Microcalorimetry for the Life Sciences

Transcription

1 Microcalorimetry for the Life Sciences

2 Why Microcalorimetry? Microcalorimetry is universal detector Heat is generated or absorbed in every chemical process In-solution No molecular weight limitations Label-free Non-optical

3 Calorimetry in the Life Sciences Binding Studies Quick and accurate affinities Mechanism of action (MOA) screening and conformational changes Structure-function relationships Specific vs. non-specific binding Kinetics K M, V max, k cat Enzyme Inhibition Stability Studies Intramolecular e.g. protein unfolding Intermolecular e.g. solution optimization, CMCs

4 Isothermal Titration Calorimetry VP-ITC µcal/sec Time (min) AutoITC

5 Differential Scanning Calorimetry VP-DSC VP-Capillary DSC Platform

6 How Do They Work? Measuring Temperature Changes in Calorimetry

7 Isothermal Titration Calorimetry: A Method for Characterizing Binding Interactions Mixture of two components at a set temperature Heat of interaction is measured Parameters measured from a single ITC experiment Affinities Binding mechanism Number of binding sites Kinetics

8 Isothermal Titration Calorimetry Typical ITC Data µcal/sec 10 8 kcal/mole of injectant ΔH Mechanism Affinity Time (min) Stoichiometry Molar Ratio

9 ITC Protein-Small Molecule Interaction 4-carboxybenzenesulfonomide titrated into carbonic anhydrase II N = 0.97 K D = 730 nm ΔH = kcal/mol Day, et al, Protein Sci. 11, (2002)

10 ITC Protein-Protein Interaction A: Wild-type cytochrome c titrated into wild-type cytochrome c peroxidase B: Mutant cytochrome c titrated into mutant cytochrome c peroxidase Pielak and Wang, Biochemistry 40, (2001)

11 Multiple Binding Sites ITC shows differential binding of Mn(II) ions to WT T5 5 nuclease µcal/sec Time (min) kcal/mole -2 0 n = 0.85 K a = 3.0 x 10 5 M -1 ΔH = kcal mol -1 n = 1.3 K a = 1.0 x 10 4 M -1 ΔH = +1.6 kcal mol Feng, et al, Nat. Struct. Mol. Biol. 11, (2004) Molar Ratio

12 Binding Energetics Mechanism of Action (MoA) Conformational changes H-bonding Hydrophobic interactions Charge-charge interactions Multiprobe structure-activity relationship (SAR) Validate in-silico modelling Selectivity and adaptability of drugs

13 Binding Mechanism Same affinity but different binding mechanisms and specificity kcal/mole of injectant

14 Enthalpic and Entropic Contributions to Binding Affinity Enthalpy and Entropy make up the affinity (ΔG=-RTlnK) ΔG=ΔH-TΔS ΔH kcal mol TΔS -4 ΔG -6-8

15 Enthalpy and Entropy Entropy Hydrophobic interactions Water release Ion release Conformational changes Enthalpy Hydrogen bonding Protonation events More specific

16 Energetic Signatures A is enthalpy driven. Good H-bonding coupled to a conformational change B is entropically driven. Hydrophobic Interactions and possibly rigid body kj mol A B C -TΔS ΔH ΔG C is mildly enthalpic and entropic

17 Drug Discovery Binding of Inhibitors 5 to HIV-1 Protease 0 kcal/mole ΔG ΔH TΔS Indinavir Nelfinavir Saquinavir Ritonavir Amprenavir Lopinavir KNI-272 KNI-764 Ohtaka, et al. Protein Sci. 11, (2002)

18 Enzyme and ITC ITC measures thermal power (dq/dt)

19 Enzyme Rate = V o dq/dt

20 ITC and Binding - Summary Quick and Easy Affinities Mechanism of Action SAR-Structure Activity Relationships Drug design Multi-probe technique detects contributions that affinity only methods may miss Enzyme

21 Differential Scanning Calorimetry Typical Data

22 Minimum Protein for DSC - Lysozyme 25 μg/ml Kholodenko and Freire, Anal. Biochem. 270, (1999)

23 Data Interpretation Oligomers T M Shelf-Life/ Stability 10 Binding Cp (kcal/mole/ o C) } ΔC p ΔH Stabilizing Forces/ Energetics Temperature ( o C)

24 Data Interpretation Oligomers T M Shelf-Life/ Stability 10 Binding Cp (kcal/mole/ o C) } ΔC p ΔH Stabilizing Forces/ Energetics Temperature ( o C)

25 Stability Intrinsic molecular Thermodynamic characterization of macromolecular unfolding- proteins, nucleic acids, lipids, Domain structure identification Assessment of viability and/or crystallization potential of protein constructs and mutants Extrinsic molecular Formulation studies effect of different excipients, preservatives Binding Membrane and lipid studies

26 DSC Protein Stability and Mutant Characterization Sot, et al, J. Biol. Chem. 278, (2003)

27 Domain Identification Structural organization of biomolecules Protein has a least two structural domains O Brien, et al, Biophys J. 70, (1996)

28 Formulations/Protein Storage CD40 ligand has a longer shelf-life at ph 6-7. DSC experiment could be completed in 1 day as opposed to 8 days by size exclusion chromatography Remmele and Gombotz, BioPharm 13, (2000)

29 Binding HTS validation OR Ligand Identification FBS at 60 μm Plus VAF955 and 1827 (at 1:1 and 1:20 [Ratios]) VAF955 (1:20) Cp(cal/ o C) No ligand 1827(1:1) VAF (1:1) 1827 (1:20) Temperature ( o C)

30 Antibody Stability Effects of Glycosylation Native Partially Deglycosylated Deglycosylated Mimura, et al, J. Biol. Chem. 276, ( 2001)

31 Lipid/Membrane systems Uptake of proteins into lipid membrane causes peak broadening Narrow Broad Lipid phase transitions

32 Microcalorimetry Summary Affinities and Binding Energetics Mechanisms of Binding Stoichiometry Determination of Active Concentration Enzyme Kinetics Thermodynamic Stability Formulations and Drug delivery

33 Conclusion Microcalorimetry is one of the most versatile technologies available for characterization and analysis of biological molecules