1. ABOUT THE DATASET --- Title: Dataset for "Phage Display Identifies Affimer Proteins that Direct Calcium Carbonate Polymorph Formation" Creator(s): Ilaria Sandei[1], Thembaninkosi Gaule [1,2], Matthew Batchelor[2], Emanuele Paci[2], Yi-Yeoun Kim[1], Alexander N. Kulak[1], Darren Tomlinson[2] and Fiona C. Meldrum[1] Organisation(s): [1] School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK [2] School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK. Rights-holder(s): Copyright 2025 University of Leeds Publication Year: 2025 Description: Dataset supporting a study in which a phage display approach is used to identify proteins – rather than the short peptides typically identified using this method – that can direct calcium carbonate formation. A 1.3 X 1010 library of Affimer proteins was displayed on modified M13 phage, where Affimer is a 3 kDa protein scaffold that displays two variable regions of 9–13 residues. The phage displaying the Affimer library were then screened in binding assays against calcite and aragonite at pH 7.4, and four different strongly-binding proteins were identified. The two aragonite-binding proteins generated aragonite when calcium and magnesium ions were present at a 1:1 ratio, while the calcite-binding proteins produce magnesium-calcite under the same conditions. Calcite alone formed in the presence of all four proteins in the absence of magnesium ions. In combination with molecular dynamics simulations to evaluate the conformations of the proteins in solution, this work demonstrates the importance of conformation in polymorph control, and highlights the importance of magnesium ions, which are abundant in seawater, to reduce the energetic barriers associated with aragonite formation. Cite as: Sandei I., Gaule T., Batchelor M., Paci E., Kim YY, Kulak AN, Tomlinson D, Meldrum FC Dataset for “Phage Display Identifies Affimer Proteins that Direct Calcium Carbonate Polymorph Formation” [Dataset] https://doi.org/10.5518/1374 Related publication: Sandei I., Gaule T., Batchelor M., Paci E., Kim YY, Kulak AN, Tomlinson D, Meldrum FC “Phage Display Identifies Affimer Proteins that Direct Calcium Carbonate Polymorph Formation” Biomater. Sci. (2024), 12, 5215-5224. 2. TERMS OF USE --- Copyright [2025] [University of Leeds]. This dataset is licensed under a Creative Commons Attribution 4.0 International Licence: https://creativecommons.org/licenses/by/4.0/ 3. PROJECT AND FUNDING INFORMATION --- Title: DYNAMIN Dates: Sept 2018 to Aug 2025 Funding organisation: ERC Grant no.: Grant Agreement No. 788968 Title: Flow-Xl: A New UK Facility for Analysis of Crystallisation in Flow Systems Dates: Mar 2020 - Mar 2023 Funding organisation: EPSRC Grant no.: EP/T006331/1 4. CONTENTS --- Folder: IR: Raw IR data of calcite and aragonite crystals Folder: MD Simulations Data supporting simulations described in the main article Folder: Phage Display Sequences of Affimer proteins raised against calcite and aragonite Folder: Raman Raman data of crystals produced in the absence of additives, with proteins and with magnesium Folder: SEM Affimer + Mg SEM images of crystals produced in the presence of the different affimer proteins and Mg Folder: SEM Affimer no Mg SEM images of crystals produced in the presence of the different affimer proteins Folder: Subcloning Subcloning data of Affimer proteins binding to calcite (CBA proteins) and aragonite (ABA proteins) Folder: XRD Raw XRD data of calcite and aragonite crystals File: Supplementary Information pdf file of SI published to accompany article 5. METHODS --- A full description of the methods and how data were recorded is provided in the associated full publication.