Recent Insights into Protein Crystal Nucleation

Abstract

Homogeneous nucleation of protein crystals in solution is tackled from both thermodynamic and energetic perspectives. The entropic contribution to the destructive action of water molecules which tend to tear up the crystals and to their bond energy is considered. It is argued that, in contrast to the crystals' bond energy, the magnitude of destructive energy depends on the imposed supersaturation. The rationale behind the consideration presented is that the critical nucleus size is determined by the balance between destructive and bond energies. By summing up all intra-crystal bonds, the breaking of which is needed to disintegrate a crystal into its constituting molecules, and using a crystallographic computer program, the bond energy of the closest-packed crystals is calculated (hexagonal closest-packed crystals are given as an example). This approach is compared to the classical mean work of separation (MWS) method of Stranski and Kaischew. While the latter is applied merely for the so-called Kossel-crystal and vapor grown crystals, the approach presented can be used to establish the supersaturation dependence of the protein crystal nucleus size of arbitrary lattice structures.Keywords: protein crystal nucleation; thermodynamic and energetic approach; protein 'affinity' to water; solubility; balance between crystal bond energy and destructive surface energies; supersaturation dependence of the crystal nucleus size

Optimization of Vapor Diffusion Conditions for Anti-CD20 Crystallization and Scale-Up to Meso Batch

“…Nevertheless, vapor diffusion still remains an efficient method to screen 2 of 13 crystallization conditions using a low quantity of protein. Regardless of the method, crystallization is potentially able to reduce downstream manufacturing costs by improving the efficiency of the protein purification step with respect to conventional chromatographic methods [5][6][7][8][9][10][11]. Moreover, the active ingredient is usually more stable in crystal form than in solution, a feature that is crucial in the case of samples that easily degrade, such as protein molecules.…”

Peculiarities of Protein Crystal Nucleation and Growth

“…The intuitive suggestion of Garcia-Ruiz [48] for a balance between the sum of all intra-crystal bond energies (which maintain the integrity of a crystalline cluster) and the sum of surface destructive energies (which tend to tear up it) was our starting platform for further considerations [49], which brings us to the so-called EBDE method [50]. The thermodynamic substantiation of EBDE was presented earlier in this Journal.…”

“…This means that any supersaturation increase will lead to an increase in ψ b /ψ d ratio. A rigorous definition of protein-to-water 'affinity', which uses both nucleation process enthalpy and entropy, was provided in [50].…”

“…Instead of Kossel crystals (existing extremely rarely in nature), closest packings of equal spheres are considered: 1. Crystallography equations for hexagonal crystal structures (see [50]) are applied for EBDE calculations using pore model of a hexagonal prism (Figure 1a). By denoting the total number of molecules in the hexagonal monolayer by (z), and the number of molecules in its edge by (λ), we have:…”

Biological Crystallization

“…Nanev tackles the fundamental aspects of nucleation and growth of protein in the successive articles nº 7 and 8. In his first paper [7], he presents a study that establishes the supersaturation dependence of the protein crystal nucleus size of arbitrary lattice structures. His approach is compared to the classical one of Stranski and Kaischew, which is applied merely for the so-called Kossel-crystal and vapor grown crystals.…”