Interlocking Rings and Knots at the Molecular Level

one piece, but in two halves; the line between the two halves was unsuspected and undetected for many decades .) These genes usually remain “on”during development to remind the cells what to do as the embryo grows. It is as if all the instructions on making the entire animal are written in an enormous book, and these special genes tell each group of cells which pages in the book to use. Research on vertebrate animals has shown that we are also partly built in modules and that the same designer genes are used. Flies and people have a great deal in common! References and Notes 1. Peter A. Lawrence. Tlw Making oJn 1;14.(Oxford, U.K.: Blackwell Science, 1992). 2. Seymour Benzer, ”Genetic Ilissection of Beliavior ,” ScienfijicAmm’can 229 (1973) pp. 24-37. 3. Lewis Wolpcrt, Tlip Triiiiiiph oJlhr L d r y o (Oxford , U.K.: Oxford Univ. Press, 1991). 4. Droso/Jhiki iiirlniiopler is tlie common fruitfly. Antonio Garcia-Rellido, Peter A. Lawrence and Cines hlorata, “Genetic Dissection of Behavior,” Scien/ijirAnwicnn 241 (1979) p. 102. INTERLOCKING RINGS AND KNOTS AT THE MOLECULAR LEVEL Jean-Pierre Sauvage, Universitk Louis Pasteur, Faculte de Chimie, 4, rue Blaise Pascal, 67070 Strasbourg-Cedex, France. E-mail: . The ruorlz reported in this Abstract ruas aruarded a 1996 LVMH Vinci o f Excellence Prize. The synthetic chemist is usually highly interested in the aesthetics of the molecule he or she wants to assemble. In fact, the search for aesthetically attractive molecules has been a goal since the very origin of chemistry. The aesthetic aspect of any object is usually connected to its shape in Euclidean geometry However,another interesting facet of beauty rests in the topologicalproperties of the object. The latter can be deformed as much as desired , provided edges and lines that constitute the object are not cleaved. Among the most topologically fascinating objects, interlncerl d e s i p and lrnots (such as the archetypical treJil Itnot) occupy a special position. Representing continuity and eternity in early religious symbolism, they illuminate the art of the most ancient civilizations. Developed by Egyptians, Persians and Greeks, A cU B u D Fig. 3.Jean-Pierre Sauvage.Template synthesisof catenanes (one metal, represented by a black circle) or a trefoil knot (two metal centers). Each thread is a molecular fragment, incorporating various chemical functions not represented here. For instance, in the bottom line, the two threads of A can react with two metals (copper atoms) to generate a doublestranded helical molecule (B). In this process, the two metals gather and interlace the two strings of A in such a way that a double helix is formed. From the precursor B, the trefoil knot C is obtained by specific chemical reactions, their overall effect being that of producing a knotted ring (“cyclization”process). The two metals utilized to construct and maintain the molecular edifice B in the appropriate geometry during this procedure are still present in the closed molecule C. They can be removed by appropriate chemical reagents to afford the trefoil knot D. It is interesting to note that the cyclic strand of C is identical to D. Fig. 4. Jean-Pierre Sauvage. Shownhere is the molecule represented as C in Fig. 3. The chemical formula is indicated on the left. The real shape of the molecule was determined by X-ray diffraction and is represented on the right: one can recognize the two copper atoms (white circles in the median part of the drawing) and the general analogy between both geometries (chemical formula and real shape). Interestingly, the length of the trefoil knot represented here is one-thousandth of a micron . This givesan idea of the scale at which molecular chemists construct their edifices. In a normal preparation of the knot, one obtains about 70 milligramsof the molecule (equivalent to the size of a peppercorn). This is not much, but such a sample contains 20 billion billion individual knots. Again, this shows how small the molecular world is. 276 LVMH Alistracts among others, this virtually universal art reached its zenith in the Celtic culture. The magnificent illuminations consisting of extremely complex interlaced designs and knots in the Book o f Kelk give...