Multidimensional nano-HPLC for analysis of protein complexes

The analysis of macromolecular protein complexes is an important factor in understanding most cellular processes, e.g., protein transport into cell organells, signal transduction via biological membranes, apoptosis, energy metabolism, directed motion of cells, and cell division. These complexes are not only built of various numbers of different proteins but also of prosthetic groups and RNA molecules. To understand the role each protein plays in a complex, a complete analysis of all protein compounds is necessary. Therefore, several separation steps have to be coupled to mass spectrometry to identify the proteins. In this work, we describe the application of multidimensional liquid chromatography, SCX-RP-LC as well as SAX-RP-LC, coupled to electrospray ion trap mass spectrometry. Tryptic digested ribosomes were separated by ion exchange chromatography manually collected and prepared for reversed phase chromatography to analyze the peptides via nano-ESI mass spectrometry. The total numbers of identified proteins are compared in consideration of the separation method (SCX-RP versus SAX-RP).     

Solid-phase synthesis of a type II′ β-turn peptido-mimetic library

The solid-phase synthesis of a dipeptide derived 2-amino-3-oxohexahydroindolizino[8,7-b]indole-5-carboxylate system (IBTM) is described. The IBTM moiety is formed via a solid-phase mediated Pictet-Spengler reaction of N-terminal tryptophan and the 4-{N-[1-(4,4-dimethyl-2,6-dioxocyclohexylidene)-3-methylbutyl]amino}benzyl (Dmab) ester of Fmoc protected aspartic acid β-aldehyde followed by γ-lactamization. This synthesis allows the regio- and stereoselective incorporation of a dipeptide surrogate of type II′ β-turns. The procedure is easily adaptable to combinatorial synthesis and a 576-member library was synthesized.     

Persistent Digermenes with Acyl and α-Chlorosilyl Functionalities

We report the preparation of α-chlorosilyl- and acyl-substituted digermenes. Unlike the corresponding transient disilenes, these species with a Ge=Ge double bond show an unexpectedly low tendency for cyclization, but in turn are prone to thermal Ge=Ge bond cleavage. Triphenylsilyldigermene has been isolated as a crystalline model compound, and is the first fully characterized example of a neutral digermene with an A₂GeGeAB substitution pattern. Spectroscopic and computational evidence prove the constitution of 1-adamantoyldigermene as a first persistent species with a heavy double bond conjugated with a carbonyl moiety.     

Randomized two‐way cross‐over bioequivalence study of two amoxicillin formulations and inter‐ethnicity pharmacokinetic variation in healthy Malay volunteers

The objectives of this study were to develop a new deproteinization method to extract amoxicillin from human plasma and evaluate the inter‐ethnic variation of amoxicillin pharmacokinetics in healthy Malay volunteers. A single‐dose, randomized, fasting, two‐period, two‐treatment, two‐sequence crossover, open‐label bioequivalence study was conducted in 18 healthy Malay adult male volunteers, with one week washout period. The drug concentration in the sample was analyzed using high‐performance liquid chromatography (UV–vis HPLC). The mean (standard deviation) pharmacokinetic parameter results of Moxilen® were: peak concentration (C_max), 6.72 (1.56) µg/mL; area under the concentration–time graph (AUC_0–8), 17.79 (4.29) µg/mL h; AUC_0–∞, 18.84 (4.62) µg/mL h. Those of YSP Amoxicillin® capsule were: C_max, 6.69 (1.44) µg/mL; AUC_0–8, 18.69 (3.78) µg/mL h; AUC0_0–∞, 19.95 (3.81) µg/mL h. The 90% confidence intervals for the logarithmic transformed C_max, AUC_0–8 and AUC_0–∞ of Moxilen® vs YSP Amoxicillin® capsule was between 0.80 and 1.25. Both C_max and AUC met the predetermined criteria for assuming bioequivalence. Both formulations were well tolerated. The results showed significant inter‐ethnicity variation in pharmacokinetics of amoxicillin. The C_max and AUC of amoxicillin in Malay population were slightly lower compared with other populations. Copyright © 2014 John Wiley & Sons, Ltd.     

Analytical solution to dielectric droplet diffusiophoresis under Debye–Hückel approximation

A simple analytical formula is obtained for the diffusiophoresis of a dielectric fluid droplet in symmetric binary electrolyte solutions under Debye–Hückel approximation valid for weakly charged droplets. The chemiphoresis is found to yield negative mobilities most of the time for droplets of constant surface charge density, which implies that the droplets tend to move away from the source releasing ionic chemicals. This is undesirable in some practical applications like drug delivery with liposomes in terms of conveying the drug-carrying liposomes to the desired area in the human body releasing specific ionic chemicals utilizing the self-guiding nature of diffusiophoresis. The further involvement of the electrophoresis component, however, may change the scenario via the oriented electric field generated by the induced diffusion potential. The lesson here is that while the impact of the chemiphoresis component is determined by nature and uncontrollable, the electrophoresis component serves as an artificially adjustable factor via choosing droplets with the surface charge of appropriate sign in practical applications. The results here have potential use in practical applications such as drug delivery. The portable simple analytical formula is a powerful asset to experimental researchers and design engineers in colloid science and technology to facilitate their works.     

Textile‐Compatible Substrate Electrodes with Electrodeposited ZnO—A New Pathway to Textile‐Based Photovoltaics

A strategy is presented to realize textile‐based photovoltaic cells motivated by developments of textile‐based electronics and their demand of grid‐independent energy supply. Beyond this, a development of textile‐based photovoltaics also represents an attractive pathway towards very flexible and rugged solar cells. The need for compatibility of an appropriate photovoltaic technology with the physical limitations of textiles is stressed. Electrodeposition from aqueous solutions is presented as a successful strategy to realize semiconductor structures on textiles and detailed control and influence of the deposition conditions is discussed. The role of microelectrode effects, options of forced convection, deposition under pulsed potential, alternative deposition baths and different substrate metals are emphasized. An active electrode material is presented which reaches a conversion efficiency close to the 1 % limit under AM 1.5 illumination conditions and thereby opens the door for a further optimization towards devices of technical interest.     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.