Effect of Heating Temperature on Sulfhydryl and disulfide Contents and State of Aromatic Amino Acid Residues in Soybean Protein

The optical isomers of ten kinds of insecticidal 1,3,2-oxazaphospholidine 2-sulfides (OS) and two kinds of 1,3,2-benzodioxaphosphorin 2-sulfides (BS), including the commercial insecticide salithion, were synthesized in high optical purity by using two optically active aryl methyl phosphorochloridothionates (AMPC) as chiral two-step phosphorylating reagents. Their con-figurations were assigned according to the reaction mechanisms and supported by proton NMR information.     

Isolation and Characterization of a Proteolipid in Defatted Soybean Meals

A proteolipid was isolated from the chloroform–methanol (2:1, by vol.) extract of defatted soybean meals by a modified Folch method. The proteolipid gave a yield of 0.05% of the defatted meals, and the ratio of protein and lipid was neary 3:4. The complex gave a single band containing both protein and lipid on polyacrylamide gel electrophoresis. TLC analysis of the lipid moiety showed that the major components were glycolipids and phospholipids. The protein moiety contained more hydrophobic amino acids and less acidic amino acids in comparison with the amino acid composition of soybean globulin. The protein moiety contained two kinds of protein component (I and II) which have molecular weights of 13,000 (I) and 15,000 (II) on SDS-urea polyacrylamide gel electrophoresis, and N-terminal amino acids of alanine (I) and glutamic acid (II). The apoprotein is a new protein and different from the whey proteins or globulins of soybean.     

Synthesis of Oligosaccharides by Growing Culture of Leuconostoc mesenteroides

When Leuconostoc mesenteroides NRRL B-1299 was grown on a medium containing sucrose and lactose, a trisaccharide named ‘Lactsucrose’ (O-β-d-galactopyranosyl- (l→4) -O-α-d-glucopyranosyl- (l→2) -β-d-fructofuranoside) was produced. This sugar was obtained as a crystalline acetyl derivative and its structure was identified by the methods of paper chromatography, paper ionophoresis, hydrolysis with acid or enzymes and periodate oxidation.     

Emulsifying Properties of a Mixture of Peptides Derived from the Enzymatic Hydrolyzates of Bovine Caseins

β-CN(f193–209), a hydrophobic peptide of 17 residues obtained from the chymosin hydrolyzate of β-casein, had little emulsifying activity (EA) at a neutral pH. When mixed with a hydrophilic glycomacropeptide (GMP) derived from κ-casein however, the EA of β-CN(f193-209) increased greatly. The mixing ratio of the peptides affected the EA as well as the adsorption of the peptides to oil droplets. Scanning electron microscopy indicated that the peptide film surrounding the emulsified oil droplets was thick and rough compared to the protein film. An amphipathic structure formed by some interaction between the hydrophilic GMP and the hydrophobic β-CN(f193-209) might contribute to the formation of the thick peptide film and stabilize the emulsified oil.     

Characterization of Plasma Membrane Proteins from Lactating Bovine Mammary Gland

Properties of proteins in the light (<d 1.03 on Ficoll and then <d 1.14 on sucrose) and heavy (d 1.03/1.05 on Ficoll and then <d 1.14 on sucrose) plasma membranes (PM) isolated from lactating bovine mammary gland were investigated. The PMs consisted of 57 ~ 62% of protein and 38 ~ 43% lipid. The lipid/protein ratio was 0.77 in the light PM and higher than 0.61 of the heavy PM. However, no appreciable differences were found between the light and heavy PMs with respect to polypeptide, amino acid, and carbohydrate compositions. The protein moiety contained approximate 5 ~ 6% carbohydrate: fucose 8 ~ 9, mannose 11 ~ 12, galactose 16, N-acetylglucosamine 32,N-acetylgalactosamine 12 ~ 15, and sialic acid 17~20 mol%. PM protein was high in the content of aspartic acid, glutamic acid, and leucine and low in proline, cystine, methionine, and histidine. On double immunodiffusion both PMs formed precipitin lines against milk fat globule membrane (MFGM) antiserum. Electrophoretic analysis on sodium dodecyl sulfate-polyacrylamide gel revealed the presence of many minor polypeptides and three major glycopeptides (PAS-I, II, and III) of molecular weights of 115,000, 94,000, and 82,000. The glycoprotein profiles of the PMs were different from those of MFGM, except that PAS-II and -III of PM corresponded to PAS-3 and -4 of MFGM, respectively.     

Isolation and Partial Characterization of Heat-denatured Products of Soybean 11S Globulin and Their Analysis by Electrophoresis

Heat denaturation of soybean 11S globulin was examined at 70° and 100°C in phosphate buffer (pH 7.6), at 0.01 and 0.5 ionic strength. Gel electrophoresis (Davis system) indicated that heat-denatured soybean 11S globulin contained two major components (buffer-soluble form). But they were not identified at 70°C-0.5 ionic strength. Gel filtration followed by SDS-gel electrophoresis showed that the major components were composed of a monomer and at least three of kinds of oligomers containing only an acidic subunit. Gel filtration of the precipitate formed at 100°C at 0.5 ionic strength gave two peaks. SDS-gel electrophoresis indicated that the first peak contained aggregates of highly polymerized subunits, and the second peak contained a monomer of basic subunit and seven kinds of oligomers with various proportions of basic subunits to an acidic subunit.     

Quenching Effect of Tocopherols on the Methyl Linoleate Photooxidation and Their Oxidation Products

The quenching effect of α-, γ- and δ-tocopherols on the methylene blue sensitized photo- oxidation of methyl linoleate was investigated, and the ¹O₂. quenching ability of tocopherols was determined. The ¹O₂ quenching rate constants for α-, γ- and δ-tocopherols in ethanol were estimated to be 2.6 × 10⁸ m^?1 sec^?1, 1.8 × 10⁸ m^?1 sec^?1 and 1.0 × 10⁸ m^?1 sec^?1, respectively. And the rate constants for the chemical reaction between each tocopherol and ¹O₂ were 6.6 × 10⁶ m^?1 sec^?1, 2.6 × 10⁶ m^?1 sec^?1 and 0.7 × 10⁶ m^?1 sec^?1 for α-, γ- and δ-tocopherols, respectively. The results show that α-tocopherol is the most effective compound toward ¹O₂ among the three tocopherols. The photooxidation of each tocopherol produced two peroxides which, after chemical reduction, were identified to be tocopherol hydroquinone by gas chromatography-mass spectrometry analysis. The photooxidation mechanism of these tocopherols was assumed to be different from that of autoxidation.     

Composition of Acid-sensitive Fraction in Soybean Proteins

An acid-sensitive fraction (ASF) was prepared from defatted soybean meals by two procedures. ASF1 was prepared by precipitation at pH 4.5 followed by removal of 1 m NaCl-soluble materials from the precipitate. ASF2 was prepared by precipitation in solution containing 1 m NaCl at pH 4.5. The protein components of the two fractions were analyzed by gel electrophoresis in a dissociating-buffer system and found to contain β-conglycinin, glycinin and whey proteins. In addition to these, several other bands appeared.

Appreciable amounts of lipid (8.2% in ASF1 and 8.8% in ASF2) were also found in the fractions. They were separated by column chromatography and thin-layer chromatography. Glycolipids were the major components of the lipids. Both glycolipid and phospholipid fractions contained slower-moving materials on thin-layer chromatography.     

Comparison of Four Distinct Idiotypes of Monoclonal Antibodies against Hen’s Egg Ovomucoid

Two monoclonal antibodies (mAb 41B3 and mAb 51B3), directed against hen’s egg ovomucoid (OM) and different from those we previously reported (mAb 23E5 and mAb 32A8), were prepared and purified. A competitive radioimmunoassay using ¹²⁵I-labeled OM showed that both mAb 41B3 and mAb 51B3 could bind all three homologous domains (domains I (DI), II (DII) and III (Dili)) of OM and that they reacted most efficiently with Dill. To analyze the paratope specificities of these four mAbs, a sandwich assay and a competitive radioimmunoassay were done. Only the pair mAb 41B3 and mAb 51B3 could not simultaneously bind the OM or domains in the sandwich assay. Only mAb 41B3 inhibited the binding of mAb 51B3 to antigens and vice versa in the competitive radioimmunoassay. These results suggest that mAb 41B3 and mAb 51B3 recognized a closely related site distinct from the epitopes for mAb 23E5 or mAb 32A8. These mAbs may be useful for general studies on epitopes of protein antigens as well as for analyses of the antigenic determinants of OM.     

Lipid Composition of Plasma Membranes Isolated from Lactating Bovine Mammary Gland

The light and heavy plasma membranes (PM) isolated from lactating bovine mammary glands contained 38~43% lipid of which 41~44% was phospholipid and 47~52% neutral lipid. The contents of phospholipid and neutral lipid were somewhat higher in the light PM than in the heavy PM. Cholesterol was contained 55 ~60% of neutral lipid and the ratio of cholesterol to phospholipid was 0.64 to 0.69. Phospholipid was composed of sphingomyelin (Sph) 29~38%, phosphatidylcholine (PC) 27~35%, phosphatidylethanolamine (PE) 16~20%, phosphatidylserine 10%, and phosphatidylinositol 6~7%. The content of Sph was higher in the heavy PM than in the light PM, while the values of PC and PE were opposite. The major fatty acids of lipid components were palmitic acid, stearic acid, and oleic acid and those of Sph were palmitic acid, stearic acid, C23:0 and 24:0. The fatty acid composition of individual lipid classes differed significantly from each other but were similar between the light and heavy PMs. Tetracosapentaenoic acid (C24:5) was the major fatty acid of the diacylglycerol fraction. The results indicated that the lipid composition, especially phospholipid components, of bovine mammary gland PMs was different from those of milk fat globule membranes which is derived from the PM of mammary secretory cells.