Triplet behavior in weakly coupled chromophors in covalent pyridyl porphyrin-polymer systems

The photophysical properties of the 5-(4-pyridyl)-10,15,20-tri(4-methyloxyphenyl)porphyrins covalently linked to polyethylene glycol – PEG of different molecular weights (35000, 20000 and 8000) dissolved in dimethylsulfoxide were studied. The singlet and triplet states of the porphyrin species behavior were discussed in terms of fluorescence and thermal relaxation processes. The absorption, fluorescence and photothermal experiments showed that in the porphyrins linked to the PEG systems in dimethylsulfoxide the dye moieties occur in weakly interacting dimers. The triplet state enhancement in the 5-(4-pyridyl)-10,15,20-tri(4-methyloxyphenyl)porphyrins covalently linked to PEG was discussed.It was shown that even that the weak interaction of the porphyrin species in the covalent systems with PEG is not detectable by the absorption and only slightly by fluorescence, it is possible to be performed by the complementary spectroscopic methods like photoacoustics and photothermal time resolved spectroscopy.     

Vibrations on Al surfaces covered by sodium

In this paper we present the results of a comparative study of vibrational and structural properties of the ordered and c(2 × 2) phases formed by Na adatoms at room temperature on the Al(1 1 1) and Al(1 0 0) surfaces, respectively. The surface relaxation, surface phonon dispersion, and polarization of vibrational modes are calculated using the embedded-atom method. Our calculated structural parameters are in agreement with experimental and ab initio results. The obtained vibrational frequencies compare fairly well with available experimental data.     

Analytical Problems in Separation of Selenomethionine and Its Oxidative Product in HILIC HPLC

Selenomethionine (SeMet) is one of the main selenium forms in foods and supplements. Determining its presence in natural food samples creates difficulties due to possible oxidation processes. The objective of this study was to evaluate the possible degradation of SeMet in water extracts of green teas, one of the most consumed beverages worldwide. Such a medium has not been investigated at this time. The HILIC-HPLC MS/MS method with different stationary phases was used to achieve the satisfactory separation of SeMet and selenomethionine oxide (SeMetO). The addition of dithiothreitol and β-mercaptoethanol, recommended to ensure that SeMet is kept in the reduced form, was also evaluated. The best separation was achieved using the zwitterionic HILIC stationary phase coupled to mass spectrometry and MeOH with water (85/15, v/v) as the eluent. Extraction was done with hot water with the addition of β-mercaptoethanol. The infusions prepared from Lung-Ching teas (from the Zhejiang Province in China) contained the highest concentration of selenium in a typical cup of tea (12.5–17.3 µg L⁻¹). For other tested teas it decreased in the following order: Yunnan > Dilmah > Lipton. For Lung-Ching teas, the sum of concentrations of SeMet and SeMetO corresponded to about 46–63% of the total selenium in their extracts.     

Effects of Insecticides and Microbiological Contaminants on Apis mellifera Health

Over the past two decades, there has been an alarming decline in the number of honey bee colonies. This phenomenon is called Colony Collapse Disorder (CCD). Bee products play a significant role in human life and have a huge impact on agriculture, therefore bees are an economically important species. Honey has found its healing application in various sectors of human life, as well as other bee products such as royal jelly, propolis, and bee pollen. There are many putative factors of CCD, such as air pollution, GMO, viruses, or predators (such as wasps and hornets). It is, however, believed that pesticides and microorganisms play a huge role in the mass extinction of bee colonies. Insecticides are chemicals that are dangerous to both humans and the environment. They can cause enormous damage to bees’ nervous system and permanently weaken their immune system, making them vulnerable to other factors. Some of the insecticides that negatively affect bees are, for example, neonicotinoids, coumaphos, and chlorpyrifos. Microorganisms can cause various diseases in bees, weakening the health of the colony and often resulting in its extinction. Infection with microorganisms may result in the need to dispose of the entire hive to prevent the spread of pathogens to other hives. Many aspects of the impact of pesticides and microorganisms on bees are still unclear. The need to deepen knowledge in this matter is crucial, bearing in mind how important these animals are for human life.     

Spectroscopic Studies of Quinobenzothiazine Derivative in Terms of the In Vitro Interaction with Selected Human Plasma Proteins. Part 1

Plasma proteins play a fundamental role in living organisms. They participate in the transport of endogenous and exogenous substances, especially drugs. 5-alkyl-12(H)-quino[3,4-b][1,4]benzothiazinium salts, have been synthesized as potential anticancer substances used for cancer treatment. Most anticancer substances generate a toxic effect on the human body. In order to check the toxicity and therapeutic dosage of these chemicals, the study of ligand binding to plasma proteins is very relevant. The present work presents the first comparative analysis of the binding of one of the 5-alkyl-12(H)-quino[3,4-b][1,4]benzothiazinium derivatives (Salt1) with human serum albumin (HSA), α-1-acid glycoprotein (AGP) and human gamma globulin (HGG), assessed using fluorescence, UV-Vis and CD spectroscopy. In order to mimic in vivo ligand–protein binding, control normal serum (CNS) was used. Based on the obtained data, the Salt1 binding sites in the tertiary structure of all plasma proteins and control normal serum were identified. Both the association constants (K_a) and the number of binding site classes (n) were calculated using the Klotz method. The strongest complex formed was Salt1–AGP_complex (K_a = 7.35·10⁴ and 7.86·10⁴ mol·L⁻¹ at excitation wavelengths λ_ex of 275 and 295 nm, respectively). Lower values were obtained for Salt1–HSA_complex (K_a = 2.45·10⁴ and 2.71·10⁴ mol·L⁻¹) and Salt1–HGG_complex (K_a = 1.41·10⁴ and 1.33·10⁴ mol·L⁻¹) at excitation wavelengths λ_ex of 275 and 295 nm, respectively, which is a positive phenomenon and contributes to the prolonged action of the drug. Salt1 probably binds to the HSA molecule in Sudlow sites I and II; for the remaining plasma proteins studied, only one binding site was observed. Moreover, using circular dichroism (CD), fluorescence and UV-Vis spectroscopy, no effect on the secondary and tertiary structures of proteins in the absence or presence of Salt1 has been demonstrated. Despite the fact that the conducted studies are basic, from the scientific point of view they are novel and encourage further in vitro and in vivo investigations. As a next part of the study (Part 2), the second new synthetized quinobenzothiazine derivative (Salt2) will be analyzed and published.     

Vibrational properties of small cobalt clusters on the Cu(111) surface

Physics of the Solid State - Vibrational properties of small cobalt clusters (dimer and trimer) adsorbed on the Cu(111) surface are studied using interatomic interaction potentials obtained in a...     

Multifractal estimates of monofractality in RR-heart series in power spectrum ranges

Two popular estimators of multifractal properties: the Wavelet Transform Modulus Maxima method and Multifractal Detrended Fluctuation Analysis are applied to investigate signals consisting of normal RR-series in 39 healthy subjects and 90 patients suffering from systolic dysfunction of the left ventricle. However, differently from standards for multifractal analysis the scaling is performed separately in intervals corresponding to standard power spectral bands: low (LF), very low (VLF) and ultra low frequencies (ULF). Tests on fractional Brownian motions (fBm) are done to quantify properties of the estimators as detectors of monofractality in LF, VLF and ULF bands. Arguments are given that multifractal analysis of RR-series performed in these bands has a physiological meaning. The increased activation of the sympathetic nervous system caused by heart disease is detected evidently only by analysis in LF. The transition in multifractal characteristics between diurnal and nocturnal activity takes place when the analysis moves from LF and VLF to ULF. Only in ULF, the diurnal heart rate variability can be approximated by fBm with a self-similarity index of H=0.20.     

Fluorine-Containing Furan-3(2Н)-Ones in Reactions with Binucleophiles: CF3vs C2F5

Chemistry of Heterocyclic Compounds - Five- and six-membered fluorine-containing azaheterocycles were synthesized based on available furan-3(2H)-ones, and the influence of the nature of the...     

SEM and TEM analysis of composite of ZrO2-Ti system

3Y-ZrO₂-Ti composites obtained by slip casting method were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, the Vickers hardness was measured. The experiments show the complex microstructure of composites. The tetragonal zirconium dioxide (t-ZrO₂) and monoclinic zirconium dioxide (m-ZrO₂) as a composite matrix were detected at XRD analysis. SEM observations revealed that Ti -rich phase are uniform distributed in composites. Moreover, the large and very fine precipitations were found. The very fine Ti rich precipitations were located at ZrO₂ grain boundaries as well as in the triple-points. TEM experiments confirmed that in the sintered composites 3Y-ZrO₂ – 10%Ti the uniaxial ZrO₂ grains (100–600 nm), fine monoclinic martensitic plates and fine round monoclinic particles (20–40 nm) of ZrTiO₂ phase were exist. The complex microstructures of 3Y-ZrO₂-Ti composites have a high hardness as a result of existing fine ZrTiO₂ and other Ti oxides precipitations.