Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and the...Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.展开更多
Hygroscopicity-resistance of an α-starch based composite binder for dry sand molds (cores) has been studiedexperimentally and theoretically. Focus is placed on the relationship between the hardening structure andhumi...Hygroscopicity-resistance of an α-starch based composite binder for dry sand molds (cores) has been studiedexperimentally and theoretically. Focus is placed on the relationship between the hardening structure andhumidity-resistance of the composite binder. The results show that the α-starch composite binder has goodhumidity-resistance due to its special complex structure. SEM observations illustrate that the composite binder consists ofreticular matrix and a ball- or lump-shaped reinforcement phase, and the specific property of the binding membrane withheterogeneous structure is affected by humidity to a small extent. Based on the analyses on the interplays of differentingredients in the binder at hardening, the structure model and hygroscopicity-resistant mechanisms of the hardeningcomposite binder were further proposed. Moreover, the reasons for good humidity-resistance of the composite binderbonded sand are well explained by the humidity-resistant mechanisms.展开更多
大环糊精(large ring cyclodextrin,LR-CD)是由9个至数百个吡喃葡萄糖单元组成的环状α-1,4-葡聚糖,主要通过环糊精葡萄糖基转移酶或4-α-糖基转移酶的环化作用使直链淀粉发生分子内转糖基作用得到。与常见α-、β-、γ-环糊精(cyclodex...大环糊精(large ring cyclodextrin,LR-CD)是由9个至数百个吡喃葡萄糖单元组成的环状α-1,4-葡聚糖,主要通过环糊精葡萄糖基转移酶或4-α-糖基转移酶的环化作用使直链淀粉发生分子内转糖基作用得到。与常见α-、β-、γ-环糊精(cyclodextrin,CD)相比,LR-CD的空腔尺寸更大,表现出独有的结构和理化特性,这些性质使LR-CD在食品、医药、生物等领域展现出巨大的应用潜力。然而,LR-CD的制备成本高,产率较低,并且缺乏有效的分离纯化方法,因此目前还未实现工业化生产与应用。本文分别从优化底物、设计基于模板诱导的新反应路径、酶分子改造及产物的分离纯化等方面综述酶法制备LR-CD的研究近况与挑战,为LR-CD的工业化生产和应用提供参考。展开更多
【目的】淀粉降解与水稻浆片膨大和颖花开放过程密切相关,探究α-淀粉酶基因在颖花开放过程中的作用,为杂交水稻制种效率及产量的提高提供理论依据。【方法】在水稻扬花时,利用稀释碱性品红溶液进行离体穗子吸水试验,观察碱性品红在颖...【目的】淀粉降解与水稻浆片膨大和颖花开放过程密切相关,探究α-淀粉酶基因在颖花开放过程中的作用,为杂交水稻制种效率及产量的提高提供理论依据。【方法】在水稻扬花时,利用稀释碱性品红溶液进行离体穗子吸水试验,观察碱性品红在颖花中残留的组织,通过碘-碘化钾染色法确定11—14期(依据雄蕊发育分期)淀粉粒的分布变化,并通过RT-PCR、RT-qPCR和GUS报告基因检测多个α-淀粉酶基因在此期间的时空表达模式。【结果】水稻颖花开放前,内外稃片通过相互嵌合的钩合槽(marginal tissues of palea,mtp)将浆片和雌雄蕊封闭在内。当颖花开放时,浆片快速膨大,使得内外稃片的钩合点松开。扬花期间,离体穗子在稀释碱性品红溶液中吸水后,碱性品红染料主要残留在内外稃片钩合槽和浆片相连处组织以及花丝中。碘染试验显示,在12期(颖花开放前),淀粉粒主要分布在雄蕊和内外稃片钩合槽,浆片中也有少量淀粉粒,在13—14期(颖花开放中),内外稃片钩合槽和浆片中的淀粉粒均降解。RT-PCR分析发现OsRAmy2A和OsRAmy3D的表达量从12期开始上升,至13—14期表达量显著增强,到受精后1 d(1 day after pollination,DAP1)表达量又明显下降,OsRAmy3E和OsRAmy3F在此过程中持续表达,OsRAmy3F表达量弱于OsRAmy3E。RT-qPCR分析显示,在11—14期,OsRAmy2A表达量变化最显著,其次是OsRAmy3A和OsRAmy3E,OsRAmy3F的表达量变化幅度最不明显,OsRAmy2A和OsRAmy3A在13—14期表达量显著增加,而OsRAmy3E和OsRAmy3F在不同时期均表达,在13—14期表达量略有升高。在12期,OsRAmy2A主要在内外稃以及内外稃片钩合槽上表达,在13—14期主要在内外稃片钩合槽、浆片以及花丝上表达。【结论】水稻颖花开放过程中淀粉粒在mtp和浆片中明显降解,与OsRAmy2A、OsRAmy3D等α-淀粉酶基因时空表达模式相对应,可能与水稻浆片膨大导致颖花开放过程密切相关。展开更多
基金This work was supported by the China Postdoctoral Science Foundation(China Fund[1998]6)that was entitled“Synthesis of Modified Starch Binder and Its Application in Foundry”.Authors would like to thank academician Jinzong YANG and lecturer Hua ZHANG for the kind analyses and discussions.
文摘Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.
文摘Hygroscopicity-resistance of an α-starch based composite binder for dry sand molds (cores) has been studiedexperimentally and theoretically. Focus is placed on the relationship between the hardening structure andhumidity-resistance of the composite binder. The results show that the α-starch composite binder has goodhumidity-resistance due to its special complex structure. SEM observations illustrate that the composite binder consists ofreticular matrix and a ball- or lump-shaped reinforcement phase, and the specific property of the binding membrane withheterogeneous structure is affected by humidity to a small extent. Based on the analyses on the interplays of differentingredients in the binder at hardening, the structure model and hygroscopicity-resistant mechanisms of the hardeningcomposite binder were further proposed. Moreover, the reasons for good humidity-resistance of the composite binderbonded sand are well explained by the humidity-resistant mechanisms.
文摘大环糊精(large ring cyclodextrin,LR-CD)是由9个至数百个吡喃葡萄糖单元组成的环状α-1,4-葡聚糖,主要通过环糊精葡萄糖基转移酶或4-α-糖基转移酶的环化作用使直链淀粉发生分子内转糖基作用得到。与常见α-、β-、γ-环糊精(cyclodextrin,CD)相比,LR-CD的空腔尺寸更大,表现出独有的结构和理化特性,这些性质使LR-CD在食品、医药、生物等领域展现出巨大的应用潜力。然而,LR-CD的制备成本高,产率较低,并且缺乏有效的分离纯化方法,因此目前还未实现工业化生产与应用。本文分别从优化底物、设计基于模板诱导的新反应路径、酶分子改造及产物的分离纯化等方面综述酶法制备LR-CD的研究近况与挑战,为LR-CD的工业化生产和应用提供参考。
文摘【目的】淀粉降解与水稻浆片膨大和颖花开放过程密切相关,探究α-淀粉酶基因在颖花开放过程中的作用,为杂交水稻制种效率及产量的提高提供理论依据。【方法】在水稻扬花时,利用稀释碱性品红溶液进行离体穗子吸水试验,观察碱性品红在颖花中残留的组织,通过碘-碘化钾染色法确定11—14期(依据雄蕊发育分期)淀粉粒的分布变化,并通过RT-PCR、RT-qPCR和GUS报告基因检测多个α-淀粉酶基因在此期间的时空表达模式。【结果】水稻颖花开放前,内外稃片通过相互嵌合的钩合槽(marginal tissues of palea,mtp)将浆片和雌雄蕊封闭在内。当颖花开放时,浆片快速膨大,使得内外稃片的钩合点松开。扬花期间,离体穗子在稀释碱性品红溶液中吸水后,碱性品红染料主要残留在内外稃片钩合槽和浆片相连处组织以及花丝中。碘染试验显示,在12期(颖花开放前),淀粉粒主要分布在雄蕊和内外稃片钩合槽,浆片中也有少量淀粉粒,在13—14期(颖花开放中),内外稃片钩合槽和浆片中的淀粉粒均降解。RT-PCR分析发现OsRAmy2A和OsRAmy3D的表达量从12期开始上升,至13—14期表达量显著增强,到受精后1 d(1 day after pollination,DAP1)表达量又明显下降,OsRAmy3E和OsRAmy3F在此过程中持续表达,OsRAmy3F表达量弱于OsRAmy3E。RT-qPCR分析显示,在11—14期,OsRAmy2A表达量变化最显著,其次是OsRAmy3A和OsRAmy3E,OsRAmy3F的表达量变化幅度最不明显,OsRAmy2A和OsRAmy3A在13—14期表达量显著增加,而OsRAmy3E和OsRAmy3F在不同时期均表达,在13—14期表达量略有升高。在12期,OsRAmy2A主要在内外稃以及内外稃片钩合槽上表达,在13—14期主要在内外稃片钩合槽、浆片以及花丝上表达。【结论】水稻颖花开放过程中淀粉粒在mtp和浆片中明显降解,与OsRAmy2A、OsRAmy3D等α-淀粉酶基因时空表达模式相对应,可能与水稻浆片膨大导致颖花开放过程密切相关。
