The stereoregular synthetic polymer isotactic polystyrene bearing partially sulfonated groups (SiPS) was used as a layer-by-layer assembled thin film for the first time. When a low molecular weight compound was employed as the pair for the alternative layer-by-layer (LbL) assembly, the frequency shift was very small using quartz crystal microbalance (QCM) analysis, whereas poly(vinylamine) (PVAm) formed an effective pair for the construction of LbL films with SiPS. When it was neutralized, SiPS was not assembled, probably due to the loss of effective polymer-polymer interactions. The ionic strength conditions revealed a slight difference of the assembly behavior on the isotactic polymer as compared to the atactic one. The assembled LbL film showed the same peaks over the range from 1141 to 1227 cm(-1) and 700 cm(-1) in the FT-IR/ATR spectra as the bulk complex of SiPS/PVAm, and the thickness on one side was calculated at 76 nm by QCM analysis. The surface roughness of the film was also observed by AFM. 相似文献
Positronium is an ideal system for the research of the quantum electrodynamics (QED) in bound state. The hyperfine splitting (HFS) of positronium, ΔHFS, gives a good test of the bound state calculations and probes new physics beyond the Standard Model. A new method of QED calculations has revealed the discrepancy by 15 ppm (3.9σ) of ΔHFS between the QED prediction and the experimental average. There would be possibility of new physics or common systematic uncertainties in the previous all experiments. We describe a new experiment to reduce possible systematic uncertainties and will provide an independent check of the discrepancy. We are now taking data and the current result of ΔHFS?=?203.395 1 ±0.002 4 (stat., 12 ppm) ±0.001 9 (sys., 9.5 ppm) GHz has been obtained so far. A measurement with a precision of O(ppm) is expected within a year. 相似文献
Poly(lactic acid) (PLA) particles dispersed in water were transformed into nanofibers by simply heating above the glass transition temperatures of the hydrated PLAs. 相似文献
The structure of melittin bound to dodecylphosphocholine (DPC) micelles was investigated using hydrogen–deuterium (H/D) exchange in conjunction with collision induced dissociation (CID) in an rf-only hexapole ion guide with electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR MS). The deuterium incorporation into backbone amide hydrogens of melittin with or without DPC micelles was analyzed at different time points examining the mass of each fragment ion produced by hexapole CID. When melittin existed alone in aqueous solution, more than 80% of amide hydrogens was exchanged within 10 s, and the deuterium content in each fragment ion showed high values throughout the experiments. When melittin was bound to DPC micelles, the percentage of deuterium incorporation into the fragment decreased remarkably at any time point. It increased little by little as the exchange period prolonged, indicating that some stable structure was formed by the interaction with DPC. The results obtained here were consistent with the previous studies on the helical structure of melittin carried out by NMR and CD analyses. The strategy using H/D exchange and MS analysis might be useful for studying structural changes of peptides and proteins caused by phospholipid micelles. It could also be applied to membrane-bound proteins to characterize their structure. 相似文献
Summary: A chitosan‐hydroxybenzotriazole (HOBt) aqueous solution prepared by simply mixing chitosan and HOBt in water provides an effective system to functionalize chitosan in an aqueous environment. This aqueous solution in combination with water‐soluble carbodiimide (WSC) allows the conjugation of functional groups onto chitosan under mild conditions without requiring any organic solvents or acid and heat. In this contribution, a series of model reactions that use a novel water‐based system of chitosan to functionalize the polymer with boc‐L ‐phenylalanine, poly(ethylene glycol) methyl ether, and dicarboxylated poly(ethylene glycol) is demonstrated.
Chitosan‐HOBt is effectively conjugated with R‐COOH via a water‐soluble carbodiimide (WSC) conjugating agent. 相似文献
A rapid and sensitive spectrophotometric method for the simultaneous determination of sodium dodecyl sulphate (SDS) and sodium linear-dodecylbenzenesulphonate (DBS) with 1-stearyl-4-(4-aminonaphthylazo)-pyridinium bromide (SAPB) is described using the difference at the maximum absorption wavelength of the SDS- and the DBS-ion associate. SDS and DBS have been determined independently by measuring their respective absorbances at the maximum absorption wavelength. The apparent molar absorptivities of the SDS- and the DBS-ion associate are 8.0×104 l mol–1 cm–1 at 445 nm and 4.5×104 l mol–1 cm–1 at 424 nm, respectively. The calibration graph for SDS is linear in the range from 0.1 to 1.0×10–6 mol/l in the presence of 1.2×10–6 mol/l DBS and for DBS from 0.8 to 2.0×10–6 mol/l in the presence of 8.0×10–7 mol/l SDS. The relative standard deviation (n=15) for 8.0×10–7 mol/l SDS is 3.4% and for 1.6×10–6 mol/l DBS 2.1%. The proposed method has been applied to the simulatenous determination of SDS and DBS in river water samples. 相似文献
Triphenylstibine oxide (Ph3SbO) and phosphorus(V) sulfide (P4S10) synergistically catalyzed the aminolysis of N-protected amino-acids with amino-acid esters in benzene. Ph3SbO accelerated both the initial conversion of carboxylic moieties into the corresponding thiocarboxylic moieties by P4S10 and the subsequent aminolysis of the resulting thiocarboxylic acids. Thus, dipeptides such as Z–A–A′–OEt (where Z = PhCH2OC(O)– and A,A′ = Ala,Gly; Gly,Gly; Leu,Gly; Phe,Gly; Phe,Leu;Ser,Gly; Val,Gly, respectively) were conveniently prepared even at 35°C. 相似文献
This paper is described for T-matrix analysis of the electromagnetic wave diffraction from a Fourier grating that the boundary
value problem is treated by applying the extended boundary condition. The rigorous form of the expression of matrix elements
is presented in the term of Bessel functions of the first kind. The error of power conservation versus the truncated number
has been examined for mode number. Diffraction efficiencies versus groove depth and wavelength for a second or third harmonic
wave of Fourier grating have been discussed. Numerical results are in good agreement with those obtained from other method
and experimental values. Reasonable numerical results are presented for a groove depth per period of the Fourier grating less
than 0.25. 相似文献