The effect of water vapour on oxidation was studied with hot-pressed silicon nitride containing both yttria and alumina as sintering aids in wet air flow with 10, 20, 30, and 40vo1% H20 at 1300°C for 10Oh. The oxidation kinetics were determined in a wet air flow with 20vo1% H20 and in a dry air flow at 1300 °C for oxidation times up to 360h. The water vapour in the atmosphere slightly influenced the oxidation and accelerated the reaction, and the weight gained on oxidation in a wet atmosphere had an increasing tendency with increasing water vapour content. The oxidation proceeded in a diffusion-controlled manner in both wet and dry atmospheres. The values of weight gained in wet oxidation varied to a greater degree than in dry oxidation. Water vapour had a strong effect on the devitrification of the amorphous oxide. This process was presumed to promote the rate of oxidation more than in dry atmosphere. The water vapour also had a strong roughening effect on the surface oxide layer grown during oxidation. The flexural strength at room temperature was degraded by oxidation in a wet atmosphere and it is presumed to be degraded by wet oxidation slightly and consecutively with time.
The primary structure of the deteriorated recombinant human basic fibroblast growth factor (rhbFGF) was determined by ultra-performance liquid chromatography and electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC/ESI-QTOF-MS) with in-source collision-induced dissociation (CID). The rhbFGFs before and after treatment with hydrogen peroxide (H(2)O(2)) were separated using an ACQUITY UPLC BEH300 C18 column (1.7 microm, 150 mm x 2.1 mm i.d.) with a gradient elution of a mixture of water/acetonitrile containing 0.1% formic acid. The separated proteins were then detected by a SYNAPT High Definition Mass Spectrometry system (SYNAPT-MS). Two methionine (Met) residues in the rhbFGF structure were oxidized to Met-sulfoxide (Met-O) in 0.03% H(2)O(2) at pH 2.0. As the result, three peaks, except for the peak of rhbFGF, appeared on the chromatogram. The three proteins corresponding to each peak were estimated as the denatured rhbFGFs including the Met-O residue(s) with TOF-MS. Furthermore, the position of the Met-O residue(s) was efficiently identified by UPLC/ESI-QTOF-MS using the in-source CID technique. The proposed method seems to be very useful for the structural elucidation of proteins, because the oxidized Met residues in rhbFGF were easily and rapidly identified.
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