theme 4 screening

Question 1

What is the aim of High Throughput Screening (HTS)?

Answer 1

To take a wide range of molecules and assess their activity in an assay against a target.

Question 2

What are the key characteristics needed for an HTS assay?

Answer 2

Reproducible, sensitive, simple, robust, reliable.

Question 3

What types of biological activities can be assessed in HTS assays?

Answer 3

Agonism, antagonism, inhibition.

Question 4

What are the two key types of assays in HTS?

Answer 4

• Target-based
• Phenotypic

Question 5

What is a target-based assay?

Answer 5

An assay where the target is known, including biochemical, biophysical, and cellular assays.

Question 6

What is a phenotypic assay?

Answer 6

An assay that assesses the cell as a whole, where the target does not need to be known.

Question 7

What are the four key methods of readout in HT assays?

Answer 7

• Absorption
• Photoluminescence
• Chemoluminescence
• Radioluminescence

Question 8

What is a homogeneous assay configuration?

Answer 8

An assay where no separation of components is needed to obtain results (‘mix and read’).

Question 9

What is a non-homogeneous assay configuration?

Answer 9

An assay where separation of components via filtration/washing is required to obtain results.

Question 10

What is Scintillation Proximity in HTS?

Answer 10

A radiometric analysis of activity that does not require washing steps or separation of components.

Question 11

What biophysical techniques are increasingly applied in early drug discovery?

Answer 11

• Crystallography
• NMR
• Surface Plasmon Resonance (SPR)
• Isothermal Titration Calorimetry (ITC)
• Differential Scanning Fluorimetry
• Mass Spectrometry

Question 12

What is fragment-based screening?

Answer 12

A method that utilizes smaller compounds with lower molecular mass that can be combined to create lead molecules.

Question 13

What are the three main methods of using fragments to form lead molecules?

Answer 13

• Fragment evolution
• Fragment linking
• Fragment self-assembly

Question 14

What is scaffold hopping?

Answer 14

A method that discovers structurally novel compounds by replacing parts of the scaffold to improve properties.

Question 15

What are the two broad approaches in virtual libraries?

Answer 15

• Ligand guided
• Receptor guided

Question 16

What does the signal to background measure assess in HTS?

Answer 16

Signal to background = mean of positive control signal / mean of background signal.

Question 17

What is an acceptable value for the signal to noise ratio in HTS?

Answer 17

A value of 10.

Question 18

What is the Z’ factor used for in HTS?

Answer 18

To evaluate the overall performance of the HTS assay.

Question 19

What should the Z’ factor value be to indicate a good assay?

Answer 19

Close to 1 but above 0.4.

Question 20

What is the purpose of developing a screening cascade?

Answer 20

To narrow molecules from hits to actives.

Question 21

Fill in the blank: The nature of biological material can be either _______ or whole cells.

Answer 21

cell-free systems

Question 22

True or False: Whole cell assays provide a simpler system than cell-free assays.

Answer 22

False

Question 23

What is the purpose of identifying high quality hits during screening?

Answer 23

To eliminate false positives and prioritize true positives.

Question 24

What is meant by false positives in screening?

Answer 24

Signals that indicate hits but do not correspond to actual active compounds.