Mechanism of protection

Several theories have appeared in the Hterature regarding the mechanism of protection by -PDA antiozonants. The scavenger theory states that the antiozonant diffuses to the surface and preferentially reacts with ozone, with the result that the mbber is not attacked until the antiozonant is exhausted (25,28,29). The protective film theory is similar, except that the ozone—antiozonant reaction products form a film on the surface that prevents attack (28). The relinking theory states that the antiozonant prevents scission of the ozonized mbber or recombines severed double bonds (14). A fourth theory states that the antiozonant reacts with the ozonized mbber or carbonyl oxide (3) in Pig. 1) to give a low molecular weight, inert self-healing film on the surface (3). 

Primers for protective coatings may be divided into three broad classes based on the mechanism of substrate protection barrier primers that function by preventing the ingress of moisture and electrolytes, primers that protect the substrate galvanically in the presence of electrolytes, and primers that contain electrochemical inhibitors to passivate the substrate. Each of these approaches requires a distinct primer film structure due to the different mechanisms of protection. 

The Durability of Steel in Concrete. Part I Mechanism of Protection and Corrosion, Digest 263, Building Research Establishment... 

Krause, G.H. Behrend, U. (1986). A pH-dependent chlorophyll fluorescence quenching indicating a mechanism of protection against photoinhibition of chloroplasts. FEBS Letters, 200, 298-302. 

The most effective antiozonants are the substituted PPDs. Their mechanism of protection against ozone is based on the scavenger-protective film mechanism [68-70]. The reaction of ozone with the antiozonant is much faster than the reaction with the C=C bond of the rubber on the rubber surface [56]. The rubber is protected from the ozone attack tUl the surface antiozonant is depleted. As the antiozonant is continuously consumed through its reaction with ozone at the mbber surface, diffusion of the antiozonant from the inner parts to the surface replenishes the surface concentration to provide the continuous protection against ozone. A thin flexible film developed from the antiozonant/ozone reaction products on the mbber surface also offers protection. 

Metal toxicity is also affected by physiochemical factors, such as pH and the concentration of divalent cations. Adding divalent cations, such as zinc, has been reported to mitigate toxicity produced by other metals. For example, the addition of 60 pM zinc reduced toxicity in Pseudomonas putida caused by 3 mM cadmium.148 Zinc had no effect on cells grown in the absence of cadmium. Little is understood surrounding the mechanism of protection however, cadmium uptake was observed to be dependent on zinc concentration.149 Zinc was found to be a competitive inhibitor of cadmium uptake. 

Mora A, Fuentes JM, Soler G, Centeno F. Different mechanisms of protection against apoptosis by valproate and Li+. Eur J Biochem 1999 266 886-891. 

Pikal [3.3] suggests also, that the mechanism of protection of proteins is different during freezing and drying. For the selection of CPAs, Pikal recommends to observe three points, which can be summarized ... 

Chlorinated phenyl isocyanates have also been reacted with wood and found to reduce attack by G. trabeum. The mechanism of protection was attributed primarily to substrate blocking, rather than toxicity of the reacted chemical (Rowell, 1984b). Chen etal. (1990)... 

Murhammer and Goochee [93, 94] have confirmed the beneficial effect of Pluronic F-68 addition to insect cell cultures and its protective effect upon bubble damage. The use of PF-68 is today ubiquitous in bioprocess development involving insect cell culture technology, although it may conceivably interfere with VLP formation in some instances. For a more detailed study of the effect of bubble in cell damage mechanisms and the mechanism of protection of PF-68 see the review by Chalmers and the references cited therein [95]. 

The mechanisms of protection by these compounds have been evaluated for irradiated polymers. Many so-called protectors contain sulfhy-dryl groups and appear to operate by replacing or capturing the hydrogen atom lost by irradiating the macromolecule. It appears most reasonable to assume mat the same mechanism often occurs in biological systems. 

Mechanism of Protection and Working Model of A3 Receptor Signaling... 

The A3 receptor agonist is a prime candidate for pharmacological intervention in the first few hours post-injury based on several working hypotheses regarding its mechanism of protection. First, the data in Fig. 13.4 in the previous section suggest that the activation of A3 receptors is capable of inducing potent anti-ischemic... 

A recent study has utilized an in vivo murine tumor model expressing human HER-2 for evaluating potential HER-2 vaccines consisting of either full-length or variable subunits of HER-2 delivered in either protein or plasmid DNA form (discussed later) (Foy et al., 2001). The mechanism of protection elicited by plasmid DNA vaccination appears to be exclusively CD4-dependent and not CD8- or antibody-dependent, whereas the protection observed with intracellular domain protein vaccination requires both CD4 and CD8 T cells. However, the exact mechanism(s) responsible for immunity to DNA has not been elucidated. 

Sudha Sawargara M, Adinarayana M (2003) Kinetics and mechanism of protection of thymine from sulphate radical anion under anoxic conditions. Proc Indian Acad Sci (Chem Sci) 115 123-128 Sugiyama H.Tsutsumi Y, Fujimoto K, Saito I (1993) Photoinduced deoxyribose C2 oxidation in DNA. Alkali-dependent cleavage of erythrose-containing sites via a retroaldol reaction. J Am Chem Soc 115 4443-4448... 

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