Lecture Notes Review: Biosensors and Protein Structure

Flashcards covering bacteria-based, mammalian cell-based, and enzyme-based biosensors, including details on protein structure, enzyme kinetics, and specific biotechnology applications from the lecture notes.

What is a common application of bacteria-based biosensors?

Water quality monitoring.

What is the function of a stress-inducible promoter in a bacteria-based biosensor?

It activates a stress response, causing bacteria to 'flash' a warning.

How does a semi-specific biosensor compare to a specific one?

A specific biosensor detects one ligand, while a semi-specific one can detect a class of compounds or multiple ligands.

What is the purpose of a negative control like M2G in biosensors?

It helps confirm the specificity or baseline response.

What concept do sensors-enabled continuous, unattended real-time monitoring devices implement?

Urban/industrial monitoring.

How are bacteria typically immobilized for detection of endocrine disruptors in urban waterways?

On an electrode.

What kind of cells are often engineered to produce electric current upon detection in biosensors?

Cells engineered to produce electric current on detection.

Do mammalian cell-based biosensors only offer specific detection?

No, they can be specific or semi-specific.

What is an example of a specific ligand mentioned for mammalian cell-based biosensors?

4-HT, as a model endocrine disruptor.

What signaling process is activated by HRH2 (histamine receptor) in an allergy profiler?

Signaling by reporter-protein.

What are enzymes known for in the context of biosensors?

Highly selective biocatalysts that accelerate chemical reactions, allowing for relatively fast detection.

In enzyme-based sensors, what two roles can an analyte play?

Either an enzyme substrate or an enzyme inhibitor.

How is a signal generated in enzyme-based sensors?

The reaction product is used to generate a signal.

What does the enzyme symbol on a diagram represent?

A complex protein molecule.

What is the main component of an enzyme biosensor that functions as a bioreceptor for the analyte?

An enzyme, e.g., GOX in a glucose sensor.

What are proteins structurally?

Linear co-polymers of twenty amino acids.

What are the common functional groups found at the ends of amino acids?

Alpha-amino (NH2) and alpha-carboxyl (COOH) groups.

What is a peptide bond?

A covalent bond formed between the alpha-carboxyl group of one amino acid and the alpha-amino group of another.

What is the N-terminus of a polypeptide?

The amino (N-terminal) end.

What is the C-terminus of a polypeptide?

The carboxyl (C-terminal) end.

What is the primary structure of a protein?

The sequence of amino acids in a polypeptide chain.

What factors make NH2, COOH groups, and side chains useful for immobilization of biomolecules?

They contain very reactive functional groups.

What information does secondary structure define?

The folding/conformation of protein segments via a pattern of H-bonding.

What information does tertiary structure define?

The assembly of different elements of secondary structure, forming the overall 3D shape.

What information does quaternary structure define?

The number and arrangement of subunits in a multi-subunit protein.

How is an alpha-helix stabilized?

By hydrogen bonds between the CO group of residue n and the NH group of residue n+4.

Describe the key characteristic of beta-strands.

Polypeptide backbones that are almost fully extended.

How are beta-strands typically depicted in diagrams?

By broad arrows pointing in the direction of the carboxyl-terminal.

What is the difference between antiparallel and parallel beta-strands?

In antiparallel, the N-terminus of one strand is adjacent to the C-terminus of another; in parallel, they are directionally aligned.

What structural element is formed when many beta-strands come together?

Beta-sheets.

What are distinct structural domains in proteins referred to as?

Fundamental units of tertiary structure.

Why is maintaining a protein's unique tertiary/quaternary structure important for its function?

Proteins are only active if their unique structure is maintained.

What types of interactions help maintain protein structure?

Covalent and non-covalent interactions (e.g., H-bonds, hydrophobic interactions, disulfide bonds).

In water-soluble proteins, where are hydrophobic amino acids typically located?

Shielded from the aqueous environment in the interior of the protein.

What is critical for maintaining the integrity of the protein fold?

Hydrophobic interactions in the core.

What properties make enzymes useful in biosensors?

Sensitivity, selectivity, stability/reproducibility, ease of integration with transducers, and signal amplification.

What are luciferases?

Enzymes that convert energy to light.

What is the overall enzymatic reaction catalyzed by bacterial luciferases in biosensing?

FMNH2 + RCHO + O2 → FMN + RCOOH + H2O + light.

What are two applications mentioned for using ATP as an analyte with luciferase for hygiene monitoring?

To determine early stage cell breaking and to look for bacteria.

How does the Lumitester improve hygiene monitoring compared to traditional methods?

It measures both ATP and AMP, offering better sensitivity and a more stable light signal, and delivers results in minutes.

What are the three main steps in a real-time detection system for airborne microorganisms?

Condensation system to concentrate aerosol, ATP extraction from captured bacteria, and bioluminescence detection of ATP.

What is the dynamic range of ATP detection in the airborne detection biosensor example?

From 10^-12 to 10^-3 M.

How can a pH electrode be modified to create a glucose enzyme electrode?

By immobilizing glucose oxidase (GOX) between two membranes on the tip.

What reaction does glucose oxidase catalyze that allows for pH detection?

Glucose + O2 + H2O → Gluconic acid + H+ + H2O2.

What enzyme is present in banana skin that can be used in a plant-based biosensor?

Polyphenol Oxidase (PPO).

What type of enzyme catalyzes the hydrolysis of P-O bonds in organophosphorus neurotoxins?

Organophosphate hydrolases (OPAA).

What common biological activity do sarin, paraoxon, and dichlorvos share?

They are powerful inhibitors of Acetylcholinesterase (AChE).

What is the biological function of Acetylcholinesterase (AChE)?

It breaks down acetylcholine, which is involved in neurotransmission.

How do AChE-based biosensors detect analytes like warfare agents or pesticides?

By measuring the inhibition of the enzyme's activity by the agent being detected.

What three enzymes are used in the foldable paper-based biosensor for pesticide detection that links to a smartphone?

Acetylcholinesterase (AChE), Choline Oxidase (ChOx), and Horseradish Peroxidase (HRP).