Nanooptics and photonics
THE ISOMERIC-DEPENDENT OPTICAL PROPERTIES OF AQUEOUS SOLUTIONS OF PLATINUM-CONTAINING DRUGS
Gryn D.V.1, Naumenko A.P.1
1 Experimental physics department, Taras Shevchenko National University of Kyiv. Prospect Glushkova 4, Kyiv-03022, Ukraine. 
E-mail: dm_gryn@ukr.net, ap_naumekno@ukr.net
Platinum drugs long time has been used in many fields of biology and medicine. Although the platinum salt of PtCl2(NH3)2 exists in two isomeric configurations, the main studies were performed for the cis-form, because it is well known that the cis-form of the platinum salt (cisplatin) can intercalate inside DNA by attaching to neighboring bases, and this property used in anti-cancer drugs.
	
Fig.1 Absorbtion (a), fluorescence emission and excitation (b) spectra of cis- and trans- form of PtCl2(NH3)2	
However, recently scientists have paid attention to the trans-form of the platinum salt – transplatin as a new drug for treatment. It has less reactivity, but also interacts with DNA. Due to the shape of the molecule, it does not cling to neighboring DNA bases, but mainly connects to the bases from different strands. 
The optical properties (optical absorption, fluorescence of fluorescence excitation) of aqueous solutions of cis- and trans- forms of platinum salt PtCl2(NH3)2 were investigated. It is shown that the absorption spectra of the two substances are similar, but trans-platinum, compared with cisplatin, have more sharp shape of the peaks. The fluorescence and excitation spectra at 300 K of both isomers are very similar. Difference in the spectra observed in the absorption was not manifested in the excitation spectra. This fact needs further research and clarification.
Conclusions: 1. The difference in the isomeric structure of molecules is manifested in the optical absorption: the spectrum of the trans- isomer is more structured. 2. The difference in the isomeric structure of the molecules was not detected in the spectra of fluorescence and excitation. 3. Fluorescence of an aqueous solution of transplatin is twice as intensity of the fluorescence of cisplatin. This may be due to the higher symmetry of the transplatin molecule.