The article by Hu et al.  mentions a compound "dithreitol" in the Saliva Proteome Analysis section (emphasis mine):
For the "shotgun" approach, saliva samples (1 mL) were pre-fractionated with the use of Millipore ultracentrifuge filters (Millipore Corp., Billerica, MA, USA). Individual fractions were treated with 10 mM dithreitol for 30 min and then 50 mM iodoacetamide for 30 min.
Google Books search results in several mentions of this compound in the literature, but I didn't find any further details except that it's probably a sulfhydryl reagent. This makes me think that "dithreitol" could be another name for dithiothreitol, but I didn't manage to find any solid references to support this proposition.
To sum it up: what is dithreitol, exactly, and what chemical and structural formulas does it posses?
- Hu, S.; Li, Y.; Wang, J.; Xie, Y.; Tjon, K.; Wolinsky, L.; Loo, R. R. O.; Loo, J. A.; Wong, D. T. Human Saliva Proteome and Transcriptome. J Dent Res 2006, 85 (12), 1129–1133. DOI: 10.1177/154405910608501212.