Pore Sites Research Articles

Cryo-EM structure of the zinc-activated channel (ZAC) in the Cys-loop receptor superfamily

Cys-loop receptors are a large superfamily of pentameric ligand-gated ion channels with various physiological roles, especially in neurotransmission in the central nervous system. Among them, zinc-activated channel (ZAC) is a Zn2+-activated ion channel that is widely expressed in the human body and is conserved among eukaryotes. Due to its gating by extracellular Zn2+, ZAC has been considered a Zn2+ sensor, but it has undergone minimal structural and functional characterization since its molecular cloning. Among the families in the Cys-loop receptor superfamily, only the structure of ZAC has yet to be determined. Here, we determined the cryo-EM structure of ZAC in the apo state and performed structure-based mutation analyses. We identified a few residues in the extracellular domain whose mutations had a mild impact on Zn2+ sensitivity. The constriction site in the ion-conducting pore differs from the one in other Cys-loop receptor structures, and further mutational analysis identified a key residue that is important for ion selectivity. In summary, our work provides a structural framework for understanding the ion-conducting mechanism of ZAC.

Facial pore refining by targeting dermal and epidermal functions: Assessment across age and gender.

Conspicuous facial pores are benign but represent a cosmetic concern for men and women. Recent works described dermal and epidermal impairments as clinical causes of enlarged pores. Morphological modifications of skin at the site of pores were associated with collagen density loss, possible alteration of extracellular matrix and abnormal differentiation of keratinocytes. A composition containing mannose-6-phosphate (Active Complex) was designed to address these different aspects of pore enlargement. Invitro and exvivo evaluations were conducted in different models mimicking disturbance of dermal and epidermal functions. The pore refining activity of Active Complex was assessed in two clinical trials studying a Caucasian women cohort and an Asian men cohort. At the dermal level, Active Complex upregulated collagen I and decorin synthesis, and genes encoding collagens I, III, V, VII, XVII; suggesting its ability to favor collagen fiber organization and anchorage. The downregulation of matrix metalloprotease, involved in extracellular matrix degradation, reinforced the protective effect of Active Complex in the dermis. Active Complex down modulated differentiation markers in keratinocytes as well as genes involved in cell renewal. Study of reconstructed human epidermis modeling keratinocyte hyperproliferation revealed that Active Complex mitigated two markers of this state: number of nuclei in the stratum corneum and involucrin expression. Clinical trials confirmed the pore refining activity of Active Complex on men and women of different ages and ethnicities; -24% total skin pore area after 56 days of application on women, and -30.2% on men after 7 days. This work demonstrates the interest to target dermal and epidermal modifications described in conspicuous pore area, especially dermis fiber organization, to address this cosmetic concern.

Translation arrest cancellation of VemP, a secretion monitor in Vibrio, is regulated by multiple cis and trans factors, including SecY

VemP is a secretory protein in the Vibrio species that monitors cellular protein-transport activity through its translation arrest, allowing expression of the downstream secD2-secF2 genes in the same operon, which encode components of the protein translocation machinery. When cellular protein-transport function is fully active, secD2/F2 expression remains repressed as VemP translation arrest is canceled immediately. The VemP arrest-cancellation occurs on the SecY/E/G translocon in a late stage in the translocation process and requires both trans-factors, SecD/F and PpiD/YfgM, and a cis-element, Arg-85 in VemP; however, the detailed molecular mechanism remains elusive. This study aimed to elucidate how VemP passing through SecY specifically monitors SecD/F function. Genetic and biochemical studies showed that SecY is involved in the VemP arrest-cancellation and that the arrested VemP is stably associated with a specific site in the protein-conducting pore of SecY. VemP-Bla reporter analyses revealed that a short hydrophobic segment adjacent to Arg-85 plays a critical role in the regulated arrest-cancellation with its hydrophobicity correlating with the stability of the VemP arrest. We identified Gln-65 and Pro-67 in VemP as novel elements important for the regulation. We propose a model for the regulation of the VemP arrest cancellation by multiple cis-elements and trans-factors with different roles.

Customizing Pore Structure and Lithiophilic Sites Dual-Gradient Free-Standing 3D Lithium-Based Anode to Enable Excellent Lithium Metal Batteries.

Developing 3D hosts is one of the most promising strategies for putting forward the practical application of lithium(Li)-based anodes. However, the concentration polarization and uniform electric field of the traditional 3D hosts result in undesirable "top growth" of Li, reduced space utilization, and obnoxious dendrites. Herein, a novel dual-gradient 3D host (GDPL-3DH) simultaneously possessing gradient-distributed pore structure and lithiophilic sites is constructed by an electrospinning route. Under the synergistic effect of the gradient-distributed pore and lithiophilic sites, the GDPL-3DH exhibits the gradient-increased electrical conductivity from top to bottom. Also, Li is preferentially and uniformly deposited at the bottom of the GDPL-3DH with a typical "bottom-top" mode confirmed by the optical and SEM images, without Li dendrites. Consequently, an ultra-long lifespan of 5250h of a symmetrical cell at 2mA cm-2 with a fixed capacity of 2 mAh cm-2 is achieved. Also, the full cells based on the LiFePO4, S/C, and LiNi0.8Co0.1Mn0.1O2 cathodes all exhibit excellent performances. Specifically, the LiFePO4-based cell maintains a high capacity of 136.8 mAh g-1 after 700 cycles at 1C (1C = 170mA g-1) with 94.7% capacity retention. The novel dual-gradient strategy broadens the perspective of regulating the mechanism of lithium deposition.

Sonochemical synthesized Gd4Al2O9 nanostructures modified with carbonous compounds for electrochemical hydrogen storage application

In recent times, there has been a significant focus on research into the creation of an environmentally sustainable and pollution-free hydrogen storage cell power system. Over the last ten years, a number of significant advancements in energy storage methods have been developed, impacting research, innovation, and the likely course for furthering our understanding of energy storage. We suggest a hydrogen energy storage device built using cutting-edge electrochemical techniques and electrode materials. As active materials, a range of nanocomposites based on gadolinium aluminate (Gd4Al2O9) and carbonous compounds were created. For the fabrication of Gd4Al2O9 nanostructures, ultrasonic radiation was used in the presence of Schiff-base ligands of N,N′-bis(salicylidene)ethylenediamine (H2Salen), N,N0-disalicylidene-1,4-di-aminobutane (H2Salbn) and N,N′-bis(salicylidene)-1,2-phenylenediamine (H2Salophen). Diverse carbon-based materials of g-C3N4, GO and CNT were utilized for designing nanocomposites. After 15 cycles, the hydrogen storage capacities of pure Gd4Al2O9 were found to be 121 mAhg−1. Then, in the fifteenth cycle, the nanocomposites' capacity rose to 278 mAhg−1 at a current of 1 mA for designed nanocomposite with GO. The CNT can increase the capacity to 302 mAhg−1 (11th cycle) but the fading capacity was occurred after 11th cycle to 112 (15th cycle). The g-C3N4 led to decrease in capacity due to blocking the pore and active sites of Gd4Al2O9 nanostructures.

A 2D Metal-Free Inorganic Covalent Framework: Synthesis, Crystal Structure, and Room-Temperature Phosphorescence.

The synthesis, crystal structure and room-temperature phosphorescence (RTP) of a 2D metal-free inorganic covalent framework ((H2en) [B5O8(OH)], named as CityU-12, and en represents for ethylenediamine) are reported. The precise structure information of CityU-12 has been disclosed through both single-crystal X-ray diffraction (SCXRD) analysis and low-dose high-resolution transmission electron microscopy (LD-HRTEM) study. The SCXRD results show that CityU-12 composes of 2D anionic B─O-based covalent inorganic frameworks with protonated ethylenediamine locating in the pore sites of 2D B─O layers while LD-HRTEM suggests that CityU-12 has an interplanar distance of 0.60nm for (00 ) crystal plane and 0.60nm for (10 ) crystal plane. The optical studies show that CityU-12 is an excellent nonconventional RTP material with the emission peak at 530nm and a lifetime of 1.5s. The quantum yield is 84.6% and the afterglow time is as long as 2.5s. This work demonstrates that metal-free B─O frameworks can be promising nonconventional phosphors for RTP.

Conformational photo-trapping in NaV1.5: Inferring local motions at the “inactivation gate”

Rapid and effectual inactivation in voltage-gated sodium channels is required for canonical action-potential firing. This “fast” inactivation arises from swift and reversible protein conformational changes that utilize transmembrane segments and the cytoplasmic linker between channel domains III and IV. Until recently, fast inactivation had been accepted to rely on a “ball-and-chain” mechanism whereby a hydrophobic triplet of DIII-IV amino acids (IFM) impairs conductance by binding to a site in central pore of the channel made available by channel opening. New structures of sodium channels have upended this model. Specifically, cryo-electron microscopic structures of eukaryotic sodium channels depict a peripheral binding site for the IFM motif, outside of the pore, opening the possibility of a yet unidentified allosteric mechanism of fast-inactivation gating. We set out to study fast inactivation by photo-trapping human sodium channels in various functional states under voltage control. This was achieved by genetically encoding the crosslinking unnatural amino acid benzophenone phenylalanine at various sites within the DIII-IV linker in the cardiac sodium channel NaV1.5. These data show dynamic state- and positional-dependent trapping of the transient conformations associated with fast inactivation, each yielding different phenotypes and rates of trapping. These data reveal distinct conformational changes that underlie fast inactivation and point to a dynamic environment around the IFM locus.

Tabernanthalog and ibogainalog inhibit the α7 and α9α10 nicotinic acetylcholine receptors via different mechanisms and with higher potency than the GABAA receptor and CaV2.2 channel

In this study, we have investigated the pharmacological activity and structural interaction of two novel psychoplastogens, tabernanthalog (TBG) and ibogainalog (IBG) at heterologously-expressed rat (r) and human (h) nicotinic acetylcholine receptors (nAChRs), the rα1β2γ2L γ-aminobutyric acid type A receptor (GABAAR), and the human voltage-gated N-type calcium channel (CaV2.2 channel). Both compounds inhibited the nAChRs with the following receptor selectivity: α9α10 > α7 > α3β2 ≅ α3β4, indicating that β2/β4 subunits are relatively less important for their activity. The potencies of TBG and IBG were comparable at hα7 and hα9α10 subtypes, and comparable to their rat counterparts. TBG- and IBG-induced inhibition of rα7 was ACh concentration-independent and voltage-dependent, whereas rα9α10 inhibition was ACh concentration-dependent and voltage-independent, suggesting that they interact with the α7 ion channel pore and α9α10 orthosteric ligand binding site, respectively. These results were supported by molecular docking studies showing that at the α7 model TBG forms stable interactions with luminal rings at 9′, 13′, and 16′, whereas IBG mostly interacts with the extracellular-transmembrane junction. In the α9α10 model, however, these compounds interacted with several residues from the principal (+) and complementary (–) sides in the transmitter binding site. Ibogaminalog (DM506) also interacted with a non-luminal site at α7, and one α9α10 orthosteric site. TBG and IBG inhibited the GABAAR and CaV2.2 channels with 10 to 30-fold lower potencies. In sum, we show that TBG and IBG inhibit the α7 and α9α10 nAChRs by noncompetitive and competitive mechanisms, respectively, and with higher potency than the GABAAR and CaV2.2 channel.

Engineering ethane-trapping metal-organic framework for efficient ethylene separation under high humid conditions

One-step removing trace amounts of ethane (C2H6) during ethylene (C2H4) production using high-efficiency adsorption separation technology is in high demand in the petrochemical industry. This puts forward higher requirements for the rational design and preparation of C2H6-selective adsorbents that possess exceptional trapping capacity, selectivity, and stability. Herein, a stable material isomorphic to UiO-67 (known as UiO-67-DF) has been constructed to enhance the accessibility of adsorption sites in non-polar pores. This material demonstrates impressive improvement in both C2H6 adsorption capacity (3.65 mmol/g) and C2H6/C2H4 selectivity (1.9), outperforming UiO-67 (3.01 mmol/g and 1.5, respectively). Moreover, UiO-67-DF exhibits exceptional stability as evidenced by breakthrough experiments and shows its effectiveness in separating C2H6/ C2H4 mixtures at high temperatures and high humidity (316 K and RH = 100 %).

Adsorption of amlodipine on surface-modified activated carbon derived from Delonix regia seed pod

In this study, seed pods of Delonix regia was used to produce activated carbon (DRAC) whose efficiency as an adsorbent in removing amlodipine (AML) from aqueous solution was examined. Adsorbent’s characterization was carried out via Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Boehm titration (BT), and pH point of zero charge (pHpzc). Results obtained from FTIR showed notable peaks attributed to various functional groups present on the DRAC’s surface which must have contributed to the effective adsorptive removal of AML. Images obtained from the SEM analysis revealed that the surface of DRAC possesses various pore sites which enhances the uptake of AML to the adsorbent’s surface. Results obtained from the Boehm titration showed the total value of the acidic group on the surface of the DRAC to be 0.99 ± 0.02 and 0.28 ± 0.01 for the total basic group; this implies that the DRAC’s surface is predominantly acidic as further supported by the value obtained for the pHpzc which was 4.2 ± 0.2. At 303K, a maximum adsorption capacity of 56.5 ± 0.3 mg/g was obtained. It was observed that the Langmuir adsorption model best describes the adsorption data obtained and the data fitted the Pseudo-Second Order kinetics most. Analysis of adsorption thermodynamics showed that the sorption process was exothermic and physisorption defines the nature of the sorption mechanism (Ea< 40 kJmol−1). The cost analysis revealed that producing DRAC is 10 times cheaper as compared to buying commercially-available activated carbon. Hence, the adsorption of AML from aqueous solution using DRAC is efficient as well as cost-effective.

The effect of hierarchical pore structure SAPO-34 catalyst on the diffusion and reaction behavior in MTO reaction

Establishing the hierarchical pore structure is considered as a feasible approach for enhancing diffusion and improve catalytic efficiency of SAPO-34 zeolite in the methanol-to-olefin process. Nevertheless, under reaction conditions, the correlation among the diffusion behavior in the crystal, coke deposition behavior and catalytic performance of SAPO-34 catalysts with varying pore structures remains to be clarified. Herein, we revealed the structure–activity relationship between the hierarchical pore structure, the catalytic performance and the anti-coke deposition performance of the catalyst in the MTO reaction via the synergy of reaction–diffusion experiments and molecular simulation, then the mechanism of the hierarchical pore SAPO-34 catalyst to eliminate the diffusion limit and improve the accessibility of acid sites was clarified. The results demonstrated that the establishment of a hierarchical pore structure strengthened the diffusion of reactant methanol in the pores, leading to the diffusion resistance being reduced by 5 times and the diffusion coefficient being improved by two orders of magnitude. The key reaction rate-determining step shifted from micropores diffusion to the adsorption of acid sites in hierarchical pores, and the catalytic efficiency of the catalyst was increased by 3 times. Furthermore, with the establishing hierarchical pore technique, the expansion of the accommodation space for coke deposition led to a reduction in the blocking of pores due to coke deposition, particularly around the orifices. Moreover, the accessibility of the reactant molecules to the acid sites within the pores was enhanced, resulting in a balanced ratio between pore blockage and acid site coverage, thereby improving the anti-coke deposition performance of the SAPO-34 catalyst. This work can provide important foundational data and theoretical guidance for the study of reaction–diffusion synergistic interaction in zeolite catalysis reactions.

Highly efficient and selective removal of 90Sr by the carboxylated COFs (Tp-DTA) from radionuclides-contaminated groundwater

In this study, a carboxyl-functionalized covalent organic framework (COF) rich in nitrogen (N) and oxygen (O) functional groups was prepared and characterized, which provided a new opportunity for the efficient and rapid treatment of radioactive contamination in nuclear wastewater. The synthesis of the COF (Tp-DTA) was constructed using 1,3,5-triformylphloroglucinol (TFP) and 2,5-diaminoterephthalic acid (DTA), providing a large specific surface area, mesoporous pore, and abundant coordination sites with high adsorption capacity and exceptional affinity for Sr2+. Batch adsorption experiments exhibited that Tp-DTA achieved a maximum adsorption capacity of 145.4 mg/g for Sr2+ in alkaline solutions, reaching adsorption equilibrium within 60 min. Tp-DTA exhibited rapid kinetics for 90Sr, with the amounts of 90Sr removed more than 95% within 3 min. In the presence of coexisting ions (Na+, K+, Cs+, Mg2+, and Ca2+), Tp-DTA displayed excellent preferential selectivity for Sr2+ and high removal efficiency. Even in simulated groundwater containing multiple complex ions, Tp-DTA demonstrated a strong affinity for Sr2+ and showed practical applicability with a nearly 100% removal efficiency for 90Sr. XPS and FTIR characterizations confirmed that the adsorption mechanism of Sr2+ involved chelation exchange between the carboxyl groups of Tp-DTA and Sr2+ in the solution. Furthermore, the desorption efficiency of HCl (>0.01 mol/L) can reach 95% and five cyclic desorption-adsorption experiments demonstrated the reusability of Tp-DTA, endowing the carboxyl-functional COF with great potential in the treatment of 90Sr-contaminated radioactive wastewater and environmental remediation.

A Transient π-π or Cation-π Interaction between Degron and Degrader Dual Residues: A Key Step for the Substrate Recognition and Discrimination in the Processive Degradation of SulA by ClpYQ (HslUV) Protease in Escherichia coli.

The Escherichia coli ATP-dependent ClpYQ protease constitutes ClpY ATPase/unfoldase and ClpQ peptidase. The Tyr91st residue within the central pore-I site of ClpY-hexamer is important for unfolding and translocating substrates into the catalytic site of ClpQ. We have identified the degron site (GFIMRP147th) of SulA, a cell-division inhibitor recognized by ClpYQ and that the Phe143rd residue in degron site is necessary for SulA native folded structure. However, the functional association of this degron site with the ClpYQ degrader is unknown. Here, we investigated the molecular insights into substrate recognition and discrimination by the ClpYQ protease. We found that the point mutants ClpYY91FQ, ClpYY91HQ, and ClpYY91WQ, carrying a ring structure at the 91st residue of ClpY, efficiently degraded their natural substrates, evidenced by the suppressed bacterial methyl-methane-sulfonate (MMS) sensitivity, the reduced β-galactosidase activity of cpsB::lacZ, and the lowest amounts of MBP-SulA in both in vivo and in vitro degradation analyses. Alternatively, mimicking the wild-type SulA, SulAF143H, SulAF143K and SulAF143W, harboring a ring structure or a cation side-group in 143rd residue of SulA, were efficiently degraded by ClpYQ in the bacterial cells, also revealing shorter half-lives at 41 °C and higher binding affinities towards ClpY in pull-down assays. Finally, ClpYY91FQ and ClpYY91HQ, were capable of effectively degrading SulAF143H and SulAF143K, highlighting a correspondingly functional interaction between the SulA 143rd and ClpY 91st residues. According to the interchangeable substituted amino acids, our results uniquely indicate that a transient π-π or cation-π interaction between the SulA 143rd and ClpY 91st residues could be aptly gripped between the degron site of substrates and the pore site of proteases (degraders) for substrate recognition and discrimination of the processive degradation.

Adsorption mechanism of formaldehyde, ammonia and sulfur dioxide gases on inexpensive metal-doped ZnO surface: A DFT study

Here, the adsorption mechanisms and detection performance of three different hazardous gases, including formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2), on undoped ZnO and inexpensive metal-doped ZnO surfaces were studied by density functional theory (DFT). CH2O and NH3 are physically adsorbed on the zinc top site (t-site) and six-membered ring pore site (p-site) on the undoped ZnO surface, and the adsorption energies are -0.56 eV and -0.32 eV. The difference is that SO2 is weakly chemisorbed on bridge site (b-site) of ZnO surface with an adsorption energy of 1.78 eV. The adsorption energy of Al-doped ZnO for CH2O, NH3, and SO2 is higher than that of undoped ZnO, reaching -1.64 eV, -1.69 eV, and -3.62 eV respectively. The adsorption properties of Cu-doped ZnO for CH2O and SO2 are not significantly improved with exception of NH3. Collectively, the adsorption mechanism of undoped and doped ZnO or hazardous gases is elucidated, which provides theoretical guidance for the further utilization of ZnO substrate materials in the field of gas sensitivity.

Photothermal-driven Reforming of Methanol Solution into Hydrogen over Ultra-stable Cr-MOF-embedded CuInS2 Heterostructure

Photothermal-driven reforming of methanol solution to hydrogen (PTRM) is an attractive way for sustainable in-situ hydrogen (H2) supply by solar energy. But the effective activation of MeOH and H2O to improve H2 production kinetics at low temperatures faces really challenge. As the cleavage energy barrier of CH bond in methanol is much higher than that of OH bond dissociation, here, we propose the use of CuInS2 with high interfacial hydroxyl activation capacity to integrate with MIL-101(Cr) matrix via in-situ encapsulation strategy. The pore confinement and site isolation of Cr-MOF matrix (MIL-101(Cr)) keep the high dispersion of CuInS2 (4.20 nm) and prohibit its agglomeration in PTRM. With synergistically photothermal effect, the insertion of CuInS2 not only provides a high-speed channel for photoexcited charge migration through the interface between CuInS2 and MIL-101(Cr) but also enhances the dehydrogenation activity of MeOH and H2O effectively as an electron-enriched tank. Moreover, the excellent ability of CuInS2 to dissociate H2O molecules at low temperature promoted the formation of abundant interfacial OH, which reinforces the CH bond cleavage of MeOH to decline the apparent activation energy (26%) and boost the H2 evolution kinetics (36233.0 μmolgcat-1h−1). Encouragingly, CuInS2@MIL-101(Cr) with an exceptional total turnover number (TON) climbing up to 16,775 in 65 h of run without catalyst deactivation. This work provides an important insight for the rational design of ultra-stable photo-thermal catalysts toward solar-driven reforming of methanol solution to hydrogen and conducive to the high activity performance in hydrogen-powered polymer electrolyte membrane (PEMFC) fuel cell.

Effector-dependent structural transformation of a crystalline framework with allosteric effects on molecular recognition ability

Structurally flexible porous crystals that combine high regularity and stimuli responsiveness have received attracted attention in connection with natural allostery found in regulatory systems of activity and function in biological systems. Porous crystals with molecular recognition sites in the inner pores are particularly promising for achieving elaborate functional control, where the local binding of effectors triggers their distortion to propagate throughout the structure. Here we report that the structure of a porous molecular crystal can be allosterically controlled by local adsorption of effectors within low-symmetry nanochannels with multiple molecular recognition sites. The exchange of effectors at the allosteric site triggers diverse conversion of the framework structure in an effector-dependent manner. In conjunction with the structural conversion, it is also possible to switch the molecular affinity at different recognition sites. These results may provide a guideline for the development of supramolecular materials with flexible and highly-ordered three-dimensional structures for biological applications.

Synthesizing Nanoporous Stainless Steel Films via Vacuum Thermal Dealloying

Vacuum thermal dealloying is a recently developed technique and was newly introduced to produce nanoporous metals, due to its intriguing advantages, i.e., preventing oxidation and producing no chemical waste, etc. Here, we report on the fabrication of nanoporous stainless steel films by vacuum thermal dealloying of sputtered stainless steel–magnesium precursor films. It was found that crack-free nanoporous stainless steel films can be successfully attained under a broad temperature range of 450–600 °C, with a dealloying time of 0.5–2 h. The resulting structure and ligaments were temperature- and time-dependent, and moreover, the condition of “600 °C + 2 h” generated the most homogeneous structure. Moreover, small amounts of residual Mg were found at pore sites in the resultant structures, suggesting that the dealloying was not fully complete.

Real-time tracking of drug binding to influenza A M2 reveals a high energy barrier

The drug Rimantadine binds to two different sites in the M2 protein from influenza A, a peripheral site and a pore site that is the primary site of efficacy. It remained enigmatic that pore binding did not occur in certain detergent micelles, and in particular incomplete binding was observed in a mixture of lipids selected to match the viral membrane. Here we show that two effects are responsible, namely changes in the protein upon pore binding that prevented detergent solubilization, and slow binding kinetics in the lipid samples. Using 55–100 kHz magic-angle spinning NMR, we characterize kinetics of drug binding in three different lipid environments: DPhPC, DPhPC with cholesterol and viral mimetic membrane lipid bilayers. Slow pharmacological binding kinetics allowed the characterization of spectral changes associated with non-specific binding to the protein periphery in the kinetically trapped pore-apo state. Resonance assignments were determined from a set of proton-detected 3D spectra. Chemical shift changes associated with functional binding in the pore of M2 were tracked in real time in order to estimate the activation energy. The binding kinetics are affected by pH and the lipid environment and in particular cholesterol. We found that the imidazole-imidazole hydrogen bond at residue histidine 37 is a stable feature of the protein across several lipid compositions. Pore binding breaks the imidazole-imidazole hydrogen bond and limits solubilization in DHPC detergent.

Air-enclosed pores in graphene aerogel inhibit the adsorption of bisphenol A but accelerate the adsorption of naphthalene

Graphene hydrogel (GH) and aerogel (GA) have great application potential as highly effective adsorbents, but the accessibility of their adsorption sites have not yet been identified, restricting our understanding on the adsorption mechanisms and manufacturing. This study comparatively studied the adsorption characteristics of bisphenol A (BPA) and naphthalene (NAP) on GH and GA, focussing on the accessibility of the adsorption sites. The adsorption of BPA on GA was much lower but faster than that on GH. NAP adsorption on GA was very close to that on GH but faster than that on the latter. Considering that NAP is volatilisable, we speculate that some unwetted sites in the air-enclosed pores are available to it, but not to BPA. We applied ultrasonic and vacuum treatments to remove the air in GA pores, which was verified using a CO2 replacement experiment. BPA adsorption was greatly enhanced but slowed, while that of NAP was not enhanced. This phenomenon suggested that some inner pores became accessible in the aqueous phase after air removal from pores. The enhanced accessibility of air-enclosed pores was verified by the increased relaxation rate of surface-bounded water on GA, based on a 1H NMR relaxation analysis. This study highlights that the accessibility of adsorption site plays a crucial role for the adsorption properties of carbon-based aerogel. The volatile chemicals may be quickly adsorbed in the air-enclosed pores, which be useful for immobilizing volatile contaminants.

Combining hierarchical pores and unsaturated sites into Quasi-MIL-125(Ti) for ultra-fast and efficient adsorption of cationic dyes

Developing new adsorbents with hierarchical pore and unsaturated adsorption sites are highly demanded to achieve rapid adsorption rate and good adsorption selectivity in purifying organic wastewater. We here reported a new Quasi-MIL-125(Ti) synthesized at 340 °C under air atmosphere and considered as a high-efficiency adsorbent for capturing cationic dyes. The morphology of the material is characterized by XRD, SEM, TEM, etc. and the adsorption performance of Quasi-MIL-125(Ti) was systematically studied. Remarkably, it takes only 1 min to rapidly remove 20 mg L-1 MB or NR with 1 g L-1 Quasi-MIL-125(Ti), which is far superior to the previously reported materials. Adsorption isotherm shows that dyes adsorption on Quasi-MIL-125(Ti) follow a Langmuir adsorption isotherm model. The experimental maximum adsorption capacities were 109.3 mg g-1 for MB and 151.1 mg g-1 for NR, respectively. The hierarchical pores facilitate the diffusion and co-adsorption of different dye molecules. Adsorption mechanism reveals that the strong electrostatic attraction originated from the unsaturated Ti sites in Quasi-MIL-125(Ti) contributes to the ultra-fast adsorption behavior during cationic dyes chemisorption process. This study not only provides a promising prospect for the synthetic strategy of super-adsorbents, but also provides reference and theoretical guidance for practical dye wastewater treatment.