Derivatisation for liquid chromatography/electrospray mass spectrometry: synthesis of pyridinium compounds and their amine and carboxylic acid derivatives

A simple method has been developed for the pre-column derivatisation of low molecular weight primary and secondary amines and carboxylic acids using quaternary nitrogen compounds to enhance their detection by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The synthesis of seven novel quaternary nitrogen reagents is described. The derivatives are designed to be relatively small molecules to avoid some of the steric hindrance problems that may be associated with larger derivatisation reagents. The compounds have amine and carboxylic acid functional groups with which to derivatise carboxylic acids and amines, respectively. Two of the compounds contain a bromine atom in order to assess the advantages of a bromine isotope pattern in the mass spectra. This acts as a simple marker for derivatisation and enables data processing by cluster analysis.Activation of the carboxylic acid group was achieved by the use of either 1-chloro-4-methylpyridinium iodide (CMPI) or the more reactive 1-fluoro-4-methylpyridinium p-toluenesulphonate (FMP).1 Using both of these active reagents, the degree of nucleophilic substitution was investigated for the derivatisation of a variety of small molecules. Whilst giving some increase in the ESI-MS response for the derivatised compounds, the FMP itself acted as a derivatising reagent in a competing reaction. In the light of this finding, FMP was reacted with the test compounds separately and gave positive results as a derivatising reagent. Detection of the 'pre-charged' derivatives of amines and carboxylic acids by LC/ESI-MS was investigated with respect to their ESI response and chromatography.     

Isomerisation in the chemistry of platinacyclobutane complexes

The platinacyclobutane complexes PtCl₂L₂(C₃H₅Me)], L  pyridine, CD₃CN, or tetrahydrofuran, exist as mixtures of isomers containing P$\text{tCH}{}_2\text{CHMeC}$H₂ or P$\text{tCHMeCH}{}_2\text{CH}{}_2$ groups in rapid equilibrium. Decomposition occurs in some cases to give [PtCl₂L(CH₃CH₂CHCH₂)]. Stereospecific skeletal isomerisation also occurs in metallocyclobutanes containing the groups P$\text{tCHRCHRC}$H₂  P$\text{tCHRCH}{}_2\text{C}$HR, when R  aryl further decomposition gives ν-allylplatinum complexes.     

Anisotropic hydrogel thickness gradient films derivatized to yield three-dimensional composite materials

We report the preparation of in-plane density gradients of amino-terminated molecules and gold particles through derivatization of laterally varying thickness gradients of poly(acrylic acid) (PAA) or poly(acrylamide) (PAAm) films. PAA and PAAm gradients were formed by Zn(II)-catalyzed electropolymerization of acrylic acid (AA) or acrylamide (AAm) in the presence of an in-plane electrochemical potential gradient applied to Au or indium-tin-oxide (ITO) working electrodes. PAA thickness gradients were converted into density gradients of fluorocarbons or biocompatible groups by derivatizing with NH(2)CH(2)(CF(2))(6)CF(3) or an Arg-Gly-Asp (RGD)-containing peptide, respectively. X-ray photoelectron spectroscopy (XPS) and XPS imaging were used to characterize the modified PAA gradients. Transition regions as narrow as 104 mum were achieved for fluorocarbon gradients. PAAm gradients were treated with gold particles to form a density gradient of gold particles. Surface plasmon resonance imaging and scanning electron microscopy (SEM) as well as UV-visible absorption measurements were used to characterize the gold particle density gradients. It is likely that the gold particles were attached both on the surface and inside the PAAm film.     

Synthesen und chemisches Reaktionsverhalten von neuen Azapseudophenalenonen,Azapseudophenaleniumsalzen und ihren Fulvenen sowie Fulvalenen

Alkylation of the aza-pseudophenalenone1 with trialkyloxoniumtetrafluoroborates yield the azapseudophenaleniumsalts2 a,2 b, reactions with C-nucleophiles the compounds3 a 3 e, the dihydro-azapseudophenalenone4 reacts with malodinitrile-sodium to5,1 b and1 d with tetrachlorocyclopentadiene to the fulvalenes6 a,6 b,1 b was olefinated withtert. butyl-cyano-ketene to theZ-isomer7.

Meinem lieben Kollegen und Freund, Herrn Prof. Dr.Werner Heimann, Karlsruhe, mit herzlichen Wünschen zum 70. Geburtstag gewidmet.     

Optically detected zero-field triplet state magnetic resonance in photosynthetic bacteria

Triplet state transitions of the photosynthetic bacteria Rhodospirillum Rubrum, Rhodopseudomonas Spheroides and Chromatium Vinosum in chemically reduced preparations have been observed by zero-field optical detection of magnetic resonance at 2 K. For each bacterial preparation two sharp, structureless, zero-field EPR transitions were observed as microwave-induced decreases in the fluorescence intensity of the frozen cellular preparations. The depopulating rate constants for the spin sublevels of the triplet states observed in R Rubrum and R Spheroides were also measured. The similarities of the triplet state frequencies, spectral features and intersystem crossing rates suggest a common structure for the reaction centers in the photosynthetic bacteria.     

Strategies for multi-site GLP studies

 A GLP study can be performed at more than one site. This is called a multi-site study. Although, the study is performed at different sites, it is still one study and must completely comply with the GLP principles. The fact that different activities are conducted at different sites implies that the planning, the organization and the communication are crucial for the success of the study. This means that all the staff involved should know their responsibilities and should have the knowledge and skills to realize all the phases of the study according to the GLP principles. To achieve a well managed multi-site study, several strategies for setting up such a study can be followed. This paper focuses on the responsibilities, communication, and collaboration of the personnel, which are involved in a multi-site study. Several case studies are highlighted, and we concluded that the basic communication triangle in a single-site GLP study between test facility management, study director, and the quality assurance unit should be extended to the communication among test facility and test site management, study director, principle investigator(s), and the quality assurance units at the test sites. Introduction Received: 14 August 2002 Accepted: 26 November 2002     

An integrated solid-phase extraction system for sub-picomolar detection

A microchip structure etched on a glass substrate for packed column solid-phase extraction (SPE) and capillary electrochromatography (CEC) is described. A 200 microm long, octadecylsilane (ODS) packed column was secured using two different approaches: solvent lock or polymer entrapment. The former method was utilized for SPE while the latter approach was applied for CEC. In SPE, the ODS packed chamber gave a detection limit of 70 fM for a nonpolar BODIPY (493/503) dye when concentrated for 3 min at an electroosmotic flow rate of 4.14 nL/min, compared to 30 pM for this detector without the SPE step. SPE beds showed reproducible, linear calibration curves (R(2) = 0.9989) between 1 and 100 pM BODIPY at fixed preconcentration times. Breakthrough curves for the 330 pL (ODS-packed) bed indicated a capacity for BODIPY dye of 8.1 x 10(-14) mmol, or 0.25 mmol dye per liter of bed. The ODS-chamber could also be used to analyze dilute amino acid and peptide solutions. In the CEC format, two neutral dyes (BODIPY and acridine orange) were baseline-separated in an isocratic run with a theoretical plate count of 84 (420 000 plates/m) and a reduced plate height of about 1. A labeled peptide was also analyzed by CEC, using the acidic eluent (84% acetonitrile, and 26% aqueous trifluoroacetic acid (0.05%)) preferred for peptide separations on ODS-coated silica particles.     

Electrocatalytic activity of binary Palladium Ruthenium anode catalyst on Ni-support for ethanol alkaline fuel cells

In search for a cheaper anode catalyst for the oxidation of ethanol for development of direct alcohol fuel cells, Pd has been considered here as an interesting substitute for Pt in Pt Ru binary electrodeposite. The binary catalyst when co-deposited on nickel support has been found to increase the current density and decrease the anodic overvoltage significantly with respect to pure Pt, Pd and Ni. Its electrocatalytic capability is also comparable with that of the Pt-Ru binary electrocatalyst on Ni-support, when studied in 1 M EtOH containing 1 M NaOH solution. The effect of loading of Pd Ru electrocatalyst on Ni support has also been tested. The electrocatalytic activity of the electrodes for oxidation of ethanol has been explained by studies of cyclic voltammetry, chronopotentiometry, steady-state polarization, and conjugated scanning electron microscopy–energy dispersion X-ray spectroscopy. It has been found that electrode containing the higher amount of deposit are less affected by carbonaceous poisons.     

Condensation of 4-aryl-4-oxobutanoic acids with benzylamines: Synthetic and structural studies on 1-arylmethyl-3-[(<Emphasis Type="Italic">E</Emphasis>)-1-arylmethylidene]-5-phenyl-2,3-dihydro-1H-2-pyrrolones

The microwave-mediated reaction of 4-aryl-4-oxobutanoic acids with benzylamines furnished 1-arylmethyl-3-[(E)-1-arylmethylidene]-5-phenyl-2,3-dihydro-1H-pyrrolones. This result is in contract to the earlier report on this reaction conducted under neat conditions. Structures for the products were assigned on the basis of spectral data and confirmed by independent synthesis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 368–373, March, 2007.