Product Overview
Background
Catalase is present in the peroxisomes of nearly all aerobic cells and serves to protect the cell from the toxic effects of hydrogen peroxide by catalyzing the decomposition of H2O2 (1,2). The mechanism of catalysis is not fully elucidated, but the overall reaction is as follows:2H2O2 —> 2H20 + O2Catalase has one of the highest catalytic activities reported, near the diffusion-controlled limit. Catalases are tetramers of four identical subunits (220 to 350 kD), each with a heme prosthetic group at the catalytic center. Eukaryotic catalases bind NADPH, which helps to stabilize the enzyme (3).In humans, the highest levels of catalase are found in the liver, kidney, and erythrocytes, where it is believed to account for the majority of hydrogen peroxide decomposition. Studies in a mouse model system have demonstrated the importance of catalase in preventing methemoglobin formation in erythrocytes (4). Catalase activity can be directly monitored in the ultraviolet region (7), however the UV assay is subject to interference due to absorption by protein and other components in biological samples.
Assay Principle
This colorimetric, cuvette based catalase assay involves two steps. Since the rate of dismutation of hydrogen peroxide to water and oxygen is proportional to the concentration of catalase, samples are first incubated with a known amount of hydrogen peroxide. The remaining hydrogen peroxide, following a fixed incubation period, is then determined by the oxidative coupling reaction of 4-aminophenazone (4-aminoantipyrene, AAP) and 3,5-dichloro-2-hydroxy-benzenesulfonic acid (DHBS) in the presence of H2O2 and catalyzed by horseradish peroxidase (6). The resulting quinoneimine dye is measured at 520nm.Notes: Catalase is very unstable at high dilution and should be kept cold and assayed within 30-60 minutes after dilution. Whole blood samples may be stored at 4°C for up to two weeks but it is recommended that samples be stored at –70°C for long-term storage. Red blood cell lysates, undiluted, are stable for 5 days at 4°C. Long term storage should be at –70°C.
References1. Deisseroth, A. & Dounce, A.L., Physiol. Rev. 50, 319-375 (1970).2. Zamocky, M. & Koller, F. Prog. Biophys. Mol. Biol. 72, 19-66 (1999).3. Kirkman, H.N., et al., , J. Biol. Chem. 262, 660-666 (1987).4. Wakimoto, M., et al., Acta Med. Okayama 52, 233-237 (1998).5. Aebi, H. Methods Enzymol 105, 121-126 (1984).6. Fossati, P., et.al. Clin. Chem. 26, 227-231 (1980).
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因为声的多普勒效应，用专用仪器在空气里测频率似乎变得不可靠。 最简单直接的方法，用频率特性仪，接换能器正负极测量读数 或者拿一片超声波振子接受对方发射的超声波进行放大后，输入到整形电路，再输入到计数器，就可以测量频率了
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别告诉我计数的方法用数，我今天早上数了0.4g的微丸，近1000粒，快成熊猫，差点被送动物园了。也别告诉我测微丸的粒径用尺子量，我可是想着把它们排成一条线（增加准确度，可以避免忽略小粒子）再量，可是，这些小粒子不像《花园宝宝》里的小点点们那样听话，他们不爱排队。
各位老师是否还有什么高招？小的在这请教了。
1、同样的测量条件下，如测量相对几何位置相同，放射源相同，放射性测量计数率扣除本底后与活度在统计误差内成正比；
2、同样活度不同核素放射源，在其它条件相同的情况下放射性测量计数率不一定相同。因为不同核素衰变各能量分支比不同、粒子不同、能量不同，有的衰变子体也有放射性。
3、放射性测量计数率与计数器的探测效率相关。简单认为：活度＝（计数率-本底计数率）/效率。其中效率的标定要与测量条件一致。
如何用IPP软件测量肌纤维的直径？求战友教教，带图的那种。另外如何给特定的细胞计数？
频率，是单位时间内完成周期性变化的次数，是描述周期运动频繁程度的量，常用符号f或ν表示，单位为秒分之一，符号为s。为了纪念德国物理学家赫兹的贡献，人们把频率的单位命名为赫兹，简称"赫"，符号为Hz。每个物体都有由它本身性质决定的与振幅无关的频率，叫做固有频率。频率概念不仅在力学、声学中应用，在电磁学、光学与无线电技术中也常使用。
最后，再请问磷32的危害性有多大？
能不能用kappa检验，我看了论坛上的帖子，好像是不行的。但是看到一篇文章，计数资料却用了kappa检验，请问能否这样使用，如果能的话，应该用什么软件，怎么计算。谢谢
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