Facilitated Catecholamine Transport through Bulk and Polymer-Supported Liquid Membranes

Abstract

A series of crown boronic acids, 1−4, were synthesized and studied as carriers for catecholamine transport through bulk liquid membranes (BLMs) and supported liquid membranes (SLMs). Carrier 1 greatly facilitated the transport of primary catecholamines through BLMs; whereas, the more lipophilic analogues 3 and 4 were less effective. A combination of kinetic, mass spectral, and NMR evidence suggests that the transported species in BLMs is the cyclic, zwitterionic, 1:1 complex 7. The SLM transport studies used a liquid membrane of 2-nitrophenyl octyl ether supported by a thin, flat sheet of porous polypropylene. In the absence of carrier there was neglible dopamine transport (<5 × 10-9 mol/m2·s) at pH 7.2. When the membrane contained carrier 3 (33 mM or about 2% wt), facilitated catecholamine transport was observed in the order of dopamine (5 × 10-7 mol/m2·s) > epinephrine (1.5 × 10-7 mol/m2·s) > norepinephrine (0.8 × 10-7 mol/m2·s). SLMs containing carrier 3 were stable, implying that carrier 3 is a very good candidate for transport mechanism studies. Crown boronic acid 4 was an even better transport carrier of primary catecholamines with a transport order of norepinephrine (4.7 × 10-6 mol/m2·s) > dopamine (3.5 × 10-6 mol/m2·s) ≫ epinephrine (3 × 10-8 mol/m2·s). It is 10 times more effective than an equimolar mixture of boronic acid 5 and crown 6, which is one of best examples of ditopic cooperativity yet observed in SLM transport. SLMs containing 4, however, did not exibit long-term stability. Overall, it is possible that a device based on SLMs containing crown boronic acid carriers can be developed to selectively extract catecholamines from clinical samples.

A supported liquid membrane (SLM) with resorcinarene for facilitated transport of methyl glycopyranosides: Parameters and mechanism relating to the transport

“…To explain this phenomenon, we suggested in the transport of alditols [23], that the diffusion process is perhaps accompanied by a convection movement, which would be responsible for accelerating the diffusion of complexes in the membrane. While the hypothesis of "fixed-site jumping" proposed by Smith et al in the transport of sugar through a plasticized membrane of triacetate cellulose [18][19][20][21][35][36][37][38][41][42][43] is another suggestion, more likely to clarify this point. This theory assumes that the substrate moves by jumping from site to site, inside the membrane.…”

Computational Investigation of the Oxidative Deboronation of Boroglycine, H2N−CH2−B(OH)2, Using H2O and H2O2

“…In synthetic organic chemistry, the properties of boronic acids as mild Lewis acids have made them an attractive class of intermediates [25] that have been widely used in Suzuki cross-coupling reactions [3, 26], Diels-Alder reactions [27], asymmetric synthesis of amino acids [28], selective reduction of aldehydes [29], and carboxylic acid activation [30, 31]. Biochemical and medicinal applications of boronic acids include inhibitors of serine proteases and beta-lactamases [32–34], bioconjugates [35], transmembrane transporters [36–39], anti-HIV drugs [40, 41], substrates for protein immobilization [42], and agents in neutron capture therapy [43–45]. …”

Enantioselective Polymeric Transporters for Tryptophan, Phenylalanine, and Histidine Prepared Using Molecular Imprinting Techniques

“…The ability for these polymers to enantioselectively transport the corresponding amino acid across an organic phase was examined by using a Ushaped tube as it is often used in similar transport studies ( Fig. 1) (26). In such a design, 8 ml of chloroform was used to suspend the polymer particles (10 mg/ml).…”