Research Faculty and Graduate School of Agriculture, Hokkaido University, Kita-ku, Sapporo, Japan.
Cryobiology. 2011 Dec;63(3):157-63. doi: 10.1016/j.cryobiol.2011.06.001. Epub 2011 Aug 27.
Deep supercooling xylem parenchyma cells (XPCs) in Katsura tree contain flavonol glycosides with high supercooling-facilitating capability in solutions containing the ice nucleation bacterium (INB) Erwinia ananas, which is thought to have an important role in deep supercooling of XPCs. The present study, in order to further clarify the roles of these flavonol glycosides in deep supercooling of XPCs, the effects of these supercooling-facilitating (anti-ice nucleating) flavonol glycosides, kaempferol 3-O-β-D-glucopyranoside (K3Glc), kaempferol 7-O-β-D-glucopyranoside (K7Glc) and quercetin 3-O-β-D-glucopyranoside (Q3Glc), in buffered Milli-Q water (BMQW) containing different kinds of ice nucleators, including INB Xanthomonas campestris, silver iodide and phloroglucinol, were examined by a droplet freezing assay. The results showed that all of the flavonol glycosides promoted supercooling in all solutions containing different kinds of ice nucleators, although the magnitudes of supercooling capability of each flavonol glycoside changed in solutions containing different kinds of ice nucleators. On the other hand, these flavonol glycosides exhibited complicated nucleating reactions in BMQW, which did not contain identified ice nucleators but contained only unidentified airborne impurities. Q3Glc exhibited both supercooling-facilitating and ice nucleating capabilities depending on the concentrations in such water. Both K3Glc and K7Glc exhibited only ice nucleation capability in such water. It was also shown by an emulsion freezing assay in BMQW that K3Glc and Q3Glc had no effect on homogeneous ice nucleation temperature, whereas K7Glc increased ice nucleation temperature. The results indicated that each flavonol glycoside affected ice nucleation by very complicated and varied reactions. More studies are necessary to determine the exact roles of these flavonol glycosides in deep supercooling of XPCs in which unidentified heterogeneous ice nucleators may exist.
在含有冰核细菌（INB）菠萝泛菌的溶液中，桂樱木薄壁组织细胞（XPC）中的深层过冷却富含黄酮醇糖苷，具有高的过冷却促进能力，这被认为在 XPC 的深层过冷却中起着重要作用。本研究为了进一步阐明这些黄酮醇糖苷在 XPC 深层过冷却中的作用，在含有不同冰核的缓冲 Milli-Q 水（BMQW）中，通过液滴冻结试验研究了这些过冷却促进（抗冰核）黄酮醇糖苷，山柰酚 3-O-β-D-吡喃葡萄糖苷（K3Glc）、山柰酚 7-O-β-D-吡喃葡萄糖苷（K7Glc）和槲皮素 3-O-β-D-吡喃葡萄糖苷（Q3Glc）对包括 INB 野油菜黄单胞菌、碘化银和间苯三酚在内的不同冰核的影响。结果表明，所有黄酮醇糖苷都促进了含有不同冰核的所有溶液的过冷却，尽管每种黄酮醇糖苷在含有不同冰核的溶液中的过冷却能力大小有所变化。另一方面，这些黄酮醇糖苷在不含有确定的冰核，但仅含有未识别的空气传播杂质的 BMQW 中表现出复杂的成核反应。Q3Glc 在这种水中表现出过冷却促进和冰核形成能力，这取决于浓度。K3Glc 和 K7Glc 在这种水中仅表现出冰核形成能力。在 BMQW 中的乳状液冻结试验也表明，K3Glc 和 Q3Glc 对同质冰核化温度没有影响，而 K7Glc 增加了冰核化温度。结果表明，每种黄酮醇糖苷通过非常复杂和不同的反应影响冰核形成。需要进一步研究来确定这些黄酮醇糖苷在可能存在未识别的异质冰核的 XPC 深层过冷却中的确切作用。
