Take a sneak peek at the new NIST.gov and let us know what you think!
(Please note: some content may not be complete on the beta site.).

View the beta site
NIST logo
Bookmark and Share

Isotope Enrichment Calculator


The NIST Isotope Enrichment Calculator is a program written in Visual Basic which determines the percentage of 15N enrichment of stable isotope-labeled peptides or proteins.  A multinomial analysis of Hsu (Anal. Chem. 560 1356-1361 (1984)) is used to determine the theoretical isotopic distribution of an input sequence at incremental isotopic percentages which are compared with an input experimentally derived profile. The theoretical profile of 15N percentage which maximizes the Pearson correlation as described by MacCoss et al. (Anal. Chem. 77 7646-7653 (2005)) is output along with the coefficient.


isotope calc


Version: 1.2

Last Updated: September 24, 2013

Type of software: Visual Basic Executable for PC


Eric L. Kilpatrick


Windows XP, Vista, or Windows 7

Download information:

Download NIST Isotope Enrichment Calculator v1.2


This software was developed at the National Institute of Standards and Technology by employees of the Federal Government in the course of their official duties.  Pursuant to title 17 Section 105 of the United States Code this software is not subject to copyright protection and is in the public domain.  Each of these packages is an experimental system. NIST assumes no responsibility whatsoever for its use by other parties, and makes no guarantees, expressed or implied, about its quality, reliability, or any other characteristic. We would appreciate acknowledgement if the software is used; please cite Kilpatrick et al., Protein Purification and Expression 85(2012) 94-99. This software can be redistributed and/or modified freely provided that any derivative works bear some notice that they are derived from it, and any modified versions bear some notice that they have been modified.