Biochemistry - Chemical Reactions in Living Cells, Volume 3 - D. Metzler 1980

Construction of Molecular Models
Cardboard Models

Many biological "macromolecules" such as Proteins and Nucleic Acids consist of such a vast number of atoms that assembling their models from individual spheres is both time-consuming and expensive. In such cases, cardboard (metal, or plastic) mock-ups are used instead. For instance, to represent a planar peptide unit, one can construct a model (Fig. P-1) based on the dimensions given in Fig. 2-3 (Vol. 1, p. 88). It is quite difficult to calculate the exact angle at which bends should be made to reproduce the φ and ψ angles (see Fig. 2-4 and Table 2-3). (It is much easier to solve this problem directly through geometric construction using pieces of cardboard.) In this way, very elegant Helical structures can be created (some Examples are provided by Karlson [1]). If necessary, Styrofoam side chains can be glued to the α-carbon atoms. Alternatively, the helical model can be mounted On the surface of a cardboard cylinder and decorated with Styrofoam side chains.

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FIG. P-1. Template for making cardboard polypeptide models. Scale 2 cm : 0.1 nm.

To construct DNA and RNA helices, flat Base Pairs made of cardboard (or preferably a denser material) are strung onto a wire representing the axis, using pieces of rubber or polyethylene tubing as spacers. Paper mock-ups or Ball-and-stick models can be used to represent the sugar-phosphate backbone. (For greater clarity, the sugar-phosphate backbone can be made from two strips of heavy paper of different colors.) The precise geometry of the base pairs is detailed by Arnott and Hukins [2].

1. Karlson Р., Introduction to Modern Biochemistry, 3rd ed., pp. 43–45, Academic Press, 1967. (Note: a different type of model is presented in the 4th edition.)

2. Arnott S., Hukins D. W. L., JMB, 81, 93–105 (1975).