• Journal of Photoscience
• /
• v.9 no.2
• /
• pp.37-40
• /
• 2002

Ascidians are lower chordates, and their tadpole-like larvae share a basic body plan with vertebrates. To study photoreceptive systems in ascidians, we have isolated and characterized cDNA clones for three opsins, five G protein ${\alpha}$ subunits (G${\alpha}$), catalytic and regulatory subunits of cGMP phosphodiesterase (PDE), and arrestin from the ascidian Ciona intestinalis tadpole larva. Ci-opsin1 and Ci-opsin2 are vertebrate-type opsins, while Ci-opsin3 is a retinal photoisomerase similar to retinochrome and mammalian RGR. Both Ci-opsin1 and arrestin are specifically localized in the photoreceptor cells of the ocellus, whereas Ci -opsin2 is not expressed in the photoreceptors, but is co-localized in another population of neurons in the brain with PDE (Ci-PDE9 and Ci-PDE$\delta$). Ci-opsin3 is present in the entire region of the brain. Though five different cDNAs encoding Ga have been cloned, no transducin-type G protein has been found yet. Interestingly, one of G${\alpha}$i isoform is conspicuously expressed in the entire region of the brain. The Ci-opsin3 gene expression was observed in a broad area of the brain vesicle as well as in the visceral ganglion. Genes encoding ascidian homologs of CRALBP and ${\beta}$-CD, whose function is required for the mammalian visual cycle, are co-expressed with Ci-opsin3 in the brain vesicle and visceral ganglion. Localization of Ci-opsin3, CRALBP, and ${\beta}$-CD in a broad area of the brain suggests that the brain of the ascidian larva has a visual cycle system similar to that of the vertebrate RPE. Based on these data, we discuss the evolution of vertebrate visual systems.

• Journal of Life Science
• /
• v.18 no.1
• /
• pp.114-119
• /
• 2008

The molecular machinery controlling cell cycle is centered around the regulation of the activity of maturation-promoting factor (MPF), a complex composed of a catalytic Cdc2 and the cyclinB regulatory subunit. Cdc2 kinase is inactivated by phosphorylation of inhibitory kinase, Wee1. It has been known that there are three different Wee1 kinases in the mammalian cell, Wee1A, Wee1B and Myt1. To investigate the regulatory mechanism of Wee1 kinases, the phosphorylation and degradation of Wee1A and Wee1B were checked in the Xenopus oocyte cell cycle. When Wee1 kinases were injected into frog oocyte, Wee1B was more stable than Wee1A. Wee1A and Wee1B kinase were phosphorylated by many kinases such as PKA and Akt. The roles of amino or carboxyl terminal in mouse Wee1A or Wee1B kinase were investigated using chimeric constructs. The degree of protein phosphorylation, degradation and cell cycle progression were different between chimeric constructs. The amino domain of Wee1A was implicated in the protein phosphorylation and degradation while amino domain of Wee1B and carboxyl domain of Wee1A were involved in the activity regulation. These results suggested that the domains of Wee1 kinase have different and significant roles in regulating the Wee1 kinases in the cell cycle progression.

• Journal of ILASS-Korea
• /
• v.23 no.3
• /
• pp.136-148
• /
• 2018

Major countries have tighten their NOx regulation of diesel passenger cars. In the case of the EU, the regulation has been toughen up to 6.25 times since 2000. Despite the regulation the NOx concentration of the ambient has not been reduced proportionally. As these issues, to reduce NOx emission practically, Korea and the EU introduced the real-world driving emission (RDE) regulation and the test method that will be applied after 2017. In this paper, for the regulation to make a soft landing in Korea, 6 diesel passenger cars which met Euro 6a~6d regulation and were equipped with LNT/SCR were tested at a chassis dynamometer with environmental chamber applying the off-cycles (FTP, US06, SC03, HWFET and CADC) and several ambient conditions (-7 and $14^{\circ}C$) as well as certification modes (NEDC, WLTC@ $23^{\circ}C$). The result of the test showed that the ambient temp. and the engine load as a test mode impacted the NOx emission of the cars while the vehicles with SCR emitted NOx lower than with LNT. Additionally, to propose an effective RDE test method, the above result was compared with the results of the other papers which tested RDE using the same cars.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.10
• /
• pp.1597-1600
• /
• 2006

The mononuclear iron complex 1, $Fe^{III}$(Hbida)Cl($H_2O$), was synthesized using a tripodal tetradentate ligand, N-(benzimidazol-2-ylmethyl)iminodiacetic acid (H3bida), which has two carboxylate groups, one benzimida- zoyl group, and one tertiary amine where it serves as a tetradentate chelating ligand for the octahedral Fe(III) ion. The four equatorial positions of the octahedral complex are occupied by two monodentate carboxylates, a benzimidazole nitrogen, and an oxygen of a water molecule. One of the axial positions is occupied by an apical nitrogen of the Hbida and the other by a chloride anion. The mononuclear octahedral complex 1 mimics the geometry of the key intermediate structure of the catalytic reaction cycle proposed for the FeSODs, which is a distorted octahedral geometry with three histidyl imidazoles, an aspartyl carboxylate, a superoxide anion, and a water molecule. The redox potential of complex 1, $E_{1/2}$ is -0.11V vs. Ag/AgCl (0.12 V vs. NHE), which is slightly lower than those reported for the most FeSODs. The magnetic susceptibility of complex 1 at room temperature is 5.83 $\mu$B which is close to that of the spin only value, 5.92 $\mu$B of high-spin d5 Fe(III).

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.6
• /
• pp.1260-1271
• /
• 2001

The simulation program which predicts the gas behavior in a spark ignition engine has been developed and verified by the comparison with the experimental results foy the MPI engine, naturally aspirated and turbochared engines with a carburettor. First paper describes the calculations of the behavior of gas in the intake and exhaust system. The generalized method of characteristics including friction, heat transfer, area change and entropy gradients was used to analyse the pipe flow The constant-Pressure model was applied for the analysis of the flow through engine valved, and the constant-pressure perfect-mixing model was applied for the flow at manifold junction. The concept of the sudden area change was used for the muffler and catalytic convertor. Fer the plenum chamber in an MPI engine, constant-pressure model and constant-volume model were both examined. Through the comparison of predicted results with experiments, the simulation program was verified by showing good prediction of the behavior of IC engine qualitatively and quantitatively under wide range of operating conditions.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.2
• /
• pp.98-104
• /
• 2011

The introduction of a diesel engine into the passenger car and light duty applications in the United States involves significant technical challenges for the automotive makers. This paper describes the SCR System optimization procedure for such a diesel engine application to meet Tier2 Bin5 emission regulation. A urea SCR system, a representative $NO_x$ reduction after-treatment technique, is applied to a 3.0 liter diesel engine. To achieve the maximum $NO_x$ reduction performance, the exhaust system layout was optimized using series of the computational fluid dynamics and the urea distribution uniformity test. Furthermore a comprehensive simulation model for the key factors influencing $NO_x$ reduction performance was developed and embedded in the Simulink/Matlab environment. This model was then applied to the urea SCR system and played a key role to shorten the time needed for SCR control parameter calibration. The potential of a urea SCR system for reducing diesel $NO_x$ emission is shown for FTP75 and US06 emission standard test cycle.

• Journal of the Korean Magnetic Resonance Society
• /
• v.3 no.1
• /
• pp.44-51
• /
• 1999

An enzyme derived conformational changes of cobalamine is thought to be important in the homolytic cleavage of Co-C bond which is the first step of catalytic Cl-cycle of coenzyme B12-dependent enzymes. Modern 2D-NMR and NMR-based distance geometric studies were carried out to determine the 3D structure of corrin ring. Homonuclear and heteronuclear correlation NMR experiments were performed for complete 1H-NMR signal assignments. Distances between numerous proton pairs were deduced based on the NOE cross peak intensities and subsequently used as input into the distance geometry program for the 3D structure determination. The detailed 3D structure from the present NMR-based analysis was compared with the result from X-ray crystallographic study, which revealed greater conformational changes occur in benzimidazole group and sugar ring than in macrocyclic corrin and tetrapyrrole. In addition, the distance geometry used in this study was found to be quite useful for NMR-based structure determination of medium-sized molecules that give poor NOE effects arising from their intermediate tumbling rate ($\omega$$\tau$c 1.0).

• Journal of Industrial Technology
• /
• v.26 no.B
• /
• pp.163-171
• /
• 2006

Human immunodeficiency virus type 1 (HIV-1) integrase plays a critical role in the life cycle of the HIV virus. An ability to accurately map its electrostatic potential, and then use this information to predict the manner in which DNA will bind to the active site of the catalytic domain could provide a foundation for inhibitory design. Attempts to discern the crystal structure of HIV-1 integrase have proven problematic, especially in the region of enzymatic activity, that being those residues involved in the catalysis of the integration of viral DNA into the host cell. However, there is a structural correlation in to the region of interest with avian sarcoma virus (ASV), so a homology model utilizing this similarity was constructed to approximate the behavior/structure of the undetermined portions of the HIV-1 integrase crystal. After this model was constructed and its energy minimized, electrostatic calculations were carried out on the substance, so that an electrostatic potential map was constructed. Using this information, it was determined that DNA binding was oriented so as to exploit the regions of positive potential nearby the active site, as well as the positive potential of the magnesium cofactors.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.2
• /
• pp.327-333
• /
• 2009

For the Pt-catalyzed nucleophilic addition of enones, Pt complexes were employed in the presence of various phosphine ligands and $H_2\;(or\;Et_3SiH),$ affording inter- and intra-molecular coupling products in good to modest yield. Depending on reaction protocols, different phosphine ligands were required to optimize the conditions. In the aldol reaction, the Pt catalyst involving $P(2,4,6-(OMe)_3C_6H_2)3\;or\;P(p-OMeC_6H_4)_3$ was chosen. Michael reaction proceeds in good yields in the presence of $P(p-CF_3C_6H_4)_3$. Regarding the activity of the reductants, $H_2$ exhibited superior activity to $Et_3SiH$, resulting in a shorter reaction time and higher yield in the aldol and Michael reaction. In light of the deuterium labeling studies, the catalytic cycle including the hydrometalation of the enones by the platinum hydride species was proposed.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.3
• /
• pp.306-312
• /
• 2005

IMO $NO_x$ levels are generally possible to meet by means of primary on-engine measures. Further significant follow-on reductions are likely to require a secondary after-treatment technique. SCR(Selective Catalytic Reduction) technology is used almost exclusively for $NO_x$ removal in stationary combustion systems. In order to develop a practical SCR system for marine application on board ship, a primary SCR system using urea was made. The SCR system was set up on the ship, 'HANNARA' as a test vessel. employed a two-stroke cycle diesel engine as main propulsion, which is a training ship of Korea Maritime University. The purpose of this paper is to report the results about the basic effects of the below system parameters, The degree of $NO_x$ removal depends on some parameters, such as the amount of urea solution added, space velocity, reaction gas temperature and activity of catalyst.