Phenylethenyl‐Substituted Triphenylamines: Efficient,Easily Obtainable,and Inexpensive Hole‐Transporting Materials

Star‐shaped charge‐transporting materials with a triphenylamine (TPA) core and various phenylethenyl side arm(s) were obtained in a one‐step synthetic procedure from commercially available and relatively inexpensive starting materials. Crystallinity, glass‐transition temperature, size of the π‐conjugated system, energy levels, and the way molecules pack in the solid state can be significantly influenced by variation of the structure of these side arm(s). An increase in the number of phenylethenyl side arms was found to hinder intramolecular motions of the TPA core, and thereby provide significant enhancement of the fluorescence quantum yield of the TPA derivatives in solution. On the other hand, a larger number of side arms facilitated exciton migration through the dense side‐arm network formed in the solid state and, thus, considerably reduces fluorescence efficiency by migration‐assisted nonradiative relaxation. This dense network enables charges to move more rapidly through the hole‐transport material layer, which results in very good charge drift mobility (μ up to 0.017 cm² V ^?1 s^?1).     

Evaluation of Redox Activity of Human Myocardium‐derived Mesenchymal Stem Cells by Scanning Electrochemical Microscopy

In this study the redox activity of human myocardium‐derived mesenchymal stem cells (hmMSC) were investigated by redox‐competition (RC‐SECM) and generation‐collection (GC‐SECM) modes of scanning electrochemical microscopy (SECM), using 2‐methylnaphthalene‐1,4‐dione (menadione, MD) as a redox mediator. The redox activity of human healthy and dilated hmMSCs was evaluated by measuring reduction of MD. Measurements were performed by approaching and retracting the UME from the surface of growing hmMSC cells. The current study shows that the RC‐SECM mode can be applied to investigate integrity of cell membranes, whereas the most promising results were observed by using the GC‐SECM mode and applying the Hill's equation for the calculation/fitting of dependencies of electrical current vs menadione concentration. The calculated apparent Michaelis constant (K_M) for the production of menadiol (MDH₂) in the pathological hmMSC cells was 14.4 folds higher compared to that of the healthy hmMSC revealing the lover redox activity of pathological cells. Moreover, the calculated Hill's coefficient n shows a negative cooperative binding between MD and healthy hmMSC and positive cooperative binding between MD and pathological hmMSC. It means that healthy hmMSC is of lower affinity to MD, which is also related to the better membrane integrity of healthy cells. Data of this study demonstrate that SECM can be applied to investigate intracellular redox and membrane changes ongoing in human dilated myocardium‐derived hmMSC in order to improve their functioning and further regenerative potential.     

Analysis of Cibacron blue F3G-A interaction with therapeutic proteins by MALDI-TOF mass spectrometry

The formation of the complexes between Cibacron blue F3G-A and two therapeutic proteins, recombinant human interferon-alpha2b and recombinant human growth hormone, was investigated. The method of time-resolved limited proteolysis coupled with MALDI-TOF mass spectrometry was used. The analysis of peptide maps revealed that A(17)HR(19) and L(20)HQLAFDTYQEFEEAYIPK(38) of hGH, and R(14)TLMLLAQMR(23) and D(33)RHDFGFPQEEFGNQFQK(50) of hIFN-alpha2b, exhibit affinity to Cibacron blue F3G-A. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Large-Scale Reassessment of In-Vineyard Smoke-Taint Grapevine Protection Strategies and the Development of Predictive Off-Vine Models

Smoke taint in wine is thought to be caused by smoke-derived volatile phenols (VPs) that are absorbed into grape tissues, trapped as conjugates that are imperceptible by smell, and subsequently released into wines as their free odor-active forms via metabolism by yeasts during fermentation. Blocking VP uptake into grapes would, therefore, be an effective way for vineyards to protect ripening grape crops exposed to smoke. Here, we re-evaluated a biofilm that had previously shown promise in pilot studies in reducing levels of smoke-derived VPs. A suite of nine free and acid-labile VPs were quantitated in Pinot Noir grapes that had been exposed to smoke after being coated with the biofilm one, seven or 14 days earlier. In contrast with earlier studies, our results demonstrated that in all cases, the biofilm treatments led to increased concentrations of both free and total VPs in smoke-exposed grapes, with earlier applications elevating concentrations of some VPs more than the later time points. Tracking VP concentrations through the grape ripening process demonstrated that some (phenol, p/m-cresol, and guaiacol) were not entirely sequestered in grapes as acid-labile conjugates, suggesting the presence of VP storage forms beyond simple glycosides. Free VPs in grapes, though a minor portion of the total, most clearly correlated with concentrations present in the resulting wines. Finally, red table grapes, available year round, were observed to replicate the effects of the biofilm treatments and were capable of transforming most VPs into acid-labile conjugates in under 24 h, indicating that they might be an effective model for rapidly assessing smoke-taint prophylactic products in the laboratory.     

Copper bronze catalyzed Heck reaction in ionic liquids

Heck reaction of aryl iodides and activated aryl bromides catalyzed by copper bronze in tetrabutylammonium bromide as solvent and tetrabutylammonium acetate as base was developed. The effective catalysts are Cu nanoparticles deriving from the reaction of iodobenzene with copper bronze. These nanoparticles are very stable in tetraalkylammonium salts, are easily recycled, and can be stored for months without a loss of catalytic efficiency. [reaction: see text]     

Screening of antioxidant activity and volatile compounds composition of Chamerion angustifolium (L.) Holub ecotypes grown in Lithuania

Since biological activity of medicinal plants is dependent on cultivation area, climatic conditions, developmental stage, genetic modifications and other factors, it is important to study flora present in different growing sites and geographical zones. This study was focused on screening of antioxidant activity of C. angustifolium harvested in six different locations in Lithuania. The total contents of phenolic compounds, flavonoids and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity were evaluated by spectrophotometric methods. A correlation between radical scavenging activity and total phenolic compounds content was observed (correlation coefficient 0.98). HPLC with online post-column DPPH radical scavenging reaction detection was used for the separation of extracts. Oenothein B, rutin and one unidentified compound were predominant. Volatile compounds were analysed using solid-phase microextraction coupled with gas chromatography–mass spectrometry. Based on the analysis of volatiles, all samples were classified into two chemotypes: (I) with predominant α- and β-caryophyllenes and (II) with predominant anethole.     

High-performance liquid chromatography (HPLC)-size exclusion chromatography (SEC) for qualitative detection of humic substances and dissolved organic matter in mineral soils and peats in Lithuania

High-performance liquid chromatography (HPLC) with size exclusion (SEC) separation function was used to isolate and examine the molecular mass (MM) distributions and polydispersity of humic substances (HSs) and dissolved organic matter (DOM) from mineral soils and peats. The aim was to improve their detailed characterisation and to inform of their soil carbon (C) sequestration and environmental quality. This is the first study conducted in Lithuania in which HSs and DOM, separated from two soil types, have been used to characterise soil at the molecular level. The HPLC-SEC, as a separation method, was coupled with diode-array detection (DAD), thus enabling the separation of molecular fractions. Results showed that HPLC-SEC can be used to determine the MM of HSs in soil, provided that the relation between retention time and MM is known and a suitable method for fitting the HS peak is available. The UV-spectra analysis showed that DOM has a larger MM (M_w = 2439–3436 Da), which contains more aliphatic C. The HS fraction has a smaller MM (M_w = 2776 Da), with aromatic structures that reflect a higher aromaticity. Separated fractions had characteristic MMs of humic acid (HA) and fulvic acid (FA) and DOM. The HSs separated from peat samples were characterised by higher aromaticity, humification and stability. The HSs extracted from mineral soil samples showed a higher degradability level. The results also show the MM distribution and polydispersity of HS and DOM fractions (M_w/M_n = 1.009–1.252) are relatively homogenous in both soil types. Findings confirm that chromatographic and spectrometric parameters can be used for characterisation of both HSs and DOM, and for detecting changes in organic matter quality. Moreover, they can also be used for a further understanding the C-cycle and could be applied for enhancing soil C-sequestration and informing environmental quality management.     

Reflection Absorption Infrared Spectroscopy Characterization of SAM Formation from 8-Mercapto-N-(phenethyl)octanamide Thiols with Phe Ring and Amide Groups

Multifunctional amide-containing self-assembled monolayers (SAMs) provide prospects for the construction of interfaces with required physicochemical properties and distinctive stability. In this study, we report the synthesis of amide-containing thiols with terminal phenylalanine (Phe) ring functionality (HS(CH₂)₇CONH(CH₂)₂C₆H₅) and the characterization of the formation of SAMs from these thiols on gold by reflection absorption infrared spectroscopy (RAIRS). For reliable assignments of vibrational bands, ring deuterated analogs were synthesized and studied as well. Adsorption time induced changes in Amide-II band frequency and relative intensity of Amide-II/Amide-I bands revealed two-state sigmoidal form dependence with a transition inflection points at 2.2 ± 0.5 and 4.7 ± 0.5 min, respectively. The transition from initial (disordered) to final (hydrogen-bonded, ordered) structure resulted in increased Amide-II frequency from 1548 to 1557 cm⁻¹, which is diagnostic for a strongly hydrogen-bonded amide network in trans conformation. However, the lateral interactions between the alkyl chains were found to be somewhat reduced when compared with well-ordered alkane thiol monolayers.     

Ether-directed diastereoselectivity in catalysed Overman rearrangement: comparative studies of metal catalysts

Ether-directed diastereoselectivity in Overman rearrangement of δ-methoxy and δ-TBDMSO substituted allylic trichloroacetimidates has been explored using PtCl₂, PtCl₄, AuCl and AuCl₃ catalysts in comparison with commonly used Pd(II) catalysts. For both substrates the use of PtCl₂ catalyst gave notably improved anti/syn-ratio of 1,2-aminoalcohol derivatives (anti/syn=11:1 for δ-methoxy; 6:1 for δ-TBDMSO) compared to all metal catalysts known to promote Overman rearrangement. Formation of 2-trichloromethyloxazoline was observed as a dominant side reaction in the metal catalysed rearrangement of δ-methoxy substituted allylic trichloroacetimidates considerably reducing the yield of the desired product. This side reaction was suppressed when δ-TBDMS-ether was used as a directing group.     

Comparative analysis of radical scavenging and antioxidant activity of phenolic compounds present in everyday use spice plants by means of spectrophotometric and chromatographic methods

Comparative analysis of radical scavenging and antioxidant activities of phenolic compounds present in everyday use spice plants was carried out by means of spectrophotometric and chromatographic methods. Six spice plant samples, namely onion (Allium cepa), parsley (Petroselinum crispum) roots and leaves, celery (Apium graveolens) roots and leaves and leaves of dill (Anethum graveolens) were analyzed. Total amount of phenolic compounds and radical scavenging activity (RSA) was the highest in celery leaves and dill extracts and was the lowest in celery roots. Comparing commonly used spectrophotometric analysis of 2,2-diphenyl-1-picrylhydrazyl (DPPH) RSA of extracts with the results obtained using reversed-phase chromatographic separation with on-line post-column radical scavenging reaction detection, good correlation was obtained (R(2)=0.848). Studies using HPLC system with electrochemical detector showed that bioactive phytochemicals can be separated and antioxidant activities of individual compounds evaluated without the need of a complex HPLC system with reaction detector. The results obtained using electrochemical detection correlate with the RSA assayed using spectrophotometric method (R(2)=0.893).