Toxins stability

The Effects of Processing, Handling, and Storage on Toxin Stability... 

THE EFFECTS OF PROCESSING, HANDLING, AND STORAGE ON TOXIN STABILITY... 

Collectively, these studies offer important insight into the relative stability of the BoNTs within the gastrointestinal traet based upon their resistance to inactivation under various enzymatic conditions. In general, toxin stability directly correlates with the presence of the accessory HA and NTNH... 

There are samples or crude extracts containing the analyte of interest but whose concentration has not been accurately established. For marine biotoxins, such materials may be frozen homogenates of naturally contaminated seafood, crude or partially purified extracts of such seafood, or of harmful algae. Digestive glands of contaminated shellfish are a source of concentrated toxins and their metabolites. Such materials cannot be used to calibrate methods of analysis but can serve very useful functions in method validation and quality control, especially when they contain rare toxins not readily available elsewhere (i) Retention times and spectral properties can be established on a routine basis for LC-UV, LC-FL, or LC-MS methods (ii) Partially purified extracts can be used for fortification experiments during method validation and thus establish recovery and precision data (iii) If concentrations of toxins can be established by reference to CRMs, then the materials can be used as in-house or interlaboratory reference materials for quality control. Issues such as toxin stability and homogeneity then become more important. ... 

FIGURE 16 Ribbon representation of irregular structures (a) High potential iron-sulfur protein coordinated to a 4Fe-4S cluster, (b) RAG1 DMA binding protein which contains representative examples of Zn-tinger domains, (c) Defensin as example of a membrane toxin stabilized by disulfide bonds, and (d) Chinese bird spider neurotoxin which contains a cystine knot. 

Preservatives generally fall into four categories. There are ultravi-olet/UV light absorbers (to prevent light from creating harmful and bad-tasting toxins), color stabilizers, antioxidants, and antimicrobials. 

The known toxinology of the Na channel classifies compounds into three categories activators, stabilizers, and occluders. Although these terms describe the apparent major effect of the toxin, it should be realized that multiple effects are more often the rule than the exception. 

Figure 5. Multiple actions of toxin II from Ammonia sulcata (ATX II) on voltage-clamped Na currents (Ij ) from amphibian myelinated nerve. This stabilizer toxin works in a dose-dependent manner to inhibit channel inactivation see bottom panel) and, as a consequence, delay the time of peak current see top panel). The reduction of peak current amplitude does not result directly from these kinetic alterations and is not observed with all stabilizers (Reproduced with permission from Ref. 39. Copyright 1981 SPPIF).

Chemical techniques for the isolation, purification and elucidation of the structure of toxins have evolved to the extent that it is frequently a routine procedure to identify the chemical nature of a newly discovered toxin once it has been purified, although difficulties arise when the toxin is a very large polypeptide, protein, or a very complex organic molecule. However, it is sometimes found that a toxin becomes progressively more labile and stabilizing contaminants are removed by the purification processes. An example of this is Cyanea toxic material which becomes increasingly labile with each purification step 111). 

Lead (Pb) is used for many applications, for example in electronic goods such as cathode ray tube (CRT) televisions and as a stabilizer in PVC. Pb is one of the oldest known and most studied occupational and environmental toxins. Despite the many studies, there is still debate regarding the toxic effects caused by Pb [39]. 

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