Structure-stabilizing factors

Palau and co workers proposed a sdieme with elements of purely statistical methods (conformational preference parameters) and structure-stabilizing factors ( weighting factors ) The wei ting factors modify the conformational preference parameters by taking into account e.g. hydrophobic interactions with )-structural regions or the occurrence of hydrophobic triplets in the helical positions 1-2-5 and 1-4-5. Additional parameters can be introduced into the prediction scheme. 

All these studies demonstrated that water stability of MOFs can be improved by incorporating specific factors (e.g., metal-ligand strength, thermodynamic and kinetic factors, etc.) which govern the structural stability of the framework. 

The search for regularities and criteria for the synthesis of new representatives of particular structure types has been carried out by many authors. Several factors have been recognized to be important in controlling the structural stability, and some of these were used as coordinates for the preparation of classification and prediction maps in which various compounds can be plotted and separated into different structure domains. 

Delocalization of charge in the conjugate base anion through resonance is a stabilizing factor and will be reflected by an increase in acidity. Drawing resonance structures allows us to rationalize that the negative charge is not permanently localized on a particular atom, but may be dispersed to other areas of the structure. We should appreciate that a better interpretation is that the electrons are contained in a molecular orbital that spans several atoms. 

Haltia, T. Freire, E. (1995) Forces and factors that contribute to the structural stability of membrane proteins. Biochim. 

However, its high ash content and its high quantity of inert materials put it in a category of coals where predictions of stability are difficult. A comparison of the FSI values (Table II) for the +1% inch material (point 5 in Figure 5) with the 1% x Vi inch coal (point 6) suggests that the stability factor of the first-mentioned coal should be lower. This comparison substantiates to some degree the predictions made concerning the +1% inch coal. It is possible that the pitted or mylonitized component, because of its open porous structure, is more susceptible to oxidation than is the more normally textured vitrinite, and this could explain the apparently deleterious effect that this material has on coke quality. 

In view of the importance of macroscopic structure, further studies of liquid crystal formation seem desirable. Certainly, the rates of liquid crystal nucleation and growth are of interest in some applications—in emulsions and foams, for example, where formation of liquid crystal by nonequilibrium processes is an important stabilizing factor—and in detergency, where liquid crystal formation is one means of dirt removal. As noted previously and as indicated by the work of Tiddy and Wheeler (45), for example, rates of formation and dissolution of liquid crystals can be very slow, with weeks or months required to achieve equilibrium. Work which would clarify when and why phase transformation is fast or slow would be of value. Another topic of possible interest is whether the presence of an interface which orients amphiphilic molecules can affect the rate of liquid crystal formation at, for example, the surfaces of drops in an emulsion. 

Stability of an enzyme is usually understood to mean temperature stability, although inhibitors, oxygen, an unsuitable pH value, or other factors such as mechanical stress or shear can decisively influence stability (Chapter 17). The thermal stability of a protein, often employed in protein biochemistry, is characterized by the melting temperature Tm, the temperature at which a protein in equilibrium between native (N) and unfolded (U) species, N U, is half unfolded (Chapter 17, Section 17.2). The melting temperature of a protein is influenced on one hand by its amino acid sequence and the number of disulfide bridges and salt pairs, and on the other hand by solvent, added salt type, and added salt concentration. Protein structural stability was found to correlate also with the Hofmeister series (Chapter 3, Section 3.4 Hofmeister, 1888 von Hippel, 1964 Kaushik, 1999) [Eq. (2.18)]. 

From a point of view of industrial protein production the number of sequential operations necessary to achieve the desired purity of a protein contributes significantly to the overall costs of the downstream process. This is on one hand due to the capital investment and amount of consumables needed for each step as well as to the individual time requirements of each operation, as labour costs are a very important factor in the calculation of process economics. Secondly the overall yield of the purification is reduced with each additional process step, originating from its inherent loss of product. Furthermore, fast primary recovery should separate the protein of interest from process conditions detrimental to its structural stability, e.g. proteases, glycosidases, or oxidizing conditions. As the performance of the purification process, expressed by its overall yield, operation time, and capital cost may contribute to up to 80% of the total production costs [2], it is evident, that a reduction of the number of sequential steps in a purification protocol may be the key to the economic success of a potential protein product [3],... 

To evaluate the factors affecting the structural stability of some crystalline materials that are potential hosts for radioactive wastes, the crystal structures of a series of 3+p5 xv5+o compounds, where A is lanthanum or a member of the rare-earth series, were determined. The end-member phosphates (APO4) have the monoclinic Monazite structure (P2 /n) for A La, Ce-Gd, and the tetragonal Zircon structure (l4]/amd) for A Tb - Lu. The corresponding vanadates have the Monazite structure only for LaVO, and the Zircon structure for A = Ce - Lu. When the end members are iso-structural, e.g., LaPO /LaVO, Monazite, YbPC /YbVOA,... 

Thus, the apparent stability of a cluster ion in any specific CMS may arise from a combination of one or more of the following factors, such as structural stability, electronic bonding pattern, and dynamics of unimolecular dissociation. 

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