- New class of biodegradable polymers formed from reactions of an inorganic functional group
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Although numerous small molecules have been synthesized with sulfenamide bonds (R2N-SR), this is the first report of the synthesis of polysulfenamides. These polymers are readily synthesized at room temperature using secondary diamines and dithiosuccinimides. The dithiosuccinimides were readily synthesized in one step by the reaction of dithiols such as HS(CH 2)6SH with N-chlorosuccinimide. The resulting dithiosuccinimides were either recrystallized or readily purified by chromatography on silica gel and required no special handling. The conversions of polymerization ranged from 95 to 98%, and the molecular weights of the polymer reached as high as 6300 g mol-1. The sulfenamide bond was very stable in organic solvents, and no degradation was observed under atmospheric conditions in C6D6 for 30 days. In contrast, the sulfenamide bond readily decomposed in less than 12 h in D2O. Polysulfenamides were fabricated into micrometer-sized particles loaded with dye and endocytosed into JAWSII immature dendritic and HEK293 cells. Polysulfenamides represent a new class of polymers that are readily synthesized, stable in aprotic solvents, and readily degrade in water.
- Yoo, Jun,Kuruvilla, Denison J.,D'Mello, Sheetal R.,Salem, Aliasger K.,Bowden, Ned B.
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p. 2292 - 2300
(2012/06/29)
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- A kinetic study of S-nitrosothiol decomposition
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Under anaerobic conditions S-nitrosothiols 1a-e undergo thermal decomposition by homolytic cleavage of the S-N bond; the reaction leads to nitric oxide and sulfanyl radicals formed in a reversible manner. The rate constants, k1, have been determined at different temperatures from kinetic measurements performed in refluxing alkane solvents. The tertiary nitrosothiols 1c (k1(69°C) = 13 × 10-3 min-1) and 1d (k1(69°C) 91 × 10-3 min-1) decomposed faster than the primary nitrosothiols 1a (k1(69°C) = 3.0 × 10-3 min-1) and 1b (k1(69°C) = 6.5 × 10-3 min-1). The activation energies (E#= 20.5 - 22.8 Kcal mol-1) have been calculated from the Arrhenius equation. Under aerobic conditions the decay of S-nitrosothiols 1a-e takes place by an autocatalytic chain-decomposition process catalyzed by N2O3. The latter is formed by reaction of dioxygen with endogenous and/or exogenous nitric oxide. The autocatalytic decomposition is strongly inhibited by removing the endogenous nitric oxide or by the presence of antioxidants, such as pcresol, β-styrene, and BHT The rate of the chain reaction is independent of the RSNO concentration and decreases with increasing bulkiness of the alkyl group; this shows that steric effects are crucial in the propagation step.
- Grossi, Loris,Montevecchi, Pier Carlo
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p. 380 - 387
(2007/10/03)
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