**1. Introduction to chemical biology and history**

Chemical biology flourished as a discipline of science which makes use of several aspects of chemistry to understand biology [1]. Chemical biology includes a wide range of fundamental problems related to the understanding of complex biological processes by the development of synthetic frameworks to generate selective and active lead compounds [2].

The roots of history of chemical biology lie in the emergence of chemistry and biology as separate disciplines. Chemical biology flourished as a separate discipline of science because of newer challenges and questions for the study of chemical methods employed on living bodies. This branch of study is concerned with advanced molecular concepts of biology harnessed to the use of chemical entities. In spite of the newness of this concept, the history of chemical biology extends up to two centuries, considering the foundations of chemistry and biology. Here only a brief account of history of chemical biology is discussed. Joseph Priestley

discovered nitrous oxide gas in 1772 and incubated the mice with "airs" (the gases discovered till that time). He used 10 gases including nitrous oxide on experimental mice. His experiments on mice faced a strong mass discontent from Americans who showed a sympathetic behavior towards animal rights. Thus, the first chemical biologist fell a prey to angry mob due to his experiment on mice [3].

Afterwards, another chemist, Humphry Davy, worked (1778–1829) on the newly isolated and unfamiliar gases at that time. Frightened by the previous experiment, Humphry completely omitted the use of mice and decided to carry out the research on himself. It was not a matter of surprise that one of the gases, carbon monoxide, proved fatal for the scientist, but the pleasant effect of nitrous oxide made him name this gas, "the laughing gas." He also investigated the use of this gas in medical surgeries. Samuel Taylor also documented this gas as a pleasure-making gas [4], but the practical use of this gas in medicine was described in 1844 by an American

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*Chemical Biology Toolsets for Drug Discovery and Target Identification*

dentist, Horace Wells [5]. In 1998, three scientists, namely, Ferid Murad, Robert Furchgott, and Louis Ignarro, won Nobel Prize for the demonstration of significant

to lay the basis of chemical biology by carrying out his research on vitalism. He prepared urea from inorganic chemicals and rejected the famous "vital force theory" in 1828 [7]. The next important event in the history of chemical biology "cellular imaging" was revolutionized by utilizing the chemical approaches during the nineteenth century. John Hershel invented the cyanotype process which was brought into practice by Anna Atkins to prepare delicate botanical specimens. This noble lady also published her book entitled as *Photographs of British Algae: Cyanotype Impressions* [8]. Ehrlich (1854–1915) is thought to be the pioneer of the earliest forms of chemotherapy and drug therapy. He carried out numerous experiments on aniline based dyes and proposed the idea of "magic bullets." He said that these magic bullets are capable of targeting specific pathogens. He discovered a chemical compound Salvarsan, a drug used against syphilis. This compound is also called as Ehrlich's 606th compound, it was named so because of the successful compound he discovered after 605 failed target compounds. The discovery of this compound paved a way for the discovery of new chemical entities or the new "magic bullets" [6, 9] (**Figure 1**). Chemical biology flourished as an eminent scientific discipline due to significant

contributions of Koehler (pioneer of various chemical screening approaches), Saghatelian (discovery and characterization of lipids and peptides), Wang (use of chemoproteomics in determination of electrophilically lipidated cellular proteins),

Chemical probes are the small molecules which bind to the specific targeted sites and initiate their cellular activities. These archetypal tools act as highly valued reagents for molecular- and genetic-level biological research. Chemical probes are helpful in the

Many tools have been involved in target validation since the 1980s. Target identification and validation are long procedures. They were mainly based on structureactivity relationship. The drug discovery system becomes the most important approach towards the targeted cells [11]. Traditional antisense and RNA interference (RNAi) technologies are the robust tools used in multidimensional phases to discover and validate the potential drug targets. This approach elaborates the potentially selective cleavage of a targeted messenger RNA. This targeting technique enables the

Induced protein degradation is an event-driven approach which depends on drug binding and eliminating the target protein after tagging it. This approach is gaining attention in recent times because of the selective degradation of the target proteins.

accurate investigation of biological pathways and their associated targets [10].

researchers to explore the protein-based expression on phenotypes [12].

and Patti and Northen (metabolomics analysis) [1].

**2. Chemical biology tools**

**2.2 Antisense and RNAi technologies**

**2.3 Protein degradation strategies**

*2.3.1 Induced protein degradation*

**2.1 Chemical probes**

Wöhler is a well-known scientist in the history of chemical biology. He attempted

*DOI: http://dx.doi.org/10.5772/intechopen.91732*

role of nitric acid in cell signaling [6].

**Figure 1.** *History of chemical biology with its eminent events.*

#### *Chemical Biology Toolsets for Drug Discovery and Target Identification DOI: http://dx.doi.org/10.5772/intechopen.91732*

dentist, Horace Wells [5]. In 1998, three scientists, namely, Ferid Murad, Robert Furchgott, and Louis Ignarro, won Nobel Prize for the demonstration of significant role of nitric acid in cell signaling [6].

Wöhler is a well-known scientist in the history of chemical biology. He attempted to lay the basis of chemical biology by carrying out his research on vitalism. He prepared urea from inorganic chemicals and rejected the famous "vital force theory" in 1828 [7]. The next important event in the history of chemical biology "cellular imaging" was revolutionized by utilizing the chemical approaches during the nineteenth century. John Hershel invented the cyanotype process which was brought into practice by Anna Atkins to prepare delicate botanical specimens. This noble lady also published her book entitled as *Photographs of British Algae: Cyanotype Impressions* [8].

Ehrlich (1854–1915) is thought to be the pioneer of the earliest forms of chemotherapy and drug therapy. He carried out numerous experiments on aniline based dyes and proposed the idea of "magic bullets." He said that these magic bullets are capable of targeting specific pathogens. He discovered a chemical compound Salvarsan, a drug used against syphilis. This compound is also called as Ehrlich's 606th compound, it was named so because of the successful compound he discovered after 605 failed target compounds. The discovery of this compound paved a way for the discovery of new chemical entities or the new "magic bullets" [6, 9] (**Figure 1**).

Chemical biology flourished as an eminent scientific discipline due to significant contributions of Koehler (pioneer of various chemical screening approaches), Saghatelian (discovery and characterization of lipids and peptides), Wang (use of chemoproteomics in determination of electrophilically lipidated cellular proteins), and Patti and Northen (metabolomics analysis) [1].
