Viewing Stereo Drawings A. R. Srinlvasan and Wilma K. Olson Rutgers University. New Brunswick, NJ 08903
The illustration of molecular structures by means of stereo pairs (to project three-dimensional views of two-dimensional representations) has been in common practice for many years in periodicals, slide presentations, and books ( I , 2). A stereo viewer is indispensable to visualize these pictures correctly. However, an increasing number of readers have the skill of unaided cross-eyed stereopsis (3) (the abilitv to form a mental three-dimensional model from the twodimensional stereo pictures by crossing the images formed bv the rieht and left eves). This method of viewine stereograms b; means of direct stereopsis brings in an inherent error. Such stereo pairs in the literature are in ~ e n e r adel signed to provide the correct three-dimensional appearance when viewed with a special device, and a mirror image of the
Figure 1. Stereo Mptych drawing of a EDNA double helix. A right-handed B DNA double hellx is seen if the eyes are focused oo the pair of pictures to the right or if a Stereo device is focused on lhe pair to the left.
true object is perceived with unaided eyes. Because of this fact, understanding the molecular structures when viewed without an external appliance becomes very difficult and confusing in a number of instances (4). One avoids the problem, however, if one uses stereo triptych representations in place of conventional stereo diagrams. In fact, these representations have begun to appear in the literature in recent years ( 6 6 ) . Both exact and inverted three-dimensional images are simultaneously provided by a triptych (and not distal and proximal stereo views as detailed by Masut and Kusbick (5)).Themiddle figure of the triptych is the desired view of a structure, and the side figures are images rotated in a posi' about the axis perpendicular to the line of tive sense by 6 sight (the instructions given in Ref 6 are confusing). One such stereo triptych (Fig. 1) is shown for a B-DNA double helix (7). If the eyes are focused on the pair of pictures to the right, a right-handed structure (true model) is visualized; a left-handed helix (with the added inversion of all chiral centers) is obtained if the air on the left is examined. However, when the latter pair is viewed with a stereo device, the corrert right-handed DNA is seen. Stereo triptych drawings are clearly advantageous for the exact deciphering of threedimensional data through direct visual inspection or with the help of a stereo device. An overlapping sequence of stereos can be further used to visualize molecular rotations in three dimensions. As shown in Figure 2 (top) for the drug netropsin (B), multiply-rotated stereo views of the same structure can be eenerated bv nlac' about ihe axis perpendicing a series of images rutated by 6 ular to the lines of sieht of their predecessors. The structure on the far left is the starting image. Exact views of this molecule are perceived when looked at with cross-eyed stereopsis. The viewer has the advantage of looking at several three-dimensional views of the same molecule simultaneuusly. A picture of this type is also shown in Figure 2 (bottom) for device-aided visualization. In this case, the left-to-right orderine of the imaees nlaced on ton is reversed with the startiniiimage on thefa;right. pictures of this typemay be a useful means of disolavine . . -molecular structures in textbooks and for classroom use when no sophisticated graphics equipment is available.
Figure 2. Diagram projectingmunlplymtatedstereoviewsof nehopsin.mesequence of imagesonthe upper half of this pl?w er half is fa aided visuallation.
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Journal Of Chemical Education
is for vlrual inap%ctlonanndthelow-
Sponsorship of this work by the U.S. Public Health Service under grant GM-20861is gratefully acknowledged.
3. ~ a m o r iE , :; mad.^. D.;~ e e dC. , E., P L I ~ P ~1 m ~ ~. 1O 1 ,~ 4. young.^. C. science 1981.m.623. 5. Masvt. R A.; Kushick. J. N. J. Cornout. Chem. 1984.5.336.
Literature Cited
6. '"lnstrhionta~ufha&,"Protoin EM. 1981, 1 (no 4i. ' 7. S. Amoft (unpublished mordinate). 6. K w h , M.L.; Yoon, C.; GmdaeU. D.: Pjura, P.;Diek-n, USA 1985.82,1376.
1. Grah.m,D. M.J.Chem.Edu. lW6,63,6'lZ. 2. Strsuaa. M.J.: Dribble, G. J. Chem.Edu. 1987,64,850.
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