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PubChem
PubChem is a database of Chemistry, chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information (NCBI), a component of the National Library of Medicine, which is part of the United States National Institutes of Health (NIH). PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be freely downloaded via FTP. PubChem contains multiple substance descriptions and small molecules with fewer than 100 atoms and 1,000 bonds. More than 80 database vendors contribute to the growing PubChem database. History PubChem was released in 2004 as a component of the Molecular Libraries Program (MLP) of the NIH. As of November 2015, PubChem contains more than 150 million depositor-provided substance descriptions, 60 million unique chemical structures, and 225 million biological activity test results (from over 1 million assay experiments performe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical File Format
A chemical file format is a type of data file which is used specifically for depicting molecular data. One of the most widely used is the chemical table file format, which is similar to ''Structure Data Format'' (SDF) files. They are text files that represent multiple chemical structure records and associated data fields. The XYZ file format is a simple format that usually gives the number of atoms in the first line, a comment on the second, followed by a number of lines with atomic symbols (or atomic numbers) and cartesian coordinates. The Protein Data Bank Format is commonly used for proteins but is also used for other types of molecules. There are many other types which are detailed below. Various software systems are available to convert from one format to another. Distinguishing formats Chemical information is usually provided as files or streams and many formats have been created, with varying degrees of documentation. The format is indicated in three ways:(see ) * ''f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Assays
An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a target entity. The measured entity is often called the analyte, the measurand, or the target of the assay. The analyte can be a drug, biochemical substance, chemical element or compound, or cell in an organism or organic sample. An assay usually aims to measure an analyte's intensive property and express it in the relevant measurement unit (e.g. molarity, density, functional activity in enzyme international units, degree of effect in comparison to a standard, etc.). If the assay involves exogenous reactants (the reagents), then their quantities are kept fixed (or in excess) so that the quantity and quality of the target are the only limiting factors. The difference in the assay outcome is used to deduce the unknown quality or quantit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Center For Biotechnology Information
The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is located in Bethesda, Maryland, and was founded in 1988 through legislation sponsored by US Congressman Claude Pepper. The NCBI houses a series of databases relevant to biotechnology and biomedicine and is an important resource for bioinformatics tools and services. Major databases include GenBank for DNA sequences and PubMed, a bibliographic database for biomedical literature. Other databases include the NCBI Epigenomics database. All these databases are available online through the Entrez search engine. NCBI was directed by David Lipman, one of the original authors of the BLAST sequence alignment program and a widely respected figure in bioinformatics. GenBank NCBI had responsibility for making available the GenBank DNA seque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Chemical Identifier
The International Chemical Identifier (InChI, pronounced ) is a textual identifier for chemical substances, designed to provide a standard way to encode molecular information and to facilitate the search for such information in databases and on the web. Initially developed by the International Union of Pure and Applied Chemistry (IUPAC) and National Institute of Standards and Technology (NIST) from 2000 to 2005, the format and algorithms are non-proprietary. Since May 2009, it has been developed by the InChI Trust, a nonprofit charity from the United Kingdom which works to implement and promote the use of InChI. The identifiers describe chemical substances in terms of ''layers'' of information — the atoms and their bond connectivity, tautomeric information, isotope information, stereochemistry, and electronic charge information. Not all layers have to be provided; for instance, the tautomer layer can be omitted if that type of information is not relevant to the particular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simplified Molecular Input Line Entry Specification
The Simplified Molecular Input Line Entry System (SMILES) is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules. The original SMILES specification was initiated in the 1980s. It has since been modified and extended. In 2007, an open standard called OpenSMILES was developed in the open source chemistry community. History The original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo (USEPA) and Albert Leo and Corwin Hansch (Pomona College) for supporting the work, and Arthur Weininger (Pomona; Daylight CIS) and Jeremy Scofield (Cedar River Software, Renton, WA) for assistance in progra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XLogP
In the physical sciences, a partition coefficient (''P'') or distribution coefficient (''D'') is the ratio of concentrations of a compound in a mixture of two immiscible solvents at equilibrium. This ratio is therefore a comparison of the solubilities of the solute in these two liquids. The partition coefficient generally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized). In the chemical and pharmaceutical sciences, both phases usually are solvents. Most commonly, one of the solvents is water, while the second is hydrophobic, such as 1-octanol. Hence the partition coefficient measures how hydrophilic ("water-loving") or hydrophobic ("water-fearing") a chemical substance is. Partition coefficients are useful in estimating the distribution of drugs within the body. Hydrophobic drugs with high octanol-water partition coefficients are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Institutes Of Health
The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in 1887 and is part of the United States Department of Health and Human Services (HHS). Many NIH facilities are located in Bethesda, Maryland, and other nearby suburbs of the Washington metropolitan area, with other primary facilities in the Research Triangle Park in North Carolina and smaller satellite facilities located around the United States. The NIH conducts its scientific research through the NIH Intramural Research Program (IRP) and provides significant biomedical research funding to non-NIH research facilities through its Extramural Research Program. , the IRP had 1,200 principal investigators and more than 4,000 postdoctoral fellows in basic, translational, and clinical research, being the largest biomedical research institution in the world, while, as of 2003, the extramural arm provided 28% of biomedical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during chemical reaction, reactions with other chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the prop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chirality (chemistry)
In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotation (geometry), rotations, translation (geometry), translations, and some Conformational isomerism, conformational changes. This geometric property is called chirality (). The terms are derived from Ancient Greek (''cheir'') 'hand'; which is the canonical example of an object with this property. A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. The two enantiomers have the same chemical properties, except when reacting with other chiral compounds. They also have the same physics, physical properties, except that they often have opposite optical activity, optical activities. A homogeneous mixture of the two enantiomers in equal parts is said to be racemic mixture, racem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formal Charge
In chemistry, a formal charge (F.C. or ), in the covalent view of chemical bonding, is the hypothetical charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity. In simple terms, formal charge is the difference between the number of valence electrons of an atom in a neutral free state and the number assigned to that atom in a Lewis structure. When determining the best Lewis structure (or predominant resonance structure) for a molecule, the structure is chosen such that the formal charge on each of the atoms is as close to zero as possible. The formal charge of any atom in a molecule can be calculated by the following equation: q^ = V - L - \frac where is the number of valence electrons of the neutral atom in isolation (in its ground state); is the number of non-bonding valence electrons assigned to this atom in the Lewis structure of the molecule; and is the total num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotope
Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemical element), but different nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have similar chemical properties, they have different atomic masses and physical properties. The term isotope is derived from the Greek roots isos (wikt:ἴσος, ἴσος "equal") and topos (wikt:τόπος, τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by Scottish doctor and writer Margaret Todd (doctor), Margaret Todd in a 1913 suggestion to the British chemist Frederick Soddy, who popularized the term. The number of protons within the atomic nuc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
