该文研究了利用一种新型羧肽酶M32制备低苦味豌豆低聚肽的方法并进行了功能特性分析。结果表明羧肽酶M32酶解的最适条件为60℃,pH 7,酶解时间2 h,底物质量浓度60 g/L;羧肽酶M32结合碱性蛋白酶制备的豌豆低聚肽(pea protein isolate hydr...该文研究了利用一种新型羧肽酶M32制备低苦味豌豆低聚肽的方法并进行了功能特性分析。结果表明羧肽酶M32酶解的最适条件为60℃,pH 7,酶解时间2 h,底物质量浓度60 g/L;羧肽酶M32结合碱性蛋白酶制备的豌豆低聚肽(pea protein isolate hydrolysed by alkaline protease and carboxypeptidase M32,PPIACP)的溶解性和水解度分别为80.6%和15.4%,与碱性蛋白酶单酶制备的豌豆低聚肽(pea protein isolate hydrolysed by alkaline protease,PPIA)相比,分别提高了37.4%和33.4%;PPIACP中分子质量在0.2~1 kDa的短肽与PPIA相比显著增加(P<0.05),增加了36.2%;鲜味氨基酸提高了3.8%,苦味氨基酸His、Arg、Val、Leu含量显著增加了17.4%(P<0.05),表明羧肽酶M32可将苦味肽C端的疏水性氨基酸(多为苦味氨基酸)释放出来,使其呈游离状态,降低苦味;电子舌结果显示,苦味值由5.09变为3.93,降低了22.8%;鲜味由18.9变为21.7,提高了20.9%;DPPH自由基清除率、•OH清除率分别为98%和90%。综上所述,结合羧肽酶M32的双酶法可以显著降低豌豆低聚肽的苦味并提高其功能特性,该羧肽酶在植物蛋白生物活性肽制备中具有良好的应用前景。展开更多
Since Baade＇s photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our invest...Since Baade＇s photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our investigation into the nature of the existing evidence. We find that the case for M32 being a satellite of M31 rests upon Hubble Space Telescope （HST） based stellar population studies which have resolved red-giant branch （RGB） and red clump stars in M32 as well as other nearby galaxies. Taken in isolation, this recent evidence could be considered to be conclusive in favour of the existing view. However, the conventional scenario does not explain M32＇s anomalously high central velocity dispersion for a dwarf galaxy （several times that of either NGC 147, NGC 185 or NGC 205） or existing planetary nebula observations （which suggest that M32 is more than twice as distant as M31） and also requires an elaborate physical explanation for M32＇s inferred compactness. Conversely, we find that the case for M32 being a normal galaxy, of the order of three times as distant as M31, is supported by： （1） a central velocity dispersion typical of intermediate galaxies, （2） the published planetary nebula observations, and （3） known scaling relationships for normal early-type galaxies. However, this novel scenario cannot account for the high apparent luminosities of the RGB stars resolved in the M32 direction by HST observations. We are therefore left with two apparently irreconcilable scenarios, only one of which can be correct, but both of which suffer from potentially fatal evidence to the contrary.This suggests that current understanding of some relevant fields is still very far from adequate.展开更多
文摘该文研究了利用一种新型羧肽酶M32制备低苦味豌豆低聚肽的方法并进行了功能特性分析。结果表明羧肽酶M32酶解的最适条件为60℃,pH 7,酶解时间2 h,底物质量浓度60 g/L;羧肽酶M32结合碱性蛋白酶制备的豌豆低聚肽(pea protein isolate hydrolysed by alkaline protease and carboxypeptidase M32,PPIACP)的溶解性和水解度分别为80.6%和15.4%,与碱性蛋白酶单酶制备的豌豆低聚肽(pea protein isolate hydrolysed by alkaline protease,PPIA)相比,分别提高了37.4%和33.4%;PPIACP中分子质量在0.2~1 kDa的短肽与PPIA相比显著增加(P<0.05),增加了36.2%;鲜味氨基酸提高了3.8%,苦味氨基酸His、Arg、Val、Leu含量显著增加了17.4%(P<0.05),表明羧肽酶M32可将苦味肽C端的疏水性氨基酸(多为苦味氨基酸)释放出来,使其呈游离状态,降低苦味;电子舌结果显示,苦味值由5.09变为3.93,降低了22.8%;鲜味由18.9变为21.7,提高了20.9%;DPPH自由基清除率、•OH清除率分别为98%和90%。综上所述,结合羧肽酶M32的双酶法可以显著降低豌豆低聚肽的苦味并提高其功能特性,该羧肽酶在植物蛋白生物活性肽制备中具有良好的应用前景。
文摘Since Baade＇s photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our investigation into the nature of the existing evidence. We find that the case for M32 being a satellite of M31 rests upon Hubble Space Telescope （HST） based stellar population studies which have resolved red-giant branch （RGB） and red clump stars in M32 as well as other nearby galaxies. Taken in isolation, this recent evidence could be considered to be conclusive in favour of the existing view. However, the conventional scenario does not explain M32＇s anomalously high central velocity dispersion for a dwarf galaxy （several times that of either NGC 147, NGC 185 or NGC 205） or existing planetary nebula observations （which suggest that M32 is more than twice as distant as M31） and also requires an elaborate physical explanation for M32＇s inferred compactness. Conversely, we find that the case for M32 being a normal galaxy, of the order of three times as distant as M31, is supported by： （1） a central velocity dispersion typical of intermediate galaxies, （2） the published planetary nebula observations, and （3） known scaling relationships for normal early-type galaxies. However, this novel scenario cannot account for the high apparent luminosities of the RGB stars resolved in the M32 direction by HST observations. We are therefore left with two apparently irreconcilable scenarios, only one of which can be correct, but both of which suffer from potentially fatal evidence to the contrary.This suggests that current understanding of some relevant fields is still very far from adequate.
