title: An enzyme electrode for amperometric measurement of D-amino acid.
abstract: A carbon paste enzyme electrode has been developed for measurement of D-amino acids that employs a fatty acid modified FAD to prevent leaching of this essential cofactor to the surrounding aqueous environment and which serves as an enzyme stabilizing agent. The lower limit of detection is at least 10(-4) M and the electrode has a linear range of 10(-4) to 3 x 10(-3) M and a response time of 180 s. Twenty L-amino acids were tested and none of them elicited responses when electrodes were exposed to 0.5 mM concentration increases over a baseline level. On the other hand, some response was observed when exposed to 18 of 20 D-amino acids varying from 2 to 200% of the corresponding D-alanine response. Electrodes were shown to have longevities of over 30 days while maintaining 85% of their original sensitivity. Electrodes showed activity over a pH of 6.2-11.7 with a maximum at 9.2 and over temperatures of 10-47 degrees C with a maximum at 37 degrees C.
authors.affiliation: School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164-2710, USA. xiaoxi@wsu.edu
authors.forename: Xiaoxi
authors.initials: X
authors.lastname: Wu
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Van Wie
authors.forename: David A
authors.initials: DA
authors.lastname: Kidwell
mesh_terms: D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D002244:Carbon / Q000737:chemistry; D003605:D-Amino-Acid Oxidase / Q000737:chemistry*; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004789:Enzyme Activation; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000032:analysis / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005227:Fatty Acids / Q000737:chemistry*; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D009824:Ointments; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013696:Temperature
chemical_list: D000596:Amino Acids; D004800:Enzymes, Immobilized; D005227:Fatty Acids; D009824:Ointments; D002244:Carbon; D003605:D-Amino-Acid Oxidase