Rationalizing the Optimization of Detergents for Membrane Protein Purification.

Membrane protein purification by means of detergents is key to isolating membrane-bound therapeutic targets. The role of the detergent structure in this process, however, is not well understood. Detergents are optimized empirically, leading to failed preparations, and thereby raising costs. Here we evaluate the utility of the hydrophilic-lipophilic balance (HLB) concept, which was introduced by Griffin in 1949, for guiding the optimization of the hydrophobic tail in first-generation, dendritic oligoglycerol detergents ([G1] OGDs). Our findings deliver qualitative HLB guidelines for rationalizing the optimization of detergents. Moreover, [G1] OGDs exhibit strongly delipidating properties, regardless of the structure of the hydrophobic tail, which delivers a methodological enabling step for investigating binding strengths of endogenous lipids and their role for membrane protein oligomerization. Our findings will facilitate the analysis of challenging drug targets in the future.

Interfaces with Fluorinated Amphiphiles: Superstructures and Microfluidics.

This Minireview discusses recent developments in research on the interfacial phenomena of fluorinated amphiphiles, with a focus on applications that exploit the unique and manifold interfacial properties associated with these amphiphiles. Most notably, fluorinated amphiphiles form stable aggregates with often distinctly different morphologies compared to their nonfluorinated counterparts. Consequently, fluorinated surfactants have found wide use in high-performance applications such as microfluidic-assisted screening. Additionally, their fluorine-specific behaviour at solid/liquid interfaces, such as the formation of superhydrophobic coatings after deposition on surfaces, will be discussed. As fluorinated surfactants and perfluorinated materials in general pose potential environmental threats, recent developments in their remediation based on their adsorption onto fluorinated surfaces will be evaluated.

Walking instead of standing.

Background: Leg discomfort is common in the general population. Volume increase and discomfort in the lower legs especially occur in occupations with long standing or sitting periods and less movement. Are both related to each other? Patients and methods: A time-controlled standing period of 15 min was performed in this nonrandomized controlled study to investigate the change and temporal relationship of volume increase and the occurrence of lower leg discomfort. Sensations of discomfort and the urge to move were queried using a numerical rating scale from 0 to 10 (NRS). Correlation analysis was conducted between the lower leg volume and the data regarding the discomfort and urge to move in each subject. Further, linear mixed effect models were performed to detect a causal relationship between the lower leg volume and the sensations of discomfort/urge to move in the standing period. Results: Lower leg volume increased by an average of 63 ml (p<0.001) during the standing period. The sensations of discomfort increased by a mean of 3.46 points on the NRS (p<0.001) during orthostasis. Participants' urge to move increased by 3.47 points on the NRS (p<0.001) during the standing period. A significant correlation was shown between the increase of lower leg volume and the occurrence of discomfort sensation in 9 out of 15 subjects (p<0.05) and between the increase of lower leg volume and the urge to move in 11 out of 15 subjects (p<0.05). Association was shown between volume increase and symptoms in linear mixed effects models. Conclusions: Prolonged standing with lack of movement leads to an increase in the lower leg volume and a sensation of discomfort in venous healthy subjects. Causal relationships are indicated between these variables by linear mixed effects models.

Fluorinated dendritic amphiphiles, their stomatosome aggregates and application in enzyme encapsulation.

Enzymes are more selective and efficient than synthetic catalysts but are limited by difficult recycling. This is overcome by immobilisation, namely through encapsulation, with the main drawback of this method being slow diffusion of products and reactants, resulting in effectively lowered enzyme activity. Fluorinated dendritic amphiphiles were reported to self-assemble into regularly perforated bilayer vesicles, so-called "stomatosomes". It was proposed that they could be promising novel reaction vessels due to their increased porosity while retaining larger biomolecules at the same time. Amphiphiles were synthesised and their aggregation was analysed by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) in buffered conditions necessary for enzyme encapsulation. Urease and albumin were encapsulated using the thin-film hydration method and investigated by confocal and time-gated stimulated emission depletion microscopy (gSTED). Their release was then used to probe the selective retention of cargo by stomatosomes. Free and encapsulated enzyme activity were compared and their capacity to be reused was evaluated using the Berthelot method. Urease was successfully encapsulated, did not leak out at room temperature, and showed better activity in perforated vesicles than in closed vesicles without perforations. Encapsulated enzyme could be reused with retained activity over 8 cycles using centrifugation, while free enzyme had to be filtrated. These results show that stomatosomes may be used in enzyme immobilisation applications and present advantages over closed vesicles or free enzyme.

Influence of compression stockings on the sensation of discomfort and the volume of the lower legs in healthy subjects during standing load.

BACKGROUND: Edema caused by orthostasis is a common clinical picture in the medical and occupational context. Medical compression therapy with compression stockings (CS) is considered a conservative therapeutic standard in edema therapy. The effect of CS on leg discomfort and the increase of the lower leg volume during a standing load still remains questionable. In addition, it is not entirely known whether there is a correlation between volume increase and discomfort in these individuals. METHOD: A timed, controlled standing load of 15 min was conducted by the participants in this non-randomized controlled study to analyze the change in and correlation between lower leg volume increase and the occurrence of lower leg discomfort under compression therapy. Below-knee CS with an interface pressure of 23-32 mmHg were used. The lower leg volume was measured following previous studies using an optical three-dimensional volume (ml) measurement system, and sensations of discomfort and the urge to move were asked about using a numerical rating scale (NRS) of 0-10. The subjects conducted a leg movement for 15 s immediately after the standing period; the data were collected again subsequently. A correlation was calculated between the lower leg volume and the data regarding the discomfort and urge to move for each participant. The experiments had already been performed as part of a previous study including the same subjects who did not wear CS. The results of the study conducted here were compared with those of the participants who did not wear CS to investigate the effect of the CS. RESULTS: Lower leg volume increased by an average of 27 ml (p < 0.001) (without CS: by 63 ml) during standing load in the right leg. During the leg movement after standing load, the lower leg volume increased by 5 ml (n.s.). The sensations of discomfort during the orthostasis increased by 2.6 points on the NRS (p < 0.001) (without CS: by 3.46 points) and decreased by 1.67 points (p < 0.001) during the leg movement shortly after the standing period. Participants' urge to move increased by 3.73 points on the NRS (p < 0.001) (without CS: by 3.47 points) while the participants performed the standing period and decreased by 2.73 points (p < 0.001) during the final movement exercise. A weakly significant correlation could be demonstrated between the increase in the lower leg volume and the occurrence of discomfort in 6 out of 13 subjects (p < 0.1), and between the increase in the lower leg volume and the urge to move in 8 out of 15 subjects (p < 0.1). CONCLUSION: Standing loads and lack of movement lead to an increase in the lower leg volume and sensation of discomfort in venous healthy subjects wearing CS, which are reduced by wearing them (p < 0.001). A weakly significant mathematical correlation (Pearson's correlation coefficient) could be shown between the increase in the lower leg volume and the occurrence of the urge to move in 8 out of 15 subjects (p < 0.1) and between the increase in lower leg volume and the occurrence of leg discomfort in 6 out of 13 subjects (p < 0.1).