Analyses have been made for crude protein, amino acids, and trypsin inhibitor content of 21 cultivars of sweet potato collected from two regions of the highlands of Papua New Guinea, one (Upper Mendi region) of high incidence of Enteritis necroticans (EN) and the other (Erave region) of low incidence of EN. The incidence of EN occurs in populations that are reported to be low in protein; hence, the analysis of the staple food (sweet potato) may give a clue to the difference between the two regions. No significant differences were found in the crude protein content, amino acid scores, or trypsin inhibitor contents between the sweet potatoes from the two regions. The range of crude protein content is 0.5-2 g of protein/100 g of fresh sweet potato; the S-containing amino acids (cystine plus methionine) are limiting in 65% of cases, followed by lysine (23%), leucine (6%), and other amino acids. The average chemical score is 0.6. The trypsin inhibitor content varies greatly over a 67-fold range. No significant correlation (r = 0.057) is found between trypsin inhibitor and crude protein.

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Equilibrium systems containing intercalation complexes formed between the novel anthracycline drug, 3‐fluoro‐4‐demethoxydaunomycin (3FD), and the hexanucleotide duplex d(CTGCAG)2 have been studied by 19FNMR spectroscopy. Solutions containing a 1:1 molar ratio of 3FD/d(CTGCAG)2 gave four 19F signals which have been assigned to each of four possible intercalation isomers for the 1:1 3FD · d(CTGCAG)2 complex, which we denote by [d(CTGCAG)2][3FD]; these were where 3FD bound between the 5′‐CT‐3′,5′‐TG‐3′, 5′‐GC‐3′ or 5′‐CA‐3′ base sequences, with the drug sugar moiety lying in the minor groove and pointed in the 3′ direction in each case. Changes in temperature and NaCl concentration affecting the equilibrium distribution of these isomers were studied and indicated that no overriding binding site preference prevailed under standard biochemical conditions. Formation of some of the 2:1 3FD · d(CTGCAG)2 complex occurred when a solution of [d(CTGCAG)2][3FD] was exposed to excess 3FD; however, this complex was unstable to gel filtration and no co‐operative binding of the second 3FD molecule was observed.

Abstract:The heat stability of trypsin inhibitors from rice (Oryza sativa L), sweet potato (Ipomoea batatas (L) Lam), taro (Colocasia esculenta var esculenta ( L ) Schott), giant taro (Alocasia macrorrhiza (L) G Don) and giant swamp taro (Cyrtosperma chamissonis (Schott) Merr) was studied. Rice trypsin inhibitor (TI) occurred only in the germ, so it is absent from white rice. Taro, giant taro and giant swamp taro (but not rice or sweet potato) showed an initial large increase (one-to tenfold) in the amount of TI present on heating at about 80°C. The heat release mechanism, which was accompanied by a change to a rubbery texture in the food, amounted to a breakdown of the cellular structure making TI available for extraction. Such heat release of TI would cause partially cooked food to be deleterious for human consumption. Brown rice, sweet potato, taro and giant swamp taro contained moderate amounts of TI, which was fully inactivated when the boiled or baked food was soft enough to eat. Giant taro, however, contained 10-100 times as much TI (which in this case also inhibited chymotrypsin) as the other foods, and a boiling time of at least 30 min was needed for its inactivation.

19F NMR has been used to show that changes in NaCl concentration, as well as the presence of lysine or arginine, affect the equilibrium distribution of the synthetic anthracycline 2‐fluoro‐4‐demethoxydaunomycin (2FD) between binding sites on d(G‐C)5 and d(A‐T)5 in a 1:1:1 molar aqueous system: 2FD/d(G‐C)5/d(A‐T)5. Varying the pH between 6.2 and 7.7 had no effect. NaCl concentrations below 0.1 M led to a d(G‐C)5 preference while above 0.1 M a preference for d(A‐T)5 was observed. At comparable solute concentrations, use of either lysine or arginine resulted in a significant drug preference for d(G‐C)5 compared to systems containing only NaCl.