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.
Comparison of bond lengths (Å) and charges (NPA) of isolated bicylic urea unit of biotin (8), the urea group when bound in the (strept)avidin model binding sites (9), and the conjugate base (10). Structures were optimized by B3LYP/6-31+G(d,p).
