An official website of the United States government
Here's how you know
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Structures of folic acid, aminopterin and methotrexate. The arrow indicates the point of cleavage. The stars indicate the points where aminopterin and methotrexate differ from folic acid.