Katrin Streffer

Universität Potsdam, Potsdam, Brandenburg, Germany

Are you Katrin Streffer?

Claim your profile

Publications (5)17.98 Total impact

  • Bioelectrochemistry: Fundamentals, Experimental Techniques and Applications, 04/2008: pages 219 - 248; , ISBN: 9780470753842
  • [Show abstract] [Hide abstract]
    ABSTRACT: Properties of Streptomyces antibioticus tyrosinase and the implementation of the enzyme in a biosensor for the detection of phenolic compounds were investigated. The tyrosinase from S. antibioticus is a monomer and has a molecular weight of 30.6 kD. The specific activity is about 5 U/mg with catechol as substrate and 1225 U/mg with l-dopa as substrate. The activity of tyrosinase upon long-term storage is best maintained in buffer at temperatures of −80 or +4°C. Storage at −18°C, with or without glycerol, resulted in quick enzyme inactivation.For the construction of the sensor bi-enzymatic substrate recycling was exploited. Quinoprotein glucose dehydrogenase (GDH) and tyrosinase were immobilised in polyvinyl alcohol and coupled to a Clark-type oxygen electrode that allowed for monitoring of the oxygen consumption during catechol conversion. This design of the sensor facilitates the determination of phenolic compounds in the nanomolar range. The lower limit of detection for l-dopa, dopamine, and adrenalin was 5 nM.
    Analytica Chimica Acta 01/2001; 427(2):201-210. DOI:10.1016/S0003-2670(00)01040-0 · 4.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A substrate regenerating bienzyme sensor was used to measure a variety of organic and inorganic inhibitors with high sensitivity. The bienzyme system consists of the two cooperating enzymes, cytosolic quinoprotein glucose dehydrogenase and mushroom tyrosinase. The cooperation takes place on the substrate/product level. Under kinetic control, compounds that affect one of the enzymes can be detected with high sensitivity.For the construction of the sensor, the enzymes were immobilized in polyvinyl alcohol, coupled to a Clark-type oxygen electrode and the oxygen consumption was monitored during catechol conversion. In this way, carboxylic acids, kojic acids, inorganic ions and thiourea derivatives were studied.Theoretical considerations reveal the relationship between amplification gain and inhibitor concentration.
    Analytica Chimica Acta 04/1998; DOI:10.1016/S0003-2670(97)00690-9 · 4.52 Impact Factor
  • Biosensors & Bioelectronics 05/1996; 11(8). · 6.45 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mushroom tyrosinase and glucose dehydrogenase from Acinetobacter calcoaceticus were immobilized in poly(vinyl)alcohol membranes and coupled with a Clark-type oxygen electrode to give a substrate (analyte) regenerating cycle for monitoring of nanomolar concentrations of phenolic compounds. In this way the response for catechol, phenol, p-cresol, p-chlorophenol and p-acetamidophenol was amplified by a factor of 450, 300, 240, 150, and 140, respectively. The resulting detection limit for catechol and phenol is 0·6 nmol dm−3 and 0·9 nmol dm−3, respectively. The measuring linear range for phenol obtained by the amplified electrode extends from 1 to 400 nmol dm−3. The comparison with the chemical (ascorbic acid) regeneration of the phenolic compounds demonstrates the efficiency of the enzymatic procedure. The biosensor can be used for monitoring of phenolic compounds in environmental or industrial samples.
    Journal of Chemical Technology & Biotechnology 01/1996; 65(1):39 - 44. DOI:10.1002/(SICI)1097-4660(199601)65:1<39::AID-JCTB377>3.0.CO;2-Q · 2.49 Impact Factor