In this work, we investigate the effect of salt and water on plasticization and thermal properties of hydrated poly(diallyldimethylammonium chloride) (PDAC) and poly(sodium 4-styrenesulfonate) (PSS) assemblies via molecular dynamics simulations and modulated differential scanning calorimetry (MDSC). Commonly, both water and salt are considered to be plasticizers of hydrated polyelectrolyte assemblies. However, the simulation results presented here show that while water has a plasticizing effect, salt can also have an opposite effect on the PE assemblies. On one hand, the presence of salt ions provides additional free volume for chain motion and weakens PDAC-PSS ion pairing due to electrostatic screening, which contributes toward plasticization of the complex. On the other hand, salt ions bind water in their hydration shells, which decreases water mobility and reduces the plasticization by hydration. Our MDSC results connect the findings to macroscopic PE plasticization and the glass-transition-like thermal transition T under controlled PE hydration and salt content. This work identifies and characterizes the dual nature of salt both as plasticizer and hardener of PE assemblies and maps the interconnection of the influence of salt with the degree of hydration in the system. Our findings provide insight into the existing literature data, bear fundamental significance in understanding of hydrated polyelectrolyte assemblies, and suggest a direct means to tailor the mechanical characteristics of PE assemblies via interplay of water and salt.

Streptomyces sp. linear plasmids and linear chromosomes usually contain conserved terminal palindromic sequences bound by the conserved telomeric proteins Tap and Tp, encoded by the tap and tpg genes, respectively, as well as plasmid loci required for DNA replication in circular mode when the telomeres are deleted. These consist of iterons and an adjacent rep gene. By using PCR, we found that 8 of 17 newly detected linear plasmids in Streptomyces strains lack typical telomeric tap and tpg sequences. Instead, two novel telomeres in plasmids pRL1 and pRL2 from the eight strains and one conserved telomere in pFRL1 from the other strains were identified, while multiple short palindromes were also found in the plasmids. The complete nucleotide sequence of pRL2 revealed a gene encoding a protein containing two domains, resembling Tap of Streptomyces and a helicase of Thiobacillus, and an adjacent gene encoding a protein similar to Tpg of Streptomyces and a portion of the telomere terminal protein pTP of adenoviruses. No typical iterons-rep loci were found in the three plasmids. These results indicate an unexpected diversity of telomere palindromic sequences and replication genes among Streptomyces linear plasmids.Streptomyces species are gram-positive, high-GϩC, myceliumproducing eubacteria. Unlike the case for most eubacteria, linear plasmids and linear chromosomes are common in Streptomyces species (3,8,11,19,20,28). The linear plasmids vary in size between 12 kb (16) and 1,700 kb (19). Their telomeres contain long inverted repeat sequences of 44 bp (7) to 180 kb (21), and the 5Ј telomeric ends are linked covalently to terminal proteins (Tp) (1, 31). The telomeres of the ϳ8-Mb linear Streptomyces chromosomes are 46 bp to 1 Mb long (14,29). With the exceptions of the telomeres of the large linear plasmid SCP1 and the Streptomyces griseus linear chromosome (9, 18), Streptomyces linear plasmids and linear chromosomes usually contain conserved palindromic DNA sequences at their telomeres (13).Unlike the terminal protein-capped linear replicons of adenoviruses and bacteriophage ⌽29 (25), replication of Streptomyces linear plasmids starts at centrally located loci (27) and proceeds bidirectionally toward the telomeres (5). This leaves an ϳ280-nucleotide (nt) single-strand overhang at the 3Ј telomeric end of pSLA2 as a replication intermediate (5). To convert the 3Ј overhang to a double strand, the terminal 144 nt of the telomere contain short palindromes 1 to 5 (22), with palindromes 2/3 being bound by the conserved telomere-associated protein (Tap) to recruit the conserved telomere terminal protein (Tp) (1, 2).Streptomyces linear plasmids can also propagate in circular mode when the telomeres are deleted (5, 10, 24, 27). The centrally located locus for replication of pSLA2 consists of a rep-2 gene (encoding a DNA helicase) and its adjacent iterons within a transcribed rep-1 gene (6). The replication loci of plasmids SCP1 and pSLA2-L also consist of rep genes and different iteron sequences (10, 24). Such iterons-rep loci ...