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Dimethylsulfoniopropionate (DMSP) plays important roles in oceanic carbon and sulfur cycling and may significantly impact climate. It is a biomolecule synthesized from the methionine (Met) pathway and proposed to serve various physiological functions to aid in environmental stress adaptation through its compatible solute, cryoprotectant, and antioxidant properties. Yet, the enzymes and mechanisms regulating DMSP production are poorly understood. This study utilized a proteomics approach to investigate protein changes associated with salinity-induced DMSP increases in the model sea-ice diatom Fragilariopsis cylindrus (CCMP 1102). We hypothesized proteins associated with the Met-DMSP biosynthesis pathway would increase in relative abundance when challenged with elevated salinity. To test this hypothesis axenic log-phase cultures initially grown at a salinity of 35 were gradually shifted to a final salinity of 70 over a 24-h period. Intracellular DMSP was measured and two-dimensional gel electrophoresis was used to identify protein changes at 48 h after the shift. Intracellular DMSP increased by approximately 85% in the hypersaline cultures. One-third of the proteins increased under high salinity were associated with amino acid pathways. Three protein isoforms of S-adenosylhomo-cysteine hydrolase, which synthesizes a Met precursor, increased 1.8-to 2.1-fold, two isoforms of S-adenosyl Met synthetase increased 1.9-to 2.5-fold, and S-adenosyl Met methyltransferase increased by 2.8-fold, suggesting active methyl cycle proteins are recruited in the synthesis of DMSP. Proteins from the four enzyme classes of the proposed algal Met transaminase DMSP pathway were among the elevated proteins, supporting our hypothesis and providing candidate genes for future characterization studies.

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Collagenous microbeads are a favorable scaffold for adipose-derived stem cells, allowing ex vivo proliferation and differentiation on particles that are small enough to be injected.

Small intestinal submucosa particles are a favorable scaffold for preadipocytes, allowing ex vivo proliferation on particles small enough to be injected. Delivery of FGF-2 from poly(lactic-co-glycolic acid) microspheres resulted in cell survival and enhanced vascularization.

Melatonin induces cellular differentiation in numerous cell types. Data show that multiple mechanisms are involved in these processes that are cell-type specific and may be receptor dependent or independent. The focus of this study was to specifically assess the role of human MT1 melatonin receptors in cellular differentiation using an MT1-Chinese hamster ovary (CHO) model; one that reproducibly produces measurable morphologic changes in response to melatonin. Using multiple approaches, we show that melatonin induces MT1-CHO cells to hyperelongate through a MEK 1/2, and ERK 1/2-dependent mechanism that is dependent upon MT1 receptor internalization, Gi protein activation, and clathrin-mediated endocytosis. Using immunoprecipitation analysis, we show that MT1 receptors form complexes with Gi(alpha) 2,3, Gq(alpha), beta-arrestin-2, MEK 1/2, and ERK 1/2 in the presence of melatonin. We also show that MEK and ERK activity that is induced by melatonin is dependent on Gi protein activation, clathrin-mediated endocytosis and is modulated by microtubules. We conclude from these studies that melatonin-induced internalization of human MT1 melatonin receptors in CHO cells is responsible for activating both MEK 1/2 and ERK 1/2 to drive these morphologic changes. These events, as mediated by melatonin, require Gi protein activation and endocytosis mediated through clathrin, to form MT1 receptor complexes with beta-arrestin-2/MEK 1/2 and ERK 1/2. The MT1-CHO model is invaluable to mapping out signaling cascades as mediated through MT1 receptors especially because it separates out MEK/ERK 1/2 activation by MT1 receptors from that of receptor tyrosine kinases.

Using density functional theory and a combination of growing string and dimer method transition state searches, we investigate the interaction of phosphorus atoms with the silicon (001) surface.We report reaction pathways for three technologically important processes: diffusion of phosphorus adatoms on the surface, incorporation of the phosphorus adatom into the surface, and diffusion of the incorporated phosphorus atom within the surface. These reactions have direct relevance to nanoscale lithographic schemes capable of positioning single phosphorus atoms on the silicon surface. Temperatures of activation for the various processes are calculated and, where possible, compared with experiment.

The action of water on y-Ca,SiO,, either alone or in the presence of calcium hydroxide, quartz, or amorphous silica, has been studied mainly a t 150-600" and 5-350 bars. A new compound, of probable composition Ca8Si5Ols, is formed over a wide range of conditions; its appears to have a regularly interstratified structure composed of alternate layers of y-Ca,SiO, and kilchoanite (Ca,Si,O,).The supposed compound, " y-dicalcium silicate hydrate " or " dicalcium silicate hydrate (C)," which has been widely reported as forming under saturated steam pressures around ZOO", is a mixture consisting principally of a disordered form of Ca8Si5018 and calciochondrodite, Ca5(Si04),(OH),.Reaction sequences and equilibria are discussed ; a t least up to 450", the initial and early products are crystalline compounds (kilchoanite, calcio-chondrodite, Ca8Si5OI8) with structures related to that of y-Ca,SiO,.THE system CaO-SO,-H,O has been extensively studied under hydrothermal conditions because of its relevance to the manufacture of autoclaved building materials and to geological problems. Few studies have, however, been made much above 200" on the reaction of water with y-Ca,SiO,, either alone or in the presence of added lime or silica, and the present work was therefore undertaken. I t had two specific aims. First, a supposed compound of composition 2CaO,Si0,,0~3--1~OH2O, generally called y-dicalcium silicate hydrate or dicalcium silicate hydrate (C): has been reported by many workers to form under saturated steam pressures around 200". The status of this product as a distinct compound has been questioned,* and it was hoped to obtain more definite evidence as to its nature. Secondly, there is uncertainty about the stability under hydrothermal conditions at 200-600" of kilchoanite (a polymorph of Ca,Si,O, relative to assemblages such as foshagite [Ca,Si309(0H),] plus dellaite (Ca,Si,O,,H,), and it was hoped to obtain further evidence bearing on this problem.