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The lectin amaranthin, purified from the seeds of Amaranthus caudatus, has been shown to react specifically with the Gal beta 1,3GalNAc-alpha and the NeuAc alpha 2,3Gal beta 1,3GalNAc-alpha sequence which represent the T antigen and the cryptic T antigen, respectively. We report here the development of labeling techniques that apply amaranthin to stain paraffin sections from rat fetuses. Amaranthin staining was inhibited by pre-incubation of lectin-gold complexes with 10 mM Gal beta 1,3GalNAc-alpha-O-benzyl (synthetic T antigen) or 10 mM Gal beta 1,3GalNAc-alpha-O-aminophenylethyl-human serum albumin (T antigen neoglycoprotein), asialoglycophorin, asialofetuin, and asialomucin. The beta-elimination reaction also abolished the lectin staining demonstrating specificity for O-glycosidically linked structures. A comparison with monoclonal anti-T antigen antibody immunostaining demonstrated that amaranthin detects the T antigen and its cryptic form in tissue sections. Application of the galactose oxidase-Schiff sequence abolished amaranthin (and anti-T antibody) binding to the T antigen but not to its cryptic form, and therefore permitted their differentiation in tissue sections. Histochemical evidence was obtained indicating that amaranthin is a more specific anti-T reagent than peanut lectin. Data are presented that show the differential expression of the T antigen and the cryptic T antigen in organs and cells of rat fetuses late in gestation. Therefore, amaranthin can be used for histochemical detection of the T antigen and the cryptic T antigen, and facilitates discrimination between them.

Amaranthin is the lectin present in the seeds of Amaranthus caudatus, which specifically binds the T-disaccharide (Gal beta 1,3GalNAc alpha-O-). The lectin is composed of a single type of subunit with Mr = 33,000-36,000 (Rinderle et al., 1989). Equilibrium sedimentation (Mr = 62,900) and low-angle laser light scattering (Mr = 61,400) methods have been used to unambiguously establish the native multimeric structure of amaranthin as a homodimer. These absolute molecular weight methods and the calculated Stokes radius (27.2 A) indicate that the amaranthin dimer is highly compact relative to typical globular proteins, and thus, anomalous molecular weight values are obtained when simple size exclusion chromatography is used to determine the molecular weight of amaranthin. Studies with a homobifunctional cross-linking reagent and amaranthin further support the existence of a lectin homodimer. The stoichiometry of carbohydrate binding was determined to be one T-disaccharide-binding site per amaranthin subunit (Ka = 3.6 X 10(5) M-1). Amaranthin exhibits hydrophobic-binding properties as indicated by binding of 8-anilino-1-naphthalene-sulfonate (Ka = 3.6 X 10(3) M-1) and 6-toluidinyl-2-naphthalenesulfonate (Ka = 2 X 10(4) M-1). Serological studies suggest that amaranthin does not appear to be present in the stems or leaves of the A. caudatus plant, nor were there any indications for the presence of cross-reactive material.

1,2,3,4-Tetrahydro-7,12-dimethylbenz[a]anthracene (THDMBA) is an animal carcinogen which lacks an aromatic bay-region and shows promise as a model to investigate non-classical mechanisms of carcinogenesis. The fluorine-substituted derivatives at positions 5 and 6 on the B-ring exhibit a striking range of oncogenic potential wherein the 6F-THDMBA is twice as potent as the parent carcinogen, but the 5F-THDMBA is virtually inactive. To study structure-reactivity relationships for these fluorine regioisomers, we have determined the three-dimensional structures of the compounds by single-crystal X-ray diffraction. These crystal structures are the first such to be reported for any monofluoro anthracene (or pyrene) derivative. The partially-reduced A-ring exists in both enantiomeric half-chair conformers in the crystalline state, and the compounds have quasi-planar anthracene ring systems which exhibit a right-handed twist in the 'beta'-conformer, with the expected opposite twist in the other. A complete analysis of bond lengths, bond angles and torsion angles is presented. Preliminary electrostatic potentials have been derived from the X-ray data sets, and the results indicate significant differences in potential between 5F- and 6F-THDMBA at positions near the partially reduced bay region. Such results are likely to be of importance in the understanding of metabolic activation to reactive intermediates capable of bonding covalently to DNA.