• Journal of the Korea Institute of Military Science and Technology
• /
• v.17 no.5
• /
• pp.561-568
• /
• 2014

The Republic of Korea Army is using R-NAD of MIL-STD-188-220 as a Media Access Control protocol. Under urgent situations, almost all stations transmit data frames and then the network will reach a saturation state. Several articles have been devoted to the study of R-NAD performance. However, most of them focus on comparing the performance of some NADs using network simulation tools. We propose an analytical model to compute the throughput of R-NAD under the assumption of a network traffic saturation. Analytical results were verified by Monte Carlo methods. We have shown that the performance of a success probability and an average idle time remains almost unchanged as the total number of stations increases. We have also shown that Type 1/2/4 operation mode outperforms Type 3 operation mode in throughput. The results showed that the system with a squelch detection achieved a better performance than the one without it. The longer DATA time had a higher throughput.

• Journal of Life Science
• /
• v.8 no.5
• /
• pp.486-491
• /
• 1998

Previously, we have cloned and characterized two ADP-ribosyltransferases (Yac-1 and Yac-2) from mouse Iym-phocyte. Yac-2 transferase contains significant NAD glycohydrolase activity as well as ADP-ribosyltransferase acti-vity. Yac-2 has an arginine at position 221 between two conserved glutamic acids. To investigate the significance of Arg-221 on enzyme activities, Arg-221 was mutagenized to Glu (R221E) and to Ala (R221A). Mutants R221E and R221A were active as wild type for ADP-ribosyltransferase and NAD glycohydrolase activity, suggesting that the arginine 221 in Yac-2 does not play a major role in enzyme activities.

• Journal of Life Science
• /
• v.24 no.1
• /
• pp.98-103
• /
• 2014

NAD(P)H quinone oxidoreductase 1 (NQO1) is a flavoprotein that catalyzes the two electron reduction of diverse substrates, including quinones. It uses NADH or NADPH as a cofactor for enzymatic machinery. In the metabolism of quinones, NQO1 has two conflicting functions because of the different stability of converted hydroquinones. The stable form of hydroquinone is excreted from cells by conjugation with glutathione or glucuronic acid. The unstable form of hydroquinone induces cell death by induction of oxidative stress and DNA damage. Certain quinones known as bio-reductive agents have a cytotoxic function following reduction by NQO1. Bio-reductive agents, such as ${\beta}$-lapachone or mitomycin C, induce the depletion of NAD(P)H and the generation of oxidative stress in an NQO1-dependent manner. NQO1 is highly expressed in several cancer tissues. Therefore, NQO1 is a good therapeutic target for cancer treatment with bio-reductive agents.

• Molecules and Cells
• /
• v.25 no.2
• /
• pp.158-162
• /
• 2008

Recent molecular genetics studies have revealed that cyclic electron transport around photosystem I is essential for normal photosynthesis and growth of plants. Chloroplastic NAD(P)H dehydorgenase (NDH) complex, a homologue of the complex I in respiratory electron transport, is involved in one of two cyclic pathways. Recent studies on the function and structure of the NDH complex are reviewed.

• The Korean Journal of Zoology
• /
• v.17 no.4
• /
• pp.163-166
• /
• 1974

Malate dehydrogenases of ten bivalved mollusks consist of one or two isozyme, which are species-spcific. It is concluded that the electrophoretic character of the enzyme is available for identification of these ten bivalves.

• Animal cells and systems
• /
• v.9 no.4
• /
• pp.191-198
• /
• 2005

The effects of 6-aminonicotinamide (6-AN) on viability of IMR32 neuroblastoma cells in the presence of ATP or $NAD^+$ have been investigated. 6-AN caused marked reduction in cell viability and similar observations were also made with cells treated with 6-AN+ATP. However, cells treated with $6-AN+NAD^+$ showed cell viability similar to untreated cells. Morphologically, 6-AN and 6-AN+ATP treated cells showed loss of neurites, polyhedric shapes, shrinkage of cell bodies and formation of lysed cells, while $6-AN+NAD^+$ cells did not show any such changes. The flow cytometry analysis demonstrated that 6-AN increased cell population in $G_0/G_1$ phase and decreased cell population in Sand $G_2/M$ phase following a 72 h exposure. Western blot analysis showed that 6-AN stimulated a substantial increase in the level of the cdk inhibitor $p27^{kip1}$, but lowered the levels of cdk2, cyclin E and p-Rb. However, cdc25A and p53R2 were not significantly affected. Immunofluorscence staining of $p27^{kip1}$, cdk2, cyclin E and p-Rb revealed close correlation between the signal observed in the Western blot analysis. 6AN+ATP treated cells showed similar results obtained with 6-AN treated cells in expression of cdk2, cyclin E, p-Rb proteins and $p27^{kip1}$, $6-AN+NAD^+$ cells showed greater expression of cdk2, cyclin E and p-Rb than those in 6-AN and 6-AN+ATP treated cells. The results suggest that 6-AN induced the $G_0/G_1$ phase arrest in IMR32 neuroblastoma cell lines through the increase of $p27^{kip1}$ and the decrease of cdk2, cyclin E and p-Rb.

• Biodesign
• /
• v.7 no.1
• /
• pp.24-27
• /
• 2019

Pnc1 converts nicotinamide to nicotinic acid to generate NAD⁺ through the Preiss-Handler pathway that is one of the NAD⁺-salvage pathway. By reducing levels of nicotinamide, an inhibitor of the NAD⁺-dependent histone deacetylase Sir2, yeast Pnc1 contributes gene silencing. In this study, to understand the structural features and molecular mechanism of nicotinamidase Pnc1, we overexpressed, purified, and crystallized the N-terminally His₆-tagged Pnc1 protein from Kluyveromyces lactis and obtained X-ray diffraction data at a resolution of 2.2 Å. The crystals of the K. lactis Pnc1 (KlPnc1) belonged to space group P2₁2₁2₁ with unit cell parameters a=38.5, b=77.3, c=83.3, and α=β=γ= 90°. There is one molecule in the asymmetric unit.

• Applied Biological Chemistry
• /
• v.41 no.4
• /
• pp.228-234
• /
• 1998

An adaptive measure of photosynthetic cells to a condition identified with a reduction of cellular energy charge, caused by water deficit-induced impairment of photosynthetic ATP production, was investigated using hydroponically cultured rice seedlings. Water stress treatment of the seedlings resulted in a marked decrease in cellular ATP level, a significant increase in the content of NAD(H) and concurrent decrease in that of NADP(H) in shoots, which accompanied a decrease in the activity of NAD kinase (EC 2.7.1.23) that specifically converts NAD(H) to NADP(H). The decline in the enzyme activity was particularly evident in the $Ca^{2+}/calmodulin-dependent$ kinase, the major form of NAD kinase in plants, whereas the level of active calmodulin remained unchanged during water deficit. The ratio of $NADP^+$ to NADPH was maintained nearly constant and no increases were seen in the level of $H_2O_2$ and the activities of $superoxide/H_2O_2-detoxifying$ enzymes in shoots stress-treated for two days. Based on these results, it may be suggested that rice plants take a strategy to cope with an adverse situation of limited photophosphorylation created by water deficit in that cells facilitate ATP production through glycolysis and oxidative phosphorylation; in doing so, rice cells suppress NAD kinase activity, consequently up-sizing the NAD(H) pool at the expense of the NADP(H) pool. Several parameters associated with the stress symptoms are also of implicative that there is no overproduction of superoxide radical or the related active oxygen at least in rice seedlings.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.10
• /
• pp.977-985
• /
• 2012

Recently, many countries have been developing new protocols to improve the performance of tactical ad hoc networks for implementing NCW (Network Centric Warfare). Combat net radio (CNR) networks are the most important communication infra for the ground forces such as infantry of Army. U.S. Army had developed MIL-STD-188-220D that is the Interoperability Standard for DMTDs (Digital Messages Transfer Device Subsystems) for voice and data communication in CNR. MIL-STD-188-220D is a candidate for MAC protocol of TMMR which is next radio and has a few constraints to used in TMMR. NAD (Network Access Delay) defined in MIL-STD-188-220D needs time synchronization to avoid collision. However, it is difficult for time synchronization to fit in multi-hop environment. We suggest the enhanced DAP (Deterministic Adaptable Priority)-NAD to prevent conflicts and decrease delays in multi-hop CNR. Simulation results show that the proposed scheme improves the performance in multi-hop CNR networks.

• Journal of Ginseng Research
• /
• v.24 no.1
• /
• pp.35-40
• /
• 2000

The purpose of this study was to investigate the antioxidant activities of water soluble browning reaction products (WS-BRPs) isolated 5\ulcorneron korea red ginseng. Antioxidant activities of WS-BRPs were examined with the various systems. All three WS-BRPs (L, S-1 and S-2) were found to have an ability to linoleic acid, Ox-brain autoxidant, Fe$^{2+}$ ADP/NAD system and cumene hydroperoxide system. Especially, S-2 was had the strongest activity of theses three WS-BRPs to scavenge free radicals such as more effective than S-1, L. MDA determination showed the antioxidant effect on linoleic acid oxidation inhibition ratio of 22.5%, 31.7%, 31.9% and 33.5%, respectivity Especially; Ox-brain autoxidant was strong inhibited activity by 49.52%,62,44,97.54% by addition of various concentration. But three WS-BRPs showed weak inhibitory activity on lipid peroxidation in rat hepatic microsomes induced enzymatically and nonenzymaticallyly