Isothermal Titration Calorimetry (ITC) is considered the ‘gold standard’ biophysical assay to determine the binding affinity/dissociation constant for any interaction involving proteins, nucleic acids, or lipids. ITC also determines the binding stoichiometry (related to the number of binding sites), and the binding thermodynamics.

MicroCal LLC, now part of Malvern Panalytical, launched the world’s first commercial ITC instrument, the OMEGA, in 1987 (there are several OMEGA ITCs still in use today!).  MicroCal then followed this success with the MCS ITC in 1992, the VP-ITC in 1998, and the iTC200 in 2007. In 2004, MicroCal developed the AutoITC, the first ITC with an autosampler for 24/7 operation, and in 2–8, we released the Automated iTC200. In 2015, Malvern Panalytical released PEAQ-ITC and the Automated PEAQ-ITC, our latest ITC systems with advanced hardware and software.

Thousands of MicroCal ITC instruments are used worldwide in life science research labs, and in pharmaceutical and biopharmaceutical companies.

On June 30, 2018, I performed Google Scholar searches for MicroCal + at least one ITC product name. The results, shown below in 5-year increments, show dramatic growth in the use of MicroCal ITC systems with an associated increase in publications:

1988-1992: 15 hits

1993-1997: 246 hits

1998-2002: 857 hits

2003-2007: 2250 hits

2008-2012: 4360 hits

2013-2018: 5800 hits

These articles detail the characterization of many types of interactions, including protein-small molecule, protein-protein, protein-DNA, antibody-antigen, and enzyme-substrate interactions. ITC is commonly used to analyze the binding of drug candidates to their target molecules, and use this information to further develop these drugs. There is also growing use of ITC to characterize interactions with nanoparticles, polymers, membranes, surfactants, and micelles.

Over 350 journals and books were included in this list of citations.

The following journals had more than 25 articles published between January 1, 2015-June 30, 2018 that cited use of a MicroCal ITC instrument (number of articles rounded to nearest 5):

Journal of Biological Chemistry (260); Scientific Reports (225); Nature Communications (135);  Biochemistry (125); PloS One (100); Biochimica et Biophysica Acta (BBA) (85); Structure (85); Nucleic Acids Research (80); Proceedings of the National Academy of Sciences (80);  International Journal of Biological Macromolecules (70); RSC Advances (70); Journal of Medicinal Chemistry (60); Journal of Molecular Biology (50); The Journal of Physical Chemistry B (50); Elife (45); Langmuir (45); Biochemical and Biophysical Research Communications (40); Nature Chemical Biology (40);  ACS Chemical Biology(35); Chemistry-A European Journal (35); Biochemical Journal (30); Biophysical Journal (30); FEBS Letters (30); Journal of the American Chemical Society (30); Molecular Cell (30); Nature (30); Nature Structural and Molecular Biology (30); Protein Science (30); The FEBS Journal (30); ChemBioChem (25); Physical Chemistry Chemical Physics (25); The Journal of Chemical Thermodynamics (25);

ITC was used in papers published in diverse journals, including:

Acta parasitological:Measurement of binding strength between prey proteins interacting with Toxoplasma gondii SAG1 and SAG2 using isothermal titration calorimetry (ITC)

AIDS: “Design of a highly potent HIV-1 fusion inhibitor targeting the gp41 pocket

Allergy:Characterization of maize chitinase‐A, a tough allergenic molecule”

Anesthesiology:Discovery of a novel general anesthetic chemotype using high-throughput screening”

Antibodies:Dimerized Domain V of Beta2-Glycoprotein I Is Sufficient to Upregulate Procoagulan Activity in PMA-Treated U937 Monocytes and Require Intact Residues in Two Phospholipid-Binding Loops”

Archives of Toxicology:Interaction of perfluoroalkyl acids with human liver fatty acid-binding protein”

Bioengineering & Translational Medicine:Targeting HPV‐infected cervical cancer cells with PEGylated liposomes encapsulating siRNA and the role of siRNA complexation with polyethylenimine”

Biomedicine & Pharmacotherapy:Nanobodies targeting cortactin proline rich, helical and actin binding regions downregulate invadopodium formation and matrix degradation in SCC-61 cancer cells”

Blood:Structural basis for quinine-dependent antibody binding to platelet integrin αIIbβ3”

Breast Cancer Research:Gossypol has anti-cancer effects by dual-targeting MDM2 and VEGF in human breast cancer”

Cell Host & Microbe:Structural conservation despite huge sequence diversity allows EPCR binding by the PfEMP1 family implicated in severe childhood malaria”

Cerebral Cortex:Cortical layer inversion and deregulation of reelin signaling in the absence of SOCS6 and SOCS7”

Chemical Research in Toxicology:Identification and Molecular Interaction Studies of Thyroid Hormone Receptor Disruptors among Household Dust Contaminants”

Chemistry Select:An ITC Study on the Interaction Energy Between Galactomannan Biopolymers and Selected MO2 Nanoparticles in Hydrogels”

ChemNanoMat:The Effect of PEGylation on Multivalent Binding: A Surface Plasmon Resonance and Isothermal Titration Calorimetry Study with Structurally Diverse PEG‐Dendritic GATG Copolymers”

Chirality:Isothermal Titration Calorimetry of Chiral Polymeric Nanoparticles”

Clinical and Translational Oncology:Selection of DNA aptamers for extra cellular domain of human epidermal growth factor receptor 2 to detect HER2 positive carcinomas”

Cogent Biology:Isolation and purification of phytocystatin from almond: Biochemical, biophysical, and immunological characterization”

Colloid and Polymer Science:Adsorption of lysozyme on pH-responsive PnBA-b-PAA polymeric nanoparticles: studies by stopped-flow SAXS and ITC”

Extremophiles:High-affinity RNA binding by a hyperthermophilic single-stranded DNA-binding protein”

Flavour and Fragrance Journal:Facile separation of cinnamyl acetate and cinnamaldehyde based on host–guest complexation with β‐cyclodextrin”

Food Chemistry:Effect of the addition of mannoproteins on the interaction between wine flavonols and salivary proteins”

Food Research International:Evaluation of butyrylcholinesterase inhibitory activity by chlorogenic acids and coffee extracts assessed in ITC and docking simulation models”

Journal of Agricultural and Food Chemistry:Ethanol Concentration Influences the Mechanisms of Wine Tannin Interactions with Poly(l-proline) in Model Wine”

Tuberculosis:Investigating the inhibitory potential of 2-Aminopurine metal complexes against serine/threonine protein kinases from Mycobacterium tuberculosis”

Water, Air, & Soil Pollution:Exploring the Effect of Cu2+ on Sludge Hydrolysis and Interaction Mechanism between Cu2+ and Xylanase by Multispectral and Thermodynamic Methods”

The following books, published since 2015, include chapters with protocols using MicroCal ITC:

AMPK (Methods in Molecular Biology, volume 1732):Applications of NMR and ITC for the Study of the Kinetics of Carbohydrate Binding by AMPK β-Subunit Carbohydrate-Binding Modules”

Antimicrobial Peptides (Methods in Molecular Biology, volume 1548):Calorimetry Methods to Study Membrane Interactions and Perturbations Induced by Antimicrobial Host Defense Peptides”

Applied Biophysics for Drug Discovery:Thermodynamics in Drug Discovery”

Biocalorimetry (Methods, volume 76):

Biocalorimetry: Foundations and Contemporary Approaches

Biochemical Roles of Eukaryotic Cell Surface Macromolecules (Advances in Experimental Medicine and Biology, volume 842):Biophysical Characterization of the Interaction of O-acylcholines with the Major Bovine Seminal Plasma Protein, PDC-109”

c-Di-GMP Signaling (Methods in Molecular Biology, volume 1657):Isothermal Titration Calorimetry to Determine Apparent Dissociation Constants (Kd) and Stoichiometry of Interaction (n) of C-di-GMP Binding Proteins”

Calorimetry (Methods in Enzymology, volume 567)

Current Protocols in Nucleic Acid Chemistry:Calorimetry of Nucleic Acids”

Excipient Applications in Formulation Design and Drug Delivery:Drug Excipient interactions”

Galectins:Probing lectin–mucin interactions by isothermal titration microcalorimetry” https://link.springer.com/protocol/10.1007/978-1-4939-1396-1_5

Glycosaminoglycans:Using Isothermal Titration Calorimetry to Determine Thermodynamic Parameters of Protein–Glycosaminoglycan Interaction”

In Vitro Mutagenesis (Methods in Molecular Biology, volume 1498):Biochemical and Biophysical Methods to Examine the Effects of Site-Directed Mutagenesis on Enzymatic Activities and Interprotein Interactions”

Molecular Physiology and Ecophysiology of Sulfur:Investigation of Protein-Protein Interactions of Ferredoxin and Sulfite Reductase Under Different Sodium Chloride Concentrations by NMR Spectroscopy and Isothermal Titration Calorimetry”

Nucleic Acid Aptamers  (Methods in Molecular Biology, volume 1380):Label-free determination of the dissociation constant of small molecule-aptamer interaction by isothermal titration calorimetry”

Nucleic Acid Crystallography (Methods in Molecular Biology, volume 1320):Isothermal Titration Calorimetry: Assisted Crystallization of RNA–Ligand Complexes”

Polymer Micelles:Micellization Thermodynamics of Pluronic P123 (EO20PO70EO20) Amphiphilic Block Copolymer in Aqueous Ethylammonium Nitrate (EAN) Solutions”

Potassium Channels (Methods in Molecular Biology, volume 1684):Ion Binding to Transport Proteins using Isothermal Titration Calorimetry”

Semaphorin Signaling Methods (Methods in Molecular Biology, volume 1493): “Characterizing Plexin GTPase Interactions Using Gel Filtration, Surface Plasmon Resonance Spectrometry, and Isothermal Titration Calorimetry”

SH2 Domains (Methods in Molecular Biology, volume 1555):Calorimetric measurement of SH2 domain ligand affinities”

Thermodynamics and Kinetics of Drug Binding: “Thermodynamic Profiling of Carbonic Anhydrase Inhibitors”

Vitamin C:Encapsulation of Vitamin C into β‐Cyclodextrin for Advanced and Regulatory Release”

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