Surface active benzodiazepine-bromo-alkyl conjugate for potential GABAA-receptor purification

Abstract

A conjugable analogue of the benzodiazepine 5-(2-hydroxyphenyl)-7-nitro-benzo[e][1,4]diazepin-2(3H)-one containing a bromide C₁₂-aliphatic chain (BDC) at nitrogen N1 was synthesized. One-pot preparation of this benzodiazepine derivative was achieved using microwave irradiation giving 49% yield of the desired product. BDC inhibited FNZ binding to GABA_A-R with an inhibition binding constant K_i = 0.89 μM and expanded a model membrane packed up to 35 mN m⁻¹ when penetrating in it from the aqueous phase. BDC exhibited surface activity, with a collapse pressure π = 9.8 mN m⁻¹ and minimal molecular area A_min = 52 Ų/molecule at the closest molecular packing, resulted fully and non-ideally mixed with a phospholipid in a monolayer up to a molar fraction x ≅ 0.1. A geometrical–thermodynamic analysis along the π–A phase diagram predicted that at low x_BDC (<0.1) and at all π, including the equilibrium surface pressures of bilayers, dpPC–BDC mixtures dispersed in water were compatible with the formation of planar-like structures. These findings suggest that, in a potential surface grafted BDC, this compound could be stabilize though London-type interactions within a phospholipidic coating layer and/or through halogen bonding with an electron-donor surface via its terminal bromine atom while GABA_A-R might be recognized through the CNZ moiety.