X-ray Intraday Variability of HBL Blazars with XMM-Newton

We present an extensive study on the X-ray intraday variability of ten TeV-emitting high synchrotron peaked blazars (HBLs): 1ES 0229+200, 1ES 0414+009, PKS 0548-322, 1ES 1101-232, 1H 1219+301, H 1426+428, Mrk 501, 1ES 1959+650, PKS 2005-489, and 1ES 2344+514 made with twenty-five XMM-Newton pointed observations during its operational period. Intraday variability has been estimated in three energy bands: soft (0.3--2 keV), hard (2--10 keV) and total (0.3--10 keV). Although seven out of these ten TeV HBLs exhibited some intraday variability at three-sigma levels no major variations exceeding six percent were detected. We explored the spectral properties of the sample by extracting the hardness ratio from the soft and hard bands; no significant variations in the hardness ratio were observed in any source. We performed power spectral density analyses on the variable light-curves by fitting power-laws, yielding slopes lying in the range from 1.11 to 2.93 for different HBLs. We briefly discuss possible emission mechanisms and carry out rough estimates for magnetic fields, electron Lorentz factors and emission region sizes for seven of these HBLs.Comment: Accepeted for publication in ApJ, 33 pages, 14 figures, 5 table

Effect of PEGylation on protein hydrodynamics

We studied the effect of PEGylation on protein hydrodynamic behavior using hen egg-white lysozyme (HEWL) as a model protein. HEWL was PEGylated with a linear, 20 kDa PEG using reductive amination to produce PEG1-, PEG2-, and PEG3-HEWL. Near- and far-UV–CD spectroscopy revealed no significant effect of PEGylation on HEWL higher order structure. SDS–PAGE, mass spectrometry, online static light scattering (SLS) and sedimentation velocity analytical ultracentrifugation (SV-AUC) were employed to characterize the heterogeneity and molecular weights of the purified PEG-HEWL molecules, the results of which underscored the importance of using first-principle based methods for such analyses along with the underlying complexities of characterizing PEG–protein conjugates. Hydrodynamic characterization of various linear and branched PEGs (5–40 kDa) and PEG-HEWL molecules was performed using dynamic light scattering (DLS) and SV-AUC. The PEG polymer exhibited a random-coil conformation in solution with the Mw ∝ Rhn scaling relationship yielding a scaling exponent (n) = 2.07. Singly branched PEGs were also observed to exhibit random-coil behavior with Stokes radii identical to those of their linear counterparts. SV-AUC studies of PEG-HEWL showed PEG has a “parachute” like effect on HEWL, and dramatically increases the frictional drag; PEG-HEWL also exhibited random-coil-like characteristics in solution (n = 1.8). The sedimentation coefficient (s) of PEG-HEWL remained invariant with increasing degree of PEGylation, indicating that the increase in molecular mass from PEG was compensated by an almost equivalent increase in frictional drag. Our studies draw caution to using SV-AUC for the characterization of size heterogeneity of PEG–protein mixtures