http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
( Rahman Siti Fauziyah ),( Sriramulu Gobikrishnan ),( Natarianto Indrawan ),( Seok Hwan Park ),( Jae Hee Park ),( Kyoung Seon Min ),( Young Je Yoo ),( Don Hee Park ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.10
Levodopa or L-3,4-dihydroxyphenylalanine (L-DOPA) is the precursor of the neurotransmitter dopamine. L-DOPA is a famous treatment for Parkinson`s disease symptoms. In this study, electroenzymatic synthesis of L-DOPA was performed in a three-electrode cell, comprising a Ag/AgCl reference electrode, a platinum wire auxiliary electrode, and a glassy carbon working electrode. L-DOPA had an oxidation peak at 376 mV and a reduction peak at -550 mV. The optimum conditions of pH, temperature, and amount of free tyrosinase enzyme were pH 7, 30℃, and 250 IU, respectively. The kinetic constant of the free tyrosinase enzyme was found for both cresolase and catacholase activity to be 0.25 and 0.4 mM, respectively. A cyclic voltammogram was used to investigate the electron transfer rate constant. The mean heterogeneous electron transfer rate (ke) was 5.8 × 10-4 cm/s. The results suggest that the electroenzymatic method could be an alternative way to produce L-DOPA without the use of a reducing agent such as ascorbic acid.
L-DOPA Synthesis Using Tyrosinase-immobilized on Electrode Surfaces
( Siti Fauziyah Rahman ),( Siramulu Gobikhrisnan ),( Misri Gozan ),( Gwi Taek Jong ),( Don-hee Park ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.6
Levodopa or L-3,4-dihydroxyphenylalanine (L-DOPA) is the direct precursor of the neurotransmitter dopa-mine. L-DOPA is a well-known neuroprotective agent for the treatment of Parkinson`s disease symptoms. L-DOPA was synthesized using the enzyme, tyrosinase, as a biocatalyst for the conversion of L-tyrosine to L-DOPA and an electro-chemical method for reducing L-DOPAquinone, the product resulting from enzymatic synthesis, to L-DOPA. In this study, three electrode systems were used: A glassy carbon electrode (GCE) as working electrode, a platinum, and a Ag/ AgCl electrode as auxiliary and reference electrodes, respectively. GCE has been modified using electropoly-merization of pyrrole to facilitate the electron transfer process and immobilize tyrosinase. Optimum conditions for the electropolymerization modified electrode were a temperature of 30℃ and a pH of 7 producing L-DOPA concentration 0.315 mM. After 40 days, the relative activity of an enzyme for electropolymerization remained 38.6%, respectively.
Rahman, Siti Fauziyah,Min, Kyoungseon,Park, Seok-Hwan,Park, Jae-Hee,Yoo, Jin Cheol,Park, Don-Hee Korean Society for Biotechnology and Bioengineerin 2016 Biotechnology and Bioprocess Engineering Vol.21 No.5
Dopamine, the most important neurotransmitter in the human brain, controls various functions. Dopamine deficiency causes fatal neurological disorders such as Parkinson's disease. Even though various types of electrochemical sensors have been studied to measure dopamine levels, they often have poor selectivity for dopamine due to co-existence of interfering substances (e.g. ascorbic acid). Herein, we aimed to develop a highly sensitive dopamine detection method in the co-existence of ascorbic acid, a major interfering substance in real sample by designing an electrochemically pretreated and activated carbon/tyrosinase/Nafion<TEX>$^{(R)}$</TEX>-modified GCE as an amperometric dopamine biosensor. To maximize the biosensor performance, pH, volume of Nafion<TEX>$^{(R)}$</TEX>, and scan rate were optimized. This electrochemically pretreated and activated carbon/tyrosinase/Nafion<TEX>$^{(R)}$</TEX>-modified GCE could detect as low as <TEX>$50{\mu}M$</TEX> of dopamine with a wide linear range (<TEX>$50{\sim}1,000{\mu}M$</TEX>) within a few seconds. In addition, it had a sensitivity of <TEX>$103mAM/cm^2$</TEX>, which was higher than all previously reported tyrosinase-based dopamine biosensors. In addition, interference effect caused by 4 mM of ascorbic acid was negligible in the co-existence of 1 mM of dopamine. Consequently, this electrochemically pretreated and activated carbon/tyrosinase/Nafion<TEX>$^{(R)}$</TEX>-modified GCE might be applicable as amperometric biosensor for selective detection of dopamine in real samples with interfering substances.
Don-Hee Park,Siti Fauziyah Rahman,민경선,박석환,Jae-Hee Park,JIN CHEOL YOO 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.12
Dopamine (3,4-dihydroxylphenyl ethylamine) is the most significant neurotransmitter in the human nervous system. Abnormal dopamine levels cause fatal neurological disorders, and thus measuring dopamine level in actual samples is important. Although electrochemical methods have been developed for detecting dopamine with high accuracy, certain substances (e.g., ascorbic acid) in actual samples often interfere with electrochemical dopamine detection. We developed tyrosinase-based dopamine biosensor with high sensitivity and selectivity. An electrochemically pretreated tyrosinase/multi-walled carbon nanotube-modified glassy carbon electrode (tyrosinase/MWNT/GCE) was prepared as an amperometric biosensor for selective dopamine detection. For optimizing the biosensor performance, pH, temperature, and scan rate were investigated. The electrochemically pretreated tyrosinase/MWNT/GCE exhibited not only the highest sensitivity (1,323mAM−1cm−2) compared to previously reported tyrosinase-based dopamine sensors, but also good long-term stability, retaining 90% of initial activity after 30 days. Additionally, ascorbic acid, a major interfering substances, was not oxidized at the potential used to detect dopamine oxidation, and the interfering effect of 4mM ascorbic acid was negligible when monitoring 1mM dopamine. Consequently, the electrochemically pretreated tyrosinase/MWNT/GCE is applicable for highly selective and sensitive dopamine detection in actual samples including interfering substances, thereby extending the practical use to monitor and diagnose neurological disorders.