微藻光合作用制氢——能源危机的最终出路?

微藻光合作用制氢是解决能源短缺问题的有效途径.本文介绍了微藻光合作用制氢的机理,包括蓝藻固氮酶和可逆氢酶产氢以及绿藻可逆氢酶产氢的机理.在分析光合制氢限制因素的基础上,指出筛选和构建高效放氢藻株是制氢的有效途径.然后介绍了“直接生物光解”、固氮酶放氢和“间接生物光解”等制氢方式.利用绿藻“间接生物光解”水制氢是一种最有发展潜力的制氢方式.本文最后展望了微藻光合制氢的前景.     

Iron loaded ferritin secretion and inhibition by CI-976 in Aedes aegypti larval cells

Ferritin is a multimer of 24 subunits of heavy and light chains. In mammals, iron taken into cells is stored in ferritin or incorporated into iron-containing proteins. Very little ferritin is found circulating in mammalian serum; most is retained in the cytoplasm. Female mosquitoes, such as Aedes aegypti (yellow fever mosquito, Diptera), require a blood meal for oogenesis. Mosquitoes receive a potentially toxic level of iron in the blood meal which must be processed and stored. We demonstrate by ⁵⁹Fe pulse-chase experiments that cultured A. aegypti larval CCL-125 cells take up iron from culture media and store it in ferritin found mainly in the membrane fraction and secrete iron-loaded ferritin. We observe that in these larval cells ferritin co-localizes with ceramide-containing membranes in the absence of iron. With iron treatment, ferritin is found associated with ceramide-containing membranes as well as in cytoplasmic non-ceramide vesicles. Treatment of CCL-125 cells with iron and CI-976, an inhibitor of lysophospholipid acyl transferases, disrupts ferritin secretion with a concomitant decrease in cell viability. Interfering with ferritin secretion may limit the ability of mosquitoes to adjust to the high iron load of the blood meal and decrease iron delivery to the ovaries reducing egg numbers.     

Differences in specificity and catalytic efficiency between allozymes of esterase-4 from Drosophila mojavensis

A more than 10-fold difference in the specificity and catalytic efficiency for 1-naphthyl esters was measured between two allozymes of esterase-4 from Drosophila mojavensis. This difference is mainly caused by a difference in the affinity for the 1-naphthyl esters. The amino acid compositions of the allozymes are not significantly different, which means that the difference in primary structure is small. Small differences in primary structure generally do not result in such a large increase in catalytic efficiency and such a large shift in substrate specificity as was found in the present study.