Filament region formation

Fig. 4. Schematic diagram of segment IB in intermediate filament chains showing generally conserved features. These include the highly conserved residues L74, L81, and E95 the conserved intra- and interchain ionic interactions represented by solid and dotted lines, respectively the trigger motif (residues 79-91) that acts as a particularly stable region that nucleates coiled-coil formation the site at residue 40 (indicated by an asterisk) of a six heptad insertion in lamin molecules. The entire segment displays a regular disposition of acidic and basic residues, each with a period of about 9.54 residues. These periods are approximately out of phase with one another.

Local non-uniformities present the danger of hot spot formation where the current forms filaments. Two adverse scenarios can develop (1) local thermal run away that engenders regions of high defect density which gradually grow in size, and (2) spectral hole burning in which certain spectral modes are locally depleted. For all of these reasons, uniform material properties have always been a mandatory virtue. 

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