Per- and Polyfluoroalkyl Substances in Human Serum Samples of Selected Populations from Ghana

The aims of this study were to assess serum concentrations of per- and polyfluoroalkyl substances (PFASs) in selected populations from Ghana, including workers engaged in the repair of electronic equipment (ERWs), and to elucidate PFAS concentrations in relation to blood mercury concentrations (B-Hg) as a biomarker of seafood consumption. In all, 219 participants were recruited into the study, of which 26 were women and 64 were ERWs. Overall, the PFAS concentrations were low. The most abundant components were perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonic acid (PFHxS). Women had generally lower PFAS concentration than men. The ERWs had statistically significantly higher concentrations of perfluorooctanoate (PFOA), which was associated with the concentration of tin in urine. This could indicate exposure during soldering. The concentration of B-Hg was associated with several of the PFASs such as PFOA, PFOS and perfluoroheptane sulfonate (PFHpS). Additionally, the concentrations of perfluorodecanoic acid (PFDA) and perfluoroundecanoate (PFUnDA) were highly associated with the concentrations of B-Hg. It is noteworthy that the linear isomer of PFHxS was strongly associated with B-Hg while the branched isomers of PFHxS were not. In conclusion, the PFAS concentrations observed in the present study are low compared to other populations previously investigated, which also reflects a lower PFAS exposure within the Ghanaian cohorts. ERWs had significantly higher PFOA concentrations than the other participants. Several PFASs were associated with B-Hg, indicating that seafood consumption may be a source of PFAS exposure.

Spectroscopy of van der Waals molecules: Isomers and vibrational predissociation

The inert-gas-halogen complexes have been studied for several decades by jet spectroscopy. Much of the seemingly bizarre behavior has become understandable in terms of two virtually isoenergetic isomer forms. The recently recognized linear isomer of Ar–I2 has a virtually continuous B ¬ X excitation spectrum. It also undergoes a very rapid vibrational predissociation, and suffers no electronic quenching from the B state. The well-known T-shaped isomer shows slow vibrational predissociation, which is competitive with electronic quenching. The quenching distorts the vibrational distribution of the I2 B state photofragments, consequently leading to a false estimation of the T-shaped Ar–I2 (B) state dissociation energy. The binding energies for the T-shaped Ar–I2 (X) and Ar–I2 (B) are unambiguously determined from the recent dispersed fluorescence study, which are also in good accord with the ab initio calculation. We discuss aspects of pure vibrational laser-induced fluorescence of hydrogen fluoride complexes. We contrast the behavior of Ar–HF with Ne–HF and present new results for the vHF = 3 level of Ne–HF. PACS Nos.: 33.80Gj, 34.30th

Acyclo C-Nucleosides Analogues of Condensed 1,2,4-Triazines

1-Acyclo C-nucleosides of 7-methyl-10H-1,2,4-triazolo[3’,4’:3,4][1,2,4]triazino[5,6-b]indoles (9) have been prepared by cyclodehydrogenation of the sugar derivatives of 3-hydrazino-8-methyl-5H-1,2,4-triazino[5,6-b]indole (1). The respective linear isomer as 4 has been prepared by a dehydrative cyclization of the amides of 1. Acetylation of the sugar hydrazones and their cyclized products gave the per-N,O-acetyl derivatives. The molecular connectivity of the products was established by 1H, 13C, and 2D H ,H Cosy spectra.

Transfer of Free Polymannose-type Oligosaccharides from the Cytosol to Lysosomes in Cultured Human Hepatocellular Carcinoma HEPG2 Cells

Large, free polymannose oligosaccharides generated during glycoprotein biosynthesis rapidly appear in the cytosol of HepG2 cells where they undergo processing by a cytosolic endo H–like enzyme and a mannosidase to yield the linear isomer of Man5GlcNAc (Man[α1-2]Man[α1-2]Man[α1-3][Man α1-6]Man[β14]GlcNAc). Here we have examined the fate of these partially trimmed oligosaccharides in intact HepG2 cells. Subsequent to pulse–chase incubations with d-[2- 3H]mannose followed by permeabilization of cells with streptolysin O free oligosaccharides were isolated from the resulting cytosolic and membrane-bound compartments. Control pulse–chase experiments revealed that total cellular free oligosaccharides are lost from HepG2 cells with a half-life of 3–4 h. In contrast use of the vacuolar H+/ATPase inhibitor, concanamycin A, stabilized total cellular free oligosaccharides and enabled us to demonstrate a translocation of partially trimmed oligosaccharides from the cytosol into a membrane-bound compartment. This translocation process was unaffected by inhibitors of autophagy but inhibited if cells were treated with either 100 μM swainsonine, which provokes a cytosolic accumulation of large free oligosaccharides bearing 8-9 residues of mannose, or agents known to reduce cellular ATP levels which lead to the accumulation of the linear isomer of Man5GlcNAc in the cytosol. Subcellular fractionation studies on Percoll density gradients revealed that the cytosol-generated linear isomer of Man5GlcNAc is degraded in a membrane-bound compartment that cosediments with lysosomes.

Theoretical study of the PSi2 radical

G2 methodology has been used to characterize minima on both doublet and quartet potential energy surfaces of the PSi2 radical system. We found that for states with doublet spin multiplicity the most stable isomer is the cyclic 2A1. Linear isomers lie more than 24 kcal/mol above in energy. For the quartets the most stable state isomer is the cyclic 4A2, and the most stable linear isomer, i.e., Si-Si-P(4∑−), lies 10.68 kcal/mol higher in energy. The structural features of the various isomers characterized have been rationalized in terms of the bonding features of the molecular orbitals involved. Key words: ab initio, excited states, radical.