细胞色素c在Eastman AQ聚离子薄膜电极上的直接电化学

将聚磺酸酯Eastman AQ38(AQ)与细胞色素c (Cyt c)的混合水分散系涂布于热解石墨电极表面,晾干后可形成Cyt c-AQ薄膜.在pH 7.6的缓冲溶液中,Cyt c-AQ薄膜电极表现出良好的直接电化学行为,电化学活性中心为血红素Fe(Ⅲ)/血红素Fe(Ⅱ)氧化还原对. Cyt c-AQ薄膜在-0.05V(vs SCE)处的一对可逆的循环伏安还原氧化峰随浸泡时间的延长而逐渐降低,而在-0.40V的另一对峰逐渐增高,表明Cyt c在AQ薄膜中很可能经历了由其原始构象向另一种新构象的转变,后者在AQ薄膜中十分稳定.对其伏安行为进行了较详尽的研究,并估计了体系的电化学参数,如表观异相电子传递速率常数ks和式量电位E°′等. Cyt c-AQ薄膜电极可催化还原溶液中的氧.     

低温敏感不育水稻育性敏感期细胞色素氧化酶活性

以常规品种特青作对照，分别测定了特青、低温敏感核不育材料Ｎ１０Ｓ、Ｎ１３Ｓ，在花粉母细胞形成期和花粉母细胞减数分裂期不同育性条件下的叶片和幼穗花药的细胞色素氧化酶的活性，并进行了统计学分析———两因素方差分析（Ｆ检验）及平均数的Ｄｕｎｃａｎ多重比较．结果表明，在育性敏感的２个时期，Ｎ１０Ｓ和Ｎ１３Ｓ不育株幼穗花药的细胞色素氧化酶的活性极显著低于可育株细胞色素氧化酶的活性，Ｎ１０Ｓ在育性敏感的２个时期分别为７２．０％和６３．２％，Ｎ１３Ｓ则分别为７２．１％和６７．７％．这就使得不育株花药中能量供应短缺，造成物质合成等许多生命活动衰减，最终导致不育     

Mitochondrial cytochrome b sequences variation of Protura and molecular systematics of Apterygota

Mitochondrial cytochrome b genes of about 450 bp fragments from 3 proturan species, 5 collembolan species and 2 dipluran species have been sequenced. The number of nucleotide substitutions and Kimura 2-parameter distances have also been calculated, and a series of molecular phylogenetic trees reconstructed by using parsimony and distance methods. The proturan, collembolan and dipluran species have evolved monophyletic groups. The results suggest that Protura and Collembola are sister groups, while Diplura is more or less demonstrating a closer phylogenetic relationship to the pterygotan insects. The phylogeny and their systematic position of protura and other groups are also discussed.     

Estimated evolutionary tempo of East Asian gobionid fishes (Teleostei: Cyprinidae) from mitochondrial DNA sequence data

The rapid development of molecular phylogenetic analysis has provided a new path to investigate the tempo of evolution.In this work,a rather complete molecular phylogeny of the East Asian gobionid fishes was constructed based on mtDNA cytochrome b gene sequences.Molecular clock analysis was then applied to investigate the speciation tempo of this group.The phylogenetic analysis revealed four major groups that were in agreement with previous studies.Lineage numbers plotted over time indicate that gobionid li...     

Cytochrome c release and endoplasmic reticulum stress are involved in caspase-dependent apoptosis induced by G418

G418 is used extensively in transfection experiments to select eukaryotic cells that have acquired neomycin resistance genes, but the mechanism is still elusive. To investigate this, we treated normal rat kidney cells with G418 for 3 days and found that the cells presented typical apoptotic features such as cell shrinkage, nuclear fragmentation, and caspase-3 activation. However, there was no low-molecular DNA ladder. The pan caspase inhibitor z-VAD-fmk completely inhibited this type of apoptosis, suggesting a caspase-dependent mechanism. Caspase cascades in apoptosis induced by G418 were initiated by at least two pathways: the release of cytochrome c from mitochondria, which was observed under confocal microscopy, and endoplasmic reticulum stress, demonstrated by the increase in Ca²⁺ concentration and the cleavage of m-calpain and procaspase-12. Both pathways activated caspase-9. Inhibition of caspase-9 activity by z-LEHD-fmk prevented most of the cells from apoptosis, and E-64d, an inhibitor of calpain accentuated this block. The cleavage of casapse-9 and caspase-12 was blocked only by simultaneous application of z-VAD-fmk and E-64d, but not by either alone. E-64d did not prevent the release of cytochrome c. These results indicated that these two pathways were independent of each other. Received 1 April 2004; received after revision 21 April 2004; accepted 26 May 2004     

pH值对细胞色素C的反胶团萃取的影响

以ＡＯＴ／异辛烷反胶团萃取不同ｐＨ值的猪心提取液中的ｃｙｔＣ。结果表明：ｐＨ４～１０范围内有不同的萃取效果，其中ｐＨ８～９的萃取率达到６０％～７５％。萃取水相中细胞色素Ｃ的特征吸收峰值下降或消失，萃取有机相的吸收光谱与提取原液的吸收光谱相似，并具有相同的吸收峰。说明在ｐＨ４～１０之间均能用ＡＯＴ／异辛烷萃取分离细胞色素Ｃ。     

Interaction of BW755C,a potent inhibitor of lipoxygenase and cyclo-oxygenase,with mitochondrial cytochrome oxidase

Summary The interaction between BW755C (3-amino-1-[m-(trifluoromethyl)phenyl]-2-pyrazoline), a potent inhibitor of both lipoxygenase and cyclo-oxygenase, and respiratory chain in mitochondria and electron transport particles (ETP) from rat livers was examined. BW755C accelerated the oxygen uptake by mitochondria without the addition of substrate for the respiratory chain. Spectrophotometric study revealed that BW755C was quickly oxidized by cytochrome oxidase in mitochondria to a compound possessing an absorption maximum at 524 nm. p-Phenylenediamine (p-diaminobenzene, PPDA), which, like BW755C, serves as an electron donor to cytoschrome oxidase, was shown to inhibit the generation of active oxygen in macrophages; the inhibition was stronger than that of BW755C. These results strongly suggest that the oxidative conversion of BW755C by mitochondrial cytochrome oxidase is associated with its potentially inhibitory action on the active oxygen-generating system in phagocytes.The authors are indebted to Dr M. Hori, Gifu College of Pharmacy and to Dr Y. Orii, Kyoto University for their kind supplies of BW755C and pure cytochrome oxidase, respectively.