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(New page: == Your Heading Here (maybe something like 'Structure') == Elephants can hold their breath for 2 minutes, but whales can ghold their breath for 60 minuntes - and they do, migrating underwa...)
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Revision as of 09:28, 31 December 2013
Your Heading Here (maybe something like 'Structure')
Elephants can hold their breath for 2 minutes, but whales can ghold their breath for 60 minuntes - and they do, migrating underwater around the world. To get a clue as to why whales can hold their breath for so long, several researchers attained tissue samples (mainly from museum collections) from hundreds of aquatic and terrestrial mammialian species. They measured the concentration of myoglobin - the protein that stores oxygen in muscle tissue for times of muscle activity - in the tissue, and they cloned and sequenced the myoglobin gene, and used to sequence - as well as eletrophoresis of the protein, when possible - to calculate the net charge of each species myoglobin protein. Amazingly they found that independently, aquatic mammals across the mammalian phylogeny had acquired their ability to hold their breath through increasing the concentration of myoglobin, via increasing the net charge of myoglobin. typically, terrestrial mammal's myoglobin has a solubility of 20 mg/g tissue and that is the level of myoglobin found in most terrestrial mammals tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility contrains may be traced back to an incraese in t net charge of myoglobin - from around +2 in terrestrial animals to +around +4 in aquatic animlals.
However, a 3-fold increase in concentration of myoglobin out to result in a similar fold incraese in max time of breath holding, and the researchers determine that body mass has also bea critical contribution to enabling breath holding, with the overall equation for the contribution of body mass and myoglobin net charge as follows: EQUATION
Molecular Tour
the ability of incraesing net charge to enable higher solubility is a known phenomena, and this study is consistent with previous reports. The aquatic animals have increased their net charge in a variety of ways - different combination amino acids switches. We present one such manifestation of this overall trend, by comparing the elephant and whale myoglobin structures.
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