• Title/Summary/Keyword: NTP

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Phenotypic Suppression of Rad53 Mutation by CYC8 (CYC8에 의한 rad53 돌연변이의 표현형 억제에 대한 연구)

  • Park, Kyoung-Jun;Choi, Do-Hee;Kwon, Sung-Hun;Kim, Joon-Ho;Bae, Sung-Ho
    • Korean Journal of Microbiology
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    • v.46 no.2
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    • pp.122-126
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    • 2010
  • RAD53 functions as an effector kinase of checkpoint pathways in Saccharomyces cerevisiae, which plays a central role to regulate many downstream cellular processes in response to DNA damage. It also involves in transcriptional activation of various genes including RNR genes which encode the key enzyme required for dNTP synthesis. In this study, we identified CYC8 as a suppressor for the hydroxyurea sensitivity of $rad53{\Delta}$ mutation. $Rad53{\Delta}$ mutant transformed with a multi-copy plasmid containing CYC8 showed increased hydroxyurea resistance. In contrast, TUP1 which forms a complex with CYC8 did not function as a suppressor. In the case of mutations, both $cyc8{\Delta}$ and $tup1{\Delta}$ suppressed hydroxyurea sensitivity of $rad53{\Delta}$. Since CYC8 can propagate as a prion in yeast, overexpression of CYC8 induced misfolding of the normal CYC8 proteins, resulting in dominant cyc8-phenotype. Therefore, it is suggested that CYC8 can act as a multi-copy suppressor due to its prion property. It was observed that the levels of RNR transcription were increased in the yeast strains containing either multi-copies of CYC8 gene or $cyc8{\Delta}$ mutation, suggesting that the increased level of RNR will elevate the intracellular pools of dNTPs, which, in turn, suppress the phenotype of $rad53{\Delta}$ mutation.

CoAP-based Time Synchronization Algorithm in Sensor Network (센서 네트워크에서의 CoAP 기반 시각 동기화 기법)

  • Kim, Nac-Woo;Son, Seung-Chul;Park, Il-Kyun;Yu, Hong-Yeon;Lee, Byung-Tak
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.3
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    • pp.39-47
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    • 2015
  • In this paper, we propose a new time synchronization algorithm using CoAP(constrained-application protocol) in sensor network environment, which handles a technique that synchronizes an explicit timestamp between sensor nodes not including an additional module for time-setting and sensor node gateway linked to internet time server. CoAP is a standard protocol for sensor data communication among sensor nodes and sensor node gateway to be built much less memory and power supply in constrained network surroundings including serious network jitter, packet losses, etc. We have supplied an exact time synchronization implementation among small and cheap IP-based sensor nodes or non-IP based sensor nodes and sensor node gateway in sensor network using CoAP message header's option extension. On behalf of conventional network time synchronization method, as our approach uses an exclusive protocol 'CoAP' in sensor network, it is not to become an additional burden for synchronization service to sensor nodes or sensor node gateway. This method has an average error about 2ms comparing to NTP service and offers a low-cost and robust network time synchronization algorithm.

Purification, Characterization and Cellular Localization of Klebsiella aerogenes UreG Protein

  • Lee, Mann-Hyung
    • Biomolecules & Therapeutics
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    • v.3 no.4
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    • pp.311-315
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    • 1995
  • The K. aerogenes ureal gene product was previously shown to facilitate assembly of the crease metallocenter (Lee, M. H., Mulrooney, S. B., Renner, M. J., Markowicz, Y., and Hausinger, R. P. (1992) J. Bacteriol. 174, 4324-4330). UreG protein has now been purified and characterized. Although the protein is predicted to possess a putative NTP-binding P-loop motif, equilibrium dialysis studies showed negative results. Immunogold electron microscopic studies using polyclonal antibodies directed against UreG protein confirm that UreG is located in the cytoplasm as predicted in the DNA sequence.

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HIV-1 RT (reverse transcriptase) 저해제에 대한 내성 발현 기전

  • 임광진
    • Proceedings of the Korean Society of Applied Pharmacology
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    • 1995.10a
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    • pp.67-69
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    • 1995
  • reverse transcription은 AIDS를 일으킨다고 알려진 바이러스인 HIV-1의 번식에는 필수적이나 인체 세포에는 필수적이 아니기에 이 단계를 표적으로 하는 AIDS 치료제가 우선적으로 개발되었다. 그 단계에 필요한 효소가 바이러스에 의해 만들어진 RT이며 이 효소의 작용을 저해하는 nucleoside 유도체들인 AZT, DDC, DDI 들이 현재 AIDS 환자의 치료에 사용되고 있다. 이들 nucleoside 유도체들은 세포안으로 들어가 triphosphate 형태로 변화된 후 dNTP와 상경적으로 경쟁하며 합성 중인 바이러스의 DNA에 들어가 DNA의 합성을 정지시켜 바이러스의 증식을 억제한다. 그러나, 이들 nucleoside 유도체들은 치료용량에서 심한 독성을 나타낼 뿐만 아니라 장기 투여시 내성을 나타내는 바이러스가 생겨나 AIDS의 치료를 불가능하게 하고 있다.

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Parameters Affecting Polymerase Chain Reaction in RAPD Analysis of Pleurotus spp. (느타리버섯속(屬)의 DNA 다형성분석(多型性分析)에 영향(影響)을 미치는 PCR 조건(條件))

  • Kim, Beom-Gi;Jeong, Mi-Jeong;Lee, Chang-Soo;Lee, Hee-Kyung;Yoo, Young-Bok;Ryu, Jin-Chang
    • The Korean Journal of Mycology
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    • v.23 no.3 s.74
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    • pp.202-208
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    • 1995
  • This study describes the effects of several components on PCR amplification used for RAPD. We used different concentrations of reaction components to obtaine discrete and reproducible PCR products from Pleurotus cornucopiae. The optimum concentrations of reaction components were found to be 80 ng of template DNA, 30 pmole of 10-mer primer, $200\;{\mu}M$ dNTP, 2mM $MgCl_2$, 50 mM KCl, 10 mM Tris-HCl(pH 9.0), 0.1% Triton X-100, 1.5 unit of Taq DNA polymerase (promega) in $50\;{\mu}l$ reaction volume. The optimum annealing temperature was $35^{\circ}C$. These results proved to be valuable for characterization of Pleurotus spp.

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Response System for DRDoS Amplification Attacks (DRDoS 증폭 공격 대응 시스템)

  • Kim, Hyo-Jong;Han, Kun-Hee;Shin, Seung-Soo
    • Journal of Convergence for Information Technology
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    • v.10 no.12
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    • pp.22-30
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    • 2020
  • With the development of information and communication technology, DDoS and DRDoS continue to become security issues, and gradually develop into advanced techniques. Recently, IT companies have been threatened with DRDoS technology, which uses protocols from normal servers to exploit as reflective servers. Reflective traffic is traffic from normal servers, making it difficult to distinguish from security equipment and amplified to a maximum of Tbps in real-life cases. In this paper, after comparing and analyzing the DNS amplification and Memcached amplification used in DRDoS attacks, a countermeasure that can reduce the effectiveness of the attack is proposed. Protocols used as reflective traffic include TCP and UDP, and NTP, DNS, and Memcached. Comparing and analyzing DNS protocols and Memcached protocols with higher response sizes of reflective traffic among the protocols used as reflective traffic, Memcached protocols amplify ±21% more than DNS protocols. The countermeasure can reduce the effectiveness of an attack by using the Memcached Protocol's memory initialization command. In future studies, various security-prone servers can be shared over security networks to predict the fundamental blocking effect.

Attack Scenarios and Countermeasures using CoAP in IoT Environment (IoT기기에서 SSDP 증폭 공격을 이용한 공격기법 및 대응 방안)

  • Oh, Ju-Hye;Lee, Keun-Ho
    • Journal of the Korea Convergence Society
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    • v.7 no.4
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    • pp.33-38
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    • 2016
  • DDoS attack has been continuously utilized that caused the excessively large amount of traffic that network bandwidth or server was unable to deal with paralyzing the service. Most of the people regard NTP as the biggest cause of DDoS. However, according to recently executed DDoS attack, there have been many SSDP attack in the use of amplified technique. According to characteristics of SSDP, there is no connection for making a forgery of source IP address and amplified resources feasible. Therefore, it is frequently used for attack. Especially, as it is mostly used as a protocol for causing DDoS attack on IoT devices that constitute smart home including a wireless router, media server, webcam, smart TV, and network printer. Hereupon, it is anticipated for servers of attacks to gradually increase. This might cause a serious threat to major information of human lives, major government bodies, and company system as well as on IoT devices. This study is intended to identify DDoS attack techniques in the use of weakness of SSDP protocol occurring in IoT devices and attacking scenario and counter-measures on them.

A Study of Optium Condition of RAPD for the Analysis of Genetic Characteristics by Autumn Leaf Color of Zelkova serrata (느티나무(Zelkova serrata)단풍의 유전적 특성분석을 위한 RAPD 적정 조건 구명에 관한 연구)

  • Choi, Byoung Kon;Bang, Kwang Ja
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.7 no.5
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    • pp.94-99
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    • 2004
  • This study was carried out to find out what is the optimum conditions for RAPD of Zelkova serata. We changes the factors what affect to PCR band patterns, as a result, we established the optimum conditions as follows; template DNA 100mg, Primer 0.25uM, dNTP 100mM, Taq polymerase 1.0u, and total reaction volume was filled up to 10uL with distilled water. As the amount of primers went higher, PCR reaction rates were lowered. This reason was cause by exhaustion of primers during initial reaction. The amount of dNTP didn't showed noticable differtations between the range, but the optimum amount was 100mM for efficiency. Taq polymerase 1.0 unit was the best in the range. As the concentration of polymerase were increased, many non-specific bands were appeared, In primer selection, most Openron Random Primers are amplified in this experiment. The primers GC contents were 60, and set A, B, C, D, E, X were tested. Thermal cycler(ASTEC PC808, Japan) condition was, $95^{\circ}C$, 5min, initial denaturation, $94^{\circ}C$, 20sec, denaturation, $37^{\circ}C$, 40sec, annealing, $72^{\circ}C$, 1min, extention, 45cycle repeated and final extention $72^{\circ}C$10min.

A study on the detection of DDoS attack using the IP Spoofing (IP 스푸핑을 통한 DDoS 공격 탐지 방안에 대한 연구)

  • Seo, Jung-Woo;Lee, Sang-Jin
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.25 no.1
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    • pp.147-153
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    • 2015
  • Since the DoS(Denial of Service) attack is still an important vulnerable element in many web service sites, sites including public institution should try their best in constructing defensive systems. Recently, DDoS(Distributed Denial of Service) has been raised by prompting mass network traffic that uses NTP's monlist function or DoS attack has been made related to the DNS infrastructure which is impossible for direct defense. For instance, in June 2013, there has been an outbreak of an infringement accident where Computing and Information Agency was the target. There was a DNS application DoS attack which made the public institution's Information System impossible to run its normal services. Like this, since there is a high possibility in having an extensive damage due to the characteristics of DDoS in attacking unspecific information service and not being limited to a particular information system, efforts have to be made in order to minimize cyber threats. This thesis proposes a method for using TTL (Time To Live) value in IP header to detect DDoS attack with IP spoofing, which occurs when data is transmitted under the agreed regulation between the international and domestic information system.