Four groups of proteins which bind IgE were identified on immunoblots: <5kD, 15-20kD, 25-40kD, 45-50kD (Arshad et al 1991 ).
Nordlee et al. (1996)  reported that sera from 8/9 Brazil nut allergic subjects bound to the 2S protein from Brazil nut and sera from 7/9 patients bound a similar protein from transgenic soybean. Sera from a single patient bound a 42 kDa protein from Brazil nut but not the 2S protein.
Bartolomé et al. (1997)  found IgE-binding proteins included the 9 kDa and 4 kDa subunits of the 2S albumin and also the alpha-subunits, 33.5 kDa and 32 kDa, and at least one of the beta-subunits, approximately 21 kDa, of the 12S Brazil nut globulin (also called the 11S globulin).
Pastorello et al. (1998)  found that all the Brazil nut allergic patients had specific IgE against a 9 kDa allergen. Other allergenic polypeptides were detected at less than 5 kDa (2 of 11 patients, 18.2%), 14.4 kDa (4 of 11 patients, 36.6%), 22 kDa (4 of 11 patients, 36.6%), 35 kDa (4 of 11 patients, 36.6%), and 48 and 55 kDa (3 of 11 patients, 27.3%). 4 asymtomatic patients showed weak IgE binding at 25 to 58 kDa, which in symptomatic patients represent minor allergens.
With the 12.5% SDS-PAGE gels, Borja et al. (1999)  found IgE binding to five bands of 52.2, 41.4, 39, 33.4, and 23.7 kDa under non-reducing conditions. IgE binding under reducing conditions was restricted to two bands of 33.4 and 21.4 kDa. The tricine SDS-PAGE immunoblotting under non-reducing conditions, revealed IgE binding to bands of 19.3, 18.4, and a wide band of 7-12 kDa, probably the 2S albumin. A loss of binding was observed under reducing conditions.
Asero et al. (2002)  found that their patient's serum reacted strongly to four distinct Brazil nut proteins at about 18, 25, 33, and 45 kDa, but no reactivity against 2S albumin (10 kDa) was found.