Trinity College Dublin require the supply of Isothermal Titration Calorimeter (ITC) for protein complexes for the deliverables of a Research Ireland grant. The calorimeter is required for measuring micro-calories of heat evolved or absorbed from protein-protein and protein-small molecule interactions in aqueous solution. The measurement involves multiple injections of ligand (protein, other macromolecules, small molecules) into a cell containing another protein, small molecule, or other macromolecules. The titration is performed under isothermal conditions using a reference cell containing water or related aqueous solution that is similar to the experimental cell. Changes in temperature between the two cells during injections are rapidly equilibrated using active power compensation that is calibrated for calories of heat. The properties of the isothermal titration calorimeter should include the following: (1) The tenderer SHOULD provide a new or recent state-of the-art (ex-demo) model ITC calorimeter, and if ex-demo, it should be minimally used. Volume of experimental and reference cells should be approximately 200 mico-Liters. (2) Typical concentration ranges for analyses should ideally be in the range from 1 micro-Molar to 100 micro-Molar for macromolecules (typically proteins) in the cell, and 10 micro-Molar to 1M concentrations in the injections syringe for the ligand. (3) Preferred temperature range for isothermal titrations from 4 deg Celsius to 60 deg Celsius. (4) software that can analyse data and determine the Kd (dissociation constant), enthalpy, and entropy from analyses of the titrations. (5) Software should handle simple 1:1 binding models, with the possibility to analyse more complex interactions, such as multiple binding sites, sequential interactions. The capability to analyse complex binding with rigor would be a major advantage, as many interactions are not simple 1:1. (6) minimal generation of bubbles or artefactual heat, which may arise from high concentrations of viscous protein in cell (7) Ideally - prefer system/software compatibility with .opj files generated by Origin 7 (or later) software, since we have nearly 20 years of previous data collections. This could be transferred to new control computer for continuity. (8) New computer, drivers, and accessories required to run the calorimeter software.