Crab sticks

Fig. 7.4 The three-dimensional fold of three serine proteases, (a) Fiddler crab collagenase defined in complex with WT eco, (b) rat gran-zyme B in complex with [81-84 lEPD] eco, and (c) human factor Xa in complex with M84Reco. Each protease is shown in grey. The catalytic triad and amino acids contacting the ecotin molecule in the active site are shown in grey ball and stick representation. The ecotin mol-...

On the one hand, the fda considers one part per million (ppm) of methylmercury in fish to be the limit. Shark, swordfish, king mackerel, and tilefish can contain more than this. On the other hand, the Environmental Protection Association maintains that 0.25 ppm is the upper hmit. If we adhere to this guideline, then white tuna (at 31 ppm) and light tuna (at 16 ppm) pose a problem. The species that canneries use for their light tuna contains less mercury than the albacore they use for white tuna because the fish are smaller. Current advice is that an adult should eat no more than one or two cans of tima a week. A child should eat no more than one tuna sandwich a week, and before the age of five he or she should stick to flounder, haddock, sardines, crab, or shrimp. 

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