Reorientation of interfacial water molecules during melting of brain sphingomyelin is associated with the phase transition of its C24:1 sphingomyelin lipids

IF 3.4 3区生物学 Q2 BIOCHEMISTRY & MOLECULAR BIOLOGY

Chemistry and Physics of Lipids Pub Date : 2024-08-30 DOI:10.1016/j.chemphyslip.2024.105434

Petra Maleš , Jana Munivrana , Lea Pašalić , Barbara Pem , Danijela Bakarić

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引用次数: 0

Abstract

Melting of brain sphingomyelin (bSM) manifests as a broad feature in the DSC curve that encompasses the temperature range of 25 – 45 °C, with two distinguished maxima originating from the phase transitions of two the most abundant components: C24:1 (T_m,1) and C18:0 (T_m,2). While C24:1/C18:0 sphingomyelin transforms from the gel/ripple phase to the fluid/fluid phase, the dynamics of water molecules in the interfacial layer remain completely unknown. Therefore, we carried out a calorimetric (DSC), spectroscopic (temperature-dependent UV-Vis and fluorescence) and MD simulation study of bSM in the absence/presence of Laurdan® (bSM ± L) suspended in Britton-Robinson buffer with three different pH values, 4 (BRB4), 7 (BRB7) and 9 (BRB9), and of comparable ionic strength (I = 100 mM). According to DSC, $\overset{̅}{T}$ _{m, 1} (≈ 34.5 °C/≈ 32.1 °C) and $\overset{̅}{T}$ _{m, 2} (≈ 38.0 °C/≈ 37.2 °C) of bSM suspended in BRB4, BRB7, and BRB9 in the absence/presence of Laurdan® are found to be practically pH-independent. Turbidity-based data (UV-Vis) detected both qualitative and quantitative differences in the response of bSM suspended in BRB4/BRB7/BRB9 ( $\overset{̅}{T}$ _m: ∼ 35 °C/32.0 ± 0.2 °C/36.4 ± 0.4), suggesting an intricate interplay of weakening of van der Waals forces between their hydrocarbon chains and of increased hydration in the polar headgroups region during melting. The temperature-dependent response of Laurdan® reported a discontinuous, pH-dependent change in the reorientation of interfacial water molecules that coincides with the melting of C24:1 lipids (on average, $\overset{̅}{T}$ _{m (LTC/HTC)}: ≈ 31.8 °C/30.6 °C/30.5 °C). MD simulations elucidated the impact of Laurdan® on a change in the physicochemical properties of bSM lipids and characterized the hydrogen bond network at the interface at 20 °C and 50 °C.

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脑鞘磷脂熔化过程中界面水分子的重新定向与其 C24:1 鞘磷脂脂质的相变有关

脑鞘磷脂（bSM）的熔化在 DSC 曲线上表现为一个广泛的特征，温度范围为 25 - 45 °C，其中有两个不同的最大值，分别源于两种最丰富成分的相变：C24:1（Tm,1）和 C18:0（Tm,2）。虽然 C24:1/C18:0 sphingomyelin 会从凝胶/碎裂相转变为流体/流体相，但界面层中水分子的动力学仍完全未知。因此，我们对悬浮在布里顿-罗宾逊缓冲液中的 bSM（bSM ± L）进行了量热（DSC）、光谱（温度依赖性紫外可见光和荧光）和 MD 模拟研究，该缓冲液有三种不同的 pH 值，分别为 4（BRB4）、7（BRB7）和 9（BRB9），离子强度相当（I = 100 mM）。根据 DSC，悬浮在 BRB4、BRB7 和 BRB9 中的 bSM 的 T̅m, 1（≈ 34.5 ℃/≈ 32.1 ℃）和 T̅m, 2（≈ 38.0 ℃/≈ 37.2 ℃）与 Laurdan® 的存在/缺失几乎无关。基于浊度的数据（紫外可见光）检测到悬浮在 BRB4/BRB7/BRB9 中的 bSM（T̅m: ∼ 35 °C/32.0 ± 0.2 °C/36.4 ± 0.4）的反应在质量和数量上的差异，这表明在熔化过程中，碳氢链之间的范德华力减弱和极性头团区域的水合作用增强之间存在着错综复杂的相互作用。Laurdan® 的温度依赖性反应显示，界面水分子的重新定向发生了不连续的、与 pH 值相关的变化，这种变化与 C24:1 脂类的熔化相吻合（平均 T̅m (LTC/HTC)：≈ 31.8 °C/30.6 °C/30.5 °C）。MD 模拟阐明了 Laurdan® 对 bSM 脂类理化性质变化的影响，并描述了 20 °C 和 50 °C 时界面氢键网络的特征。

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来源期刊

Chemistry and Physics of Lipids 生物-生化与分子生物学

CiteScore

7.60

自引率

2.90%

发文量

审稿时长

40 days

期刊介绍： Chemistry and Physics of Lipids publishes research papers and review articles on chemical and physical aspects of lipids with primary emphasis on the relationship of these properties to biological functions and to biomedical applications. Accordingly, the journal covers: advances in synthetic and analytical lipid methodology; mass-spectrometry of lipids; chemical and physical characterisation of isolated structures; thermodynamics, phase behaviour, topology and dynamics of lipid assemblies; physicochemical studies into lipid-lipid and lipid-protein interactions in lipoproteins and in natural and model membranes; movement of lipids within, across and between membranes; intracellular lipid transfer; structure-function relationships and the nature of lipid-derived second messengers; chemical, physical and functional alterations of lipids induced by free radicals; enzymatic and non-enzymatic mechanisms of lipid peroxidation in cells, tissues, biofluids; oxidative lipidomics; and the role of lipids in the regulation of membrane-dependent biological processes.