Calculation of Intrinsic eXchange rates of labile protons in proteins

I. Enter/ Upload the pdb file.

Enter the pdb id:
Upload the pdb file:


Enter the amino acid sequence and related structural information.

Position of cysteine residue(s). (Help)

Position of cis proline(s). (Help)

II. Enter the experimental conditions.

Temperature: K
Solvent: H 2 O D2O Others

Ionic Strength: Low High

Enter the reference rates if the solvent is other than D2O.

ka kb kw

Do you want to account for the effect of pKR of amino acids in the calculation ?

Yes No

III. Calculation of free energy exchange of amino acids.

Do you want to calculate residue specific free energy of proteins?

Upload the file containing kex values of amino acids.


Updated on May 8, 2015
for queries contact:
sivaram @
tricha @
Please cite the website and the following reference(s) in your publication(s) if you use CIntX.
1. T. Richa and T. Sivaraman. OneG: A computational tool for predicting cryptic intermediates in the unfolding kinetics of proteins under native conditions, PLoS ONE (2012), 7(3): e32465.
2. T. Richa and T. Sivaraman, CIntX: A software tool for calculating the intrinsic exchange rates of labile protons in proteins, J. Pharm. Sci. and Res. (2012), 4(6), 1852-1858.
3. T. Richa, Computational tools for predicting cryptic intermediates and metastable states in the unfolding kinetics of proteins under native conditions. Ph.D. Dissertation (2014), SASTRA University, Tamil Nadu, India.