| 3D Macromolecular Structures |
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To receive e-mail news about changes to the Molecular Modeling Database and its associated resources, subscribe to the structure-announce@ncbi.nlm.nih.gov mailing list by completing a brief form or sending an e-mail message with the word subscribe in the subject line to structure-announce-request@ncbi.nlm.nih.gov.
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iCn3D 2.0 released
[17 August 2016] iCn3D 2.0 is now available on NCBI web servers (https://www.ncbi.nlm.nih.gov/Structure/icn3d/icn3d.html) and on GitHub (https://github.com/ncbi/icn3d). New features in this release include:
- an interactions schematic (2D view) that is available when a structure is loaded as an MMDB file. It can be used to select/highlight molecular components (illustrated example) or interaction interfaces (illustrated example)
- calculation of secondary structures if the input PDB file does not define secondary structure information
- previous files src/icn3d.js, src/full_ui.js, and src/simple_ui.js have been separated into small files
The iCn3D help document provides additional details about the viewer, including examples of how iCn3D can be used.
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New version of VAST+ released
[27 JULY 2016] A new version of VAST+ was released. It provides a refined structure-based alignment of similar macromolecular complexes, and displays the 3D superpositions in the recently released iCn3D, a WebGL-based structure viewer. The initial alignment of similar macromolecular complexes, which became available with the first release of VAST+, uses the complete set of individually aligned macromolecules and corresponding matching amino acids to calculate a superposition of the complex structures. In contrast, the new release of VAST+ identifies a subset set of amino acids that have highly similar 3D positions in the query and subject complex structure, and uses it to create a refined alignment that allows identification and visualization of the most similar portion of the structures (the structurally invariant core of the assembly), as well as the differences between the structures.
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iCn3D 1.0 is now available
[28 APRIL 2016] iCn3D 1.0 is now available. It is a new WebGL-based viewer for interactive viewing of three-dimensional macromolecular structures on the web, without the need to install a separate application, and enables you to:
- interactively view 3D structures and corresponding sequence data
- interactively view superpositions of similar structures
- cutomize the display of a structure and generate a URL that allows you to share the link
- incorporate iCn3D into your own pages
An example of each is accessible from the "About iCn3D" page.
iCn3D can be accessed from the molecular graphic that appears on the structure summary page for any record in the Molecular Modeling Database (MMDB).
As an example, view the MMDB summary page for the Tumor Suppressor P53 Complexed with DNA (1TUP). Click on the spin icon  in the molecular graphic to open the structure in the basic version of iCn3D, or click on the launch icon  to open the structure in the advanced (full feature) version of iCn3D in a separate window.
You can also access the advanced version of iCn3D directly at https://www.ncbi.nlm.nih.gov/Structure/icn3d/full.html, where you can use the "File" menu to retrieve a structure by its ID or to open a structure file on your local computer.
The source code is available from GitHub (https://github.com/ncbi/icn3d) for developers who would like to customize the program and/or contribute code, and for users who would like to run the program on their local computer.
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New structure summary pages featuring interactive molecular graphic
[28 APRIL 2016] MMDB structure summary pages have been revised to feature interactive molecular graphics using iCn3D, a new WebGL-based viewer for three-dimensional macromolecular structures. A spin icon in the molecular graphic loads a basic version of iCn3D into the web page, enabling you to render the structure in the desired style and highlight molecules of interest by clicking on the corresponding interactions schematic. A launch icon opens the advanced (full feature) version of iCn3D in a separate window. As an example, view the MMDB summary page for Tumor Suppressor P53 Complexed With DNA (1TUP). Additional information is available in the MMDB help document and the About iCn3D page.
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VAST+ released! Find 3D structures with similar macromolecular complexes
[06 DEC 2013] VAST+ is a new tool designed to identify macromolecules that have similar 3-dimensional structures, with an emphasis on finding similar macromolecular complexes. The similarities are calculated using purely geometric criteria, without regard to sequence similarity, and therefore can identify distant homologs. VAST+ is built upon the original Vector Alignment Search Tool (VAST), and expands the capabilities of that program by taking into account the biological unit ("biounit") of each structure, not just individual protein molecules or their substructures. A recent publication provides details and the VAST+ help document includes a comparison of original VAST and VAST+, as well as examples of how can VAST+ be used to learn more about proteins. (Please note: in order to view the 3D superpositions of similar biological units, you must install the most recent version of the NCBI molecular viewing software, Cn3D 4.3.1.)
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Cn3D 4.3.1 now available
[06 DEC 2013] A new version of NCBI's macromolecular structure viewing program, Cn3D 4.3.1, is now available (download). New features include the ability to view superpositions of 3D structures that have similar biological units, as identified by the newly released VAST+, an enhanced version of the Vector Alignment Search Tool (VAST). In addition, Cn3D 4.3.1 now uses the MIME type: application/vnd.ncbi.cn3d. Up to version 4.3, Cn3D used the MIME type: chemical/ncbi-asn1-binary.
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Merged PDB split files: View large macromolecules in their entirety
[25 JUL 2012] It is now possible to interactively view and/or download large macromolecular structures in their entirety, such as the viral capsid illustrated below, the rat liver vault, and the ribosome structure by Nobel Laureate V. Ramakrishnan, and more. These and approximately 150 other large macromolecular structures exceed the size limits implicit to the PDB file format and are therefore split into several PDB files. The MMDB data processing procedure merges the files into a single structure record, and the merged files can be viewed interactively with Cn3D 4.3 (install). You can also retrieve all merged files, if desired.
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PDB SPLIT FILES for the
Adeno-associated Virus Serotype 6 (Aav-6) |
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MMDB MERGED FILE |
| PDB ID: 1VU0
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PDB ID: 1VU1
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PDB ID: 3TSX
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MMDB ID: 99554 |
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Click on the thumbnail image above to open the merged file in Cn3D 4.3 and interactively view the entire structure and its sequence data. |
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Entrez Structure interface redesign
[25 JULY 2011] NCBI's Structure database now has a revised home page, search interface, and search results display, to have functions similar to those available in PubMed. Changes include: (a) a streamlined home page with links to related resources; (b) an "Advanced Search" page, which provides the ability to build a query one term at a time, browse the index of any search field, and combine earlier searches; and (c) new search results displays that provide links in the right margin to search filters, related data, and tools.
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Cn3D 4.3 now available
[25 MAY 2011] A new version of NCBI's macromolecular structure viewing program, Cn3D 4.3, is now available (download). New features include the ability to view biological unit(s), including those containing molecules generated by applying transformations from crystallographic symmetry, side by side stereo views, additional alignment algorithms for editing multiple sequence alignments, new highlighting features, and more. It is similar to the Cn3D 4.2 preview release that was packaged with CDTree, but has been packaged as a standalone program and enhanced to handle the new Molecular Modeling Database (MMDB) data specification that now includes biological units and interactions.
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New structure summary pages featuring biological units and interactions
[09 MAY 2011] MMDB structure summary pages have been revised to display salient features of each structure, including its biological unit(s) and an interaction schematic depicting the interactions among the structure's molecular components, as in the human hemoglobin example below. The procedures to identify a structure's biological unit(s) and thresholds used to display interactions are described in the help document.
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Cn3D 4.2 preview available
[09 MAY 2011] A preview of a new version of NCBI's structure viewing program, Cn3D 4.2, is packaged together with the CDTree program (install). New features include:
- the ability to view the biological units identified within a structure, including those containing molecules generated by applying transformations from crystallographic symmetry
- side by side stereo views
- additional alignment algorithms for editing multiple sequence alignments
- new highlighting features
- more robust handling of sequence identifiers
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"Selected Structures" display in Entrez Structure search results
[03 JUN 2010] When you search the Entrez Structure (Molecular Modeling Database) database, a "Selected Structures" summary box now appears in the upper right corner of the search results page (for example, see the results of a search for p53 tumor suppressor). The "Selected Structures" box lists the top five protein domain families found among the retrieved structures, inferring protein function, as well as the top five organisms represented in the structures. It also provides easy access to various subsets of structure records in the search results, such as those composed of specific molecule combinations (e.g., protein-protein, protein-DNA, protein-chemical), and those with links to literature in PubMed or free full text in PubMed Central.
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Inferred Biomolecular Interactions Server (IBIS) publicly available
[18 AUG 2009] The NCBI Inferred Biomolecular Interactions Server (IBIS) server was made public. For a given protein sequence or structure query, IBIS reports physical interactions observed in experimentally-determined structures for this protein. IBIS also infers/predicts interacting partners and binding sites by homology, by inspecting the protein complexes formed by close homologs of a given query. To ensure biological relevance of inferred binding sites, the IBIS algorithm clusters binding sites formed by homologs based on binding site sequence and structure conservation. (read more about IBIS; additional publications)
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