17 Questions
What happens to the ECL signal when a stem-loop of the ECL probe is converted into a linear double-helix configuration in the presence of target ss-DNA?
Decreases
Which enzyme is commonly used as a sensor biorecognition element for urea determination/monitoring in medical and environmental applications?
Urease
In the first transduction mechanism mentioned, what product is formed when glucose oxidase catalyzes the oxidation of glucose?
Gluconolactone + H2O2
What type of prosthetic group is utilized by glucose dehydrogenase in the second transduction mechanism for glucose biosensors?
NAD+
Which enzyme is commonly used in glucose biosensors as the recognition element for catalyzing glucose oxidation?
Glucose dehydrogenase
Which of the following measurable reaction products arise from the catalytic process involving catalytic enzyme-based sensor recognition elements?
Protons
What is the substrate used in the biosensor for the enzyme alkaline phosphatase (ALP)?
PNPP
Which type of receptor is responsible for the recognition in the biosensor?
Cell receptor
What disrupts normal physiological function, leaving a detectable signature on the cells?
Pathogen
In the biosensor system, what reduces a yellow water-soluble reaction product that absorbs light at 405 nm?
Enzyme ALP
Which enzyme is used in the biosensor system for detection?
Alkaline phosphatase (ALP)
Which type of biosensor uses an antigen-antibody reaction to effect a transducer signal change?
Immunosensor
What serves as the electron sinks in the electrochemical detection approach of glucose biosensors?
Inorganic redox couples
What does the quinoprotein glucose dehydrogenase use to oxidize alcohols and amines in the alternative transduction scheme?
PQQ
What is the problem with immunosensors compared to enzyme-based sensors?
They only involve a binding reaction with the antigen
Which component is essential for glucose oxidation in the reaction catalyzed by glucose dehydrogenase?
PQQ(ox)
What are some examples of electrochemical mediators used in the detection approach of glucose biosensors?
Organic dyes like Prussian Blue
Study Notes
Electrochemical Detection
- Glucose dehydrogenase is used in an electrochemical detection approach where the product (hydrogen peroxide or NADH) is detected by an electrochemical mediator.
- Examples of electrochemical mediators include organic dyes (e.g. Prussian Blue) and inorganic redox couples that serve as electron sinks.
Glucose Dehydrogenase Mechanisms
- The 1st mechanism uses glucose dehydrogenase to oxidize glucose to gluconolactone with NAD+ as a cofactor, producing NADH and H+.
- The 2nd mechanism uses glucose dehydrogenase with an orthoquinone cofactor (PQQ) to oxidize glucose to gluconolactone, producing PQQ(red).
Recognition Receptors
- Antibody-based recognition involves an antigen-antibody reaction to effect a transducer signal change.
- Enzyme-based recognition uses catalytic enzymes, producing measurable products such as protons, electrons, light, and heat.
- Examples of enzyme-based recognition elements include urease, glucose oxidase, and glucose dehydrogenase.
Glucose Biosensors
- Glucose biosensors use glucose oxidase to catalyze the oxidation of glucose to gluconolactone, producing H2O2.
- The H2O2 is then detected electrochemically.
- Alternative glucose biosensors use glucose dehydrogenase, producing NADH instead of H2O2.
Cell Receptors on Biosensors
- Cell receptors on biosensors use mammalian cells and alkaline phosphatase (ALP) to detect pathogens/toxins.
- The ALP catalyzes the conversion of PNPP to a yellow, water-soluble product that absorbs light at 405 nm.
- Pathogen-induced cellular damage produces a detectable signature of the pathogen.
Explore the dominant detection approach in biochemical reactions, which involves electrochemical detection of products like hydrogen peroxide or NADH using organic dyes or inorganic redox couples. Learn about the alternative transduction scheme involving quinoprotein glucose dehydrogenase.
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