ABSTRACT
The simple and reversible control of the degree of polymerization, and thereby the bulk material properties, of a supramolecular polymer is reported. Noncovalent capping agents (chain stoppers) modulate the length of supramolecular polymers by stacking on the surfaces of the polymer's ends. Methylene blue (MB) is a positively charged, planar polycyclic dye that acts as a chain stopper. It can be reversibly switched between its colored, planar, cationic state and a colorless, nonplanar, neutral state (leucomethylene blue, LMB) by reduction with ascorbic acid and then reoxidized to MB by O2. LMB does not act as a chain stopper. This behavior was utilized to reversibly trigger the gel to sol transformation of supramolecular polymers formed by the self-assembly of hexameric rosettes comprising 2,4,6-triaminopyrimidine and a hexanoic acid-substituted cyanuric acid (CyCo6) in aqueous media. The results of our experiments highlight the ability of this approach to reversibly switch between the gel and solution states of materials formed from supramolecular polymers and thereby control their bulk properties.
ABSTRACT
IT127 is a dinuclear transition metal complex that contains a Pt(ii) and a Ru(iii) metal center. We have shown that IT127 is significantly more effective in binding the 29-base sarcin ricin loop (SRL) RNA in comparison to Cisplatin, a hallmark anticancer agent. Binding site analysis shows that IT127 prefers purine bases and the GAGA tetraloop region of SRL RNA. Our results with a dihydrofolate reductase (DHFR) model system reveal that IT127 binding to mRNA reduces translation of DHFR enzyme and that the Ru(iii) and Pt(ii) centers in IT127 appear to work in a synergistic manner.
Subject(s)
Coordination Complexes/chemistry , Platinum/chemistry , RNA, Messenger/chemistry , RNA, Ribosomal, 28S/chemistry , Ruthenium/chemistry , Antineoplastic Agents/chemistry , Binding Sites , Cisplatin/chemistry , Dimethyl Sulfoxide/analogs & derivatives , Dimethyl Sulfoxide/chemistry , NADP/metabolism , Nucleic Acid Conformation , Organometallic Compounds/chemistry , Protein Biosynthesis , RNA, Messenger/metabolism , Ruthenium Compounds , Tetrahydrofolate Dehydrogenase/chemistryABSTRACT
AH197, a trinuclear Ru(III)/Pt(II) metal complex, is strikingly more effective than the hallmark anticancer drug cisplatin and the Ru(III) clinical candidate NAMI-A in its binding to RNA and inhibition of primer DNA synthesis. Heteromultinuclear complexes could potentially serve as far better chemotherapeutics than mononuclear complexes.
