Binding under a molecular "umbrella" as a cooperative statistical mechanical system: tropomyosin-actin-myosin as an example.

We Study models in which initial ligand molecules can bind on a linear array of sites only by lifting or moving an adjacent polymer molecule, over a range of a few binding sites, into a state of higher free energy. This inhibits the initial binding but subsequent ligand molecules can then bind more easily under the "umbrella" already lifted in the initial binding (a cooperative effect). Three subjects are considered: cooperative properties of a general model in which, besides the "umbrella" effect, the polymer is divided into m-site long segments, with interactions between the ends of these segments (section 3); application of this model to tropomyosin-troponin-myosin (section (a cooperative effect). Three subjects are considered: cooperative properties of a general model in which, besides the "umbrella" effect, the polymer is divided into m-site long segments, with interactions between the ends of these segments (section 3); application of this model to tropomyosin-troponin-myosin (section (a cooperative effect). Three subjects are considered: cooperative properties of a general model in which, besides the "umbrella" effect, the polymer is divided into m-site long segments, with interactions between the ends of these segments (section 3); application of this model to tropomyosin-troponin-myosin (section 2); and cooperative properties of simpler models in which the polymer is not divided into segments though the "umbrella" can have various ranges (section 4).