BackgroundRelationship between the level of repetitiveness in genomic sequence and genome size has been investigated by making use of complete prokaryotic and eukaryotic genomes, but relevant studies have been rarely made in virus genomes.ResultsIn this study, a total of 257 viruses were examined, which cover 90% of genera. The results showed that simple sequence repeats (SSRs) is strongly, positively and significantly correlated with genome size. Certain repeat class is distributed in a certain range of genome sequence length. Mono-, di- and tri- repeats are widely distributed in all virus genomes, tetra- SSRs as a common component consist in genomes which more than 100 kb in size; in the range of genome < 100 kb, genomes containing penta- and hexa- SSRs are not more than 50%. Principal components analysis (PCA) indicated that dinucleotide repeat affects the differences of SSRs most strongly among virus genomes. Results showed that SSRs tend to accumulate in larger virus genomes; and the longer genome sequence, the longer repeat units.ConclusionsWe conducted this research standing on the height of the whole virus. We concluded that genome size is an important factor in affecting the occurrence of SSRs; hosts are also responsible for the variances of SSRs content to a certain degree.

We provide a convenient method to construct photo-responsive poly(carbonate)s via ring-opening polymerization of cyclic carbonates followed by azide–alkyne click chemistry.

Light‐responsive poly(carbonate)s PEG113‐b‐PMPCn‐SP were synthesized via copper catalyzed azide‐alkyne cycloaddition reaction between azide‐modified spiropyran (SP‐N3) and amphiphilic copolymer PEG113‐b‐PMPCn. PEG113‐b‐PMPC25‐SP can self‐assemble to biocompatible micelles with an average diameter of ∼96 nm and a critical aggregation concentration of 0.0148 mg mL−1. Under 365 nm UV light irradiation, the characteristic absorption intensity of merocyanine (MC) progressively increased and most of the micellar aggregations were disrupted within 10 min, suggesting the completion of the transformation of hydrophobic SP to hydrophilic MC. Subsequent exposuring the micelles to 620 nm visible light, spherical micelles aggregated again. The light‐controlled release and re‐encapsulation behaviors of coumarin 102‐loaded micelles were further investigated by fluorescence spectroscopy. This study provides a convenient way to construct smart poly(carbonate)s nanocarriers for controlled release and re‐encapsulation of hydrophobic drugs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 750–760

Photo-responsive block copolymer mPEG-b-poly(Tyr)-g-NB was prepared by introduction of o-nitrobenzyl ester group into the side chain of amphiphilic poly(ethylene glycol)-b-poly(α-hydroxy acids) (mPEG-b-poly(Tyr)) containing pendent alkynyl group via copper-catalyzed azide-alkyne cycloaddition reaction. The amphiphilic mPEG-bpoly(Tyr) was synthesized via the ring-opening polymerization of O-carboxyanhydrides, with monomethoxy poly (ethylene glycol) (mPEG) as macroinitiator. The molecular structure, self-assembly, and photo-controlled release of the obtained mPEG-b-poly(Tyr)-g-NB were thoroughly investigated. mPEG-b-poly(Tyr)-g-NB could self-assemble into spherical micelles in water and showed disassembly under UV light irradiation, which was demonstrated by means of UV-vis spectroscopy, scan electron microscopes, and dynamic light scattering measurement. Fluorescence emission measurements demonstrated that Nile red, encapsulated by micelles, can be released upon UV irradiation. This study provides a convenient way to construct smart poly(α-hydroxy acids)-based nanocarriers for controlled release of hydrophobic drugs.