MSOP1016 QSAR Lecture 8&9 Summary
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Questions and Answers

What type of parameters are used to build a QSAR model?

  • Biological parameters
  • Hydrophobic parameters (correct)
  • Chemical parameters
  • Physical parameters

    • In a QSAR study, what type of analysis is commonly used to develop models?

  • Multiple regression analysis (correct)
  • Discriminant analysis
  • Cluster analysis
  • Factor analysis

    • What technique is used for screening molecules in virtual screening?

  • Enzyme kinetics
  • Immunofluorescence
  • Drug-receptor docking (correct)
  • Mass spectrometry

    • When is QSAR typically used in drug discovery?

    <p>When the molecular structure and properties of ligands are known</p> Signup and view all the answers

    Which parameter is NOT considered in building QSAR models?

    <p>Biological parameters</p> Signup and view all the answers

    What is one of the primary purposes of virtual combinatorial chemistry methods?

    <p>Screening diverse set of molecules</p> Signup and view all the answers

    What relationship exists between hydrophobicity constant (π) and the hydrophobicity of a substituent?

    <p>A positive π value indicates the substituent is more hydrophobic than H</p> Signup and view all the answers

    How can hydrophobic parameters be used to predict drug activity?

    <p>Most drugs need to be hydrophobic to be absorbed, so hydrophobic parameters are crucial</p> Signup and view all the answers

    What type of relationship do linear QSAR logP examples demonstrate?

    <p>As logP increases, binding to proteins increases</p> Signup and view all the answers

    How do electron parameters contribute to drug-receptor interactions?

    <p>They measure electrostatic interaction forces between molecules in drug-receptor interactions</p> Signup and view all the answers

    What effect does increasing logP have on the hypnosis effect of barbiturates according to parabolic relationships?

    <p>Hypnosis effect reaches a maximum at an optimum logP value, then decreases</p> Signup and view all the answers

    What is the significance of the hydrophobicity constant (π) in calculating octanol/water partition coefficients?

    <p>π values are used to adjust log P values in different solvent systems</p> Signup and view all the answers

    What is the main aim of using QSAR in predicting biological activity?

    <p>To express the relationship between chemical structure and biological activity mathematically</p> Signup and view all the answers

    What is one main requirement for building a QSAR model?

    <p>Having a diverse set of drug molecules</p> Signup and view all the answers

    What does QSAR stand for?

    <p>Quantitative Structure-Activity Relationship</p> Signup and view all the answers

    In QSAR, what is used to represent the 2D structure of a compound for computer calculations?

    <p>SMILES codes</p> Signup and view all the answers

    Which term is used to refer to the statistical relationships between molecular structure and biological activity?

    <p>Quantitative Structure-Activity Relationship (QSAR)</p> Signup and view all the answers

    What is the purpose of determining properties like molecular weight and polarity in QSAR?

    <p>To quantify the molecular structure for correlation analysis</p> Signup and view all the answers

    How is the relationship between chemical structure and biological activity expressed in QSAR?

    <p>$y = c + mx$</p> Signup and view all the answers

    Why might there be errors in predicting biological activity using QSAR models?

    <p>Because the line of best fit may not perfectly represent all data points</p> Signup and view all the answers

    What does Log P represent in QSAR calculations?

    <p>A molecular property used to calculate relationships in QSAR</p> Signup and view all the answers

    Which scientist is primarily credited with developing the methodology known as QSAR?

    <p>Corwin Hansch</p> Signup and view all the answers

    What role do shape and size play in biological activity?

    <p>Impact the absorption of large compounds</p> Signup and view all the answers

    In a drug-receptor interaction, what effect does steric hindrance from a substituent have?

    <p>Decreases affinity</p> Signup and view all the answers

    What is the simplest molecular parameter related to size?

    <p>Molecular volume</p> Signup and view all the answers

    Which parameter describes the volume occupied by one mole of a compound?

    <p>Molecular volume</p> Signup and view all the answers

    What does a high correlation coefficient (r) indicate in QSAR models?

    <p>Goodness of fit</p> Signup and view all the answers

    What information is provided by the standard error of the estimate (s) in a QSAR model?

    <p>Error value</p> Signup and view all the answers

    What does an r2 value of 0.96 represent in QSAR models?

    <p>&quot;Percent of variation explained by X&quot;</p> Signup and view all the answers

    In a QSAR study, what does log(1/EC50) = 0.817π - 0.764 represent?

    <p>&quot;Regression equation&quot;</p> Signup and view all the answers

    "Log Biologic activity = Log P" suggests a correlation between what two parameters?

    <p>&quot;Biologic activity and hydrophobicity&quot;</p> Signup and view all the answers

    "Log 1/C = 0.75 Log P + 2.30" provides information on what aspect in a QSAR model?

    <p>&quot;Regression equation&quot;</p> Signup and view all the answers

    According to the provided equation, which substituents should be chosen to increase activity based on their effect on pi and sigma values?

    <p>Substituents with positive pi and negative sigma values</p> Signup and view all the answers

    In a QSAR study, which molecular descriptor would be associated with hydrophobicity according to the text?

    <p>Log P</p> Signup and view all the answers

    Which parameter is crucial for determining the goodness of fit for a QSAR equation in regression analysis?

    <p>Correlation coefficient, r/r2</p> Signup and view all the answers

    When interpreting a QSAR equation, what type of substituents would be selected to increase activity based on their pi and sigma values?

    <p>Positive pi and negative sigma values</p> Signup and view all the answers

    What is the significance of SMILES encoding in the context of QSAR studies?

    <p>Encoding 2D chemical structures for molecular descriptor calculation</p> Signup and view all the answers

    In Craig plots, which areas correspond to hydrophobic/lipophilic and electron-donating substituents respectively?

    <p>Areas 2 and 4; Areas 3 and 4</p> Signup and view all the answers

    What is the primary function of electron-deficient groups in morphine analogues?

    <p>Interact with a negatively charged area in the receptor site</p> Signup and view all the answers

    Which type of groups will reduce the electron density on the amine, leading to a stronger interaction with the receptor?

    <p>Electron-withdrawing groups</p> Signup and view all the answers

    What effect do electron-donating groups like methyl (-CH3) have on the affinity of morphine analogues?

    <p>Reduce the analgesic effect</p> Signup and view all the answers

    What is the purpose of the Hammett constant sigma (σ) introduced by Hammett?

    <p>Predict rate constants of chemical reactions</p> Signup and view all the answers

    In the context of Hammett constant sigma (σ), what do positive values indicate for substituents?

    <p>Strong electron-withdrawing ability</p> Signup and view all the answers

    How does an electron-donating group like -CH3 affect the pKa value of a compound compared to the parent compound?

    <p>Decrease the pKa value</p> Signup and view all the answers

    What is a key characteristic of Hammett constant sigma (σ) regarding its application in QSAR?

    <p>Always includes a hydrophobicity parameter</p> Signup and view all the answers

    What is the relationship between electron-withdrawing groups and biological activity according to Hammett constant sigma (σ) applications?

    <ul> <li>positive σ leads to increased activity</li> </ul> Signup and view all the answers

    How does Hammett constant sigma (σ) define the order of activity in methadone analogues?

    <p>-NO2 &gt; Cl &gt; H &gt; CH3</p> Signup and view all the answers

    What is one of the key roles of hydrogen bonding in molecular interactions?

    <p>Affects receptor binding</p> Signup and view all the answers

    What is the equation for multiple linear regression used in QSAR?

    <p>Log 1/EC50 = 0.398+1.089 +1.03MW +4.541</p> Signup and view all the answers

    How many descriptors are needed in a QSAR model according to the content provided?

    <p>At least 2 descriptors</p> Signup and view all the answers

    What does a positive coefficient for parameter 𝜋 signify in a QSAR equation?

    <p>Increases biological activity</p> Signup and view all the answers

    Why is it important to split chemicals into training and test sets in QSAR modeling?

    <p>To validate the predictive power of the model</p> Signup and view all the answers

    What does the statement 'Rubbish in, Rubbish out' imply in the context of QSAR modeling?

    <p>Quality of input data impacts model outcomes</p> Signup and view all the answers

    Which term refers to Taft's steric parameter in QSAR modeling?

    <p>Es</p> Signup and view all the answers

    In a QSAR equation, what does a negative coefficient for parameter 𝜎 suggest?

    <p>Decreases biological activity</p> Signup and view all the answers

    How is the success of a QSAR model influenced by the number of compounds used?

    <p>More compounds lead to more accurate predictions</p> Signup and view all the answers

    'Craig Plots' are primarily used for what purpose in QSAR modeling?

    <p>'Quickly deciding which analogs to synthesize'</p> Signup and view all the answers

    'MLR analysis' in QSAR stands for what term?

    <p>'Multiple Linear Regression'</p> Signup and view all the answers

    What does logP represent as a molecular descriptor in QSAR studies?

    <p>Hydrophobicity of the molecule</p> Signup and view all the answers

    Which descriptor is significant for drug-receptor binding according to the text?

    <p>Polarizability</p> Signup and view all the answers

    What can be deduced from a small range of logP values for a molecule according to the text?

    <p>A linear relationship between log 1/C and log P</p> Signup and view all the answers

    What is the significance of logP for passing through membranes?

    <p>It represents hydrophobicity for passing through membranes</p> Signup and view all the answers

    Which parameter dominates when logP values are small in QSAR studies?

    <p>Log P term</p> Signup and view all the answers

    In QSAR studies, what happens to activity as logP increases beyond a certain point?

    <p>Activity first increases then decreases</p> Signup and view all the answers

    Why might a molecule with high logP values be more susceptible to metabolism?

    <p>Due to decreased solubility in aqueous phase</p> Signup and view all the answers

    What is the relationship between log 1/C and log P when graphed at very high logP values?

    <p>'A parabolic curve'</p> Signup and view all the answers

    'Over a small range of log P, e.g. logP 1-4, a straight line is obtained' - this statement indicates a linear relationship between what variables?

    <p>'Log 1/C and log P'</p> Signup and view all the answers

    'When log P large, log P squared dominates & so activity decreases' - this statement explains the influence of what on biological activity?

    <p>Increased log P</p> Signup and view all the answers

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