共查询到20条相似文献,搜索用时 15 毫秒
1.
Two polystyrene-based capillary monolithic columns of different length (50 and 250 mm) were used to evaluate the effects of
column length on gradient separation of protein digests. A tryptic digest of a 9-protein mixture was used as a test sample.
Peak capacities were determined from selected extracted ion chromatograms, and tandem mass spectrometry data were used for
database matching using the MASCOT search engine. Peak capacities and protein identification scores were higher for the long
column with all gradients. Peak capacities appear to approach a plateau for longer gradient times; maximum peak capacity was
estimated to be 294 for the short column and 370 for the long column. Analyses with similar gradient slope produced a ratio
of the peak capacities of 3.36 for the long and the short column, which is slightly higher than the expected value of the
square root of the column length ratio. The use of a longer monolith improves peptide separation, as reflected by higher peak
capacity, and also increases protein identification, as observed from higher identification scores and a larger number of
identified peptides. Attention has also been paid to the peak production rate (PPR, peak capacity per unit time). For short
analysis times, the short column produces a higher PPR, while for analysis times longer than 40 min, the PPR of the 250-mm
column is higher. 相似文献
2.
Hollow micron-sized poly(styrene-co-divinylbenzene) particles were produced in seeded emulsions in the presence of swelling solvents. The size and morphology
of the resulting polymer particles can be altered by varying swelling solvent in seeded polymerization at elevated temperature.
The effects of swelling agents, including hydrophobic solvents, hydrophilic solvents and solvent mixtures, on the microstructure
of particles were investigated. The formation of hollow poly(styrene-co-divinylbenzene) particles depended significantly on a fast and effective phase separation between the cross-linked shell
and the swollen core, that occurred only in the presence of an appropriate swelling solvent. 相似文献
3.
Poly(styrene-co-divinylbenzene) microspheres having a diameter range of 3.0–4.5 µm were synthesized by precipitation polymerization under various conditions, then the effects of the polymerization parameters such as monomer and initiator concentration, and used cosolvents on the characteristics of the final particles were compared with those in dispersion polymerization. It was found that precipitation polymerization is more sensitive to polymerization conditions than dispersion polymerization, and that precise control of polymerization parameters is therefore essential for individually stable spherical particles. Monomer and initiator concentration, and the use of cosolvents significantly vary the morphology and the size of the final particles. However, the uniformity of the microspheres is not greatly affected by the polymerization parameters. 相似文献
4.
In order to exploit the biological functions of materials, a series of new random terpolymers were synthesized by the ring-opening polymerization of p-dioxanone, trimethylene carbonate, and L-phenylalanine N-carboxyanhydride (L-Phe- NCA) in the presence of stannous octoate. The terpolymers were characterized by 1H-NMR, 13C-NMR, FTIR, and gel permeation chromatography. The effects of the reactant ratio, catalyst dosage, reaction temperature and time on the copolymerization were investigated, and were found to regulate the composition of the terpolymer. Increases in the reaction temperature, polymerization time, L-Phe-NCA monomer amount, and catalyst content generated a product with a slightly decreased molecular weight. The crystallinity of the terpolymer was investigated by differential scanning calorimetry and polarized optical microscopy. A reasonable mechanism for the polymerization was proposed based on the obtained results. 相似文献
5.
Utilizing the hydrolysis and condensation of the methoxysilyl moieties, organic-inorganic hybrid poly(N-isopropylacrylamide-co-acrylamide-co-3-(trimethoxysilyl)propylmethacrylate) P(NIPAM-co-AM-co-TMSPMA) microgels were prepared via two different methods. The first method was that the microgels were post-fabricated from the crosslinkable linear P(NIPAM-co-AM-co-TMSPMA) terpolymer aqueous solutions above the lower critical solution temperature (LCST) of the terpolymer. For the second
method, the microgels were directly synthesized by conventional surfactant free emulsion copolymerization of NIPAM, AM, and
TMSPMA. The hydrodynamic diameter and stability of the resultant P(NIPAM-co-AM-co-TMSPMA) microgels strongly depend on the pH and temperature of the microgel aqueous solution. The hydrodynamic diameters
of the microgels decreased with increasing the measuring temperature. The phase transition temperature of the microgels was
found to be around 34°C, which was independent of the initial terpolymer concentration and shifted to lower temperature with
increasing the preparation temperature. Increasing the initial amount of AM will enhance the instability of the microgels
at high pH values. Moreover, the P(NIPAM-co-AM-co-TMSPMA) microgels obtained from the linear terpolymer had more homogeneous microstructures as compared with the corresponding
NIPAM/AM/TMSPMA microgels prepared by one step emulsion copolymerization as revealed by light scattering measurements. 相似文献
6.
Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene(St) and ethyleneglycol dimethacrylate(EGDMA,used as a crosslinker) on spherical, linear polystyrene(PS) seed particles.The morphology of the resulting PS/poly(St-co-EGDMA) particles was dependent on the crosslinker concentration and polymerization temperature. 相似文献
7.
P. S. Vijayanand J. Vivekanandan A. Jeeva R. Arun Prasath 《Polymer Science Series B》2016,58(5):580-586
A new series of copolymers of poly(m-toluidine-co-m-aminoacetophenone) were synthesized by the chemical oxidative method in acid medium. The copolymers were characterized by UV–Vis and FTIR spectroscopy. X-ray diffraction analysis revealed the partial crystalline nature of copolymer. The morphological study by SEM analysis indicated that the surface of the copolymer had the granular structure of agglomerated morphology with average particle size of 200 nm. The conductivity of the copolymers ranged from 2 × 10–4 to 3.3 × 10–8 S/cm and the conductivity decreased with the increase of comonomer concentration. The resultant copolymers showed an enhanced solubility and an improved processability when compared with pure polyaniline. 相似文献
8.
Chemical based approach for the synthesis of poly(styrene-co-acrylonitrile)/ZnO nanocomposites with different ZnO nanoparticle content by in situ emulsion polymerization is discussed. A significant increase in the thermal degradation temperature, melting and crystallization temperatures in all nanocomposite is observed. Increasing ZnO loading to polymer matrix enhances the flame retardant ability of polymer matrix with an appreciable increase in thermal degradation temperature of pristine polymer. 相似文献
9.
Ramachandran H Iqbal NM Sipaut CS Abdullah AA 《Applied biochemistry and biotechnology》2011,164(6):867-877
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)] terpolymer was produced using Cupriavidus sp. USMAA2-4 via one-step cultivation process through combination of various carbon sources such as 1,4-butanediol or γ-butyrolactone
with either 1-pentanol, valeric acid, or 1-propanol. Oleic acid was added to increase the biomass production. The composition
of 3HV and 4HB monomers were greatly affected by the concentration of 1,4-butanediol and 1-pentanol. Terpolymers with 3HV
and 4HB molar fractions ranging from 2 to 41 mol.% and 5 to 31 mol.%, respectively, were produced by varying the concentration
of carbon precursors. The thermal and mechanical properties of the terpolymers containing different proportions of the constituent
monomers were characterized using gel permeation chromatography (GPC), DSC, and tensile machine. GPC analysis showed that
the molecular weights (M
w) of the terpolymer produced were within the range of 346 to 1,710 kDa. The monomer compositions of 3HV and 4HB were also
found to have great influences on the thermal and mechanical properties of the terpolymer P(3HB-co-3HV-co-4HB) produced. 相似文献
10.
Previously unknown E isomers of azomethines (Schiff bases) were synthesized from vanillal and vanillin esters by their reaction with cyclohexylamine. 相似文献
11.
O. G. Strukov V. B. Kondrat’ev Z. V. Vlasova V. A. Petrunin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(1):100-105
Conformers of the biologically active compounds CH3P(O)(OR)(SCH2CH2NR 2 ′ ), where (I) R = i-C4H9, R′ = C2H5 and (II) R = C2H5, R′ = i-C3H7, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object. 相似文献
12.
The ring opening polymerization of ε-caprolactone (CL) was initiated by glycol and yttrium tri(2,6-di-tert-butyl-4-methylphenolate)s (Y(OAr)3), preparing dihydroxy-capped poly (ε-caprolactone) (PCL) with controllable molecular weight. 1H NMR and SEC analyses indicate that two kinds of active species and corresponding PCL with different structures exist in
the system. Increasing the ratio of glycol to Y(OAr)3 benefits the formation of monofunctional active species. However, poly(ethylene glycol) (PEG)/Y(OAr)3 system only contains sole bifunctional active species to synthesize copolymer of CL with PEG (poly(CL-b-PEG-b-CL)). Dihydroxycapped PCL as macroinitiator can further initiate the polymerization of 2,2-dimethyltrimethylene carbonate
(DTC). Thus, triblock copolymer of CL with DTC (poly(DTC-b-CL-b-DTC)) has been prepared. 相似文献
13.
14.
Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003
Published online September 25, 2003 相似文献
15.
Wenzhong Ma Jun Zhang Shuangjun Chen Xiaolin Wang 《Colloid and polymer science》2008,286(10):1193-1202
Poly (styrene-co-acrylonitrile) (SAN) is a hydrophilic non-crystalline copolymer, which is initially used in this paper to improve the hydrophilicity
of poly (vinylidene fluoride) (PVDF). Investigation of the crystallization behavior of PVDF/SAN blends showed that the samples
presented only α phase regardless of SAN content as cooling from the melt. A double-melting phenomenon was related to the
perfection or crystal size of PVDF crystals. As the SAN content is increasing, crystallization of PVDF was limited, leading
to a decreased crystallinity and lamellar growth. Besides, the hydrophilicity of PVDF was improved by blending with SAN. The
sample containing 70 wt.% SAN performed a similar surface property of the neat SAN owing to the besieging of the PVDF phase
by SAN. Observed from the cross section of the blends, PVDF/SAN blends were partially miscible with less than 50 wt.% SAN
addition. As the SAN content was more than 50 wt.%, the crystalline PVDF particles clearly dispersed in the amorphous matrix. 相似文献
16.
Swelling behaviour of poly(N-vinylcaprolactam) (PVC) and poly(N-vinylcaprolactam-co-itaconic acid) (P(VC-co-IA)) gels was investigated in different solvents (water, ethanol, methanol, isopropyl alcohol (IPA), chloroform, toluene, acetone) and in binary solvent mixtures (ethanol/chloroform, ethanol/methanol, IPA/chloroform, ethanol/water, IPA/water). Gels were synthesised in ethanol by the free radical cross-linking polymerisation method at 60°C for 24 h in the presence of azo-bis(isobutyronitrile) and allyl methacrylate as the initiator and cross-linker, respectively. And also, ethanol/distilled water mixture (?r = 4:1) was used as the synthesis medium to determine its effect on the swelling of gels. It was found that the presence of water in the synthesis medium significantly affected the equilibrium swelling value (ESV) and the swelling tendency of gels both in solvents and in solvent mixtures. All gels synthesised in ethanol showed the highest swelling in chloroform. The gels synthesised in the ethanol/water mixture displayed different swelling behaviour. In this case, while chloroform was still valid for maximum swelling of PVC, P(VC-co-IA) had the highest swelling in methanol. Solubility parameters of gels were predicted by the van Krevelen-Hoftyzer (VKH) and Hoy methods (group contribution methods) and theoretical calculations verified the experimental swelling order. 相似文献
17.
K. N. Smirnov I. A. Dyatchkov A. V. Pirogov O. A. Shpigun 《Moscow University Chemistry Bulletin》2011,66(6):351-355
Monolithic columns based on copolymer of divinylbenzene (DVB), ethylvinylbenzene (EVB), and 2-hydroxyethyl methacrylate (HEMA)
were prepared and applied to the separation of low-molecular-weight aromatic compounds. The monoliths were synthesized via
thermally initiated free-radical polymerization in confines of stainless steel tubes with dimensions of 100 × 4.3 mm. In order
to compensate for the polymer shrinkage during the synthesis and prevent the monolith from detachment from the column wall,
the polymerization was conducted under nitrogen pressure. The excess pressure was varied from 0 bar to 9 bar. The synthesis
under pressure was shown to improve the peak shapes and column efficiency in comparison with the synthesis in the closed tube.
The optimum pressure for poly(DVB-co-EVB-co-HEMA) monoliths was found to be 3 bar. The efficiency of the column obtained at 3 bar is 13 500 TP/m for propylbenzene (k′ = 6) and 38 300 TP/m for uracil (k′ = 0). 相似文献
18.
T. F. Ibragimov M. G. Levkovich V. A. Saprykina Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2010,46(5):767-770
N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The
point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated. 相似文献
19.
Taís Vanessa Gabbay Alves Eraldo José Madureira Tavares Fauze Ahmad Aouada Charles Alberto Brito Negrão Marcos Enê Chaves Oliveira Anivaldo Pereira Duarte Júnior Carlos Emmerson Ferreira da Costa José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2011,106(3):717-724
This paper reports the thermal characterization of polyacrylamide-co-methylcellulose hydrogels and the constituent monomers (acrylamide and methylcellulose). Polymeric materials can be used
to produce hydrogels, which can be natural, synthetic, or a mixture. The hydrogels described here were obtained by free radical
polymerization, in the presence of N,N′-methylene-bis-acrylamide as a cross-linker agent. Four acrylamide concentrations were used for the synthesis of hydrogels:
3.6, 7.2, 14.7, and 21.7% (w/v). The materials so obtained were analyzed by TG, DTG, DSC, and FT-IR. The TG curves of acrylamide
and methylcellulose showed three mass loss events. In DSC curves, the acrylamide exhibited one melting peak at 84.5 °C, and
methylcellulose indicated one exothermic event. Nevertheless, acrylamide was considered more stable than methylcellulose.
The TG curves of the hydrogels exhibited three mass loss events, and on the DSC curves, three endothermic events were observed.
It was verified that the different acrylamide proportions influenced the thermic behavior of hydrogels, and that the authors
considered the 7.2% hydrogel a promising drug carrier system. The absorption bands were well defined, confirming the presence
of the functional groups in the samples. 相似文献
20.
Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield. 相似文献