WLN Wiswesser Line Notation

The Wiswesser Line Notation (WLN) was introduced in 1946, in order to organize and to systematically describe the cornucopia of compounds in a more concise manner. A line notation represents a chemical structure by an alphanumeric sequence, which significantly simplifies the processing by the computer [9-11], (n many cases the WLN uses the standard symbols for the chemical elements. Additionally, functional groups, ring systems, positions of ring substituents, and posi-... 

Fritts, Lois E., Margaret Mary Schwind, Using the Wiswesser Line Notation (WLN) for Online, Interactive Searching of Chemical Structures, J. Chem. Inf. Comput. Sci., 22, (1982), pp. 106-109. 

Until the late 1970s, the Wiswesser Line Notation (WLN) was the only widely recognized format in which to code chemical structures in a computer-readable linear format. It was invented by William J. Wiswesser (1952), and his work was recognized and honored with the Skolnik Award for outstanding contributions to and achievements in the theory and practice of chemical information science by the American Chemical Society in 1980. The WLN was quickly adopted by major chemical companies to store and retrieve machine-readable, 3D-chemical structure information in a 2D, linear array, and is still in use today. 

Another approach for representing 2D chemical structures is the linear notation. Linear notations are strings that represent the 2D structure as a more or less complex set of characters and symbols. Characters represent the atoms in a linear manner, whereas symbols are nsed to describe information about the connectivity [3]. The most commonly nsed notations are the Wiswesser line notation (WLN) and the simpUfled molecnlar inpnt line entry specihcation (SMILES) [2]. The WLN, invented by William J. Wiswesser in the 1949, was the hrst line notation capable of precisely describing complex molecnles [4]. It consists of a series of uppercase characters (A-Z), numerals (0-9), the ampersand ( ), the hyphen (-), the oblique stroke (/), and a blank space. 

The efforts in computer technology were based on non-graphic business applications, so it was most practical for the chemical information systems to be made to adapt to the standard business computer. Systems evolved that were based on linear representations of graphical formulas, such as Wiswesser Line Notation, WLN (see Figure 3), or standard chemical nomenclature. But the linear representations were one step further removed from the 2-D structure that the chemist so depended on, and involved learning what in essence was a foreign language. The chemists found themselves more and more alienated from their own literature, and information intermediaries found their place in the sun. 

Computers have been used for the storage and retrieval of scientific datasince the late 1960s. At first only punched cards and printers with the alphanumerical character set were available for a reasonable price. These facilities were insufficient for a good presentation of chemical structures. The Wiswesser line notation (WLN) was a workable substitute for structures, but it has never become a common language for the chemists. CROSSBOW and a few other programs became available but these batch-oriented programs are not user-friendly for bench chemists. They found them barriers instead of aids in communication. Therefore these systems were used mainly by intermediaries or information scientists. 

Fisons original biological and chemical records system was set up in 1973 on a remote ICL computer and was subject to the hardware and software limitations of the time. Results were recorded by biologists on datasheets and largely in free format. Some codes were added by information scientists before the data was sent for input. Chemical structures were stored as Wiswesser Line Notations (WLN). 

What appears to be the first SDG paper was concerned with visualizing the hits of a database search. The structures were entered in Wiswesser line notation (WLN) and manipulated in a closely descended connection table. Drawing sequence was essentially the same as the WLN order. To avert atom overlap, stretching was used in branched chains (same approach as shown later in Figure 62), and drawing directions from ring alpha substituents were redirected as necessary. 

Wiswesser line notation (WLN) An early method for encoding chemical structures in alphanumeric characters representing atoms and groups of atoms. The method was widely used prior to computerization of compound databases. 

SMILES notation (Simplified Molecular Input Line Entry System) used in the Pomona College MedChem project ( ) the Dyson notation (5) adopted as a standard by the International Union for Pure and Applied Chemistry (lUPAC) and Wiswesser Line Notation (WLN), which became the actual standard used in the chemical industry (6). The rules of WLN were standardized by the Chemical Notation Association (CNA), but the two major WLN data bases. Index Chemicus Registry System, ICRS, from the Institute for Scientific Information and the Commercially Available Organic Chemicals Index, CAOCI (7) used somewhat different conventions. 

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