Thermal stability screening

The first aim of a thermal stability screening test (e.g., DSC/DTA) is to obtain data on the potential for exothermic decomposition and on the enthalpy of decomposition (AHd). These data, together with the initial theoretical hazard evaluation, are used in reviewing the energetic properties of the substance (Box 4) and the detonation and deflagration hazards of the substance (Boxes 7 and 8). The screening tests also provide data on the thermal stability of the substance or mixture, on the runaway potential, on the oxidation properties, and to a lesser extent, on the kinetics of the reaction (Box 10). 

Gustin, J. L., "Thermal Stability Screening and Reaction Calorimetry—Application to Runaway Hazard Assessment and Process Safety Management," /. Loss Prev. Proc. Ind., 6,275 (1993). 

Thermal stability Screen size (mm) of screws (single/dual)... 

Gustin, J.L. (1993) Thermal stability screening and reaction calorimetry. Application to runaway reaction hazard... 

Thermal stability screens measure the increase in fluorescence intensity of a hydrophobic fluorescent probe that binds to proteins as they unfold during thermal denaturation. Automation of this assay in plate format has allowed rapid screening of libraries for compounds that improve the thermal stability profile of the target protein and has been particularly successful in identifying hits against active site pockets [152,153], and has recently been demonstrated in screening for inhibitors of Bel interactions and human MDM2/p53 [142, 154],... 

Bis(xanthates) are a readily accessible class of bis(ligands), but surprisingly little research has been published about their coordination polymers with metals 3, 7). This could be due to the fact that thermal stability screening studies showed them to be inferior in this respect (i). A series of polymeric nickel bis(xanthates) have been prepared from reaction of bis(potassium xanthates) with nickel salts (7) (see Table X.3, p. 315). Only meager information about their properties has been published. 

The remarkable thermal stability of the di-ferf-butyl-substituted thiepin 6, due to steric screening, has been demonstrated by its synthesis in an analogous manner to the carbocation rearrangement which provides dibenzothiepins. Under acidic conditions, methanesulfonic acid was eliminated from Ihiopyran 5 to give the thiepin via cationic rearrangement.18... 

At an industrial scale, the esterification catalyst must fulfill several conditions that may not seem so important at lab-scale. This must be very active and selective as by-products are likely to render the process uneconomical, water-tolerant and stable at relatively high temperatures. In addition, it should be an inexpensive material that is readily available on an industrial scale. In a previous study we investigated metal oxides with strong Bronsted acid sites and high thermal stability. Based on the literature reviews and our previous experimental screening, we focus here on application of metal oxide catalysts based on Zr, Ti, and Sn. 

Explanation of Principal Application Codes 1 = screening 6 = reaction due to oxidation 2 = thermal stability 7 = runaway behavior (initial phase) 3 = sensitive thermal stability 8 = complete runaway behavior and 4 = very sensitive thermal stability simultaneous pressure measurements 5 = study autocatalysis, contaminations, 9 = time to maximum rate of reaction inhibitor depletion ... 

The equipment is quite adequate for screening purposes. In its simplest form (i.e., a glass tube in an oven), it is a relatively low cost technique that can be assembled with standard laboratory equipment. However, the simple test set-up provides no quantitative thermal data for scale-up purposes, but only T0 values. The more advanced instruments like the SEDEX and SIKAREX, which are also isoperibolic calorimetry equipment, acquire specific thermal stability data that can be used for scale-up. Furthermore, the small autoclave tests provide gas evolution data. 

OECD Guideline for Testing of Chemicals, "Screening Test for Thermal Stability and Stability in Air," No. 113, Organization for Economic Cooperation and Development, Paris, France (1981). 

Five of nine respondents to the CSB survey frequently use both screening and more sophisticated approaches, including adiabatic calorimetry, to determine the thermal stability or compatibility of process materials. Seven of nine respondents use screening alone for chemical reactivity testing. The most often used testing objectives are ... 

To determine thermal stability using screening tests. 

Neupogen), a four-helix bundle cytokine, is formulated at pH 4 but has been shown to maintain both thermal stability and tertiary structure at pH 2.60 In fact, the secondary structure of this molecule was shown to remain highly helical at pH 4 (Tm approximately 62°C) and 2 (Tm approximately 63°C) as compared to pH 7 (Tm approximately 55°C) where a less conformationally stable form was observed. In the same study, FTIR and CD data corroborated the tendency of the protein to unfold as measured by the loss of helical structure in the order pH 7 > pH 4 > pH 2. Moreover, after determining optimal pH conditions of thermostability, several studies have shown that excipient screening at such conditions can successfully predict the rank of formulation cocktails that offer the most favorable stability.14 23 31 56... 

The a-helical coiled coil-based screening system already provided a wide variety of information about the interactions of fluorinated amino acids within hydrophobic and hydrophilic protein environments. Investigations on the thermal stability as well as the replicase activity have both emphasized the orthogonal properties of fluorinated aliphatic amino acid side chains. The term orthogonal in this context has been chosen by us to demonstrate that they are in fact hydrophobic... 

DSC is a basic screening test and should be applied to all chemicals and mixtures unless the thermal stability has already been clearly established. 

Overall, the effects of polycations on the helix-coil transition of DNA are similar to those exhibited by the small cations both of them induce thermal stabilization of DNA duplex and decrease the cooperativity of the helix-coil transition In both cases the reasons for the stabilization effects are the screening of the negatively charged phosphate groups of the DNA, which reduces their electrostatic repulsion (Schildkraut, 1965). However, the effective concentration of a simple salt at which the same stabilization effect is achieved is ca. 103 times higher than the effective concentrations of a polycation. Consequently, polycations provide for a much more efficient screening of the DNA phosphate groups than the small cations. 

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