Biomedical subjects

Yanting Wang

Publications and source records attributed to Yanting Wang.

8 recordsLinked to original sources

PubMed2006

Tail aggregation and domain diffusion in ionic liquids.

An extended multiscale coarse-graining model for ionic liquids is used to investigate the liquid crystal-like phase in certain ionic liquids. The tail groups of the cations with a sufficient side-chain length are found to aggregate, forming spatially heterogeneous domains, due to the competition between the electrostatic interactions between the charged head groups and the anions and the collective short-range interactions between the neutral tail groups. With a sufficiently long alkyl chain at a low enough temperature, the tail domains remain relatively stable, despite the diffusion of individual ions in the liquid phase. With increasing temperature, the average tail domains begin to diffuse, while beyond a transition temperature, their average density has an almost uniform distribution, although the tail groups still form instantaneous domains.

Carbon↗

PubMed2006

Multiscale coarse-graining of ionic liquids.

A recently developed multiscale coarse-graining (MS-CG) approach for obtaining coarse-grained force fields from fully atomistic molecular dynamics simulation is applied to the challenging case of the EMIM+NO3- ionic liquid. The force-matching in the MS-CG methodology is accomplished with an explicit separation of bonded and nonbonded forces. While the nonbonded forces are adopted from this force-matching approach, the bonded forces are obtained from fitting the statistical configurational data from the atomistic simulations. The many-body electronic polarizability is also successfully broken into effective pair interactions. With a virial constraint fixing the system pressure, the MS-CG models rebuild satisfactory structural and thermodynamic properties for different temperatures. The MS-CG model developed from a modest atomistic simulation is therefore suitable for simulating much larger systems, because the coarse-grained models show significant time integration efficiency. This approach is expected to be general for coarse-graining other ionic liquids, as well as many other liquid-state systems. The limitations of the present coarse-graining procedure are also discussed.

Algorithms↗

PubMed2006

Ellagic and tannic acids protect newly synthesized elastic fibers from premature enzymatic degradation in dermal fibroblast cultures.

Progressive proteolytic degradation of cutaneous elastic fibers, that cannot be adequately replaced or repaired by adult dermal fibroblasts, constitutes a major feature of aging skin. Our present investigations, employing monolayer cultures of human dermal fibroblasts and organ cultures of skin biopsies, were aimed at testing whether the hydrophilic tannic acid (TA) and lipophilic ellagic acid (EA) would protect dermal elastin from exogenous and endogenous enzymatic degradation. Results from both culture systems indicated that dermal fibroblasts, maintained with TA or EA, deposit significantly more elastic fibers than untreated control cultures despite the fact that neither polyphenol enhanced transcription of elastin mRNA or cellular proliferation. Results of a pulse and chase experiment showed that pretreatment with both polyphenols enhanced biostability of tropoelastin and newly deposited elastin. Results of in vitro assays indicated that both polyphenols bound to purified elastin and significantly decreased its proteolytic degradation by elastolytic enzymes belonging to the serine proteinase, cysteine proteinase, and metallo-proteinase families. Importantly, both polyphenols also synergistically enhanced elastogenesis induced by selected elastogenic compounds in cultures of dermal fibroblasts. We propose that EA and TA may be useful for preventing proteolytic degradation of existing dermal elastic fibers and for enhancing more efficient elastogenesis in aged skin.

Adolescent↗

PubMed2005

Unique spatial heterogeneity in ionic liquids.

A multiscale coarse-graining model for ionic liquids has been extended to investigate the unique aggregation of cations in ionic liquids through computer simulation. It has been found that, with sufficiently long side chains, the tail groups of cations aggregate to form spatially heterogeneous domains, while headgroups of the cations and the anions distribute as uniformly as possible. This is understood as the result of competition between the charged electrostatic interactions between headgroups and anions and the collective short-range interactions between the neutral tail groups. This aggregation can help to explain a number of experimentally observed physical phenomena in ionic liquids.

Journal Article↗

PubMed2005

Melting of icosahedral gold nanoclusters from molecular dynamics simulations.

Molecular dynamics simulations show that gold clusters with about 600-3000 atoms crystallize into a Mackay icosahedron upon cooling from the liquid. A detailed surface analysis shows that the facets on the surface of the Mackay icosahedral gold clusters soften but do not premelt below the bulk melting temperature. This softening is found to be due to the increasing mobility of vertex and edge atoms with temperature, which leads to inter-layer and intra-layer diffusion, and a shrinkage of the average facet size, so that the average shape of the cluster is nearly spherical at melting.

Journal Article↗

PubMed2005

Proteolytic digest derived from bovine Ligamentum Nuchae stimulates deposition of new elastin-enriched matrix in cultures and transplants of human dermal fibroblasts.

BACKGROUND: Diverse topical products and injectable fillers used for correcting facial wrinkles induce rather short-lived effects because they target replacement of dermal collagen and hyaluronan, matrix components of limited biologic durability. OBJECTIVE: Present studies were aimed at stimulation of fully differentiated human dermal fibroblasts to resume deposition of new extracellular matrix rich of elastin, the most durable and metabolically inert component of dermal ECM. METHODS: We have created a novel proteolytic digest of bovine ligamentum nuchae (ProK-60), and tested its potential biological effect on dermal fibroblasts derived from females of different ages. Northern blots, quantitative immunohistochemistry and metabolic assays were used to assess effects of ProK-60 on proliferation and matrix production in primary cultures of dermal fibroblasts, in cultures of skin explants and after implantation of stimulated fibroblasts into the skin of athymic nude mice. RESULTS: ProK-60 increased proliferation (25-30%) of cultured dermal fibroblasts and significantly enhanced their production of new elastic fibers (>250%) and collagen fibers (100%). These effects were mostly mediated by stimulation of cellular elastin receptor. In contrast, ProK-60 inhibited production of fibronectin (-30%) and chondroitin sulfate proteoglycans (-50%). ProK-60 also activated proliferation of dermal fibroblasts, mostly derived from the stratum basale and induced deposition of elastic fibers in cultures of skin explants. Moreover, human fibroblasts pre-treated with ProK-60 produced abundant elastic fibers after their injection into the skin of athymic nude mice. CONCLUSION: The described biological effects of ProK-60, including its unique elastogenic property, encourage use of this compound in cosmetic formulations stimulating rejuvenation of aged skin.

Animals↗

PubMed2005

Surface-driven bulk reorganization of gold nanorods.

Molecular dynamic simulations are used to study the structural stability of gold nanorods upon heating. We show that the global stability of the rod is governed by the free energetics of its surface. In particular, an instability of surface facets nucleates a bulk instability that leads to both surface and bulk reorganization of the rod. The surface reorganizes to form new, more stable, {111} facets, while the underlying fcc lattice completely reorients to align with this new surface structure. Rods with predominantly {111} facets remain stable until melting.

Journal Article↗

PubMed2004

Retrovirally mediated overexpression of versican v3 reverses impaired elastogenesis and heightened proliferation exhibited by fibroblasts from Costello syndrome and Hurler disease patients.

The phenotypic resemblance of patients with Costello syndrome and Hurler disease has been linked to impaired formation of elastic fibers that coincides with elevated cellular proliferation. Impaired elastogenesis in these diseases associates with respective abnormal accumulation of chondroitin sulfate and dermatan sulfate proteoglycans that induce cell surface shedding of elastin-binding protein (EBP) normally required for intracellular chaperoning of tropoelastin and its assembly into elastic fibers. A variant of the chondroitin sulfate proteoglycan versican, V3, which lacks chondroitin sulfate, has recently been shown to stimulate elastic fiber assembly and decrease proliferation when expressed by retroviral transduction in arterial smooth muscle cells. However, the mechanism(s) by which V3 influences this phenotype is not known. We now demonstrate that transduction of skin fibroblasts from Costello syndrome and Hurler disease patients with cDNA to versican V3 completely reverses impaired elastogenesis and restores normal proliferation of these cells. This phenotypic reversal is accompanied by loss of chondroitin sulfate from the cell surface and increased levels of EBP. Versican V3 transduction of skin fibroblasts from GM(1)-gangliosidosis patients, which lack EBP, failed to restore impaired elastogenesis. These results suggest that induction of elastic fiber production by gene transfer of versican V3 in skin fibroblasts is mediated by rescue of the tropoelastin chaperone, EBP.

Animals↗