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Monte Carlo Simulations of Tau Proteins: Effect of Phosphorylation
Jho, Y.S.,Zhulina, E.B.,Kim, M.W.,Pincus, P.A. Elsevier 2010 Biophysical journal Vol.99 No.8
<P><B>Abstract</B></P><P>We perform Monte Carlo simulations of tau proteins bound to a cylinder that mimics a microtubule (MT), and then study them in solution. Tau protein binds to a highly anionic MT surface to stabilize the cylindrical structure of MT. The negatively charged tail domain floats away from the anionic MT surface while positively charged tau segments localize near the MT surface. Monte Carlo simulations demonstrate that, in 3RS tau isoform (which has three imperfect repeats (R) short (S) isoform), amino acids are more condensed near a highly charged interface compared to 4RL isoform (which has four imperfect repeats (R) long (L) isoform). In 4RL isoform, amino acids in tail domain stay mostly apart from the MT surface. In the bulk solution, dephosphorylated taus are separated due to Coulomb repulsion between similarly charged isoforms. Moderate phosphorylation of 3RS isoform decreases average intermolecular distance between dephosphorylated and phosphorylated taus and lead to their overlap. Further phosphorylation does not change noticeably the intermolecular distances.</P>
Interaction between two inhomogeneously charged parallel surfaces in the strong coupling regime.
Jho, Y S,Park, G,Chang, C S,Pincus, P,Kim, M W Published by the American Physical Society through 2006 Physical review. E, Statistical, nonlinear, and so Vol.73 No.2
<P>The counterion density profile and pressure between two inhomogenously charged parallel plates are analyzed analytically and numerically in the strong-coupling regime. Point charges are used and the surface charges are immobile. It is found that when the surface charge distribution is inhomogeneous, the charge coupling effect becomes stronger, the counterion spatial distribution is more localized toward the plate surfaces, and, thus, the pressure between two plates becomes lower than in the case when the surface charge distribution is homogeneous.</P>
First Year Observations of Air Quality from Geostationary Environment Monitoring Spectrometer (GEMS)
Jhoon Kim,Dongwon Lee 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10
Hourly observations of air quality (AQ) over Asia have been available by the Geostationary Environment Monitoring Spectrometer (GEMS) for the first time from a geostationary Earth orbit (GEO) since its launch in February 2020. After 8-month in orbit tests, the first light images were released in November, 2020. GEMS has observed diurnal variations of column amounts of atmospheric pollutants (O₃, NO₂, SO₂, HCHO, CHOCHO, and aerosols) with the UV-Vis spectrometer at 0.6 nm spectral resolution and sophisticated retrieval algorithms. Details of the first year of GEMS mission are presented, including calibrations, results, validations, and case studies including volcanic eruption, dusts, and urban pollution. The Advanced Meteorological Imager (AMI), Geostationary Ocean Color Imager 2 (GOCI-2), and GEMS can now provide synergistic science products to better understand air quality, the long-range transport of air pollutants, emission source distributions, and chemical processes. Faster sampling rates at higher spatial resolution increase the probability of finding cloud-free pixels, leading to more observations of aerosols and trace gases than LEO. GEMS will be joined by NASA’s Tropospheric Emissions: Monitoring of Pollution (TEMPO) and ESA’s Sentinel-4 to form a GEO AQ satellite constellation in 2022 and 2023, respectively, as recognized by the Committee on Earth Observation Satellites (CEOS).
Physical Properties of Ultra - High Molecular Weight Polyethylene in Retrieved Artificial Knee Joint
Jho, Jae Young,Bae, Dae Kyung,Shin, Hyo Seop,Lee, Choon Soo,Choi, Kui Won 한국공업화학회 2000 Journal of Industrial and Engineering Chemistry Vol.6 No.6
Physical properties of ultra-high molecular weight polyethylene (UHMWPE) in retrieved artificial knee joints were investigated. Lamella thickness, crystallinity, and mechanical chain scission appeared to increase during service. Crystallinity-depth profile was related to the conformity of joint and the thickness of tibial component. For the joint of low conformity, stress, crystallinity, and lamellae alignment were highest at subsurface 1-2 ㎜ beneath the surface, where crack propagation and delamination eventually occurred. It was suggested that the thickness and conformity of UHMWPE part should be increased for better wear-resistant tibial component of knee joint prosthesis.
The mechanical responses of tilted and non-tilted grain boundaries in graphene
Jhon, Y.I.,Zhu, S.E.,Ahn, J.H.,Jhon, M.S. Pergamon Press ; Elsevier Science Ltd 2012 Carbon Vol.50 No.10
Various mechanical characteristics of tilted and non-tilted grain boundaries in graphene were investigated under tension and compression in directions perpendicular and parallel to the grain boundaries using molecular dynamics simulation. In contrast to the non-tilted grain boundary and the pristine graphene, the mechanical response of tilted grain boundary was observed to be quite unique under perpendicular tension, exhibiting distinct crack propagation prior to tensile failure and the subsequent pattern of incomplete fracture. These features are manifested as a remarkable decrease in the slope and a rugged pattern in the stress-strain curves. The characteristic of incomplete fracture was striking especially for large misorientation angles with formation of long monoatomic carbon chains, suggesting a methodology for feasible production of the monoatomic carbon chains that have been difficult to synthesize and extract. Under perpendicular compression, the folding of the sheet occurred consistently along grain boundaries during the entire process, indicating a tunable folding, while the folding line wandered extensively for pristine graphene. Under parallel compression, we found that folding along grain boundaries disturbed the bending of the graphene substantially for intrinsic reinforcement.
Availability of brain serotonin transporters in patients with restless legs syndrome
Jhoo, J. H.,Yoon, I. -Y.,Kim, Y. K.,Chung, S.,Kim, J. -M.,Lee, S. B.,Kim, T. H.,Moon, S. H.,Kim, S. E.,Kim, K. W. Ovid Technologies (Wolters Kluwer) - American Acad 2010 Neurology Vol.74 No.6
<P>BACKGROUND: Selective serotonin reuptake inhibitors have been associated with the risk of restless legs syndrome (RLS), suggesting that dysregulation of serotonergic neurotransmission may provoke or exacerbate RLS. METHODS: We compared the availability of serotonin transporter (SERT) between 16 drug-naïve patients with RLS and 16 healthy controls. SERT was measured in the pons and medulla via [(123)I]-2beta-carbomethoxy-3beta-(4-iodophenyl) tropane (beta-CIT) SPECT. A ratio of specific to nonspecific brain uptake (V(3)'') was used for all comparisons. RLS was diagnosed according to the criteria proposed by the National Institute of Health, and its severity was measured using the International RLS Study Group (IRLSSG) Severity Scale. RESULTS: The availability of SERT was similar in the RLS group and the control group with regards to the pons (1.24 +/- 0.31 vs 1.24 +/- 0.25, p > 0.1) and the medulla (0.99 +/- 0.25 vs 1.00 +/- 0.23, p > 0.1). However, IRLSSG Severity Scale scores increased with decrease of SERT availability in both the pons (beta = -0.50, t = -3.19, p = 0.009) and the medulla (beta = -0.42, t = -2.44, p = 0.03). CONCLUSIONS: Although serotonin transporter (SERT) availability in pons and medulla was similar in the restless legs syndrome (RLS) group and the control group, the severity of RLS symptoms increased as the availability of SERT decreased. These data partially support the hypothesis that an increase of serotonergic neurotransmission in the brainstem may exacerbate RLS, possibly via dual modulations on striatal dopaminergic neurotransmission and on the activities of spinal motor and sensory neurons.</P>
Strong-Coupling Electrostatics in the Presence of Dielectric Inhomogeneities
Jho, Y. S.,Kanduč,, M.,Naji, A.,Podgornik, R.,Kim, M. W.,Pincus, P. A. American Physical Society 2008 Physical review letters Vol.101 No.18
<P>We study the strong-coupling (SC) interaction between two like-charged membranes of finite thickness embedded in a medium of higher dielectric constant. A generalized SC theory is applied along with extensive Monte Carlo simulations to study the image charge effects induced by multiple dielectric discontinuities in this system. These effects lead to strong counterion crowding in the central region of the intersurface space upon increasing the solvent-membrane dielectric mismatch and change the membrane interactions from attractive to repulsive at small separations. These features agree quantitatively with the SC theory at elevated couplings or dielectric mismatch where the correlation hole around counterions is larger than the thickness of the central counterion layer.</P>