Understanding and controlling vesicle shapes is fundamental challenge in biophysics and materials design. In this paper, we employ the Monte Carlo method to investigate the shape of soft vesicle ...induced by semiflexible polymer outside in two dimensions. The effect of bending stiffness κ of polymer and the strength εVP of attractive interaction between vesicle and polymer on the shape of vesicle is discussed in detail in the present paper. It is found that the shape of vesicle is influenced by κ and εVP. Typical shape of vesicles is observed, such as circular, cigar-like, double vesicle, and racquet-like. To engineer vesicle shape transformations is helpful for exploiting the richness of vesicle geometries for desired applications.
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Self-assembly behavior of semiflexible polymers on rigid spherical shell is investigated using the molecular dynamics (MD) simulation method. We find that the conformation of ...semiflexible polymers depends on the length of polymers and bending energy of polymer chains. For moderate adhesive strength and bending energy, the polymers aggregate into multiple clusters, each of which contains several parallel chains. Simultaneously, the self-assembly conformations, volley-ball, helical and tennis-ball state, form on spherical shell depend on the number of clusters. We quantify the self-assembly conformation and analysis its physical mechanics of formation. This work may provide a theoretical foundation for the future theories of conformation prediction and material fabrication.
In this work, the conformational behaviors of ring polyelectrolyte in tetravalent salt solutions are discussed in detail through molecular dynamics simulation. For simplification, here we have ...neglected the effect of the twisting interaction, although it has been well known that both bending and twisting interactions play a deterministic in the steric conformation of a semiflexible ring polymer. The salt concentration CS and the bending energy b take a decisive role in the conformation of the ring polyelectrolyte (PE). Throughout our calculations, the b varies from b = 0 (freely joint chain) to b = 120. The salt concentration CS changes in the range of 3.56 × 10−4 M ≤ CS ≤ 2.49 × 10−1 M. Upon the addition of salt, ring PE contracts at first, subsequently re-expands. More abundant conformations are observed for a semiflexible ring PE. For b = 10, the conformation of semiflexible ring PE shifts from the loop to two-racquet-head spindle, then it condenses into toroid, finally arranges into coil with the increase of CS. As b increases further, four phase transitions are observed. The latter two phase transitions are different. The semiflexible ring PE experiences transformation from toroid to two racquet head spindle, finally to loop in the latter two phase transitions. Its conformation is determined by the competition among the bending energy, cation-bridge, and entropy. Combined, our findings indicate that the conformations of semiflexible ring PE can be controlled by changing the salt concentration and chain stiffness.
We study the process of a semiflexible polymer chain adsorption on to planar surface by the dynamic Monte Carlo (DMC) method, based on the 3D off-lattice model. Both the strength of attractive ...monomer-surface interaction (ε
) and bending energy (b) have pronounced effect on the adsorption and shape of semiflexible polymer chain. The semiflexible polymer can just fully adsorb on to the surface at certain ε
, which is defined as critical ε
The essential features of the semiflexible polymer adsorption on to surface are that (i) the critical ε
increases with increase in b; (ii) the shape of the fully adsorbed semiflexible polymer chain is film-like toroid, and the toroid becomes more and more perfect with increase in b In addition, the size of toroid and the number of turns of toroid can be controlled by the b and ε
.
Wrapping and unwrapping behaviors of double-stranded DNA around a positively charged nanosphere in solution are studied by using the coarse-grained molecular dynamics (CGMD) simulation method. When ...monovalent, divalent and trivalent anions are added to the DNA-nanosphere complex solution, double-stranded DNA binds with a nanosphere owing to strong electrostatic attraction. However, when tetravalent anions are added to the DNA-nanosphere complex solution, local charge inversion is observed for a high anion concentration of tetravalent anions and the double-stranded DNA can be unwrapped from the nanosphere because of the local charge inversion near the nanosphere. Moreover, the helical structure of DNA is damaged when double-stranded DNA wraps around the nanosphere and the helical structure can be rebuilt when the double-stranded DNA unwraps from the nanosphere. This study can help us understand how to control the release of DNA in DNA-nanosphere complexes.
A series of chalcogenide compounds with various compositions, i.e. , octanuclear or tetranuclear Zn–S clusters, have been synthesised in a straighforward manner. Different fused-ring aromatic ligands ...were used as capping ligands and the corresponding zero-dimensional (0D) products were obtained. On the other hand, use of bridging ligands led to a family of one-dimensional (1D) coordination polymers, and an in situ ligand reaction has been observed in Zn 8 S(SC 6 H 5 ) 13 L 1 (H 2 O)·2H 2 O (L = 3-carboxypryidyl) due to the hydrolysis of the cyano group of 3-pyridinecarbonitrile. A very rare 1D helical-chain structure was observed in Zn 4 (SC 6 H 5 ) 8 L 1 (L = 4,4′-bipyridyl), providing evidence of the character of bridging organic ligands in the corresponding crystalline materials. First-principles calculations on Zn 4 (SC 6 H 5 ) 8 L 1 (L = 4,4′-bipyridyl) further revealed that the two cluster units could rotate freely about the C–C single bond over a broad range, eventually leading to the formation of a one-dimensional helical structure.
A series of chalcogenide compounds with various compositions,
i.e.
, octanuclear or tetranuclear Zn-S clusters, have been synthesised in a straighforward manner. Different fused-ring aromatic ligands ...were used as capping ligands and the corresponding zero-dimensional (0D) products were obtained. On the other hand, use of bridging ligands led to a family of one-dimensional (1D) coordination polymers, and an
in situ
ligand reaction has been observed in Zn
8
S(SC
6
H
5
)
13
L
1
(H
2
O)·2H
2
O (L = 3-carboxypryidyl) due to the hydrolysis of the cyano group of 3-pyridinecarbonitrile. A very rare 1D helical-chain structure was observed in Zn
4
(SC
6
H
5
)
8
L
1
(L = 4,4′-bipyridyl), providing evidence of the character of bridging organic ligands in the corresponding crystalline materials. First-principles calculations on Zn
4
(SC
6
H
5
)
8
L
1
(L = 4,4′-bipyridyl) further revealed that the two cluster units could rotate freely about the C-C single bond over a broad range, eventually leading to the formation of a one-dimensional helical structure.
A series of Zn-S clusters have been synthesised and a very rare 1D helical structure was illustrated by first-principles calculations.
Background & Aims Reports on the association between dietary fiber intake and risk of colorectal adenoma (CRA), the precursor of colorectal cancer, have been inconsistent. We conducted a ...meta-analysis of case-control and cohort studies to analyze this association. Methods We searched the MEDLINE and EMBASE databases to identify relevant studies published through July 2013. A random-effects model was used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs) for associations between fiber intake and CRA risk. Heterogeneity among studies was assessed using the Cochran Q and I2 statistics. Results Our meta-analysis included 20 studies involving 10,948 subjects with CRA. The SRRs of CRA for total dietary fiber were 0.72 (95% CI, 0.63–0.83) in a high- vs low-intake analysis and 0.91 (95% CI, 0.87–0.95) per 10-g/day increase in fiber intake in a dose-response model. Subgroup analyses indicated a significant inverse association between total fiber intake and CRA risk in case-control studies (SRR, 0.66; 95% CI, 0.56–0.77), but not in cohort studies (SRR, 0.92; 95% CI, 0.76–1.10). The SRRs of CRA were 0.84 for fruit fiber (95% CI, 0.76–0.94; n = 6 studies), 0.93 for vegetable fiber (95% CI, 0.84–1.04; n = 6 studies), and 0.76 for cereal fiber (95% CI, 0.62–0.92; n = 9 studies) in high- vs low-intake analyses. Conclusions Our findings support the hypothesis that high dietary fiber intake is associated inversely with CRA risk. Further studies with prospective designs that use validated questionnaires and control for important confounders are warranted.
► No study carried out on the combined thermal-Fe(II)–S2O82− oxidation pretreatment. ► Sludge dewaterability was enhanced by Fe(II)–S2O82− oxidation in mild temperature. ► 94–96% CST reduction ...efficiency was obtained within the first 5min. ► Tyrosine and tryptophan protein-like matters in EPS mainly affected the dewatering. ► The treatment destroyed EPS, releasing EPS-bound water and interstitial water.
The potential benefits of Fe(II)–activated persulfate (S2O82−) oxidation under mild temperature in enhancing the dewaterability of waste activated sludge were investigated. Capillary suction time (CST) was used to characterize sludge dewatering. Zeta potential, particle size distribution, three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy, fourier-transformed infrared (FT-IR) spectroscopy and scanning electronic microscopy (SEM) were employed to explore influencing mechanisms. The results indicated that the dewaterability was deteriorated with single thermal treatment, but significantly enhanced in the presence of Fe(II)–S2O82− oxidation and further advanced together with thermal treatment. EEM and FT-IR analysis indicated that combined thermal and Fe(II)–S2O82− oxidation pretreatment led to degrading of tyrosine and tryptophan protein-like substances in extracellular polymeric substances (EPS) and cleavage of linkages in polymeric backbone. SEM images further revealed the rupture of sludge flocs at the colloidal scale, which contributed to the release of EPS-bound water and interstitial water trapped between flocs, and subsequent enhanced dewaterability.
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