Quantitation of low abundant soluble biomarkers using high sensitivity Single Molecule Counting technology.

Quantitation of biomarkers in biofluids plays a central role in basic research to management of patient care and is routinely used in clinical laboratories and academic institutions. Standard immunoassays, such as an enzyme-linked immunosorbent assay (ELISA), have provided understanding of both normal and pathological processes for many decades. However, in more recent decades, new immunoassay technologies have uncovered numerous analytes in blood that were once undetectable using traditional ELISAs. To meet this new challenge for quantifying low abundant proteins in biofluids, Single Molecule Counting (SMC™) technology was developed. This new technology is a combination of improvements to both the immunoassay procedure as well as the instrument. The aim of this article is to introduce the new SMCxPRO™ instrument, xPRO Acquisition and Analysis software, and the high sensitivity immunoassay kits validated on this instrument for the detection of low abundant proteins in biofluids, such as serum and plasma. Using this new technology platform, biomarkers that were once unquantifiable can now be quantitated in both normal and diseased biofluids.

Rapid online proteolytic mapping of PEGylated rhGH for identity confirmation, quantitation of methionine oxidation and quantitation of UnPEGylated N-terminus using HPLC with UV detection.

Proteolytic mapping is a widely used tool in the BioPharmaceutical Industry for the analysis of post-translation modifications as well as confirmation of protein identity by comparison to a well-characterized reference standard. This manuscript presents an integrated chromatographic approach which provides the ability to rapidly digest and analyze a PEGylated rhGH for methionine oxidation, identity confirmation and free (unPEGylated) N-terminal peptide by RP-HPLC using UV detection at 280 nm. This approach utilizes an online procedure in which the digestion step is integrated to the RP-HPLC analysis via an external column switching valve. A Poroszyme Trypsin cartridge is used in the digestion step, followed by delivery of the digested sample plug through a sample loop to an orthogonal RP-HPLC column for separation and quantitation of the resulting tryptic peptides. Oxidation of the methionine (met14) in the T2 tryptic fragment was quantified with a sensitivity of approximately 1.0% (peak area percent relative to parent T2). The RP-HPLC profile obtained with the integrated system was nearly identical to that obtained via traditional methods (e.g. batch digestion followed by RP-HPLC analysis). The integrated technique, however, represents a 10-fold reduction in total analysis time when compared to the optimized batch digestion procedure. In addition, the identity of the PEGylated rhGH compound could be confirmed as well as the percentage of free N-terminus in a single injection.

Structural bioinformatics-based prediction of exceptional selectivity of p38 MAP kinase inhibitor PH-797804.

PH-797804 is a diarylpyridinone inhibitor of p38alpha mitogen-activated protein (MAP) kinase derived from a racemic mixture as the more potent atropisomer (aS), first proposed by molecular modeling and subsequently confirmed by experiments. On the basis of structural comparison with a different biaryl pyrazole template and supported by dozens of high-resolution crystal structures of p38alpha inhibitor complexes, PH-797804 is predicted to possess a high level of specificity across the broad human kinase genome. We used a structural bioinformatics approach to identify two selectivity elements encoded by the TXXXG sequence motif on the p38alpha kinase hinge: (i) Thr106 that serves as the gatekeeper to the buried hydrophobic pocket occupied by 2,4-difluorophenyl of PH-797804 and (ii) the bidentate hydrogen bonds formed by the pyridinone moiety with the kinase hinge requiring an induced 180 degrees rotation of the Met109-Gly110 peptide bond. The peptide flip occurs in p38alpha kinase due to the critical glycine residue marked by its conformational flexibility. Kinome-wide sequence mining revealed rare presentation of the selectivity motif. Corroboratively, PH-797804 exhibited exceptionally high specificity against MAP kinases and the related kinases. No cross-reactivity was observed in large panels of kinase screens (selectivity ratio of >500-fold). In cellular assays, PH-797804 demonstrated superior potency and selectivity consistent with the biochemical measurements. PH-797804 has met safety criteria in human phase I studies and is under clinical development for several inflammatory conditions. Understanding the rationale for selectivity at the molecular level helps elucidate the biological function and design of specific p38alpha kinase inhibitors.