...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Biochemistry >ORIGIN OF OPTICAL ACTIVITY IN THE PURPLE BACTERIAL PHOTOREACTION CENTER
【24h】

ORIGIN OF OPTICAL ACTIVITY IN THE PURPLE BACTERIAL PHOTOREACTION CENTER

机译：紫色细菌光合作用中心的光学活性起源

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The photoreaction center (RC) of purple bacteria contains four bacteriochlorophyll (Bch) and two bacteriopheophytin (Bph) molecules as prosthetic groups. Their optical activity, as measured by circular dichroism (CD) spectroscopy, is largely increased in situ as compared to organic solutions. The all-exciton hypothesis posits that this enhanced optical activity is entirely due to excitonic interactions between the electronic transitions of all six bacteriochlorin molecules. Using the simple exciton theory, this model predicts that the near-infrared CD spectra should be conservative. The fact that they are not, whether the special pair of Bch (SP) that constitutes the primary electron donor is reduced or oxidized, has been explained by hyperchromic effects. The present work tests this hypothesis by successively eliminating the absorption and, therefore, the optical activity of the Bphs and of the non-special-pair (non-SP) Bchs. This was accomplished by trapping these pigments in their reduced state. RC preparations with the four non-SP bacteriochlorins trapped in their reduced state and, therefore, with an intact SP displayed conservative CD spectra. RC preparations with only the electronic transitions of SP and of one non-SP Bch also showed conservative CD spectra. These conservative CD spectra and their corresponding absorption spectra were simulated using simple exciton theory without assuming hyperchromic effects. Bleaching half of the 755-nm absorption band by phototrapping one of the two Bph molecules led to the complete disappearance of the corresponding CD band. This cannot be explained by the all-exciton hypothesis. These results suggest that the optical activity of the SP alone, or with one non-SP Bch, is due to excitonic interactions. They also suggest that the optical activity of the other three bacteriochlorins is due to other factors, such as pigment-protein interaction. [References: 32]
机译：紫色细菌的光反应中心（RC）包含四个细菌叶绿素（Bch）和两个细菌脱镁叶绿素（Bph）分子作为修复基团。与有机溶液相比，通过圆二色性（CD）光谱法测量的它们的光学活性在原位大大提高。全激子假设认为，这种增强的光学活性完全归因于所有六个细菌绿素分子的电子跃迁之间的激子相互作用。使用简单的激子理论，该模型预测近红外CD光谱应该是保守的。变色效应解释了它们不是这样的事实，即构成初级电子供体的特殊对Bch（SP）是被还原还是被氧化。本工作通过连续消除Bphs和非特殊对（非SP）Bchs的吸收并因此消除其光学活性来检验该假设。通过捕获这些还原态的颜料可以实现这一点。具有四种非SP细菌绿素的RC制剂以其还原态捕获，因此具有完整的SP，显示出保守的CD光谱。仅具有SP和一个非SP Bch的电子跃迁的RC制备物也显示出保守的CD光谱。使用简单的激子理论模拟了这些保守的CD光谱及其相应的吸收光谱，而没有假定增色效应。通过光捕获两个Bph分子之一漂白755-nm吸收带的一半导致相应的CD带完全消失。全激子假设不能解释这一点。这些结果表明，单独的SP或具有一个非SP Bch的SP的光学活性是由于激子相互作用。他们还表明，其他三种细菌绿素的旋光性是由于其他因素引起的，例如色素-蛋白质相互作用。 [参考：32]

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号