Aqueous chemistry of transition metals in oxidation state (I) in Nanodroplets

"Nanodroplets" consisting of a central ion surrounded by a solvation shell of water molecules provide an interesting medium for studies of aqueous transition-metal chemistry in the unusual oxidation state (I). While VI undergoes efficient, solvent shell dependent redox reactions to VII and VIII, the absence of any similar reactivity in aqueous CrI, Mn1, FeI, CoI, NiI, and CuI clusters is explained by a rapid precipitation of the corresponding single monochloride molecules from the nanosolutions.     

Additive Tuning of Redox Potential in Metallacarboranes by Sequential Halogen Substitution

The first artificially made set of electron acceptors is presented that are derived from a unique platform Cs[3,3′‐Co(C₂B₉H₁₁)₂], for which the redox potential of each differs from its predecessor by a fixed amount. The sequence of electron acceptors is made by substituting one, two, or more hydrogen atoms by chlorine atoms, yielding Cs[3,3′‐Co(C₂B₉H_11?yCl_y)(C₂B₉H_11?zCl_z)]. The higher the number of chlorine substituents, the more prone the platform is to be reduced. The effect is completely additive, so if a single substitution implies a reduction of 0.1 V of the redox potential of the parent complex, then ten substitutions imply a reduction of 1 V.     

Proteome profile of the MCF7 cancer cell line: a mass spectrometric evaluation

The development of novel proteomic technologies that will enable the discovery of disease specific biomarkers is essential in the clinical setting to facilitate early diagnosis and increase survivability rates. We are reporting a shotgun two-dimensional (2D) strong cationic exchange/reversed-phase liquid chromatography/electrospray ionization tandem mass spectrometry (SCX/RPLC/ESI-MS/MS) protocol for the analysis of proteomic constituents in cancerous cells. The MCF7 breast cancer cell line was chosen as a model system. A series of optimization steps were performed to improve the LC/MS experimental setup, sample preparation, data acquisition and database search protocols, and a data filtering strategy was developed to enable confident identification of a large number of proteins and potential biomarkers. This research has resulted in the identification of >2000 proteins using multiple filtering and p-value sorting. Approximately 1600-1900 proteins had p < 0.001, and, of these, approximately 60% were matched by >or=2 unique peptides. Alternatively, >99% of the proteins identified by >or=2 unique peptides had p < 0.001. When searching the data against a reversed database of proteins, the rate of false positive identifications was 0.1% at the peptide level and 0.4% at the protein level. The typical reproducibility in detecting overlapping proteins across replicate runs exceeded 90% for proteins matched by >or=2 unique peptides. According to their biological function, approximately 200 proteins were involved in cancer-relevant cellular processes, and over 25 proteins were previously described in the literature as putative cancer biomarkers, as they were found to be differentially expressed between normal and cancerous cell states. Among these, biomarkers such PCNA, cathepsin D, E-cadherin, 14-3-3-sigma, antigen Ki-67, TP53RK, and calreticulin were identified. These data were generated by subjecting to MS analysis approximately 42 microg of sample, analyzing 16 SCX peptide fractions, and interpreting approximately 55,000 MS2 spectra. Total MS time required for analysis was 40 h.     

Mass spectrometric studies on 4-aryl-1-cyclopropyl-1,2-dihydropyridinyl derivatives: an examination of a novel fragmentation pathway

Examination of the electrospray ionization product ion spectra of 1,2-dihydropyridinyl and 4-aryl-1,2-dihydropyridinyl derivatives bearing a 1-cyclopropyl or 1-trans-2-phenylcyclopropyl group has led to the characterization of unexpected fragment ions. For example, the base peak at m/z 156 present in the product ion spectrum of trans-1-(2-phenylcyclopropyl)-4-phenyl-1,2-dihydropyridine proved not to be the expected 4-phenylpyridinium species but rather the isomeric 3-phenyl-5-azoniafulvenyl species. The results of studies with a series of structural and isotopically labeled analogs require a novel fragmentation pathway to account for the formation of this and related fragment ions. One possible pathway is based on an initial 1,5-sigmatropic shift of a cyclopropylmethylene hydrogen atom that is accompanied by opening of the cyclopropyl ring. The resulting eniminium intermediates then fragment to yield the 5-azoniafulvenyl species.     

Construction of the mutually orthogonal extraordinary supersquares

Our purpose is to determine the complete set of mutually orthogonal squares of order d, which are not necessary Latin. In this article, we introduce the concept of supersquare of order d, which is defined with the help of its generating subgroup in $\mathbb{F}_d \times \mathbb{F}_d$ . We present a method of construction of the mutually orthogonal supersquares. Further, we investigate the orthogonality of extraordinary supersquares, a special family of squares, whose generating subgroups are extraordinary. The extraordinary subgroups in $\mathbb{F}_d \times \mathbb{F}_d$ are of great importance in the field of quantum information processing, especially for the study of mutually unbiased bases. We determine the most general complete sets of mutually orthogonal extraordinary supersquares of order 4, which consist in the so-called Type I and Type II. The well-known case of d ? 1 mutually orthogonal Latin squares is only a special case, namely Type I.     

Single-molecule precipitation of transition metal(I) chlorides in water clusters.

Metal ions in unusual oxidation states can be introduced into water clusters using a standard laser vaporization source. Such nanosolutions of a single ion in typically 50 water molecules are comparable to a 1 M bulk solution, and their chemistry can be studied in the ion trap of a Fourier transform ion cyclotron resonance mass spectrometer. We find that a strong acid like hydrogen chloride oxidizes the early transition metal vanadium to the more common +III state, while later first row transition metals retain their unusual +I oxidation state, and the binary metal chlorides M(I)Cl precipitate.     

Microfluidic platform with mass spectrometry detection for the analysis of phosphoproteins

The development of novel and reliable technologies for the analysis of proteins and their post-translational modifications, in particular, has recently received much attention and interest. The implementation of a fully integrated microfluidic device interfaced with MS detection for the analysis of phosphoproteins is presented in this paper. The microfluidic platform (3'x1.5') comprises two individual sample processing systems: one for performing direct sample infusion and one for performing microfluidic LC separations. Various MS detection strategies, specific for the study of post-translational modifications, were conducted using alpha-casein as a model protein. Neutral loss ion mapping, data-dependent triple-play and neutral loss analysis, and in situ dephosphorylation followed by LC separation and MS detection were performed. Consistent results in identifying phosphopeptides with conventional and microfluidic instrumentation have been obtained. Unlike with conventional instrumentation, however, the microfluidic device enabled the completion of each analysis from only a few microliters of sample, in approximately 10-15 min, and on a bioanalytical platform that facilitates multiplexing and disposability, and thus high-throughput, contamination-free analysis.     

High-throughput liquid-chromatography method with fluorescence detection for reciprocal determination of furosemide or norfloxacin in human plasma

A simple, high-throughput, highly selective and sensitive HPLC-FLD method for isolation and determination of furosemide and/or norfloxacin in human plasma samples following a simple organic solvent deproteinization step with acetonitrile as sample 'clean-up' procedure is reported. One of the two drug substances plays the internal standard role for the determination of the other. Separation of analyte and internal standard was achieved in less than 5.3 min (injection to injection) on a Chromolith Performance RP-18e column, using an aqueous component containing 0.015 mol/L sodium heptane-sulfonate and 0.2% triethylamine brought to pH = 2.5 with H(3)PO(4). The composition of the mobile phase was: acetonitrile-methanol-aqueous component = 70:15:15 (v/v/v) and the flow-rate was set up to 3 mL/min. The chromatographic method applied to the determination of furosemide relies on fluorescent detection parameters of 235 nm for the excitation wavelength, and 402 nm for the emission wavelength. In case of norfloxacin, the excitation wavelength is set up to 268 nm and the emission wavelength is set up to 445 nm. The overall method leads to quantitation limits of about 27 ng/mL for furosemide, and 19.5 ng/mL for norfloxacin, using an injection volume of 250 microL. The method was applied to the bioequivalence study of two furosemide-containing formulations.