A new quantitative structure-retention relationship model for predicting chromatographic retention time of oligonucleotides

An integrated approach is proposed to predict the chromatographic retention time of oligonucleotides based on quantitative structure-retention relationships(QSRR) models.First,the primary base sequences of oligonucleotides are translated into vectors based on scores of generalized base properties(SGBP),involving physicochemical,quantum chemical,topological,spatial structural properties,etc.;thereafter,the sequence data are transformed into a uniform matrix by auto cross covariance(ACC).ACC accounts for the ...     

Aqueous Batteries Operated at −50 °C

Insufficient ionic conductivity and freezing of the electrolyte are considered the main problems for electrochemical energy storage at low temperatures (low T). Here, an electrolyte with a freezing point lower than ?130 °C is developed by using dimethyl sulfoxide (DMSO) as an additive with molar fraction of 0.3 to an aqueous solution of 2 m NaClO₄ (2M‐0.3 electrolyte). The 2M‐0.3 electrolyte exhibits sufficient ionic conductivity of 0.11 mS cm^?1 at ?50 °C. The combination of spectroscopic investigations and molecular dynamics (MD) simulations reveal that hydrogen bonds are stably formed between DMSO and water molecules, facilitating the operation of the electrolyte at ultra‐low T. Using DMSO as the electrolyte additive, the aqueous rechargeable alkali‐ion batteries (AABs) can work well even at ?50 °C. This work provides a simple and effective strategy to develop low T AABs.     

Late‐Stage Peptide Diversification by Bioorthogonal Catalytic CH Arylation at 23 °C in H2O

The step‐economical late‐stage diversification of tryptophan‐containing peptides was accomplished through chemo‐ and site‐selective palladium‐catalyzed C?H arylation under exceedingly mild reaction conditions. Thus, the C?H functionalization occurred efficiently at 23 °C with a catalyst loading as low as 0.5 mol %, and/or in H₂O.     

A Decatwistacene with an Overall 170° Torsion

Two different lengths of twistacenes, namely hexatwistacene and decatwistacene, induced by steric hindrance between imide groups and neighboring annulated benzene rings, were synthesized by bottom‐up synthesis of palladium‐catalyzed Suzuki cross‐coupling and C−H activation. Single‐crystal X‐ray analyses revealed that decatwistacene, which is the longest twistacene reported, exhibits an astonishing overall end‐to‐end torsion angle of about 170°, the largest torsion angle reported. Both twistacenes have an enhanced solubility and stability with respect to light and oxygen owing to their large twisting deformations together with much lower LUMO levels caused by the introduction of imide groups, opening a window to the narrowest chiral graphene nanoribbons with good stability and processability.     

Effect of acidification treatment and morphological stability of sulfonated poly(arylene ether sulfone) copolymer proton‐exchange membranes for fuel‐cell use above 100 °C

Directly copolymerized wholly aromatic sulfonated poly(arylene ether sulfone) copolymers derived from 4,4′‐biphenol, 4,4′‐dichlorodiphenyl sulfone, 3,3′‐disulfonated, and 4,4′‐dichlorodiphenyl sulfone (BPSH) were evaluated as proton‐exchange membranes for elevated temperature operation (100–140 °C). Acidification of the copolymer from the sulfonated form after the nucleophilic step (condensation) copolymerization involved either immersing the solvent‐cast membrane in sulfuric acid at 30 °C for 24 h and washing with water at 30 °C for 24 h (method 1) or immersion in sulfuric acid at 100 °C for 2 h followed by similar water treatment at 100 °C for 2 h (method 2). The fully hydrated BPSH membranes treated by method 2 exhibited higher proton conductivity, greater water absorption, and less temperature dependence on proton conductivity as compared with the membranes acidified at 30 °C. In contrast, the conductivity and water absorption of a control perfluorosulfonic acid copolymer (Nafion 1135) were invariant with treatment temperature; however, the conductivity of the Nafion membranes at elevated temperature was strongly dependent on heating rate or temperature. Tapping‐mode atomic force microscope results demonstrated that all of the membranes exposed to high‐temperature conditions underwent an irreversible change of the ionic domain microstructure, the extent of which depended on the concentration of sulfonic acid sites in the BPSH system. The effect of aging membranes based on BPSH and Nafion at elevated temperature on proton conductivity is also discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2816–2828, 2003     

Über die Phasenbreite von V2O5 im Temperaturbereich von 450°C bis 620°C

About the Homogeneity Range of V₂O₅ in the Temperature Range of 450°C to 620°C The influence of the deposition temperature T₁ on the homogeneity range of V₂O₅-crystalls was investigated by using a solid electrolyte cell. The deviation x in V₂O_5–x from the stoichiometric composition was obtained with: x = 0.0066 at T₁ = 450°C up to x = 0.0326 at T₁ = 620°C.     

Retention behavior of resorcinarene‐based cavitands on C8 and C18 stationary phases

The understanding of the retention behavior of large molecules is an area of interest in liquid chromatography. Resorcinarene‐based cavitands are cavity‐shaped cyclic oligomers that can create host–guest interactions. We have investigated the chromatographic behavior of two types of cyclic tetramers as analytes in high‐performance liquid chromatography. The experiments were performed at four different temperatures (15, 25, 35, 45°C) on two types of reversed stationary phases (C₈ and C₁₈) from two different manufacturers. We have found a huge difference between the retention of resorcinarenes and cavitands. In some cases, the retention factor of cavitands was even a hundred times larger than the retention factor of resorcinarenes. The retention of methylated derivates was two to four times larger compared to that of demethylated compounds on every column. The opposite retention behavior of the resorcinarenes and cavitands on the two types of stationary phases showed well the difference of the selectivity of the XTerra and BDS Hypersil columns. The retention mechanism was studied by the thermodynamic parameters calculated from the van't Hoff equation.     

Crystallographic data for KNO2III at −35 °C and KNO2VII at −100°C

KNO₂ III below ?13°C is monoclinic, space group P2₁ or P2₁/m, with a₀, b₀, c₀ = 4.677, 9.650, 6.395 Å, β = 93.8° at ?35°C. There is a further phase transformation between ?35°C and ?100°C to a new phase KNO₂ VII, which is also monoclinic, space group P2₁ or P2₁/m: with a₀, b₀, c₀ = 8.397, 4.773, 7.644 Å, β = 112° at ?100°C. Both these phases appear to be ordered.     

Cycling a Lithium Metal Anode at 90 °C in a Liquid Electrolyte

Stable operation at elevated temperature is necessary for lithium metal anode. However, Li metal anode generally has poor performance and safety concerns at high temperature (>55 °C) owing to the thermal instability of the electrolyte and solid electrolyte interphase in a routine liquid electrolyte. Herein a Li metal anode working at an elevated temperature (90 °C) is demonstrated in a thermotolerant electrolyte. In a Li|LiFePO₄ battery working at 90 °C, the anode undergoes 100 cycles compared with 10 cycles in a practical carbonate electrolyte. During the formation of the solid electrolyte interphase, independent and incomplete decomposition of Li salts and solvents aggravate. Some unstable intermediates emerge at 90 °C, degenerating the uniformity of Li deposition. This work not only demonstrates a working Li metal anode at 90 °C, but also provides fundamental understanding of solid electrolyte interphase and Li deposition at elevated temperature for rechargeable batteries.     

Retention of nucleic acids in ion‐pair reversed‐phase high‐performance liquid chromatography depends not only on base composition but also on base sequence

The study on nucleic acid retention in ion‐pair reversed‐phase high‐performance liquid chromatography mainly focuses on size‐dependence, however, other factors influencing retention behaviors have not been comprehensively clarified up to date. In this present work, the retention behaviors of oligonucleotides and double‐stranded DNAs were investigated on silica‐based C₁₈ stationary phase by ion‐pair reversed‐phase high‐performance liquid chromatography. It is found that the retention of oligonucleotides was influenced by base composition and base sequence as well as size, and oligonucleotides prone to self‐dimerization have weaker retention than those not prone to self‐dimerization but with the same base composition. However, homo‐oligonucleotides are suitable for the size‐dependent separation as a special case of oligonucleotides. For double‐stranded DNAs, the retention is also influenced by base composition and base sequence, as well as size. This may be attributed to the interaction of exposed bases in major or minor grooves with the hydrophobic alky chains of stationary phase. In addition, no specific influence of guanine and cytosine content was confirmed on retention of double‐stranded DNAs. Notably, the space effect resulted from the stereostructure of nucleic acids also influences the retention behavior in ion‐pair reversed‐phase high‐performance liquid chromatography.     

Mechanical deformations of a liquid crystal elastomer at director angles between 0° and 90°: Deducing an empirical model encompassing anisotropic nonlinearity

Despite the wealth of studies reporting mechanical properties of liquid crystal elastomers (LCEs), no theory can currently describe their complete mechanical anisotropy and nonlinearity. Here, we present the first comprehensive study of mechanical anisotropy in an all‐acrylate LCE via tensile tests that simultaneously track liquid crystal (LC) director rotation. We then use an empirical approach to gain a deeper insight into the LCE's mechanical responses at values of strain, up to 1.5, for initial director orientations between 0° and 90°. Using a method analogous to time–temperature superposition, we create master curves for the LCE's mechanical response and use these to deduce a model that accurately predicts the load curve of the LCE for stresses applied at angles between 15° and 70° relative to the initial LC director. This LCE has been shown to exhibit auxetic behavior for deformations perpendicular to the director. Interestingly, our empirical model predicts that the LCE will further demonstrate auxetic behavior when stressed at angles between 54° and 90° to the director. Our approach could be extended to any LCE; so it represents a significant step forward toward models that would aid the further development of LCE theory and the design and modeling of LCE‐based technologies. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1367–1377     

The Comparability of Pt to Pt‐Ru in Catalyzing the Hydrogen Oxidation Reaction for Alkaline Polymer Electrolyte Fuel Cells Operated at 80 °C

The Pt‐catalyzed hydrogen oxidation reaction (HOR) for alkaline polymer electrolyte fuel cells (APEFCs) has been one of the focus subjects in current fuel‐cell research. The Pt catalyst is inferior for HOR in alkaline solutions, and alloying with Ru is an effective promotion strategy. APEFCs with Pt‐Ru anodes have provided a performance benchmark over 1 W cm^?2 at 60 °C. The Pt anode is now found to be in fact as good as the Pt‐Ru anode for APEFCs operated at elevated conditions. At 80 °C with appropriate gas back‐pressure, the cell with a Pt anode exhibits a peak power density of about 1.9 W cm^?2, which is very close to that with a Pt‐Ru anode. Even by decreasing the anode Pt loading to 0.1 mg cm^?2, over 1.5 W cm^?2 can still be achieved at 80 °C. This finding alters the previous understanding about the Pt catalyzed HOR in alkaline media and casts a new light on the development of practical and high‐power APFEC technology.     

Analysis of oxidation behavior under dry air of neat and Ta‐alloyed furan‐resin‐derived carbons heat treated at 3000 °C

Oxidation behavior and structural changes of furan‐resin‐derived carbons heat treated at 3000 °C were investigated at 500 and 700 °C under dry air. Thermogravimetric analysis (TGA), Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS) were employed to detect and understand this behavior and the changes. Effect of tantalum on antioxidation property of Ta‐alloyed carbon was also analyzed. The neat and Ta‐alloyed carbons had insignificant weight losses even after being kept at 500 °C for 12 h, while the Ta‐alloyed carbon had weight loss lower than that of the neat carbon after being kept at 700 °C for 6 h. It has been found by XPS that oxidation involves oxygen in internal area as well as on external surface of the carbons. It was also inferred that the carbon stored with oxygen in deeper internal area was easily oxidized. Ta alloying leads to change of the state of the Fermi energy on the specimens, which may cause the antioxidation property. Copyright © 2005 John Wiley & Sons, Ltd.     

Ultrafast SET‐LRP of methyl acrylate at 25 °C in alcohols

Alcohols are known to promote the disproportionation of Cu(I)X species into nascent Cu(0) and Cu(II)X. Therefore, alcohols are expected to be excellent solvents that facilitate the single‐electron transfer mediated living radical polymerization (SET‐LRP) mediated by nascent Cu(0) species. This publication demonstrates the ultrafast SET‐LRP of methyl acrylate initiated with bis(2‐bromopropionyloxy)ethane and catalyzed by Cu(0)/Me₆‐TREN in methanol, ethanol, 1‐propanol, and tert‐butanol and in their mixture with water at 25 °C. The structural analysis of the resulting polymers by a combination of ¹H NMR and MALDI‐TOF MS demonstrates the synthesis of perfectly bifunctional α,ω‐dibromo poly(methyl acrylate)s by SET‐LRP in alcohols. Moreover, this work provides an expansion of the list of solvents available for SET‐LRP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2745–2754, 2008     

Electrochemical Characterization of Myoglobin‐Polylysine Films at a Temperature Range of 6–80 °C

This work demonstrated for the first time that myoglobin cross‐linked in polylysine films is electrochemically active at 6 °C. At 6 °C, these protein films exhibited reversible reduction/oxidation peaks which are characteristic of Fe^III/Fe^II redox couple. The estimated current function densities (J=1.6×10^?4 C/V cm²), surface concentrations (Γ_T=0.10 nmol/cm²) and standard electron transfer constant (k_s=13.86 s^?1) at 6 °C for the data taken at a scan rate of 0.1 V/s were similar to those which were obtained at 10, 15 and 23 °C. Basically, this study shows a possible electrocatalytic application of these myoglobin/polylysine films, for example in low temperature sensing applications.     

High‐performance liquid chromatographic enantioseparation of isoxazoline‐fused 2‐aminocyclopentanecarboxylic acids on a chiral ligand‐exchange stationary phase

The application of a chiral ligand‐exchange column for the direct high‐performance liquid chromatographic enantioseparation of unusual β‐amino acids with a sodium N‐((R)‐2‐hydroxy‐1‐phenylethyl)‐N‐undecylaminoacetate‐Cu(II) complex as chiral selector is reported. The investigated amino acids were isoxazoline‐fused 2‐aminocyclopentanecarboxylic acid analogs. The chromatographic conditions were varied to achieve optimal separation. The effects of temperature were studied at constant mobile phase compositions in the temperature range 5–45°C, and thermodynamic parameters were calculated from plots of lnk or lnα versus 1/T. Δ(ΔH°) ranged from –2.3 to 2.2 kJ/mol, Δ(ΔS°) from –3.0 to 7.8 J mol^?1 K^?1 and –Δ(ΔG°) from 0.1 to 1.7 kJ/mol, and both enthalpy‐ and entropy‐controlled enantioseparations were observed. The latter was advantageous with regard to the shorter retention and greater selectivity at high temperature. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes. The sequence of elution of the enantiomers was determined in all cases.     

Preparation of perfluoro‐1,3‐propanedisulfonic acid/Nafion/silica hybrid nanoparticles—thermally stable Nafion in these silica hybrid nanoparticles even after calcination at 800 °C

Perfluoro‐1,3‐propanedisulfonic acid (PFPS)/Nafion/silica hybrid particles were prepared by the sol–gel reactions of PFPS with tetraethoxysilane and silica nanoparticles in the presence of Nafion under alkaline conditions. These obtained composites exhibited a good dispersibility and stability in not only water but also traditional organic media such as methanol, ethanol, 1,2‐dichloroethane, tetrahydrofuran, and dimethyl sulfoxide. Dynamic light scattering measurements and field‐emission scanning electron microscopy show that these hybrid particles are nanometer size‐controlled fine particles before and even after calcination at 800 °C. Nafion/silica hybrid nanoparticles were also prepared in the absence of PFPS under similar conditions. The weight of original Nafion markedly dropped around 350 °C and decomposed gradually, reaching 0% around 450 °C, and Nafion in the Nafion/silica nanocomposites exhibited a similar weight loss behavior to that of the original one. However, Nafion/PFPS/silica hybrid nanoparticles were found to exhibit no weight loss corresponding to the contents of Nafion and PFPS in the silica gel matrices even after calcination at 800 °C. It was demonstrated that the pH value (3.77 at 25 °C) of Nafion/PFPS/silica hybrid nanoparticles after calcination is smaller than that (5.66 at 25 °C) before calcination, and this hybrid nanoparticles exhibited a higher proton conductivity (5.8 × 10^?3 S/cm at 85 °C) than that (4.1 × 10^?3 S/cm at 85 °C) before calcination. In addition, Nafion/PFPS/silica hybrid nanoparticles after calcination at 800 °C were applied to the Friedel‐Crafts acylation of thiophene with acetic anhydride to give the expected 2‐acetylthiophene, of whose yield was similar to that before calcination under similar conditions. These findings suggest that Nafion in PFPS/silica hybrid nanoparticle cores should exhibit a nonflammable characteristic even after calcination at 800 °C to act as an effective acid catalyst. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1869–1877     

A polarizable dipole–dipole interaction model for evaluation of the interaction energies for NH···OC and CH···OC hydrogen‐bonded complexes

In this article, a polarizable dipole–dipole interaction model is established to estimate the equilibrium hydrogen bond distances and the interaction energies for hydrogen‐bonded complexes containing peptide amides and nucleic acid bases. We regard the chemical bonds N? H, C?O, and C? H as bond dipoles. The magnitude of the bond dipole moment varies according to its environment. We apply this polarizable dipole–dipole interaction model to a series of hydrogen‐bonded complexes containing the N? H···O?C and C? H···O?C hydrogen bonds, such as simple amide‐amide dimers, base‐base dimers, peptide‐base dimers, and β‐sheet models. We find that a simple two‐term function, only containing the permanent dipole–dipole interactions and the van der Waals interactions, can produce the equilibrium hydrogen bond distances compared favorably with those produced by the MP2/6‐31G(d) method, whereas the high‐quality counterpoise‐corrected (CP‐corrected) MP2/aug‐cc‐pVTZ interaction energies for the hydrogen‐bonded complexes can be well‐reproduced by a four‐term function which involves the permanent dipole–dipole interactions, the van der Waals interactions, the polarization contributions, and a corrected term. Based on the calculation results obtained from this polarizable dipole–dipole interaction model, the natures of the hydrogen bonding interactions in these hydrogen‐bonded complexes are further discussed. © 2013 Wiley Periodicals, Inc.     

Automatic simulated distillation of heavy petroleum fractions up to 800°C TBP by capillary gas chromatography. Part I: Possibilities and limits of the method

The characterization of heavy petroleum fractions is essential for the design and improvement of cracking plants converting heavy feedstock into valuable “white” products. Conventional simulated distillation methods using packed columns are unsuitable for this purposes, being limited to boiling points up to about 600°C. The method presented is able to cover a boiling points interval ranging from about 150°C up to around 800°C. It employs a short, nonpolar, highly thermostable capillary column routinely operated at temperatures around 430°C. The analytical system is based on a high temperature versions of a fully automatic, capillary dedicated gas chromatograph. The experimental data demonstrate that cold on-column injection is the sole sampling system suitable for such heavy compounds. The conversion of the retention times into boiling points, based on the use of low molecular weight polyethylenes, is extremely reliable, as demonstrated by the excellent retention time reproducibilities. The lower part (up to 550–600°C TBP) of the boiling point distribution curves of heavy petroleum fractions obtained on capillary columns fits well with the corresponding distribution curves based on packed column data. For the petroleum fractions fully eluted from the column the quantitative results obtained either using internal standards or by direct processing of the elution curves are in excellent agreement (less than 0.3 weight% differences). The method has been applied to the determination of the true boiling points corresponding to short path vacuum distillation (DISTACT) cut points over 300°C.     

High‐Energy Rechargeable Metallic Lithium Battery at −70 °C Enabled by a Cosolvent Electrolyte

Lithium metal is an ideal anode for high‐energy rechargeable batteries at low temperature, yet hindered by the electrochemical instability with the electrolyte. Concentrated electrolytes can improve the oxidative/reductive stability, but encounter high viscosity. Herein, a co‐solvent formulation was designed to resolve the dilemma. By adding electrochemically “inert” dichloromethane (DCM) as a diluent in concentrated ethyl acetate (EA)‐based electrolyte, the co‐solvent electrolyte demonstrated a high ionic conductivity (0.6 mS cm^?1), low viscosity (0.35 Pa s), and wide range of potential window (0–4.85 V) at ?70 °C. Spectral characterizations and simulations show these unique properties are associated with the co‐solvation structure, in which high‐concentration clusters of salt in the EA solvent were surrounded by mobile DCM diluent. Overall, this novel electrolyte enabled rechargeable metallic Li battery with high energy (178 Wh kg^?1) and power (2877 W kg^?1) at ?70 °C.