Catapano Elisa R, Lillo M P, García Rodríguez C, Natale P, Langevin D, Monroy F, López-Montero I
†Departamento de Química Física I, Universidad Complutense, Ciudad Universitaria s/n, 28040 Madrid, Spain.
‡Instituto de Investigación Hospital 12 de Octubre (i+12), Avda. de Córdoba s/n, 28041 Madrid, Spain.
Langmuir. 2015 Apr 7;31(13):3912-8. doi: 10.1021/acs.langmuir.5b00229. Epub 2015 Mar 25.
Ceramides have unique biophysical properties. Their high melting temperature and their ability to form lateral domains have converted ceramides into the paradigm of rigid lipids. Here, using shear surface rheology of egg-ceramide Langmuir monolayers, a solid to fluid transition was evidenced as a vanishing shear rigidity at lower temperatures than the lipid melting temperature. Such a mechanical transition, which depends on the lipid lateral pressure, was found in a broad range temperature (40-50 °C). The solid to fluid transition was correlated to a LC to LC+LE phase transition, as confirmed by BAM experiments. Interestingly, together with the softening transition, a supercooling process compatible with a glassy behavior was found upon freezing. A new phase scenario is then depicted that broadens the mechanical behavior of natural ceramides. The phase diversity of ceramides might have important implications in their physiological roles.
神经酰胺具有独特的生物物理特性。它们的高熔点以及形成侧向结构域的能力,使神经酰胺成为刚性脂质的典范。在此,通过对鸡蛋神经酰胺朗缪尔单分子层进行剪切表面流变学研究,发现了在低于脂质熔点的温度下,固体到流体的转变表现为剪切刚性消失。这种机械转变取决于脂质侧向压力,在较宽的温度范围(40 - 50°C)内都能观察到。如掠入射小角X射线散射(BAM)实验所证实,固体到流体的转变与液晶(LC)到液晶 + 液晶扩展(LC + LE)相转变相关。有趣的是,在冷冻过程中,除了软化转变外,还发现了一个与玻璃态行为相符的过冷过程。由此描绘了一种新的相态情况,拓宽了天然神经酰胺的机械行为。神经酰胺的相多样性可能对其生理作用具有重要意义。