Medicinal Chemistry Chapter 17 Key

Type: multiple choice Title: Chapter 17 - Question 01 01) Which of the following operations or calculations would generally be carried out using quantum mechanics? Feedback: Quantum mechanics is used for the calculation of partial atomic charges. The other calculations or procedures are generally done using molecular mechanics incorrect a.# Energy minimisation. incorrect b.# Identifying stable conformations. Correct c.# Partial atomic charges. incorrect d.# Energy calculations for specific conformations. END OF QUESTION Type: multiple choice Title: Chapter 17 – Question 02 02) Which of the following software programs is not used for drawing 2D chemical structures? Feedback: Chem3D is a general molecular modelling software program. incorrect a.# ChemDraw. incorrect b.# ChemWindow. Correct c.# Chem3D. incorrect d.# Isis/Draw. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 03 03) Which of the following software programs is not dedicated to the creation of 3D chemical models? Feedback: DOCK was one of the early software programs used for docking a ligand to a binding site. Correct a.# DOCK. incorrect b.# Alchemy. incorrect c.# Hyperchem. incorrect d.# Discovery Studio Pro. END OF QUESTION Type: multiple choice Title: Chapter 17 – Question 04 04) Which of the following is associated with conformational searching? Feedback: The Monte Carlo method is used in searching for different conformations of a molecule. LUDI is a software program used in de novo drug design. DOCK is used in docking molecules into binding site. CoMFA is used in 3D QSAR. incorrect a.# LUDI. incorrect b.# DOCK. Correct c.# Monte Carlo method. incorrect d.# CoMFA. END OF QUESTION Type: multiple choice Title: Chapter 17 – Question 05 05) Molecular dynamics can be used to search for different conformations of a molecule. Which of the following statements is false? Feedback: Measurements are calculated after each femtosecond of movement. incorrect a.# Correct b.# incorrect c.# incorrect d.# A variety of different conformations are generated by 'heating' the molecule to 900K. The position and velocity of each atom is measured after each nanosecond of movement The programme treats each atom as a moving sphere Each atom is only allowed to move a fraction of a bond length between each cycle of calculations END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 06 06) Which of the following statements regarding molecular mechanics is untrue? Feedback: Molecular mechanics involves the use of equations that follow the laws of classical physics. It treats atoms as spheres and bonds as springs. incorrect a.# It treats atoms as spheres. Correct b.# It treats bonds as rigid features. incorrect c.# It is a molecular modelling computational method. incorrect d.# It uses equations that obey the laws of classical physics. END OF QUESTION Type: multiple choice Title: Chapter 17- Question 07 07) Which of the following statements regarding quantum mechanics is untrue? Feedback: In quantum mechanics the assumption is made that nuclei are motionless. incorrect a.# It uses quantum physics to calculate molecular properties. Correct b.# incorrect c.# incorrect d.# It makes the assumption that nuclei are moving independently of each other It makes the assumption that electrons move independently of each other. There are two broad categories - ab initio and semi-empirical END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 08 08) Which of the following statements is true? Feedback: Energy minimisation finds a stable conformation for a molecule, but not necessarily the most stable conformation. Bond lengths and bond angles are changed during energy minimisation, but torsion angles are also changed. The energy minimisation stops when there is little change in energy between one structure and the next – corresponding to a stable conformation. Correct a.# Energy minimisation is carried out using molecular mechanics. incorrect b.# Energy minimisation is used to find the most stable conformation for a molecule. incorrect c.# incorrect d.# Energy minimisation is carried out by varying only bond angles and bond lengths. Energy minimisation stops when a structure is formed with a much greater stability than the previous one in the process. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 09 09) What is meant by a local energy minimum in conformational analysis? Feedback: The local energy minimum corresponds to the first stable structure which is formed when energy minimisation is carried out. It may or may not be the most stable conformation. The most stable conformation of a structure is the global energy minimum. incorrect a.# It is a localised region of a molecule which is free of steric strain. incorrect b.# It is the most stable conformation of a structure. incorrect c.# Correct d.# It is the initial structure that is formed when a 3D model is created, prior to energy minimisation. It is the closest stable conformation to the starting structure. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 10 10) What is meant by a global energy minimum in conformational analysis? Feedback: The global energy minimum corresponds to the most stable conformation of a molecule. The closest stable conformation to the starting structure describes a local energy minimum which corresponds to the first stable structure that is formed when energy minimisation is carried out. incorrect a.# It is a localised region of a molecule which is free of steric strain. Correct b.# It is the most stable conformation of a structure. incorrect c.# incorrect d.# It is the initial structure that is formed when a 3D model is created, prior to energy minimisation. It is the closest stable conformation to the starting structure. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 11 11) The following diagram shows the energy of the starting structure prior to energy minimisation. What is the likely result of energy minimisation? Feedback: Energy minimisation would be carried out and the structure would be altered to a stable conformation. The most stable conformation would be Z, but there is no way that the software programme can predict that and so there is an equal likelihood of the structure ending up as X or Z after energy minimisation. incorrect a.# Energy minimisation would have no effect and the structure would remain at position Y. incorrect b.# The structure would be energy minimised and give the most stable structure corresponding to position Z. Correct c.# The structure would be energy minimised and give a final structure corresponding to either position X or Z. incorrect d.# Energy minimisation would be carried out and the final structure would correspond to position X. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 12 12) Which of the following statements regarding structural overlays is false? Feedback: The calculation continues until the root mean square distance is a minimum value. incorrect a.# incorrect b.# incorrect c.# Correct d.# The two structures to be overlaid should both be in their active conformations. Usually specific pairs of atoms are chosen (one from each molecule) to allow the overlay to take place. The fitting process normally involves both molecules being rigid and not changing conformation during the overlay. The overlay is carried out until a maximum value of the root mean square distance between all the atom pairs is achieved. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 13 13) Which of the following statements is true? Feedback: The active conformation is the conformation that the drug adopts when it binds to the target binding site and this does not necessarily equate with the most stable conformation. Most drugs do not react with their target binding site. Instead, they form intermolecular bonds. Therefore, the active conformation does not need to be a reactive conformation. Conformational analysis will assess the relative stabilities of different conformations, but it cannot predict the active conformation. Correct a.# The most stable conformation of a drug is not necessarily the active conformation. incorrect b.# incorrect c.# incorrect d.# The active conformation is the most reactive conformation of a structure. The active conformation is the conformation adopted by a target binding site when it binds a drug. The active conformation can be determined by conformational analysis. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 14 14) Which of the following statements is not true of cyclic structures? Feedback: Cyclic, rigid structures are generally more difficult to synthesise than acyclic simpler molecules. incorrect a.# They are normally more rigid than acyclic structures. incorrect b.# They have fewer possible conformations. incorrect c.# Correct d.# They are useful in determining the active conformation of a series of related compounds. They are easier to synthesise than more flexible acyclic molecules. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 15 15) What term is used to describe the process by which drugs are fitted into their target binding sites using molecular modelling? Feedback: Docking is where a molecular ligand is fitted into its binding site by molecular modelling. incorrect a.# Energy minimisation. incorrect b.# Conformational searching. Correct c.# Docking. incorrect d.# Overlaying. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 16 16) What term is used for the design of a novel drug based on molecular modelling studies of a binding site Feedback: De novo drug design involves the computer-aided design of a drug based purely on knowledge of a binding site, and without the benefit of a lead compound. incorrect a.# Drug development. incorrect b.# Structure-based drug design. Correct c.# De novo drug design. incorrect d.# Drug optimisation. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 17 17) Which of the following statements is false in de novo drug design? Feedback: If a molecule is designed to fit snugly, it leaves no margin for error. If the molecule does not bind as predicted, it is unlikely to bind at all. If the molecule is designed such that it does not fill up the available space, an alternative binding mode might be possible. incorrect a.# The design of flexible molecules is superior to rigid ones. Correct b.# incorrect c.# incorrect d.# Molecules should be designed to fit as snugly as possible into the target binding site. Molecules that have to adopt an unstable conformation in order to bind should be rejected. Desolvation energies cannot be ignored. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 18 18) What is the software program LUDI used for? Feedback: LUDI is a software program used for de novo drug design. incorrect a.# Docking molecules into binding sites. Correct b.# Automated de novo drug design. incorrect c.# Creating 3D models of molecules. incorrect d.# Conformational analysis. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 19 19) Which of the following statements is untrue when using molecular modelling to design a combinatorial library? Feedback: It is the other way round. The aim is to synthesise the minimum number of structures likely to produce the maximum number of pharmacophores. incorrect a.# Pharmacophore triangles can be used to design a library. Correct b.# The aim is to synthesise the maximum number of structures likely to produce the minimum number of pharmacophores. incorrect c.# Rigid structures should be analysed before flexible ones. incorrect d.# Structures should only be included in the library if they represent at least 10% additional new pharmacophores compared to the total represented by structures already present in the library. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 20 20) Which of the following operations or calculations would generally be carried out using molecular mechanics? Feedback: Generating different conformations is carried out using molecular mechanics. The other three operations or calculations are carried out using quantum mechanics. incorrect a.# Heat of formation for specific conformations. Correct b.# Generating different conformations. incorrect c.# Partial atomic charges. incorrect d.# Transition-state energies. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 21 21) Which of the following operations or calculations would generally be carried out using quantum mechanics? Feedback: Transition-state energies can be calculated using quantum mechanics. The other three operations can be carried out using molecular mechanics. incorrect a.# Studying molecular motion. incorrect b.# Generating different conformations. incorrect c.# Energy minimisation. Correct d.# Transition-state energies. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 22 22) Which of the following software programmes is not used for drawing 2D chemical structures? Feedback: LUDI is a software programme used for de novo drug design. incorrect a.# ChemDraw. Correct b.# LUDI. incorrect c.# ChemWindow. incorrect d.# Isis/Draw. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 23 23) Which of the following software programmes is not dedicated to the creation of 3D chemical models? Feedback: CoMFA is a software programme used in 3D-QSAR. incorrect a.# CAChe. Correct b.# CoMFA. incorrect c.# Hyperchem. incorrect d.# Sybil. END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 24 24) Which of the following statements is false regarding Monte Carlo methods of conformational searching? Feedback: The programme can be used to find global energy conformations since a facility is present to avoid the structure being stuck in energy 'wells'. At regular intervals, the programme introduces a large change in conformation to ensure that a structure is moved out of a 'well'. incorrect a.# The Monte Carlo method introduces a bias towards stable conformations. Correct b.# The method has the drawback that the structure becomes stuck in a local energy minimum 'well' and fails to reach the global energy minimum. incorrect c.# Energies of randomly created conformations are compared, incorrect d.# then further minor modifications are carried out on the more stable conformations. Random conformations are generated by carrying out bond rotations END OF QUESTION Type: multiple choice Title: Chapter 17 - Question 25 25) Molecular dynamics can be used to search for different conformations of a molecule. Which of the following statements is false? Feedback: Each atom only moves a fraction of a bond length between each round of calculations. incorrect a.# A variety of different conformations are generated by 'heating' the molecule to 900K. incorrect b.# The position and velocity of each atom is measured after each femtosecond of movement. incorrect c.# The programme treats each atom as a moving sphere. Correct d.# END OF QUESTION Each atom is only allowed to move a bond length between each cycle of calculations.