Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA.
Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA.
Ocul Surf. 2019 Apr;17(2):327-335. doi: 10.1016/j.jtos.2018.12.005. Epub 2018 Dec 12.
NMR spectroscopy was used to measure hydrocarbon chain branching variability in meibum with age, gender and Meibomian gland dysfuction (MGD). A cohort of 65 meibum donors without dry eye and 31 donors with MGD was studied. Heteronuclear 2D NMR was used to confirm CH resonance assignments allowing us to positively identify 23 of the 27 proton resonances of cholesteryl ester and H resonances due to straight chain, iso-branched and anteiso-branched hydrocarbons. Meibum from donors without dry eye contained 57 ± 1% straight-chains, 23 ± 1% iso-branched chains and 20 ± 1% anteiso-branched hydrocarbon chains. Compared with meibum from donors without dry eye, meibum from donors with MGD contained less, 50 ± 2% straight-chains, more, 32 ± 2% iso-branched chains and the same amount, 18.0 ± 0.07%, of anteiso-branched hydrocarbon chains. Meibum hydrocarbon chain branching did not change with age between 22 and 68 years of age, nor was it influenced by gender. Based on previous studies, one would expect anteiso-branched chains would contribute to lowering the phase transition temperature of meibum, decrease the elasticity of the tear film lipid layer and increase the molecular area and spreading of meibum on the surface of the eye. Although we speculate that the observed differences in iso-chain branching do not influence tear film stability or rheology, the speculation has yet to be tested.
NMR 光谱用于测量年龄、性别和睑板腺功能障碍 (MGD) 中类脂的烃链分支变化。研究了一组 65 名无干眼的类脂供体和 31 名 MGD 供体。使用异核 2D NMR 来确认 CH 共振分配,使我们能够正确识别胆甾醇酯的 27 个质子共振和直链、异支链和前异支链烃的 H 共振中的 23 个。无干眼供体的类脂中含有 57±1%的直链、23±1%的异支链和 20±1%的前异支链烃链。与无干眼供体的类脂相比,MGD 供体的类脂含有较少的 50±2%直链、较多的 32±2%异支链和相同量的 18.0±0.07%前异支链烃链。在 22 至 68 岁之间,类脂烃链分支不受年龄变化的影响,也不受性别影响。基于以前的研究,人们会期望前异支链会降低类脂的相变温度,降低泪膜脂质层的弹性,并增加类脂在眼睛表面的分子面积和铺展。尽管我们推测观察到的异链分支差异不会影响泪膜稳定性或流变学,但这一推测仍有待检验。
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