A block includes a hole provided on one side of the block, two fifths of the length of the block from one end, and a pin provided on the opposite side of the block two fifths of the length of the block from the other end. The hole is arranged to be connected to the pin of a like underlying or overlying block, so that a plurality of said blocks can be connected to form a double helix. Each end of the block includes a knob for connecting a plurality of blocks to a flexible member which follows a double helix shape to produce a model for DNA.

A molecule model construction kit includes six types of members, with each type representing the sugar, phosphate, thymine, adenine, guanine, and cytosine submolecules of the DNA molecule. The members are provided with coupling devices in the form of interlocking notches which represent the bonds between the sugar and phosphate submolecules, between the bases and the sugar submolecules, and between the bases. The coupling notches are asymmetrical and each notch corresponding to one-half of a bond is engageable with only one other notch corresponding to the other half of the same bond and in only one orientation with respect thereto. Therefore, the notches are formed so that the model can have only the structural configuration of a DNA molecule and each notch coupling performs functions analagous to the corresponding bonds in the DNA molecule, but not to functions of noncorresponding bonds. Furthermore, the notches have an orientation which results in a helical twist in the sugar-phosphate chains, with the proper ratio between adjacent chains, between adjacent loops of the same chain, and the diameter of the helix.

A molecular model of a relatively large molecule or a portion thereof is made up of a series of solid parallel and equidistant cross sections of rigid transparent plastic sheets representing space occupied by the atoms in the crystalline state. The adjacent cross sections are generated from x-ray crystal spectroscopic data providing crystal coordinates of the large molecules in computer readable form. Computer tapes of such data are used to print out numbered cross sections of the molecule showing coordinate plots of atoms intersecting such cross sections along a preselected coordinate axis. These cross sections are duplicated manually in clear rigid plastic sheets and assembled in order using appropriate spacer blocks to maintain accurate spacing of the adjacent cross section.

A magnetic toy or puzzle comprising a plurality of essentially two-dimensional pieces that may be assembled to form a hollow three-dimensional object. Each piece has at least three edges, and a magnet is mounted along each edge of each piece to allow the edges of the pieces to be joined together. The magnets are preferably keyed to allow: (a) only certain edges to attach to each other; or (b) the edges of the pieces to fit together in only one orientation. The magnets allow the edges to be joined in certain configurations to obtain the three-dimensional object. A holder for the puzzle pieces is provided that adds additional puzzle possibilities.

An NMR teaching method and apparatus incorporating pieces representative of chemical fragments. Each piece has the number of sides corresponding to the number of bonds present around the central atom. Bonds to hydrogen are curved while bonding sides are flat. The presence of concavities and convex tabs on the bonding sides indicates bonding of the respective piece to a mating piece that causes splitting of the NMR peak. The shape of concavities on each piece is indicative of the chemical fragment of the respective piece while the shape of the convex tab of the respective piece is indicative of the chemical fragment of the mating piece. First and second bonding indicators can be used to replace the convex tabs. When presented with a spectrum, a student user can select the necessary pieces using data from the spectrum. Once selected, the student user can then assemble the pieces to determine the identity of the unknown molecule in the NMR spectrum.