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Published on Nov 15, 2008
Human hemoglobin, in your blood cells, displays precise changes in internal cooperativity in response to exactly how the first two oxygens bind to it.
This video depicts, in dance, the study: "Resolving Pathways of Functional Coupling in Human Hemoglobin Using Quantitative Low Temperature Isoelectric Focusing of Asymmetric Mutant Hybrids"
Hemoglobin is a 4-subunit protein (a tetramer) that binds and transports oxygen. Individual alpha-subunits and beta-subunits come together to form almost inseparable dimers (boy-girl pairs with matching eye-goggle and gloves in the dance). How dimer-1 interacts with dimer-2 in the whole protein, however, depends on the exact combination of bound oxygens (white balls). If one dimer gets 2 oxygens to itself, cooperativity is reduced and it does not interact well with the other dimer. If both dimers get at least 1 oxygen, they cooperate with each other, and usually bind 2 more oxygen molecules (for a total of 4). In normal hemoglobin, the two dimers are identical. Hemoglobin tetramers with two differing types of dimers are called "asymmetric mutant hybrids" (hence the different colored goggles and gloves on each "dance-mer"). "Low temperature isoelectric focusing" is a method that freezes (literally) and takes a snapshot of the dimer-dimer interactions at different times.