Butyl Ligands Research Articles

A monolithic stationary phase with dendritic nanostructures for the separation of PEGylated proteins.

Separation of PEGylated protein mixtures into individual species is a challenging procedure, and many efforts have been focused on creating novel chromatographic supports for this purpose. In this study, a new monolithic stationary phase with hyperbranched nanostructures was chemically synthesized. For this, monoliths with a support matrix of poly (glycidyl methacrylate-co-ethylene dimethacrylate) and ethylenediamine chemistry were modified with third-generation dendrons with butyl-end groups. The new monolith was analyzed by infrared spectroscopy, confirming the dendron with butyl ligands and exhibited low mass transfer resistance as observed by breakthrough frontal analysis. This support was able to separate mono-PEG ribonuclease A from the PEGylation mixture, indicated by a single band (∼30kDa) in the electrophoretic analysis. Moreover, the separation of mono-PEGylated positional isomers was probably observed, as the protein with ∼30kDa was found in two separate peaks. Interestingly, the dendronized monolith allowed the separation of the reaction mixture into individual PEGylated species when using high ammonium sulfate concentrations (2M). A correlation between the PEGylation degree and the strength of the hydrophobic interactions on the monolith was observed. This chromatographic approach combines the natural branched architecture of dendrons and the higher capabilities of the monoliths enhancing the hydrophobic surface area, and therefore the interaction between the PEGylated proteins and ligands. Thus, the novel support represents a novel platform for the purification of PEGylated from non-PEGylated proteins with biotechnological applications.

Gas-phase computational study of tetra-n-butylammonium ion conformational mobility

The energy profiles of various configurations of the tetra-n-butylammonium ion (Bu4N+) arising by changing the angle between a pair of butyl ligands, as well as by rotating of various alkyl fragments in gas phase, were calculated using DFT methods. A hypothesis about the most probable way of changing the conformations of tetra-n-butylammonium ions during the phase transitions in highly conductive solid electrolytes was proposed.

Thermal and radiation chemistry of butyltin oxo hydroxo: A model inorganic photoresist

We have investigated the thermal and radiation chemistry of an organotin-based model photoresist to elucidate patterning mechanisms related to extreme ultraviolet (EUV) lithography. Butyltin oxide hydroxide (BuSnOOH) was dissolved in organic solvents and spin-coated to form uniform thin films. The thermal stability and radiation sensitivity of the thin films were characterized by temperature programmed desorption (TPD), electron stimulated desorption (ESD), and X-ray photoelectron spectroscopy (XPS). From the TPD studies, we determined that decomposition of BuSnOOH occurs at ~653 K through cleavage of the butyl-tin bond. Low kinetic energy electron (Ekin = 80 eV) and X-ray (1486.6 eV) exposure also resulted in cleavage of the butyl-tin bond with the resulting desorption of butyl ligands from the film. From the ESD data, we estimated that the butyl ligand desorption cross section was ~4.3 × 10−14 cm2 for electrons with 80 eV kinetic energy. From the XPS results, we found a significant reduction in C 1s intensity for extended X-ray exposures, which corresponds to butyl ligand loss. There were also changes in the O 1s spectra indicating loss of hydroxyl groups and tin oxide network formation during radiation exposure. These results indicate the preferential dissociation and desorption of butyl ligands that can occur through either thermal or radiation induced processes, and that butyl ligand loss leads to the solubility contrast.

Protein adsorption onto monoliths: A surface energetics study.

This part of work was done to explore the basic understanding of the adsorption chromatography by determining the interaction of selected model proteins (n = 5) to monolithic chromatographic materials, with varying densities of butyl and phenyl ligands. Surface energetics approach was applied to study the interaction behavior. The physicochemical properties of the proteins and monolithic chromatographic materials were explored by contact angle and zeta potential values. These values were used to study protein to monolith interaction under various operating conditions. Surface energetics approach allowed the calculation of interaction energy as a function of distance, i.e. energy minimum values. Calculations were performed at various conditions to analyze the effect of major operating parameters on the interaction strength. The interaction strength exposed the hydrophobic nature of the monoliths which increases with increasing ligand density. Further, interaction energy of proteins were higher with monolith with butyl ligand compared to monolith with phenyl ligand. For instance, lactoferrin interaction to monoliths with butyl represents more interaction, i.e. 24.38 kT as compared to monoliths with phenyl i.e. 23.28 kT, keeping lambda as 0.2 nm and salt concentration as 100mM of ammonium sulphate. Hence, more energy and time will be consumed for elution of proteins immobilized to monoliths with butyl. Similarly, the effect of solid surface for proteins immobilization, effect of ligand density and effect of lambda showed some interesting insights on the interaction behavior. The knowledge generated from the present work will help in the basic understanding as well as development of an efficient, low cost downstream processing design and may mimic the real chromatographic experiments.

Reaction Mechanisms of the Atomic Layer Deposition of Tin Oxide Thin Films Using Tributyltin Ethoxide and Ozone.

Uniform and conformal deposition of tin oxide thin films is important for several applications in electronics, gas sensing, and transparent conducting electrodes. Thermal atomic layer deposition (ALD) is often best suited for these applications, but its implementation requires a mechanistic understanding of the initial nucleation and subsequent ALD processes. To this end, in situ FTIR and ex situ XPS have been used to explore the ALD of tin oxide films using tributyltin ethoxide and ozone on an OH-terminated, SiO2-passivated Si(111) substrate. Direct chemisorption of tributyltin ethoxide on surface OH groups and clear evidence that subsequent ligand exchange are obtained, providing mechanistic insight. Upon ozone pulse, the butyl groups react with ozone, forming surface carbonate and formate. The subsequent tributyltin ethoxide pulse removes the carbonate and formate features with the appearance of the bands for CH stretching and bending modes of the precursor butyl ligands. This ligand-exchange behavior is repeated for subsequent cycles, as is characteristic of ALD processes, and is clearly observed for deposition temperatures of 200 and 300 °C. On the basis of the in situ vibrational data, a reaction mechanism for the ALD process of tributyltin ethoxide and ozone is presented, whereby ligands are fully eliminated. Complementary ex situ XPS depth profiles confirm that the bulk of the films is carbon-free, that is, formate and carbonate are not incorporated into the film during the deposition process, and that good-quality SnOx films are produced. Furthermore, the process was scaled up in a cross-flow reactor at 225 °C, which allowed the determination of the growth rate (0.62 Å/cycle) and confirmed a self-limiting ALD growth at 225 and 268 °C. An analysis of the temperature-dependence data reveals that growth rate increases linearly between 200 and 300 °C.

Di-n-butyl-bis-[N-(2-meth-oxy-eth-yl)-N-methyl-dithio-carbamato-κ2S,S']tin(IV): crystal structure and Hirshfeld surface analysis.

The complete mol-ecule of the title compound, [Sn(C4H9)2(C5H10NOS2)2], is generated by a crystallographic mirror plane, with the SnIV atom and the two inner methyl-ene C atoms of the butyl ligands lying on the mirror plane; statistical disorder is noted in the two terminal ethyl groups, which deviate from mirror symmetry. The di-thio-carbamate ligand coordinates to the metal atom in an asymmetric mode with the resulting C2S4 donor set defining a skew trapezoidal bipyramidal geometry; the n-butyl groups are disposed to lie over the longer Sn-S bonds. Supra-molecular chains aligned along the a-axis direction and sustained by methyl-ene-C-H⋯S(weakly coordinating) inter-actions feature in the mol-ecular packing. A Hirshfeld surface analysis reveals the dominance of H⋯H contacts in the crystal.

High-resolution magic angle spinning (1) H NMR measurement of ligand concentration in solvent-saturated chromatographic beads.

A method based on 1H high‐resolution magic angle spinning NMR has been developed for measuring concentration accurately in heterogeneous materials like that of ligands in chromatography media. Ligand concentration is obtained by relating the peak integrals for a butyl ligand in the spectrum of a water‐saturated chromatography medium to the integral of the added internal reference. The method is fast, with capacity of 10 min total sample preparation and analysis time per sample; precise, with a reproducibility expressed as 1.7% relative standard deviation; and accurate, as indicated by the excellent agreement of derived concentration with that obtained previously by 13C single‐pulse excitation MAS NMR. The effects of radiofrequency field inhomogeneity, spin rate, temperature increase due to spinning, and distribution and re‐distribution of medium and reference solvent both inside the rotor during spinning and between bulk solvent and pore space are discussed in detail. © 2016 The Authors Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.

¹³C SPE MAS measurement of ligand concentration in compressible chromatographic beads.

A method for measuring the ligand concentration in heterogeneous materials like chromatography media is described. In this method, 13C single pulse excitation magic angle spinning NMR experiment with broadband 1H decoupling is used to determine the peak integrals for a butyl ligand in the spectrum of a dried chromatography medium. Within a carefully controlled protocol, those integrals compared with that of the internal reference compound dimethyl sulfone provide the required volume concentration with an accuracy of ca 2%. The effects of temperature, degree of hydration, and other experimental parameters are discussed. Copyright © 2015 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.

Green Gold: Au30(S-t-C4H9)18 Molecules

Here, we report the synthesis and separation of Au30(tert-thiol)18 (tert-thiol = tert-butanethiol and 1-adamantanethiol) from a mixture of sizes of bulky-ligated nanoparticles. With precisely 30 gold metal atoms and 18 tertiary butyl ligands, this new 30 Au atom molecule is assigned a formula based on results obtained in high-resolution electrospray ionization (ESI) mass spectrometry. UV-vis-NIR spectroscopy shows a distinct electronic transition featured at 620 nm, with a valley in the green wavelength 520–570 nm region, explaining the green appearance. This lack of absorbance in the green region is uncommon, and therefore, metal nanoparticles of green color are extremely rare. Its optical band gap, 1.76 eV is much different than the 1.3 eV reported for Au25(SR)18. We report its reproducible direct synthesis (∼10 mg) in a one-pot reaction, with two different ligands. Because of the unique optical properties and altered-discrete sizes, there is a fundamental need for structural analysis of this nanoparticle.

Synthesis and properties of nanosilicon stabilized by butyl and perfluorobutyl ligands

Nanocrystalline silicon stabilized by butyl and perfluorobutyl ligands that form improper surface states of silicon nanocrystals were synthesized. The presence of perfluorobutyl ligands on the surface of silicon nanocrystals was proved by IR spectroscopy. Nanocrystals with perfluorobutyl ligands form aggregates, which decreases the efficiency of photoluminescence. The nanocrystals with butyl ligands have smaller size but their photoluminescence can be clearly recorded.

Reactions at Interfaces: Oxygenation ofn-Butyl Ligands Anchored on Silica Surfaces with Methyl(trifluoromethyl)dioxirane

The oxygenation of n-butyl and n-butoxy chains bonded to silica with methyl(trifluoromethyl)dioxirane (1) revealed the ability of the silica matrix to release electron density toward the reacting C(2)-H σ-bond through the Si-C(1) and Si-O(1) σ-bonds connecting the alkyl chain to the surface (silicon β-effect). The silica surface impedes neither the alkyl chain adopting the conformation required for the silicon β-effect nor dioxirane 1 approaching the reactive C(2) methylene group. Reaction regioselectivity is insensitive to changes in the solvation of the reacting system, the location of organic ligands on the silica surface, and the H-bonding character of the silica surface. Reaction rates are faster for those organic ligands either within the silica pores or bonded to hydrophilic silica surfaces, which evidence the enhanced molecular dynamics of confined dioxirane 1 and the impact of surface phenomena on the reaction kinetics. The oxygenation of n-butyl and n-butoxy chains carrying trimethylsilyl, trimethoxysilyl, and tert-butyl groups with dioxirane 1 under homogeneous conditions confirms the electronic effects of the silyl substituents and the consequences of steric hindrance on the reaction rate and regioselectivity. Orthosilicic acid esters react preferentially at the methylene group adjacent to the oxygen atom in clear contrast with the reactivity of the carboxylic or sulfonic acid alkyl esters, which efficiently protect this position toward oxidation with 1.

Synthesis of thermo-sensitive copolymer with affinity butyl ligand and its application in lipase purification

In this study, thermo-sensitive N-alkyl substituted polyacrylamide polymer P(NNB) was synthesized by using N-hydroxymethyl acrylamide(NHAM), N-isopropyl acrylamide (NIPA) and butyl acrylate (BA) as monomers, and its low critical solution temperature (LCST) was controlled to be 28 degrees C. The recovery of the thermo-sensitive polymer was over 98%. Butanol as a hydrophobic ligand was covalently attached onto polymer P(NNB) and butyl ligand density was 80 micromol g(-1) polymer. The affinity polymer was used for purification of lipase from crude material. Optimized condition was pH 7.0, 35 degrees C adsorption temperature, 120 min adsorption time and 0.5 mg ml(-1) initial concentration of lipase. The adsorption isotherm accords with a typical Langmuir isotherm. The maximum adsorption capacity (Q(m)) of the affinity polymer for lipase was 24.8 mg g(-1)polymer. The affinity copolymer could be recycled by temperature-inducing precipitation and there was only about 6% loss of adsorption capacity after five recyclings. Specific activity of lipase was improved from 14IU mg(-1) to 506 IU mg(-1) protein, and its recovery achieved 82%. The affinity polymer is suitable for the purification of target proteins from the crude material with large volume and dilute solution.

Silica‐Supported Zirconium Complexes and their Polyoligosilsesquioxane Analogues in the Transesterification of Acrylates: Part 1. Synthesis and Characterization

AbstractVarious silica‐supported acetylacetonate and alkoxy zirconium(IV) complexes have been prepared and characterized by quantitative chemical measurements of the surface reaction products, quantitative surface microanalysis of the surface complexes, in situ infrared spectroscopy, CP‐MAS 13C NMR spectroscopy and EXAFS. The complex (SiO)Zr(acac)3 (acac=acetylacetonate ligand) (1) can be obtained by reaction of zirconium tetraacetylacetonate [Zr(acac)4] with a silica surface previously dehydroxylated at 500 °C. The complexes (SiO)3Zr(acac) (2) and (SiO)3Zr(O‐n‐Bu) (n‐Bu=butyl ligand) (3) can be synthesized by reaction of (SiO)3ZrH with, respectively, acetylacetone and n‐butanol at room temperature. The spectroscopic data, including EXAFS spectroscopy, confirm that in compound 1 the zirconium is linked to the surface by only one SiOZr bond whereas in the case of compounds 2 and 3 the zirconium is linked to 3 surface oxygen atoms which are sigma bonded. EXAFS data indicate also that the acetylacetonate ligands behave as chelating ligands leading to a hepta‐coordination around the zirconium atom in 1 and a penta‐coordination in 2. In order to provide a molecular analogue of 1, the synthesis of the following polyoligosilsesquioxane derivative (c‐C5H9)7Si8O12(CH3)2Zr(acac)3 (1′) was achieved. The compound 1′ is obtained by reacting (c‐C5H9)7Si8O11(CH3)2(OH), 4, with an equimolecular amount of Zr(acac)4. In the same manner, syntheses of complexes (c‐C5H9)7Si7O12Zr(acac) (2′) and of (c‐C5H9)7Si7O12Zr(O‐n‐Bu) (3′) were achieved by reaction of the unmodified trisilanol, (c‐C5H9)7Si7O9(OH)3, with respectively Zr(acac)4 and Zr(O‐n‐Bu)4 at 60 °C in tetrahydrofuran. Compounds 1′, 2′ and 3′ can be considered as good models of 1, 2 and 3 since their spectroscopic properties are comparable with those of the surface complexes. The synthetic results obtained will permit us to study the catalytic properties of these surface complexes and of their molecular analogues with the ultimate goal of delineating clear structure‐activity relationships.

Determination of the secondary structure of proteins in different environments by FTIR‐ATR spectroscopy and PLS regression

The secondary structures of proteins (alpha-helical, beta-sheet, beta-turn, and random coil) in the solid state and when bound to polymer beads, containing immobilized phenyl and butyl ligands such as those as commonly employed in hydrophobic interaction chromatography, have been investigated using FTIR-ATR spectroscopy and partial least squares (PLS) methods. Proteins with known structural features were used as models, including 12 proteins in the solid state and 7 proteins adsorbed onto the hydrophobic surfaces. A strong PLS correlation was achieved between predictions derived from the experimental data for 4 proteins adsorbed onto the phenyl-modified beads and reference data obtained from the X-ray crystallographic structures with r(2) values of 0.9974, 0.9864, 0.9924, and 0.9743 for alpha-helical, beta-sheet, beta-turn, and random coiled structures, respectively. On the other hand, proteins adsorbed onto the butyl sorbent underwent greater secondary structural changes compared to the phenyl sorbent as evidenced from the poorer PLS r(2) values (r(2) are 0.9658, 0.9106, 0.9571, and 0.9340). The results thus indicate that the secondary structures for these proteins were more affected by the butyl sorbent, whereas the secondary structure remains relatively unchanged for the proteins adsorbed onto the phenyl sorbent. This study has important ramifications for understanding the nature of protein secondary structural changes following adsorption onto hydrophobic sorbent surfaces. This knowledge could also enable the development of useful protocols for enhancing the chromatographic purification of proteins in their native bioactive states.

2-(Ethoxycarbonyl)quinolinium butyltrichlorido(quinoline-2-carboxylato-κ2N,O)stannate(IV)

In the title compound, (C12H12NO2)[Sn(C4H9)(C10H6NO2)Cl3], the Sn atom is coordinated by one O and one N atom of a quinolinium-2-carboxyl­ate anion, three Cl atoms and one butyl ligand within a distorted octa­hedron. Three C atoms of the butyl ligand are disordered and were refined using a split model; the site occupancies are 0.57 and 0.43. The NH group of the cation is involved in inter­molecular N—H⋯O hydrogen bonding.

Polynuclear diorganotin(IV) complexes with arylhydroxamates: Syntheses, structures and in vitro cytotoxic activities

Series of polynuclear diorganotin(IV) complexes with di-halogenbenzohydroxamate ligands (substituents=2,4-Cl2, 2,4-F2, 3,4-F2, 2,5-F2, 2,6-F2), formulated as the polymeric [R2SnL]na (1:1) and the tetranuclear [R4Sn2(HL)2(L)]2b (2:3) (HL=arylhydroxamate), were prepared and characterized by FT-IR, 1H, 13C, 119Sn NMR spectroscopies, elemental analyses and melting point measurements. X-ray diffraction analyses were also carried out for the representative complexes [Me2Sn{2,4- F2C6H3C(O)NO}]n2a and [n-Bu4Sn2{2,4- F2C6H3C(O)NHO}2 {2,4-F2C6H3C(O)NO}] 21b and show that the ligated mono- and di-basic forms, HL and L, of the arylhydroxamic acid (H2L) display the oxamic and oximic tautomeric forms, respectively. These compounds exhibit in vitro cytotoxicities toward human leukemic promyelocites HL-60, BGC-823, BEL-7402 and KB cell lines which, in some cases, are identical to, or even higher than, that of “cisplatin”. The polymeric diorganotin/hydroxamato complexes a containing the long carbon chain butyl ligands are the most active ones, and the dependence of the antitumor activity of the complexes on various factors, namely the nuclearity, the organic ligand, the type, position and number of the X ring substituents, is also discussed.

Synthesis and Morphological, Electrochemical Characterization of Sn92Co8 Nanoalloys for Anode Materials in Li Secondary Batteries

Uniformly distributed carbon-coated nanoalloys with a particle size of 50 and were prepared using a butyllithium and naphthalide solution at 500 and , respectively. The samples annealed at were covered with an amorphous carbon layer with a thickness of about , but its thickness was shrunk to when annealed at . The first charge capacity increased with increasing annealing temperature and exhibited 380 and at 600 and , respectively. This is due to enhanced ordering of the carbon layer structure and full decomposition of the butyl ligands that limited Li-ion intercalation/deintercalation. The capacity retention of the nanoalloys annealed at 500 and was 76 and 54% after 30 cycles at a rate of , while that of bulk alloy was 15%. Much improved capacity retention of the carbon-coated nanoalloys is associated with the thicker carbon layer on the particle surface that acts as a more effective buffer layer for volume expansion during lithium alloying/dealloying than that of the bulk alloy.

Investigation of protein retention and selectivity in HIC systems using quantitative structure retention relationship models

In the present work, the effect of stationary phase resin chemistry and protein physicochemical properties on protein binding affinity in hydrophobic interaction chromatography (HIC) was investigated using linear gradient chromatography and quantitative structure-retention relationship (QSRR) modeling. Linear gradient experiments were carried out for a set of model proteins on four different HIC resins having different backbone and ligand chemistry. The retention data exhibited significant differences in protein binding affinity, not only across the phenyl and butyl ligand chemistries, but also for the different backbone chemistries found in the Sepharose (cross-linked agarose) and the Toyopearl 650 M (polymethacrylate) series of resins. QSRR models based on a Support Vector Machine (SVM) approach were developed for the linear retention data using molecular descriptors based on protein crystal structure and primary sequence information as well as a set of new hydrophobicity descriptors based on the solvent accessible protein surface area. The results indicate that the QSRR models were successfully able to capture and selectivity predict the changes observed in these systems. Furthermore, the new descriptors resulted in physically interpretable models of protein retention and provided insights into the factors influencing protein affinity in these different HIC systems. The approach put forth in this study provides a framework for developing predictive tools and for gaining insight into protein selectivity in hydrophobic interaction chromatography.

Capillary electrochromatography of therapeutic peptides on mixed-mode butylmethacrylate monoliths

In this study, a porous mixed-mode n-alkyl methacrylate-based monolith has been used in the separation of therapeutic peptides. While the sulfonic acid (SCX) moiety derived from 2-acrylamido-2-methyl-1-propanesulfonic acid supports the generation of a stable electroosmotic flow (EOF) at both acidic and basic pH values, the butyl ligands provide the nonpolar sites for chromatographic resolution. The performance of the monolith was evaluated regarding the influence of pH on chromatographic resolution of peptides. The suitability of the butylmethacrylate/SCX monolith for the analysis of therapeutic peptides containing basic centres, for example arginine, at moderately high pH 9.5 and the stability to repeat injections of a mixture of peptides was demonstrated. Separations with efficiencies as high as 5.0 x 10(5) plates/m were obtained and the migration behaviour of the peptides at both low (2.8) and high (9.5) pH values could be rationalised based on their charge, molecular mass/shape and relative hydrophobicities.

Use of NMR Spectroscopy in the Synthesis and Characterization of Air- and Water-Stable Silicon Nanoparticles from Porous Silicon

Air- and water-stable silicon nanocrystals were prepared by the bromine oxidation of porous silicon nanoparticles followed by reaction with n-butyllithium. Transmission electron microscopy suggests that the vigorous oxidation of porous silicon under reflux conditions removes the porous layer from the nanoparticle to expose a crystalline silicon core that can be passivated with organic ligands. A combination of infrared, ultraviolet/visible, and photoluminescence demonstrate the presence of small crystalline silicon particles and saturated hydrocarbon ligands, while solid- and liquid-state nuclear magnetic resonance spectroscopies establish that butyl ligands are localized on the nanocrystal surface. All of these analytical methods suggest that the product of this synthesis is stable in air and water indefinitely.