Myoglobin roughness

In the 1960, it was noticed that substitutions in some amino acid sequences seemed to occur at a roughly constant rate over time (Zuckerkandl and Pauling, 1965). This is the well known molecular clock hypothesis. For a particular protein such as cytochrome c or myoglobin, it was noticed that there was a linear relationship between divergences of pairs of sequences, as measured by numbers of amino acid differences, and divergences of the species, as measured by dates from the fossil record. There is still considerable debate as to how accurate the molecular clock may be and as to how it might vary systematically depending on the species, type of protein, and kinds of substitutions that are counted. 

Proteins are folded in many ways. We have already considered several simple patterns the antiparallel P cylinder (Fig. 2-16), the 2-helix coiled coil (Fig. 2-21) and the 3- and 4-helix bundles (Fig. 2-22). Another simple motif that has been found repeatedly is the helix-turn -helix or helix-loop-helix in which two helices at variable angles, one to another and with a turn or short loop between them, form a structural emit. DNA-binding repressors and transcription factors (see Fig. 2-21 and also Chapter 5) often contain this motif as do many Ca2+-binding proteins. Proteins containing 3-6 helical segments, often fold into a roughly polyhedral shape.258 259 An example is myoglobin (Fig. 2-19B). 

Figure 24.11 A shows a schematic structure of myoglobin, a protein that contains one heme group. Myoglobin is a globular protein, one that folds into a compact, roughly spherical shape. Globular proteins are generally soluble in water and are mobile within cells. Myoglobin is found in the cells of skeletal muscle.

Figure 20 Influence of number of bilayers deposited on the amount of electroactive myoglobin in films constructed on rough PG with various polyanions. PSS and ds-CT DNA were adsorbed from 0.5 M NaCl solutions...

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