Direct sampling gas chromatography used for determining volatiles and, indirectly, the flavor of vegetable otis, has been improved by a capillary column in place of the usual packed columns. Data on two good vegetable oils from a supermarket, and on one of these samples after intentional deterioration, are presented. Use of the capillary column provides a more efficient technique to differentiate between the better oils than did the previously used packed columns.
2-Phenyl-2,1,3-triazoIe-4-carboxaldehyde (I) was first synthesized by von Peohmann (1) who treated the hydrazoxime (II) HC=N-OH C=N-NH-C.HS
HC=NOH(II) with phosphorus pentachloride, or boiled it with acetic anhydride. These methods produced the oxime of (I) in 20 to 25% yields. An alternative procedure was to heat the monoacetate of (II) with dilute sodium carbonate which produced a 50% yield of the oxime of (I).A much more satisfactory method was discovered in 1944 by Hann and Hudson (2), who isolated (I) in connection with the proof of structure of "phenyl-n-
The monomers (subunits) are dissociated reversibly from the protomer or the dimer at pH 11.5-12.0. They may undergo conformational changes before extensively unfolding at pH 12.5. At extreme alkaline pH (pH 13) alkaline degradation may account for the irreversible dissociation. At ionic strength less than 0.01, reversible dissociation into subunits occurs even at mild alkaline or mild acidic pH. In the alkaline region, the dissociation of B3 to B6 conglycinins gives a subunit. In the acidic region both a and ß subunits are dissociated from /3-conglycinin.Dissociation of /3-conglycinin with urea has been found to accompany simultaneously the destruction of internal structure of the protein, which led to the suggestion that the subunits were very compactly and complicatedly folded on the formation of the gross structure (Koshiyama, 1971).However, in the present study the ability of the protein to undergo dissociation at low ionic strength and at physiological pH suggests that the subunits can exist as organized monomers in equilibrium with the trimer and hexamer within soybean seeds. Thus, the dissociation may not require an extensive destruction of the secondary and tertiary structures of the protein.Contrary to a report of Koshiyama (1968) we found that the dissociation at alkaline pH was reversible. The dissociation coincided with the ionization of tyrosine residues in /3-conglycinin. Tyrosine and the electrostatic interactions that are disrupted at alkaline pH due to unionization of e-amino group of lysine (pK = 10.53) and guanidine group of arginine (pK = 12.48) are considered to contribute to the interaction between the subunits. Tyrosine residues are likely to be present in the subunit contact region-therefore, exposed to the media during dissociation-rather than being buried in the interior of the subunits, because their ionization at alkaline pH was not time-dependent (Koshiyama, 1971). In a similar manner, most of the tyrosine residues of conarachin (78%), which ionized with apparent pK of 11.2 at low ionic strength, were proposed to be located at the interfaces of the subunits, stabilizing the quaternary structure of the protein (Yotsuhashi, 1973).
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