PFOS dominates PFAS composition in ambient fine particulate matter (PM2.5) collected across North Carolina nearly 20 years after the end of its US production.

Contamination of drinking water by per- and polyfluoroalkyl substances (PFASs) emitted from manufacturing plants, fire-fighting foams, and urban waste streams has received considerable attention due to concerns over toxicity and environmental persistence; however, PFASs in ambient air remain poorly understood, especially in the United States (US). We measured PFAS concentrations in ambient fine particulate matter (PM2.5) at 5 locations across North Carolina over a 1 year period in 2019. Thirty-four PFASs, including perfluoroalkyl carboxylic, perfluoroalkane sulfonic, perfluoroalkyl ether carboxylic and sulfonic acids were analyzed by UHPLC/ESI-MS/MS. Quarterly averaged concentrations ranged from <0.004-14.1 pg m-3. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) ranged from <0.18 to 14.1 pg m-3, comparable to previous PM2.5 measurements from Canada and Europe (<0.02-3.5 pg m-3). Concentrations above 1 pg m-3 were observed in July-September at Charlotte (14.1 pg m-3, PFOA), Wilmington (4.75 pg m-3, PFOS), and Research Triangle Park (1.37 pg m-3, PFOS). Notably, PM2.5 has a short atmospheric lifetime (<2 weeks), and thus, the presence of PFOS in these samples raises questions about their sources, since PFOS production was phased out in the US ∼20 years ago. This is the first US study to provide insights into ambient PFAS concentrations in PM2.5.

HLA class I binding motifs derived from random peptide libraries differ at the COOH terminus from those of eluted peptides.

Recombinant HLA-A2, HLA-B8, or HLA-B53 heavy chain produced in Escherichia coli was combined with recombinant beta2-microglobulin (beta2m) and a pool of randomly synthesised nonamer peptides. This mixture was allowed to refold to form stable major histocompatability complex (MHC) class I complexes, which were then purified by gel filtration chromatography. The peptides bound to the MHC class I molecules were subsequently eluted and sequenced as a pool. Peptide binding motifs for these three MHC class I molecules were derived and compared with previously described motifs derived from analysis of naturally processed peptides eluted from the surface of cells. This comparison indicated that the peptides bound by the recombinant MHC class I molecules showed a similar motif to naturally processed and presented peptides, with the exception of the peptide COOH terminus. Whereas the motifs derived from naturally processed peptides eluted from HLA-A2 and HLA-B8 indicated a strong preference for hydrophobic amino acids at the COOH terminus, this preference was not observed in our studies. We propose that this difference reflects the effects of processing or transport on the peptide repertoire available for binding to MHC class I molecules in vivo.

Isotope or mass encoding of combinatorial libraries.

BACKGROUND: Combinatorial chemistry using solid-phase synthesis is a rapidly developing technology that can result in a significant reduction in the time required to find and optimize lead compounds. The application of this approach to traditional medicinal chemistry has led to the construction of libraries of small organic molecules on resin beads. A major difficulty in developing large combinatorial libraries is the lack of a facile encoding and decoding methodology to identify active compounds. RESULTS: Several encoding schemes are described which use the ability of mass spectrometry to ascertain isotopic distributions. Molecular tags are attached to resin beads in parallel or on the linker used for chemical library synthesis. The tags are encoded via a controlled ratio of a number of stable isotopes on the tagging molecules, and range from a single to a complex isotopic distribution. CONCLUSIONS: A novel coding scheme is described that is useful for the generation of large encoded combinatorial libraries. The code can be cleaved after assay and analyzed by mass spectrometry in an automated fashion. An important element of the combinatorial discovery process is the ability to extract the structure-activity relationship (SAR) information made available by library screening. The speed and sensitivity of the mass-encoding scheme has the potential to determine the full SAR for a given library.

Agouti structure and function: characterization of a potent alpha-melanocyte stimulating hormone receptor antagonist.

The murine agouti gene encodes for a novel 131 amino acid protein. The sequence includes a 22 residue putative secretion signal, an internal basic region, and a C-terminal domain containing 10 cysteines. Agouti has been found to antagonize the binding of certain pro-opiomelanocortin peptides, such as alpha-melanocyte stimulating hormone (alpha-MSH), to the murine melanocortin-1 receptor (MC1-R). We report the purification of a secreted murine agouti to homogeneity by a two-step procedure from baculovirus-infected Trichoplusia ni (T. ni). The protein is glycosylated and exhibits competitive, high-affinity antagonism (Ki = 0.8 nM) versus alpha-MSH in cell-based assays employing B16F10 cells. Association state analysis by analytical ultracentrifugation reveals that agouti exists in a monomer--dimer plus aggregate equilibrium at low micromolar concentrations. Data from secondary structure studies indicate that the protein is highly stable to thermal denaturation. Enzymatic digestion to probe disulfide bond arrangement yielded a discrete C-terminal (Val 83-Cys 131) domain. The isolated highly cysteine-rich C-terminal domain retains alpha-MSH antagonism equipotent with mature agouti. This bioactive domain contains all 10 cysteines which exhibit sequence homology when aligned with several conotoxins.

The loss of female sex pheromone after mating in the corn earworm moth Helicoverpa zea: identification of a male pheromonostatic peptide.

Female moths often become depleted of sex pheromone after mating as the various components of virgin behavior are switched off. In examining a potential male contribution to these events in the corn earworm moth Helicoverpa zea, we have characterized a basic polypeptide from the tissues producing (accessory glands) and storing (duplex) the seminal fluids. The peptide evokes the depletion of sex pheromone when injected into virgin females. This pheromonostatic peptide (PSP) is 57 amino acids long and contains a single disulfide bridge. It is blocked at the N terminus with pyroglutamate and at the C terminus by amidation. As little as 23 ng of peptide evokes the near-complete depletion of pheromone in decapitated (neck-ligated) females that had been injected with pheromone biosynthesis-activating neuropeptide. Activity is approximately 15-fold less in intact virgins, showing that the head limits the expression of activity in these injected females. Females mated to surgically impaired males, capable of producing a spermatophore but not transferring spermatozoa or seminal fluids, are depleted of pheromone by injected peptide. Females whose abdominal nerve cords have been severed are not depleted of pheromone after mating. Thus, neural signals either descending or ascending via the nerve cord are required for the depletion of pheromone after mating. PSP, from the seminal fluids, may participate in this process by direct or indirect action on the glandular tissue; if so, it represents an unusual mechanism in insects for the regulation by seminal fluids of postmating reproductive behavior.

Characteristics of endogenous peptides eluted from the class I MHC molecule HLA-B7 determined by mass spectrometry and computer modeling.

Microcapillary HPLC electrospray ionization tandem mass spectrometry was used to sequence 15 peptides eluted from HLA-B7. Sequence alignment implicated four peptide positions in specific interactions with the class I molecule, and their importance was confirmed using synthetic peptides. Because no crystal structure for HLA-B7 was available, computer-assisted modeling was used to understand novel aspects of peptide binding specificity and to accurately predict the effect of defined changes in peptide structure. The results demonstrate that mass-spectrometric sequencing coupled with computer-assisted modeling can be used in the absence of a crystal structure to make accurate predictions concerning requirements for peptide binding to class I molecules. These techniques may be valuable to predict or engineer T cell epitopes.

Isolation and identification of a new diuretic peptide from the tobacco hornworm, Manduca sexta.

A 30-amino acid diuretic peptide was isolated from the corpora cardiaca-corpora allata complexes and, separately, from medial neurosecretory cells of the Sphingid moth, Manduca sexta. The peptide was found to have the following sequence, determined by automated Edman degradation and mass spectrometry: SFSVNPAVDILQHRYMEKV AQNNRNFLNRV-NH2. We have named the peptide Mas-DP II. The peptide was synthesized and shown to possess diuretic activity in decapitated moths. Mas-DP II is related by sequence homology to a 41-amino acid diuretic peptide identified previously from M. sexta, and it belongs to the family of corticotropin releasing factor-like peptides.