Primaquine (PQ) is a potent therapeutic agent used in the treatment of malaria and its mechanism of action still lacks a more detailed understanding at a molecular level. In this context, we used differential scanning calorimetry (DSC), pressure perturbation calorimetry (PPC), and electron spin resonance (ESR) to investigate the effects of PQ on the lipid phase transition, acyl chain dynamics, and on volumetric properties of lipid model membranes. DSC thermograms revealed that PQ stabilizes the fluid phase of the lipid model membranes and interacts mainly with the lipid headgroups. This result was revealed by the great effect on the pretransition of phosphatidylcholines and the destabilization of the inverted hexagonal phase of a phosphatidylethanolamine bilayer. Spin probes located at different positions along the lipid chain were used to monitor different membrane regions. ESR results indicated that PQ is effective in changing the acyl chain ordering and dynamics of the whole chain of dimyristoylphosphatidylcholine (DMPC) phospholipid in the rippled gel phase. The combined ESR and PPC results revealed that the slight DMPC volume changes at the main phase transition induced by the presence of PQ is probably due to a less dense lipid gel phase. At physiological pH, the cationic amphiphilic PQ strongly interacts with the lipid headgroup region of the bilayers, causing considerable disorganization in the hydrophobic core. These results shed light on the molecular mechanism of primaquine-lipid interaction, which may be useful in the understanding of the complex mechanism of action and/or the adverse effects of this antimalarial drug.

Os pacientes submetidos ao transplante de medula óssea (TMO) apresentam um elevado risco de infecção pelo Vírus da Varicela Zoster (VVZ). 1, 2 As complicações mais freqüentes do VVZ presentes em 68% dos caso nos pacientes transplantados são as neuralgias pós-herpéticas e as neuropatias periféricas, lesões cutãneas em 41% dos casos e o envolvimento cutâneo disseminado observados em 17% dos pacientes. 2 A incidência cumulativa da infecção viral é de 13 % após 12 meses do procedimento, e de 38% após o vigésimo oitavo mês do TMO. 1 A suspensão ou a profilaxia com antivirais está relacionada com o aparecimento da in-