Citations

Recently, the concept of ligand-directed signaling—the ability of different ligands of an individual receptor to promote distinct patterns of cellular response—has gained much traction in the field of drug discovery, with the potential to sculpt biological response to favor therapeutically beneficial signaling pathways over those leading to harmful effects. However, there is limited understanding of the mechanistic basis underlying biased signaling. The glucagon-like peptide-1 receptor is a major target for treatment of type-2 diabetes and is subject to ligand-directed signaling. Here, we demonstrate the importance of polar transmembrane residues conserved within family B G protein-coupled receptors, not only for protein folding and expression, but also in controlling activation transition, ligand-biased, and pathway-biased signaling. Distinct clusters of polar residues were important for receptor activation and signal preference, globally changing the profile of receptor response to distinct peptide ligands, including endogenous ligands glucagon-like peptide-1, oxyntomodulin, and the clinically used mimetic exendin-4.

Objective. We compared laboratory developed real-time PCR assays for detection of Mycoplasma hominis and for detection and differentiation of Ureaplasma urealyticum and parvum to culture using genitourinary specimens submitted for M. hominis and Ureaplasma culture. Methods. 283 genitourinary specimens received in the clinical bacteriology laboratory for M. hominis and Ureaplasma species culture were evaluated. Nucleic acids were extracted using the Total Nucleic Acid Kit on the MagNA Pure 2.0. 5 μL of the extracts were combined with 15 μL of each of the two master mixes. Assays were performed on the LightCycler 480 II system. Culture was performed using routine methods. Results. M. hominis PCR detected 38/42 M. hominis culture-positive specimens, as well as 2 that were culture negative (sensitivity, 90.5%; specificity, 99.2%). Ureaplasma PCR detected 139/144 Ureaplasma culture-positive specimens, as well as 9 that were culture negative (sensitivity, 96.5%; specificity, 93.6%). Of the specimens that tested positive for Ureaplasma species, U. urealyticum alone was detected in 33, U. parvum alone in 109, and both in 6. Conclusion. The described PCR assays are rapid alternatives to culture for detection of M. hominis and Ureaplasma species, and, unlike culture, the Ureaplasma assay easily distinguishes U. urealyticum from parvum.

Abstract In shotgun proteomics, database search algorithms rely on fragmentation models to predict fragment ions that should be observed for a given peptide sequence. The most widely used strategy (Naive model) is oversimplified, cleaving all peptide bonds with equal probability to produce fragments of all charges below that of the precursor ion. More accurate models, based on fragmentation simulation, are too computationally intensive for on-the-fly use in database search algorithms. We have created an ordinal-regression-based model called Basophile that takes fragment size and basic residue distribution into account when determining the charge retention during CID/higher-energy collision induced dissociation (HCD) of charged peptides. This model improves the accuracy of predictions by reducing the number of unnecessary fragments that are routinely predicted for highly-charged precursors. Basophile increased the identification rates by 26% (on average) over the Naive model, when analyzing triply-charged precursors from ion trap data. Basophile achieves simplicity and speed by solving the prediction problem with an ordinal regression equation, which can be incorporated into any database search software for shotgun proteomic identification.