Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
Photochem Photobiol Sci. 2019 May 15;18(5):1218-1227. doi: 10.1039/c8pp00535d.
Zinc bacteriochlorophyll-d analogs possessing a methylene group at the 132-position were prepared by chemical modification of naturally occurring chlorophyll-a. The synthetic 31-epimers were successfully separated by reverse phase HPLC to give diastereomerically pure samples. The stereochemistry of the chiral C31-center in the separated bacteriochlorophyll-d analogs was determined by HPLC analysis of the authentic stereoisomers prepared stereospecifically. Both the epimers were monomeric in tetrahydrofuran to give sharp absorption bands, while they self-aggregated to form chlorosomal oligomers with red-shifted bands in an aqueous Triton X-100 micelle solution. The resulting large oligomers deaggregated by addition of Triton X-100 to give monomeric species. Their aggregation and deaggregation were dependent on the 31-stereochemistry, indicating that each epimer produced self-aggregates that were supramolecularly different. The substitution with the 132-methylene group enhanced their self-aggregation abilities and the stability of their resulting self-aggregates.
通过对天然叶绿素-a 的化学修饰，制备了在 132 位具有亚甲基的锌细菌叶绿素-d 类似物。通过反相高效液相色谱法成功地将合成的 31-差向异构体分离，得到了对映体纯的样品。通过立体特异性制备的真实立体异构体的 HPLC 分析，确定了分离的细菌叶绿素-d 类似物中手性 C31-中心的立体化学。两种差向异构体在四氢呋喃中均为单体，给出尖锐的吸收带，而在含有 Triton X-100 的水性胶束溶液中，它们自组装形成具有红移带的类菌叶绿素寡聚物。加入 Triton X-100 可使生成的大寡聚物解聚成单体。它们的聚集和解聚依赖于 31-立体化学，表明每个差向异构体产生的自组装体在超分子水平上是不同的。132 位亚甲基的取代增强了它们的自组装能力和所得自组装体的稳定性。
