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Piperine has several well-documented anti-inflammatory properties; however, little is known regarding its effect on humoral immunity. In this study, we describe the immunosuppressive effect of piperine on B lymphocytes, which are integral to the humoral immune response. Mouse B cells were cultured in the absence or presence of non-cytotoxic concentrations (25, 50, and 100 μM) of piperine during T-dependent or T-independent stimulation. Piperine inhibited B cell proliferation by causing G0/G1 phase cell cycle arrest in association with reduced expression of cyclin D2 and D3. The inhibitory effect of piperine was not mediated through transient receptor potential vanilloid-1 ion channel (TRPV1) because piperine also inhibited the proliferation of B cells from TRPV1-deficient mice. Expression of class II major histocompatibility complex molecules and costimulatory CD40 and CD86 on B lymphocytes was reduced in the presence of piperine, as was B cell-mediated antigen presentation to syngeneic T cells. In addition, piperine inhibited B cell synthesis of interleukin (IL)-6 and IL-10 cytokines, as well as IgM, IgG2b, and IgG3 immunoglobulins. The inhibitory effect of piperine on B lymphocyte activation and effector function warrants further investigation for possible application in the treatment of pathologies related to inappropriate humoral immune responses. Copyright © 2017 John Wiley & Sons, Ltd.

Essential oils show promise as natural alternatives to synthetic tick repellents, but few studies have investigated their repellent efficacy in vivo or under field conditions. Here, blanket-drags and standardised walks were employed to evaluate tick acquisition by 1 m2 cotton blankets or cotton trousers, respectively, in woodland edge habitats of known high tick abundance. Blankets and trousers had been treated with one of 5% oregano, rosemary, spearmint or thyme oils, 20% DEET (N,N-diethyl-3-methylbenzamide) (positive control) or ethanol excipient-only (negative control). The number of ticks present on the blankets or trousers differed significantly between treatments: spearmint oil treatments resulted in significantly fewer ticks than the negative controls for both blankets and trousers and significantly fewer ticks were present on the oregano oil treated blankets. For ticks that did attach to the trousers, the rate of drop off within 3 min was significantly higher for trousers treated with spearmint oil or thyme oil than ethanol, oregano oil and rosemary oil. No reduction in repellence was detected over a 24 h period between treatment and testing. The results suggest that 5% oregano and spearmint oils exhibit potential as natural clothing repellents, with an effective equivalence to 20% DEET.

The specific autophagic elimination of mitochondria (mitophagy) plays the role of quality control for this organelle. Deregulation of mitophagy leads to an increased number of damaged mitochondria and triggers cell death. The deterioration of mitophagy has been hypothesized to underlie the pathogenesis of several neurodegenerative diseases, most notably Parkinson disease. Although some of the biochemical and molecular mechanisms of mitochondrial quality control are described in detail, physiological or pathological triggers of mitophagy are still not fully characterized. Here we show that the induction of mitophagy by the mitochondrial uncoupler FCCP is independent of the effect of mitochondrial membrane potential but dependent on acidification of the cytosol by FCCP. The ionophore nigericin also reduces cytosolic pH and induces PINK1/PARKIN-dependent and -independent mitophagy. The increase of intracellular pH with monensin suppresses the effects of FCCP and nigericin on mitochondrial degradation. Thus, a change in intracellular pH is a regulator of mitochondrial quality control.

For many pathogenic members of the Enterobacterales, siderophores play an important role in virulence, yet the siderophores of the host-associating members of the genus Pantoea remain unexplored. We conducted a genome-wide survey of environmental and host-associating strains of Pantoea to identify known and candidate siderophore biosynthetic clusters. Our analysis identified three clusters homologous to those of enterobactin, desferrioxamine, and aerobactin that were prevalent among Pantoea species. Using both phylogenetic and comparative genomic approaches, we demonstrate that the enterobactin-like cluster was present in the common ancestor of all Pantoea, with evidence for three independent losses of the cluster in P. eucalypti, P. eucrina, and the P. ananatis—P. stewartii lineage. The desferrioxamine biosynthetic cluster, previously described and characterized in Pantoea, was horizontally acquired from its close relative Erwinia, with phylogenetic evidence that these transfer events were ancient and occurred between ancestral lineages. The aerobactin cluster was identified in three host-associating species groups, P. septica, P. ananatis, and P. stewartii, with strong evidence for horizontal acquisition from human-pathogenic members of the Enterobacterales. Our work identifies and describes the key siderophore clusters in Pantoea, shows three distinct evolutionary processes driving their diversification, and provides a foundation for exploring the roles that these siderophores may play in human opportunistic infections.

Mucosa associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is not only an intracellular signaling scaffold protein but also a paracaspase that plays a key role in the signal transduction and cellular activation of lymphocytes and macrophages. However, its role in endothelial cells remains unknown. Here we report that pharmacological inhibition of MALT1 protease activity strongly suppresses endothelial activation via enhancing MCPIP1 expression. Treatment with MALT1 protease inhibitors selectively inhibited TNFα-induced VCAM-1 expression in HUVECs and LPS-induced VCAM-1 expression in mice. In addition, Inhibition of MALT1 protease activity also significantly inhibited TNFα-induced adhesion of THP-1 monocytic cells to HUVECs. To explore the mechanisms, MALT1 inhibitors does not affect the activation of NF-κB signaling pathway in HUVEC. However, they can stabilize MCPIP1 protein and significantly enhance MCPIP1 protein level in endothelial cells. These results suggest that MALT1 paracaspase also targets MCPIP1 and degrade MCPIP1 protein in endothelial cells similar as it does in immune cells. Taken together, the study suggest inhibition of MALT1 protease activity may represent a new strategy for prevention/therapy of vascular inflammatory diseases such as atherosclerosis.

Nicolas (Nick) Bruce Myant, DM, FRCP, who died on January 17, 2015 aged 97, was widely acknowledged as one of the leading European researchers into lipid metabolism, whose pioneering studies of whole body cholesterol turnover in human subjects made a major contribution to our current understanding of hypercholesterolaemia (Fig. 1).

Ana Catarina Alves, colaboradora do grupo de investigação cardiovascular do Departamento da Promoção da Saúde e Prevenção de Doenças Não Transmissíveis do INSA, IP e aluna de doutoramento da Faculdade de Ciências da Universidade de Lisboa recebeu com este estudo, no dia 2 de junho de 2014, o Prémio Jovem Investigador atribuído pela Sociedade Europeia de Aterosclerose. Familial hypercholesterolaemia (FH) is characterized by increased circulating low-density lipoprotein (LDL) cholesterol leading to premature atherosclerosis and coronary heart disease. Although FH is usually caused by mutations in LDLR, mutations in APOB and PCSK9 also cause FH but only a few mutations have been reported, APOB p.R3527Q being the most common. However, 30-80% of clinical FH patients do not present an identifiable mutation in any of the described genes. To identify the genetic cause of the hypercholesterolaemia in 65 patients without mutations in LDLR, PCSK9 or in fragments of exon 26 and 29 of APOB currently analysed, we performed whole sequencing of APOB by pyrosequencing. A total of 10 putative mutations in APOB were identified. Flow cytometry with fluorescently labelled LDL from patients and relatives showed that p.Arg1164Thr (exon 22) and p.Gln4494del (exon 29) presented a 40% decrease in internalization in lymphocytes and HepG2 cells, very similar to APOB3527. The proliferation assays with U937 cells showed reduced growth for both cases. The variant p.Tyr1247Cys was found to be neutral and other three alterations were considered polymorphisms. Our results emphasize the need to study the whole APOB in routine protocols to improve patient identification and cardiovascular risk assessment.

Titanium dioxide (TiO2) films are deposited on quartz substrates by atmospheric pressure (AP)CVD, and then annealed under simulated air (80% nitrogen, 20% oxygen) at temperatures from 600 to 900 °C to investigate the change in microstructure and the effect on the photocatalytic activity on the simulated pollutant stearic acid. The as-deposited TiO2 film is mainly composed of pure anatase phase while the rutile phase is detected only after annealing the film at 900 °C for 1 h. The photocatalytic activity of the annealed films on stearic acid under UV irradiation is found to deteriorate after the films are annealed at temperatures above 700 °C. This decrease in photocatalytic performance is observed to be the result of two possible mechanisms induced by the annealing temperature. The first mechanism is the increase in defect concentration (O− and Ti vacancies) in the annealed TiO2 films for annealing temperatures below 800 °C, and the second mechanism is the formation of large rutile grains at a higher temperature, 900 °C.

Aims: To determine the relative frequency of mutations in three different genes (low-density lipoprotein receptor (LDLR), APOB, PCSK9) , and to examine their effect in development of coronary heart disease (CHD) in patients with clinically defined definite familial hypercholesterolaemia in UK. Patients and methods: 409 patients with familial hypercholesterolaemia patients (158 with CHD) were studied. The LDLR was partially screened by single-strand conformational polymorphism (SSCP) (exons 3, 4, 6–10 and 14) and by using a commercial kit for gross deletions or rearrangements. APOB (p.R3500Q) and PCSK9 (p.D374Y) were detected by specific assays. Coding exons of PCSK9 were screened by SSCP. Results: Mutations were detected in 253 (61.9%) patients: 236 (57.7%) carried LDLR , 10 (2.4%) carried APOB p.Q3500 and 7 (1.7%) PCSK9 p.Y374. No additional mutations were identified in PCSK9 . After adjusting for age, sex, smoking and systolic blood pressure, compared to those with no detectable mutation, the odds ratio of having CHD in those with an LDLR mutation was 1.84 (95% CI 1.10 to 3.06), for APOB 3.40 (0.71 to 16.36), and for PCSK9 19.96 (1.88 to 211.5; p = 0.001 overall). The high risk in patients carrying LDLR and PCSK9 p.Y374 was partly explained by their higher pretreatment cholesterol levels ( LDLR , PCSK9 and no mutation, 10.29 (1.85), 13.12 and 9.85 (1.90) mmol/l, respectively, p = 0.001). The post-statin treatment lipid profile in PCSK9 p.Y374 carriers was worse than in patients with no identified mutation (LDL-C, 6.77 (1.82) mmol/l v 4.19 (1.26) mmol/l, p = 0.001, HDL-C 1.09 (0.27) mmol/l v 1.36 (0.36) mmol/l, p = 0.03). Conclusions: The higher CHD risk in patients carrying PCSK9 p.Y347 or a detected LDLR mutation supports the usefulness of DNA testing in the diagnosis and management of patients with familial hypercholesterolaemia. Mutations in PCSK9 appear uncommon in patients with familial hypercholesterolaemia in UK.

The yttrium alkyl carbene complex [Y(BIPM)(CH2Ph)(THF)] (1; BIPM = {C(PPh2NSiMe3)2})2–) was treated with a series of unsaturated organic substrates, a bulky primary amine, and a group 1 metal alkyl to gauge and compare the reactivity of the Y═Ccarbene and Y–Calkyl bonds. Treatment of 1 with tert-butyl nitrile and 1-adamantyl azide gave the 1,2-migratory insertion products [Y(BIPM){NC(But)(CH2Ph)}(THF)] (2) and [Y(BIPM){N3Ad-1,Bn-3-κ2N1,3}(THF)] (3), respectively, with no reactivity observed at the Y═C double bond even when an excess of the relevant organic substrate was added. In contrast, the heteroallenes N,N′-dicyclohexylcarbodiimide and tert-butyl isocyanate reacted at both the Y═Ccarbeneand Y–Calkyl bonds of 1 to afford [Y{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}{C(NCy)2(CH2Ph)-κ2N,N′}] (4) and [Y{C(PPh2NSiMe3)2[C(O)(NBut)]-κ4C,N,N′,O}{C(O)(NBut)(CH2Ph)-κ2N,O}] (5), respectively. 4 and 5 form regardless of the molar ratio of 1 to heteroallene, with no intermediates observed; thus, it is not clear if the ...

Time-resolved anisotropy measurements (TRAMS) have provided invaluable information concerning the molecular interactions responsible for cononsolvency in the poly(N-isopropylacrylamide), PNIPAM, H2O, and methanol ternary system. TRAMS have successfully monitored the intramolecular segmental dynamics of an acenaphthylene labelled sample, ACE–PNIPAM, revealing details about the conformation adopted by the polymer constituent as a function of both alcohol composition and temperature of the system. In pure aqueous solution, ACE–PNIPAM undergoes a conformational transition from an expanded solvent swollen structure to a compact globule at the lower critical solution temperature (LCST). With increasing alcohol content up to 55% v/v of methanol there is both a reduction in the magnitude and an onset temperature of the LCST of ACE–PNIPAM. From 57.5–65% v/v methanol, ACE–PNIPAM forms an extended solvent swollen structure: observation of an LCST at higher polymer concentrations (e.g., 0.1 wt%) is a consequence of intermolecular aggregation between expanded chains.

This paper reports on the first observation of phosphorescence emission in a thermoresponsive polymer in aqueous media. Random copolymerization of N-isopropylacrylamide, NIPAM, with bromostyrene, BrSTY, promotes efficient intersystem crossing into the triplet manifold, via the heavy atom effect, in an acenaphthylene label allowing generation of emission on a millisecond time scale. Luminescence techniques such as fluorescence time-resolved anisotropy, excited-state lifetime, and pyrene solubilization experiments have proven useful in probing the effects of heavy atom modification upon the thermoresponsive behavior of PNIPAM: BrSTY alters the hydrophobic/hydrophilic balance and serves to decrease the lower critical solution temperature, LCST, of the resultant polymer. The LCST is marked by a change in conformation of the macromolecule form an expanded water-swollen structure to a compact globule. The globular form of the BrSTY-modified polymer samples is so protective that phosphorescence emission is susta...

A 2-part epoxy-siloxane coating cured with amino silane has been developed to provide corrosion protection on carbon steel (CRSS) using dip-coating to deposit a two layer structure. Amino silane served both as hardener, reacting with the epoxide group to initiate crosslinking, and as coupling agent to enhance adhesion of hybrid polymer resin to the metal surface. Corrosion resistance in different chemical media and mechanical properties of the coating were systematically studied and characterised. It is found that prehydrolysed amino silane can speed up drying of epoxy-siloxane coatings, touch dry coatings are obtained within 1 h. Coating materials employing a mixed solvent of ethanol and methyl ethyl ketone exhibited a longer pot life, and the resultant coatings showed no degradation of their corrosion resistance after one month chemical immersion tests in alkaline, acidic and saline conditions. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion properties of these coatings.

Two types of cationic dye, Rhodamine 6G (R6G) and Methylene Blue (MB), intercalated bentonite have been developed to visualize latent fingerprints. The dyes were first absorbed on bentonite particles by an ion exchange process and the particle surface was subsequently modified by phenyltrimethoxysilane (PTMOS). Resulting particles retained incorporated dye with good affinity and their surfaces were rendered organophilic due to the planar aromatic ring of PTMOS grafted on the surface and edges of layered bentonite particles. Such organophilic properties promoted attachment of particles to finger mark residues. Particles were harvested as a powder and applied as a dusting agent using brushes.

In this review we present data highlighting the power and versatility of luminescence spectroscopy in the study of the conformational behaviour of poly(N-isopropyl acrylamide) (PNIPAM). PNIPAM shows a lower critical solution temperature (LCST) in aqueous solution at 32 °C. Fluorescence time-resolved anisotropy measurements (TRAMS) have confirmed that a conformational change occurs from an expanded open chain to a globular structure at the LCST, which forms the basis of phase separation observed for semi-dilute concentrations. The coiled conformation can solubilise low-molar-mass species as revealed by the spectral profile of pyrene and is extremely protective: intersystem crossing to the triplet manifold can be enhanced by use of a heavy-atom promoter (bromostyrene) copolymerised with NIPAM and trace levels of acenaphthylene allowing generation of phosphorescence at temperatures as high as 50 °C in aqueous solution. Manipulation of the conformational switch of PNIPAM is possible via simple free radical copolymerisation. However, a reduction in the magnitude of the transition occurs, which has an impact on the solubilisation properties of the resultant copolymers. Alternative strategies are suggested to overcome this problem: synthesis of graft copolymers allows fine-tuning of the thermal response whilst maintaining the magnitude of the transition as revealed by TRAMS. Copyright © 2009 Society of Chemical Industry

Thermal-cured coatings based on 3-glycidoxypropyltrimethoxysilane (GLYMO) have been prepared by a sol-gel process for use as corrosion resistant coatings on copper. GLYMO possesses both epoxy and silicon alkoxide functionality and so inter-linked inorganic–organic networks can be formed. It is found that corrosion resistance is enhanced by the addition of 3-mercaptopropyltrimethoxysilane (TPTMS), which improves adhesion of coatings to substrates. Coatings with suitable curing agent exhibited better corrosion resistance and longer pot life. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion properties of these coatings.

Objective: The combination of simvastatin, an HMG-CoA reductase inhibitor, and ezetimibe, an inhibitor of Niemann-Pick C1-like 1 protein, decreases cholesterol synthesis and absorption and reduces circulating LDL-cholesterol concentrations. The molecular mechanisms underlying the pronounced lipid-lowering effects of this combination have not been fully elucidated in humans. Methods and results: One center, prospective, randomized, parallel three-group study in 72 healthy men (mean age 32 ± 9 years, mean body mass index 25.7 ± 3.2 kg/m 2 ). Each group of twenty-four subjects received a 14-day treatment with either ezetimibe (10 mg/day), simvastatin (40 mg/day) or their combination. Lipid levels, the ratio of non-cholesterol sterols to cholesterol concentrations (used as markers of cholesterol synthesis and absorption), cell surface LDL receptor (LDLR) protein as well as LDLR and HMG-CoA reductase gene expression in mononuclear blood cells were measured at baseline and at the end of the study. LDL-C decreased in all groups. Simvastatin decreased, ezetimibe increased and their combination had no effect on HMG-CoA reductase activity. Simvastatin and the combination of ezetimibe and simvastatin increased the HMG-CoA reductase and LDLR gene expression while ezetimibe had no effect. The cell surface LDLR protein expression remained unchanged in all groups. The combination of ezetimibe and simvastatin increased the expression of the serine protease proprotein convertase subtilisin/kexin 9 (PCSK9), an enzyme shown to down-regulate LDLR protein levels. Conclusions: The co-administration of ezetimibe and simvastatin abrogates the ezetimibe-induced increase in cholesterol synthesis and up-regulates the LDLR gene but not protein expression, an effect possibly mediated through a parallel upregulation of PCSK9 expression. © 2007 Elsevier Ireland Ltd. All rights reserved.

Poly(methacrylic acid) (PMAA) undergoes a conformational transition between pH 4 and 6 from a hypercoiled structure to a water-swollen state. There has been much speculation as to the exact nature and driving force of the transition. In this paper, we present a comprehensive investigation of the conformational switch of PMAA using techniques which report on various length scales: fluorescence energy transfer experiments provide unique information on the nanometer length scale while dynamic light scattering (DLS) offers an insight into longer range interactions involved in the transition. Fluorescence energy transfer measurements demonstrate that PMAA undergoes subtle molecular rearrangements between pH 2 and 5 as short-range hydrophobic interactions between methyl groups are broken down by increasing concentrations of mutually repulsive carboxylate anions. Although such rearrangements have been proposed to account for the pH behavior of PMAA, we reveal them experimentally using techniques sensitive to na...

Autosomal recessive hypercholesterolaemia (ARH), characterized clinically by severe inherited hypercholesterolaemia, is caused by recessive null mutations in LDLRAP1 (formerly ARH). Immortalized lymphocytes and monocyte-macrophages, and presumably hepatocytes, from ARH patients fail to take up and degrade plasma low density lipoproteins (LDL) because they lack LDLRAP1, a cargo-specific adaptor required for clathrin-mediated endocytosis of the LDL receptor. Surprisingly, LDL-receptor function is normal in ARH patients' skin fibroblasts in culture. Disabled-2 (Dab2) has been implicated previously in clathrin-mediated internalization of LDL-receptor family members, and we show here that Dab2 is highly expressed in skin fibroblasts, but not in lymphocytes. SiRNA-depletion of Dab2 profoundly reduced LDL-receptor activity in ARH fibroblasts as a result of profound reduction in LDL-receptor protein, but not mRNA; heterologous expression of murine Dab2 reversed this effect. In contrast, LDL-receptor protein content was unchanged in Dab-2-depleted control cells. Incorporation of 35S-labelled amino acids into LDL receptor protein revealed a corresponding apparent reduction in accumulation of newly synthesized LDL-receptor protein on depletion of Dab2 in ARH, but not in control, cells. This reduction in LDL-receptor protein in Dab2-depleted ARH cells could not be reversed by treatment of the cells with proteasomal or lysosomal inhibitors. Thus, we propose a novel role for Dab2 in ARH fibroblasts, where it is apparently required to allow normal translation of LDL receptor mRNA.

Research has concentrated on thermally cured packaging materials, with little effort directed at UV-curable systems. The aim of this work is to study the characteristics of a UV-curable Polyurethane Acrylate (PUA) processed under different UV curing conditions, as well as to monitor changes in its properties upon aging under room temperature conditions and in corrosive solvent environments. The PUA system was observed to possess a dual cure mechanism. Different UV conditions yield PUA with varying modulus; however, the modulus eventually converge and approach a plateau with prolonged staging under ambient conditions, due to interaction with moisture. Annealing was found to assist in accelerating moisture cure reaction, which facilitates stable material properties within a shorter ambient staging time. In addition, the degradation in properties occurring when cured materials come into contact with a corrosive solvent environment was also studied.

In this article we present recent data highlighting the power of (fluorescence) time-resolved anisotropy measurements (TRAMs) in the study of the thermoresponsive behaviour of poly( N -isopropylcrylamide), PNIPAM, and NIPAM-based systems. PNIPAM shows a lower critical solution temperature (LCST) at 32 °C when phase separation occurs as the macromolecule collapses into a globular structure. Manipulation of the conformational switch of PNIPAM results through changing the hydrophobic to hydrophilic balance within the polymer. However, although a degree of control of the LCST is possible through such a strategy, simple free radical copolymerisation serves to reduce the magnitude of the transition. Synthesis of graft copolymers based on NIPAM is offered as a solution to this problem: fine tuning of the thermal response results through control of the entropic term governing the thermodynamics of the process as revealed by TRAMs. Independent fluorescence labelling of both the backbone and the grafts allows the contribution of the chain dynamics from each of these sites to the thermal response to be monitored.

Time-resolved anisotropy measurements (TRAMS) have been used to study the relaxation behaviour of poly(butyl methacrylate) (PBMA) in dilute solution both in toluene and dichloromethane. Various fluorescent labels (residues from copolymerisation of BMA with ca 0.3 mol% of acenaphthylene (ACE), 1-vinylnaphthalene (VN), 1-naphthylmethyl methacrylate, 9-phenyanthrylmethyl methacrylate, and 9-anthrylmethyl methacrylate (AMMA)) were used. It was found that, as expected, ACE and VN provided information on the segmental motion of PBMA. The fluorescence anisotropies of the various ester labels reflected the influence of motion, independent of that of the PBMA backbone, upon the observed relaxation behaviour. The motion of AMMA, in particular, could be resolved, with confidence, into components corresponding to segmental relaxation of both the polymer and ester group motion. Clearly, in this system, motion of the labelled ester is not fully cooperative with that of the polymer backbone, even at the high test frequencies to which these fluorescence measurements correspond. Copyright © 2005 Society of Chemical Industry

The synthesis and characterization of poly(N-isopropyl acrylamide) (PNIPAM), which has been grafted to polystyrene, are described. Despite the fact that these copolymers contain around 20 % of the hydrophobic monomer styrene, they still retain water solubility below 32 °C. Such observations imply that altering the polymer topography provides an alternate strategy for manipulation of the lower critical solution temperature (LCST). The fluorescence characteristics of the polarity probe, pyrene, have been used to provide information regarding the thermoresponsive behaviour of the grafted copolymer samples. On the basis of these measurements, a model is proposed which suggests that a hydrophobic styrene core exists at all temperatures between 5 and 60 °C, which is stabilized by a hydrophilic ‘corona’ formed by the PNIPAM grafts. The LCST marks a conformational ‘collapse’ of the grafts onto the styrene core, which results in the formation of a compact globular species. The fluorescence data also provide evidence that the PNIPAM graft chain-length influences the nature of the globule. Copyright © 2005 Society of Chemical Industry

Fluorescence techniques, particularly time-resolved anisotropy measurements, TRAMS, have confirmed that poly( N -vinylcaprolactam), PNVCap, undergoes a conformational transition from an expanded coil to a compact globule at its lower critical solution temperature, LCST. TRAMS and cloud point measurements have revealed the onset of the LCST as 38 °C. The nature of the conformational change for PNVCap is distinct from that of another thermoresponsive polymer, poly( N -isopropylacrylamide), PNIPAM: the discontinuity in the thermal dependence of the rate of macromolecular motion occurs over a range of ca. 15 °C for PNVCap while that for PNIPAM takes place between 31 and 33 °C. Furthermore, there is a reduction in the magnitude of the conformational change of PNVCap when compared to that of PNIPAM. Pyrene solubilisation experiments provide support for a model for PNVCap above the LCST, consisting of a globular structure with a hydrophobic core which is stabilised by more hydrophilic units on the surface.

A study of the interaction of commercial black ink with a UV-curable polyurethane acrylate (PUA) is presented. Diffusivity and solubility in PUA cured using different UV dosages, and subjected to different post-UV curing conditions, were studied, as was the swelling produced by such sorption. Experiments were also conducted using water, to serve as a benchmark and compare with the effect of ink. The percentage ink absorption was found to decrease with higher degree of cure. In addition, through desorption measurements, ink induced swelling of PUA processed under different conditions was determined. The degree of swelling per unit solvent uptake was observed to increase with the degree of cure. PUA was determined to be more prone to moisture rather than solvent uptake. However, the coefficient of moisture expansion (CME) was found to be ∼ 35% lower than the coefficient of ink expansion (CIE) for a fully cured PUA. © 2006 Wiley Periodicals, Inc. JAppl PolymSci 103: 1985–1991, 2007

Fluorescence-quenching measurements have been made on five differently labelled poly(n-butyl methacrylate) latices. The accessibility of the fluorescent label to a freely diffusing quencher (nitromethane, in the case of the current study) gives information on the label's micro-environment. However, it is shown that this is not (necessarily) relevant to considerations of the particle morphology in the absence of the label: the presence of the label during formation of the latex influences the nature of the domain in which it is finally located. Used with caution, fluorescence quenching is capable of yielding information regarding the morphology of polymer latices, especially when complemented by other techniques, such as rheology measurements or small angle neutron scattering. Copyright © 2005 Society of Chemical Industry

Objective— Analysis of long-term (30 years) clinical history and response to treatment of 13 patients with the D374Y mutation of PCSK9 (PCSK9 patients) from 4 unrelated white British families compared with 36 white British patients with heterozygous familial hypercholesterolemia attributable to 3 specific mutations in the low-density lipoprotein (LDL) receptor gene ( LDLR ) known to cause severe phenotype. Methods and Results— The PCSK9 patients, when compared with the LDLR patients, were younger at presentation (20.8±14.7 versus 30.2±15.7 years; P =0.003), had higher pretreatment serum cholesterol levels (13.6±2.9 versus 9.6±1.6 mmol/L; P =0.004) that remained higher during treatment with simvastatin (10.1±3.0 versus 6.5±0.9 mmol/L; P =0.006), atorvastatin (9.6±2.9 versus 6.4±1.0 mmol/L; P =0.006), or current lipid-lowering therapy, including LDL apheresis and partial ileal bypass in 2 PCSK9 patients (7.0±1.6 versus 5.4±1.0 mmol/L; P =0.001), and were affected >10 years earlier by premature coronary artery disease (35.2±4.8 versus 46.8±8.9 years; P =0.002). LDL from PCSK9 patients competed significantly less well for binding to fibroblast LDL receptors than LDL from either controls or LDLR patients. Conclusions— These British PCSK9 patients with the D374Y mutation have an unpredictably severe clinical phenotype, which may be a unique feature for this cohort, and requires early and aggressive lipid-lowering management to prevent cardiovascular complications.

Magnesium, although valuable, is reactive and requires protection before it can be used in many applications. This study evaluates the corrosion protection of Mg by multilayer coatings. The coatings consist of an anodised layer and one or two sol–gel layers. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion properties of these coatings. A porous anodised Mg oxide layer is employed as an intermediate layer, which enhances the adhesion of sol–gel layers. Sol–gel layers provide corrosion protection by physically sealing pores in the anodised layer and acting as a barrier. Defects and porosity in the coatings are the main causes of corrosion, allowing diffusion paths for corrosive species to reach the metal surface, where they can initiate corrosion. The multilayer approach is found to significantly improve the corrosion resistance of Mg by reducing levels of porosity.

Typically, autosomal dominant familial hypercholesterolaemia (FH) is caused by mutations in the low density lipoprotein (LDL) receptor or apolipoprotein B genes that result in defective clearance of plasma LDL by the liver, but a third gene (PCSK9), encoding a putative proprotein convertase, has recently been implicated. Two independent microarray studies support a role for PCSK9 in sterol metabolism and adenoviral-mediated over-expression of PCSK9 in mouse liver depletes hepatic LDL-receptor protein, but the mechanism by which dominant mutations cause human FH is unclear. We have identified the D374Y mutant of PCSK9 in three FH families of English origin; all 12 affected individuals have unusually severe hypercholesterolaemia and require more stringent treatment than typical FH patients, who are heterozygous for defects in the LDL receptor. We have stably expressed wild-type (WT) and variant PCSK9 in McArdle-7777 rat hepatoma cells and shown by confocal microscopy that all forms of PCSK9 co-localize with protein disulphide isomerase in the ER whether or not they can be autocleaved. Expression of the proposed pathogenic variants, but not of WT, S386A or F216L PCSK9, increases secretion of apolipoprotein B100-containing lipoproteins from the cells by 2-4-fold probably by reducing the degradation of nascent protein; no differences in LDL-receptor content were observed in cells expressing WT, S386A or F216L PCSK9 and only a small reduction in cells expressing the D374Y or S127R mutants. This suggests that the variants of PCSK9 found in FH influence the secretion of apoB-containing lipoproteins, providing an explanation for the marked increase in circulating LDL in heterozygous carriers.

Autosomal recessive hypercholesterolaemia (ARH) is caused by mutations in ARH on chromosome 1p35-36, encoding a putative adaptor protein. Mutations in the gene prevent normal internalisation of the low density lipoprotein (LDL) receptor by cultured lymphocytes and monocyte-derived macrophages, but not skin fibroblasts. This newly identified disorder is characterised by severe hypercholesterolaemia, large tendon, tuberous and planar xanthomas and premature atherosclerosis. We describe long-term (9-23 years) follow up and response to treatment of eight subjects with ARH from four families (Turkish/Lebanese, Indian-Asian, English and Italian). The clinical phenotype of ARH is similar to that of classical homozygous familial hypercholesterolaemia (FH) caused by mutations in the LDL-receptor gene but is more variable, less severe and is more responsive to lipid-lowering therapy with bile acid sequestrants and/or HMG-CoA reductase inhibitors. The latter reduced total serum cholesterol by up to 60% and the former by 20-35%. The cardiovascular complications of premature atherosclerosis seem to be delayed in some individuals and the involvement of the aortic root and valve are rarer in comparison with homozygous FH.

Various fluorescence techniques and cloud point measurements have been used to study the effects of altering the hydrophilic/hydrophobic balance in a series of N-isopropylacrylamide (NIPAM)/N,N-dimethylacrylamide (DMAC) statistical copolymers upon the smart thermal responses of these systems in dilute aqueous solution. As expected, incorporation of DMAC into the polymer structure raises its lower critical solution temperature to an extent dependent upon DMAC content. However, use of such a hydrophilic modifier reduces the magnitude of the collapse transition that characterizes the macromolecule's thermal response. In PNIPAM, the LCST is associated with a conformational transition between a coil and a globule. However, introduction of DMAC derivatives into the polymer expands its “globular” form into a much more open structure that progressively loses its capacity for solubilization of organic guests. Consequently, although copolymerization with more polar monomers can be used to raise the LCST of NIPAM-ba...

The absorption of astaxanthin from diets (30 mg kg−1 inclusion) supplemented with either unesterified astaxanthin; isolated astaxanthin monoesters, diesters or a cell-free carotenoid extract from Haematococcus pluvialis were studied in rainbow trout (>200 g). No significant differences (P > 0.05) were recorded in the apparent digestibility coefficients (ADC) (≈60–65%) between astaxanthin sources. However, following consumption of a single meal, peak serum astaxanthin levels at 32 h (≈1.0–1.6 μg mL−1) were significantly higher (P 0.05) were recorded in serum astaxanthin uptake rates between sources of astaxanthin. Results suggest that the extent of carotenoid esterification negatively influences the peak serum levels of astaxanthin in rainbow trout.

Electrically colourable (“electrochromic”) windows, hitherto confined to small areas, have recently been much expanded in area in new aircraft windows. Reviews indicate that to extend such high-tech applications to more everyday uses requires enhanced robustness, as in a new Prussian-Blue/polymer(Li+)/WO3 electrochromic device reported here. The new polymer electrolyte is UV-curable within the cell, obviating the need and risk of thermal polymerization while conferring mechanical robustness. Prussian Blue, (in reduced form the clear Prussian white “PW”, that is turned blue on electro-oxidation) and WO3 (showing a complementary clear-to-blue on electron uptake) are known to reliably undergo these established colourations as electrochromic anode and cathode, respectively.

The deposition of natural, optically active, astaxanthin fatty acid esters in rainbow trout (Oncorhynchus mykiss) was studied. Mono-esterified and di-esterified (3S,3¢S) astaxanthin were purified from the green microalga Haematococcus pluvialis and incorporated into extruded diets and compared with diets containing synthetic racemic astaxanthin (Carophyll Pink) and a total carotenoid extract from the alga. All sources of astaxanthin achieved >4 mg kg )1 in the white muscle after 6 weeks feeding. No significant diAerence (P > 0.05) between the deposition of astaxanthin or total carotenoid for the diAerent diets was observed. Other xanthophylls, namely lutein, zeaxanthin and idoxanthin were found in the white muscle of rainbow trout fed all diets and together accounted for 10‐14% of total carotenoid. Astaxanthin was deposited in the white muscle in the stereochemical form administered in the diet, i.e. racemic astaxanthin for Carophyll Pink and 100% (3S,3¢S)-astaxanthin for the algal sources. In contrast, epimerization of (3S,3¢S) astaxanthin from the alga was observed for the astaxanthin esters deposited in the skin of rainbow trout, with a ratio close to 1.0:2.0:1.0 (3S,3¢S:3R,3¢S:3R,3¢R).

Fluorescence techniques, including time-resolved (fluorescence) anisotropy (TRAMS), have been used to study the effects of hydrophobic modification upon the thermoresponsive behavior of NIPAM-based polymers. Incorporation of styrene, through statistical free radical copolymerization, changes the hydrophobic/hydrophilic balance of the macromolecule and lowers the lower critical solution temperature (LCST) of the system. Unfortunately, although simple copolymerization with styrene can be used to manipulate the system's LCST characteristics, the polymer loses its ability to release solubilized hydrophobic guests below the critical point. This results from the formation of intramolecular aggregates between the styryl residues of the polymer chain, which can accommodate guest solutes. This is a serious limitation to this form of chemical modification if the aim is to produce smart materials for controlled solubilization and release at specific temperatures.

Poly(N-isopropylacrylamide), PNIPAM, undergoes phase separation, upon heating under semi-dilute conditions, at 32°C, the lower critical solution temperature (LCST). Upon subsequent cooling, the dispersion rapidly clears again, at the LCST, to form a single, homogeneous phase. In this paper we report that fluorescence techniques, including quenching and time-resolved anisotropy measurements (TRAMS) on ultra-dilute (10−3 wt%) aqueous solutions of an acenaphthylene labelled sample, provide conclusive evidence that a coil collapse mechanism is implicated in the thermoreversible behaviour: the polymer undergoes a conformational switch from an open coil below 32°C to a compact, globular structure above the LCST. TRAMS reveal that a marked reduction in the segmental mobility of the polymer occurs at the onset of the LCST. In addition, a dramatic change in the accessibility of the label to aqueous-borne quenchers is also apparent at temperatures in excess of 32°C. PNIPAM is capable of solubilising low molar mass species in its compact form: changes in the vibrational fine structure of the emission spectrum of pyrene have been used to monitor uptake and release of the probe. Excited state lifetime measurements have also proven to be sensitive monitors of the conformational switch of PNIPAM: at temperatures greater than 32°C, τ increases to ca. 160 ns which is indicative of pyrene sequestered in a hydrophobic, protective environment. Release of the probe into the aqueous phase results in a dramatic reduction of τ to ca. 130 ns which is characteristic of pyrene dispersed in water. These data highlight the potential of NIPAM based polymers to act as carriers in controlled release applications. Fluorescence techniques have proved capable of monitoring changes in chain mobility, the degree of coil compaction and solubilization capacity (for organic guests) of PNIPAM as it is raised through its LCST. Information of this type is not readily obtained through other techniques and fluorescence approaches should prove invaluable in future investigations of the effects of chemical modification in attempts to manipulate the LCST of NIPAM-based systems.

Abstract —Interindividual variability in low density lipoprotein (LDL) cholesterol (LDL-C) response during treatment with statins is well documented but poorly understood. To investigate potential metabolic and genetic determinants of statin responsiveness, 19 patients with refractory heterozygous familial hypercholesterolemia were sequentially treated with placebo, atorvastatin (10 mg/d), bile acid sequestrant, and the 2 combined, each for 4 weeks. Levels of LDL-C, mevalonic acid (MVA), 7-α-OH-4-cholesten-3-one, and leukocyte LDL receptor and hydroxymethylglutaryl coenzyme A reductase mRNA were determined after each treatment period. Atorvastatin (10 mg/d) reduced LDL-C by an overall mean of 32.5%. Above-average responders (ΔLDL-C −39.5%) had higher basal MVA levels (34.4±6.1 μmol/L) than did below-average responders (ΔLDL-C −23.6%, P P P P

The time-resolved fluorescence anisotropy behaviour of pyrene solubilized (10−6 M) in ultra-dilute (10−3 wt%) aqueous solutions of the thermoresponsive polymer poly(N-isopropylacrylamide), PNIPAM, shows unusual characteristics. Rather than decay to zero (as expected of a freely rotating species in a homogeneous fluid environment) the anisotropy of the emission from the probe attains a minimum but finite value, some 40 ns after excitation of the pyrene. Thereafter, over a timescale of hundreds of nanoseconds, the anisotropy increases: the fluorescence from the solubized pyrene guest becomes more polarized with time! These deviations from “expectation” are significant both in terms of the aqueous solution behaviour of the polymer and basic photophysics. The anisotropy data confirm that, above the lower critical solution temperature (LCST) of PNIPAM, the polymer host (in the form of single, “collapsed” macromolecules) is capable of solubilizing hydrophobic guests. The complexity of the time dependence of anisotropy of fluorescence from pyrene, above the LCST of the system, reflects the heterogeneous nature of the medium in which the probe is dispersed. At one extreme, we have pyrene molecules located within the bulk aqueous phase. At the other extreme, pyrene species are occluded within the hydrophobic interiors of the collapsed PNIPAM globules. The initial rapid loss in emission anisotropy reflects the contribution from shorter lived and rapidly tumbling solutes dispersed largely in the aqueous phase. The subsequent enhancement in the anisotropy at longer times, results from the ever-increasing importance of fluorescence from the longer lived, slowly rotating probes solubilized within the highly viscous cores of the globular conformation of the macromolecule. Below the polymer's LCST, most of the pyrene guest is released to the bulk aqueous phase but a proportion of the organic guests remains associated with the (otherwise) open coils of the polymer. In photophysical terms, the data presented constitute the first example of a study in which the motion of a fluorescent guest, mediated by the influence of its interactions with a synthetic polymer, appears to become more restricted as the time of sampling of its emission, following excitation, increases.

Rare earth carbenes exclusively exhibit Wittig-type reactivity with carbonyl compounds to afford alkenes. Here, we report that yttrium carbenes can effect regioselective ortho-C-H activation and sequential C-C and C-O bond formation reactions of aryl ketones to give iso-benzofurans and hydroxymethylbenzophenones. With MeCOPh, cyclotetramerization occurs giving a substituted cyclohexene. This demonstrates new rare earth carbene reactivity which complements existing Wittig-type reactivity.

The thermal dependence of the phosphorescence characteristics of benzophenone (BP) dispersed in thin films of poly(acrylic acid), PAA, and acrylic acid-methyl methacrylate, AA-MMA, copolymers is described. At all temperatures (between 77 K and 410 K), and in each of the systems studied, the triplet state decay kinetics of the phosphor are complex: a minimum of three exponential terms is required for adequate modelling of the time dependence of BP phosphorescence. This complexity is considered to reflect the breadth and heterogeneity of the distribution of sites accessed by the probe within each of the polymer matrices. Both phosphorescence intensity and lifetime measurements are affected by the onset of macromolecular relaxations within each of the film samples. However, the temperature dependence of the BP phosphorescence data seems to also reflect the presence of specific interactions between the probe and polymer. Consequently the data do not allow a definitive picture of the relaxation behaviour or phase morphology of the copolymer samples to be derived. The data also illustrate the fact that, in designing a high-performance phosphorescent coding system, trends in the photophysical characteristics of one dopant in a given matrix do not necessarily translate into predictions of the behaviour of another phosphor even in the same matrix.

The phosphorescence characteristics of naphthyl labelled poly(acrylic acid) film samples have been studied as a function of temperature, with a view to investigating the effect of matrix control on the level of triplet emission observed. Two relaxations, which serve to deactivate the excited triplet states have been detected from phosphorescence lifetime measurements: the α (or glass) and the βtransition (which can be associated with the onset of rotation of the carboxylic acid group). Investigation of the emission from 2-benzoyl naphthalene dispersed within both an acrylic acid-methyl methacrylate copolymer and a PAA film, respectively, has revealed that the more intense, longer-lived phosphorescence results from the modified polymer. This is considered to reflect the existence of (i) hydrogen-bonding interactions induced by the presence of carboxylic acid groups which serve to form a rigid matrix and (ii) intramolecular aggregates of methyl methacrylate units which create hydrophobic-rich pockets, capable of sustaining intense phosphorescence at room temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2127–2136, 1999

Familial hypercholesterolemia (FH) is caused by a defect in the function of the low density lipoprotein (LDL) receptor and inherited in an autosomal, codominant way. In this study we present a 13-year-old girl, compound heterozygote for the LDL receptor mutations C240F and Y167X. Fibroblasts from the patient showed very low cholesterol esterification rate, LDL uptake, and degradation compared to normal fibroblasts (< 2%, 8%, and < 2%, respectively). The C240F mutant was expressed in LDL receptor deficient CHOMldlA7 cells. Analysis of cell extracts by immunoblotting demonstrated delayed processing of the mutated LDL receptor, which was accumulated as a precursor protein of normal size. A high molecular weight form of the receptor was also detectable in these cells, which probably reflects cross-linking through the unpaired cysteine residue in the binding domain. Cells expressing the C240F mutant protein were unable to mediate uptake and degradation of LDL. The two siblings of the index case also carried the C240F mutation, but surprisingly one of them (a 17-year-old brother) showed no signs of hypercholesterolemia. This observation is consistent with the view that there may be cholesterol lowering mechanisms that can be activated, perhaps by mutations in known or hitherto unknown genes.

The phosphorescence characteristics of 2-benzoylnaphthalene (2BN) dispersed within thin films of poly(methyl methacrylate), poly(methyl acrylate), polystyrene and poly(acrylic acid) (PAA) respectively, are described. The excited state decay kinetics of the probe are complex in each of the macromolecular hosts studied: such behaviour is considered to result from differing degrees of phosphor–host matrix interaction but may also reflect, particularly in the case of PAA, heterogeneities within the bulk polymer phase. The thermal dependence of the intensity and average lifetime of phosphorescence of the various phosphor/polymer combinations were also investigated with a view to identifying a host matrix for a high-performance coding ink. Preliminary data indicate that the longest-lived, most intense triplet emission results from the 2BN doped PAA system.

Background: The food frequency questionnaire (FFQ) has become established as the primary method for assessing dietary intake in epidemiological studies of diet and disease; attention must now be given to developing and evaluating FFQs that extend the range of populations studied. Aim: To assess the validity of antioxidant vitamin intake estimates derived from a self-administered food frequency questionnaire which was developed for use in Scottish populations. Method: Intake estimates of vitamins A, C, E and β-carotene were compared with corresponding biochemical measurements in 273 Scottish men and women aged 39–45 years. Results: The mean ratios of energy intake to calculated basal metabolic rate were 1.40 for men and 1.46 for women suggesting that the intake values derived from the FFQ were not biased towards under-reporting. Significant positive correlation coefficients ranging from 0.14 (for vitamin A) to 0.42 (for vitamin C) were observed between total intake (including diet and supplements) and plasma values. Adjustment for other known determinants of diet and plasma values (i.e. energy intake, body mass index, gender, smoking and plasma lipid levels) improved the correlations for vitamin E and β-carotene. Excluding supplement users generally reduced the correlations suggesting that failure to include supplemental sources may result in misclassification of antioxidant vitamin intake. The food frequency questionnaire assigned 68–89% of subjects correctly into the upper or lower plus adjacent tertiles of plasma vitamin concentration. Conclusions: These results demonstrate that the food frequency questionnaire is a valid measure of antioxidant vitamin intake.

A hydrophobically modified water-soluble polymer, based upon acrylic acid and styryl derivatives, was synthesized. A proportion (ca. 75 mol%) of the styryl residues in the copolymer contain a bromine substituent as a “heavy-atom” functionality. It has been shown that room-temperature phosphorescence (RTP) can be induced in an acenaphthylene (ACE) label, covalently bound to the polymer chain, through intramacromolecular interactions in dilute solutions of the copolymer. This is the first instance in which RTP has been generated in either label or solubilized guest, in such a fashion. The conformational behavior of the functionalized copolymer, BrSTY/STY/AA, has been studied using RTP, fluorescence lifetime, and time-resolved anisotropy measurements and compared to that of both its unbrominated, styrene-modified analogue, STY/AA, and poly(acrylic acid) PAA itself. The conformation transition which accompanies conversion of each polyacid into the corresponding fully neutralized polysalt is much more dramatic in either hydrophobically modified species than in poly(acrylic acid). Intramacromolecular aggregation leading to the creation of hydrophobic domains within the coils of the macromolecules is enhanced at a low pH and severely impedes segmental motion in the two styrene-modified polyacids. The effect is greater in the bromine-containing polymer, which suggests that more densely packed domains are formed in this species than in STY/AA. In addition to altering the magnitude of the effect that neutralization has upon the molecular dynamics of the polyacid in aqueous media, hydrophobic modification raises the pH range over which the change in conformational behavior of the macromolecule is apparent.

The relationship between molecular defect and clinical phenotype has been examined in 42 patients with heterozygous familial hypercholesterolaemia (FH) and premature coronary heart disease. The defined defects included mutations in the low density lipoprotein (LDL)-receptor gene (23/42) or the apolipoprotein B Arg3500Gln mutation (5/42). Mean LDL-cholesterol was higher, both before and during treatment with simvastatin and bile acid sequestrants, in patients predicted as having a `severe' mutation than in those with a `mild' mutation (8.72±2.02 mmol/l vs 6.63±1.8, P =0.05 before and 4.51±0.90 mmol/l vs 3.19±0.58, P =0.05 during treatment). Maximum inducible LDL-receptor activity in cultured lymphoblasts was inversely correlated with LDL-cholesterol before ( r 2 =0.499, P =0.002) and during ( r 2 =0.478, P =0.004) treatment in patients with a defined mutation in the LDL-receptor gene, but not in the 14 patients with no detectable molecular defect. LDL-cholesterol concentrations before and during treatment were significantly correlated in patients with a defined LDL-receptor gene mutation ( r 2 =0.548, P =0.0001), but not in those with no detectable genetic defect. All these correlations were weak, however and there were no differences in the response to treatment in terms of either relative reduction or absolute decrease in LDL-cholesterol concentration between patients with different LDL-receptor defects. We conclude that only part of the variable phenotype of heterozygous FH patients is explained by different LDL-receptor defects and that other factors determine the severity of their hypercholesterolaemia and the onset of coronary disease.

An improved synthesis of a water-soluble derivative of dipyrido[3,2-a:2',3'-c]phenazine (dppz) is reported. The structures of both dppz and the cation ethylene-bipyridyldiylium-phenazine dinitrate [[1][(PF(6))(2)]] have been obtained via X-ray crystallography. Metal complex derivatives of dppz are very well studied. However, using the water soluble [1][(NO(3))(2)], the nature of the interaction of a simple dppz unit with duplex DNA has been investigated for the first time. In both organic solvents and water, 1 displays unstructured luminescence, assigned to an intramolecular charge transfer. The emission is quenched on binding to natural and synthetic duplex DNA, including poly(dA).poly(dT). A variety of techniques reveal that the cation binds to DNA with an affinity comparable to those of many metal dppz complexes, via an intercalative binding mode.

The fluorescence behaviour of thin films of poly( N-vinyl carbazole), PNVCz, and a series of N-vinyl carbazole/methyl acrylate, NVCz/MA, copolymers has been investigated using both steady-state and time-resolved emission techniques. The fluorescence of PNVCz at 298 K is dominated by emission from two excimeric traps. Trap I has the conventional ‘sandwich’ structure formed from two fully overlapped aromatic rings. The other (trap II) is a species involving two partially overlapped carbazole substituents. The fluorescences of the NVCz/MA copolymers contain contributions from unassociated or monomeric carbazoyl excited states which increase in prominence as the aromatic content of the system is reduced. The influence of intermolecular interactions in creating excimer traps is apparent: even at a carbazole content of 8.3 mol%, excimer emission is evident. In PNVCz and copolymers of higher aromatic contents, the microtacticity of the macromolecule exerts a dominant influence upon the photophysical behaviour of the bulk polymer despite the moderating effects of intermolecular interactions between chromophores. As the temperature of the system is reduced, the contribution from trap II to the overall fluorescence from the polymer films increases relative to that made by emission from trap I. At 77 K, the fluorescence of PNVCz contains a significant contribution from trap II emission. At 298 K, fluorescence from the conventional excimer, trap I, dominates the steady-state emission spectrum. On the basis of observations upon time-resolved fluorescence data, it is proposed that restrictions to the reorientation of carbazole substituents which occur at low temperature serve to inhibit the conversion of a proportion of the trap II sites into fully overlapped excimers, thereby reducing depletion of the trap II population. Implicit to this explanation of the photophysical characteristics of PNVCz and the higher content NVCz/MA copolymers, is the belief that the high concentration of excimer-forming trap sites mitigates against significant energy migration between carbazole substituents which might otherwise populate the excimer traps. These observations are of importance to considerations of the photoconductivity displayed by polymers derived from NVCz.

Steady-state and time-resolved fluorescence techniques have been used to study the photophysical behaviors of poly(N-vinyl carbazole), PNVCz and a series of N-vinyl carbazole-methyl acrylate (NVCz-co-MA) copolymers in dilute solution as a function of both NVCz composition and temperature. A kinetic scheme, intended to describe intramolecular excimer formation across the entire NVCz composition range, is proposed. In low aromatic content copolymers, two monomer species (unquenched and quenched monomer) and two excimer species (the sandwich-like excimer and a higher energy excimer) exist. The contribution from monomer emission to the overall fluorescence decreases with increasing NVCz content through increased excimer formation: this is likely to be consequent upon (1) an increase in the number of excimer forming sites, and (2) increasing efficiency of energy transfer from the excited monomers to the excimer forming sites. In the homopolymer, PNVCz, the only emission that can be observed on a nanosecond timescale is excimeric. This fluorescence appears to originate from three excimer species (the sandwich-like excimer, and two higher energy forms). For the homopolymer, the current observations are consistent with the model proposed by Vandendriessche and De Schryver [Polym. Photochem. 7, 153 (1986)]. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 963–978, 1997

Time-resolved fluorescence anisotropy measurements have been performed upon an acenaphthylene-labelled (0.5 mol%) sample of poly( N -isopropylacrylamide), PNIPAM, in dilute solutions in both methanol and water as solvents. In methanol, segmental relaxation of PNIPAM follows an Arrhenius dependence upon temperature over the range investigated (279–323K) characterized by an ‘activation energy’ of 13.4(±0.5) kJ mol −1 . This is only slightly greater (by ca 2.4 kJ mol −1 ) than that of solvent flow and it is likely that specific dipolar interactions between the PNIPAM and the methanol determine the macromolecular dynamics in this solvent. In aqueous solution, the segmental mobility of PNIPAM exhibits a dramatic thermoreversible discontinuity at ca 32°C. This change in conformational behaviour occurs at the polymer's lower critical solution temperature in aqueous media. This observation, supports the proposition (Winnik, F. M. Polymer 1990, 31, 2125) that the thermally-induced separation in this system occurs by a ‘dual mode’ mechanism wherein intermolecular aggregation is preceded by intramolecular conformational shrinkage of the polymer coils.