Antifreeze elimination

Destruction of the galactosyl residues by oxidation with periodate, acetylation of the free hydroxyl groups of the oligosaccharides, or their removal by P elimination all lead to loss of antifreeze activity. 

Polyhydric alcohols such as ethylene glycol (CH2OHCH2OH) are used as heat exchangers, in antifreeze formulations, and as industrial solvents. Young children and animals are sometimes attracted by the sweet taste of ethylene glycol and, rarely, it is ingested intentionally as an ethanol substitute or in attempted suicide. While ethylene glycol itself is relatively harmless and eliminated by the kidney, it is metabolized to toxic aldehydes and oxalate. 

In the winter months, significant benefits are derived from the use of concretes that contain cold-weather accelerating (CWA) admixtures with antifreeze properties. The economic benefits are derived from their ability to eliminate heating costs, afford the use of less costly mixes and enable the extension of the construction... 

Table II. Effect of Hydroxide Ion Concentration and Calcium Ion on Initial Rate of 3 Elimination of Phosvitin and Antifreeze Glycoprotein-8 (AFGP-8)...

Fig. 9. Time dependence of loss of threonine from antifreeze glycoprotein /8-eliminated in 0.5 N NaOH at several temperatures. Threonine loss was calculated on the basis of 4 residues per mole of AFGP-8. From Lee et al. (1977), reproduced with permission.

Effect of Hydroxide Ion Concentration on Initial Rate of R-Elimination of Antifreeze Glycoproteina,b... 

Sulfite Addition to p-Eliminated Antifreeze Glycoprotein at Different pH valuesa,b... 

Fig. 26. Inactivation of antifreeze and antilectin activities of antifreeze glycoprotein by /3-elimination of carbohydrate. Antilectin activity was determined by inhibition of Osage-orange lectin. Antifreeze activities were determined by measurements of freezing temperatures. /3-Elimination was done with glycoprotein concentrations of 0.1 mg/ml in 0.1 N NaOH at 20°C. Extent of/3-elimination was determined according to data of Table VIII. From Ahmed et al. (1973), reproduced with permission.

Elimination (Figs. 9 and 26) of the disaccharide destroyed both the antifreeze and antilectin activities (Ahmed et al., 1973). When 80% of the carbohydrate was /3-eliminated, approximately 10 and 20% of the antifreeze and antilectin activities, respectively, remained. 

If the enhanced kinetic barrier, Ag, results in the observed antifreeze function, then according to Eq. (44), the continued growth of the nucleus is a rate phenomenon. In experiments conducted with seed crystals of ice nuclei held at — 0.2°C, there does not seem to be a time-dependent growth of the seed nucleus, even over extended periods (Feeney and Hofmann, 1973 Ahmed et al., 1975). The fact that no rate effects have been observed, however, is insufficient reason to eliminate a kinetic mechanism. 

Air-cooled heat exchangers eliminate the need for water treatment and the need for disposal or recycling of solutions of antifreeze.82 The Volkswagen beetle uses an aircooled engine. Texaco is marketing an Extended Life Anti-Freeze/Coolant for cars and light trucks that lasts for 100,000 miles. Engine coolants can be recycled profitably.83... 

Presence of water in the system makes fuel cell systems susceptible to freezing if used outdoors in cold climate. In such case, the coolant loop is separated from the water system, which allows for antifreeze coolants (such as aqueous solutions of ethylene-glycol or propylene-glycol) to be used instead of deionized water. Nevertheless, water cannot be completely eliminated from the system after all, the PSA membrane contains up to 35% water. Operation, or actually, survival and start-up, of a fuel cell system in a cold environment is an issue that must be addressed by the... 

Automotive fuel cells must survive and operate in extreme weather conditions (-40 to -f40°C). This requirement has a tremendous effect on system design. Survival and start-up in extremely cold climate requires specific engineering solutions, such as use of antifreeze coolant and water management. Water cannot be completely eliminated from the system, because water is essential for the membrane ionic conductivity. 

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