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Xiang-Yang Liu

Publications and source records attributed to Xiang-Yang Liu.

17 recordsLinked to original sources
PubMed2006

Architecture of fiber network: from understanding to engineering of molecular gels.

A new approach of engineering of molecular gels was established on the basis of a nucleation-initiated network formation mechanism. A variety of gel network structures can be obtained by regulating the starting temperature of the sol-gel transition. This enables us to tune the network from the spherulitic domains pattern to the extensively interconnected fibrillar network. As the consequence of fibrous network structure turning, desirable rheological and other in-use properties of the materials can be obtained accordingly. This approach of micro-/nanostructural fabrication may open up a new route for micro-/nanofunctional materials engineering in general.

Crystallography↗
PubMed2006

Interaction of 2-(2'-pyridyl)benzimidazolyl derivative ligands with group 12 metal ions: coordination, structures and luminescence.

The coordination chemistry of the group 12 metal ions with two 2-(2'-pyridyl)benzimidazolyl derivative ligands 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb) and 2-(2'-pyridyl)benzimidazolylbenzene (mb) has been investigated. The crystal structures of two coordination compounds (HgCl(2))(2)(tmb) and [Zn(mb)(2)(H(2)O)][ClO(4)](2) have been determined by single-crystal X-ray diffraction analysis which established the chelate bonding mode by the group 12 metal ions to the tmb or mb ligand. The luminescent response of tmb and mb toward group 12 metal ions, Zn(II), Cd(II) and Hg(II) has been examined by fluorescent titration experiments which established that the three group 12 metal ions have distinct luminescent response toward the tmb or mb ligand. The addition of the Hg(II) ion resulted in fluorescence quenching. In contrast, the addition of Zn(II) or Cd(II) led to a red shift and dramatic intensity increase of the emission spectrum of the ligand.

Journal Article↗
PubMed2006

How does bovine serum albumin prevent the formation of kidney stone? A kinetics study.

To attain a better understanding of the crystallization of calcium oxalate crystals under the influence of the protein bovine serum albumin, we examined not only the nucleation kinetics but also the structural synergy between the biomineral and the biosubstrate. It follows that during the crystallization process of calcium oxalate crystals bovine serum albumin inhibits the nucleation of calcium oxalate by increasing the kink kinetics barrier. The results of scanning electron microscopy and X-ray diffraction show, however, that bovine serum albumin promotes the formation of calcium oxalate dihydrate. Apart from this, bovine serum albumin facilitates the ordered calcium oxalate crystal assembly by suppressing the supersaturation-driven interfacial structure mismatch. The physics questions behind the mentioned effects have been addressed from the kinetics point of view. This may explain why bovine serum albumin plays an important role in suppressing urine stone formation.

Animals↗
PubMed2006

Real-time observation of fiber network formation in molecular organogel: supersaturation-dependent microstructure and its related rheological property.

Low-molecular mass organic gelators self-organizing into three-dimensional fiber networks within organic solvents have attracted much attention in recent years. However, to date, how the microstructure of fiber network is formed in a gelation process and the key factors that govern the topological structure of a gel network remain to be determined. In this work, we address these issues by investigating the in situ formation of the gel networks in the N-lauroyl-l-glutamic acid di-n-butylamide (GP-1)/propylene glycol (PG) system. By using optical microscopy, the time evolution of the gel network microstructure was investigated under various supersaturation conditions. It is found that supersaturation is one of the key factors that govern the topological structure of a gel network. In particular, the creation of the junctions turns out to be supersaturation-dependent. The rheological experiments further revealed the correlation between topological structure and mechanical properties. It suggests that the rheological properties can be effectively modified by tuning the microstructure topology of the gel network. Our results reported here provide new physical insight into the formation kinetics of a molecular gel. Furthermore, this work could be important in constructing and engineering a supramolecular structure for the purpose of applications.

Gels↗
PubMed2006

From surface self-assembly to crystallization: prediction of protein crystallization conditions.

A new criterion based on surface and volume diffusion kinetics was established to predict protein crystallization. Similar to the layer-by-layer crystal growth process of protein, the kinetics of the two-dimensional self-assembly of protein at the aqueous solution surface provides a convenient and reliable way to estimate the surface integration and the volume transport during protein crystallization. Both the surface and diffusion kinetics were estimated based on the protein self-assembly at the air/solution interface, which can be obtained by measuring the surface tension. A crystallization coefficient is found to provide an effective and reliable criterion to predict protein crystallization conditions. This criterion has been applied to lysozyme, concanavalin A and BSA crystallization, and it turns out to be very successful and more reliable than the second virial coefficient criterion.

Animals↗
PubMed2006

Colloidal phase transition driven by alternating electric field.

The transverse two-dimensional assembly of colloidal particles near an electrode surface subjected to ac polarization is studied by varying the frequency and field strength in the absence and presence of an added electrolyte. The variation of the translational and bond-orientational correlation functions with frequency suggests the existence of a hexatic phase in which the particles retain the remnants of the crystalline long-range orientational order, but has a liquidlike translational order. The electrohydrodynamic (EHD) flow is analyzed in the light of the existing theoretical models. The equilibrium distribution of particles is considered to be the resultant of the two opposing forces--Stoke's force due to EHD flow and the screened Coulomb interaction between the colloidal particles. Several features of the experimental results are discussed, such as the role played by the EHD flow in the particle aggregation, the dependence of the equilibrium interparticle separation on ionic strength, zeta potential, and particle size.

Journal Article↗
PubMed2006

[Construction of human growth hormone lentiviral vector and its expression in murine skeletal myoblasts].

The aim of this study is to construct a lentiviral vector encoding human growth hormone, and to achieve the long, efficient and stable expression in murine skeletal myoblasts. Primary skeletal myoblasts were isolated from Sprague-Dawley rats and cultured by enzymatic digestion. We tested them by Desmin immunohistochemistry stains and found their viability was up to 94% by Trypan blue. Human growth hormone (hGH) cDNA was subcloned into expression vector pLenti6/V5-D-TOPO to construct recombinant pLenti6/V5-hGH. The pLenti6/V5-hGH and the contructed pLenti6/V5-EGFP were transfected into murine skeletal myoblasts by the Lipofectamin 2000. Through counting by the Confocal Laser Scanning Microscope, we identified the transfection efficency. We added the blasticidin to the 6-well plate with lids and obtained stable myoblasts expressing hGH. The concentration of human growth hormone (hGH) in cell culture medium was detected by Radioimmunoassay (RIA). Polymerase Chain Reaction (PCR) and DNA sequence showed hGH cDNA had been correctly inserted into pLenti6/V5-D-TOPO vector. Bright green fluorescence of the transfected cells could be observed under the Confocal Laser Scanning Microscope after 24 h transfection with pLenti6/V5-EGFP plasmids, and the transfection rate reached 40%. The difference was distinct (P < 0.01) between the pLenti6/V5- hGH groups and control groups in the secretive level of human growth hormone. After 8 weeks, the expression of human growth hormone was still stable. Then, we validated the biological characterization of the rhGH by the enzyme-link immunosorbent assay (ELISA) of the Insulin-like growth factor I (IGF-1). These results demonstrate we have successfully constructed the recombinant pLenti6/V5-hGH plasmids and accomplished rhGH long, efficient and stable expression ectopic in skeletal muscle myoblasts.

Animals↗
PubMed2005

Architecture of a biocompatible supramolecular material by supersaturation-driven fabrication of its fiber network.

The architecture of a biocompatible organogel formed by gelation of a small molecule organic gelator, N-lauroyl-L-glutamic acid di-n-butylamide, in isostearyl alcohol was investigated based on a supersaturation-driven crystallographic mismatch branching mechanism. By controlling the supersaturation of the system, the correlation length that determines the mesh size of the fiber network was finely tuned and the rheological properties of the gel were engineered. This approach is of considerable significance for many gel-based applications, such as controlled release of drugs that requires precise control of the mesh size. A direct cryo-transmission electron microscopy (TEM) imaging technique capable of preserving the network structure was used to visualize its nanostructure.

Cryoelectron Microscopy↗
PubMed2005

Kinetics and template nucleation of self-assembled hydroxyapatite nanocrystallites by chondroitin sulfate.

Biomineralization is an important process, which is often assisted by biomolecules. In this paper, the effect of chondroitin sulfate on the crystallization of hydroxyapatite was examined quantitatively based on a generic heterogeneous nucleation model. It is found that chondroitin sulfate can suppress the supersaturation-driven interfacial structure mismatch between the hydroxyapatite crystal and the substrate and promote the formation of ordered hydroxyapatite nanocrystallite assemblies. The nucleation mechanism of self-aligned hydroxyapatite nanocrystallites was examined from the viewpoints of kinetics and interfacial structure and properties, which contributes to an understanding of the fundamentals of biomineralization of self-assembled structures. The results obtained from this study will provide a basic principle to design and fabricate highly orderly organic-inorganic hybrid materials.

Biocompatible Materials↗
PubMed2005

Investigation on the mechanism of crystallization of soluble protein in the presence of nonionic surfactant.

The mechanism of crystallization of soluble, globular protein (lysozyme) in the presence of nonionic surfactant C8E4 (tetraoxyethylene glycol monooctyl ether) was examined using both static and dynamic light scattering. The interprotein interaction was found to be attractive in solution conditions that yielded crystals and repulsive in the noncrystallizing solution conditions. The validity of the second virial coefficient as a criterion for predicting protein crystallization could be established even in the presence of nonionic surfactants. Our experiments indicate that the origin of the change in interactions can be attributed to the adsorption of nonionic surfactant monomers on soluble proteins, which is generally assumed to be the case with only membrane proteins. This adsorption screens the hydrophobic attractive force and enhances the hydration and electrostatic repulsive forces between protein molecules. Thus at low surfactant concentration, the effective protein-protein interaction remains repulsive. Large surfactant concentrations promote protein crystallization, possibly due to the attractive depletion force caused by the intervening free surfactant micelles.

Binding Sites↗
PubMed2005

Preferential solvation stabilization for hydrophobic polymeric nanoparticle fabrication.

Preferential solvation of polymer molecules and strong EPD-EPA (EPD, electron pair donor; EPA, electron pair acceptor) interaction between solvent and nonsolvent molecules were found to be of great significance in the fabrication of two kinds of aromatic polyimide (AP) nanoparticles. Surfactant free yet stable AP nanoparticles were prepared using a liquid-liquid phase separation method. The stability of the AP nanoparticles can be achieved by the solvation multilayer resulting from a solvation stabilization chain in the form of nonsolvent --> solvent --> AP (a --> b denotes that component b is solvated by component a). The significance of this stabilization chain was identified by many comparative experiments using different types of molecular probes. On the other hand, the formation of AP nanoparticles was found to be governed by a nucleation process and therefore the particle size is controlled by the nucleation rate. A very high level of supersaturation can be attained under the intensive local motions induced by ultrasound, resulting in a very high nucleation rate. This effect was found to be extremely useful in the fabrication of sub-50 nm AP nanoparticles.

Journal Article↗
PubMed2005

Topology evolution and gelation mechanism of agarose gel.

Kinetics as well as the evolution of the agarose gel topology is discussed, and the agarose gelation mechanism is identified. Aqueous high melting (HM) agarose solution (0.5% w/v) is used as the model system. It is found that the gelation process can be clearly divided into three stages: induction stage, gelation stage, and pseudoequilibrium stage. The induction stage of the gelation mechanism is identified using an advanced rheological expansion system (ARES, Rheometric Scientific). When a quench rate as large as 30 deg C/min is applied, gelation seems to occur through a nucleation and growth mechanism with a well-defined induction time (time required for the formation of the critical nuclei which enable further growth). The relationship between the induction time and the driving force which is determined by the final setting temperature follows the 3D nucleation model. A schematic representation of the three stages of the gelation mechanism is given based on turbidity and rheological measurements. Aggregation of agarose chains is promoted in the polymer-rich phase and this effect is evident from the increasing mass/length ratio of the fiber bundles upon gelation. Continuously increasing pore size during gelation may be attributed to the coagulation of the local polymer-rich phase in order to achieve the global minimum of the free energy of the gelling system. The gel pore size determined using turbidity measurements has been verified by electrophoretic mobility measurements.

Gels↗
PubMed2005

[Surgical treatment and prognosis of synchronous double primary lung cancer: a report of 31 cases].

BACKGROUND & OBJECTIVE: The idea of double primary lung cancer (DPLC) has been generally accepted. Recently, an increasing incidence of synchronous DPLC has been reported, while the diagnostic standard and treatment strategies remain to be improved. This study was to investigate effective surgical treatment, and prognosis of synchronous DPLC. METHODS: From Jan. 1983 to Apr. 2004, 31 patients with synchronous DPLC were operated in our department. Clinical data, such as surgical pattern, postoperative complication, and survival status, of all these patients were reviewed retrospectively. RESULTS: The 31 patients with synchronous DPLC accounted for 0.67% of all 4 649 patients operated for primary lung cancer in our department during the same period. Both tumors of synchronous DPLC were resected with lobectomy or pneumonectomy in 12 patients, while among the other 19 patients, at least 1 tumor was treated with partial pulmonary resection. The postoperative morbidity was 29% (9/31), including 1 case of respiratory insufficiency, 3 cases of atelectasis, 2 cases of atrial fibrillation, 1 case of haemoptysis, 1 case of pleural effusion, and 1 case of wound fat necrosis. No death occurred during operation or within 30 days postoperatively. The postoperative 1-, 3-, and 5-year survival rates were 52%, 29%, and 20%, respectively. CONCLUSIONS: The incidence of synchronous DPLC is low. Aggressive and reasonable surgical approach can achieve satisfactory outcomes in patients with synchronous DPLC. The postoperative morbidity is low. Some patients might achieve long-term survival.

Adenocarcinoma↗
PubMed2004

Principles of mimicking and engineering the self-organized structure of hard tissues.

The mechanism of the formation of a self-aligned hydroxyapatite (HAP) nanocrystallite structure was examined. It is found that the highly ordered HAP nanocrystallite assembly is attributed to the so-called self-(homo)epitaxial nucleation and growth. On the other hand, according to this mechanism, a high supersaturation will give rise to a random assembly of HAP crystallites. The effects of ions, biosubstrate, and supersaturation on the micro/nanostructure correlation between substrate and biominerals as well as their implications in hard tissue formation were examined. Surprisingly, some biomolecules are found to be able to suppress the supersaturation-driven interfacial structure mismatch and hence promote the well aligned HAP pattern formation.

Calcification, Physiologic↗
PubMed1998

Framework Bonding and Coordination Sphere Rearrangement in the M(2)X(2) Cores of Synthetic Analogues of Oxyhemocyanin and Related Cu and Pt Complexes.

The electronic structures of oxo- and peroxo-bridged binuclear copper compounds analogous to the active site of oxyhemocyanin are analyzed in terms of their framework electron counts with the help of density functional and extended Hückel calculations. Through-ring bonding in the Cu(2)O(2) framework is discussed by means of a topological analysis of the electron density for the model compounds [(NH(3))(3)Cu(&mgr;-eta(2):eta(2)-O(2))Cu(NH(3))(3)](2+), [(NH(3))(3)Cu(&mgr;-O)(2)Cu(NH(3))(3)](2+), and [(PH(3))(2)Cu(&mgr;-H)(2)Cu(PH(3))(2)]. The existence of isomeric peroxo- and bis(oxo)-bridged Cu complexes can be rationalized in light of the framework electron counting rules by taking into account that two electrons can be localized in the metal 3d orbitals in the former but delocalized through framework bonding molecular orbitals in the latter. An analysis of the theoretical and experimental structural data indicates that a reorganization of the Cu coordination sphere that can be affected by the nature of the terminal ligands is important for the relative stability of the two isomeric forms. In particular, the peroxo-bridged structure is favored by tridentate ligands, whereas the oxo-bridged isomer is favored by bidentate ones. The stability of the two isomers is also compared for analogous complexes with different metal or bridging atoms for which only one isomeric form is known.

Journal Article↗
PubMed1997

M(2)L(6) Complexes with Triple Mo-Mo and W-W Bonds: Molecular Topology and Inverted Pyramidality Effect.

A molecular orbital study of the model compounds [Mo(2)(NH(2))(6)], [Mo(2)(OH)(6)], [W(2)H(6)] and [W(2)Cl(6)], indicates that the M-M bond strength should increase with increasing pyramidality (i.e., the average of the M-M-L bond angles) up to a certain angle (the turnover point), after which the trend is inverted. The topology of the metal-centered pi-type orbitals of the ML(3) fragments favors the appearance of the turnover point at a smaller angle than the minimum in energy, resulting in an inverted pyramidality effect for the experimentally attainable angles. A structural database search supports the theoretical findings: the M-M distances in triple-bonded complexes of d(3) transition metal ions in the families [Mo(2)(NR(2))(6)], [W(2)(NR(2))(6)], and [W(2)(OR)(6)] decrease with increasing pyramidality angles, while the [Mo(2)(OR)(6)] complexes present a parabolic bond distance-bond angle dependence.

Journal Article↗