Extremophile: Difference between revisions
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== Extraordinary Proteins == | == Extraordinary Proteins == | ||
Life has managed to weather extreme environments - almost every hole we've poked a stick into contains thriving living communities. Proteins are a necessity for living, and therefore tuning protein structures to an extreme environment is of paramount value to an evolving organism. In this article we | Life has managed to weather extreme environments - almost every hole we've poked a stick into contains thriving living communities. Proteins are a necessity for living, and therefore tuning protein structures to an extreme environment is of paramount value to an evolving organism. In this article, we present the biophysical modifications present in extreme protein structures. | ||
== Positively charged myoglobin allows whales to hold their breath during long dives == | == Positively charged myoglobin allows whales to hold their breath during long dives == | ||
Elephants can hold their breath for 2 minutes, but whales can hold their breath for 60 minutes - 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 from hundreds of aquatic and terrestrial | Elephants can hold their breath for 2 minutes, but whales can hold their breath for 60 minutes - 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 from hundreds of aquatic and terrestrial mammalian species (mainly from museum collections)<ref name="whaleMyo"> DOI:10.1126/science.1234192</ref>. They measured the concentration of [[myoglobin]], the protein that stores oxygen in muscle tissue for times of muscle activity, and also sequenced each specie's myoglobin gene, and used this sequence - as well as eletrophoresis of the protein, when possible - to calculate the net charge of each myoglobin protein. Amazingly, they found that independently, aquatic mammals across the mammalian phylogeny had acquired their ability to hold their breath, by increasing the concentration of myoglobin, through increasing the net charge of myoglobin. In real values, typically, terrestrial mammal's myoglobin has a solubility of 20 mg/g tissue ([[http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/Product_Information_Sheet/2/m0630pis.pdf Sigma Aldrich]]) and that is the level of myoglobin found in most terrestrial mammal's tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility constraint may be traced back to an increase in the 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 ought to result in a similar fold increase in max time of breath holding, and the researchers determine that body mass also makes a critical contribution to an animal's ability to hold its breath, with the overall equation for the contribution of body mass and myoglobin net charge as follows: | However, a 3-fold increase in concentration of myoglobin ought to result in a similar fold increase in max time of breath holding, and the researchers determine that body mass also makes a critical contribution to an animal's ability to hold its breath, with the overall equation for the contribution of body mass and myoglobin net charge as follows: | ||
