainly largely present as aggregates precipitated on the surface, not spread at all Lyons and Rideal, and Schulman and Ridcal (Proc. Roy. Soc. A, 124, 344 (1929) 130, 284 (1931)) described bimolecular films of fatty acids on alkaline solutions, but Adam and Miller (ibid., 142, 401 (1933)) found these to consist of mixtures of collapsed small aggregates, very thick, and monomolecular films. 

Another approach to circumvent poor CE CLOD is to undertake offline sample pretreatment and analyte concentration. This should be avoided, if possible, particularly for dilute protein solutions since losses to exposed surfaces (e.g., walls of microcentrifuge tubes, pipette tips, solid extraction phases, etc.) can be substantial. Furthermore, excessive handing of a concentrated solution of protein(s) can lead to denaturation, aggregation, precipitation, and, ultimately, poor analyte recovery. 

Solubility—Dissolve the macromolecule to a high concentration without the formation of aggregates, precipitate, or other phases... 

Physical stability related to denaturization processes such as unfolding, aggregation, precipitation, or self-association (major degradation pathways)... 

Hi) The procedures, where the gel chromatographic separation is combined with other, non-chromatographic, selective physico-chemical processes such as solvation, association, aggregation, precipitation, electrokinetic effects, etc. 

The protein has disappeared In this worst-case scenario, the protein has probably been denatured by the iodination procedure and as a result was aggregated, precipitated, or adsorbed (e.g., to the column that was supposed to separate the iodized protein from free iodine). A milder iodination procedure brings rescue. 

Prior to the assay, centrifuge each mAh that has to be tested (10 min at 16,000 x ) in order to pellet any aggregate/precipitate. Immediately after the centrifugation, dilute mAbl to 7.5 nMin PBS. Dilute the che-mokine to 100 nMin PBS. Dilute the AF647 anti-hIgG 1 2000 in PBS. 

Aggregation/Precipitation in Fe-Si04 Systems 5.3.4.1 Effect of Si on Fe crystallization... 

Insoluble polyplexes are the result of a two-phase system of supernatant liquid solution (containing either polycation as in Scheme 10, or DNA as in Scheme 11) or colloidal suspension (in the particular case of polymeric micelles in solution as shown in Scheme 11, case 1) from which the polyplexes precipitate. For non-sterically stabilized polyplexes, when the molar mixing ratio approaches unity or a low quantity of salt is added (screening of charges of the polyplex) [74] and therefore the electrostatic stabilization is insufficient, secondary aggregation occurs and the aggregates precipitate (this is also a function of the density of the polyplexes) (Scheme 10) [47]. 

Sol becomes unstable after mixing, with large aggregates precipitated. 

Enantioselectivity in Aggregation/Precipitation Induced Fluorescence Emission. 203... 

In the case of finer suspensions such as wheat starch or quartz powder, the particles of which have a diameter of 0.001 to 0.005 mm., the effect of electrolytes is more marked. The particles flock together to form larger aggregates, and these aggregates precipitate more rapidly than do the individual particles. The much investigated turbid solutions of clay exhibit this to a marked degree, as shown by the work of Schlosing f and Bodlander.f These solutions behave in a manner very similar to that of irreversible hydrosols such as colloidal metals, which are also very sensitive to the action of electrolytes. 

Lowering the dielectric constant also affects the electrostatic interactions in the structure The ionization of charges in contact with the solvent is weaker and the electrostatic interactions between neighboring ions at the protein surface are modified. Aggregation/ precipitation of the proteins follow. On the other hand, a salting-in effect results from the weakening of the water structure due to the strong interaction between alcohol and water molecules. 

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