Novel poly(3-hydroxybutyrate) nanocomposites containing WS2 inorganic nanotubes with improved thermal, mechanical and tribological properties

Poly(3-hydroxybutyrate) (PHB) nanocomposites containing environmentally-friendly tungsten disulphide inorganic nanotubes (INTeWS2) have been successfully prepared by a simple solution blending method. The dynamic and isothermal crystallization studies by differential scanning calorimetry (DSC) demonstrated that the INTeWS2 exhibits much more prominent nucleation activity on the crystallization of PHB than specific nucleating agents or other nanoscale fillers. Both crystallization rate and crystallinity significantly increase in the nanocomposites compared to neat PHB. These changes occur without modifying the crystalline structure of PHB in the nanocomposites, as shown by wide-angle X-ray diffraction (WAXS) and infrared/Raman spectroscopy. Other parameters such as the Avrami exponent, the equilibrium melting temperature, global rate constant and the fold surface free energy of PHB chains in the nanocomposites were obtained from the calorimetric data in order to determine the influence of the INTeWS2 filler. The addition of INTeWS2 remarkably influences the energetics and kinetics of nucleation and growth of PHB, reducing the fold surface free energy by up to 20%. Furthermore, these nanocomposites also show an improvement in both tribological and mechanical (hardness and modulus) properties with respect to pure PHB evidenced by friction and nanoindentation tests, which is of important potential interest for industrial and medical applications.

d-β-Hydroxybutyrate protects neurons in models of Alzheimer's and Parkinson's disease

The heroin analogue 1-methyl-4-phenylpyridinium, MPP+, both in vitro and in vivo, produces death of dopaminergic substantia nigral cells by inhibiting the mitochondrial NADH dehydrogenase multienzyme complex, producing a syndrome indistinguishable from Parkinson's disease. Similarly, a fragment of amyloid protein, Aβ1–42, is lethal to hippocampal cells, producing recent memory deficits characteristic of Alzheimer's disease. Here we show that addition of 4 mM d-β-hydroxybutyrate protected cultured mesencephalic neurons from MPP+ toxicity and hippocampal neurons from Aβ1–42 toxicity. Our previous work in heart showed that ketone bodies, normal metabolites, can correct defects in mitochondrial energy generation. The ability of ketone bodies to protect neurons in culture suggests that defects in mitochondrial energy generation contribute to the pathophysiology of both brain diseases. These findings further suggest that ketone bodies may play a therapeutic role in these most common forms of human neurodegeneration.

Cleavage of lamin A by Mch2 alpha but not CPP32: multiple interleukin 1 beta-converting enzyme-related proteases with distinct substrate recognition properties are active in apoptosis.

Although proteases related to the interleukin 1 beta-converting enzyme (ICE) are known to be essential for apoptotic execution, the number of enzymes involved, their substrate specificities, and their specific roles in the characteristic biochemical and morphological changes of apoptosis are currently unknown. These questions were addressed using cloned recombinant ICE-related proteases (IRPs) and a cell-free model system for apoptosis (S/M extracts). First, we compared the substrate specificities of two recombinant human IRPs, CPP32 and Mch2 alpha. Both enzymes cleaved poly-(ADP-ribose) polymerase, albeit with different efficiencies. Mch2 alpha also cleaved recombinant and nuclear lamin A at a conserved VEID decreases NG sequence located in the middle of the coiled-coil rod domain, producing a fragment that was indistinguishable from the lamin A fragment observed in S/M extracts and in apoptotic cells. In contrast, CPP32 did not cleave lamin A. The cleavage of lamin A by Mch2 alpha and by S/M extracts was inhibited by millimolar concentrations of Zn2+, which had a minimal effect on cleavage of poly (ADP-ribose) polymerase by CPP32 and by S/M extracts. We also found that N-(acetyltyrosinylvalinyl-N epsilon-biotinyllysyl)aspartic acid [(2,6-dimethylbenzoyl)oxy]methyl ketone, which derivatizes the larger subunit of active ICE, can affinity label up to five active IRPs in S/M extracts. Together, these observations indicate that the processing of nuclear proteins in apoptosis involves multiple IRPs having distinct preferences for their apoptosis-associated substrates.

Gene-targeted deletion and replacement mutations of the T-cell receptor beta-chain enhancer: the role of enhancer elements in controlling V(D)J recombination accessibility.

To assess the role of transcriptional enhancers in regulating accessibility of the T-cell receptor beta-chain (TCRbeta) locus, we generated embryonic stem cell lines in which a single allelic copy of the endogenous TCRbeta enhancer (Ebeta) was either deleted or replaced with the immunoglobulin heavy-chain intronic enhancer. We assayed the effects of these mutations on activation of the TCRbeta locus in normal T- and B-lineage cells by RAG-2 (recombination-activating gene 2)-deficient blastocyst complementation. We found that Ebeta is required for rearrangement and germ-line transcription of the TCRbeta locus in T-lineage cells. In the absence of Ebeta, the heavy-chain intronic enhancer partially supported joining region beta-chain rearrangement in T- but not in B-lineage cells. However, ability of the heavy-chain intronic enhancer to induce rearrangements was blocked by linkage to an expressed neomycin-resistance gene (neo(r)). These results demonstrate a critical role for Ebeta in promoting accessibility of the TCRbeta locus and suggest that additional negative elements may cooperate to further modulate this process.

Excitotoxicity in the lung: N-methyl-D-aspartate-induced, nitric oxide-dependent, pulmonary edema is attenuated by vasoactive intestinal peptide and by inhibitors of poly(ADP-ribose) polymerase.

Excitatory amino acid toxicity, resulting from overactivation of N-methyl-D-aspartate (NMDA) glutamate receptors, is a major mechanism of neuronal cell death in acute and chronic neurological diseases. We have investigated whether excitotoxicity may occur in peripheral organs, causing tissue injury, and report that NMDA receptor activation in perfused, ventilated rat lungs triggered acute injury, marked by increased pressures needed to ventilate and perfuse the lung, and by high-permeability edema. The injury was prevented by competitive NMDA receptor antagonists or by channel-blocker MK-801, and was reduced in the presence of Mg2+. As with NMDA toxicity to central neurons, the lung injury was nitric oxide (NO) dependent: it required L-arginine, was associated with increased production of NO, and was attenuated by either of two NO synthase inhibitors. The neuropeptide vasoactive intestinal peptide and inhibitors of poly(ADP-ribose) polymerase also prevented this injury, but without inhibiting NO synthesis, both acting by inhibiting a toxic action of NO that is critical to tissue injury. The findings indicate that: (i) NMDA receptors exist in the lung (and probably elsewhere outside the central nervous system), (ii) excessive activation of these receptors may provoke acute edematous lung injury as seen in the "adult respiratory distress syndrome," and (iii) this injury can be modulated by blockade of one of three critical steps: NMDA receptor binding, inhibition of NO synthesis, or activation of poly(ADP-ribose) polymerase.

Protein crosslinking studies suggest that Rhizobium meliloti C4-dicarboxylic acid transport protein D, a sigma 54-dependent transcriptional activator, interacts with sigma 54 and the beta subunit of RNA polymerase.

Rhizobium meliloti C4-dicarboxylic acid transport protein D (DCTD) activates transcription by a form of RNA polymerase holoenzyme that has sigma 54 as its sigma factor (referred to as E sigma 54). DCTD catalyzes the ATP-dependent isomerization of closed complexes between E sigma 54 and the dctA promoter to transcriptionally productive open complexes. Transcriptional activation probably involves specific protein-protein interactions between DCTD and E sigma 54. Interactions between sigma 54-dependent activators and E sigma 54 are transient, and there has been no report of a biochemical assay for contact between E sigma 54 and any activator to date. Heterobifunctional crosslinking reagents were used to examine protein-protein interactions between the various subunits of E sigma 54 and DCTD. DCTD was crosslinked to Salmonella typhimurium sigma 54 with the crosslinking reagents succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate and N-hydroxysulfosuccinimidyl-4-azidobenzoate. Cys-307 of sigma 54 was identified by site-directed mutagenesis as the residue that was crosslinked to DCTD. DCTD was also crosslinked to the beta subunit of Escherichia coli core RNA polymerase with succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate, but not with N-hydroxysulfosuccinimidyl-4-azidobenzoate. These data suggest that interactions of DCTD with sigma 54 and the beta subunit may be important for transcriptional activation and offer evidence for interactions between a sigma 54-dependent activator and sigma 54, as well as the beta subunit of RNA polymerase.

DNA polymerase beta bypasses in vitro a single d(GpG)-cisplatin adduct placed on codon 13 of the HRAS gene.

We have examined the capacity of calf thymus DNA polymerases alpha, beta, delta, and epsilon to perform in vitro translesion synthesis on a substrate containing a single d(GpG)-cisplatin adduct placed on codon 13 of the human HRAS gene. We found that DNA synthesis catalyzed by DNA polymerases alpha, delta, and epsilon was blocked at the base preceding the lesion. Addition of proliferating cell nuclear antigen to DNA polymerase delta and replication protein A to DNA polymerase alpha did not restore their capacity to elongate past the adduct. On the other hand, DNA polymerase beta efficiently bypassed the cisplatin adduct. Furthermore, we observed that DNA polymerase beta was the only polymerase capable of primer extension of a 3'-OH located opposite the base preceding the lesion. Likewise, DNA polymerase beta was able to elongate the arrested replication products of the other three DNA polymerases, thus showing its capacity to successfully compete with polymerases alpha, delta, and epsilon in the stalled replication complex. Our data suggest (i) a possible mechanism enabling DNA polymerase beta to bypass a d(GpG)-cisplatin adduct in vitro and (ii) a role for this enzyme in processing DNA damage in vivo.

Elevated expression of H type GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase is associated with human colon adenocarcinoma progression.

GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase (EC 2.4.1.69) is a key enzyme in the biosynthesis of fucosylated type 1 and 2 lactoseries structures, such as Lewis b and the H type 2 and Lewis Y, respectively, that are accumulated in colon adenocarcinoma. Analysis of the mRNA transcript level for the human H gene-encoded beta-D-galactoside alpha-2-L-fucosyltransferase revealed 40- and 340-fold increases in the mRNA levels in all adenocarcinomas and tumor cell lines, respectively, compared to normal colon mucosa where a low level of mRNA transcript was detected. A variable increase in mRNA transcript levels was observed in 50% of adenomatous polyps. Nucleotide sequence analysis of the protein coding region of the cDNAs derived from normal colon, adenoma, and colon adenocarcinoma revealed 100% homology, suggesting that there are no tumor-associated allelic variations within the H beta-D-galactoside alpha-2-L-fucosyltransferase cDNA. These results suggest that beta-D-galactoside alpha-2-L-fucosyltransferase expression highly correlates with malignant progression of colon adenocarcinoma.

A discourse delivered at Schenectady, July 22d, A.D., 1823, before the New-York Alpha of the Phi Beta Kappa ...

Mode of access: Internet.

Recherches sur quelques derives du 2, 4-dinitro-1-naphtol et sur les derives d'azonium obtenus par condensation de l'acide [beta]-naphtoquinone-4-sulfonique avec la phenylorthophenylenediamine /

Thesis (doctoral)--Universitate de Geneve, 1897.

Polymeric grafting of acrylic acid onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Surface functionalization for tissue engineering applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt processed disks and solvent cast films were modified by graft co-polyinerization with acrylic acid (AAc) in methanol solution at ambient temperature using gamma irradiation (dose rate of 4.5 kGy/h). To assess the presence of carboxylic acid groups on the surface, reaction with pentafluorophenol was performed prior to X-ray photoelectron spectroscopy analysis. The grafting yield for all samples increased with monomer concentration (2-15%), and for the solvent cast films, it also increased with dose (2-9 kGy). However, the grafting yield of the melt processed disks was largely independent of the radiation dose (2-8 kGy). Toluidine blue was used to stain the modified materials facilitating, visual information about the extent of carboxylic acid functionalization and depth penetration of the grafted copolymer. Covalent linking of glucosamine to the functionalized surface was achieved using carbodimide chemistry verifying that the modified substrates are suitable for biomolecule attachment.

Extrusion of mixtures of starch and D-limonene encapsulated with beta-cyclodextrin: Flavour retention and physical properties

d-Limonene was encapsulated with beta-cyclodextrin to improve its retention during pre-added flavour starch extrusion. The objective of this work was to determine the effect of processing condition on the flavour retention and extrudate properties. Corn starch containing five levels of beta-cyclodextrin-d-limonene capsules (0-5%) were extruded at five different maximum barrel temperatures (133-167 degrees C) and screw speeds (158-242 rpm) using a twin screw extruder. The effect of these parameters on the flavour retention, expansion, texture, colour difference (Delta E), Water Absorption Index, Water Solubility Index, and residence time distribution (RTD) were investigated. Barrel temperature and capsule level predominantly influenced flavour retention and extrudate properties, while screw speed primarily affected extruder performances such as torque, die pressure, specific mechanical energy and RTD. (c) 2005 Elsevier Ltd. All rights reserved.

Molecular dynamics characterization of n-octyl-beta-D-glucopyranoside micelle structure in aqueous solution

n-Octyl-beta-D-glueopyranoside (OG) is a non-ionic glycolipid, which is used widely in biotechnical and biochemical applications. All-atom molecular dynamics simulations from two different initial coordinates and velocities in explicit solvent have been performed to characterize the structural behaviour of an OG aggregate at equilibrium conditions. Geometric packing properties determined from the simulations and small angle neutron scattering experiment state that OG micelles are more likely to exist in a non-spherical shape, even at the concentration range near to the critical micelle concentration (0.025 M). Despite few large deviations in the principal moment of inertia ratios, the average micelle shape calculated from both simulations is a prolate ellipsoid. The deviations at these time scales are presumably the temporary shape change of a micelle. However, the size of the micelle and the accessible surface areas were constant during the simulations with the micelle surface being rough and partially elongated. Radial distribution functions computed for the hydroxyl oxygen atoms of an OG show sharper peaks at a minimum van der Waals contact distance than the acetal oxygen, ring oxygen, and anomeric carbon atoms. This result indicates that these atoms are pointed outwards at the hydrophilic/hydrophobic interface, form hydrogen bonds with the water molecules, and thus hydrate the micelle surface effectively. (c) 2005 Elsevier Inc. All rights reserved.