Role of water content in dielectric properties and delayed luminescence of bovine Achilles' tendon

In order to investigate the role of water network in collagen structure, measurement of dielectric permittivity was performed on bovine Achilles' tendon as a function of water content. The data show a sudden decrease of the permittivity at each measured frequency value when the tendon humidity decreases. A similar behaviour is shown by the total number of photons emitted in delayed luminescence (DL) experiments. The comparison of the two results is in agreement with the hypothesis that DL is connected to the excitation and subsequent decay of collective electronic states, whose properties depend on the organized structure of the system.     

Formation of a new hybrid complex via coordination interaction between 5,10,15-tritolyl-20-(4- and 3-pyridyl)porphyrin or 5,10,15-triphenyl-20-(4-pyridyl)porphyrin and the α-[MSiW11O39] Keggin-type polyoxometalate (M = Co and Ni)

New complexes based on a coordination interaction between a pyridyl-porphyrin (namely 5,10,15-tritolyl-20-(4-pyridyl)porphyrin, 5,10,15-tritolyl-20-(3-pyridyl)porphyrin or 5,10,15-triphenyl-20-(4-pyridyl)porphyrin) and a Keggin-type polyoxometalate (α-[MSiW₁₁O₃₉]⁶⁻, M = Co²⁺ or Ni²⁺) are formed in solution. The formation of these complexes is clearly evidenced by steady-state and time-resolved luminescence measurements. A strong quenching of the porphyrin fluorescence, accompanied by an important shortening of the fluorescence lifetime, is observed upon addition of the POM and formation of the complexes. Using a variant of the Job’s method from the luminescence spectra, the association constants of the complexes have been estimated to be around 10⁶ L mol⁻¹. Paramagnetic ¹H NMR experiments confirm the formation of the complexes. Indeed, in addition to broadenings of the signals, the coordination binding of the POM to the porphyrin induces large high-frequency shifts for the protons of the pyridyl group coordinated to the paramagnetic metal, and low-frequency shifts for all the other resonances.     

Characterization of hydrogen peroxide production by Duox in bronchial epithelial cells exposed to Pseudomonas aeruginosa

Hydrogen peroxide production by the NADPH oxidase Duox1 occurs during activation of respiratory epithelial cells stimulated by purified bacterial ligands, such as lipopolysaccharide. Here, we characterize Duox activation using intact bacterial cells of several airway pathogens. We found that only Pseudomonas aeruginosa, not Burkholderia cepacia or Staphylococcus aureus, triggers H₂O₂ production in bronchial epithelial cells in a calcium-dependent but predominantly ATP-independent manner. Moreover, by comparing mutant Pseudomonas strains, we identify several virulence factors that participate in Duox activation, including the type-three secretion system. These data provide insight on Duox activation by mechanisms unique to P. aeruginosa.     

On the determination of empirical absolute chiral structure: chiroptical spectrum correlations for D3 lanthanide (III) complexes

Circularly polarized luminescence (CPL) from selected transitions of Eu(III) in resolved single crystals of Na3[Eu(ODA)3].2NaClO4.6H2O are compared to CPL results obtained from solutions containing perturbed racemic mixtures of Eu(2,6-pyridine-dicarboxylate)3 (3-) and enantiomerically pure d-f helicate LambdaLambda-(-)EuCr(L8)3] in order to determine an empirical relationship between helicity and CPL spectra. Comparison of the CPL results, even for the magnetic dipole allowed transitions of Eu(III) where one measures large chiral discrimination, shows that the signs and magnitudes do not correlate with the overall helicity of the Eu(III) site. It is concluded that the symmetry of the Eu(III) site in LambdaLambda-(-)EuCr(L8)3 is not close enough to D3 to allow for the confirmation of the presumed spectra:structure correlation.     

Delayed luminescence: a novel technique to obtain new insights into water structure

Fully understanding the structure of water is a crucial point in biophysics because this liquid is essential in the operation of the engines of life. Many of its amazing anomalies seem to be tailored to support biological processes and, during about a century, several models have been developed to describe the water structuring. In particular, a theory assumes that water is a mixture of domains constituted by two distinct and inter-converting structural species, the low-density water (LDW) and the high-density water (HDW). According to this theory, by using some particular solutes or changing the water temperature, it should be possible to modify the equilibrium between the two species, changing in this way the water behavior in specific biological processes, as in governing the shape and stability of the structures of proteins. In this work, we assess the possibility of obtaining information on the structures induced in water by specific salts or by temperature by measuring the delayed luminescence (DL) of some salt solutions and of water in the super-cooled regime. Previous works have demonstrated that the delayed luminescence of a system is correlated with its dynamic ordered structures. The results show significant DL signals only when the formation of LDW domains is expected. The measurement reveals a similar activation energy for the domains both in aqueous salt solutions and super-cooled water. It is worth noting that the time trend of DL signals suggests the existence of structures unusually long-lasting in time, up to the microsecond range.     

Thermal luminescence spectra of polyamides and their Maillard reaction with reducing sugars

Thermal luminescence (TL) spectra of polyamides were measured with a Fourier‐transform chemiluminescence spectrometer to elucidate the emission mechanism. A TL band of ε‐polylysine with a peak at 542 nm observed at 403 K was assigned to the emission due to the interaction of the –CO–NH– group with oxygen molecules by comparison with nylon‐6, polyglycine, and polyalanine. When the sample was kept at 453 K, the intensity of the TL band decreased and the wavelength of the peak shifted to 602 nm, which was assigned to the emission due to the interaction of the NH₂ group on the side chain with oxygen molecules by comparison with monomeric lysine. A weak emission with a peak at 668 nm was assigned to the advanced glycosylation end products (AGEs) yielded by the Maillard reaction with a catalytic amount of water. To understand this reaction and to examine the TL emission of AGEs, we measured TL spectra of mixtures of polylysine and reducing sugars such as glucose, maltose, lactose, and dextrin. The minimum temperature for TL emission, wavelength of the peak and the relative intensities of the TL emission were found to depend on the size of the sugars. Copyright © 2011 John Wiley & Sons, Ltd.     

Luminescence in Li2Sr2Al2PO4F9:Dy3+ ‐ a novel nanophosphor

Earlier research has revealed numerous advantages of the wet chemical method in reaction acceleration, yield improvement, enhanced photoluminescence properties and the evolution of new material phases. In the present study the novel nanophosphor Li₂Sr₂Al₂PO₄F₉:Dy³⁺ was synthesized by a one‐step wet chemical method. Formation of single‐phase compounds was confirmed by X‐ray diffraction (XRD) and characterized by photoluminescence (PL) and transmission electron microscopy (TEM) techniques. The average diameter of the particles was calculated from the TEM image as ca. 20 nm. The synthesized nanophosphor exhibited intense blue and yellow emissions at 482 and 575 nm, respectively, owing to the Dy³⁺ ion, by Hg‐free excitation at 387 nm, i.e. solid‐state lighting excitation. The results obtained showed that phosphors have the potential for applications in the lamp industry. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and properties of a new red luminescence europium complex containing a 2‐(benzimidazol‐2‐yl)‐8‐octyloxyquinoline as the second ligand

A new Eu(III) complex, Eu(III)(DBM)₃BIOQ, has been synthesized with dibenzoylmethane (DBM) as the first ligand and 2‐(benzimidazol‐2‐yl)‐8‐octyloxyquinoline (BIOQ) as the second ligand. The stability of the complex was analysed by DSC–TG. The results show that the Eu(III) complex has a relatively high thermal stability with a melting point of 235 °C and a decomposition temperature (onset) of 252 °C. The fluorescence properties of the compound were also investigated. The fluorescence results reveal that the as‐prepared complex shows the characteristic maximum emission spectra of Eu(III) at 611 nm (λ_ex = 350 nm). In addition, the photoluminescence spectrum of the complex in the solid state exhibits a single and symmetrical emission band at 611 nm, with a full width at half‐maximum of 4.7 nm, showing high colour purity. This finding indicates the possibility for the development of brighter red luminescent materials. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of isoflurane on measurements of delayed lumininescence in Acetabularia acetabulum.

The volatile halogenated methyl ethyl ether, isoflurane, used as an anaesthetic, inhibits actin-based dynamics directly or indirectly in animal cells. In plant cells, most intracellular movements are related to actin pathways. We have used isoflurane in a unicellular alga, Acetabularia acetabulum, to test the dynamics of choloroplast organization. By measuring the delayed luminescence, we found that isoflurane worked efficiently in the unicellular organism and showed dose- and time-course-dependent actin-inhibition patterns. When A. acetabulum was treated with saturated solutions of isoflurane in artificial seawater (defined as 100% isoflurane) for 3 or 6 min, the delayed luminescence (DL) was decreased and was never recovered. In contrast, if treated with 75% diluted isoflurane, the DL was firstly inhibited and then recovered several hours later, and if treated with 50% diluted isoflurane, the change of DL was small. Our work proved that isoflurane can affect actin-related pathways in both animals and plants.     

Delayed luminescence of Prorocentrum minimum under controlled conditions

Delayed luminescence (DL), also termed delayed fluorescence or delayed light emission, is the phenomenon of long-lived light emission by plants and cyanobacteria after being illuminated with light and put into darkness. Culture growth of three Prorocentrum minimum strains was studied with DL measurements. DL decay kinetics was measured from 1–60 s after a pulse of white light. The strains used were from the Adriatic Sea (PmK), from Chesapeake Bay, USA (D5), and from the Baltic Sea (BAL), cultured at salinity of 32, 16, and 8 (practical salinity scale), respectively. The strains differed in cell size and chlorophyll a content (PmK > D5 > BAL), as well as in DL parameters. The DL results were compared to standard measurements of culture density and carbon content (calculated from biovolumes). DL decay curves had a specific peak, which changed with culture growth and showed more similarities between the strains PmK and D5. The DL intensity increased with cell density and carbon content in a two-stage process, corresponding to the lag and exponential phases of growth. DL intensity was best correlated with carbon content irrespective of strain and is proposed as an estimate of biomass and for differentiating between lag and exponential phases of growth.