The application of amine-terminated silicon quantum dots on the imaging of human serum proteins after polyacrylamide gel electrophoresis (PAGE)

Novel amine-terminated silicon (Si) quantum dots (QDs) were synthesized and applied for the detection of human serum proteins on gels directly after polyacrylamide gel electrophoresis (PAGE). The diameter of these stable amine-terminated Si?QDs was in the range of 0.5-2.0 nm. In this study, the fluorescent imaging conditions, such as the buffer solution, pH value, buffer concentration and quantity of Si?QDs, were optimized and the possible mechanisms of Si?QDs-protein interaction were analyzed. The mode of Si?QDs and human serum albumin association was found to occur by hydrogen bond interactions; this was probably attributed to the interaction between the amino group of amine-terminated Si?QDs and the carboxyl group of proteins. Meanwhile, human serum proteins separated by native 1D and native 2D electrophoresis were detected by Si QD-based fluorescent imaging. Some proteins, such as isoform 1 of α-1-antitrypsin, complement C3 (Fragment) and hemopexin, which were identified by mass spectrometry (MS), were easily detected by using Si?QDs, but not with CBB-R250 staining. The Si?QDs-based fluorescent imaging technique with high resolution is a sensitive and dependable method for direct detection of human serum proteins, and has enormous potential in clinical diagnosis.     

Capillary zone electrophoresis of rigid submicron-sized particles in polyacrylamide. Solution selectivity, peak spreading and resolution.

Submicron-sized rigid particles can be separated in a size-dependent fashion by electrophoresis in free solution. Yet it has remained unknown whether the presence of polymers in the solution confers an advantage in size-dependent separation of submicron particles and their resolution. The present study addresses that question, using capillary zone electrophoresis of carboxylate modified polystyrene latex microspheres of 55, 140 and 215 nm radius in solutions of linear polyacrylamide in the M(r) range of 0.4.10(6) to 1.14.10(6). Selectivity of particle separation increases in direct relation to the polymer concentration in the concentration range of 0 to 1% (w/v). Selectivity was found to increase with M(r) of the polymer for the particle sets of 55/140 (nm/nm) and 140/215 (nm/nm) but to decrease with polymer M(r) for the 55/215 (nm/nm) set. Peak spreading is a complex and, in the case of the largest particle, non-monotonic function of polymer concentration, with a minimum at concentrations around the entanglement threshold, c*. Consequently, resolution of the 55/215 and 140/215 (nm/nm) sets also exhibits a maximum around the entanglement threshold while resolution for the 55/140 (nm/nm) set increases with a rise of polymer concentrations above c*. Within the range of optimally resolving polymer concentrations there also occurs a maximum of resolution for all particle sets at a field strength in the range of 150 to 250 V cm-1.     

The Application of Amine‐Terminated Silicon Quantum Dots on the Imaging of Human Serum Proteins after Polyacrylamide Gel Electrophoresis (PAGE)

Novel amine‐terminated silicon (Si) quantum dots (QDs) were synthesized and applied for the detection of human serum proteins on gels directly after polyacrylamide gel electrophoresis (PAGE). The diameter of these stable amine‐terminated Si QDs was in the range of 0.5–2.0 nm. In this study, the fluorescent imaging conditions, such as the buffer solution, pH value, buffer concentration and quantity of Si QDs, were optimized and the possible mechanisms of Si QDs–protein interaction were analyzed. The mode of Si QDs and human serum albumin association was found to occur by hydrogen bond interactions; this was probably attributed to the interaction between the amino group of amine‐terminated Si QDs and the carboxyl group of proteins. Meanwhile, human serum proteins separated by native 1D and native 2D electrophoresis were detected by Si QD‐based fluorescent imaging. Some proteins, such as isoform 1 of α‐1‐antitrypsin, complement C3 (Fragment) and hemopexin, which were identified by mass spectrometry (MS), were easily detected by using Si QDs, but not with CBB‐R250 staining. The Si QDs‐based fluorescent imaging technique with high resolution is a sensitive and dependable method for direct detection of human serum proteins, and has enormous potential in clinical diagnosis.     

Gel electrophoresis of polystyrene particles in glutaraldehyde crosslinked polyvinyl alcohol

Polystyrene sulfate and carboxylate particles (19-189 nm radius) were subjected to electrophoresis in glutaraldehyde crosslinked polyvinyl alcohol of molecular weight 25.000 and 650.000 Da at various concentrations. The degree of crosslinking is severely limited by the mechanical properties of the gels that deteriorate beyond a glutaraldehyde concentration which decreases with increasing polyvinyl alcohol chain length. The effective fiber radius of the short-chain and long-chain polymer fiber was 45 +/- 25 and 131 +/- 47 nm, respectively. Thus, these media do not significantly exceed the apparent fiber thickness of agarose, are more difficult to prepare--but are well-defined synthetic products rather than natural ones, and have the advantage of carrying no net charge and can therefore be expected to exhibit no electroendosmosis.     

Adhesion forces between hybrid colloidal particles and concanavalin A

Hybrid particles of poly(methyl methacrylate) and carboxymethylcellulose, PMMA/CMC, were attached to atomic force microscopy cantilevers and probed against concanavalin A (ConA) films formed either on Si wafers or on CMC substrate. Regardless of the substrate, the approach curves showed different inclinations, indicating that the probe first touches a soft surface and then a hard substrate. The distance corresponding to the soft layer was estimated as 20 +/- 10 nm and was attributed to the CMC layers attached to the hybrid particles surfaces. Probing PMMA/CMC particles against ConA adsorbed onto Si wafers yielded retract curves with a sawlike pattern. The average range of adhesion forces (maximum pull-off distance) and mean adhesion force were estimated as 100 +/- 40 nm and -11 +/- 7 nN, respectively, evidencing multiple adhesions between CMC sugar residues and ConA. However, upon probing against ConA adsorbed onto CMC substrates, the mean pull-off distance and mean adhesion force were reduced to 37 +/- 18 nm and -3 +/- 1 nN, respectively, indicating that the ConA molecules immobilized onto CMC films are less available to interact with the hybrid particle than the ConA molecules adsorbed onto Si wafers. Another set of experiments, where PMMA/CMC particle probed against ConA-covered Si wafers in the presence of mannose, showed that the addition of mannose led to a considerable decrease in the mean adhesion force from -11 +/- 7 to -3 +/- 1 nN. Two hypotheses have been considered to explain the effect caused by mannose addition. The first suggested the desorption of ConA from the substrate so that the hybrid particle would probe bare Si wafer (weak adhesion). The second proposed the adsorption of mannose onto the ConA layer so that mannose layer would probe against another mannose layer, leading to low adhesion forces. In situ ellipsometry and capillary electrophoresis have been applied to check the hypotheses.     

Infrared investigation of the silicon oxide phase in [perfluoro-carboxylate/sulfonate (bilayer)]/[silicon oxide] nanocomposite membranes

[Perfluoro-organic]/[silicon oxide] hybrids were formed by conducting sol-gel reactions of tetraethylorthosilicate within a perfluoro(carboxylate/sulfonate) bilayer membrane in the Co⁺² form. FTIR and ²⁹Si solid-state NMR spectroscopies were used to probe general aspects of molecular structure within the silicon oxide phase as a function of its relative content. The internal gel structure is considerably unconnected in terms of the population of Si O Si groups in cyclic vs. linear substructures and degree of Si atom coordination about bonded SiO₄ units. In situ (HO)_xSiO_2[1-1/4x] intrastructure become increasingly less connected and more strained with regard to bonding geometry with increasing percent silicon oxide. Structural differences are seen between the silicon oxide component incorporated in carboxylate and sulfonate layers. These inorganically modified perfluorinated ionomers have potential as fast-proton conducting membranes for fuel cells and as permselective membranes in liquid pervaporation cells. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 595–606, 1998     

Synthesis and spectroscopic studies of non-heme diiron(III) species with a terminal hydroperoxide ligand: models for hemerythrin

Two compounds, [Fe2(mu-OH)(mu-Ph4DBA)(TMEDA)2(OTf)] (4) and [Fe2(mu-OH)(mu-Ph4DBA)(DPE)2(OTf)] (7), where Ph4DBA(2-) is the dinucleating bis(carboxylate) ligand dibenzofuran-4,6-bis(diphenylacetate), have been prepared as synthetic models for the dioxygen-binding non-heme diiron protein hemerythrin (Hr). X-ray crystallography reveals that, in the solid state, these compounds contain the asymmetric coordination environment found at the diiron center in the reduced form of the protein, deoxyHr. M?ssbauer spectra of the models (4, delta = 1.21(2), DeltaE(Q) = 2.87(2) mm s(-1); 7, delta(av) = 1.23(1), DeltaE(Qav) = 2.79(1) mm s(-1)) and deoxyHr (delta = 1.19, DeltaE(Q) = 2.81 mm s(-1)) are also in good agreement. Oxygenation of the diiron(II) complexes dissolved in CH2Cl2 containing 3 equiv of N-MeIm (4) or neat EtCN (7) at -78 degrees C affords a red-orange solution with optical bands at 336 nm (7300 M(-1) cm(-1)) and 470 nm (2600 M(-1) cm(-1)) for 4 and at 334 nm (6400 M(-1) cm(-1)) and 484 nm (2350 M(-1) cm(-1)) for 7. These spectra are remarkably similar to that of oxyHr, 330 nm (6800 M(-1) cm(-1)) and 500 nm (2200 M(-1) cm(-1)). The electron paramagnetic resonance (EPR) spectrum of the cryoreduced, mixed-valence dioxygen adduct of 7 displays properties consistent with a (mu-oxo)diiron(II,III) core. An investigation of 7 and its dioxygen-bound adduct by extended X-ray absorption fine structure (EXAFS) spectroscopy indicates that the oxidized species contains a (mu-oxo)diiron(III) core with iron-ligand distances in agreement with those expected for oxide, carboxylate, and amine/hydroperoxide donor atoms. The analogous cobalt complex [Co2(mu-OH)(mu-Ph4DBA)(TMEDA)2(OTf)] (6) was synthesized and structurally characterized, but it was unreactive toward dioxygen.     

Bilayer vesicles of amphiphilic cyclodextrins: host membranes that recognize guest molecules

A family of amphiphilic cyclodextrins (6, 7) has been prepared through 6-S-alkylation (alkyl=n-dodecyl and n-hexadecyl) of the primary side and 2-O-PEGylation of the secondary side of alpha-, beta-, and gamma-cyclodextrins (PEG=poly(ethylene glycol)). These cyclodextrins form nonionic bilayer vesicles in aqueous solution. The bilayer vesicles were characterized by transmission electron microscopy, dynamic light scattering, dye encapsulation, and capillary electrophoresis. The molecular packing of the amphiphilic cyclodextrins was investigated by using small-angle X-ray diffraction of bilayers deposited on glass and pressure-area isotherms obtained from Langmuir monolayers on the air-water interface. The bilayer thickness is dependent on the chain length, whereas the average molecular surface area scales with the cyclodextrin ring size. The alkyl chains of the cyclodextrins in the bilayer are deeply interdigitated. Molecular recognition of a hydrophobic anion (adamantane carboxylate) by the cyclodextrin vesicles was investigated by using capillary electrophoresis, thereby exploiting the increase in electrophoretic mobility that occurs when the hydrophobic anions bind to the nonionic cyclodextrin vesicles. It was found that in spite of the presence of oligo(ethylene glycol) substituents, the beta-cyclodextrin vesicles retain their characteristic affinity for adamantane carboxylate (association constant K(a)=7.1 x 10(3) M(-1)), whereas gamma-cyclodextrin vesicles have less affinity (K(a)=3.2 x 10(3) M(-1)), and alpha-cyclodextrin or non-cyclodextrin, nonionic vesicles have very little affinity (K(a) approximately 100 M(-1)). Specific binding of the adamantane carboxylate to beta-cyclodextrin vesicles was also evident in competition experiments with beta-cyclodextrin in solution. Hence, the cyclodextrin vesicles can function as host bilayer membranes that recognize small guest molecules by specific noncovalent interaction.     

毛细管区带电泳法研究新型喜树碱衍生物的水解反应

采用毛细管区带电泳法考察新型喜树碱衍生物(L-P)在不同pH溶液中的结构稳定性,并在接近人体生理条件下(310 K, pH 7.4)研究由内酯环结构形式向羧酸盐结构形式转化的水解反应的动力学和热力学参数.采用未涂层熔融石英毛细管柱(35 cm×50 μm i.d.,有效柱长26.5 cm),背景电解质溶液(BGE)为0 025 mol/L磷酸钠缓冲溶液,pH 值分别为2.5, 4.0, 5.0, 6.0, 7.0, 7.4和9.0.在pH＜4的溶液中,L-P以内酯环结构形式存在;随着pH值增大,内酯环结构形式将逐渐水解转化成羧酸盐结构形式;当pH>9时,L-P几乎完全以羧酸盐结构形式存在.上述水解反应的速率常数随温度的升高而增加;测得其活化能 (Ea),焓变(ΔH)和熵变(ΔS)分别为72.6 kJ/mol,10.5 kJ/mol和50.9 J/(mol · K).毛细管区带电泳法能有效分离新型喜树碱衍生物(L-P)两种具有pH依赖性的结构形式.由内酯环结构形式向羧酸盐结构形式转化的水解反应是一个自发的吸热过程, 而且随着温度的升高其水解反应趋势相应加大.     

一维链状配位聚合物[Pb_2(C_8H_7O_2)_4(H_2O)_2]_n的合成、晶体结构及荧光性质

<正>近年来,铅的配位聚合物以其丰富的结构与在离子交换和光学等领域中的应用前景[1-3]而引起了广泛关注。由于铅的原子半径较大,可以形成较高的配位数[4-6];另外,二价铅的6s轨道上有一对孤对     

Photochemical cleavage and release of carboxylic acids from alpha-keto amides

In aqueous media, alpha-keto amides LGCH(2)COCON(R)CH(R')CH(3) (1a, R = Et, R' = H; 1b, R = (i)()Pr, R' = Me; 1c, R = Ph, R' = H) with various carboxylate leaving groups (LG) at the C-3 position undergo photocleavage and release of carboxylic acids with formation of diastereomeric 5-hydroxyoxazolidin-4-ones 2a,c in the cases of 1a,c or 5-methyleneoxazolidin-4-ones 3b in the case of 1b. For 1a,b, Phi(photocleavage) = 0.24-0.38, whereas Phi(photocleavage) = ca. 0.05 for 1c. The proposed mechanism involves transfer of hydrogen from an N-alkyl group to the keto oxygen to produce zwitterionic intermediates 4a-c that eliminate carboxylate anions. The resultant imminium ions, H(2)C=C(OH)CON(+)(R)=C(R')CH(3) 5a-c, cyclize intramolecularly to 3b or undergo intermolecular addition of water followed by tautomerization and cyclization to give 2a,c. These inter- or intramolecular trapping reactions of 5 release protons that decrease the pH and cause bleaching of the 620 nm band of the pH indicator, bromocresol green. Determination of the bleaching kinetics by laser flash photolysis methods in the case of 1a gives time constants of 18-137 mus, depending on the leaving group ability of the carboxylate anion, whereas amides 1b show only a small leaving group effect. For 1a, the large leaving group effect is consistent with rate-limiting carboxylate elimination from 4a, whereas the proton release step would be largely rate determining for 1b. Photolyses of 1a (LG = CH(3)CO(2)(-), PhCH(2)CO(2)(-)) in neat CH(3)CN results in carboxylate elimination to form imminium ion 5a, followed by internal return to give aminals.     

In situ generation of the silica shell layer--key factor to the simple high yield synthesis of silver nanowires

a-Silica encapsulated silver nanowires (diameter of 25 +/- 5 nm, average length of 10 mum) have been synthesized by reacting (Me3Si)4Si with AgNO3 in nearly quantitative yield. Formation of the a-silica shell layer (1-3 nm) in situ appears to be one of the most important factors in this simple process.     

Synthesis, characterization, and growth rates of germanium silicalite-1 grown from clear solutions

The synthesis, characterization, and growth of Ge-silicalite-1 from optically clear solutions are reported. Ge-silicalite-1 is readily formed from optically clear solutions of TEOS, TPAOH, water, and a germanium source at 368 K. X-ray fluorescence (XRF) is used to determine the Si/Ge ratio and indicates that germanium inclusion is typically 30-50% of that in the actual mixture. Adsorption, power X-ray diffraction (PXRD), and 29Si NMR indicate the materials are crystalline and microporous. In situ small-angle X-ray scattering (SAXS) is applied to investigate the influences of germanium source (GeO2 and Ge(OC2H5)4) and content (Si/Ge 100:5) on the growth of Ge-silicalite-1 from clear solutions at 368 K. The in situ SAXS investigations show that for solutions with Si/Ge ratios of 100, 50, and 25 using Ge(OC2H5)4 the induction periods are approximately 6 h and the particle growth rates are 1.82 +/- 0.04, 2.52 +/- 0.13, and 2.85 +/- 0.08 nm/h, respectively, at 368 K, compared to those of pure silicalite-1 (6 h induction period, 1.93 +/- 0.1 nm/h growth rate). Further increasing the Si/Ge ratio to 15 and 5 shortens the induction period to approximately 4.5 h, and the growth rates are 3.07 +/- 0.16 and 2.05 +/- 0.10 nm/h, respectively, indicating the Si/Ge ratio that maximizes Ge-silicalite-1 growth is between 25 and 15. Similar trends are obtained with germanium oxide; however, the growth rates are all consistently larger than those for syntheses with Ge(OC2H5)4. The results indicate that Ge-silicalite-1 growth rates in the presence of germanium are increased as compared to those of pure-silica syntheses.     

Binding of glycine and L-cysteine on Si(111)-7 x 7

The adsorption of glycine and l-cysteine on Si(111)-7 x 7 was investigated using high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). The observation of the characteristic vibrational modes and electronic structures of NH3+ and COO- groups for physisorbed glycine (l-cysteine) demonstrates the formation of zwitterionic species in multilayers. For chemisorbed molecules, the appearance of nu(Si-H), nu(Si-O), and nu(C=Omicron) and the absence of nu(O-H) clearly indicate that glycine and l-cysteine dissociate to produce monodentate carboxylate adducts on Si(111)-7 x 7. XPS results further verified the coexistence of two chemisorption states for each amino acid, corresponding to a Si-NH-CH2-COO-Si [Si-NHCH(CH2SH)COO-Si] species with new sigma-linkages of Si-N and Si-O, and a NH2-CH2-COO-Si [NH2CH(CH2SH)COO-Si] product through the cleavage of the O-H bond, respectively. Glycine/Si(111)-7 x 7 and l-cysteine/Si(111)-7 x 7 can be viewed as model systems for further modification of Si surfaces with biological molecules.     

在蒸气相中合成中孔分子筛MCM—41及其孔结构参数的表征

在水蒸气中，由含表面活性剂十六烷基三甲基溴化铵的无定形凝胶合成出Ｓｉ－ＭＣＭ－４１和Ａｌ－Ｓｉ－ＭＣＭ－４１分子筛纯相，研究了它们的合成条件。     

三苯基锡-2-(1, 2-亚乙二硫)亚甲基-3-羰基-5-芳基-4-戊烯酸 酯的合成及晶体 结构

由2-(1,2-亚乙二硫)亚甲基-3-羰基-5-芳基-4-戊烯酸与三苯基氢氧化锡反应,合成了九个标题化合物3。用X射线衍射法测定了3b的晶体结构。该晶体属三斜晶系,空间群P1,a=0.9074(2)nm,b=1.6809(3)nm,c=2.1834(4)nm,α=77.57(3)ⅲ,β=88.04(3)ⅲ,γ=89.47(3)ⅲ,V=3.2503nm^3,Z=2;R=0.0592。由锡氧原子间距离可推测,该晶体中羧酸根作为双齿配体与锡原子形成了分子内五配位结构。     

New water-soluble polyanionic dendrimers and binding to acetylcholine in water by means of contact ion-pairing interactions

A new water-soluble polyanionic dendrimer containing 81 benzoate termini (diameter: 11+/-1 nm from DOSY NMR spectroscopy) has been synthesized; it interacts with acetylcholine cations in water-soluble assemblies in which each carboxylate terminus reversibly forms contact ion pairs and aggregates at the tether termini, as shown by 1H NMR spectroscopy.     

Facile fabrication of 2-dimensional arrays of sub-10 nm single crystalline Si nanopillars using nanoparticle masks

A simple procedure for the fabrication of sub-10 nm scale Si nanopillars in a 2-D array using reactive ion etching with 8 nm Co nanoparticles as etch masks is demonstrated. The obtained Si nanopillars are single crystalline tapered pillar structures of 5 nm (top) x 8 nm (bottom) with a density of approximately 4 x 10(10) pillars cm(-2) on the substrate, similar to the density of Co nanoparticles distributed before the ion etching process. The uniform spatial distribution of the Si nanopillars can also be patterned into desired positions. Our fabrication method is straightforward and requires mild process conditions, which can be extended to patterned 2-D arrays of various Si nanostructures.     

熔盐法合成新型硅酸铀K6(UO2)3Si8O22

用熔盐法合成了新型硅酸铀K4(UO2),Si8O22,并用单晶X射线衍射确定结构.结果表明,化合物由UO6 双四角椎及硅酸根四面体构成的(Si8O22)12-单元组成,其中(Si8O22)12-单元的结构形态是最新发现的.29Si MAS NMR测定结果与晶体结构相吻合,而光致发光光谱证实了六价铀的存在.K(UO2),...     

Controlled growth of Zn nano-dots on a Si(111)-7x7 surface saturated with C2H5OH

Metal atoms bonded with Si adatoms on the Si(111)-(7x7) surface undergo migration by hopping adjacent Si-rest atoms with dangling bond. By saturated adsorption of Si(111)-(7x7) surface with C(2)H(5)OH, the whole Si-rest atoms and a half of Si adatoms are occupied with Si-H and Si-OC(2)H(5), so that the Zn atoms adsorbed on this surface cannot migrate by hopping. When Zn atoms were deposited on this surface, ca. 5 nm Zn dots were grown in the hexagonal spacing of ca. 5.4 nm width around the corner holes, which work as a mold. This is quite different from the growth of honeycomb layers composed of Zn(3) clusters on the clean Si(111)-(7x7) surface. The dots grow up to nine (1.97 nm) to 13 layers (2.64 nm) by keeping their size, which implies a layer-by-layer growth of dots in the mold, where the growth is controlled by the kinetics instead of energetic feasibility.