Maleš, Petra; Munivrana, Jana; Pašalić, Lea; Pem, Barbara; Bakarić, Danijela (2024) Reorientation of interfacial water molecules during melting of brain sphingomyelin is associated with the phase transition of its C24:1 sphingomyelin lipids. Chemistry and Physics of Lipids, 264 . ISSN 0009-3084
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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 (Tm,1) and C18:0 (Tm,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 (temperaturedependent 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, Tm, 1 (≈ 34.5 ◦C/≈ 32.1 ◦C) and Tm, 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 (Tm: ~ 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, Tm (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.
| Item Type: | Article | ||||||||
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| Uncontrolled Keywords: | brain sphingomyelin (bSM) ; differential scanning calorimetry ; temperature-dependent UV-Vis and fluorescent spectroscopies ; Laurdan® ; multivariate curve resolution approach | ||||||||
| Subjects: | NATURAL SCIENCES NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry |
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| Divisions: | Division of Organic Chemistry and Biochemistry | ||||||||
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| Depositing User: | Danijela Bakarić | ||||||||
| Date Deposited: | 15 Jan 2026 11:46 | ||||||||
| URI: | http://fulir.irb.hr/id/eprint/10803 | ||||||||
| DOI: | 10.1016/j.chemphyslip.2024.105434 |
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