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Same Molecular Weight (same + molecular_weight)
Selected AbstractsChitosan scaffolds for in vitro buffalo embryonic stem-like cell culture: An approach to tissue engineeringJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007Wah W. Thein-Han Abstract Three-dimensional (3D) porous chitosan scaffolds are attractive candidates for tissue engineering applications. Chitosan scaffolds of 70, 88, and 95% degree of deacetylation (% DD) with the same molecular weight were developed and their properties with buffalo embryonic stem-like (ES-like) cells were investigated in vitro. Scaffolds were fabricated by freezing and lyophilization. They showed open pore structure with interconnecting pores under scanning electron microscopy (SEM). Higher % DD chitosan scaffolds had greater mechanical strength, slower degradation rate, lower water uptake ability, but similar water retention ability, when compared to lower % DD chitosan. As a strategy to tissue engineering, buffalo ES-like cells were cultured on scaffolds for 28 days. It appeared that chitosan was cytocompatible and cells proliferated well on 88 and 95% DD scaffolds. In addition, the buffalo ES-like cells maintained their pluripotency during the culture period. Furthermore, the SEM and histological study showed that the polygonal buffalo ES-like cells proliferated well and attached to the pores. This study proved that 3D biodegradable highly deacetylated chitosan scaffolds are promising candidates for ES-like cell based tissue engineering and this chitosan scaffold and ES cell based system can be used as in vitro model for subsequent clinical applications. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source] Bimolecular radical termination: New perspectives and insightsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2008Geoffrey Johnston-Hall Abstract The reversible addition-fragmentation chain transfer-chain length dependent termination (RAFT-CLD-T) method has allowed us to answer a number of fundamental questions regarding the mechanism of diffusion-controlled bimolecular termination in free-radical polymerization (FRP). We carried out RAFT-mediated polymerizations of methyl acrylate (MA) in the presence of a star matrix to develop an understanding of the effect of polymer matrix architecture on the termination of linear polyMA radicals and compared this to polystyrene, polymethyl methacrylate, and polyvinyl acetate systems. It was found that the matrix architecture had little or no influence on termination in the dilute regime. However, due to the smaller hydrodynamic volumes of the stars in solution compared to linear polymer of the same molecular weight, the gel onset point occurred at greater conversions, and supported the postulate that chain overlap (or c*) is the main cause for the observed autoacceleration observed in FRP. Other theories based on "short,long" termination or free-volume should be disregarded. Additionally, since our systems are well below the entanglement molecular weight, entanglements should also be disregarded as the cause of the gel onset. The semidilute regime occurs over a small conversion range and is difficult to quantify. However, we obtain accurate dependencies for termination in the concentrated regime, and observed that the star polymers (through the tethering of the arms) provided constriction points in the matrix that significantly slow the diffusion of linear polymeric radicals. Although, this could at first sight be postulated to be due to reptation, the dependencies showed that reptation could be considered only at very high conversions (close to the glass transition regime). In general, we find from our data that the polymer matrix is much more mobile than what is expected if reptation were to dominate. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3155,3173, 2008 [source] Proteomics viewed on stress response of thermophilic bacterium Bacillus stearothermophilus,TLS33PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 14 2005Supachai Topanurak Abstract Thermophilic bacterium Bacillus stearothermophilus,TLS33, isolated from a hot spring in Chiang Mai, Thailand, usually produces many enzymes that are very useful for industrial applications. However, the functional properties and mechanisms of this bacterium under stress conditions are rarely reported and still need more understanding on how the bacterium can survive in stress environments. In this study, we examined the oxidative stress induced proteins of this bacterium by proteomic approach combining two-dimensional electrophoresis and mass spectrometry. When the bacterium encountered oxidative stress, peroxiredoxin, as an antioxidant enzyme, is one of the interesting stressed proteins which appeared to be systematically increased with different pI. There are four isoforms of peroxiredoxin, denoted as Prx,I, Prx,II, Prx,III and Prx,IV, which are observed at the same molecular weight of 27,kDa but differ in pI values of 5.0, 4.87, 4.81 and 4.79, respectively. The H2O2 concentration directly increased Prx,II, Prx,III and Prx,IV intensities, but decreased Prx,I intensity. These shifting of peroxiredoxin isoforms may occur by a post-translational modification. Otherwise, the longer time of oxidative stress had not affected the expression level of peroxiredoxin isoforms. Therefore, this finding of peroxiredoxin intends to know the bacterial adaptation under oxidative stress. Otherwise, this protein plays an important role in many physiological processes and able to use in the industrial applications. [source] Enzymatic stability of 2,-ethylcarbonate-linked paclitaxel in serum and conversion to paclitaxel by rabbit liver carboxylesterase for use in prodrug/enzyme therapyBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 5 2008Tadatoshi Tanino Abstract In prodrug/enzyme therapy for cancer, information on the sensitivity of hydrolytic enzymes to prodrug is required to reduce adverse effects of the parental drug and to find the activating enzyme. The aim of this study was to characterize the enzymatic stability of 2,-ethylcarbonate-linked paclitaxel (TAX-2,-Et) in the sera of several different species including humans. TAX-2,-Et disposition in serum was kinetically analysed using models with hydrolytic and/or degradation processes. To further evaluate the capability of liver carboxylesterases (CESs) in TAX-2,-Et hydrolysis, a CES isolated from rabbit liver (Ra-CES) was utilized as a model enzyme. Rat serum provided rapid enzymatic hydrolysis of TAX-2,-Et with a half-life of 4 min. The degradation of paclitaxel (TAX) (degradation rate constant, 0.16,h,1) was accompanied by the formation of an unknown compound. The conversion to TAX was almost completely inhibited by phenylmethyl sulfonylfluoride (PMSF) and bis(p-nitrophenyl) phosphate (BNPP). In human and rabbit sera, the degradation rate constant of TAX-2,-Et was 5.1,×,10,2 and 0.15,h,1, respectively, when excepting hydrolysis. The degradation products had the same molecular weight as TAX-2,-Et. The amount of TAX produced accounted for only 8,11% of the decrease in TAX-2,-Et after a 9 h exposure to rabbit or human serum. PMSF, but not BNPP, inhibited more than 90% of the TAX production in a 1.5,h incubation with human or rabbit serum. Ra-CES enzyme converted TAX-2,-Et to TAX with Vmax and Km of 74.7±13.8 nmol/min/mg protein and 8.8±2.8 µM, respectively. These results indicate that TAX-2,-Et is sensitive to serum CESs, but not cholinesterases. However, serum CESs show species-dependent hydrolysis of TAX-2,-Et. Although human serum allows the slow release of TAX, TAX-2,-Et is expected to reduce the side-effects of TAX. The Ra-CES enzyme is capable of hydrolysing TAX-2,-Et, which may be beneficial for the development of a TAX-2,-Et/enzyme therapy strategy for ovarian cancer. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||