Polymers Containing Hydroxamate Groups: Nanoreactors for Hydrolysis of Phosphoryl Esters

Abstract

A polyhydroxamicalkanoate (PHA) polymer containing the functional groups hydroxamic acid and carboxylic acid with the ability to accelerate dephosphorylation reactions is proposed. The methodology used to prepare this polymer favored the position of the two functional groups next to each other, which allows for the cooperativity between these groups. This cooperative effect has an important role when one wants to mimic enzymes. The catalytic effect promoted by the polymer was evaluated on the cleavage of the bis(2,4-dinitrophenyl) phosphate (BDNPP) and diethyl 2,4-dinitrophenyl phosphate (DEDNPP) esters. Indeed, PHA was very efficient and promiscuous because it increased the rate of both reactions by a factor of up to 10(6)-fold. Isothermal titration calorimetry (ITC) experiments showed that the presence of PHA aids the formation of cetyltrimethylammonium bromide (CTABr) micelles. Thus, the effect of the cationic surfactant CTABr on the dephosphorylation of BDNPP by PHA was also investigated, and it was observed that, when CTABr is added to PHA, the reaction is ca. 15-fold faster compared to the reaction when only PHA is present.

Interaction of cationic dodecyl‐trimethyl‐ammonium bromide with oxy‐HbGp by isothermal titration and differential scanning calorimetric studies: Effect of proximity of isoelectric point

“…The cac is assigned to the formation of premicellar aggregates, formed along the polymer chain, being characterized by the sharp increase in DH. 20,21 Although the DH curves follow the same behavior (an endothermic peak before DTAB cmc), the cac values are significantly different, 8.2 and 4.2 mmol/L, at pH 5.0 and 7.0, respectively (see Table I). These results suggest that the interaction of DTAB with hemoglobin is significantly dependent on the medium pH.…”

“…This method is broadly used in the surfactants-polymers research area. 20,21 In the present work, ITC and HSDSC, at pH 5.0 and 7.0, are applied as the main tools, in combination with pyrene fluorescence emission and dynamic light scattering at pH 7.0, aiming to investigate changes caused by the interaction of the cationic surfactant DTAB with oxy-HbGp. For this purpose, ITC curves were obtained for oxy-HbGp, in the concentration range from 0.08 to 0.84 lmol/L, at 258C.…”

Desenvolvimento de um biossensor mimético descartável para pesticidas organofosforados e carbamatos para o controle de qualidade de águas de abastecimento

“…O polímero PHA contendo grupos ácidos hidroxâmico e carboxilíco foi preparado de acordo com a rota sintética proposta por Mello et al (2011). 64 …”

“…89 Os valores de pK a encontrados para o PHA foram pk a1 5,5 e pK a2 9,3 de acordo com o equilíbrio mostrado no Esquema 1. 64 , o polímero PHA atua como um nanoreator na reação com organofosforados devido ao efeito alfa nucleófilo relacionado à sua constituição, uma vez que possui grupos hidroxamatos e carboxílicos em sua estrutura, podendo funcionar de modo similar aos processos enzimáticos. Nanoreatores são complexos moleculares ou moléculas grandes com cavidade estrutural externamente acessível, na qual uma ou mais moléculas são capazes de entrar e sofrer transformações químicas, de modo que várias enzimas naturais ou sintéticas podem ser classificadas como tal.…”

“…Diante disso, uma vez reportada a habilidade do PHA em acelerar a desfosforilação de alguns compostos, 64 houve interesse em avaliar seu efeito em relação ao organofosforado paraoxon. Aquelas com energias intermediárias estão representadas em B e C. …”