| Abstract
| - The thiazole orange dye 1,1‘-(4,4,8,8-tetramethyl-4,8-diazaundecamethylene)-bis-4-[(3-methyl-2,3-dihydro-2(3H)-benzo-1,3-thiazolylidene)methyl]quinolinium tetraiodide (TOTO) binds to double-stranded DNA (dsDNA) in a sequence selective bis-intercalation. We have examined the binding ofderivatives of TOTO with different substituents on the benzothiazole ring. The analogues are thefollowing: 1,1‘-(4,4,8,8-tetramethyl-4,8-diazaundecamethylene)-[4-[3-(benzyl-2,3-dihydro-2-(3H)-benzothiazolylidene)methyl]quinolinium]-[4-[3-(methyl-2,3-dihydro-2-(3H)-benzothiazolylidene)methyl]quinolinium]tetraiodide (TOTOBzl) and 1,1‘-(4,4,8,8-tetramethyl-4,8-diazaundecamethylene)-bis-4-[(3-ethyl-2,3-dihydro-2(3H)-benzo-1,3-thiazole)methyl]quinolinium tetraiodide (TOTOEt). In this paper,we report the synthesis of TOTOBzl and TOTOEt together with the one- and two-dimensional 1HNMR investigations of complexes between these TOTO analogues and the dsDNA oligonucleotided(CGCTAGCG)2. Both analogues yield extremely stable complexes in which each chromophore issandwiched between two base pairs in a (5‘-CpT-3‘):(5‘-ApG-3‘) site. The linker spans over two basepairs in the minor groove. The benzyl group in TOTOBzl and the ethyl groups in TOTOEt is pointingoutward in the major groove.
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