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The interaction between a single-chain Fv (sFv) of the monoclonal antibody 3A21 and its antigen, bovine pancreatic ribonuclease A (RNase A), was studied by site-directed mutagenesis of the hypervariable regions and fluorescence polarization analysis. The affinity constants of wild-type sFv and a mutant sFv D31A (Asp31 of heavy chain was replaced by Ala) for RNase A were found to be 2.7 x 10(7) and 4.7 x 10(6) M-1 in PBS at pH 7.2 and 37 degrees C, respectively. While the affinity constant of D31A is not affected by NaCl concentration, that of wild-type sFv is almost the same as that of D31A in the presence of more than 1 M NaCl. These results demonstrate that Asp31 of the heavy chain interacts electrostatically with a positively charged amino acid residue of RNase A.

Lipoxygenase (LOX) is thought to play an important role in the formation of desirable or undesirable flavor and aroma in many plant products. In rice seeds, LOX activity is localized in the bran fraction and LOX-3 is the major isozyme component. We used gas chromatography-mass spectrometry to determine whether the degree of staleness in the flavor of stored brown rice was related to the presence of LOX-3. We found that the amount of hexanal, pentanal, and pentanol in normal raw LOX-3 rice markedly increased during storage at 35 degrees C. That in LOX-3-less rice increased slightly but was a third to a fifth that of normal LOX-3 rice. In cooked rice, the amount of these components from glutinous rice exceeded that in nonglutinous rice, and that in normal LOX-3 rice exceeded that in LOX-3-less rice. These results indicate that the stale flavor production in LOX-3-less rice during storage is less than that in normal LOX-3 rice.

We measured serum sialic acid in oral cancer patients by enzymatic method.The mean serum level of sialic acid in the patients was significantly higher than that in normal volunteers, and the level was proportional to the stage of cancer. In most patients, serum levels of sialic acid returned to normal postoperatively. However, in patients with recurrence or metastasis, the levels rose gradually after surgery.Serum levels of sialic acid were well correlated with those of aracid glycoprotein and ar macroglobulin. In addition, we found that O2- production of neutrophils was inhibited by sialic acid.From these results, the measurement of serum sialic acid in oral cancer seems to be useful to estimate of progress, recurrence and metastasis. It is also suggested that sialic acid has deep connection with neutrophil's function.

Serum sialic acid in patients with acute oral bacterial infections and healthy parsons was measured by enzymatic method. Significant raised levels of serum sialic acid were found in patients with acute infections as compared with healthy persons. Serum levels of sialic acid corresponded with the clinical condition of infections diseases and recovered normally with clinical improvement. Serum concentrations of sialic acid were well correlated with those of C-reactive protein and numbers of white blood cells. In addition, serum sialic acid significantly increased postoperatively.As human serum does not contain free sialic acid and sialic acid almost binds to glycoprotein such as C-reactive protein, acid glycoprotein, and so on, these results suggest that raised levels of serum sialic acid may be caused by the increase of acute phase proteins. Therefore, measurement of serum sialic acid is thought to be useful as a marker which reflects the clinical condition of infections diseases rather than infections themselves.