DNA Condensation Triggered by the Synergistic Self-Assembly of Tetraphenylethylene-Viologen Aggregates and CT-DNA

Development of small organic chromophores as DNA condensing agents, which explore supramolecular interactions and absorbance or fluorescence-based tracking of condensation and gene delivery processes, is in the initial stages. Herein, we report the synthesis and electrostatic/groove binding interaction–directed synergistic self-assembly of the aggregates of two viologen-functionalized tetraphenylethylene (TPE-V) molecules with CT-DNA and subsequent concentration-dependent DNA condensation process. TPE-V molecules differ in their chemical structure according to the number of viologen units. Photophysical and morphological studies have revealed the interaction of the aggregates of TPE-V in Tris buffer with CT-DNA, which transforms the fibrous network structure of CT-DNA to partially condensed beads-on-a-string-like arrangement with TPE-V aggregates as beads via electrostatic and groove binding interactions. Upon further increasing the concentration of TPE-V, the “beads-on-a-string”-type assembly of TPE-V/CT-DNA complex changes to completely condensed compact structures with 40–50 nm in diameter through the effective charge neutralization process. Enhancement in the melting temperature of CT-DNA, quenching of the fluorescence emission of ethidium bromide/CT-DNA complex, and the formation of induced CD signal in the presence of TPE-V molecules support the observed morphological changes and thereby verify the DNA condensation abilities of TPE-V molecules. Decrease in the hydrodynamic size, increase in the zeta potential value with the addition of TPE-V molecules to CT-DNA, failure of TPE-V/cucurbit(8)uril complex to condense CT-DNA, and the enhanced DNA condensation ability of TPE-V2 with two viologen units compared to TPE-V1 with a single viologen unit confirm the importance of positively charged viologen units in the DNA condensation process. Initial cytotoxicity analysis on A549 cancer and WI-38 normal cells revealed that these DNA condensing agents are non-toxic in nature and hence could be utilized in further cellular delivery studies.

Preparation of Soluble POSS-Linking Polyamide and Its Application in Antifogging Films

In this study, we prepared a polyhedral oligomeric silsesquioxane (POSS)-linking polyamide (POSS polyamide) by a polycondensation of ammonium-functionalized POSS (POSS-A) and carboxyl-functionalized POSS (POSS-C) in dehydrated dimethyl sulfoxide (DMSO) using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) as condensing agents. The obtained POSS polyamide was soluble in various highly polar solvents, and it could form a self-standing film. FT-IR, 1H NMR, and 29Si NMR analyses showed that POSS polyamide is a polymer in which POSS-A and POSS-C are linked almost linearly by amide bonds. Furthermore, the cast film obtained by heat-treating the polymer at 150 °C for 30 min exhibited excellent transparency and hard-coating (pencil scratch test: 5H) and antifogging properties (evaluation by water vapor exposure).

Novel soluble and heat-resistant polyamides derived from 4-(4-diphenylphosphino) phenyl-2,6-bis(4-aminophenyl)pyridine and various aromatic dicarboxylic acids

New diamine, 4-(4-diphenylphosphino)phenyl-2,6-bis(4-aminophenyl)pyridine, was prepared, and the related polyamides (PAs) bearing 2,6-diphenylpyridyl units and pendant diphenylphosphinophenyl groups were synthesized by direct polycondensation of this diamine and various aromatic diacids in N-methyl-2-pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. The resulting PAs with inherent viscosities of 0.78–1.06 dL g−1 are readily soluble in polar aprotic solvents such as NMP, N, N-dimethylacetamide, and dimethylsulfoxide as well as less polar solvents such as m-cresol and pyridine. All the PAs are amorphous and could be solution-cast into transparent, flexible, and tough films, which have tensile strengths of 68.2–88.8 MPa, tensile moduli of 1.9–2.4 GPa, and elongations at break of 5.4–10.3%. These polymer films also exhibit high optical transparence with the UV cutoff wavelength in the 361–412 nm range. These PAs display glass transition temperatures of 316–332°C, 10% mass loss temperatures of 524–553°C, and more than 48% residues at 800°C in nitrogen, respectively. Their high char yields and good limited oxygen index values ranging from 39 to 44 indicate the prepared PAs show good thermal stability and flame-retardant property.

Hydrolysis, alcoholysis and aminolysis of N,N'-malonyldiimidazole

The achievements of molecular biology, biochemistry and bioorganic chemistry are largely due to the methods of organic chemistry, in particular chemistry N-azolides over the past twenty years. Imidazolides are not the most reactive group of compounds among heterocyclic amides, however, it is interesting for preparative purposes because of the availability of imidazole. It is known that compounds of this class are widely used as specific condensing agents in the synthesis of a number of biologically active substances. The investigation of the physicochemical properties of N-azolides is of great interest. According to well-known kinetic studies, the aminolysis and the alcoholysis of N-azolides proceed according to the addition-elimination mechanism. The hydrolysis of N-azolides of sterically hindered carboxylic acids proceeds according to the mechanism of monomolecular nucleophilic substitution. These conclusions are based on the study of the dependence of the rate constants and the activation energy of the acyl residue. Differences in the reactivity of N-azolides with different acyl residues are quite pronounced. In this work, the reactions of hydrolysis, alcoholysis and aminolysis of N,N'-malonyldiimidazole were studied by an HPLC method on an isocratic pump chromatograph, with a UV spectrophotometric detector with a wavelength range of 190–600 nm. A polar chromatographic column with a particle size of 5 μm was used. Acetonitrile eluent (CH3CN) was used as the mobile phase. The speed of the mobile phase was 1,000 ml/min. Before the experiment, air was removed from the mobile phase by degassing into an ultrasonic bath. We used the program "Open LAB" for processing the results. Chromatography was carried out in isocratic mode at a wavelength of 280 nm. After a certain period of time, chromatography was carried out and a decreasing peak area of the starting dionicid of malonic acid was noted. The kinetics of the processes of hydrolysis, aminolysis of alcoholysis was determined during the study. The relative instability of N,N'-malonyldiimidazole and high reactivity were established because of the calculated half-life data.