Macromolecules scaling representation

One of the examples of the scaling representation of macromolecules is the reptation model [48], according to which the tube diameter O, in which the macromolecule is confined (equal to the distance between entanglements nodes), can be estimated according to the relationship [49] ... 

Fig. 11. Unfolding of vitronectin exposes epitopes for osteoblast adhesion on nanophase ceramics. Schematic representation (not in scale) of a possible mechanism for enhanced osteoblast adhesion on (a) nanophase, compared to (b) conventional, ceramics, which involves unfolding of the vitronectin macromolecule to expose select cell-adhesive epitopes (such as arginine-glycine-aspartic acid) for osteoblast adhesion. Increased exposure of cell-adhesive epitopes of vitronectin for enhanced osteoblast adhesion on nanophase ceramics may be due to nanometer surface topography and/or increased wettability due to the greater number of grain boundaries at the surface.

In this chapter we shall combine some of the ideas described in Chapters 3 and 4 the applications of topological concepts and methods for the study of various representations of molecular shapes. Among the shape representations molecular contour surfaces have a prominent role, but we shall also consider alternatives, primarily for the purposes of characterizing the large scale shape features of biological macromolecules. 

Even in the atomic-scale graphical representation of macromolecules it is easy to recognize helical segments. In our display we represent any helical portion of a molecule by a single rod. Properties of the rod would include the number of turns and the number and nature of atoms or residues involved in the local helical structure. Other types of secondary structure lend themselves to representation by generalized cylinders, but have not been incorporated into our code, which is in an early stage of development. 

There are considerable advantages, of simplicity and power, to the large-scale and approximate representation of macromolecules by "generalized cylinders". Gross features of the structure are made easier to grasp visually. But more significant, major alterations to the... 

Most large-scale shape features of macromolecules such as proteins require representations which ignore some of the details. Topical among such models are the motifs of an a-helix or a -sheet of a protein. ... 

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