Polymeric alkenoxy amino acid surfactants: IV. effects of hydrophobic chain length and degree of polymerization of molecular micelles on chiral separation of beta-blockers

Four alkenoxy leucine-based surfactants with C8-C11 chains containing a terminal double bond, and one C11 chain surfactant with a terminal triple bond are synthesized and characterized in monomeric and polymeric forms. These polymeric pseudophases are then utilized to study the influence of chain length and DP for the enantioseparations of seven beta-blockers in MEKC. Variations in chain length and concentration of polymeric surfactants showed significant effects on the chiral resolution (Rs) and efficiency (N). A relatively large elution range combined with the highest polarity and aggregation number (A) but the lowest retention time, partial specific volume, and optical rotation generated with C8-polymeric surfactant results in simultaneous enantioseparation of all seven beta-blockers with higher N and R(s). In particular, highly hydrophobic beta-blockers are better resolved with shorter hydrocarbon chain even at higher surfactant concentration, which is unachievable with longer chain surfactant. On the other hand, polymer derived from C11-triple bond provided smaller A value compared to C11-double bond surfactant. However, chiral Rs of hydrophobic beta-blockers are still achievable with the C11-triple bond surfactant with enhanced N and shorter analysis time. In addition, effect of polymerization concentration is evaluated by polymerizing all five surfactants at five times their respective CMCs and 100 mM equivalent monomer concentrations. Polymerization of shorter chain (C8 and C9) double-bonded surfactants at five times their respective CMCs results in higher A values with better chiral Rs and N compared to the same two surfactants polymerized at 100 mM.     

Signalling probe displacement electrochemical aptasensor for malignant cell surface nucleolin as a breast cancer biomarker based on gold nanoparticle decorated hydroxyapatite nanorods and silver nanoparticle labels

Nucleolin is a multifunctional protein that is markedly overexpressed on the surface of most cancer cells. By taking advantage of the high affinity and specificity of the AS1411 aptamer for nucleolin, a signalling probe displacement electrochemical aptasensor was developed. The thiolated AS1411 aptamer was conjugated to hydroxyapatite nanorods (HApNRs) decorated with gold nanoparticles (AuNPs). To further increase the electrical conductivity of the interface, the ionic liquid 1-ethyl-3-methylimidazolium alanine with its high ion conductivity was placed on the electrode surface. Then, the aptamer was immobilized on the modified electrode and conjugated to signalling c-DNA tagged with AgNPs (c-DNA@AgNPs). In the presence of the MCF7 target cells, the signalling probe is displaced and released from the electrode surface. This leads to a decrease in the current that is proportional to the concentration of cancer cells in the range from 10 to 10⁶ cells mL^?1, with a detection limit as low as 8?±?2 cells mL^?1 (n?=?3) (based as 3σ/m, where σ is the standard deviation of the blank and m is the slope of the calibration plot). This method presents a promising tool for highly sensitive and selective detection of surface nucleolin on MCF7 cancer cells.

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Graphical abstract HApNR-AuNP-AS1411 aptamer nanocomposite as an electrochemical sensing interface was immobilized on the gold electrode surface and conjugated to signaling c-DNA tagged with AgNPs for determination of surface nucleolin on MCF7 cancer cells.

     

Design and development of several polymeric metal–organic frameworks,spectral characterization,and their antimicrobial activity

Coordination polymers were obtained by the reaction of metal acetates, M(CH₃COO)₂·xH₂O {where M = Mn(II), Co(II), Ni(II) and Cu(II)} with AFP ligand (AFP = 5,5'-(piperazine-1,4-diylbis(methylene))bis(2-aminobenzoic acid). The AFP ligand was prepared by the one-pot, two-step reaction of formaldehyde, 2-aminobenzoic acid, and piperazine. Structural and spectroscopic properties have been studied by elemental, spectral (FT-IR, ¹H NMR, ¹³C NMR, and UV–vis), and thermogravimetric analysis. UV–vis spectra and magnetic moment values indicate that Mn(II), Co(II), and Ni(II) polymer–metal complexes are octahedral, while Cu(II) and Zn(II) polymer–metal complexes are distorted octahedral and tetrahedral, respectively. The analytical data confirmed that the coordination polymers of Mn(II), Co(II), Ni(II), and Cu(II) are coordinated with two water molecules, which are further supported by infrared spectra and thermogravimetric analysis data. The prepared polymer–metal complexes showed good antibacterial activities against all tested microorganisms; however, the AFP ligand was also found to be effective, but relatively less than their polymer–metal complexes. Along with antibacterial activity, all the polymer–metal complexes exhibit significant antifungal activity against most of the tested fungal strains. The results of antimicrobial activity reveals that the AFP–Cu(II) showed the highest antibacterial and antifungal activity than other polymer–metal complexes.     

Chiral separation of polychlorinated biphenyls using a combination of hydroxypropyl-gamma-cyclodextrin and a polymeric chiral surfactant

Chiral separation of moderately to highly hydrophobic polychlorinated biphenyls (PCBs) using a conventional chiral micelle or a polymeric chiral surfactant, as the single chiral selector is very difficult since the hydrophobic interactions between the chiral PCB and the monomeric or polymeric surfactant is very strong. Combined use of a polymeric chiral surfactant, polysodium N-undecanoyl-D-valinate (poly-D-SUV) with hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) was successful in cyclodextrin modified electrokinetic chromatography (CD-EKC) enantioseparation of PCB congeners. Addition of HP-gamma-CD to the background electrolyte containing poly-D-SUV functioned to improved chiral resolution for the PCBs and reduce the analysis time for these congeners. In addition, concentration of methanol, concentration of 2-(N-cyclohexylamino) ethanesulfonic acid (CHES) buffer and separation voltage was also varied to optimize multicomponent separation of five chiral PCBs. Simultaneous separation and enantioseparation of all five PCBs was possible in less than 50 min under optimized conditions that requires a 5 mM CHES solution buffered at about pH 10 with 1.5% w/v (ca. 60 mM) poly-D-SUV and 16 mM HP-gamma-CD. In addition, 1 M urea and 20% v/v methanol should be added as organic modifier and the capillary temperature maintained at 45 degrees C. As expected the polymeric surfactant showed improved chiral resolution of PCBs over conventional micelles of SUV. Under optimized conditions, when CD-EKC of chiral PCBs using poly-D-SUV was compared to sodium dodecyl sulfate (SDS), better resolution, higher efficiency and shorter analysis time was achieved with poly-D-SUV.     

Polymeric sulfated surfactants with varied hydrocarbon tail: II. Chemical selectivity in micellar electrokinetic chromatography using linear solvation energy relationships study

The effect of hydrocarbon chain length on chemical selectivity in micellar electrokinetic chromatography (MEKC) was investigated using polymeric sulfated surfactants: poly-(sodium 7-octenyl sulfate), poly(sodium 8-nonenyl sulfate), poly(sodium 9-decenyl sulfate), and poly(sodium 10-undecenyl sulfate). Linear solvation energy relationships (LSERs) and free energy of transfer studies were conducted to predict the selectivity differences between the four polymeric surfactants. The overall nature of the solute/ polymeric micelle interactions was found to be different despite the fact that all polymeric surfactants have the same head group. The polar character and acidic strength of the polymeric surfactant are found to decrease as the hydrocarbon chain length of the surfactant is increased. On the other hand, the polarizability of the polymeric sulfated surfactants increases (upon interacting with solute lone-pair electrons) with increasing hydrocarbon chain length. The LSER results show that the solute size and hydrogen bond accepting ability play the key roles in MEKC retention.     

DFT Study of Physisorption Effect of the Curcumin on CNT(8,0-6) Nanotube for Biological Applications

In the given work the adsorption properties of molecule curcumin((1 E,6 E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) on CNT(8,0-6) nanotube were investigated by the density functional theory(DFT) in the solvent water for the first time. The non-bonded interaction effects of compounds curcumin and CNT(8,0-6) nanotube on the electronic properties, UV/Vis spectra, chemical shift tensors and natural charges were determined and discussed. The electronic spectra of the compound curcumin and the complex CNT(8,0-6)/curcumin in the solvent water were calculated by time dependent density functional theory(TD-DFT) for investigation of the maximum wavelength value of molecule Curcumin before and after the non-bonded interaction with the CNT(8,0-6) nanotube and molecular orbitals involved in the formation of absorption spectrum of the complex CNT(8,0-6)/curcumin at maximum wavelength.     

Combination of cyclodextrins and polymeric surfactants for chiral separations

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method was applied to the enantioseparation of three binaphthyl derivatives using neutral CDs (i.e., beta- and gamma-CD) in combination with various chiral amino acid-based polymeric surfactants (PSs). Both the D- and L-configurations of poly(sodium N-undecanoyl alaninate), poly(sodium N-undecanoyl leucinate), and poly(sodium N-undecanoyl valinate) (poly(L-SUV)) were synthesized. The retention behavior of the three binaphthyl derivatives under optimum electrophoretic conditions using a single chiral additive (PS or CD) is discussed. In addition, the effect of CD cavity size and stereochemical configuration of polymeric surfactants on selectivity (alpha) and resolution (Rs) was investigated. The enantioseparation of (+/-)1,1'-binaphthyl-2,2'-diamine gave a reversal of enantiomeric order when using beta-CD in combination with any of the three D-configuration PS. However, better enantioseparation is obtained when using the corresponding L-configuration PS with beta-CD. A reversal of migration order (RMO) for the enantiomers of (+/-)1,1'-bi-2-naphthol was observed upon the addition of 10 mM gamma-CD to poly(L-SUV). However, no RMO of (+/-)1,1'-bi-2-naphthol was seen when either beta-CD or gamma-CD was combined with D-PS. The enantiomers of (+/-)1,1'-binaphthyl-2,2'-diyl hydrogen phosphate showed little enantioselective behavior toward the PS alone. However, combined D- or L-PS and beta-CD or gamma-CD systems gave increased Rs and alpha values. The chiral recognition of binaphthyl derivatives observed resulting from the various combinations of two chiral selectors is discussed.     

A modified square well model in obtaining the surface tension of pure and binary mixtures of hydrocarbons

A model based on the perturbation theory of fluids was proposed to correlate the experimental data for surface tension of pure hydrocarbons in a wide range of temperature. The results obtained for the pure hydrocarbons were directly used to predict the surface tension for binary hydrocarbon mixtures at various temperatures. In the proposed model, a modified form of the square well potential energy between the molecules of the reference fluid was taken into account while the Lennard–Jones dispersion energy was considered to be dominant amongst the molecules as the perturbed term to the reference part of the model. In general, the proposed model has three adjustable parameters which are chain length, m, size, σ, and energy, ε/κ, parameters, but in some cases the number of parameters was reduced to two, thereby setting the chain length to be unity for pure hydrocarbons. The regressed values of these parameters were obtained using the experimental data for pure hydrocarbons at different temperatures. The results showed that these parameters can be related to the molar mass of hydrocarbons. The model was also extended to predict the surface tension of binary hydrocarbon mixtures using the parameters obtained for the pure compounds. It is worth noting that no additional parameter has been introduced into the model in the extension of the model to the mixtures studied in this work. The results showed that the proposed model can accurately correlate the surface tension of pure hydrocarbons. Also the results showed that the surface tension for binary mixture of hydrocarbons can be accurately predicted using the proposed model over a wide temperature range.     

Synthesis, crystal structure and magnetic properties of a new pillared perovskite La5Mo2.75V1.25O16

A new pillared perovskite compound La₅Mo_2.76(4)V_1.25(4)O₁₆, has been synthesized by solid-state reaction and its crystal structure has been characterized using powder X-ray and neutron diffraction. The magnetic properties of this compound have been investigated using SQUID magnetometry, and the magnetic structure has been studied using neutron diffraction data. A theoretical calculation of relative strengths of spin interactions among different magnetic ions and through different pathways has been performed using extended Hückel, spin dimer analysis. The crystal structure of this material contains perovskite-type layers that are connected through edge-sharing dimeric units of octahedra. The structure is described in space group C2/m with unit cell parameters a=7.931(2) Å, b=7.913(2) Å, c=10.346(5) Å and β=95.096(5)°. The material shows both short-range ferrimagnetic correlations from ∼200 to 110 K and long-range antiferromagnetic order below T_c∼100 K. The magnetic structure was investigated by neutron diffraction and is described by k=(0 0 ) as for other pillared perovskites. It consists of a ferrimagnetic arrangement of Mo and V within the layers that are coupled antiferromagnetically between layers. This is the first magnetic structure determination for any Mo-based pillared perovskite.     

Quantitation of tryptophan and kynurenine in human plasma using 4-vinylphenylboronic acid column by capillary electrochromatography coupled with mass spectrometry

Tryptophan (TRP) is an essential amino acid catabolized mainly through the kynurenine pathway, and part of it is catabolized in the brain. The abnormal depletion of TRP and production of kynurenine (KYN) by two enzymes, tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), have been linked to various neurological diseases. The ratio of TRP/KYN in plasma is a valuable measure for IDO/TDO activity and the prognosis of disease conditions. The 4-vinylphenylboronic acid (4-VPBA) was evaluated as a novel stationary phase for OT–CEC–MS/MS. TRP, KYN, and 3-hydroxykynurenine were separated using optimum conditions of 15 mM (NH₄)₂CO₃ at pH 8 as a background electrolyte and 25 kV separation voltage on a 90 cm column. The usefulness of the 4-VPBA column for simple, fast, repeatable, and sensitive CEC–ESI–MS/MS application was demonstrated for the quantitation of TRP and KYN in the plasma of healthy human subjects and neuroinflammation subjects. The plasma sample was extracted on a zirconia-based ion-exchange cartridge for simultaneous protein precipitation and phospholipid removal. The method of standard addition, in combination with the internal standards approach, was used to prepare the calibration curve to overcome matrix matching and eliminate procedural errors. The developed quantitation method was validated according to FDA guidelines for sensitivity, accuracy, precision, and extraction recovery. The measured plasma level of TRP and KYN in healthy humans is aligned with the human metabolome database for the same two metabolites.