Effects of grafted polymers on the lipid membrane fluidity.

Since the membrane fluidity controls the cellular functions, it is important to identify the factors that determine the cell membrane viscosity. Cell membranes are composed of not only lipids and proteins but also polysaccharide chain-anchored molecules, such as glycolipids. To reveal the effects of grafted polymers on the membrane fluidity, in this study, we measured the membrane viscosity of polymer-grafted giant unilamellar vesicles (GUVs), which were prepared by introducing the poly (ethylene glycol) (PEG)-anchored lipids to the ternary GUVs composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol. The membrane viscosity was obtained from the velocity field on the GUV generated by applying a point force, based on the hydrodynamic model proposed by Henle and Levine. The velocity field was visualized by a motion of the circular liquid ordered (Lo) domains formed by a phase separation. With increasing PEG density, the membrane viscosity of PEG-grafted GUVs increased gradually in the mushroom region and significantly in the brush region. We propose a hydrodynamic model that includes the excluded volume effect of PEG chains to explain the increase in membrane viscosity in the mushroom region. This work provides a basic understanding of how grafted polymers affect the membrane fluidity.

The use of the software JST-XRD for identification of crystalline phases in pharmaceutical raw materials and tablets / Uso do software JST-XRD para identifcação de fases cristalinas em insumos farmacêuticos e medicamentos

Study of polymorphism is of great importance for the pharmaceutical industry once polymorphs may display different physicochemical properties, which, in turn, may result in stability differences that can bring problems for the manufacturing stages and the quality of fnal products. Although research on organic polymorphs has greatly increased in the last decades, it still does not cover all needs for the pharmaceutical market. Techniques such as spectroscopy in the infrared region, nuclear magnetic resonance, thermal analysis, X-ray diffraction, etc., can be used to identify polymorphism. The polymorphism is a property of the crystalline solid state, and can be evaluated by X-ray diffraction once each polymorph exhibits one specifc X-ray diffraction pattern. The JST-XRD program is a tool designed to help the identifcation of crystalline phases (including polymorphs) present in pharmaceutical ingredients and tablets by using X-ray diffraction data obtained from scientifc articles and patents. This paper presents new implementations for the JST-XRD and describes its use in the analysis of active pharmaceutical ingredient and marketed tablets of norfloxacin, mebendazole and atorvastatin calcium. By the means of comparison, JSTXRD allowed identifying the crystalline phases in the diffraction patterns of the analyzed drugs, showing the program suitability for polymorphism research, pre-formulation and quality control in pharmaceutical industries. JST-XRD can also be used for educational purposes in undergraduate and graduate programs in order to show the potentiality of X-ray powder diffraction in polymorphism analysis.(AU)

O estudo do polimorfsmo é de grande importância na indústria farmacêutica porque os polimorfos podem apresentar diferentes propriedades físico-químicas, podendo resultar em diferenças na estabilidade e desse modo causar problemas nas etapas de manufatura e no produto fnal. Embora a pesquisa de moléculas orgânicas que apresentam polimorfsmo tenha aumentado bastante nas últimas décadas, ainda não contempla todas as necessidades do mercado farmacêutico. Para a identifcação de polimorfsmo podem ser utilizadas técnicas como espectroscopia na região do infravermelho, ressonância nuclear magnética, análise térmica (DSC), difração de raios X, etc. O polimorfsmo, por ser uma propriedade do estado sólido e cristalino, pode ser avaliado através da difração de raios X, já que cada polimorfo apresenta um padrão de difração de raios X único. O programa JST-XRD é uma ferramenta projetada para auxiliar a identifcação de fases cristalinas, incluindo polimorfos, presentes em insumos farmacêuticos e comprimidos, usando dados de difração de raios X obtidos em artigos científcos e patentes. Esse trabalho apresenta novas implementações no JST-XRD e descreve seu uso na análise de amostras de princípio ativo e comprimidos comerciais de norfloxacino, mebendazol e atorvastatina cálcica. Através das comparações realizadas, JSTXRD permitiu identifcar todas as fases cristalinas dos difratogramas dos fármacos analisados, mostrando que o programa é adequado para pesquisa em polimorfsmo; na pré-formulação e controle de qualidade em indústrias farmacêuticas, assim como para uso didático em cursos de graduação e pós-graduação a fm de mostrar as potencialidades da difração de raios X na análise de polimorfsmo.(AU)