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In the Cambridge Structural Database of small-molecule structures, more than 95% of the 500,000+ crystals have an R-factor lower than 0.15, and 9.5% have an R-factor lower than 0.03. Crystallographers also use the Free R-Factor ( R F r e e {\displaystyle R_{Free}} ) [ 3 ] to assess possible overmodeling of the data.
An R F value will always be in the range 0 to 1; if the substance moves, it can only move in the direction of the solvent flow, and cannot move faster than the solvent. For example, if particular substance in an unknown mixture travels 2.5 cm and the solvent front travels 5.0 cm, the retardation factor would be 0.50.
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula −OH and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry , alcohols and carboxylic acids contain one or more hydroxy groups.
In organic chemistry, an acetyl group is a functional group denoted by the chemical formula −COCH 3 and the structure −C(=O)−CH 3. It is sometimes represented by the symbol Ac [5] [6] (not to be confused with the element actinium). In IUPAC nomenclature, an acetyl group is called an ethanoyl group.
An overview of the different components included in the field of chemical biology. Chemical biology is a scientific discipline between the fields of chemistry and biology.The discipline involves the application of chemical techniques, analysis, and often small molecules produced through synthetic chemistry, to the study and manipulation of biological systems. [1]
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
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Forsterite. In chemistry, isomorphism has meanings both at the level of crystallography and at a molecular level. In crystallography, crystals are isomorphous if they have identical symmetry and if the atomic positions can be described with a set of parameters (unit cell dimensions and fractional coordinates) whose numerical values differ only slightly.