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Synthesis and Spectroscopic Properties of Reconstituted ZincMyoglobin Appending a DNA‐Binding Platinum(II) Complex
Author(s) -
Takashima Hiroshi,
Fujimoto Emi,
Hirai Chiharu,
Tsukahara Keiichi
Publication year - 2008
Publication title -
chemistry and biodiversity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 70
eISSN - 1612-1880
pISSN - 1612-1872
DOI - 10.1002/cbdv.200890191
Subject(s) - chemistry , moiety , fluorescence , ethylenediamine , quenching (fluorescence) , zinc , photochemistry , photoinduced electron transfer , porphyrin , electron transfer , bipyridine , stereochemistry , crystallography , inorganic chemistry , organic chemistry , physics , crystal structure , quantum mechanics
A reconstituted zinc–myoglobin (ZnMb) dyad, ZnMb‐[Pt(bpy)(en)] 2+ , has been prepared by incorporating chemically‐modified zinc–porphyrin, being capable of DNA‐binding of the Pt complex, [Pt(bpy)(en)] 2+ , where bpy and en are 2,2′‐bipyridine and ethylenediamine, respectively. The steady‐state fluorescence of the cofactor, [Pt(bpy)( μ ‐enPP)Zn]Cl 2 , in MeOH indicates that the excited singlet state of zincporphyrin was almost quenched, probably because of the strong hydrophobic and π – π stacking interactions between the [Pt(bpy)( μ ‐enPP)Zn] 2+ ions. In the reconstituted ZnMb‐[Pt(bpy)(en)] 2+ , the quenching reaction of 1 (ZnMb)* with the [Pt(bpy)(en)] 2+ moiety does not occur, indicating apo‐Mb matrix is essential. On the other hand, when the [Pt(bpy)(en)] 2+ moiety was excited, the enhancement of the fluorescence from ZnMb unit was observed. It is suggested that the energy transfer from 1 ([Pt(bpy)(en)] 2+ )* to ZnMb occurs. The spectroscopic changes of ZnMb‐[Pt(bpy)(en)] 2+ in the presence of calf‐thymus DNA were also provided. Soret band at 428 nm gradually decreased, and isosbestic points at 321, 414, and 432 nm were observed with increasing the DNA concentration. When the Pt II moiety was excited at λ ex 321 nm, the fluorescence signal around 600 nm similarly decreased. The synthetic manipulation of ZnMb by using a DNA‐binding Pt II complex demonstrates sensitive fluorescent signal for DNA and valuable information to study photoinduced electron transfer within a Mb–DNA complex.