Maximum stability

GB is unstable in the presence of water. Maximum stability in aqueous solutions occurs from pH 4.0—6.5 with the hydrolysis rate increasing as the pH increases. The half-life in distilled water at 25°C is ca 36 h, but hydrolysis is accelerated in the presence of acids or bases. Because bases are far more effective in this respect than acids, caustic solutions are useful for decontamination. 

Replenishment should be done with caie. Massive additions can cause decomposition. Maximum stability of electroless baths is obtained when continuous replenishment is practiced. Colorimetric analy2ers are commonly used to control the addition of replenisher solutions in a set ratio based on the nickel or copper content of the bath. A number of machines are available that continuously analy2e plating baths and make additions based on each separately analy2ed component. 

Paper with enhanced wet-strength may be obtained by incorporating melamine resin acid colloid into the pulp. Melamine resin acid colloid is obtained by dissolving a lightly condensed melamine resin or trihydroxymethylmelamine, which are both normally basic in nature, in dilute hydrochloric acid. Further condensation occurs in solution and eventually a colloidal solution is formed in which the particles have a positive charge. Careful control over the constitution of the colloidal solution must be exercised in order to obtain products of maximum stability. 

How close are the two nuclei in the H2 molecule If they are too close, they will repel each other because both are positively charged, yet if they re too far apart, they won t be able to share the bonding electrons. Thus, there is an optimum distance between nuclei that leads to maximum stability (Figure 1.9). Called the bond length, this distance is 74 pm in the H2 molecule. Every covalent bond has both a characteristic bond strength and bond length. 

What about tertiary structure Why does any protein adopt the shape it does The forces that determine the tertiary structure of a protein are the same forces that act on ail molecules, regardless of size, to provide maximum stability. Particularly important are the hydrophilic (water-loving Section 2.13) interactions of the polar side chains on acidic or basic amino acids. Those acidic or basic amino acids with charged side chains tend to congregate on the exterior of the protein, where they can be solvated by water. Those amino acids with neutral, nonpolar side chains tend to congregate on the hydrocarbon-like interior of a protein molecule, away from the aqueous medium. 

In the cyclization of the corresponding cis-epoxides, with the aim of obtaining the corresponding cis-2,3-disubstituted tetrahydropyrans, a similar trend was observed. For these systems, however, the 6-endo pathway was less favored, which was ascribed to difficulties in attaining a TS conformation that would allow for maximum stabilization of the developing p-orbital with the adjacent 7t-system. Alternatively, palladium-catalyzed cyclization of the tetrabutylammonium alkoxide derived from 33b results in the corresponding ris-2,3-disubstituted tetrahydro-pyran in excellent yield and selectivity (90%, dr >99 1), while the ris-epoxide gives stereoisomer 37b (86%, dr 98 2) [112]. 

The Distribution of Spherons in Layers.—Several theoretical and empirical arguments indicate that the nature of spheron-spheron interactions is not such as to limit the ligancy of a spheron to a fixed value, but that, instead, maximum stability is achieved when each spheron ligates about itself the maximum number of neighbors aggregates of spherons, like aggregates of argonon (noble-gas) atoms or metal atoms, assume a closest-packed structure. 

However, consideration in terms of the ionic radius or the LFSE shows that both factors predict that the maximum stabilities will be associated with nickel(ii) complexes, as opposed to the observed maxima at copper(ii). Can we give a satisfactory explanation for this The data presented above involve Ki values and if we consider the case of 1,2-diaminoethane, these refer to the process in Eq. (8.13). 

Steric crowding of intermediates, preventing groups from attaining correct conformations for maximum stabilization of departing anions, may be responsible for the observation that, in the alkaline hydrolysis of sterically crowded phosphonium salts, the group lost need not be that which is most stable as the anion. 

Silyl migrations readily occur in silylated ylides to give the ylides of optimum stability. Thus, deprotonation of the salts (21) and (23) gave the ylides (22) and (24), respectively. Intermolecular silyl transfers, from one ylide (or the corresponding phosphonium salt) to another, also lead to maximum stabilization. Silyl transfer does not occur in the product (26) from methylenetrimethylphosphorane and the chlorodisilane (25), pre-... 

Most particles of the dispersion phase occur in a wide distribution of sizes consisting of aggregates of the primary particles. To ensure maximum stability, these aggregates must be reduced to an acceptable minimum size. When particles larger than the accepted minimum size are present in a dispersion, the physical properties of the dispersion are influenced by the size of the larger aggregates. 

Effects of cyclic tension. Cyclic compounds including six bonds present maximum stability. This rapidly decreases when the number of bonds increases... 

The formulation for soft gelatin capsules involves liquid rather than powder technology. Materials are generally formulated to produce the smallest possible capsule consistent with maximum stability, therapeutic effectiveness, and manufacture efficiency [3],... 

In addition to the additives used in a formulation to help stabilize the protein to freezing, the residual moisture content of the lyophilized powder needs to be considered. Not only is moisture capable of affecting the physicochemical stability of the protein itself, equally important is the ability of moisture to affect the Tg of the formulation. Water acts as a plasticizer and depresses the Tg of amorphous solids [124,137,138]. During primary drying, as water is gradually removed from the product, the Tg increases accordingly. The duration and temperature of the secondary drying step of the lyophilization process determines how much moisture remains bound to the powder. Usually lower residual moisture in the finished biopharmaceutical product leads to enhanced stability. Typically, moisture content in lyophilized formulations should not exceed 2% [139]. The optimal moisture level for maximum stability of a particular product must be demonstrated on a case-by-case basis. 

Cyclics are removed via vacuum stripping Catalyst must be neutralized for maximum stability Mn is controlled at equilibrium via initial [D l/lDSX] ratio Other endgroups possible with appropriate DSX and catalyst... 

Most of the hydrogen peroxide solution supplied for textile bleaching is acidic (pH 4.5-5.0) because it shows maximum stability under these conditions. Additives are present to increase its stability further at this pH. 

The localized product-NBO view also makes clear the importance of the non-planarity of the TS in achieving favorable hyperconjugative stabilizations, because interactions of 7t-planar geometry. Indeed, one can see that favorable vicinal n-a or a-7r overlap should primarily involve one end (hybrid) of each NBO, oriented, if possible, in the anti conformation for maximum stabilization. This viewpoint allows one to recognize the importance of angular and orientational factors that would not be evident in a purely topological framework. 

Erythromycin is unstable in acidic or alkaline solutions and shows its maximum stability between pH 6.0 and 9.525. Its aqueous, alcoholic solution buffered at pH 7.0 - 8.0 is stable for about one week under refrigeration. 

Stability. Being a fairly high-silicious zeolite, mordenite generally has high thermal stability. It was reported (77) that progressive acid dealumination results in an increase in thermal stability, followed by a decrease. Maximum stability was reached for a Si09/Al90 ratio of about 19. 1 1 J... 

The ether-catalyst complex (II) splits into a complex anion (III) and a carbonium ion (IV), which rearranges to the configuration of maximum stability (V). This carbonium ion (V) could itself initiate polymerisation, but it is more likely that it attacks the double bond of the closely associated anion (III), giving the double ion (VI) in equilibrium with the aldehyde (VII). Rearrangements of the type (I)-(VII) have been observed for vinyl ethers [7], and a closely parallel isomerisation is that of isobutyl phenyl ether into para-tertiary butyl phenol under the influence of A1C13 [8]. It is unlikely that the steps from (II) to (VI) take place in a well defined succession. The process probably proceeds by a single intramolecular transformation. 

Consider what happens to pepsinogen near its optimal Tm of 339.4°K (66.2°C), when 20% ethanol is added to the solution (Figure 13.9). The temperature of maximum stability occurs near 300°K (26.9°C). When 20% ethanol is added, the Tm is lowered to 329.0°K (55.9°C) as expected, suggesting some destabilization of the protein between the two solution conditions. However, the temperature of maximum stability occurs at a lower temperature near 273°K... 

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