Chemical structure-biological activity

The term alkaloids can be considered as more pharmaceutical and medical than chemical, since alkaloids come from a variety of otherwise-unrelated organic compounds. Alkaloids can be classified in terms of their biological activity, chemical structure (nucleus containing nitrogen), or biosynthetic pathway (the way they are produced in the plant). 

Square planar. There are two compounds with the formula Pt(NH3)2Cl2, differing in water solubility, melting point, chemical behavior, and biological activity. Their structures are... 

Chemists can make, or synthesize, many biologically active chemical compounds in the laboratory. (Chemical, chemical compound, and compound are interchangeable terms.) One starts with readily available simple molecules and proceeds to build more complex structures, one step at a time, through chemical reactions. 

The process through which a linear string of amino acid residues newly synthesized at a ribosome folds into a complex, three-dimensional, biologically active protein structure remains poorly understood. Consider how protein-folding contrasts with RNA-folding. Proteins have 20 distinct monomeric units, RNA only four. The amino acids include aromatic, hydrophobic, cationic, and anionic chemical properties compared to four comparable RNA nucleosides. Moreover, secondary and tertiary structures were fundamentally inter-linked in proteins, but are essentially distinct in RNA molecules. 

What Do You Know About the Sample How many other compounds are present and what are their chemical characteristics Is it necessary to recover all of the components or only part of the material What will the collected fractions be used for—to test biological activity do structure elucidation ... 

The Hansch Structure-Activity Approach As an Aid in Designing New Biologically Active Chemicals... 

A review has described the synthetic approaches, chemical properties, biological activities, and structure-activity relationships (SARs) of pyrazole nucleosides and condensed pyrazole nucleosides <2005NN1227>. Many of the references are pre-1996, and only selected post-1996 examples will be cited here. 

The subject of interest in relating reactivity (or biological activity) to structure is the change in the property of the compound upon interaction with a system, chemical or biological. The change in the property is the difference between its final and initial value. Applying the additivity approximation results in equation 2. 

Partial and total ranking methods have been widely used to perform data exploration, investigate the inter-relationships of objects and/or variables and set priorities. However it appears a very useful tool even for modelling purposes. Mathematical models have become an extremely useful tool in several scientific fields like environmental monitoring, risk assessment, QSAR and QSPR, i.e. in the search for quantitative relationships between the molecular structure and the biological activity/ chemical properties of chemicals. 

However, Edwin A. Abbott s fanciful two-dimensional world described in Flat-land is no more the world of molecules and chemical reactions than it was the world around us. While molecular topology is adequate to explain many aspects of chemical behavior, the evolution of quantitative models for structure-activity relations is unavoidably moving into the realm of three-dimensional (3D) structure. Modern computing enables rapid manipulation of 3D chemical structures, and it is leading the way for a proliferation of models for the quantification of electronic structure. For complex behavior of chemicals including physicochemical properties, reactivity, and biological activity, 3D structures are essential. 

Figure 1 Bulk drugs from natural sources Paclitaxel (antileukemic and antitumor) and lovastatin (inhibitor of cholesterol biosynthesis) are examples of the diverse and complex structures made by plant and microbial cell biosyntheses, respectively. In most instances of such compounds having desirable biological activities, their structural and chiral complexities make chemical synthesis not competitive with isolation from biosynthesis.

Nowadays, in science, there is a basic assumpion that molecular properties and structural characteristics are closely connected to biological functions of the compounds. It is often assumed that compounds with similar properties and structures also display similar biological responses. Chemical structure encodes a large amount of information explaining why a certain molecule is active, toxic or insoluble (Rajarshi, 2008). Thus to understand the mechanism of action of a drug it is necessary to interpret the role played by its molecular and structural properties. 

The chemical structure of A -tetrahydrocannabinol, determined by Gaoni and Mechoulam in 1964, is illustrated in Figure 6.3. Unlike many other biologically active chemicals of plant origin, A -tetrahydrocannabinol is a highly hydrophobic molecule, a property that has hindered the progress on its mode of action for nearly three decades. Indeed, not only was A -tetrahydrocannabinol more difficult to handle experimentally than such hydrophylic alkaloids as cocaine or morphine, but also its preference for lipid... 

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