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Polyphenol oxidase from wheat bran is a serpin

100%

Yamasaki Y. , Konno H. , Noda K.

2008

tom 55

nr 2

325-328

Polyphenol oxidase (PPO; EC 1.10.3.2) was isolated from wheat bran by a procedure that included ammonium sulfate fractionation, batch adsorption by DEAE-cellulofine, CM-cellulofine column chromatography, DEAE-cellulofine column chromatography, preparative isoelectric focusing, adsorption on the membrane of a Vivapure Q Maxi H spin column, and heat treatment. These procedures led to 150-fold purification with 4.2% recovery. The PPO was homogeneous by SDS/PAGE. The relative molecular weight of the PPO was estimated to be 37000 based on its mobility in SDS/PAGE. The isoelectric point of the PPO was 4.4. The Kmvalues of the PPO for caffeic acid, chlorogenic acid, pyrocatechol, 4-methyl catechol and l-DOPA as substrates were 0.077, 0.198, 1.176, 1.667 and 4.545 mM. The PPO was strongly inhibited by tropolone. The Kivalue for tropolone is 2.2 × 10–7M. The sequence of the 15 N-terminal amino-acid residues was determined to be ATDVRLSIAHQTRFA, which was identical to those of serpin from Triticum aestivum and protein Z from Hordeum vulgare. The PPO strongly inhibited the activity of trypsin, which is an enzyme of serine proteases; 50% inhibition was observed with 1.5 × 10–7M PPO. The Kivalue for PPO is 2.3 × 10–8M. The wheat bran PPO should be a very important protein for protecting wheat against disease, virus, insect and herbivore damages by both the activities of PPO and protease inhibitor.

Development of manufacturing process of wrought magnesium alloy sheets by twin roll casting

75%

Watari H. , Paisarn R. , Haga T. , Noda K. , Davey K. , Koga N.

tom Vol. 20, nr 1-2

515-518

Purpose: The purpose of the work is to development of a strip casting technology for manufacturing magnesium alloy sheets. The aim of the work is to establish a manufacturing process and technology to facilitate the economical manufacture of high-strength magnesium sheet alloys. Design/methodology/approach: A horizontal type twin roll caster was used to manufacture magnesium alloy sheets. Pair of copper alloy roll, pure copper roll and steel roll was used for the horizontal type twin roll caster. The diameter of the rolls was 300 mm and the width of rolls was 100 and 150 mm. Findings: The magnesium alloy sheets could be successfuly manufactured by the horizontal twin roll caster. The product sheet thickness in the present experiment was 2.0 to 5.0 mm. The equiaxed microstructure was observed in cast magnesium alloys when a pair of copper and copper alloy rolls were used. The mean grain size of the cast magnesium alloys strip was from 30 to 60 micrometers. After hot rolling process, the grain size was reduced to about 10 micrometers. The obtained magnesium alloy sheet indicated a good plastic formability by a warm-drawing test. Research limitations/implications: The superheat in the experiment was between 15 and 30 degrees centigrade, also an appropriate hot rolling temperature was 250 degrees centigrade for AZ31, AZ61 and AM60, 300 degrees centigrade for AZ91. Practical implications: The proposed manufacturing process was effective from the view point of economical manufacturing process as well as of formation of rapid solidification microstructures. Introducing the twin roll casting technology enable to manufacture magnesium sheet alloys with high aluminium contents, such as AZ61, AM60 and AZ91. Originality/value: AZ31, AM60, AZ61 and AZ91 wrought magnesium alloy sheets can be manufactured economically by twin roll casting. These cast sheet can be hot rolled and the proposed manufacturing process enables manufacturer to manufacture thin magnesium alloy sheets with high aluminium contents such as AM60, AZ61 and AZ91.