A group of functionalized oxazoles were synthesized in moderate to good yields from enamides via phenyliodine diacetate (PIDA)-mediated intramolecular cyclization. The main advantageous features of the present method include its broad substrate scope and the heavy-metal-free characteristic of the oxidative carbon-oxygen bond formation process.

High throughput protein–ligand interaction screening assays employing mass spectrometric detection are widely used in early stage drug discovery. Mass spectrometry-based screening approaches employ a target protein added to a pool of small-molecule compounds, and binding is assessed by measuring ligands denatured from the complexes. Direct analysis of protein–ligand interactions using native mass spectrometry has been demonstrated but is not widely used due to the detection limit on protein size, the requirement of volatile buffers, and the necessity for specialized instrumentation to preserve weak interactions under native conditions. Here we present a robust, quantitative, and automated online size-exclusion chromatography-native mass spectrometry (SEC-nMS) platform for measuring affinities of noncovalent protein–small-molecule interactions on an Orbitrap mass spectrometer. Indoleamine 2,3-dioxygenase 1, a catabolic enzyme, and inhibitory ligands were employed as a demonstration of the method. Efficient separation and elution enabled preservation of protein–ligand complexes and increased throughput. The high sensitivity and intra charge state resolution at high m/z offered by the Exactive Plus EMR Orbitrap allowed for protein ligand affinity quantitation and resolved individual compounds close in mass. Vc50 values determined via collision-induced dissociation experiments enabled the evaluation of complex stability in the gas phase and were found to be independent of the extent of complex formation. For the first time, Vc50 determinations were achieved on an inline SEC-nMS platform. Systematic comparison of our method with optimized chip-based nanoelectrospray infusion served as a reference for ligand screening and affinity quantitation and further revealed the advantages of SEC-MS.

No abstract

Metal labeling and ICP MS detection offer an alternative to commonly accepted techniques that are currently used to quantitate exogenous proteins in vivo, but modifying the protein surface with metal-containing groups inevitably changes its biophysical properties and is likely to affect trafficking and biodistribution. The approach explored in this work takes advantage of the presence of hexa-histidine tags in many recombinant proteins, which have high affinity toward a range of metals. While many divalent metals bind to poly histidine sequences reversibly, oxidation of imidazolebound Co II or Ru II is known to result in a dramatic increase of the binding strength. In order to evaluate the feasibility of using imidazole-bound metal oxidation as a means of attaching permanent tags to polyhistidine segments, a synthetic peptide YPDFEDYWMKHHHHHH was used as a model. Ru II can be oxidized under ambient (aerobic) conditions, allowing any oxidation damage to the peptide beyond the metalbinding site to be avoided. The resulting peptide−Ru III complex is very stable, with the single hexa-histidine segment capable of accommodating up to three metal ions. Localization of Ru III within the hexa-histidine segment of the peptide was confirmed by tandem mass spectrometry. The Ru III /peptide binding appears to be irreversible, with both low-and high-molecular weight biologically relevant scavengers failing to strip the metal from the peptide. Application of this protocol to labeling a recombinant form of an 80 kDa protein transferrin allowed Ru III to be selectively placed within the His-tag segment. The metal label remained stable in the presence of ubiquitous scavengers and did not interfere with the receptor binding, while allowing the protein to be readily detected in serum at sub-nM concentrations. The results of this work suggest that ruthenium lends itself as an ideal metal tag for selective labeling of His-tag containing recombinant proteins to enable their sensitive detection and quantitation with ICP MS.

ASP flooding in Daqing oilfield commenced from 1980s. To date, industrial pilot tests have been carried out in three blocks. The averaged recovery was increased by 20%. On the other hand, scaling issue caused high frequent pump failures. Large amount of scale building up in the producers wellbore and downhole equipments with high speed, which resulted in the averaged running life of lifting system decreased from 599 days of water flooding period to 60 days. Further more, some producers’ running lives were only around 30 days, leading to higher production cost and lower production rate as well. Study indicated that, the scaling principle and scale composition in producing wells differed from each other and was difficult to be predicted accurately. In this study, after tracking and measuring the ion in produced fluid for the whole process from water flooding, polymer flooding to ASP flooding and analyzing composition of the scale on different parts of scaling well, the criterion and distinguishing chart of scaling tendency had been set up initially. The criteria were applied in 102 wells in ASP flooding area, the accordance rate was more than 90 percent. Based on that, scaling inhibition technology was timely performed for predicted scaling wells, and the running lives were increased from 40 days to above 200 days. This paper presented the process of the study and is greatly helpful for APS flooding in commercial scale.