Youngjae Jeon

Synthesis and properties of non‐symmetric liquid crystal dimers containing a cholesteryl moiety

A series of non‐symmetric liquid crystal dimers having cholesteryl and 4‐trans‐(4‐n‐alkylcyclohexyl)phenoxy groups were synthesized by condensation of cholesteryl ω‐bromoalkanoates with appropriate 4‐trans‐(4‐n‐alkylcyclohexyl)phenols. The structures and thermal phase behaviour of the dimers were characterized using IR, 1H NMR and mass spectroscopy, elemental analysis, differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction measurements. Their thermal phase behaviour is significantly different to that of other cholesterol‐based liquid crystal dimers. All of these liquid crystal dimers exhibit low phase transition temperatures. The relationships between their properties and chemical structures of these new dimers are discussed.

Roles of Tsp66E and Tsp74F in border cell migration and the maintenance of border cell adhesion in Drosophila

KAI1/CD82, a member of the tetraspanin superfamily, is a tumor metastasis suppressor implicated in cell migration and adhesion in various tumor cells. Drosophila expresses an orthologue of KAI1/CD82, Tsp66E. However, the role of Tsp66E in cell migration and adhesion has not been studied. Here, we investigated the roles of Tsp66E in border cell migration and border cell adhesion, which are well-established in vivo models of cell migration and adhesion. Border cell migration was accelerated by loss of Tsp66E but delayed by Tsp66E overexpression. Deficiency of Tsp74F, a Drosophila orthologue of human Tspan11 and CD151, further increased the migration rate of Tsp66E mutant border cells. In addition, the premature detachment of border cells at stage 8 oogenesis induced by the loss of inflated, which encodes αPS2 integrin, was enhanced by Tsp66E deficiency. Interestingly, Tsp74F deficiency further enhanced the phenotype. αPS2 and βPS integrins were highly expressed in anterior follicle cells before border cell migration, consistent with an important role in border cell adhesion. The results suggest that Tsp66E and Tsp74F cooperate to negatively regulate border cell migration, support the integrin-mediated maintenance of border cell adhesion, and prevent premature migration.

Rotational viscosity calculation method for liquid crystal mixture using molecular dynamics

This paper presents the directly obtained rotational viscosity values of E7, which includes pentylcyanobiphenol, heptylcyanobiphenol, 4-cyano-4′ -n-octyloxy-1,1′ -biphenyl, and 4-cyano-4′′-n-pentyl-1,1′,1′′-terphenyl, at various temperatures using molecular dynamics computer simulation. The director mean squared displacement was achieved from the squared displacement of the mean director using the concept of the mean director of various nematic liquid crystals. The calculated values were compared with the experiment results that predicted a good agreement. Additional points that must be considered for further study are also discussed.

Nardostachys jatamansi DC ethanol extract ameliorates Aβ42 cytotoxicity

The Nardostachys jatamansi DC (NJ) root has been used as a sedative or analgesic to treat neurological symptoms and pain in traditional Korean medicine. Here, we investigate the potential effects of NJ on Alzheimers disease (AD) and reveal the molecular mechanism through which NJ exerts its effects. The neuroprotective effect of the NJ root ethanol extract against β amyloid (Aβ) toxicity was examined in vitro using a cell culture system and in vivo using a Drosophila AD model. The NJ extract and chlorogenic acid, a major component of NJ, inhibited Aβ-induced cell death in SH-SY5Y cells. Moreover, the NJ extract rescued the neurological phenotypes of the Aβ42-expressing flies (decreased survival and pupariation rate and a locomotor defect) and suppressed Aβ42-induced cell death in the brain. We also found that NJ extract intake reduced glial cell number, reactive oxygen species level, extracellular-signal-regulated kinase (ERK) phosphorylation, and nitric oxide level in Aβ42-expressing flies, without affecting Aβ accumulation. These data suggest that the neuroprotective activity of NJ might be associated with its antioxidant and anti-inflammatory properties, as well as its inhibitory action against ERK signaling; thus, NJ is a promising medicinal plant for the development of AD treatment.

Phenotypic differences between Drosophila Alzheimer’s disease models expressing human Aβ42 in the developing eye and brain

ABSTRACT Drosophila melanogaster expressing amyloid-β42 (Aβ42) transgenes have been used as models to study Alzheimer’s disease. Various Aβ42 transgenes with different structures induce different phenotypes, which make it difficult to compare data among studies which use different transgenic lines. In this study, we compared the phenotypes of four frequently used Aβ42 transgenic lines, UAS-Aβ422X, UAS-Aβ42BL33770, UAS-Aβ4211C39, and UAS-Aβ42H29.3. Among the four transgenic lines, only UAS-Aβ422X has two copies of the upstream activation sequence-amyloid-β42 (UAS-Aβ42) transgene, while remaining three have one copy. UAS-Aβ42BL33770 has the 3′ untranslated region of Drosophila α-tubulin, while the others have that of SV40. UAS-Aβ4211C39 and UAS-Aβ42H29.3 have the rat pre-proenkephalin signal peptide, while UAS-Aβ422X and UAS-Aβ42BL33770 have that of the fly argos protein. When the transgenes were expressed ectopically in the developing eyes of the flies, UAS-Aβ422X transgene resulted in a strongly reduced and rough eye phenotype, while UAS-Aβ42BL33770 only showed a strong rough eye phenotype; UAS-Aβ42H29.3 and UAS-Aβ4211C39 had mild rough eyes. The levels of cell death and reactive oxygen species (ROS) in the eye imaginal discs were consistently the highest in UAS-Aβ422X, followed by UAS-Aβ42BL33770, UAS-Aβ4211C39, and UAS-Aβ42H29.3. Surprisingly, the reduction in survival during the development of these lines did not correlate with cell death or ROS levels. The flies which expressed UAS-Aβ4211C39 or UAS-Aβ42H29.3 experienced greatly reduced survival rates, although low levels of ROS or cell death were detected. Collectively, our results demonstrated that different Drosophila AD models show different phenotypic severity, and suggested that different transgenes may have different modes of cytotoxicity. Abbreviations: Aβ42: amyloid-β42; AD: Alzheimer’s disease; UAS: upstream activation sequence

Recent simulation results on neutron sensitivity of new low-resistive phosphate glass electrode RPC using GEANT4 MC

The low rate capability behavior of conventional glass with resistivity ~ 1013 Ωcm, is not acceptable in many experiments being performed in high energy physics. The usage of low bulk resistivity glass electrode in the configuration of Resistive Plate Chamber (RPC) makes it possible for such studies where high rate environment is required. The sensitivity to neutron of low-resistive glass electrode RPC has been simulated using GEANT4 Monte Carlo codes with G4 Standard and G4 Low packages. The detailed simulation studies have been performed as a function of neutron energy in the range 10−10 MeV–10 GeV. The response of the detector in LHC background environment expected in the CMS- barrel region is evaluated for the neutron energy spectrum. According to our obtained results a hit rate 0.532 Hz/cm2 has been estimated for the RPC located in RB1 station. A comparison of the simulated results with the available experimental results has also been performed.