A New Approach through the Eye of a Needle and Its Potential Application in Bioscience

Putting the thread through the eye of a needle is a very ordinary issues in daily life. The mechanism of putting the thread through the eye of a needle is quite similar to threading a series of polymer chains through synthetic macrocycle in bioscience. A new rubbing approach to thread through the eye of a needle was proposed in this paper, and its potential application in the fields of biomechanics and mechanobiology to mimic the micro scale assembly processes was discussed.     

Barrier height of free energy on confined polymer translocation through a short nano-channel

The translocation of a confined polymer chain through a nano-channel has been simulated by using two-dimensional bond fluctuation model (BFM) with Monte Carlo dynamics. It is found that the trapping time for the polymer chain to overcome the free energy barrier during the translocation, tautrap, depends exponentially on the chain length N and the channel length M, respectively. The results suggest that the barrier height of free energy depends linearly on N and M, which is different from that predicted for the Gaussian chain.     

Synthesis, structures and luminescence properties of two new Zn(II) coordination compounds incorporating the 5-(4-pyridyl)tetrazolate spacer ligand

The hydrothermal reaction of ZnCl₂ with 5-(4-pyridyl)tetrazole afforded the 2D metal-organic coordination framework [Zn(OH)(4-ptz)] (1) and the mononuclear complex [Zn(4-ptz)₂(H₂O)₄]?2(H₂O) (2) [4-ptz = 5-(4-pyridyl)-tetrazolate]. Compound 1 consists of a zig-zag bidimensional network formed by rectangular (4,4) grid sheets. Molecules of 2 form a 3D extended network of hydrogen bonding involving water molecules and the tetrazolate ligand. In addition, compound 1 exhibits strong fluorescence at room temperature in the solid state.     

Development of Direct Grafting on Cyclic Olefin Copolymers to Improve Hydrophilicity by Using Bioactive Polymers

ObjectivesTo improve the hydrophilicity of cyclic olefin copolymer, a simple and rapid method using two-stage with ultraviolet irradiation was developed in order to graft a bioactive polymer on the surface of these polymers.Materials and MethodsA bioactive polymer, poly(sodium styrene sulfonate) was grafting in two steps on the cyclic olefin copolymer surface. The process consists to activate the surface with ozone and grafting to under UV irradiation in presence of sodium styrene sulfonate. The presence of polymer on the surfaces was characterized by water contact angle, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy and the quantity of polymer grafted was determined by a colorimetric method.ResultsFirst, the time of UV irradiation for the grafting was studied. The results showed that the maximum grafting rate is reached after 60 minutes of reaction. Second, the influence of the presence of additive on the grafting was investigated. The degree of grafting is significantly reduced compared to a sample without additive.ConclusionWe have developed a simple and fast method to graft a hydrophilic and bioactive polymer covalently to a COC surface.     

One novel dichromato-bridged Nickel(II) polymeric complex: formation of metal-oxygen chain structure

A novel one-dimensional Ni(II) coordination polymer [Ni(C₆H₈N₂)₂Cr₂O₇]_n (1) has been synthesised and characterised by elemental analyses, spectroscopic and single crystal X-ray diffraction study. Single crystal X-ray analysis revealed that the [Ni(C₆H₈N₂)₂]²⁺ cations are connected by μ_1,5 dichromato bridges forming infinite zig-zag chain along b-axis.     

Gene expression profile of human mesenchymal stem cells during osteogenesis in three-dimensional thermoreversible gelation polymer

This study attempted to characterize the ability of thermoreversible gelation polymer (TGP) to induce differentiation of human mesenchymal stem cells (hMSC) into osteoblasts. Using a long oligo microarray system consisting of 3760 genes, we compared the expression profiles of the cells in 2-dimensional (2D) culture, 3D culture in collagen gel, and 3D culture in TGP with or without osteogenic induction. Compared to 2D culture, the gene expression profile of hMSC showed almost the same pattern in TGP without osteogenic induction, but 72% of genes (2701/3760) were up-regulated in collagen gel. With osteogenic induction, hMSC showed higher ALP activity and osteocalcin production in TGP as compared to 2D culture. Moreover, up-regulation and down-regulation of osteogenic genes were augmented in 3D culture in TGP as compared to 2D culture. As TGP is chemically synthesized and completely free from pathogen such as prion in bovine spongiform encephalopathy, these results suggest that TGP could be applied clinically to induce osteogenic differentiation of hMSC.     

CO2 bioconversion using carbonic anhydrase (CA): Effects of PEG rigidity on the structure of bio-mineralized crystal composites

The combined effect of both carbonic anhydrase (CA) and the rigidity of polyethylene glycol (PEG) were found to assist the bio-mineralized crystallization behavior of CO₂ differentially. In this study, different forms of magnetically responsive calcium carbonate (CaCO₃) crystal composites were successfully formed from gaseous CO₂ by using the different forms of polyethylene glycols (PEGs) in a constant CO₂ pressure controlled chamber. Polygonal particles were produced with more rigid polymer chains (branched PEG), whereas less rigid polymer chains (PEG) induced the formation of ellipsoidal particles. However, no morphological changes occurred without the presence of CA.     

Dynamic simulations of potentially auxetic liquid-crystalline polymers incorporating swivelling mesogens

Dynamic simulations under stress were carried out on a series of main-chain polymers containing two types of mesogen. One mesogen is orientated in-line with the chain (end-to-end) and the second (swivelling) has the main chain passing at right angles through it. Under strain the swivelling mesogens are expected to rotate, pushing apart the neighbouring chains. Polymers incorporating 50% of both mesogens showed a reduced Poisson's ratio. In particular, swivelling mesogens of seven rings length produced a negative Poisson's ratio, and thus should be auxetic. In contrast, polymers containing only end-to-end mesogens had relatively high Poisson's ratios of 0.53–0.59.     

Nitric oxide reduces sickle hemoglobin polymerization: potential role of nitric oxide-induced charge alteration in depolymerization

We previously demonstrated that inhaling nitric oxide (NO) increases the oxygen affinity of sickle red blood cells (RBCs) in patients with sickle cell disease (SCD). Our recent studies found that NO lowered the P₅₀ values of sickle hemoglobin (HbS) hemolysates but did not increase methemoglobin (metHb) levels, supporting the role of NO, but not metHb, in the oxygen affinity of HbS. Here we examine the mechanism by which NO increases HbS oxygen affinity. Because anti-sickling agents increase sickle RBC oxygen affinity, we first determined whether NO exhibits anti-sickling properties. The viscosity of HbS hemolysates, measured by falling ball assays, increased upon deoxygenation; NO treatment reduced the increment. Multiphoton microscopic analyses showed smaller HbS polymers in deoxygenated sickle RBCs and HbS hemolysates exposed to NO. These results suggest that NO inhibits HbS polymer formation and has anti-sickling properties. Furthermore, we found that HbS treated with NO exhibits an isoelectric point similar to that of HbA, suggesting that NO alters the electric charge of HbS. NO–HbS adducts had the same elution time as HbA upon high performance liquid chromatography analysis. This study demonstrates that NO may disrupt HbS polymers by abolishing the excess positive charge of HbS, resulting in increased oxygen affinity.     

Artificial humification of lignin architecture: Top-down and bottom-up approaches

Humic substances readily identifiable in the environment are involved in several biotic and abiotic reactions affecting carbon turnover, soil fertility, plant nutrition and stimulation, xenobiotic transformation and microbial respiration. Inspired by natural roles of humic substances, several applications of these substances, including crop stimulants, redox mediators, anti-oxidants, human medicines, environmental remediation and fish feeding, have been developed. The annual market for humic substances has grown rapidly for these reasons and due to eco-conscious features, but there is a limited supply of natural coal-related resources such as lignite and leonardite from which humic substances are extracted in bulk. The structural similarity between humic substances and lignin suggests that lignocellulosic refinery resulting in lignin residues as a by-product could be a potential candidate for a bulk source of humic-like substances, but structural differences between the two polymeric materials indicate that additional transformation procedures allowing lignin architecture to fully mimic commercial humic substances are required. In this review, we introduce the emerging concept of artificial humification of lignin-related materials as a promising strategy for lignin valorization. First, the core structural features of humic substances and the relationship between these features and the physicochemical properties, natural functions and versatile applications of the substances are described. In particular, the mechanism by which humic substances stimulate the growth of plants and hence can improve crop productivity is highlighted. Second, top-down and bottom-up transformation pathways for scalable humification of small lignin-derived phenols, technical lignins and lignin-containing plant residues are described in detail. Finally, future directions are suggested for research and development of artificial lignin humification to achieve alternative ways of producing customized analogues of humic substances.