Proteins and peptides voltammetry: Trends,potential, and limitations

Numerous biological processes are connected with the efficient electron transfer reactions in proteins and peptides. In this review, we discuss briefly the relevance and current challenges associated with the voltammetric analysis of peptides and proteins with and without a metal redox center. Special attention is paid to the integration of electrochemical methods with new nanomaterials which offers amplification of multiplexing capabilities for simultaneous and very sensitive examination of various proteins. After critically discussing the most interesting approaches in the proteins/peptides voltammetric analysis reported so far, for the single or multiplexed examination of such biomolecules with demonstrated applicability in the real-sample analysis, existing challenges still need to be addressed and future directions in this field will be pointed out.     

Usefulness of chaotropic salt additive in RP‐HPLC of organic nonionized compounds

New synthesized 1,4‐disubstituted thiosemicarbazide derivatives were analyzed in the RP system, modified with the addition of salts; chaotropic (sodium hexafluorophosphate – Na PF₆), cosmotropic (sodium phosphate – NaH₂PO₄), and neutral (NaCl) on Zorbax XDB C18 column. The effect of the eluent composition on the analytes retention (k), system efficiency (N), peak symmetry (A_s), and LOD values were all examined and compared to unmodified organic‐aqueous mobile phase system. It was established that eluent modified with chaotropic salts addition was also the most advantageous according to other peak parameters such as the theoretical plates numbers and asymmetry factors. The lower LOD values were achieved in comparison to unmodified organic‐aqueous eluent system. Compatibility of lipophilicity parameters calculated by the use of computer software with experimental ones measured by RP‐HPLC was also the best for chaotropic modified mobile phase. To explain the observed phenomena, molecular modeling was performed for chosen representative compound in different environment representing examined mobile phase composition.     

Solvatochromic equilibria of cobalt(II) chloride in binary mixtures of dipolar aprotic solvents with water

The visible absorption spectra of CoCl₂ in binary mixtures of acetone, dmf, dma and dmso with H₂O show the existence of configuration equilibria between tetrahedral (T) and octahedral (O) species. Linear correlations between the values of log K (K = [O]/[T]) and the mole fraction of H₂O, _w, have been observed in all the systems under study; their slopes decrease linearly with an increase of the donor number, DN, of the organic component of the mixture. The formation of octahedral species is enthalpy favoured but entropy disfavoured. It was found that both H and S values change linearly with _w and the slopes of these relationships depend clearly on the DN values.     

Determination of nonsteroidal antiinflammatory drugs in water samples using liquid chromatography coupled with diode-array detector and mass spectrometry

An analytical method for the determination of trace levels of six different nonsteroidal antiinflammatory drugs (NSAIDs) in water samples has been developed and validated. Environmentally relevant pharmaceuticals were chosen according to human consumption in Poland. Final analysis of the target compounds was performed by RP LC-diode-array detection-MS, whereas sample preparation included an SPE step. For this SPE step, a number of packing materials, such as LiChrolut RP-18, calixarene, Strata-X, BAKERBOND Narc-2, BAKERBOND Polar Plus, BAKERBOND styrene divinylbenzene-1, and Discovery DSC-18, were used, and their respective advantages and disadvantages in this study were discussed. The RP-18 phase was found to be the most retentive for all analytes. The detection limits for compounds in surface waters were varied from 0.005 for diflunisal to 0.095 microg/L for ibuprofen. The average recoveries of NSAIDs from the surface water samples ranged from 80 up to 103%. RSD value is relatively low (from 4% for fenoprofen up to 8% for ibuprofen). The performance of the method was tested with several environmental water samples.     

Retention behaviour of some high-intensity sweeteners on different SPE sorbents

The objective of this paper is to provide information about application of solid-phase extraction (SPE) for isolation of nine high-intensity sweeteners (acesulfame-K, alitame, aspartame, cyclamate, dulcin, neotame, saccharin, sucralose and neohesperidin dihydrochalcone) from aqueous solutions. The influence of several types of LC-MS compatible buffers (different pH values and compositions) on their recovery has been studied and discussed. A number of commercially available SPE cartridges, such as Chromabond C18ec, Strata-X RP, Bakerbond Octadecyl, Bakerbond SDB-1, Bakerbond SPE Phenyl, Oasis HLB, LiChrolut RP-18, Supelclean LC-18, Discovery DSC-18 and Zorbax C18 were tested in order to evaluate their applicability for the isolation of analytes. Very high recoveries (better than 92%) of all studied compounds were obtained using formic acid-N,N-diisopropylethylamine buffer adjusted to pH 4.5 and C₁₈-bonded silica sorbents. Behaviour of polymeric sorbents strongly depends on their structure. Strata-X RP behaves much like a C₁₈-bonded silica sorbent. Recoveries obtained using Oasis HLB were comparable with those observed for silica-based sorbents. The only compound less efficiently (83%) retained by this sorbent was cyclamate. Bakerbond SDB-1 shows unusual selectivity towards aspartame and alitame. Recoveries of these two sweeteners were very low (26 and 42%, respectively). It was also found that aspartame and alitame can be selectively separated from the mixture of sweeteners using formic acid-triethylamine buffer at pH 3.5.     

Interplay between the Ribosomal Tunnel,Nascent Chain,and Macrolides Influences Drug Inhibition

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Highlights? Macrolides exhibit nascent polypeptide chain–dependent inhibition ? Peptides can form specific interactions with the ribosomal tunnel ? A covalent bond between tylosin and the ribosome is necessary for inhibitory activity     

Electrodeposition of gold nanoparticles at a solid|ionic liquid|aqueous electrolyte three-phase junction

Gold nanoparticles have been electrodeposited on an electrode through electrogeneration at an ITO|AuCl₄^? solution in an ionic liquid|aqueous electrolyte three-phase junction. The electrodeposition was carried out by inverted double-pulse potential chronoamperometry. The direct reduction of AuCl₄^? ions at the electrode is followed by a counterion transfer through the liquid|liquid interface. Contrary to the electrodeposition from a single ionic liquid phase, scanning electron microscopy reveals that the shape of the resulting nanoparticles is highly angular and well-developed with a diameter of 110 ± 30 nm. Catalytic oxidation of glucose on the modified electrode is demonstrated.     

Halogen,hydrogen and electrostatic interactions in 2‐amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium nitrate and 2‐amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium perchlorate

In the title compounds, C₇H₆ClN₂O⁺·NO₃⁻ and C₇H₆ClN₂O⁺·ClO₄⁻, the ions are connected by N—H...O hydrogen bonds and halogen interactions. Additionally, in the first compound, co‐operative π–π stacking and halogen...π interactions are observed. The energies of the observed interactions range from a value typical for very weak interactions (1.80 kJ mol⁻¹) to one typical for mildly strong interactions (53.01 kJ mol⁻¹). The iminium cations exist in an equilibrium form intermediate between exo‐ and endocyclic. This study provides structural insights relevant to the biochemical activity of 2‐amino‐5‐chloro‐1,3‐benzoxazole compounds.     

Improvement of the Water Resistance of a Narrow‐Band Red‐Emitting SrLiAl3N4:Eu2+ Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer

A SrLiAl₃N₄:Eu²⁺ (SLA) red phosphor prepared through a high‐pressure solid‐state reaction was coated with an organosilica layer with a thickness of 400–600 nm to improve its water resistance. The observed 4f⁶5d→4f⁷ transition bands are thought to result from the existence of Eu²⁺ at two different Sr²⁺ sites. Luminescence spectra at 10 K revealed two zero‐phonon lines at 15377 (for Eu(Sr1)) and 15780 cm^?1 (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu^2+/3+ result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White‐light‐emitting diodes of the SLA red phosphor and a commercial Y₃Al₅O₁₂:Ce³⁺ yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R9=69) and a low correlated color temperature of 2406 K.