Metal Complex Systems of Novel Spectroscopic Significance with Applications to Biochemical Probing

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09650885
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 工業分析化学
• Research Institution: Tohoku University
• Principal Investigator: HOSHINO Hitoshi Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (20124620)
• Co-Investigator(Kenkyū-buntansha): KANEKO Emiko Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (00241539)
• Project Period (FY): 1997 – 1998
• Keywords: metal chelate / room-temperature phosphorescence / near-infrared spectroscopy / chemical probe / 1,2-diaminobenzene / 8-quinolinol / biological microenvironment / hydrophobicity

Research Abstract

Chemical probes (reporter molecules) which are capable of detecting self-assembly media in biological systems such as lipid bilayers, cell-surface sugar-chains, and nucleic acids have been investigated in terms of the sensitized spectroscopic response in the presence of such microenvironment. The photophysical processes amenable to this function are found in metal-complex systems ; (I) near-infrared (NIR) light absorption(low energy electronic transition) and (II) room-temperature phosphorescence.
(I-a) It has been found that the hydrophobic environment, such as surfactant micelles, artificial lipid bilayers, and liposomes strongly enhances the MR absorption (730 nm - 850 nm, epsilon=(5-13)x10^4 M^<-1> cm^<-1>) of planar1 , 2-diaminobenzene chelates of Ni, Pd, and Pt ions.
(I-b) The mechanistic investigation of this hydrophobic environment recognition has been made in terms of factors affecting solution structure of water with several additives of structure-promoters, structure-breakers, and hydrophobic hydration breakers. The addition of urea, a strong hydrophobic hydration breaker, gives rise to the great enhancement of the MIR absorption as the liposome medium does. This suggests that the recognition depends upon the water-structure in the close vicinity of these chelate probes, rather than being responsible for the lipophilicity of the media of interest.
(II-a) The room-temperature phosphorescence from Pt(II) - 7-iodo-5-sulfo-8-quinolinol chelate (ex. 475 nm, em. 630 rim) is strongly facilitated in particular in n-dodecyl-beta-D-maltoside micellar solutions. This enhancement in such sugar-based surfactant micelles is interesting in relation with the applications tosugar-chain recognition necessary in biological studies.
(II-b) 4-Hydroxyacridine possessing larger pi-electron system has been synthesized for the benefit of the greater luminescence sensitivity. The Pt(II) chelate is also phosphorescent (ex. 396 nm, em. 448rim) in the above sugar-based micelles. Calf thymus DNA gives the similar enhancement effect on the luminescence of the chelate, which indicates that the chelate can afford to report the intercalation interaction with DNA molecules.