Spacer Length Research Articles

Thermal behaviors and DC conductivity of linker spacer influence on polymerized ionic liquids with bis-imidazolium embedding in the backbone chain

A series of polymerized ionic liquids (PILs) with bis-imidazolium embedding into the backbone was designed to study the effect of linker spacers (C-2, C-4, C-6, and C-8) on their ionic conductivity and thermal behaviors. All PILs were prepared by step-growth polymerization using a modified Menshutkin reaction, where 1,1′-(1,4-butadiyl) bisimidazole (Bbim), was structurally modified by a series of bis-bromoacetates (1,1-(1,n-alkanediyl) bis(bromoacetate) (n = 2, 4, 6, and 8 correspond to 1,2-EBA, 1,4-BBA, 1,6-HBA, and 1,8-OBA, respectively). Interestingly, the density function theory (DFT)-derived complexation energy exhibits a correlation with spacer length, decreasing as the linker spacer increases. Moreover, shorter linker chains notably elevate the glass transition temperature (Tg). The room temperature dc-conductivity of C-8 is the highest (2.2 × 10–5 S/cm) among PILs with shorter linker chain lengths. These results indicate that PILs 1–4 have the potential to yield substantial ionic conductivity in a chain of flexible segments (low Tg), while exhibiting a decrease in complexation energy.

Synthesis and Enzymatic Evaluation of a Small Library of Substituted Phenylsulfonamido-Alkyl Sulfamates towards Carbonic Anhydrase II.

A small library of 79 substituted phenylsulfonamidoalkyl sulfamates, 1b-79b, was synthesized starting from arylsulfonyl chlorides and amino alcohols with different numbers of methylene groups between the hydroxyl and amino moieties yielding intermediates 1a-79a, followed by the reaction of the latter with sulfamoyl chloride. All compounds were screened for their inhibitory activity on bovine carbonic anhydrase II. Compounds 1a-79a showed no inhibition of the enzyme, in contrast to sulfamates 1b-79b. Thus, the inhibitory potential of compounds 1b-79b towards this enzyme depends on the substituent and the substitution pattern of the phenyl group as well as the length of the spacer. Bulkier substituents in the para position proved to be better for inhibiting CAII than compounds with the same substituent in the meta or ortho position. For many substitution patterns, compounds with shorter spacer lengths were superior to those with long chain spacers. Compounds with shorter spacer lengths performed better than those with longer chain spacers for a variety of substitution patterns. The most active compound held inhibition constant as low as Ki = 0.67 μM (for 49b) and a tert-butyl substituent in para position and acted as a competitive inhibitor of the enzyme.

Exploring interfacial properties and thermodynamic parameters of synthesized biodegradable surfactants from Brassica Juncea and their emulsification characteristics

This study investigates the synthesis and characterization of four non-ionic surfactants of different spacer lengths derived from Brassica Juncea (mustard oil) and explore their potential applications. The chemical structures of the surfactants were confirmed by FTIR, 1HNMR spectroscopy and GC. Surface tension values of the surfactants were measured at various temperatures, unveiling temperature-dependent behaviour and associated thermodynamics. The critical micelle concentrations (CMC) of different surfactants were found to be very low (0.064–0.096 mmol/l at 303 K) compared to conventional surfactants. The CMC and the surface tension further decrease significantly with an increase in temperature. Surface-active thermodynamic parameters of the surfactants demonstrate their lower interfacial characteristics and enhanced self-aggregation capability. At CMC, the synthesized surfactants effectively decrease the interfacial tension (IFT) between water and dodecane to a notably low range of 9.5 to 12.1 mN/m, which is further reduced to a range of 3.2 to 6.1 mN/m at optimal salinity. The surfactants also show good emulsification properties, the emulsions formed in the water-dodecane system using the gemini surfactants as emulsifiers were extensively characterized, encompassing phase behaviour and droplet size distribution analysis. These emulsions exhibit favourable viscous properties, with viscosities ranging from 5 to 20 mPa.s at a 5 s-1 shear rate. This study establishes that the synthesized Gemini surfactants are viable candidates for Enhanced Oil Recovery (EOR), showcasing robust stability, interfacial activity, and favourable rheological properties, alongside biodegradability.

Effects of Carbon Spacer Length on Conformational Transitions and Protein Adsorption of Polyzwitterions.

The properties of polyzwitterions are closely linked to their carbon spacer length (CSL) between oppositely charged groups. A thorough understanding of the effect of CSL on the properties of polyzwitterion-functionalized membranes is important for their fouling resistance and separation performances. In this work, polyzwitterion-functionalized membranes with different CSLs are prepared by coupling selective swelling-induced pore generation with zwitterionization, and the investigation is focused on comprehending the molecular mechanisms underlying protein resistance and conformational transitions within polyzwitterions under varying CSLs. The zwitterionized films show an enhancement in the surface negative potential with the increase of CSL, attributed to the negatively charged groups distanced from the positively charged groups. Quartz crystal microbalance with dissipation (QCM-D) demonstrates that zwitterionized films with different CSLs display distinct levels of resistance to protein adsorption. The trimethylamine N-oxide-derived polymer (PTMAO, CSL = 0) zwitterionized film shows the highest resistance compared to the poly(3-[dimethyl(2'-methacryloyloxyethyl] ammonio) ethanesulfonate (PMAES, CSL = 2) zwitterionized film and the poly(sulfobetaine methacrylate) (PSBMA, CSL = 3) zwitterionized film, owing to its electrical neutrality and pronounced hydrophilicity. Moreover, analysis of the anti-polyelectrolyte behaviors reveals that PTMAO does not undergo a significant conformation transition in deionized water and salt solutions, while the conformations of PMAES and PSBMA display to be more salt-dependent as the CSL increases, attributed to their increased polarization and dipole moment. As a result, the permeability of zwitterionized membranes exhibits enhanced salt responsiveness with the increase in CSL. The findings of this study are expected to facilitate the design of adsorption-resistant surfaces desired in diverse fields.

Lymph node targeting of cyclosporine ameliorates ocular manifestations in a mouse model of systemic lupus erythematosus (SLE) via PD-L1

One-third of systemic lupus erythematosus (SLE) patients experience various degrees of ocular manifestations, with immunosuppressants recommended as a treatment option. Targeted immune suppression via oral administration is challenging due to the harsh gastrointestinal tract environment combined with complex physiological barriers. Here, we report the efficacy of orally administered cyclosporine (CsA)-laden polymer nanoparticles decorated with the ligand – Gambogic Acid (P2Ns-GA-CsA) in sustained lymph node delivery. This is the first report demonstrating the CD71 specificity of P2Ns-GA-CsA in the CD71 knockout mouse model and the influence of spacer length in achieving target tissue bioavailability in a lupus mouse model. P2Ns-GA-CsA effectively regulates T-cell chemotaxis by PD-L1 at a 50 % lower dose compared to conventional CsA in a mouse model exhibiting lupus-associated corneal inflammation. Collectively, these results suggest the possibility for further development of P2Ns-GA to target a diverse range of lymphatic disorders.

Artificially designed synthetic promoter for a high level of salt induction using a cis-engineering approach

This work aimed to design a synthetic salt-inducible promoter using a cis-engineering approach. The designed promoter (PS) comprises a minimal promoter sequence for basal-level expression and upstream cis-regulatory elements (CREs) from promoters of salinity-stress-induced genes. The copy number, spacer lengths, and locations of CREs were manually determined based on their occurrence within native promoters. The initial activity profile of the synthesized PS promoter in transiently transformed N. tabacum leaves shows a seven-fold, five-fold, and four-fold increase in reporter GUS activity under salt, drought, and abscisic acid stress, respectively, at the 24-h interval, compared to the constitutive CaMV35S promoter. Analysis of gus expression in stable Arabidopsis transformants showed that the PS promoter induces over a two-fold increase in expression under drought or abscisic acid stress and a five-fold increase under salt stress at 24- and 48-h intervals, compared to the CaMV35S promoter. The promoter PS exhibits higher and more sustained activity under salt, drought, and abscisic acid stress compared to the constitutive CaMV35S.

Lytic transglycosylase Slt of Pseudomonas aeruginosa as a periplasmic hub protein.

Peptidoglycan is a major constituent of the bacterial cell wall. Its integrity as a polymeric edifice is critical for bacterial survival and, as such, it is a preeminent target for antibiotics. The peptidoglycan is a dynamic crosslinked polymer that undergoes constant biosynthesis and turnover. The soluble lytic transglycosylase (Slt) of Pseudomonas aeruginosa is a periplasmic enzyme involved in this dynamic turnover. Using amber-codon-suppression methodology in live bacteria, we incorporated a fluorescent chromophore into the structure of Slt. Fluorescent microscopy shows that Slt populates the length of the periplasmic space and concentrates at the sites of septation in daughter cells. This concentration persists after separation of the cells. Amber-codon-suppression methodology was also used to incorporate a photoaffinity amino acid for the capture of partner proteins. Mass-spectrometry-based proteomics identified 12 partners for Slt in vivo. These proteomics experiments were complemented with in vitro pulldown analyses. Twenty additional partners were identified. We cloned the genes and purified to homogeneity 22 identified partners. Biophysical characterization confirmed all as bona fide Slt binders. The identities of the protein partners of Slt span disparate periplasmic protein families, inclusive of several proteins known to be present in the divisome. Notable periplasmic partners (KD < 0.5 μM) include PBPs (PBP1a, KD = 0.07 μM; PBP5 = 0.4 μM); other lytic transglycosylases (SltB2, KD = 0.09 μM; RlpA, KD = 0.4 μM); a type VI secretion system effector (Tse5, KD = 0.3 μM); and a regulatory protease for alginate biosynthesis (AlgO, KD < 0.4 μM). In light of the functional breadth of its interactome, Slt is conceptualized as a hub protein within the periplasm.

New half-sandwich ruthenium(II) complexes of chelating (SS) organochalcogen ligands and their application as transfer hydrogenation catalysts

Room temperature reactions of [(η6-arene)Ru(μ-Cl)Cl]2 (arene = p-cymene) with three new bidentate (SS) organochalcogen ligands, 2a–c (2a: 1,1’-ethylenebis(3-ethyl-imidazole-2-thione), 2b: 1,1’-ethylenebis(3-propyl-imidazole-2-thione), 2c: 1,1’-methylenebis(3-ethyl-imidazole-2-thione)), and in situ anionic exchange with KPF6 afforded the corresponding new 18-electron half-sandwich [(η6-arene)RuLCl]PF6 complexes 3a–c (3a: L = 2a, 3b: L = 2b, 3c: L = 2c). The Ru(II) complexes and the organochalcogen ligands were fully characterized by spectroscopic and analytical techniques. Solid state single crystal X-ray diffraction analysis of 3a–c displayed the Ru(II) center in the expected piano stool geometry. The catalytic activities of the half-sandwich ruthenium complexes toward the transfer hydrogenation of ketones to their corresponding alcohols were investigated using 2-propanol as a hydrogen source and solvent. All three Ru(II) complexes exhibited excellent catalytic activity for the transfer hydrogenation of ketones in the order 3b > 3a > 3c at an appreciably low catalyst loading of 0.5 mol% under a minimal alkaline condition of 10 mol% KOH. The catalytic activities of the complexes are influenced by the length of the alkyl spacer and the steric bulk of the N-substituents on the chelating organochalcogen ligand framework.

Virtual screening of cucurbituril host-guest complexes: Large-scale benchmark of end-point protocols under MM and QM Hamiltonians

The similarity of protein–ligand and host–guest complexes leads to the direct extension of end-point free energy techniques to virtual screening of the latter. Despite the massive application of end-point calculations in modelling and predictions of host–guest binding, it still lacks a large-scale benchmark test with sufficient sizes, sampling length and diverse coverages of chemical spaces to get rid of many disturbing factors and provide an unbiased statistical perspective of practical performance and value of end-point screening. Cucurbiturils as one of the main-stream macrocycles are quite popular in pharmaceutical research and industrial applications as drug reservoirs and carriers. In this work, we gather a large dataset of ∼150 host–guest complexes involving cucurbiturils with varying numbers of repeating units, extensively sample the conformational space in physical end states with both the single- and three-trajectory protocols, and extract the affinity estimates with a variety of MM and QM/GBSA Hamiltonians with implicit solvents. The diversity of chemical compositions, the quality of configurational sampling, and the comprehensiveness of parameter combinations are unprecedently high, enabling us to deduce conclusive pictures of the end-point performance in host–guest binding. Unlike previous reports on improved performance due to the incorporation of the QM treatment, shifting to QM/GBSA treatments deteriorates both the reproduction of absolute affinities and the prediction of affinity ranks in our large-scale end-point benchmark, regardless of the employed sampling protocol (i.e., single- and three-trajectory realization). Overall, in the end-point screening of cucurbituril host–guest complexes, we recommend sticking to the original MM/GBSA Hamiltonians in both sampling and free energy estimation. The best/recommended selection with high accuracy and robustness among all end-point protocols benchmarked in this work is the three-trajectory GAFF + GBOBC-I regime, which achieves top performances for both the reproduction of absolute affinities and ranking different host–guest pairs. Docking estimates with seven main-stream protocols have been observed as a promising tool for host–guest binding, but their ranking powers in the current large host–guest dataset does not surpass end-point tools, validating the value of post-docking end-point screening.

Understanding the Role of Ligand Structure on Extraction of Neptunium by N-Pivot Tripodal Diglycolamides in an Ionic Liquid

ABSTRACT The extraction of Np4+ was studied by a series of N-pivot tripodal diglycolamides, with varying substituents (alkyl groups with varying branching and chain length) and varying spacer length, dissolved in an ionic liquid, i.e. [C4mim][Tf2N]. Out of a series of four ligands, L I (propylene spacer) and L II (ethylene spacer) differ only in the spacer length connecting the three diglycolamide units with the tripodal N platform. While L II – L IV have the same spacer length (ethylene spacer), but L II has a hydrogen atom, L III has methyl group, and L IV has isopropyl group as a substituent at the amidic N atom close to the central N atom. A reversal extraction mechanism of Np4+ was observed when the spacer chain length reduced from a propylene group in L I to an ethylene group in L II – L IV . While a cation-exchange mechanism was observed in case of L I , a solvation extraction mechanism was seen for the other three ligands with the extracted species being Np(NO3)2(L)2+ for L I , and [Np(NO3)4·L] for L II – L IV . The extraction efficiencies of Np4+ with L II – L IV were significantly affected by the nature of the alkyl substituents and follow the order: L II > L III > L IV . This trend in the extraction pattern affirms that the alkyl substitution at the amidic N atom creates steric strain in the ligand while complexing with the metal ion.

Comprehensive analysis of the editing window of C-to-T TALE base editors

One of the most recent advances in the genome editing field has been the addition of “TALE Base Editors”, an innovative platform for cell therapy that relies on the deamination of cytidines within double strand DNA, leading to the formation of an uracil (U) intermediate. These molecular tools are fusions of transcription activator-like effector domains (TALE) for specific DNA sequence binding, split-DddA deaminase halves that will, upon catalytic domain reconstitution, initiate the conversion of a cytosine (C) to a thymine (T), and an uracil glycosylase inhibitor (UGI). We developed a high throughput screening strategy capable to probe key editing parameters in a precisely defined genomic context in cellulo, excluding or minimizing biases arising from different microenvironmental and/or epigenetic contexts. Here we aimed to further explore how target composition and TALEB architecture will impact the editing outcomes. We demonstrated how the nature of the linker between TALE array and split DddAtox head allows us to fine tune the editing window, also controlling possible bystander activity. Furthermore, we showed that both the TALEB architecture and spacer length separating the two TALE DNA binding regions impact the target TC editing dependence by the surrounding bases, leading to more restrictive or permissive editing profiles.

Extension of unbounded uniformly continuous functions and pseudometrics

In this paper we aim to characterize uniformly continuous real functions and pseudometrics on metric spaces, having uniformly continuous extension. For functions we use a very similar approach as McShane in [7] using moduli of continuity. By doing that we obtain an explicit formula for the extension. We also show that our characterization for functions is equivalent to one proposed in [8] for uniform spaces. We then show that a similar approach can be done for uniformly continuous pseudometrics.To do so we use the notion of chainable metric spaces and intrinsic metrics defined in [9]. A somewhat similar approach has been studied in [6] for normed linear spaces.

Hot-carrier thermophotovoltaic systems

A thermophotovoltaic (TPV) energy converter harnesses thermal photons emitted by a hot body and converts them to electricity. When the radiative heat exchange between the emitter and photovoltaic cell is spectrally monochromatic, the TPV system can approach the Carnot thermodynamic efficiency limit. Nonetheless, this occurs at the expense of vanishing extracted electrical power density. Conversely, a spectrally broadband radiative heat exchange between the emitter and the cell yields maximal TPV power density at the expense of low efficiency. By leveraging hot-carriers as a means to mitigate thermalization losses within the cell, we demonstrate that one can alleviate this trade-off between power density and efficiency. Via detailed balance analysis, we show analytically that one can reach near-Carnot conversion efficiencies close to the maximum power point, which is unattainable with conventional TPV systems. We derive analytical relations between intrinsic device parameters and performance metrics, which serve as design rules for hot-carrier-based TPV systems.

Singularity distance computations for 3-RPR manipulators using intrinsic metrics

Avoiding singularities is a crucial task in robotics and path planning. This paper proposes a novel algorithm for detecting the closest singularity to a given pose for nine interpretations of the 3-RPR manipulator. The algorithm utilizes intrinsic metrics based on the framework's total elastic strain energy density, employing the physical concept of Green-Lagrange strain. The constrained optimization problem for detecting the closest singular configuration with respect to these metrics is solved globally using tools from numerical algebraic geometry implemented in the software package Bertini. The effectiveness of the proposed algorithm is demonstrated on a 3-RPR manipulator executing a one-parametric motion. Additionally, the obtained intrinsic singularity distances are compared with extrinsic metrics. Finally, the paper illustrates the advantage of employing a well-defined metric for identifying the closest singularities in comparison with the existing methods in the literature, highlighting its application in design optimization.

Investigation of glass transition and polymorphism of smectogenic, partially fluorinated chiral compound by X-ray diffraction and infra-red spectroscopy

The X-ray diffraction and infra-red spectroscopy measurements are performed as a function of temperature upon heating of the glassy smectic CA* phase of liquid crystalline (S)-4′-(1-methylheptylcarbonyl)biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy)heptyl-1-oxy]-3-fluorobenzoate (3F7FPhH6) for the search of relationship between the structural changes and intra-molecular vibrations. The smectic layer spacing and correlation length, determined from the X-ray diffraction patterns, show different temperature dependences in the glassy state and above the glass transition temperature. The vibrational spectra do not show distinct changes upon the glass transition. Density-functional theory calculations for an isolated molecule in two conformations are applied for assignment of the IR absorption bands. The positive correlation between the average intermolecular distances and positions of two absorption bands, originating from the C=O stretching, is noticed and interpreted as a decreasing amount of the weak C-H…O=C hydrogen bonds upon heating in the smectic CA*, smectic A*, and isotropic liquid phases. The results are compared with the previously reported X-ray diffraction and infra-red data for the isostructural (S)-4′-(1-methylheptylcarbonyl)biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy)heptyl-1-oxy]-2-fluorobenzoate (3F7HPhF6).

Correction of linear fracture density and error analysis using underground borehole data

Fracture data acquired from drill core and borehole image logs require corrections for the bias due to fracture orientation, that are usually achieved by the Terzaghi correction technique. Previous studies often approximate the wellbore as a one-dimensional scanline, assuming that the length of the core axis within the sampling range is equal to the scanline length. This study refers to the commonly used workflow as the original Terzaghi correction method which is known to perform poorly when the angle (θ) between the core axis and the fracture is small. To address this issue, we propose an extension of the Terzaghi correction method that also considers the core diameter and is a function of both the fractures and the host layer dipping angle. The new method resolves the fracture density problem by selecting a new direction for the scanline perpendicular to the fracture and calculating the projection length of the sampling space in this direction. The fracture spatial arrangements and observed number of sampled fractures mainly affect the performance of this new approach. However, possible errors in the new correction method pertaining to the equidistant fracture density should decrease with increasing number of sampled fractures. It is found that an acceptable correction range exists for equidistant fracture density, though, when the corrected density is not within the acceptable correction range, the observed sampled fractures will not be equal to the true observed value. This means the corrected fracture density would be in an unacceptable range of errors. Moreover, the new method can provide results within the acceptable range when the angle between the fracture and the core axis is less than 20°. At the same time, this new method is free from other disadvantages in the original Terzaghi correction method, particularly, when the ratio of layers’ thickness to the core diameter is low. Therefore, the improved approach presented here is especially applicable to thin layers (no more than two times the core diameter) and conditions where the angle between the fracture and the core axis is less than 20°, which can contribute to fracture density characterization in the subsurface.

Recurrent and (strongly) resolvable graphs

We develop a new approach to recurrence and the existence of non-constant harmonic functions on infinite weighted graphs. The approach is based on the capacity of subsets of metric boundaries with respect to intrinsic metrics. The main tool is a connection between polar sets in such boundaries and null sets of paths. This connection relies on suitably diverging functions of finite energy.

The effect of polymer with tunable alkyl spacers on the microstructure of amphoteric membrane for vanadium redox flow battery (VRB)

Amphoteric membranes, as promising candidates for VRBs, have attracted more attention. The side-chain-type polymers go far towards improving ion exchange capacity and further enhancing ion conductivity. A kind of Amphoteric ion exchange membranes (AIEMs) with different alkyl chain lengths (C2, C6, and C12 spacers) were synthesized by using ring-opening metathesis polymerization (ROMP). In addition, the interactions between N-containing groups with positively charged and -SO3- groups prevent swelling and vanadium crossover. The microphase separation structure through side chain induction was regulated, to respond to the ionic mobility of the membrane. The effect of the spacer lengths on the ion selectivity of AIEMs is investigated. In addition, the size and matrix of the constructed ion channel were calculated by using coarse-grained molecular dynamics (CGMD) simulation, which further verified the experiment.

Implicit particle-in-cell development for ion source plasmas

Particle-in-Cell (PIC) codes used to study plasma dynamics within ion sources typically use an explicit scheme. These methods can be slow when simulating regions of high electron density in ion sources, which require resolving the Debye length in space and the plasma frequency in time. Recent developments on fully-implicit PIC models in curvilinear geometries have shown that these spatial/time scales can be significantly decreased/increased respectively, allowing for notable speed-ups in simulation time, and thus making it a potential tool for studying the physics of ion sources. For this purpose, a charge and energy conserving implicit PIC code has been developed in 1D to determine its potential for simulating bounded plasmas. In this paper, we use this model to simulate a 1D benchmark of a bounded plasma with fixed plasma density and electron/ion temperatures. The results are shown to compare well to the benchmark and to the results using an explicit PIC code. It is shown that the total amount of macro-particles used in the simulation is a better figure of merit for accurate results than the standard particles per cell used in literature. Significant speed-ups in computation time can be achieved for high plasma densities if the accuracy requirements are relaxed. In this case, we demonstrate the ability of the implicit PIC code to speed-up simulation time by nearly a factor of 12 compared to explicit PIC.

A new method of oil and water well completion involving the implosion effect

Features of colmatation zones of a productive formation in terms of rotary drilling by drilling muds are considered. A brief analysis of the most popular decolmatation methods is performed. Special attention is paid to the decolmatation method involving implosion effect. An example of one of the existing installations is represented with following consideration of its application features. A new principally different installation, free from the disadvantages found in the available one, is considered; a patent for the installation is obtained in Kazakhstan. It does not involve tubing with its packer and wellhead sealing. It also does not require a compressor and its manifold. Characteristic features of the newly developed installation for creating implosion effect are represented; its operation at producing both single and any number of repeated implosion acts is examined. A mathematical analysis is performed to calculate the empty space limits required for the implosion effect by a criterion to prevent casing string collapse by hydrostatic pressure of the drilling mud remained in the annular space. An example of dependency of the maximum permitted length of empty space in the casing string on its mechanical strength and its wall thickness, calculated by means of a computer program, is represented.