Data format .cif Web service URL webcsd.ccdc.cam.ac.uk | Website www.ccdc.cam.ac.uk Web WebCSD | |
Description Molecular structure elucidation
X-ray crystallography
Cheminformatics
Metalorganic
Organometallic Research center Cambridge Crystallographic Data Centre | ||
The Cambridge Structural Database (CSD) is both a repository and a validated and curated resource for the three-dimensional structural data of molecules generally containing at least carbon and hydrogen, comprising a wide range of organic, metal-organic and organometallic molecules. The specific entries are complementary to the other crystallographic databases such as the PDB, ICSD and PDF. The data, typically obtained by X-ray crystallography and less frequently by neutron diffraction, and submitted by crystallographers and chemists from around the world, are freely accessible (as deposited by authors) on the Internet via the CSD's parent organization's website (CCDC, Repository). The CSD is overseen by the not-for-profit incorporated company called the Cambridge Crystallographic Data Centre, CCDC.
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The CSD is widely recognized as the world’s repository for small-molecule organic and metal-organic crystal structures, and has become an essential resource to scientists around the world. Structures deposited with CCDC are made publicly available for download at the point of publication or at consent from the depositor. They are also scientifically enriched and included in the Cambridge Structural Database (CSD) which underpins a range of software solutions offered by CCDC. Targeted subsets of the CSD are also freely available to support teaching and other activities.
History
The CCDC grew out of the activities of the crystallography group led by Dr Olga Kennard OBE FRS in the Department of Organic, Inorganic and Theoretical Chemistry of the University of Cambridge. From 1965, the group began to collect published bibliographic, chemical and crystal structure data for all small molecules studied by X-ray or neutron diffraction. With the rapid developments in computing taking place at this time, this collection was encoded in electronic form and became known as the Cambridge Structural Database (CSD).
The CSD was one of the first numerical scientific databases to begin operations anywhere in the world, and received academic grants from the UK Office for Scientific and Technical Information and then from the UK Science and Engineering Research Council. These funds, together with subventions from National Affiliated Centres, enabled the development of the CSD and its associated software during the 1970s and 1980s. The first releases of the CSD System to the United States, Italy and Japan occurred in the early 1970s. By the early 1980s the CSD System was being distributed in more than 30 countries worldwide. As of 2014, the CSD System is now distributed to academics in 70 countries worldwide.
During the 1980s, interest in the CSD System from pharmaceutical and agrochemicals companies increased significantly. This led to the establishment of the CCDC as an independent company in 1987, with the legal status of a non-profit charitable institution, and with its operations overseen by an international Board of Governors. The CCDC moved into purpose-built premises on the site of the University Department of Chemistry in 1992.
Dr Kennard retired as Director in 1997 and was succeeded by Dr David Hartley (1997-2002) and Dr Frank Allen (2002-2008). Dr Colin Groom was appointed as Executive Director from 1 October 2008.
CCDC software products have now diversified to make maximum use of crystallographic data in applications in the life sciences and crystallography. Much of this software development and marketing is now carried out by CCDC Software Limited (founded in 1998), a wholly owned subsidiary which covenants all of its profits back to the CCDC.
Although the CCDC is now a self-administering organization, it retains close links with the University of Cambridge, and is a University Partner Institution that is qualified to train postgraduate students for higher degrees (PhD, MPhil).
The CCDC established US applications and support operations in the USA in October 2013 at Rutgers, the State University of New Jersey, where it is co-located with the RCSB Protein Data Bank
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The CSD is continually updated with new structures (>50,000 new structures each year) and with improvements to existing entries. Entries (structures) in the repository are released for public access shortly after the corresponding entry has appeared in the peer-reviewed scientific literature.
Periodically, general statistics about the breadth of CSD holdings are reported. As of 6 January 2014, the summary statistics are as follows:
As of 6 January 2014, the top 25 scientific journals in terms of publication of structures in the CSD repository were:
These 25 journals account for 499,109 of the 686,944 or 72.7% of the structures in the CSD.
These data show that most structures are determined by X-ray diffraction, with less than 1% of structures being determined by neutron diffraction or powder diffraction. The number of error-free coordinates were taken as a percentage of structures for which 3D coordinates are present in the CSD.
The significance of the structure factor files, mentioned above, is that, for CSD structures determined by X-ray diffraction that have a structure file, a crystallographer can verify the interpretation of the observed measurements.
Growth trend
Historically, the number of structures in the CSD has grown at an approximately exponential rate passing the 25,000 structures milestone in 1977, the 50,000 structures milestone in 1983, the 125,000 structures milestone in 1992, the 250,000 structures milestone in 2001, the 500,000 structures milestone in 2009, and is estimated to reach the 1,000,000 structures milestone in 2017.
Note: data for 1923-1964 are aggregated together in the last line of the table.
File format
The primary file format for CSD structure deposition, adopted around 1991, is the "Crystallographic Information file" format, CIF.
The deposited CSD files can be downloaded in the CIF format. The validated and curated CSD files can be exported in a wide range of formats, including CIF, MOL, Mol2, PDB, SHELX and XMol, using tools in the CSD System.
The CCDC uses two different codes to distinguish between the deposited CSD entry and the curated CSD entry. For example, one specific ‘Personal Communication’ of an organic molecule was deposited with the CCDC and assigned the deposition number 'CCDC-991327.' This allows free public access to the data as deposited. From the deposited data, selected information is extracted to prepare the validated and curated CSD entry which was assigned the refcode 'MITGUT'. The validated and curated entry is included in the CSD System and WebCSD distributions, with availability restricted to those making appropriate contributions.
Viewing the data
The structure files may be viewed using one of several open source computer programs such as Jmol. Some other free, but not open source programs include MDL Chime, Pymol, UCSF Chimera, Rasmol, WINGX, the CCDC and Discovery Studio provides a free version of its molecule visualization program Mercury.