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( Jiao Zhang ),( Yahui Qian ),( Qingbao Ding ),( Ling Ou ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.12
A one-pot process of enzymatic synthesis of deoxythymidine-5`-triphosphate (5`-dTTP) employing whole cells of recombinant Escherichia coli coexpressing thymidylate kinase (TMKase) and acetate kinase (ACKase) was developed. Genes tmk and ack from E. coli were cloned and inserted into pET28a(+), and then transduced into E. coli BL21 (DE3) to form recombinant strain pTA in which TMKase and ACKase were simultaneously overexpressed. It was found that the relative residual specific activities of TMKase and ACKase, in pTA pretreated with 20 mM ethylene diamine tetraacetic acid (EDTA) at 25℃ for 30 min, were 94% and 96%, respectively. The yield of 5`-dTTP reached above 94% from 5 mM deoxythymidine 5`-monophosphate (5`-dTMP) and 15 mM acetyl phosphate catalyzed with intact cells of pTA pretreated with EDTA. The process was so effective that only 0.125 mM adenosine-5`-triphosphate was sufficient to deliver the phosphate group from acetyl phosphate to dTMP and dTDP.
Lane-Change Collision Avoidance Control for Automated Vehicles with Control Barrier Functions
Ding Yang,Zhong Hong,Qian Yahui,Wang Liangmo,Xie Yuan 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.3
In congested street or highway scenarios, such as lane-change in dynamically changing traffic flow situations, the planning and tracking of trajectories for connected and automated vehicles (CAVs) represent some of the most challenging tasks. As an introduction to automated lane-change in CAVs, this paper presents a control Lyapunov function (CLF) approach that follows an optimal desired trajectory while observing the constraints imposed by the control barrier function (CBF) in order to avoid collision with surrounding vehicles. By combining CLF and CBF within the framework of quadratic programs (QP), it allows the implementation to simultaneously track the control objective (represented by the CLF) and satisfy the constraints of the desired state of the system (represented by the CBF). Therefore, it provides the possibility of tracking simultaneously the path of the unmanned vehicle, within the constraints of the surrounding vehicles as well as the surrounding environment. From simulations and comparison results, the controller presented here can perform collision avoidance well and can be used on a real traffic system, which has the advantage of providing faster and more precise lane-change results than another work.
One-pot Process of 2'-Deoxyguanylic Acid Catalyzed by a Multi-enzyme System
Yanyu Li,Qingbao Ding,Ling Ou,Yahui Qian,Jiao Zhang 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.1
2'-Deoxyguanylic acid (deoxyguanosine-5'-monophosphate, dGMP) is a substance required by livingcells that is used extensively in reagents, fine chemicalsand other industrial fields. Traditionally, dGMP is separatedfrom DNA degradation products, which is low-yieldingand time-consuming. Herein, we investigated a novel, onepotmulti-enzymatic cascade reaction to produce dGMP. This reaction involved purine nucleoside phosphorylase(PNPase) and acetate kinase (ACKase) from Escherichiacoli, N-deoxyribosytransferase II (NDT-II) from Lactobacillusdelbrueckii and deoxyguanosine kinase (dGKase) fromBacillus subtilis. During the reaction, the initial guanosinesubstrate was cleaved into guanine and ribose-1-phosphateby PNPase. Then, deoxyguanosine (dGR) was subsequentlyproduced from a reaction between guanine and thymidinecatalysed by NDT-II. Finally, the intermediate dGR wasphosphorylated to dGMP by dGKase and a cytidinetriphosphate (CTP) regeneration system that utilised acetylphosphate via ACKase. A very small amount of CTP wasadded because CTP regeneration was efficient to transfer aphosphate group from acetyl phosphate to dGR. After 12 hof incubation, a maximal dGMP yield of up to 76% wasobtained based on the addition of 5 mM guanosine and 5mM thymidine.