The effect of pH on the propagation of the diploid cell WI-38 in galactose medium

The pH range for optimal growth of WI-38 in Eagle's minimum essential medium varies with the carbohydrate utilized. Growth with glucose occurred only in the pH range 6.8–7.4. Glucose-free galactose supported growth only if the pH of the medium was adjusted to 6.4–6.8. Supplementing the galactose medium with pyruvate extended the pH range for growth to 7.4. The addition of 0.01% glucose to the galactose medium increased growth at pH 7.0–7.4, reduced growth at pH 6.8, and completely inhibited growth at pH 6.6. This toxic effect of glucose under conditions impairing glycolysis was considered to be a contributing factor to the post-confluent growth rate decline associated with “contact inhibition.”     

Thermochemical pretreatment of lignocellulose to enhance methane fermentation: II. Evaluation and application of pretreatment model

A model was developed and evaluated as a tool for predicting the formation of soluble products from staged thermochemical treatment of lignocellulosic materials under acidic conditions typical of autohydrolysis. The model was used to predict the general trend of hemi-cellulose and cellulose hydrolysis between pH 2 and 4 and temperatures of 170-230 degrees C, and results were compared with experimental data. When the model was evaluated for this range of temperatures and pH values, results indicated: (1) a relatively low temperature (175 degrees C) during the first stage allows hydrolysis of the hemi-cellulose polysaccharides without significant mono-saccharide decomposition, (2) subsequent stages at higher temperatures (equal or greater than 200 degrees C) are needed for significant cellulose hydrolysis, but glucose decomposition will also occur, and, (3) a pH in the range of 2-2.5 will enhance polysaccharide hydrolysis while limiting monosaccharide decomposition. The model's predictions, indicating that the formation of biodegradable products could be optimized using Pretreatments at pH 2-2.5 for the pH range evaluated, were confirmed in experiments with white fir as a representative lig nocellulose.     

Tyrosine phosphorylation of myosin heavy chain during skeletal muscle differentiation: an integrated bioinformatics approach

Background  

Previously it has been shown that insulin-mediated tyrosine phosphorylation of myosin heavy chain is concomitant with enhanced association of C-terminal SRC kinase during skeletal muscle differentiation. We sought to identify putative site(s) for this phosphorylation event.     

X-ray absorption spectroscopy of dimethylsulfoxide reductase from Rhodobacter capsulatus

Mo K-edge X-ray absorption spectroscopy (XAS) has been used to probe the environment of Mo in dimethylsulfoxide (DMSO) reductase from Rhodobacter capsulatus in concert with protein crystallographic studies. The oxidised (Mo^VI) protein has been investigated in solution at 77?K; the Mo K-edge position (20006.4?eV) is consistent with the presence of Mo^VI and, in agreement with the protein crystallographic results, the extended X-ray absorption fine structure (EXAFS) is also consistent with a seven-coordinate site. The site is composed of one oxo-group (Mo=O 1.71?Å), four S atoms (considered to arise from the dithiolene groups of the two molybdopterins, two at 2.32?Å and two at 2.47?Å, and two O atoms, one at 1.92?Å (considered to be H-bonded to Trp 116) and one at 2.27?Å (considered to arise from Ser 147). The Mo K-edge XAS recorded for single crystals of oxidised (Mo^VI) DMSO reductase at 77?K showed a close correspondence to the data for the frozen solution but had an inferior signal:noise ratio. The dithionite-reduced form of the enzyme and a unique form of the enzyme produced by the addition of dimethylsulfide (DMS) to the oxidised (Mo^VI) enzyme have essentially identical energies for the Mo K-edge, at 20004.4?eV and 20004.5?eV, respectively; these values, together with the lack of a significant presence of Mo^V in the samples as monitored by EPR spectroscopy, are taken to indicate the presence of Mo^IV. For the dithionite-reduced sample, the Mo K-edge EXAFS indicates a coordination environment for Mo of two O atoms, one at 2.05?Å and one at 2.51?Å, and four S atoms at 2.36?Å. The coordination environment of the Mo in the DMS-reduced form of the enzyme involves three O atoms, one at 1.69?Å, one at 1.91?Å and one at 2.11?Å, plus four S atoms, two at 2.28?Å and two at 2.37?Å. The EXAFS and the protein crystallographic results for the DMS-reduced form of the enzyme are consistent with the formation of the substrate, DMSO, bound to Mo^IV with an Mo-O bond of length 1.92?Å.     

Influence of nanofibers on growth and gene expression of human tendon derived fibroblast

Background  

Rotator cuff tears are a common and frequent lesion especially in older patients. The mechanisms of tendon repair are not fully understood. Common therapy options for tendon repair include mini-open or arthroscopic surgery. The use of growth factors in experimental studies is mentioned in the literature. Nanofiber scaffolds, which provide several criteria for the healing process, might be a suitable therapy option for operative treatment. The aim of this study was to explore the effects of nanofiber scaffolds on human tendon derived fibroblasts (TDF's), as well as the gene expression and matrix deposition of these fibroblasts.     

Channeling between the active sites of formiminotransferase-cyclodeaminase. Binding and kinetic studies

Formiminotransferase-cyclodeaminase, a circular tetramer of dimers, binds four tetrahydropteroylpolyglutamates/octamer, which indicates that these polyglutamate sites are formed by one type of subunit interface. The transferase and deaminase are separate catalytic sites as determined by inhibition studies with (6R)-tetrahydropteroylglutamate and by the observation that the activities can operate simultaneously. Under conditions where the transferase is saturated with tetrahydropteroyl(glutamate)n substrate, exogenously added formimino intermediate is utilized by the deaminase only if at least one of the substrate/intermediate pair is a monoglutamate. These properties indicate the existence of only one polyglutamate site/pair of catalytic sites. Kinetic specificity for each activity as measured by Vm/Km increases for longer polyglutamates, but does not differentiate among 4, 5, 6, and 7 glutamates. The enzyme shows distinct preference for hexaglutamate based on Kd as well as on Km values. With all substrates, Vm of the deaminase is greater than that of the transferase, allowing for potential channeling of the intermediate between active sites. Efficiency of channeling, optimal with pentaglutamate, does not correspond with affinity for binding. This demonstrates that a steric requirement predominates over simple sequestering of intermediates on the enzyme surface as the fundamental mechanism for channeling.     

DAF-18/PTEN inhibits germline zygotic gene activation during primordial germ cell quiescence

Quiescence, an actively-maintained reversible state of cell cycle arrest, is not well understood. PTEN is one of the most frequently lost tumor suppressors in human cancers and regulates quiescence of stem cells and cancer cells. The sole PTEN ortholog in Caenorhabditis elegans is daf-18. In a C. elegans loss-of-function mutant for daf-18, primordial germ cells (PGCs) divide inappropriately in L1 larvae hatched into starvation conditions, in a TOR-dependent manner. Here, we further investigated the role of daf-18 in maintaining PGC quiescence in L1 starvation. We found that maternal or zygotic daf-18 is sufficient to maintain cell cycle quiescence, that daf-18 acts in the germ line and soma, and that daf-18 affects timing of PGC divisions in fed animals. Importantly, our results also implicate daf-18 in repression of germline zygotic gene activation, though not in germline fate specification. However, TOR is less important to germline zygotic gene expression, suggesting that in the absence of food, daf-18/PTEN prevents inappropriate germline zygotic gene activation and cell division by distinct mechanisms.