Dendritic Oligoglycerol Regioisomer Mixtures and Their Utility for Membrane Protein Research

Diffusion Coefficient Analysis by Dynamic Light Scattering Enables Determination of Critical Micelle Concentration

The critical micelle concentration is an important property of supramolecular detergents. Two dynamic light scattering approaches have been developed for critical micelle concentration analysis, i. e., concentration-dependent light scattering intensity analysis and diffusion coefficient analysis. Their utility as complementary tools for a reproducible determination of critical micelle concentration remains to be clarified. Herein, we address the question which of the two approaches is more suitable for obtaining reproducible critical micelle concentration values. We systematically compare both approaches in context with common detergent classes and benchmark utility by means of literature values. Our results show that the diffusion coefficient analysis delivers reproducible critical micelle concentration values in aqueous solutions. Our findings outline a roadmap to guide the critical micelle concentration analysis of detergents by dynamic light scattering in the future.

Synthesis of Asymmetric Ionic Hybrid Detergents enables Micelles with Scalable Properties including Cell Compatibility

Ionic detergents enable applications and cause harm in biospheres due to cell toxicity. The utility of covalent combinations between ionic and non-ionic detergent headgroups in modulating cell toxicity remains speculative due to the yet rarely explored synthesis. We close this gap and establish the modular synthesis of ionic/non-ionic hybrid detergents. We restructure a combinatorial methallyl dichloride one-pot coupling into a two-step coupling, which reduces by-products, improves product yields, and enables the gram-scale preparation of asymmetric, cationic/non-ionic and anionic/non-ionic hybrid detergents. Our modular synthesis delivers new modalities for the design of ionic detergents, including an unprecedented scaling of properties that determine applications, such as charge, critical micelle concentration, solubilizing properties, hard water tolerance, and cell compatibility. We uncover that shielding the charge in ionic headgroups can switch the detergent species that is toxic to cells from monomers to mixtures of monomers and micellar assemblies. Establishing the chemistry of ionic/non-ionic hybrid detergents provides a missing evolutionary link in the structural comparison of ionic and non-ionic detergents, enables an easy synthesis access to yet unexplored chemical spaces of asymmetric hybrid materials, and delivers new modalities for designing the toxicity of supramolecular nanomaterials.

Trends in the Diversification of the Detergentome

Detergents are amphiphilic molecules that serve as enabling steps for today's world applications. The increasing diversity of the detergentome is key to applications enabled by detergent science. Regardless of the application, the optimal design of detergents is determined empirically, which leads to failed preparations, and raising costs. To facilitate project planning, here we review synthesis strategies that drive the diversification of the detergentome. Synthesis strategies relevant for industrial and academic applications include linear, modular, combinatorial, bio-based, and metric-assisted detergent synthesis. Scopes and limitations of individual synthesis strategies in context with industrial product development and academic research are discussed. Furthermore, when designing detergents, the selection of molecular building blocks, i. e., head, linker, tail, is as important as the employed synthesis strategy. To facilitate the design of safe-to-use and tailor-made detergents, we provide an overview of established head, linker, and tail groups and highlight selected scopes and limitations for applications. It becomes apparent that most recent contributions to the increasing chemical diversity of detergent building blocks originate from the development of detergents for membrane protein studies. The overview of synthesis strategies and molecular blocks will bring us closer to the ability to predictably design and synthesize optimal detergents for challenging future applications.

Protocol to test the utility of detergents for E. coli membrane protein extraction and delipidation

We present a protocol to evaluate the utility of detergents for purification and delipidation of E. coli membrane proteins. We determine the critical aggregation concentration of detergents. Furthermore, we compare the ability of detergents to extract membrane proteins and to maintain protein-lipid interactions during purification. The protocol describes steps for isolating and delipidating membrane proteins from E. coli membranes by extraction and affinity purification using detergents. The protocol does not enable an absolute quantification of purification outcomes. For complete details on the use and execution of this protocol, please refer to Urner et al.1.

Emergence of mass spectrometry detergents for membrane proteomics

Detergents enable the investigation of membrane proteins by mass spectrometry. Detergent designers aim to improve underlying methodologies and are confronted with the challenge to design detergents with optimal solution and gas-phase properties. Herein, we review literature related to the optimization of detergent chemistry and handling and identify an emerging research direction: the optimization of mass spectrometry detergents for individual applications in mass spectrometry-based membrane proteomics. We provide an overview about qualitative design aspects including their relevance for the optimization of detergents in bottom-up proteomics, top-down proteomics, native mass spectrometry, and Nativeomics. In addition to established design aspects, such as charge, concentration, degradability, detergent removal, and detergent exchange, it becomes apparent that detergent heterogeneity is a promising key driver for innovation. We anticipate that rationalizing the role of detergent structures in membrane proteomics will serve as an enabling step for the analysis of challenging biological systems.

Combinatorial synthesis enables scalable designer detergents for membrane protein studies

Non-ionic detergents with tailor-made properties are indispensable tools for today's world applications, such as cleaning, disinfection, and drug discovery. To facilitate their challenging production, herein we introduce a new detergent class, namely scalable hybrid detergents. We report a combinatorial synthesis strategy that allows us to fuse head groups of different detergents into hybrid detergents with unbeatable ease. Importantly, combinatorial synthesis also enables the choice between (i) high-throughput preparation of detergents for small scale applications and (ii) large scale preparation of individual detergents. This combinatorial synthesis strategy enables an unprecedented fine tuning of detergent properties, such as overall polarity and shape, which are determining factors in applications, such as membrane protein research. Our data show that membrane protein purification parameters, such as protein yields and activity, can be linked to overall polarity and shape. Conveniently, both parameters can be theoretically described by means of the hydrophilic-lipophilic balance (HLB) and packing parameter concepts. Both concepts are principally applicable to all non-ionic detergent classes, which facilitates the identification of widely applicable design guidelines for the predictable optimization of non-ionic detergents. Our findings permit access to a yet unexplored chemical space of the detergentome, therefore creating new possibilities for structure-property relationship studies. Seen from a broader perspective, combinatorial synthesis will facilitate the preparation of designer detergents with tailor-made properties for future applications in today's world.

Non-ionic hybrid detergents for protein delipidation

Non-ionic detergents are important tools for the investigation of interactions between membrane proteins and lipid membranes. Recent studies led to the question as to whether the ability to capture protein-lipid interactions depends on the properties of detergents or their concentration in purification buffers. To address this question, we present the synthesis of an asymmetric, hybrid detergent that combines the head groups of detergents with opposing delipidating properties. We discuss detergent properties and protein purification outcomes to reveal whether the properties of detergent micelles or the detergent concentration in purification buffers drive membrane protein delipidation. We anticipate that our findings will enable the development of rationally design detergents for future applications in membrane protein research.

Tailoring Purification and Analysis of Membrane Proteins with Modular Detergents

Detergents are crucially needed for the purification of drug targets: membrane proteins. Here, a method is described that combines tunable detergent technology and established laboratory techniques to tailor the affinity purification and structural analysis of membrane proteins.

Supramolecular Self-Associations of Amphiphilic Dendrons and Their Properties

This review presents precisely defined amphiphilic dendrons, their self-association properties, and their different uses. Dendrons, also named dendritic wedges, are composed of a core having two different types of functions, of which one type is used for growing or grafting branched arms, generally multiplied by 2 at each layer by using 1→2 branching motifs. A large diversity of structures has been already synthesized. In practically all cases, their synthesis is based on the synthesis of known dendrimers, such as poly(aryl ether), poly(amidoamine) (in particular PAMAM), poly(amide) (in particular poly(L-lysine)), 1→3 branching motifs (instead of 1→2), poly(alkyl ether) (poly(glycerol) and poly(ethylene glycol)), poly(ester), and those containing main group elements (poly(carbosilane) and poly(phosphorhydrazone)). In most cases, the hydrophilic functions are on the surface of the dendrons, whereas one or two hydrophobic tails are linked to the core. Depending on the structure of the dendrons, and on the experimental conditions used, the amphiphilic dendrons can self-associate at the air-water interface, or form micelles (eventually tubular, but most generally spherical), or form vesicles. These associated dendrons are suitable for the encapsulation of low-molecular or macromolecular bioactive entities to be delivered in cells. This review is organized depending on the nature of the internal structure of the amphiphilic dendrons (aryl ether, amidoamine, amide, quaternary carbon atom, alkyl ether, ester, main group element). The properties issued from their self-associations are described all along the review.