Explore characteristics of amino acids by comparing their structural and chemical properties, predicting protein sequence changes caused by mutations, viewing common substitutions, and browsing functions of given residues in conserved domains.

BLAST finds regions of similarity between biological sequences. The program compares nucleotide or protein sequences to sequence databases and calculates the statistical significance. Technical documentation at http://blast.ncbi.nlm.nih.gov/Blast.cgi?CMD=Web&PAGE_TYPE=BlastDocs

The BioProject database provides an organizational framework to access information about research projects with links to data that have been or will be deposited into archival databases maintained at members of the International Nucleotide Sequence Database Consortium (INSDC, which comprises the DNA DataBank of Japan (DDBJ), the European Nucleotide Archive at European Molecular Biology Laboratory (ENA), and GenBank at the National Center for Biotechnology Information (NCBI)).

The BioSample database contains descriptions of biological source materials used in experimental assays.

The NCBI BioSystems Database provides integrated access to biological systems and their component genes, proteins, and small molecules, as well as literature describing those biosystems and other related data throughout Entrez.

A collection of online biomedical books whose full text can be searched through the Entrez system. Bookshelf provides free online access to books and documents in life science and healthcare.

This resource provides cytogenetic locations for features or sequence locations, or sequence locations for cytogenetic locations.

A stand-alone application for classifying protein sequences and investigating their evolutionary relationships. CDTree can import, analyze and update existing Conserved Domain (CDD) records and hierarchies, and also allows users to create their own.

ClinVar aggregates information about genomic variation and its relationship to human health.

COBALT is a protein multiple sequence alignment tool that finds a collection of pairwise constraints derived from conserved domain database, protein motif database, and sequence similarity, using RPS-BLAST, BLASTP, and PHI-BLAST.