Tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene resin as an efficient solid support for gel phase peptide synthesis

Various applications of the newly developed tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene resin are illustrated by the synthesis of model peptides, fully protected peptides, peptide amides and biologically important sequences. PS-TTEGDA resin was prepared by suspension polymerization of styrene and TTEGDA and functionalized with chloromethyl, 4-cholromethyl-3-nitro, aminomethyl, α-bromopropionyl, α-aminopropionyl, 4-bromomethyl 3-nitrobenzamido, 4-aminomethyl-3-nitrobenzamido groups. Peptide synthesis was carried out using these modified resins by standard solid phase methodology. Coupling and deprotection in this synthetic strategy went to near completion showing the positive role of hydrophilic and flexible crosslinking agent TTEGDA in facilitating gelphase reactions. The peptides were removed from the support by photolysis, trifluoroaceticacid (TFA) treatment,trans-esterification or ammonolysis in high purity and yield. The crude peptides were purified by column chromatography/FPLC and characterized by aminoacid analysis, sequencing or 1H-NMR

Revival of the magnetar PSR J1622-4950: observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation.Comment: Published in ApJ (2018 April 5); 13 pages, 4 figure

The SARAO MeerKAT 1.3 GHz Galactic Plane Survey

We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251\deg $\le l \le$ 358\deg and 2\deg $\le l \le$ 61\deg at $|b| \le 1.5\deg$). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8" and a broadband RMS sensitivity of $\sim$10--20 $\mu$ Jy/beam. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908--1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE HII region candidates are not true HII regions; and a large sample of previously undiscovered background HI galaxies in the Zone of Avoidance

The 1.28 GHz MeerKAT DEEP2 Image

We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one qb » ¢ 68 FWHM primarybeam area with θ = 7 6 FWHM resolution and s = m - n 0.55 0.01 Jy beam 1 rms noise. Its J2000 center position α = 04h 13m 26 4, δ = −80° 00′ 00″ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary-beam attenuation pattern, estimate telescope pointing errors, and pinpoint (u, v) coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion P(D) distribution from 0.25 to 10 μJy with counts of individual DEEP2 sources between 10 μJy and 2.5 mJy. Most sources fainter than S ∼ 100 μJy are distant star-forming galaxies (SFGs) obeying the far-IR/ radio correlation, and sources stronger than 0.25 μJy account for ∼93% of the radio background produced by SFGs. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson model for the evolution of SFGs based on UV and infrared data underpredicts our 1.4 GHz source count in the range -5 log Jy 4 [ ( )] S

The SARAO MeerKAT 1.3 GHz Galactic Plane Survey

We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251○ ≤l ≤ 358○ and 2○ ≤l ≤ 61○ at |b| ≤ 1 5). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8″ and a broadband RMS sensitivity of ∼10–20 μJy beam−1. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908–1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE H II region candidates are not true H II regions; and a large sample of previously undiscovered background H I galaxies in the Zone of Avoidance

The MeerKAT Galaxy Cluster Legacy Survey: I. Survey overview and highlights

Please abstract in the article.The South African Radio Astronomy Observatory (SARAO), the National Research Foundation (NRF), the National Radio Astronomy Observatory, US National Science Foundation, the South African Research Chairs Initiative of the DSI/NRF, the SARAO HCD programme, the South African Research Chairs Initiative of the Department of Science and Innovation.http://www.aanda.orghj2022Physic

Synthesis, characterization and application of tetraethylene glycol diacrylate crosslinked polystyrene support for gel phase peptide synthesis

Styrene and tetraethylene glycol diacrylate (TTEGDA) were copolymerized by the free radical aqueous suspension polymerization technique, employing toluene as the monomer diluent at 80°C. The resulting beads were functionalized by chloromethylation. The copolymer was characterized by IR and high-resolution solid-state 13C-NMR techniques. Scanning electron microscopy was employed to observe shape, size, and morphological features of the crosslinked bead copolymer. The swelling capacities of the copolymer were measured in various solvents. Reactivity of the amino functionalized polymer was compared with divinylbenzene-polystyrene (PS) resin. Stability of the copolymer was tested under various peptide synthetic conditions. High capacity chloromethyl TTEGDA-crosslinked PS was employed as a solid support in the synthesis of the hydrophobic peptide Boc(Ala-Leu-Ala)4-OMe. The coupling and deprotection steps in the synthetic scheme proceeded in near quantitative yields, supporting the positive role of the flexible and hydrophilic crosslinking agent. The fully protected 12-residue peptide was cleaved from the support by a transesterification procedure in 85% overall yield and characterized by thin-layer chromatography, amino acid analysis, and 1H-NMR

Synthesis of fully protected peptides on a tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene support with a photolytically detachable 2-nitrobenzyl anchoring group

1-Chloromethyl-2-nitro tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene resin was prepared by nitration of chloromethyl (4%) TTEGDA-crosslinked polystyrene resin and used as a photosensitive solid support for the preparation of fully protected peptides. C-protected amino acid esters were attached to resin (1) using large excess of amino acid ester and equivalent amount of triethylamine (TEA). After estimation of first amino acid attachment, the stepwise synthesis of the peptides was carried out using the symmetric anhydride procedure. The fully protected peptides were cleaved from the support by photolysis. The crude product was purified on a silica gel column and characterised by amino acid analysis and tlc

Solid phase synthesis of nuclear localization signal on a new PS-TTEGDA polymer support

1740-1746Tetraethyleneglycol diacrylate (2%) cross-linked polystyrene a highly solvating copolymer is used for the synthesis of the peptide. The peptide is grown from the hydroxymethyl functional site introduced into the resin. The peptide H-Ala-Ala-Ala-Lys-Lys-Asn-Ser-Leu-Ala-Leu-Ser-Leu-Thr-Ala-Asp-Gln-Met-Val-Ser-Ala-Leu-Leu is the sequence of the nuclear localization signal 1 and also the hormone binding domain of the human estrogen receptor (amino acids 302-320) with polyalanine at N-terminus. The C-terminal amino acid Fmoc-Leu is anchored using DCC and HOBt where the reagents are reacted in 4:4:3 ratio. The remaining amino acids are incorporated into this support following the standard solid-phase methodology of peptide synthesis. The completely deprotected peptide is cleaved from the resin using trifluoroacetic acid in 7h, isolated in solid form and purity is checked by HPLC. The peptide is characterised by amino acid analysis and MALDI TOF MAS. Biological studies reveal that the peptide is successful in binding three proteins of 73, 55 and 28 kiloDaltons from goat uterine cytosol

Gel-phase peptide synthesis on a new high-capacity tetraethyleneglycol diacrylate-crosslinked polystyrene support: synthesis of pardaxin 16-33

An insoluble but highly solvating copolymer composed of tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene has been prepared in beaded form by free-radical suspension polymerization of the monomers and employed as a new solid support for gel-phase peptide synthesis. This new polymer support has comparable physical and mechanical properties as that of the divinylbenzene (DVB)-crosslinked polystyrene support permitting identical manipulation such as shaking and filtration when used as a support for solid-phase peptide synthesis. This polystyrene-TTEGDA crosslinked polystyrene resin undergoes much more effective swelling and solvation than DVB-crosslinked polystyrene in a range of solvents with widely varying polarity which are commonly employed synthesis. The resin can be easily chloromethylated under controlled conditions to prepare resins of varying capacity ranging from low (0.15 meq/g) to high capacity (3.5meq/g). A high capacity resin with 1.5 meq/g chlorine capacity was used for synthesis of hydrophilic C-terminal 18-residue peptide of pardaxin from Pardachirus Pavoninus. The peptide was cleaved from the polymeric support by trifluoroacetic acid at 37°C and purified by Fast Protein Liquid Chromatography (FPLC). The purified peptide was shown to be homogeneous by HPLC and the identity of the 18-residue peptide was confirmed by amino acid analysis. The free peptide possesses a disordered conformation as revealed by the CD measurement