Preparation of flexible and transparent polylactic acids films by crystallization manipulation

Highly flexible and transparent polylactic acids (PLAs) films were successfully prepared by manipulating their crystallization. The semicrystalline poly(L ‐lactic acid) (L) was blended with a noncrystalline poly(DL ‐lactic acid) (DL) together with diglycerol tetraacetate (DGTA). Optimal DGTA content to plasticize PLAs was about 17%. Addition of DL hindered the crystallization of the films. Tensile strengths of the films having DL content more than 5% were about 10 MPa while the elongations at break were boosted as DL content increased. Films having L/DL ratio of 50/50 showed elongations at break of 270%. Stretch ability and clarity of films containing 15–50% DL were fair although they were subjected to annealing at 60 °C for 1 h. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6489–6495, 2008     

Fungicidal Activity of Recombinant Javanicin against Cryptococcus neoformans Is Associated with Intracellular Target(s) Involved in Carbohydrate and Energy Metabolic Processes

The occurrence of Cryptococcus neoformans, the human fungal pathogen that primarily infects immunocompromised individuals, has been progressing at an alarming rate. The increased incidence of infection of C. neoformans with antifungal drugs resistance has become a global concern. Potential antifungal agents with extremely low toxicity are urgently needed. Herein, the biological activities of recombinant javanicin (r-javanicin) against C. neoformans were evaluated. A time-killing assay was performed and both concentration- and time-dependent antifungal activity of r-javanicin were indicated. The inhibitory effect of the peptide was initially observed at 4 h post-treatment and ultimately eradicated within 36 to 48 h. Fungal outer surface alteration was characterized by the scanning electron microscope (SEM) whereas a negligible change with slight shrinkage of external morphology was observed in r-javanicin treated cells. Confocal laser scanning microscopic analysis implied that the target(s) of r-javanicin is conceivably resided in the cell thereby allowing the peptide to penetrate across the membrane and accumulate throughout the fungal body. Finally, cryptococcal cells coped with r-javanicin were preliminarily investigated using label-free mass spectrometry-based proteomics. Combined with microscopic and proteomics analysis, it was clearly elucidated the peptide localized in the intracellular compartment where carbohydrate metabolism and energy production associated with glycolysis pathway and mitochondrial respiration, respectively, were principally interfered. Overall, r-javanicin would be an alternative candidate for further development of antifungal agents.     

Process of destruction of large unilamellar vesicles by a zwitterionic detergent, CHAPS: partition behavior between membrane and water phases

The process of vesicle destruction by zwitterionic detergent, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), was examined to clarify the vesicle-micelle transition mechanism. The physicochemical properties including turbidity, apparent particle size, Cl(-) permeability, electron spin resonance (ESR) spectroscopic parameters, and freeze-fracture electron microscopy were investigated. The concentration of CHAPS was analyzed using HPLC to determine the partition coefficient during the solubilization process. The data obtained revealed that maximum turbidity and apparent particle size were found at the effective ratio (R(e)) of 0.21 and 0.49, respectively. With a further increase in CHAPS concentration, turbidity and particle size abruptly decreased, suggesting the formation of mixed micelles. The partition coefficient changed throughout the solubilization process. In the presence of low concentrations of CHAPS, CHAPS partitioned into vesicles without destruction of membrane bilayers. When the R(e)<0.04, the partition coefficient was independent of the detergent concentration with value of 24 M(-1). At R(e) greater than 0.05, the membrane barrier abruptly decreased. At 0.04相似文献   

A Comparison of the Nutritional and Biochemical Quality of Date Palm Fruits Obtained Using Different Planting Techniques

Date palm fruit (Phoenix dactylifera L.) is commonly consumed around the world and has recently become an economical crop in Eastern Thailand, especially the Barhi cultivar that can be consumed as fresh fruit. To maintain genetic qualities, date palm is populated through cell culture. This leads to high production costs, while access to this technique is limited. Increasing date palm population by simple seed planting is currently of interest as an alternative for local farmers. Nevertheless, information on nutritive values, bioactive compounds, and health-promoting bioactivities of seed originating from date palm fruit is unavailable. Effects of different planting origins (cell culture origin (CO) and seed origin (SO)) of date palm fruits at the Khalal stage of Barhi cultivar were investigated for nutritive values, bioactive compounds, and in vitro health-promoting properties via key enzyme inhibitions against obesity (lipase), diabetes (α-amylase, α-glucosidase, and dipeptidyl peptidase-IV), Alzheimer’s disease (cholinesterases and β-secretase), and hypertension (angiotensin-converting enzyme). Waste seeds as a by-product from date palm production were also examined regarding these properties to increase seed marketing opportunities for future food applications and other health-related products. CO and SO exhibited insignificant differences in energy, fat, and carbohydrate contents. SO had higher protein, dietary fiber, vitamin A, vitamin E, and calcium contents than CO, while CO contained higher contents of fructose, glucose and maltose. Higher phenolic contents in SO led to greater enzyme inhibitory activities than CO. Interestingly, seeds of date palm fruits mostly contained higher nutritive values than the flesh. No carotenoids were detected in seeds but higher phenolic contents resulted in greater enzyme inhibitory activities than recorded for fruit flesh. Results suggest that appropriate planting of date palm can support the development of novel date palm fruit products, leading to expansion of economic opportunities and investment in date palm fruit agriculture.     

Preparation of thermally sensitive poly[N-isopropylacrylamide-co-(maleic acid)] hydrogel membrane by electrospinning using a green solvent

Poly[N-isopropylacrylamide-co-(maleic acid)], poly(NIPA-co-MA), was synthesized by radical polymerization in an aqueous solution composing of 35% mol N-isopropylacrylamide/maleic acid. Poly(NIPA-co-MA) hydrogel nanofibrous membrane was fabricated by electrospinning using ethanol as solvent. The electrospun nanofibers were cross-linked using diethylene glycol as cross-linker, followed by a heat-induced esterification reaction at 145°C. The average diameter of electrospun fibers was 117 ± 33 nm. The hydrogel membrane exhibited a temperature sensitive property. Its minimum and maximum water absorption ratios were 4 ± 0 g g^?1 at 50°C and 17 ± 4 g g^?1 at 34°C, respectively. An equilibrium swelling state of the electrospun membrane was reached within 5 min.     

Investigation on thermoresponsive behavior of biodegradable poly(γ‐glutamic acid)‐graft‐L‐phenylalanine ethyl ester

The thermosensitivity of biodegradable and non‐toxic amphiphilic polymer derived from a naturally occurring polypeptide and a derivative of amino acid was first reported. The amphiphilic polymer consisted of poly(γ‐glutamic acid) (γ‐PGA) as a hydrophilic backbone, and L ‐phenylalanine ethyl ester (L ‐PAE) as a hydrophobic branch. Poly(γ‐glutamic acid)‐graft‐L ‐phenylalanine (γ‐PGA‐graft‐L ‐PAE) with grafting degrees of 7–49% were prepared by varying the content of a water‐soluble carbodiimide (WSC). γ‐PGA‐graft‐L ‐PAE with a grafting degree of 49% exhibited thermoresponsive phase transition behavior in an aqueous solution at around 80°C. The copolymers with grafting degrees in the range of 30–49% showed thermoresponsive properties in NaCl solution. A clouding temperature (T_cloud) could be adjusted by changing the polymer concentration and/or NaCl concentration. The thermoresponsive behavior was reversible. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Chemical-Genetic Interactions of Bacopa monnieri Constituents in Cells Deficient for the DNA Repair Endonuclease RAD1 Appear Linked to Vacuolar Disruption

Colorectal cancer is a common cancer worldwide and reduced expression of the DNA repair endonuclease XPF (xeroderma pigmentosum complementation group F) is associated with colorectal cancer. Bacopa monnieri extracts were previously found to exhibit chemical-genetic synthetic lethal effects in a Saccharomyces cerevisiae model of colorectal cancer lacking Rad1p, a structural and functional homologue of human XPF. However, the mechanisms for B. monnieri extracts to limit proliferation and promote an apoptosis-like event in RAD1 deleted yeast was not elucidated. Our current analysis has revealed that B. monnieri extracts have the capacity to promote mutations in rad1∆ cells. In addition, the effects of B. monnieri extracts on rad1∆ yeast is linked to disruption of the vacuole, similar to the mammalian lysosome. The absence of RAD1 in yeast sensitizes cells to the effects of vacuole disruption and the release of proteases. The combined effect of increased DNA mutations and release of vacuolar contents appears to induce an apoptosis-like event that is dependent on the meta-caspase Yca1p. The toxicity of B. monnieri extracts is linked to sterol content, suggesting saponins may be involved in limiting the proliferation of yeast cells. Analysis of major constituents from B. monnieri identified a chemical-genetic interaction between bacopasaponin C and rad1∆ yeast. Bacopasaponin C may have potential as a drug candidate or serve as a model for the development of analogs for the treatment of colorectal cancer.     

Solubilization of egg phosphatidylcholine liposomes by sodium taurocholate: partition behavior and morphology

Solubilization process of egg yolk phosphatidylcholine (EggPC) liposomes by sodium taurocholate (TC) was performed using membrane dialysis technique. Turbidity, apparent particle size, Cl⁻ permeability, membrane fluidity measured by electron spin resonance spectroscopy (ESR), and structural changes observed by freeze-fracture electron microscopy were investigated. The concentrations of TC were analyzed by high-performance liquid chromatography to determine the incorporation of TC in membrane phase and apparent partition coefficient. When TC concentration in water phase (D _w) was lower than 1.41 mM, or effective ratio of TC to EggPC (R _e) was less then 0.14, the partition coefficient was independent of the TC concentration and was 90 M⁻¹, where the membrane permeability of Cl⁻ was rather small. Upon increasing the concentrations in the range of 1.41 mM≤D _w<3.10 mM (0.14≤R _e<0.21), the apparent partition coefficient decreased and membrane permeability markedly increased. The coexistence of small vesicles and bilayer fragments were observed in this region. At 3.10 mM≤D _w<3.53 mM (0.21≤R _e<0.59), the steep decrease in turbidity was accompanied with the gradual increase in apparent partition coefficient, suggesting the formation of mixed micelles. The freeze-fracture electron micrographs confirmed the transformation of saturated bilayers to wormlike mixed micelles. When a further increase in TC (D _w≥3.53 or R _e≥0.59) was applied, the turbidity and apparent particle sizes became small. Transformation of the wormlike structure to ellipsoid mixed micelles was observed. The ESR spectra showed that TC/EggPC mixed micelles still retain a somewhat orderly structure.