Derivatization of peptides and small proteins for improved identification and detection in capillary zone electrophoresis (CZE)

Peptides and small proteins, of limited molecular weight (MW) can be derivatized with a 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (6-AQC) reagent, leading to a single capillary zone electrophoresis (CZE) peak, suggestive of a completely tagged product. The number of tags per molecule was demonstrated by matrix assisted, laser desorption, time-of-flight mass spectrometry (MALDI-TOFMS) studies. In CZE, these species have greatly improved plate count and peak shape, improved (lowered) detectabilities, and in general, improved identification properties in the CZE mode in high performance capillary electrophoresis (HPCE). The formation of what appears to be a single, homogeneously tagged product is a function of how the derivatizations are performed. Once these conditions are optimized, virtually all peptides and small proteins tested (limited MW) can form single, fully tagged products, with the desirable CZE properties. These derivatization approaches thus lead to products that perform and are detected much better in CZE than their precursors (native, untagged peptides). The determined plate counts for these tagged peptides were as high as 6 million plates/m, which was very reproducible, and 59–12,000 times higher than the untagged (native) molecules. The peak symmetry was also improved greatly. The limit of detection (LOD) of some tested 6-AQC tagged peptides were nine to 209 times improved (lower) with ultraviolet (UV) absorption detection, again as compared with that for the native species. The LOD could be further lowered via laser induced fluorescence (LIF) detection in CZE, especially when acetonitrile (ACN) containing buffers were used.     

Untersuchung von Harn, Blut und sonstigem biologischen Material

Ohne Zusammenfassung     

Early cure behavior of a liquid dicyanate ester resin

The early cure behavior of 4,4‐dicyanato 1,1‐diphenolethane resin with and without incorporating Cr(acac)₃, Co(acac)₃, and Cu(acac)₂, respectively, as catalysts was investigated by gel permeation chromatography. The curing intermediates were separated by the column elution method and characterized by Fourier transform infrared, ¹H, and ³C NMR spectroscopies. The results indicated that the formed dimer in the early cure stage is a straight chain containing a primary amino group. The formed triazine ring in the trimer has a strong catalytic effect on the remaining cyanate groups so that the reactivity of the trimers was significantly increased. The reactivities of the curing intermediates decreased with molecular size until 7‐mer was reached. The initial monomer consumption is described by second‐order‐rate kinetics. In the presence of metal acetylacetonates, the curing reactions may be accelerated, but they did not change the reaction path and preceding sequence of reactivities. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3085–3092, 2001     

A π‐stacked and conjugated hybrid based on poly(N‐vinylcarbazole) postfunctionalized with terfluorene for stable deep‐blue hole‐transporting materials

The combination of π‐stacked with π‐conjugated building blocks offers an essential strategy to construct multifunctional organic semiconductors (MOSs) with the unique optoelectrical properties. Covalent hybrids can efficiently avoid the intrinsic phase‐separation defects in corresponding blend system. In this contribution, poly(vinylcarbazole) tethered with terfluorene, PVK‐TF, as a double‐channeled π‐stacked and π‐conjugated hybrid (SCH), has been constructed via Friedal‐Crafts click postmodification (FCCP). The chemical structure and optoelectrical property were determined by GPC, UV–vis, PL, TGA, DSC, and CV. Its PL spectra in the annealing thin film at N₂ atmosphere without low‐energy emission bands centered at the 530 nm indicates that no π‐stacks between carbazole and TF or among TFs dominate the whole condensed phase, which is in agreement with the intrachain T‐shaped π‐pitched motifs in molecular modeling simulation due to steric hindrance effect in complicated diarylfluorenes (CDAFs). A supporting prototype stable deep‐blue PLED was successfully obtained with an Internationale de l'Eclairage (CIE) coordinates of (0.20, 0.10) and a width at half maximum (FWHM) of about 60 nm at high current density of 100 mA/cm² (35 V). Deep‐blue PVK‐TF is a promising MOS for hole‐transporting and host materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5221–5229, 2009     

High-temperature collisional energy transfer in highly vibrationally excited molecules II: Isotope effects in isopropyl bromide systems

Values for 〈ΔE_down〉, the average downward energy transferred from the reactant to the bath gas upon collision, have been obtained for highly vibrationally excited undeuterated and per-deuterated isopropyl bromide with the bath gases Ne, Xe, C₂H₄, and C₂D₄, at ca. 870 K. The technique of pressure-dependent very low-pressure pyrolysis (VLPP) was used to obtain the data. For C₃H₇Br, the 〈ΔE_down〉 values (cm^?1) are 490 (Ne), 540 (Xe), 820 (C₂H₄), and 740 (C₂D₄), and for C₃D₇Br, 440 (Ne), 570 (Xe), 730 (C₂H₄), and 810 (C₂D₄). The uncertainties in these values are ca. ±10%. The 〈ΔE_down〉 values for the inert bath gases Ne and Xe show excellent agreement with the theoretical predictions of the semi-empirical biased random walk model for monatomic/substrate collisional energy exchange [J. Chem. Phys., 80 , 5501 (1984)]. The relative effects of deuteration of the reactant molecule on 〈ΔE_down〉 also compare favorably with the predictions of this theoretical model. Extrapolated high-pressure rate coefficients (s^?1) for the thermal decomposition of reactant are 10^13.6±0.3 exp(?200 ± 8 kJ mol^?1/RT) for C₃H₇Br and 10^13.9±0.3 exp(?207 ± 8 kJ mol^±1/RT) for C₃D₇Br, which are consistent with previous studies and the expected isotope effect.