This laboratory was the first to demonstrate that specific protein interactions could be preserved on conventional MALDI targets during the ionisation of non-binding components providing an indirect means with which to probe protein interactions. The approach was later described as "intensity fading" (and falsely described as new) by others.  For a review of the true history of the approach, download the PDF review article available here.

First reported in 1999, it was subsequently applied in the same year to a biological mixture in the form antigenicity studies of the influenza virus. It has since been applied to antibody interactions with gel-recovered antigens (2006, 2007) and in time-course experiments (2008) to measure the relative rates of binding. A computer algorithm (PRISM) to interpret such MALDI spectral pairs has also been developed (2007). The approach has also been applied to study the binding of anti-viral inhibitor drugs including the relative affinity of that binding (2012-today).  (see references below)




Downard KM (2016) Indirect Study of Non-Covalent Protein Complexes by MALDI Mass Spectrometry. Origins, Advantages and Applications of the "Intensity-Fading" Approach, Mass Spectrom. Rev., 35: 559-573.   PDF copy


Downard KM (2007) Softly. Softly. Detection of Protein Complexes by Matrix-assisted Laser Desorption Ionization Mass Spectrometry, in Mass Spectrometry of Protein Interactions, Downard KM ed., John Wiley & Sons, New Jersey U.S.A., pp. 25-43.


Downard KM (2013) An Immunoproteomics Approach to Screen the Antigenicity of the Influenza Virus, in Methods in Molecular Biology: Immunoproteomics (Ed. S. Twine & K. Fulton), Vol. 1061, Ch. 8, pg 141-153.


Downard KM, Morrissey B, Schwahn AB (2009) Mass Spectrometry Analysis of the Influenza Virus, Mass Spectrom. Rev. 28: 35-49.


Downard K.M. (2000) Contributions of Mass Spectrometry to Structural Immunology, J. Mass Spectrom. 35: 493-503.


Original references (from 1999):


Kiselar JG, Downard KM (1999) Direct Identification of Protein Epitopes by Mass Spectrometry without Immobilization of Antibody and Isolation of Antibody-Peptide Complexes, Anal. Chem. 17: 1792-1801.

Kiselar JG, Downard KM (1999) Antigenic Surveillance of the Influenza Virus by Mass Spectrometry, Biochemistry 43: 14185-14191.


Kiselar J.G., Downard K.M. (2000) Preservation and Detection of Specific Antibody-Peptide Complexes by Matrix-assisted Laser Desorption Ionization Mass Spectrometry, J. Am. Soc Mass Spectrom. 11: 746-750.


Ho JWK, Morrissey B, Downard KM (2007) A Computer Algorithm for the Identification of Protein Interactions from the Spectra of Masses (PRISM), J. Am. Soc. Mass Spectrom., 18, 563– 566. 


Application with Gel-Based Antigen Separation:

Morrissey B, Downard KM (2006) A Proteomics Approach to Survey the Antigenicity of the Influenza Virus by Mass Spectrometry, Proteomics 6: 2034-2041.


Other Protein-Antibody Studies:

Schwahn AB, Downard KM (2009) Antigenicity of a type A influenza virus through a comparison of hemagglutination inhibition and mass spectrometry immunoassays, J. Immunoassay Immunochem. 30: 245-261.

Morrissey B, Streamer M, Downard KM (2007) Antigenic Characterisation of H3N2 subtypes of the Influenza Virus by Mass Spectrometry, J. Virol. Methods 145: 106-114.


Time-Course Study:


Morrissey B, Downard KM (2008) Kinetics of Antigen-Antibody Interactions Employing a MALDI Mass Spectrometry Immunoassay, Anal. Chem. 80: 7720-7726.


Protein-Drug Applications:

Lu R, Muller P, Downard KM (2015) Molecular Basis of Influenza Hemaglutinin Inhibition with an Entry-Blocker Peptide by Computational Docking and Mass Spectrometry, Antiviral Chem. Chemother. 24: 109-117.

Muller P, Downard KM (2015) Catechins Inhibit Influenza Neuraminidase and its Molecular Basis with Mass Spectrometry, J. Pharmaceut. Biomed. Anal. 111: 222-230.

Swaminathan K, Muller P, Downard KM (2014) Substituent Effects on the Binding of Natural Product Anthocyanidin Inhibitors to Influenza Neuraminidase with Mass Spectrometry, Anal. Chim. Acta 828: 61-69.

Nasser Z, Swaminathan K, Muller P, Downard KM (2013) in-vitro Inhibition of the Influenza virus with the Anti-Viral Inhibitor Arbidol by a Proteomics based Approach with Mass Spectrometry, Antiviral Res. 100: 399-406.

Swaminathan K, Dyason JC, Maggioni A, von Itzstein M, Downard KM (2013) Binding of a Natural Anthocyanin Inhibitor to Influenza Neuraminidase by Mass Spectrometry, Anal. Bio. Chem. 405: 6563-6572.

Swaminathan K, Downard KM (2012) Anti-Viral Inhibitor Binding to Influenza Neuraminidase by MALDI Mass Spectrometry, Anal. Chem. 84: 3725-3730.

Additional Relevant Articles:


Downard K.M. (2000) Contributions of Mass Spectrometry to Structural Immunology, J. Mass Spectrom. 35: 493-503.

Mackun K., Downard KM (2003) Strategy for the Study of Protein-Protein Interactions of Gel- Separated Proteins by Mass Spectrometry, Anal. Biochem. 318: 60-70.


Kiselar JG, Downard KM (2001) Preservation of Specific Immune Complexes by Matrix-assisted Laser Desorption Ionization Mass Spectrometry, in Advances in Mass Spectrometry, Volume 15, E. Gelphi (ed.) John Wiley & Sons, Chichester, UK.