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    STUDIA CHEMIA - Issue no. 1-2 / 1999  
         
  Article:   AMPEROMETRIC STUDY OF THE INHIBITORY EFFECT OF BENZOIC ACID ON A TYROSINASE-MODIFIED PLATINUM ELECTRODE.

Authors:  SARMIZA ELENA STANCA, IONEL CĂTĂLIN POPESCU, LIVIU ONICIU. 		 
       
         
  Abstract:  A new type of tyrosinase (PPO)-modified Pt electrode, based on physical entrapment of the enzyme in agar-agar gel, was constructed and used to investigate the inhibitory effect of benzoic acid on the PPO activity. At an applied potential of -50 mV vs. SCE, the bioelectrode develops a fast, steady state response, linearly correlated with the phenol concentration up to 0.1 mM, with a sensitivity of 4.2 mA.M-1.cm-2. A kinetic interpretation of the amperometric response to phenol recorded in the absence and in the presence of benzoic acid, allowed identifying the inhibition process as a competitive one. The inhibition constant, (1.16  0.01)*10-6 M, and inhibition coefficient, (1.24  0.15) 10-3 M, were found in good agreement with similar data published in the literature.  
         
     
         
         
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