Pd(II)-Mediated Assembly of Porphyrin Channels in Bilayer Membranes

详细信息    查看全文

• 作者：Usha Devi ; James R. D. Brown ; Andrew Almond ; Simon J. Webb
• 刊名：Langmuir
• 出版年：2011
• 出版时间：February 15, 2011
• 年：2011
• 卷：27
• 期：4
• 页码：1448-1456
• 全文大小：984K
• 年卷期：v.27,no.4(February 15, 2011)
• ISSN：1520-5827

文摘

A membrane-spanning bis(meso-3-pyridyl) porphyrin 1 has been synthesized, embedded in EYPC vesicles, and upon Pd(II) addition has been shown to form ionophores that allow the passage of anionic 5/6-carboxyfluorescein through membranes. The geometric matching of bis(meso-3-pyridyl) porphyrin 1 and trans-Pd(II) was designed to give a cyclic porphyrin trimer [PdCl₂(1)]₃. However, solution-phase studies showed that PdCl₂(PhCN)₂ cross linked 1 into linear oligomers at porphyrin concentrations above 10 mM, although the formation of cyclic species was inferred from studies at concentrations below 2 渭M. Fluorescence titrations showed that embedding porphyrin 1 in bilayers greatly reduced its affinity for Pd(II), but the combination of porphyrin 1 and Pd(II) gave an ionophoric species that increased the rate of 5/6-carboxyfluorescein (5/6-CF) transit through the phospholipid bilayer 12-fold. A maximum in the 5/6-CF release rate was observed at a Pd(II) concentration of 4 渭M, and the application of a solution-phase binding model to the membrane phase showed that this peak in ionophoric activity corresponded to the greatest extent of porphyrin oligomerization. Further studies suggested these Pd(II)/porphyrin oligomers transported 5/6-CF via a channel mechanism.