High Solvent Concentrations Research Articles

Modeling fixed bed bioreactors for isopropanol and butanol production using Clostridium beijerinckii DSM 6423 immobilized on polyurethane foams

Isopropanol-butanol fermentation carried out by C. beijerinckii can be improved by immobilizing cells in a fixed bed bioreactor. In this study, a fixed bed bioreactor was developed using polyurethane foams as a solid support for biofilm growth. The dilution rate was increased over time to follow biofilm development while avoiding solvent accumulation within the bioreactor. A phenomenological model was designed and successfully described batch and continuous fixed bed bioreactor dynamics. The parameters regarding biofilm detachment and attachment were estimated using a bioreactor design allowing biofilm sampling during a continuous fermentation. This last experiment was operated during 550 h and reached a maximum productivity of 1.5 g.L −1.h −1. The model prediction capacity was tested by describing a continuous fermentation in a fixed bed bioreactor column over 800 h. This latter bioreactor enabled a maximum productivity of 2.5 g.L −1 h −1 in 650 h of continuous fermentation. A high solvent concentration (13.5 g.L −1) with a butanol concentration close to the toxicity threshold (7.5 g.L −1) was obtained during the fermentation process. The process enhanced the isopropanol butanol fermentation productivity. The model properly described the batch fermentation and the immobilized cells fermentation. However, a 20% difference between experimental and modeled data was observed. Therefore, the model should be improved to better described such fermentation systems.

Measurement of Water Activity in the Presence of High Volatile Concentrations Using a Tunable Diode Laser-Single Laboratory Validation, First Action 2021.04.

Water activity is measured by equilibrating a test portion with a sealed head space and measuring the test portion temperature and the vapor density of the head space. The water activity is the ratio of head space vapor density to the saturation vapor density at test portion temperature. Headspace vapor density is typically measured using capacitance or chilled mirror sensors, but, when volatiles in significant concentration are present, these measurements may fail. Evaluate the accuracy of a tunable diode laser (TDL) for measuring the headspace vapor density and water activity of pharmaceutical preparations and food in the presence of non-aqueous volatiles. A commercial TDL water activity meter was calibrated against standards of known water activity and used to measure water activity of pharmaceutical preparations and food with high concentrations of non-aqueous volatiles. When no volatiles other than water vapor are present, this method is capable of measuring water activity with an accuracy of 0.005 or better. When high concentrations of volatiles such as ethanol, isopropanol, propylene glycol, tetrahydrofuran, or acetonitrile are present the uncertainty of the measurement increases. This is at least partly due to the uncertainty of the standards. Based on uncertainties in the water activity estimates of the water-organic mixtures, the uncertainties in water activity measurements with high concentrations of non-aqueous solvents is 0.02 or less up to mass fractions of the organic of 0.97. The theoretical background for TDL measurement of water activity is presented showing that the water vapor concentration is proportional to the area of the absorption line which is not affected by the presence of other volatiles.

Efficient Design and Sustainability Assessment of Wastewater Treatment Networks using the P-graph Approach: A Tannery Waste Case Study

In the tannery industry approximately, 30 - 35 m3 of wastewater (WW) is generated per ton of rawhide processed. The WW comprises high concentrations of salts, ammonia, dye, solvents, and chromium. Of particular interest is chromium, which has been proven to cause dermatological, developmental, and reproductive issues on exposure. Thus, there is a need for appropriate treatment of the tannery WW before it is discharged for natural remediation. However, designing a treatment process is multifaceted due to the availability of multiple technologies that can perform similar tasks and the complex composition of waste streams. This necessitates the treatment to be performed in stages namely, primary, secondary, and tertiary. In some cases, pretreatment is required to enhance the recovery in the following stages. Due to the combinatorial nature of this problem, the P-graph approach, which uses principles from graph theory, can be used to synthesize a treatment pathway by selecting appropriate technologies at each stage, while meeting required purity specifications. Furthermore, the P-graph approach can provide alternate feasible treatment structures ranked based on Economics as well as Sustainability indicators, such as the Sustainable Process Index (SPI). In this work, a tannery WW case study is investigated with multiple stages and treatment technologies. A complex maximal structure is generated comprising all possible technologies, flows, connections, bypasses, mixers, and splitters. The models for each technology involve capital and operating costs, efficiency, and SPI at each stage of the treatment process. This problem is formulated in P-graph and solved using the Accelerated Branch-and-Bound algorithm.

The Impact of Solvent Vapor on the Film Morphology and Crystallization Kinetics of Lead Halide Perovskites during Annealing.

One of the key factors for the remarkable improvements of halide perovskite solar cells over the last few years is the increased control over perovskite crystallinity and its thin film morphology. Among various processing methods, solvent vapor-assisted annealing (SVAA) has proven to be promising in achieving high-quality perovskite films. However, a comprehensive understanding of the perovskite crystallization process during SVAA is still lacking. In this work, we use a home-built setup to precisely control the SVAA conditions to investigate in detail the perovskite crystallization kinetics. By changing the solvent vapor concentration during annealing, the perovskite grain size can be tuned from 200 nm to several micrometers. We monitor the crystallization kinetics during solvent-free annealing and SVAA using in situ grazing incidence wide-angle X-ray scattering, where we find a diminished perovskite growth rate and the formation of low dimensional perovskite at the top of the perovskite layer during SVAA. Scanning electron microscopy images of the final films further suggest that the perovskite growth follows an Ostwald ripening process at higher solvent concentrations. Thus, our results will contribute to achieve a more targeted processing of perovskite films.

Solvent induced conformational changes for the altered activity of laccase: A molecular dynamics study

The growing demands of solvent-based industries like paint, pharmaceutical, petrochemical, paper and pulp, etc., have directly increased the release of effluents that are rich in hazardous aromatic compounds in the environment. A sustainable biotechnological approach utilizing laccases as biocatalyst enable in biodegradation of these aromatic toxin-rich effluents. However, this enzymatic process is ineffective as laccases lose their stability and catalytic activity at high organic solvent concentrations. In this study, molecular dynamic simulations of a novel solvent tolerant laccase, DLac from Cerrena sp. RSD1 was performed to explore the molecular-level understanding of DLac in 30%(v/v) acetone and acetonitrile. Solvent-induced conformational changes were analyzed via protein structure network, which was illustrated with respect to cliques and communities. In the presence of acetonitrile, the cliques around the active site and substrate-binding site were disjoined, thus the communities lost their network integrity. Whereas with acetone, the community near the substrate-binding site gained new residues and formed a rigidified network that corresponded to enhanced DLac’s activity. Moreover, prominent solvent binding sites were speculated, which can be probable mutation targets to further improve solvent tolerance and catalytic activity. The molecular basis behind solvent induced catalytic activity will further aid in engineering laccase for its industrial application.

Air pollutant emissions from multi jet fusion, material-jetting, and digital light synthesis commercial 3D printers in a service bureau

As additive manufacturing becomes more prevalent in industrial manufacturing facilities, so does human interaction with these machines. In this study, we characterized the size-resolved concentrations of particulate matter (PM, from ≈ 11 to 20,000 nm in size) and volatile organic compounds (VOC) resulting from a material-jetting (Projet 5500X), multi jet fusion (HP MJF 4200), and photopolymerization (Carbon 3D continuous liquid interface production). During all processes, PM concentrations were below the OSHA limits and ultrafine PM (PM0.1) concentrations were well below levels commonly observed for fused deposition modeling printers. PM and total volatile organic compound (VOC) concentrations during printing were close to background levels for the HP MJF printer and HP MJF post processing station. However, the mean particle size of the powder used (PA 12) was above the upper detection limit of the instrument (20 μm). Carbon 3D total VOC levels were highest during part post processing. Cyclic PM emissions from the Projet 5500X printer suggested higher PM emissions during cooling fan activity. VOC analysis revealed high concentrations of HP ink solvents (2-Pyrrolidinone and Triethylene glycol), potential exposure to fluorinated compounds and photoresin VOCs during Carbon 3D post-processing, and exposure to photo-resin compounds during Projet 5500X printing. This study indicates that proper exhaust and facility air exchange can limit concentrations of PM and VOCs and therefore particular attention to the building design and ventilation system should be taken into consideration for additive manufacturing facilities to mitigate potential human exposure and associated health risks.

Gas sweetening simulation and its optimization by two typical amine solutions: An industrial case study in Persian Gulf region

The selective removal of acid gases using amine-based solutions is a significant process in the petroleum and natural gas industries. This work investigates the effectiveness of two common chemical solvents of Methyl Diethanolamine (MDEA) and Diethanolamine (DEA) and the blends of them with different mass concentration and circulation rate to absorb H2S and CO2 from natural gas in an existing industrial process plant in Phase I of the South Pars Gas Complex (SPGC) located in Persian Gulf region. This sweetening unit was simulated for H2SCO2MDEAH2O and H2SCO2DEAH2O systems incorporated into the Amine Package in the Promax simulator. Sensitivity analyses were performed on circulation rate (140–350 m3/h for MDEA and 300–520 m3/h for DEA), concentration (30–65 wt.% for MDEA and 30–40 wt.% for DEA) of amine solution and the MDEA to DEA ratio (eight different cases) which are the main factors improving process performance. The effect of these factors has been separately studied on the parameters such as acid gas content in the sweetened gas, reboiler duty, acid gas loadings, amine carryover and pH. The results confirmed that higher solvent concentration and circulation rate are beneficial to the sour gas absorption process. However, they require greater corresponding energy to regenerate rich-loaded solution in the reboiler. It enhances the operational costs. Based on the results, the optimal concentration and flow rate of MDEA and DEA solvents was obtained at 40 and 32 wt.% and 150 and 350 m3/h, respectively.

Assessment of Antimicrobial Activity of Pomegranate, Cranberry, and Black Chokeberry Extracts against Foodborne Pathogens.

Herbal and plant extracts are being applied to a wide range of foods against different types of foodborne pathogens. In the present study, ethanolic and aqueous extracts of different concentrations (5% v/v, 10% v/v, and 20% v/v) from cranberry (Vaccinium macrocarpon), black chokeberry (Aronia melanocarpa), and pomegranate (Punica granatum L.) plants were applied in five concentrations (62.5 to 1000 mg/mL) against foodborne strains of Staphylococcus aureus, Escherichia coli, and Streptococcus pyogenes. The results revealed that a low concentration of solvents (5% v/v) did not exhibit decreased antimicrobial activity in comparison with higher solvent concentrations (10% and 20% v/v). Additionally, both aqueous and ethanolic extracts were highly effective against pathogens even in their low concentrations (62.5 mg/mL and 125 mg/mL). Likewise, the extracts exhibited promising results (aqueous extracts of pomegranate, cranberry, and black chokeberry in a food-compatible concentration of 2% w/v) were applied to raw pork meatball production, and their antimicrobial activity was recorded versus Enterobacteriaceae, total mesophilic bacteria (TMB), lactic acid bacteria (LAB), Staphylococcus spp., Pseudomonas spp., and yeasts/molds. The outcome demonstrated that meatballs that contained aqueous extracts of pomegranate were more resistant to spoilage compared to all of the other samples, as it was preserved for more days. Likewise, these extracts of a plant origin could be used as natural preservatives in meat products, even in their low concentrations.

Simultaneous Biogas Upgrade and Production of Precipitated Calcium Carbonate

Biogas upgrading is a necessary step to remove impurities and increase a calorific value of biogas before it can be used as a proper energy source. The most significant impurity in raw biogas is typically carbon dioxide, composing up to 50% of biogas volume. Carbon dioxide capture is therefore an important part of the upgrading process which in turn raises the question of the availability of final carbon storage. This problem can be addressed by using calcium hydroxide solution or other lime-based solvents as scrubber in carbon dioxide capture via carbonation where precipitated calcium carbonate (PCC) is formed as a by-product. This paper reviews the viability of packed column, bubble column, and spray column for simultaneous biogas purification by CO2 capture and PCC synthesis, as well as examining various parameters that affect both carbon dioxide capture and the production of PCC. Among the three reviewed types of contactors, only packed column is deemed unsuitable for the simultaneous process. The optimal condition for both carbon dioxide scrubbing efficiency and PCC yield can be obtained by using a high liquid flow rate, low gas flow rate, and high solvent concentration. However, the desired characteristics of PCC should be considered in determining the operating parameters as the said characteristics such as crystal phase, morphology, and particle size are affected by several operating parameters, namely gas flow rate, solvent concentration, temperature, size of bubbles, and concentration of additives.

Effect of Monoethanolamine Concentration on CO2 Removal using Continuous High Frequency Ultrasonic Reactor

Chemical absorption is the most common technology used for the process of CO2 removal from natural gas due to its ability to reduce the level of the acid gas to a very low level as well as higher mass transfer performance due to the chemical kinetic reaction. Higher solvent concentration resulted in higher capacity to remove CO2, however reduces the diffusivity as well as its ability to spread on the packing due to its high solvent viscosity. This has hindered the used of high viscosity solvent in the operation of conventional packed column. However, recent technology of using high frequency ultrasonic irradiation for absorption process has shown possibility to operate high viscosity solvent due to the absence of packing in the reactor. From this work, it is shown that high viscosity solvent does not affect the mass transfer performance under ultrasonic irradiation due to the presence of acoustic streaming, fountain and atomization that reduced the film resistance thus increases the diffusivity. This work has demonstrated that this technology has high flexibility of solvent selection for the absorption process.

Development of a structure-analysis pipeline using multiple-solvent crystal structures of barrier-to-autointegration factor.

The multiple-solvent crystal structure (MSCS) approach uses high concentrations of organic solvents to characterize the interactions and effects of solvents on proteins. Here, the method has been further developed and an MSCS data-handling pipeline is presented that uses the Detection of Related Solvent Positions (DRoP) program to improve data quality. DRoP is used to selectively model conserved water molecules, so that an advanced stage of structural refinement is reached quickly. This allows the placement of organic molecules more accurately and convergence on high-quality maps and structures. This pipeline was applied to the chromatin-associated protein barrier-to-autointegration factor (BAF), resulting in structural models with better than average statistics. DRoP and Phenix Structure Comparison were used to characterize the data sets and to identify a binding site that overlaps with the interaction site of BAF with emerin. The conserved water-mediated networks identified by DRoP suggested a mechanism by which water molecules are used to drive the binding of DNA. Normalized and differential B-factor analysis is shown to be a valuable tool to characterize the effects of specific solvents on defined regions of BAF. Specific solvents are identified that cause stabilization of functionally important regions of the protein. This work presents tools and a standardized approach for the analysis and comprehension of MSCS data sets.

Fungal mycelia functionalization with halloysite nanotubes for hyphal spreading and sorption behavior regulation: A new bio-ceramic hybrid for enhanced water treatment

Filamentous fungi are believed to remove a wide range of environmental xenobiotics due to their characteristically non-specific catabolic metabolisms. Nonetheless, irregular hyphal spreading can lead to clogging problems in treatment facilities and the dependence of pollutant bioavailability on hyphal surface features severely limits their applicability in water treatment. Here, we propose a scalable and facile methodology to structurally modify fungal hyphae, allowing for both the maximization of pollutant sorption and fungal pellet morphology self-regulation. Halloysite-doped mycelium architectures were efficiently constructed by dipping Aspergillus fumigatus pellets in halloysite nanotube-dispersed water. Ultrastructure analyses using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy revealed that the nanotubes were mainly attached to the outer surface of the pellets. Fungal viability and exoenzyme production were hardly affected by the halloysites. Notably, nanotube doping appeared to be extremely robust given that detachments rarely occurred even in high concentrations of organic solvents and salt. It was also demonstrated that the doped halloysites weakened hyphal growth-driven gelation, thus maintaining sphere-like pellet structures. The water treatment potential of the hybrid fungal mycelia was assessed through both cationic toxic organic/inorganic-contaminated water and real dye industry wastewater clean-ups. Aided by the mesoporous halloysite sites on their surface, the removal abilities of the hybrid structures were significantly enhanced. Moreover, inherent low sorption ability of HNT for heavy metals was found to be overcome by the aid of fungal mycelia. Finally, universal feature of the dipping-based doping way was confirmed by using different filamentous fungi. Given that traditional approaches to effectively implement fungus-based water treatment are based mostly on polymer-based immobilization techniques, our proposed approach provides a novel and effective alternative via simple doping of living fungi with environmentally-benign clays such as halloysite nanotubes.

Utilization of turmeric residue for the preparation of ceramic foam

Turmeric residue, a solid waste discharged from the curcuminoids industry, is difficult to recover due to high concentrations of strong acids, organic solvents, and plant fibers. In this study, organic turmeric residue was used as the main raw material for the preparation of ceramic foam, in comparison with inorganic granite scraps. The bulk density, compressive strength, and thermal conductivity of ceramic foam were evaluated. And the microstructure, phase assemblage, and reaction at the high temperature were respectively characterized by computed tomography, X-ray diffraction, thermal analysis. The results revealed that the addition of turmeric residue was conducive to the formation of pore and the generation of amorphous glass phase, thereby improving the lightweight, mechanical performance, and thermal insulation. This study would provide a new perspective for the utilization of turmeric residue and the preparation of ceramic foam.

Organic solvent stability and long-term storage of myoglobin-based carbene transfer biocatalysts.

Recent years have witnessed a rapid increase in the application of enzymes for chemical synthesis and manufacturing, including the industrial-scale synthesis of pharmaceuticals using multienzyme processes. From an operational standpoint, these bioprocesses often require robust biocatalysts capable of tolerating high concentrations of organic solvents and possessing long shelflife stability. In this work, we investigated the activity and stability of myoglobin (Mb)-based carbene transfer biocatalysts in the presence of organic solvents and after lyophilization. Our studies demonstrate that Mb-based cyclopropanases possess remarkable organic solvent stability, maintaining high levels of activity and stereoselectivity in the presence of up to 30%-50% (v/v) concentrations of various organic solvents, including ethanol, methanol, N,N-dimethylformamide, acetonitrile, and dimethyl sulfoxide. Furthermore, they tolerate long-term storage in lyophilized form, both as purified protein and as whole cells, without significant loss in activity and stereoselectivity. These stability properties are shared by Mb-based carbene transferases optimized for other type of asymmetric carbene transfer reactions. Finally, we report on simple protocols for catalyst recycling as whole-cell system and for obviating the need for strictly anaerobic conditions to perform these transformations. These findings demonstrate the robustness of Mb-based carbene transferases under operationally relevant conditions and should help guide the application of these biocatalysts for synthetic applications.

Mass Transfer Performance Study for CO2 Absorption into Non-Precipitated Potassium Carbonate Promoted with Glycine Using Packed Absorption Column

The removal of carbon dioxide (CO2) at offshore operation requires an absorption system with an environmentally friendly solvent that can operate at elevated pressure. Potassium carbonate promoted with glycine, PCGLY, is a green solvent that has potential for offshore applications. For high solvent concentrations at elevated pressure, the by-product of CO2 absorption consists of precipitates that increase operational difficulty. Therefore, this study was done to assess the CO2 absorption performance of non-precipitated PCGLY with concentration 15wt%PC+3wt%GLY, which is known to have comparable solubility performance with MDEA. A packed absorption column was used to identify the CO2 removal efficiency, mass transfer coefficient in liquid film, k l a e , and overall volumetric mass transfer coefficient, K G a v . A simplified rate-based model was used to determine k l a e and K G a v based on the experimental data with a maximum MAE value, 0.057. The results showed that liquid flow rates and liquid temperature gives significant effects on the k l a e and K G a v profile, whereas gas flow rate and operating pressure had little effect. The CO2 removal efficiency of PCGLY was found to be 77%, which was only 2% lower than 1.2 kmol/m3 MDEA. K G a v of PCGLY is comparable with MDEA. The absorption process using PCGLY shows potential in the CO2 sweetening process at offshore.

Effect of Solvent Concentration on Scaling Butane Solvent Enhanced Oil Recovery Processes Using Reservoir Simulation

Understanding scaling of enhanced oil/bitumen recovery processes is essential in moving laboratory scale experimental results to field scale. Scaling theory for thermal processes is well understood and has been applied to steam processes. However, scaling of hybrid steam (thermal) /solvent (mass transfer) processes is still not well defined nor well understood. This paper investigates the scaling behavior of hybrid steam/butane gravity drainage processes using reservoir simulation (commercial thermal compositional simulator CMG STARSTM). Previous research has used reservoir simulation to confirm scaling groups for waterflooding. A similar strategy was used in this study whereby the scaling of a hybrid (steam) solvent oil recovery process was examined using reservoir simulations at three different reservoir scales: lab scale, semi-field scale and field scale to examine the influence of the mass transfer mechanisms of diffusion and dispersion on the scalability of the process. In particular, the influence of butane solvent concentration on scaling a steam/butane gravity drainage process was investigated by considering several butane mole fraction concentrations injected with steam (1%, 2%, 5%, 7%, 10%, 15%, 21%, 25% and 50%). Temperature contours, and mole fraction contours of butane in both the oil and gas phases were examined for various solvent injection concentrations to examine scalability. Numerical results are provided with no diffusion and dispersion, diffusion only, dispersion only and with both diffusion and dispersion added to the simulations. Results confirmed scalability of the process with no capillary effects when the simulation results were non-dimensionalized, although there were some issues with material balance errors in some of the simulation results particularly at high solvent concentrations. For low injection concentrations, the contours were almost identical (indicating scalability) for the three scales for the operating condition studied. In addition, capillary effects were also studied, and similar to scaling thermal processes, the capillarity effects influenced scalability of the process under the conditions studied particularly at higher injection concentrations. Scalability using reservoir simulation was generally preserved with low injection concentrations, but unusual behavior was observed at higher injection concentrations (>5%). Oil recovery curves were non-dimensionalized to make comparisons amongst the three scales. The oil recovery curves displayed an unusual S-shaped behavior at higher injection concentrations when capillary effects were included especially for the lab and semi-field scales. In all cases when all of the mechanisms are included (diffusion, dispersion and capillary effects), Scale 1 shows a much faster recovery than Scale 3 which suggests that the lab scale might temporally overestimate the field scale recovery for this particular process scenario.

Periprotein lipidomes of Saccharomyces cerevisiae provide a flexible environment for conformational changes of membrane proteins.

Yeast tolerates a low pH and high solvent concentrations. The permeability of the plasma membrane (PM) for small molecules is low and lateral diffusion of proteins is slow. These findings suggest a high degree of lipid order, which raises the question of how membrane proteins function in such an environment. The yeast PM is segregated into the Micro-Compartment-of-Can1 (MCC) and Pma1 (MCP), which have different lipid compositions. We extracted proteins from these microdomains via stoichiometric capture of lipids and proteins in styrene-maleic-acid-lipid-particles (SMALPs). We purified SMALP-lipid-protein complexes by chromatography and quantitatively analyzed periprotein lipids located within the diameter defined by one SMALP. Phospholipid and sterol concentrations are similar for MCC and MCP, but sphingolipids are enriched in MCP. Ergosterol is depleted from this periprotein lipidome, whereas phosphatidylserine is enriched relative to the bulk of the plasma membrane. Direct detection of PM lipids in the 'periprotein space' supports the conclusion that proteins function in the presence of a locally disordered lipid state.

Tuning Enzyme Activity for Nonaqueous Solvents: Engineering an Enantioselective "Michaelase" for Catalysis in High Concentrations of Ethanol.

Enzymes have evolved to function under aqueous conditions and may not exhibit features essential for biocatalytic application, such as the ability to function in high concentrations of an organic solvent. Consequently, protein engineering is often required to tune an enzyme for catalysis in non‐aqueous solvents. In this study, we have used a collection of nearly all single mutants of 4‐oxalocrotonate tautomerase, which promiscuously catalyzes synthetically useful Michael‐type additions of acetaldehyde to various nitroolefins, to investigate the effect of each mutation on the ability of this enzyme to retain its “Michaelase” activity in elevated concentrations of ethanol. Examination of this mutability landscape allowed the identification of two hotspot positions, Ser30 and Ala33, at which mutations are beneficial for catalysis in high ethanol concentrations. The “hotspot” position Ala33 was then randomized in a highly enantioselective, but ethanol‐sensitive 4‐OT variant (L8F/M45Y/F50A) to generate an improved enzyme variant (L8F/A33I/M45Y/F50A) that showed great ethanol stability and efficiently catalyzes the enantioselective addition of acetaldehyde to nitrostyrene in 40 % ethanol (permitting high substrate loading) to give the desired γ‐nitroaldehyde product in excellent isolated yield (89 %) and enantiopurity (ee=98 %). The presented work demonstrates the power of mutability‐landscape‐guided enzyme engineering for efficient biocatalysis in non‐aqueous solvents.

Supported Lipid Membranes at the Au‐Buffer Interface by Solvent Exchange: The Effect of Initial Solvent Concentration

The recently introduced solvent‐assisted lipid bilayer (SALB) formation method has proved a fast, simple, and versatile alternative to vesicle fusion in forming membrane‐mimicking platforms on solid supports such as SiO2, TiO2, graphene, and Au. This confers SALB with a broad applicability for developing biomaterial coatings for implants, biomimetic cell culture platforms, and cancer diagnostics. Although significant understanding on the interplay of the parameters controlling SALB (type of solvent, lipid concentration, and flow rate) has been achieved to date, there still exists several unexplored specific questions to be tackled. Herein, the question of how the initial solvent concentration affects the formation and organization of (zwitterionic) lipid membranes formed by SALB on Au surfaces is addressed. Using quartz crystal microbalance with dissipation monitoring, differences in frequency and dissipation responses are observed upon dissolving the lipid compound dimyristoyl phosphatidylcholine (DMPC) in either pure isopropanol or mixtures of different volume ratios of isopropanol and aqueous buffer. At high and medium initial solvent concentrations, thin and rigid supported lipid bilayers (SLBs) are typically formed at the Au–liquid interface, irrespective of the lipid structures formed in bulk, whereas at low solvent concentrations, irreversible vesicle adsorption takes place hindering the homogeneous SLB formation.

Exploration of Missing Proteins by a Combination Approach to Enrich the Low-Abundance Hydrophobic Proteins from Four Cancer Cell Lines.

The mission of the Chromosome-Centric Human Proteome Project (C-HPP) to discover missing proteins (MPs) has become increasingly difficult due to the remaining low-abundance, high-hydrophobicity, or low-molecular-weight MPs. We have reported two approaches to resolve these identification problems for the low-abundance and high-hydrophobicity MPs, respectively. In this study, to improve the identification of low-abundance MPs with high hydrophobicity, we combined two approaches and obtained MPs from several different cancer cell lines. Their membrane fractions were isolated by ultracentrifugation, and the low-abundance proteins were enriched at the protein level with the ProteoMiner kit. After that, the peptides from the enriched proteins were separated by high concentrations of organic solvents according to their hydrophobicity as the first dimension of separation at the peptide level, and the second and third dimensions of separation involved a high pH reversed-phase and an acid reversed-phase column, respectively. In total, 16 MPs (at least two non-nested unique peptides with ≥9 amino acids) with 61 unique peptides were identified from four human cancer cell lines, including 2, 8, 2, and 7 MPs from HeLa, HCT116, SNU-1, and HepG2 cells, respectively. Furthermore, all MPs were verified with two non-nested unique peptides through parallel reaction monitoring (PRM) by matching the peptides with their chemically synthesized peptides. Interestingly, two additional MPs were verified from the same cell line by PRM assay, although the two non-nested unique peptides with ≥9 amino acids for each MP were identified from different MS injections or cell lines by data-dependent acquisition (DDA). Thus, a total of 18 MPs were dug out in this study. The data are available via ProteomeXchange (PXD014058) and PeptideAtlas (PASS01388).