Retropective Analysis of Hydrogen Cyanide Exposure via Mass Spectral Detection of a Unique Cys-SCN Human Serum Albumin Adduct
Tue 11:30 AM - Track 3: Protein Adduct Methods
Michael Fasco
NY State Dept of Health
*Michael J Fasco, *Charles R. Hauer III, *Erasmus Schneider, *Kenneth M. Aldous, #Michael Dailey

*New York State Department of Health, Wadsworth Center, Albany, NY 12201
#Albany Medical Center, Albany, NY 12208
Cyanide (CN = HCN + CN-) is a renowned poison, as well as a potential terrorist weapon and neurotoxicant. CN is ubiquitous in the environment and can reach potentially dangerous levels in certain workplaces, improperly processed foods, such as cassava root, and in fire smoke. Despite a plethora of studies conducted over that last half century, relatively little is known of potential adverse health effects in groups that are at risk for above normal exposure such as firefighters and first responders.

CN exposure is normally determined in whole blood using GC/MS. However, CN is rapidly metabolized and cleared from this compartment (t1/2 < 1 hr), and it is common for several half-lives to have passed before blood samples are drawn for analysis. This variable, coupled with metabolic diversity among individuals, and a very narrow toxic index, have made correlations between CN exposure and health highly problematic.

Prior studies by us have shown the potential of Cys-SCN human serum albumin (HSA) adducts formed by reaction of CN with susceptible protein disulfides to act as retrospective surrogates of CN exposure. We have since discovered a HSA-SCN adduct that is detectable in variable amounts in all of the samples obtained from individuals so far. Base catalysis in the presence of guanidine hydrochloride releases a uniquely modified peptide identified by LC-MS/MS. Inclusion of an internal serum standard containing HSA labeled with 13C15N and enhanced detection using LC-MS/MS Multiple Reaction Monitoring (MRM) permits quantitation of the target peptide with high sensitivity and precision. Reaction of CN in vitro with HSA disulfides is specific, rapid, and concentration dependent within the putative physiologically relevant range, demonstrating their potential as biomarkers of exposure. Data obtained with a small cohort of normal human subjects are presented.
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