The effects of red and blue light-emitting diode (LED) lights on the senescence of broccoli (Brassica oleracea L. var. italica) after harvest were investigated. The results showed that irradiation with red LED light was effective in delaying senescence in broccoli after harvest. Under red LED light, the yellowing process was delayed, and ethylene production and reduction of ascorbate (AsA) were suppressed in broccoli after harvest. In contrast, the blue LED light treatment did not significantly affect the senescence process of broccoli after harvest. As the red light is inconvenient for customers in selecting broccoli in the supermarket, we designed a type of modified white LED light. In this modified white LED light, the ratio of blue light was decreased, while the ratio of red light was increased. Under the modified white LED light, AsA reduction in broccoli was slightly delayed on the first and second days after harvest. Moreover, the modulation of AsA reduction by the modified white LED light treatment was highly regulated at the transcriptional level. The up-regulation of the AsA biosynthetic genes (BO-VTC2 and BO-GLDH) and AsA regeneration genes (BO-MDAR1 and BO-MDAR2) contributed to the higher AsA content in the modified white LED light treatment on the first and second days after harvest. The results presented might provide new strategies to improve the nutritional quality of broccoli after harvest.

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The clathrin-induced fusion of liposome membranes, the membrane binding of clathrin, and the conformational states of clathrin were investigated over a wide pH range using large unilamellar and multilamellar vesicles composed of phosphatidylserine (PS), phosphatidylcholine (PC), PS/PC (2:1), PS/PC (1:1), or PS/PC (1:2). The pH profiles of clathrin-induced fusion of all types of liposomes containing PS showed biphasic patterns. Their pH thresholds were found in the pH range of 5-6 and shifted to lower pH values with decrease in the PS content. Similar shifts were observed in the pH range of 5-6 and shifted to lower pH values with decrease in the PS content. Similar shifts were observed in the pH profiles of clathrin binding to these vesicles, but the pH profiles of binding were different from the biphasic fusion patterns. With PC vesicles, only small degrees of fusion and clathrin binding were observed at pH 2-4. The pH dependences of the conformation and hydrophobicity of clathrin were determined by measuring the extent of the blue shift of the fluorescence maximum of 1-anilinonaphthalene-8-sulfonate in the presence of the protein, the fluorescence intensity of N-(1-anilinonaphthyl-4)maleimide bound to the clathrin molecule, the resonance energy transfer from its tryptophan to anilinonaphthyl residues, the partitioning of the protein in Triton X-114 solution, and the hydrophobicity index of clathrin using cis-parinaric acid. These measurements indicated that conformational change and exposure of hydrophobic regions occur below pH 6 and suggested that clathrin may adopt different conformational states in the pH region where it induced membrane fusion.(ABSTRACT TRUNCATED AT 250 WORDS)