Synthesis and Application of Histidine-Modified Poly(Glycidyl Methacrylate/Ethylene Glycol Dimethacrylate) Sorbent for Isolation of Caffeine from Black and Green Tea Samples

This work presents the synthesis of a polymeric mixed-mode solid-phase extraction (SPE) sorbent for clean-up and isolation of caffeine from black and green tea samples. The material was synthesized by a simple thermally initiated copolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate. Further functionalization was executed with histidine (HIS). Functional groups were investigated by attenuated total-reflection infrared spectroscopy. Furthermore, nitrogen sorption porosimetry was executed and revealed surface areas of 90 m² g^??1. Adsorption capacities for caffeine were compared between functionalized and non-modified polymers and showed maximum capacities of 3.01 and 4.82 mg g^??1 polymer, respectively. Time adsorption profiles revealed an equilibrium adsorption after 15 min. The proposed polymer was used for SPE of black and green tea extracts and showed excellent clean-up efficiency for isolation of caffeine with recoveries ranging from 89 to 93%. When compared to commercially available Oasis HLB, the HIS-functionalized polymer demonstrated a distinctly better performance for clean-up. Finally, the proposed method was validated regarding international (ICH) guidelines and regulations.     

Enrichment of low-abundant serum proteins by albumin/immunoglobulin G immunoaffinity depletion under partly denaturing conditions

We present a simple protocol for affinity depletion to remove the two most abundant serum proteins, albumin and immunoglobulin G (IgG). Under native conditions, albumin/IgG were efficiently removed and several proteins were enriched as shown by two-dimensional electrophoresis (2-DE). Besides that, partly denaturing conditions were established by adding 5 or 20% acetonitrile (ACN) in order to disrupt the binding of low-molecular-weight (LMW) proteins to the carrier proteins albumin/IgG. 2-DE results showed that the total number of detected LMW proteins increased under denaturing conditions when compared to native conditions. Interestingly, the presence of 5% ACN in serum revealed better enrichment of LMW proteins when compared to 20% ACN condition. Seven randomly distributed spots in albumin/IgG depleted serum samples under 5% ACN condition were picked from the 2-DE gels and identified by mass spectrometry (MS). The intensity of five LMW protein spots increased under denaturing conditions when compared to native conditions. Three of the seven identified spots (serum amyloid P, vitamin D-binding protein, and transthyretin) belong to a group of relatively low-abundant proteins, which make up only 1% of all serum proteins. The method presented here improves the resolution of the serum proteome by increasing the number of visualized spots on 2-D gels and allowing the detection and MS identification of LMW proteins and proteins of lower abundance.     

Effects of nanoconfinement on the morphology and reactivity of organic materials

When organic materials are placed in environments which physically confine the materials at the nanometre scale, interfacial effects and confinement-induced loss of entropy can significantly alter materials' properties such as the glass transition temperature as well as the nanoscale morphology as compared to a "free" system. In block copolymers, nanoconfinement leads to a range of unusual self-organized nanoscale morphologies. In this article, attempts to induce nanoconfinement effects in new polymer systems as well as at interfaces will be highlighted and some possible future implications for organic synthesis and biology will be discussed.     

Recent progress in high-performance capillary bioseparations

Bioanalysis is a fast growing domain with new technological developments in the field of mass spectrometry, separation science, and bioinformatics. The central role of separation prior to detection and evaluation of analytes is indisputable. In fact, since the decipherment of the human genome via multichannel capillary electrophoresis in combination with laser-induced fluorescence [1], the analysis of the proteome, i.e., the type and amount of all proteins expressed at a certain time by the genome in a cell or tissue [2] became of central interest. Therefore, new fast and sensitive capillary liquid chromatographic, electrophoretic, and electrochromatographic separation techniques, suitable for high-throughput analysis of proteins, peptides and nucleic acids, are required.     

Remarkable solvent-dependent excited-state chirality: a molecular modulator of circularly polarized luminescence

The photochemical control of ground- and excited-state chirality of (M)-cis-(1) and (P)-trans-(2)-2-nitro-7-(dimethylamino)-9-(2',3'-dihydro-1'H-naphtho[2,1-b]-thiopyran-1'-ylidene)-9H-thioxanthene is described. It is shown that while ground state chirality can be controlled photochemically by irradiation with light of different wavelengths, the excited state chirality can be tuned either photochemically in a similar way or by appropriate choice of solvent. In benzene solution, circularly polarized luminescence of the two isomers with opposite ground-state helicity, (M)-cis-1 and (P)-trans-2, revealed corresponding excited states of opposite helicity. On the contrary, in n-hexane solution, circularly polarized luminescence was identical for the two forms indicating identical excited state chirality. Circularly polarized luminescence (CPL), steady-state and time-dependent fluorescence, and time-resolved microwave conductivity (TRMC) measurements in both n-hexane and benzene are reported, which provide an explanation for the remarkable solvent dependence of excited-state chirality.     

Eine analytische Brennstoffzelle als Alkoholsensor

An analytical fuel cell for the quantitative determination of alcohols is described. As an example of application its use as selective gas-chromatographic detector is demonstrated. The cell contains a symmetrical bipolar Pt/Pt gas diffusion electrode with an acid electrolyte which is surrounded by air on both sides. By this arrangement the reaction was not influenced by air because the rate of chemisorption of ethanol was much greater than that of oxygen. The polarization of the measuring electrode as a criterion of sensitivity was about 3 mV/μg ethanol.