writer：Liao B, He BQ, Liu RG, Huang Y
keywords：Porphyrin; DNA; Chirality
source：期刊
specific source：Polymer Journal 2009, 41(9), 739-743
Issue time：2009年
Induced circular dichroism (CD) of achiral anionic tetrakis (4-sulfonatophenyl) porphine (TPPS) in polyanionic DNA solutions was investigated. Induced CD signals of the anionic TPPS aggregates in both cholesteric liquid crystal DNA solutions and isotropic DNA solutions are all observed within an appropriate pH range. When the pH value is less than 5, the induced CD signals of TPPS are split in the isotropic DNA solutions, which should result from the helical arrangement of TPPS molecules within the TPPS aggregates with L- or D-type helix. The induced CD signals without splitting of TPPS aggregates in the cholesteric liquid crystal DNA solutions should result from the helical arrangement of the aggregates like molecule screwing along the cholesteric helix axis. When the pH value is higher than 5.2, no induced CD can be observed in the isotropic solutions and the cholesteric liquid crystal DNA solutions, because the electrostatic repulsion force between the non-protonated TPPS molecules and the bases on DNA chains prevents the chiral induction. The mechanism of the different induced CD signals of TPPS aggregates in the DNA solutions is discussed.