To minimize non‐specific protein adsorption on macroporous poly(glycidyl methacrylate) and poly(2‐hydroxyethyl methacrylate) microspheres containing amino and/or carboxyl groups, the microspheres are coated with α,ω‐bis‐carboxy poly(ethylene glycol) and amino‐terminated poly(ethylene glycol‐co‐propylene glycol) or α‐methoxy‐ω‐amino poly(ethylene glycol). Adsorption of bovine serum albumin (BSA), γ‐globulin, 125I‐BSA, pepsin, and chymotrypsin on neat and PEGylated microspheres is determined by UV–VIS spectroscopy of supernatants and eluates or by measurement of radioactivity in an ionization chamber. Neat and PEGylated microspheres adsorb 0.8–70% and 0.02–44% of protein, respectively.
The methods for separation of R,S‐tolterodine and R,S‐methoxytolterodine enantiomers using sulfated α‐, β‐CD and phosphated‐γ‐CD by CE in acidic BGE based on Tris/phosphate pH 2.5 buffer were developed. Sulfated α‐ and β‐CD allow anodic detection while phosphated‐γ‐CD allows only cathodic detection of the separated enantiomers. The influence of chiral selector (CS)'s concentration as well as the influence of composition and concentration of BGE on resolutions were studied. Reversal migration order of tolterodine and methoxytolterodine enantiomers was observed, when sulfated‐α‐ and sulfated‐β‐CD were used. The developed methods with all three studied CSs, were validated and compared. All proposed methods enable determination of 0.2% of S‐tolterodine as an optical impurity in pills, however the method with phosphated‐γ‐CD provided lower detection limit, better repeatability of peak areas and migration times, and also lower consumption of CS. Developed method employing phosphated‐γ‐CD that was applied for the determination of optical purity of R‐tolterodine in commercial pills. 相似文献
Two polysaccharide stationary phases have been newly suggested for application in hydrophilic interaction chromatography (HILIC). Both columns (amylose‐silica, 250 × 4.6 mm, 5 μm and cellulose‐silica, 250 × 4.6 mm, 5 μm) demonstrated a satisfactory retention of polar compounds. The influence of the mobile‐phase composition (acetonitrile content, pH, salt concentration) on the retention was in agreement with the HILIC concept. The phases showed a very similar behavior, typical efficiency of about 50 000 plates/m, cellulose retained test compounds somewhat more strongly. Under the experimental conditions, electrostatic (non‐HILIC‐type) interactions due to the dissociation of silanol groups on the silica surface did not influence the retention, noticeably. The applicability of polysaccharide stationary phases for the chromatography of polar compounds was proven by the separation of mixtures of sugars (fructose, glucose, saccharose, maltose, trehalose) or vitamins (nicotinamide, pyridoxine, riboflavin, thiamine, nicotinic acid, ascorbic acid). 相似文献
The title complex, trans‐bis(dimethylformamide‐κO)bis{N,N′‐N′′,N′′′‐tetra‐tert‐butyl[oxybis(phosphonic diamide‐κO)]}manganese(II) dichloride dihydrate, [Mn(C16H40N4O3P2)2(C3H7NO)2]Cl2·2H2O, is the first example of a bis‐chelate amido–pyrophosphate (pyrophosphoramide) complex containing an O[P(O)(NH)2]2 fragment. Its asymmetric unit contains half of the complex dication, one chloride anion and one water molecule. The MnII atom, located on an inversion centre, is octahedrally coordinated, with a slight elongation towards the monodentate dimethylformamide ligand. Structural features of the title complex, such as the P=O bond lengths and the planarity of the chelate ring, are compared with those of previously reported complexes with six‐membered chelates involving the fragments C(O)NHP(O), (X)NP(O) [X = C(O), C(S), S(O)2 and P(O)] and O[P(O)(N)2]2. This analysis shows that the six‐membered chelate rings are less puckered in pyrophosphoramide complexes containing a P(O)OP(O) skeleton, such as the title compound. The extended structure of the title complex involves a linear aggregate mediated by N—H...O and N—H...Cl hydrogen bonds, in which the chloride anion is an acceptor in two additional O—H...Cl hydrogen bonds. 相似文献
The amide bond N?C activation represents a powerful strategy in organic synthesis to functionalize the historically inert amide linkage. This personal account highlights recent remarkable advances in transition‐metal‐free activation of amides by N?C bond cleavage, focusing on both (1) mechanistic aspects of ground‐state‐destabilization of the amide bond enabling formation of tetrahedral intermediates directly from amides with unprecedented selectivity, and (2) synthetic utility of the developed transformations. Direct nucleophilic addition to amides enables a myriad of powerful methods for the formation of C?C, C?N, C?O and C?S bonds, providing a straightforward and more synthetically useful alternative to acyl‐metals. 相似文献
When nanoparticles enter biological environments, proteins adsorb to form the “protein corona” which alters nanoparticle biodistribution and toxicity. Herein, we measure protein corona formation on DNA-functionalized single-walled carbon nanotubes (ssDNA-SWCNTs), a nanoparticle used widely for sensing and delivery, in blood plasma and cerebrospinal fluid. We characterize corona composition by mass spectrometry, revealing high-abundance corona proteins involved in lipid binding, complement activation, and coagulation. We investigate roles of electrostatic and entropic interactions driving selective corona formation. Lastly, we study real-time protein binding on ssDNA-SWCNTs, obtaining agreement between enriched proteins binding strongly and depleted proteins binding marginally, while highlighting cooperative adsorption mechanisms. Knowledge of protein corona composition, formation mechanisms, and dynamics informs nanoparticle translation from in vitro design to in vivo application. 相似文献
Fourteen low molecular mass UV absorbing ampholytes containing 1 or 2 weakly acidic and 1 or 2 weakly basic functional groups that best satisfy Rilbe's requirement for being good carrier ampholytes (ΔpKa = pKamonoanion ‒ pKamonocation < 2) were selected from a large group of commercially readily available ampholytes in a computational study using two software packages (ChemSketch and SPARC). Their electrophoretic mobilities were measured in 10 mM ionic strength BGEs covering the 2 < pH < 12 range. Using our Debye-Hückel and Onsager-Fuoss laws-based new software, AnglerFish (freeware, https://echmet.natur.cuni.cz/software/download ), the effective mobilities were recalculated to zero ionic strength from which the thermodynamic pKa values and limiting ionic mobilities of the ampholytes were directly calculated by Henderson-Hasselbalch equation-type nonlinear regression. The tabulated thermodynamic pKa values and limiting ionic mobilities of these ampholytes (pI markers) facilitate both the overall and the narrow-segment characterization of the pH gradients obtained in IEF in order to mitigate the errors of analyte ampholyte pI assignments caused by the usual (but rarely proven) assumption of pH gradient linearity. These thermodynamic pKa and limiting mobility values also enable the reality-based numeric simulation of the IEF process using, for example, Simul (freeware, https://echmet.natur.cuni.cz/software/download ). 相似文献
Three sets of 7-deazaadenine and cytosine nucleosides and nucleoside triphosphates bearing either unsubstituted ferrocene, octamethylferrocene and ferrocenecarboxamide linked through an alkyne tether to position 7 or 5, respectively, were designed and synthesized. The modified dNFcXTP s were good substrates for KOD XL DNA polymerase in primer extension and were used for enzymatic synthesis of redox-labelled DNA probes. Square-wave voltammetry showed that the octamethylferrocene oxidation potential was shifted to lower values, whilst the ferrocenecarboxamide was shifted to higher potentials, as compared to ferrocene. Tailed PEX products containing different ratios of Fc-labelled A ( dAFc ) and FcPa-labelled C ( dCFcPa ) were synthesized and hybridized with capture oligonucleotides immobilized on gold electrodes to study the electrochemistry of the redox-labelled DNA. Clearly distinguishable, fully orthogonal and ratiometric peaks were observed for the dAFc and dCFcPa bases in DNA, demonstrating their potential for use in redox coding of nucleobases and for the direct electrochemical measurement of the relative ratio of nucleobases in an unknown sequence of DNA. 相似文献