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Stable graphene oxide-based lyotropic liquid crystals for interfacial lubrication

Friction 2024年第5期12卷 954-967页

作者： Yumei GuO Hanglin LI Jiusheng LI Xiangqiong ZENG Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201210China university of Chinese Academy of sciences Beijing100049China

Lyotropic liquid crystals have lubricating properties due to their ordered assembly and fluidity,whose mesogens are often characterized by amphiphilic properties.Despite the attention that graphene oxide(GO)has been studied as a novel amphiphilic lyotropic mesogen this decade,and GO applied as a lubrication additive has been demonstrated in both oil and water-based systems,little research reveals the interfacial lubrication of GO liquid crystals yet.This work reports that GO aqueous dispersion can form lyotropic liquid crystals above a specific critical concentration of 5.00 mg/mL,providing a form of stable water-based lubricant,which can keep stable for several months and can reduce friction by 37.3%and wear by 25.24%.The liquid crystal phase was verified by polarizing microscope and synchrotron radiation small-angle X-ray scattering,and its rheological properties and viscoelasticity were studied by interfacial rheometer.The formation of lyotropic liquid crystals can enhance the stability of GO aqueous dispersions at high density,simultaneously ensuring friction decrease and anti-wear effect.It is attributed to the stable nematic network by the ordered GO sheets.The ordered assembly structure bears vertical shear force,therefore,reducing the wear.It is also assumed that the wide lateral size of graphene oxide promotes the nematic phase thus smoothes the graphene oxide film composed spontaneously under the coincidence of lamellar liquid crystal and 2D layered material.Through this work,the interlayer lubrication of GO was optimized,and the problem of GO dispersion sedimentation was solved by self-assembly.The range of interfacial lubrication of GO aqueous dispersion has been expanded and the synergistic effect is conducive to the environmentally friendly lubricants.

关键词： lyotropic liquid crystal graphene oxide aqueous lubrication tribological behavior

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Formulation of lyotropic liquid crystal emulsion based on natural sucrose ester and its tribological behavior as novel lubricant

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Friction 2022年第11期10卷 1879-1892页

作者： Yumei GuO Jiusheng LI Xiaojie ZHOu Yuzhao TANG Xiangqiong ZENG Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China university of Chinese Academy of sciences Beijing 100049China national facility for protein science in shanghai Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China

The tribological behavior of oil-in-water emulsions formulated with natural lyotropic liquid crystal(LLC)emulsifiers based on natural sucrose ester was studied for the first time.Polarized optical microscopy,synchrotron radiation small-angle X-ray scattering,wide-angle X-ray scattering,and synchrotron radiation infrared microspectroscopy demonstrated that LLC emulsifiers were tightly ordered at the oil–water interface with a distinct nematic texture.The viscosity of emulsion was observed to change over time.Moreover,the zeta potential and laser particle size distribution verified the emulsion’s satisfactory stability.The frictional shearing test proved that the coefficient of friction of the emulsion versus pure oil decreased by 34.2%.The coefficient of friction of the emulsion with liquid crystal decreased 10.1%versus that without liquid crystal.Although liquid crystal emulsion did not exhibit outstanding anti-wear performance compared with pure oil,its wear volume was 29.4%less than the emulsion without liquid crystal.X-ray photoelectron spectroscopy and scanning electron microscope–energy dispersive X-ray spectroscopy(SEM–EDS)proved that the tribo-film of the emulsion with liquid crystal was formed synergistically by the liquid crystal phase with the base oil.The formulation affecting the lubricant quality was further studied by orthogonal experiments.The resulting Stribeck curve behavior suggested that proper composition with a slightly higher viscosity can better reduce friction in both boundary lubrication and mixed lubrication regimes.The lubrication mechanism indicated that the periodically ordered liquid crystal was transported to the sliding asperity in the form of emulsion droplets,which bored the pressure and released the oil to form a tribo-film.This LLC emulsion is environmentally friendly and potentially non-irritant to the skin.Thus,it has promising application prospects as novel water-based and biological lubricants.

关键词： lyotropic liquid crystal(LLC) emulsion aqueous lubrication tribological behavior

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broad-spectrum rescue compounds for structural p53 mutations: perspective on ‘Arsenic trioxide rescues structural p53 mutations through a cryptic allosteric site’

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Journal of Molecular Cell biology 2021年第2期13卷 155-157页

作者： Jia-Le Wu Shuo Chen Min Lu shanghai.Institute of Hematology State Key Laboratory of Medical GenomicsNational Research Center for Translational Medicine(Shanghai)Ruijin Hospital affiliated to Shanghai Jiao Tong University School of MedicineShanghai 200025China

Precision medicine targeting gene mutations holds the promise of changing the landscape of cancer care and prognosis,but currently approved drugs in this category are efficacious in only a very small percentage of all cancer patients(Tannock and Hickman,2016).TP53,encoding the tumor suppressor and transcription factor p53,is the most frequently mutated gene in human cancers(Joerger and Fersht,2016;Sabapathy and Lane,2018;Levine,2019).Pharmacologically rescuing mutant p53 by restoring wild-type function could therefore potentially be widely applicable in cancer treatment and is considered to be a holy grail of cancer research(Joerger and Fersht,2010).Indeed,at least 17 compounds that can rescue mutant p53 variants were reported by 2018(Sabapathy and Lane,2018).unfortunately,p53 mutations still remain therapeutically nonactionable due to challenges such as heterogeneous mechanisms of inactivation by different mutations and the absence of obvious targetable drug-binding pockets(except Y220C mutant).In a recent publication(Chen et al.,2021),we reported the identification of small-molecule compounds that rescue a broad class of p53 mutations.Notably,these include arsenic trioxide(ATO),which is used to treat acute promyelocytic leukemia(de Théet al.,2017).The study differentiates itself from previous reports in:(i)rescuing mutant p53 at striking levels when benchmarked against previously reported rescue compounds;(ii)providing a structural mechanism,wherein the arsenic atom binds to a cryptic allosteric site connecting the loop–sheet–helix(LSH)motif with theβ-sandwich skeleton to increase the thermostability of mutant p53;(iii)offering a largely defined spectrum of applicable p53 mutations—the structural mutations that compromise the wild-type structure of p53 and collectively account for more than half of all clinically relevant p53 alterations.

关键词： structural spectrum collective

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