Kangaroo endogenous retrovirus (KERV) forms megasatellite DNA with a simple repetition pattern in which the provirus structure is retained.

The kangaroo endogenous retrovirus (KERV) was previously reported to have undergone a rapid copy number increase in the red-necked wallaby; however, the mode of amplification was left to be clarified. The present study revealed that the long terminal repeat (LTR) (0.6 kb) and internal region (2.0 kb) of a provirus are repeated alternately, forming megasatellite DNA which we named kervRep. This repetition pattern was the same as that observed for walbRep, megasatellite DNA originating from another endogenous retrovirus. Their formation process can be explained using a simple model: pairing slippage followed by homologous recombination. This model features that the initial step is triggered by the presence of two identical sequences within a short distance; the possession of LTRs by endogenous retroviruses fulfills this condition. The discovery of two cases suggests that formation of this type of satellite DNA is one of non-negligible effects of endogenous retroviruses on their host genomes.

Direct Synthesis of Thermally Stable Semiaromatic Polyamides by Bulk Polymerization Using Aromatic Diamines and Aliphatic Dicarboxylic Acids.

Semiaromatic polyamides were directly synthesized by bulk polycondensation of aliphatic dicarboxylic acids (with 5, 6, 7, and 10 carbon numbers) and aromatic diamines (4,4'-oxydianiline and 4,4'-diaminodiphenylmethane) under natural pressure. In addition, copolyamides were successfully obtained by the copolymerization of aliphatic dicarboxylic acids, aromatic diamines, and biobased amino acid, 4-aminohydrocinnamic acid. The obtained polyamides had relatively high inherent viscosity values of 0.35-0.76 dL/g. The obtained polyamides exhibited good thermal stability with T d5% in the range of 316-416 °C, even when incorporated with aliphatic methylene units. In particular, some copolyamides (2AO, 2PO, and 2GM) had high T g values of 150, 158, and 156 °C and relatively low T m values of 277, 288, and 234 °C, respectively, which may be preferable thermal properties for melt-drawing processes.

Controlled Synthesis of Poly[(3-alkylthio)thiophene]s and Their Application to Organic Field-Effect Transistors.

Regioregular polythiophenes have been widely used in organic electronic applications due to their solution processability with chemical modification through side chain engineering, as well as their microstructural organization and good hole transport properties. Here, we introduce alkylthio side chains, (poly[(3-alkylthio)thiophene]s; P3ATTs), with strong noncovalent sulfur molecular interactions, to main chain thienyl backbones. These P3ATTs were compared with alkyl-substituted polythiophene (poly(3-alkylthiophene); P3AT) variants such that the effects of straight (hexyl and decyl) and branched (2-ethylhexyl) side chains (with and without S atoms) on their thin-film morphologies and crystalline states could be investigated. P3ATTs with linear alkylthio side chains (P3HTT, hexylthio; P3DTT, decylthio) did not attain the expected higher organic field-effect transistor (OFET) mobilities with respect to P3HT (hexyl) and P3DT (decyl) mainly due to their lower regioregularity (76-78%), although P3ATTs exhibit an enhanced tendency for aggregation and compact molecular packing, as indicated by the red-shifting of the absorption spectra and the shortening of the π-π stacking distance, respectively. Moreover, the loss of regioregularity issue can be solved by introducing more soluble 2-ethylhexylthio branched side chains to form poly[3-(2-ethylhexylthio)thiophene] (P3EHTT), which provides enhanced crystallinity and efficient charge mobility (increased by up to a factor of 3) with respect to the poly(2-ethylhexylthiophene) (P3EHT) without S atoms in the side moieties. This study demonstrates that the presence of side chain alkylthio structural motifs with nonbonded interactions in polythiophene semiconductors has a beneficial impact on the molecular conformation, morphologies, structural packing, and charge transport in OFET devices.