Photoresponsive optically active polymers—a review

Photoresponsive macromolecules are of interest both as novel organic materials for applications in photodevices and as models for photomodulated biological processes. The presence in polymer chains of photosensitive groups and of chiral groups capable of inducing optical activity into the polymer is very useful for the analysis of photomodulated structural variations and allows storage of the light effect in the form of chiral information. Polypeptides bearing photochromic groups in the side chains are very convenient as the chiroptical properties of the peptide chromophore can be correlated to the backbone conformation. Thus polymers of L-aspartic acid, L-glutamic acid and L-lysine with azobenzene or stilbene groups attached covalently to the side chains are discussed in terms of photoinduced conformational changes and chiroptical information storage in the spectral region of the peptide and of the photoresponsive chromophore. Optically active photochromic macromolecules with hydrocarbon backbone, such as copolymers of (—)-menthyl acrylate with vinyl or acryloyl derivatives of azobenzene, stilbene and indolinospirobenzopyran, also show in some cases photodependence of chiroptical properties with evidence of at least local conformational changes as a consequence of light irradiation which can be used for chiral information.     

A generalized approach to the analysis of voltage stability in electric power systems

In this paper a new method for analysing the voltage stability problem in electric power systems is presented. The approach starts with a linearized model in state space form of a multi-machine power system, then rigorous voltage stability conditions are derived on the basis of a suitable aggregated model of the original system capable of retaining the dynamics of voltages at generator and load nodes.The approach allows a systematic individualization of all the dynamic factors which affect voltage instability phenomena and suggests the appropriate representation which has to be adopted for each dynamic component of the system.The validity and usefulness of the suggested method are illustrated by carrying out simulation studies on a sample power system.     

Electrodeposition of nanostructured bioactive hydroxyapatite-heparin composite coatings on titanium for dental implant applications

In this paper we describe the one-pot fabrication of hydroxyapatite (HA)-heparin composites by electrodeposition onto Ti substrates and their characterisation in terms of structure, morphology, heparin content and bioactivity. HA coatings are well known and widely applied osteointegration enhancers, but post-implant healing rate in dental applications is still suboptimal: e.g. coagulation control plays a key role and the incorporation of an anticoagulant is considered a highly desirable option. In this study, we have developed an improved, simple and robust growth procedure for single-phase, pure HA-heparin films of thickness 1/3 μm. HA-heparin, forming nanowires, has the ideal morphology for bone mineralisation. Staining assays revealed homogeneous incorporation of sizable amounts of heparin in the composite films. The bioactivities of the HA and HA-heparin coatings on Ti were compared by HeLa cell proliferation/viability tests and found to be enhanced by the presence of the anticoagulant.     

Synthesis, characterization and antimicrobial activity of conjugates based on fluoroquinolon-type antibiotics and gelatin

Different fluoroquinolon-type antibiotics were conjugated to gelatin with the aim to synthesize biomacromolecules with antimicrobial properties. The covalent linkage of the antibiotic was performed by a radical process involving the residues in the side chains of gelatin able to undergo oxidative modifications. The conjugation of antibiotic moieties onto the protein structure was confirmed by FT-IR, UV–Vis, fluorescence, and calorimetric analyses. Biocompatibility tests were performed on human bone marrow mesenchymal stromal cells and the antibacterial properties of bioactive polymers were investigated by appropriate tests against Klebsiella pneumoniae and Escherichia coli. With regard to the tests conducted in the presence of E. coli, a minimum inhibitory concentration (MIC) ranging from 0.05 to 0.40 μg mL^?1 was recorded, while in the presence of K. pneumoniae this concentration varies from 0.10 to 1.60 μg mL^?1. In all the conjugates, the drug moieties retain their biological activity and the MIC values are lower than the resistance parameters of fluoroquinolon-type antibiotics versus Enterobacteriacae. The collected data suggest a broad range of applications, from biomedical to pharmaceutical and food science for all conjugates.     

NK Cells in Chronic Lymphocytic Leukemia and Their Therapeutic Implications

Key features of chronic lymphocytic leukemia (CLL) are defects in the immune system and the ability of leukemic cells to evade immune defenses and induce immunosuppression, resulting in increased susceptibility to infections and disease progression. Several immune effectors are impaired in CLL, including T and natural killer (NK) cells. The role of T cells in defense against CLL and in CLL progression and immunotherapy has been extensively studied. Less is known about the role of NK cells in this leukemia, and data on NK cell alterations in CLL are contrasting. Besides studies showing that NK cells have intrinsic defects in CLL, there is a large body of evidence indicating that NK cell dysfunctions in CLL mainly depend on the escape mechanisms employed by leukemic cells. In keeping, it has been shown that NK cell functions, including antibody-dependent cellular cytotoxicity (ADCC), can be retained and/or restored after adequate stimulation. Therefore, due to their preserved ADCC function and the reversibility of CLL-related dysfunctions, NK cells are an attractive source for novel immunotherapeutic strategies in this disease, including chimeric antigen receptor (CAR) therapy. Recently, satisfying clinical responses have been obtained in CLL patients using cord blood-derived CAR-NK cells, opening new possibilities for further exploring NK cells in the immunotherapy of CLL. However, notwithstanding the promising results of this clinical trial, more evidence is needed to fully understand whether and in which CLL cases NK cell-based immunotherapy may represent a valid, alternative/additional therapeutic option for this leukemia. In this review, we provide an overview of the current knowledge about phenotypic and functional alterations of NK cells in CLL and the mechanisms by which CLL cells circumvent NK cell-mediated immunosurveillance. Additionally, we discuss the potential relevance of using NK cells in CLL immunotherapy.     

Transamidation Down-Regulates Intestinal Immunity of Recombinant α-Gliadin in HLA-DQ8 Transgenic Mice

Enzymatic transamidation of gliadins by microbial transglutaminase (mTG) inhibits interferon-γ (IFN-γ) secretion by intestinal T cell lines in patients with celiac disease (CD). To gain insight into the cellular mechanisms underlying the down-regulatory effects of transamidation, we tested a single recombinant α-gliadin (r-gliadin) harbouring two immunodominant peptides, p13 (aa. 120–139) and p23 (aa. 220–239), in HLA-DQ8 transgenic mice, a model of gluten sensitivity. Mice were intranasally immunised with r-gliadin or r-gliadin transamidated by mTG (K-r-gliadin) along with cholera toxin, and the response of mesenteric lymph node cells was analysed by cytokine multiplex assay. An in vitro challenge with r-gliadin was characterised by secretion of specific cytokines featuring both innate immunity and the Th1/Th2/Th17 pattern of the adaptive response. Notably, transamidation specifically down-regulated the Th1 response. Structural studies performed on K-r-gliadin confirmed that specific glutamine residues in p13 and p23, previously found to be deamidated by tissue transglutaminase, were also transamidated by mTG. In silico analysis, simulating p13 and p23 peptide binding to HLA-DQ8 showed that these glutamines, in the form of glutamate, could interact by means of salt bridges with peculiar amino acids of the alpha chain of HLA-DQ8, suggesting that their transamidation may influence the HLA-restricted recognition of these peptides. Thus, the structural findings provided a rationale to explain the down-regulation of the r-gliadin-specific Th1 response following transamidation.     

Thiazolium‐Based Catalysts for the Etherification of Benzylic Alcohols under Solvent‐Free Conditions

Thiazolium and imidazolium hybrid materials were prepared by radical reactions between a mercaptopropyl‐modified SBA‐15 mesoporous silica and bis‐vinylthiazolium or bis‐vinylimidazolium dibromide salts. These hybrid materials were characterized by several techniques and were employed in the etherification reaction of 1‐phenylethanol. Solvent‐free conditions at 160 °C under different gas phases (oxygen, air, nitrogen and argon) were used. The thiazolium‐based material displayed excellent performances. Further studies were carried out using unsupported thiazolium salts, with or without a methyl group at the C‐2 position of the thiazolium moiety. These studies allowed us to propose a reaction mechanism. The supported thiazolium‐based material was successfully used in the etherification reaction of two other benzylic alcohols and also in seven consecutive cycles. This work represents the first use of thiazolium‐based compounds as catalysts for the etherification reaction of alcohols.

     

Impact Dynamics on Granular Plate

In this paper, a theoretical and numerical study on the impact of a rubber solid on the free surface of a granular plate is presented, showing a simulation of an aircraft wheel on impact with a flexible landing surface. This physical action, when we use a theological approach, becomes a fundamental parameter to investigate wear and tear, and consequently strength to micro and macro pavements failure. The study has developed initially from a microscopic point of view and subsequently on macroscale. The effects are strictly linked with material degradation associated with damage evolution. The problem is developed by energetic approach on an elastic-plastic element using the functional energy containing two contributions, bulk and surface. The model simulates the behaviour of flexible runway pavements during the landing phase.     

Quantum Erasure of Decoherence

We consider the classical algebra of observables that are diagonal in a given orthonormal basis, and define a complete decoherence process as a completely positive map that asymptotically converts any quantum observable into a diagonal one, while preserving the elements of the classical algebra. For quantum systems in dimension two and three any decoherence process can be undone by collecting classical information from the environment and using such an information to restore the initial system state. As a relevant example, we illustrate the quantum eraser of Scully et al. [Nature 351, 111 (1991)] as an example of environment-assisted correction, and present the generalization of the eraser setup for d-dimensional systems. Presented at the 38th Symposium on Mathematical Physics “Quantum Entanglement & Geometry”, Toruń, June 4–7, 2006.