Biophysical Approaches to Drug Design

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Biophysical Approaches to Drug Design
Overall Organization of the Topic

• Approaches Useful in Drug Design
• Fluorescence Spectroscopy
• - Principle of Fluorescence
• - Factors governing fluorescence intensity
• - Fluorescent groups
• - Sensitivity of Fluorescence to Environment
• - Fluorescence Resonance Energy Transfer

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Biophysical Approaches Useful in Drug Design

• Absorption Spectroscopy
• Fluorescence Spectroscopy
• Infrared Spectroscopy
• Raman Spectroscopy
• Nuclear Magnetic Resonance Spectroscopy
• Electron Spin Resonance Spectroscopy
• Circular Dichroism
• Centrifugation Techniques
• X-ray Crystallography

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Fluorescence Spectroscopy
Principle
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Electronic States of Molecules
Example of Ethylene
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Obtaining Fluorescence Spectrum
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Factors Governing Fluorescence Intensity

• Internal Conversion (kIC)
• Collisional De-excitation (kQ)
• Intersystem Crossing (kIS)

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Fluorescent Groups

• Intrinsic Groups in Proteins and Nucleic Acids
• - Trp, Tyr, Phe, Cys, Adenine, Guanine,

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Fluorescent Groups

• External Probes

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Sensitivity of Fluorescence to Environment

• Determination of Equilibrium Dissociation
  Constants

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Binding Affinities as a Function of Structure

• Varying the Receptor

• Varying the Ligand

Ligand KD DGO
(nM)
(kcal/mol) DEFGH 110-5
-19 DEFGH 110-3
-16 DEFG 34 -10.2
DEF 2,000
-7.8 EFGH 6,900 -7.0
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Fluorescence Resonance Energy Transfer
Principle
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Fluorescence Resonance Energy Transfer
Determining Substrate Specificities