Amphiphiles modify the properties of detergent solutions used in crystallization of membrane proteins

CNSL, a Promising Building Blocks for Sustainable Molecular Design of Surfactants: A Critical Review

Surfactants are crystallizing a certain focus for consumer interest, and their market is still expected to grow by 4 to 5% each year. Most of the time these surfactants are of petroleum origin and are not often biodegradable. Cashew Nut Shell Liquid (CNSL) is a promising non-edible renewable resource, directly extracted from the shell of the cashew nut. The interesting structure of CNSL and its components (cardanol, anacardic acid and cardol) lead to the synthesis of biobased surfactants. Indeed, non-ionic, anionic, cationic and zwitterionic surfactants based on CNSL have been reported in the literature. Even now, CNSL is absent or barely mentioned in specialized review or chapters talking about synthetic biobased surfactants. Thus, this review focuses on CNSL as a building block for the synthesis of surfactants. In the first part, it describes and criticizes the synthesis of molecules and in the second part, it compares the efficiency and the properties (CMC, surface tension, kraft temperature, biodegradability) of the obtained products with each other and with commercial ones.

Three-dimensional crystallization of membrane proteins

Although the examination of the protein data bank reveals an important backlog in the number of three-dimensional structures of membrane proteins, several recent successes are serving as preludes to what will become a very prosperous decade in this field. Systematic investigations of various factors affecting the stability of membrane proteins, as well as their potential to crystallize three dimensionally, have paved the way for such achievements. The importance of the role of detergents both at the level of purification and crystallization is now well established. In addition, the recognition of the protein-detergent complex as the entity to crystallize, as well as the understanding of its physical-chemical properties and discovery of factors affecting these, have permitted the design of better crystallization strategies. As a consequence of the various efforts in the field, new crystallization methods for membrane proteins are being implemented. These have already been successful and are expected to contribute significantly to the future successes. This chapter will review some basic principles in membrane protein crystallization and give an overview of the current state of the art in the field. Some practical guidelines to help the novice approach the problem of membrane protein crystallization from the initial step of protein purification to crystallogenesis will also be given.

The monotopic membrane protein human oxidosqualene cyclase is active as monomer

The monotopic integral membrane protein 2,3-oxidosqualene cyclase (OSC) catalyzes the formation of lanosterol the first sterol precursor of cholesterol in mammals. Therefore, it is an important target for the development of new hypocholesterolemic drugs. Here, we report the overexpression and purification of functional human OSC (hOSC) in Pichia pastoris. The obtained IC(50) for the reference inhibitor Ro 48-8071 is nearly identical for the recombinant hOSC compared to OSC from human liver microsomes. The correlation of analytical ultracentrifugation data and activity measurements showed the highest enzymatic activity for the monomeric hOSC indicating that this would be the natural form. Furthermore, these data helped us to identify the detergent for a successful crystallization of the protein. The availability of this active recombinant human membrane protein is a very important step on the way to a more detailed functional and structural characterization of OSCs.

Rationalization of membrane protein crystallization with polyethylene glycol using a simple depletion model

Based on the importance of crystallizing membrane proteins in a rational way, cytochrome bc(1) complex (BC1) was crystallized using polyethylene glycol (PEG) as a sole crystallization agent. Interaction between protein-detergent complexes of BC1 was estimated by dynamic light scattering, and was compared with the numerical calculation using the Derjaguin-Landau-Verwey-Overbeek potential plus a depletion potential, without considering specific surface properties of the protein-detergent complexes. The experiments and calculation were found to be consistent and we obtained a relation between PEG molecular weight M and the range of depletion zone delta as delta approximately M(0.48+/-0.02). The stability of liquid phase of BC1 solutions was controlled by a ratio of (the range of depletion zone)/(the radius of a BC1 particle), which was consistent with recent theoretical predictions. The crystallization was most successful under a condition where the stability of the liquid phase changed from stable to unstable. The PEG molecular weight that fulfilled this condition coincided with the one used empirically to crystallize BC1 in the past by a number of groups. These results are compared to the fact that membrane proteins were often successfully crystallized close to the detergent cloud point.