Electron beam triggered, free radical polymerization-derived monolithic capillary columns for high-performance liquid chromatography

Monolithic capillary columns were prepared via electron beam triggered free radical polymerization within the confines of 0.2 and 0.1mm I.D. capillary columns using ethyl methacrylate and trimethylolpropane triacrylate as monomers as well as 2-propanol, 1-dodecanol and toluene as porogenic system. The influence of column diameter on reproducibility and separation performance was investigated. For evaluation, a protein standard consisting of five proteins in the range of 5800-66,000 g mol(-1) was used. Reproducibility was checked by determining the relative standard deviations in retention times, peak widths at half height, asymmetry and resolution. Excellent run-to-run reproducibility was found for both 0.2 and 0.1mm I.D. columns; batch-to-batch reproducibility was good for both column types. In order to enhance the non-polar character of the monolithic columns, lauryl methacrylate-based capillary columns were prepared. These were successfully used for the separation of proteins and a cytochrome c digest.     

Synthesis, crystal structure and properties of cobalt(II) and nickel(II) coordination polymers supported by functionalized dicarboxylate ligands

Four new coordination polymers of cobalt(II) and nickel(II) with functionalized dicarboxylate ligands, namely, [Co^IIL¹(2,2′-bpy)(H₂O)] (1), [Ni^IIL¹(2,2′-bpy)(H₂O)]·H₂O (2), [Co^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (3) and [Ni^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (4), where H₂L¹ = 2,5-dibenzoylterephthalic acid, H₂L² = 4,6-bis(4-methylbenzoyl)isophthalic acid and 2,2′-bpy = 2,2′-bipyridine, were synthesized and characterized by elemental analysis, IR spectra and thermogravimetric analysis. Complex 1 exhibits a zigzag chain with a C–Hπ interaction between the phenyl ring proton and the phenyl ring of an adjacent chains to form a 2D supramolecular sheet. Complex 2 contains two helical chains which extend into 2D via a C–Hπ interaction between the pyridine ring proton and the pyridine ring. Complexes 3 and 4 are isomorphous with helical chains that extend in the same direction and further link to one another by supramolecular forces into a 2D structure. Moreover, magnetic and luminescence properties have been investigated for 1 and 2, respectively.     

Remarkably selective saccharide recognition by solid-supported peptide boronic acids

The affinity of nine different saccharides to a library of solid-supported pentapeptide diboronic acids was measured using a competitive binding assay, which employed alizarin as the chromophoric indicator. Considerable variation in carbohydrate binding strengths was observed, with association constants in the range 60-5300 M⁻¹ being recorded. Of particular note was the 7-fold preference for CMP over AMP shown by peptide 1. Enantioselectivity was also observed, with peptide 4 showing an 8.4-fold binding preference for l-glucose over d-glucose. The remarkably selective binding characteristics of these boronic acid-peptide hybrids suggest their potential use in carbohydrate sensors and cell-specific diagnostics and therapeutics.     

Improved analyte detectability of proteins and peptide lysates by means of multiple large‐volume injection in LC‐MS

A ‘multiple (trapping) large‐volume injection’ approach was developed for the analysis of peptides and proteins. In this way, a maximally 10‐fold gain in sensitivity could be achieved. The system involves the use of an automated 10‐port switching valve in combination with a 1 mm i.d. trapping/guard column and a 1 mm i.d.×150 mm analytical column. The optimized multiple injection/loading procedure allows quantitative measurements of peptides and protein lysates. Linear calibration curves (R² ? 0.988) over a minimum of two orders of magnitude were generated for a range of peptide and protein standards with sensitivities equal to or even exceeding, those generally achieved only through increasing miniaturization (quantification limit ?0.5 pmol/mL).     

Characterizing ion mobility-mass spectrometry conformation space for the analysis of complex biological samples

The conformation space occupied by different classes of biomolecules measured by ion mobility-mass spectrometry (IM-MS) is described for utility in the characterization of complex biological samples. Although the qualitative separation of different classes of biomolecules on the basis of structure or collision cross section is known, there is relatively little quantitative cross-section information available for species apart from peptides. In this report, collision cross sections are measured for a large suite of biologically salient species, including oligonucleotides (n = 96), carbohydrates (n = 192), and lipids (n = 53), which are compared to reported values for peptides (n = 610). In general, signals for each class are highly correlated, and at a given mass, these correlations result in predicted collision cross sections that increase in the order oligonucleotides < carbohydrates < peptides < lipids. The specific correlations are described by logarithmic regressions, which best approximate the theoretical trend of increasing collision cross section as a function of increasing mass. A statistical treatment of the signals observed within each molecular class suggests that the breadth of conformation space occupied by each class increases in the order lipids < oligonucleotides < peptides < carbohydrates. The utility of conformation space analysis in the direct analysis of complex biological samples is described, both in the context of qualitative molecular class identification and in fine structure examination within a class. The latter is demonstrated in IM-MS separations of isobaric oligonucleotides, which are interpreted by molecular dynamics simulations. Figure Potential for performing simultaneous “omics” through the separation of biomolecular classes on the basis of structure and mass using ion mobility-mass spectrometry Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

HPLC-CHIP coupled to a triple quadrupole mass spectrometer for carbonic anhydrase II quantification in human serum

A method for carbonic anhydrase II (CA II) absolute quantification in human serum is presented. This method is based on high-performance liquid chromatography (HPLC)-Chip microfluidic device incorporating a nanoelectrospray source interfaced to a triple quadrupole mass spectrometer. The fraction containing CA II was isolated by preparative reversed-phase HPLC, and peptides obtained from the tryptic digest of the protein mixture were separated by the HPLC-Chip system. The multiple-reaction monitoring acquisition mode of a selected suitable CA II peptide and peptide internal standard allowed the selective and sensitive determination of a CA II. Absolute recovery of the method was 52 ± 12%, while analytical recovery was 81 ± 10%. For the eight samples analyzed, the matrix effect was found to be only −14 ± 6%. A comparison among three regression lines type which were obtained by external calibration, matrix-matched calibration, and standard addition method, respectively, demonstrated that the first one is adequate in obtaining good accuracy and precision. Method quantification limit for CA II in serum was estimated to be 2 fmol/mL. CA II mean concentration in sera from eight healthy subjects was found to be 56 pmol/mL (relative standard deviation 24%).     

Preparation of the β2‐Homoselenocysteine Derivatives Fmoc‐(S)‐β2hSec(PMB)‐OH and Boc‐(S)‐β2hSec(PMB)‐OH for Solution and Solid‐Phase Peptide Synthesis

Fmoc‐β²hSer(^tBu)‐OH was converted to Fmoc‐β²hSec(PMB)‐OH in five steps. To avoid elimination of HSeR, the selenyl group was introduced in the second last step (Fmoc‐β²hSer(Ts)‐OAll→Fmoc‐β²hSec(PMB)‐OAll). In a similar way, the N‐Boc‐protected compound was prepared. With the β²hSe‐derivatives, 21 β²‐amino‐acid building blocks with proteinogenic side chains are now available for peptide synthesis.     

以聚乳酸为侧链的光学活性聚苯乙炔的合成与表征

通过4-溴苯甲醇和三甲基硅基乙炔的Sonagashira偶联反应与三甲基硅基的脱除反应,合成4-乙炔基苯甲醇.以4-乙炔基苯甲醇为引发剂,以有机氮杂环化合物DBU为催化剂,常温常压下进行丙交酯的活性开环聚合反应,采用1H-NMR和GPC对产物结构、分子量与分子量分布进行表征分析,结果表明,合成以了苯乙炔为端基的聚乳酸大...     

Surface-modified TiO(2) nanoparticles as affinity probes and as matrices for the rapid analysis of phosphopeptides and proteins in MALDI-TOF-MS

We utilized three different types of TiO₂ nanoparticles (NPs) namely TiO₂‐dopamine, TiO₂‐CdS and bare TiO₂ NPs as multifunctional nanoprobes for the rapid enrichment of phosphopeptides from tryptic digests of α‐ and β‐casein, milk and egg white using a simplified procedure in MALDI‐TOF‐MS. Surface‐modified TiO₂ NPs serve as effective matrices for the analysis of peptides (gramicidin D, HW6, leucine‐enkephalin and methionine‐enkephalin) and proteins (cytochrome c and myoglobin) in MALDI‐TOF‐MS. In the surface‐modified TiO₂ NPs‐based MALDI mass spectra of these analytes (phosphopetides, peptides and proteins), we found that TiO₂‐dopamine and bare TiO₂ NPs provided an efficient platform for the selective and rapid enrichment of phosphopeptides and TiO₂‐CdS NPs efficiently acted as the matrix for background‐free detection of peptides and proteins with improved resolution in MALDI‐MS. We found that the upper detectable mass range is 17 000 Da using TiO₂‐CdS NPs as the matrix. The approach is simple and straightforward for the rapid analysis of phosphopeptides, peptides and proteins by MALDI‐MS in proteome research.     

Size-exclusion separation of proteins using a biocompatible polymeric monolithic capillary column with mesoporosity

Biocompatible poly(ethylene glycol methyl ether acrylate-co-polyethylene glycol diacrylate) monoliths were prepared for size exclusion chromatography (SEC) of proteins in the capillary format using Brij 58P in a mixture of hexanes and dodecanol as porogens. The monolithic columns provided size separation of four proteins in 20 mM sodium phosphate buffer (pH 7.0) containing 0.15 M NaCl, and there was a linear relationship between the retention times and the logarithmic values of the molecular weights. Compared to SEC monoliths previously synthesized using a triblock copolymer of polyethylene oxide and polypropylene oxide, an increase in mesoporosity was confirmed by inverse size exclusion chromatography. As a result, improved protein separation in the high molecular weight range and reduced column back-pressure were observed.