The Temperature Dependence of Protoporphyrin IX Production in Cells and Tissues

The formation of protoporphyrin IX (PpIX) in human skin during topical application of 5-aminolevulinic acid (ALA) was found to be strongly temperature dependent, with an activation energy of about 17 kcal/mol. This temperature dependence is mainly related to porphyrin production and not to ALA penetration into the skin. The penetration of ALA into mouse and human skin was almost temperature independent. The activation energy of PpIX production in mouse skin was practically identical with that in human skin. The activation energy of ALA uptake by cells in vitro was about 10 kcal/mol and that for PpIX production was about 13 kcal/mol. The latter activation energy was within the error limits similar to that for the activity of the enzyme porphobilinogen deaminase, suggesting that this enzyme might represent a rate-limiting step for PpIX production in living tissue.     

The Vitamin D Status Among Tibetans

UVB from the sun and intake from food are the only human sources of vitamin D. Tibet is a unique region for comparisons of these sources: (1) it lies at a low latitude and at a high altitude and has very large annual fluences of UVB; (2) the traditional Tibetan food is poor in vitamin D. Blood samples were taken from 63 persons of different age, with different occupations and staying at different places. UVB doses at these places were measured. The samples were analyzed by a standard radioimmune assay for determination of the serum concentration of 25 hydroxyvitamin D (25(OH)D). The main finding was that among nomads, there seems to be severe vitamin D deficiency (serum levels of 25(OH)D < 30 n m ). We tentatively propose that the low level of 25(OH)D of nomads is related to their clothing and sun exposure habits. For persons of other occupations (students, teachers and farmers) the levels are higher, although a significant fraction of these persons also have lower levels than 75 n m , by many regarded as a limit for insufficiency related to a number of negative health conditions. The annual dose of vitamin D-generating UVB is about five times larger in Lhasa than in Oslo. Despite this, the average vitamin D status seems to be similar, except in the case of nomads. This phenomenon is certainly related to food habits. In conclusion, the 25(OH)D status among nomads in Tibet appears to be alarmingly low. However, for people of other occupations the status is more normal.     

Diamino acid derivatives of PpIX as potential photosensitizers for photodynamic therapy of squamous cell carcinoma and prostate cancer: In vitro studies

Photodynamic therapy (PDT) is an alternative treatment modality involving light activated drugs, called photosensitizers (PSs), to treat cancer and non-cancerous conditions. The search for new compounds which might become effective PSs is the major direction for PDT development. In the present work we have studied the dark toxicity, intracellular localization and photodynamic properties of four potential, water soluble, second generation PSs – PP(Arg)₂, PP(Ser)₂Arg₂, PP(Ala)₂Arg₂, PP(Phe)₂Arg₂, all diamino acid derivatives of protoporphyrin IX. Human prostate cancer (DU-145) and squamous carcinoma (A431) cells were used as experimental model.Among investigated compounds PP(Ser)₂Arg₂ exhibited the lowest dark toxicity and the highest PDT effectiveness towards both cell lines. Fluorescence microscopy revealed the time-dependent changes in intracellular localization of the PS which were related to the phototoxicity. The results show that PP(Ser)₂Arg₂ may be a potential PS for PDT.     

Artificial transfer hydrogenases based on the biotin-(strept)avidin technology: fine tuning the selectivity by saturation mutagenesis of the host protein

Incorporation of biotinylated racemic three-legged d6-piano stool complexes in streptavidin yields enantioselective transfer hydrogenation artificial metalloenzymes for the reduction of ketones. Having identified the most promising organometallic catalyst precursors in the presence of wild-type streptavidin, fine-tuning of the selectivity is achieved by saturation mutagenesis at position S112. This choice for the genetic optimization site is suggested by docking studies which reveal that this position lies closest to the biotinylated metal upon incorporation into streptavidin. For aromatic ketones, the reaction proceeds smoothly to afford the corresponding enantioenriched alcohols in up to 97% ee (R) or 70% (S). On the basis of these results, we suggest that the enantioselection is mostly dictated by CH/pi interactions between the substrate and the eta6-bound arene. However, these enantiodiscriminating interactions can be outweighed in the presence of cationic residues at position S112 to afford the opposite enantiomers of the product.     

The influence of temperature on photodynamic cell killing in vitro with 5-aminolevulinic acid

Cell survival was investigated after exposing cells in vitro to different temperatures before or after photodynamic therapy with 5-aminolevulinic acid. The photodynamic process was found to be temperature dependent. Cells exposed for 1h to 41 degrees C before light exposure or to 7 degrees C after light exposure showed decreased survival. Furthermore, the photobleaching rate of protoporphyrin IX in the cells was found to increase with increasing temperature during the light exposure. Thus, the photodynamic effect with 5-aminolevulinic acid may be enhanced by heating the tumour area before, and by cooling it immediately after the treatment.     

Cell refractive index tomography by digital holographic microscopy

For what we believe to be the first time, digital holographic microscopy is applied to perform optical diffraction tomography of a pollen grain. Transmission phase images with nanometric axial accuracy are numerically reconstructed from holograms acquired for different orientations of the rotating sample; then the three-dimensional refractive index spatial distribution is computed by inverse radon transform. A precision of 0.01 for the refractive index estimation and a spatial resolution in the micrometer range are demonstrated.     

Synthesis,characterization, and cytotoxicity evaluation of high-magnetization multifunctional nanoclusters

The paper presents the synthesis, characterization, and in vitro cytotoxicity tests of Fe₃O₄ magnetic nanoclusters coated with ethylenediaminetetraacetic acid disodium salt (EDTA). Electron microscopy analysis (SEM) evidences that magnetite nanoparticles are closely packed into the clusters stabilized with EDTA with well-defined near spherical shapes and sizes in the range 100–200 nm. From XRD measurements, we determined the mean size of the crystallites inside the magnetic cluster about 36 nm. The saturation magnetization determined for the magnetic clusters stabilized with EDTA has high value, about 81.7 emu/g at 300 K. X-ray photoelectron spectroscopy has been used to determine both the elemental and chemical structure of the magnetic cluster surface. In vitro studies have shown that the magnetic clusters at low doses did not induce toxicity on human umbilical vein endothelial cells or lesions of the cell membrane. In contrast, at high doses, the magnetic clusters increased the lipid peroxidation and reduced the leakage of a cytoplasmic enzyme, lactate dehydrogenase (LDH), in parallel with increasing the antioxidant defense.

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Graphical abstract SEM images of EDTA-coated magnetic clusters (MCs) and the HUVEC viability at different MC doses

     

A selenium analogue of firefly d-luciferin with red-shifted bioluminescence emission

A selenium analogue of amino-D-luciferin, aminoseleno-D-luciferin, is synthesized and shown to be a competent substrate for the firefly luciferase enzyme. It has a red-shifted bioluminescence emission maximum at 600?nm and is suitable for bioluminescence imaging studies in living subjects.     

Linearization of the MS response function: case study for metformin assay in plasma samples for bioequivalence purposes

Calibration data of LC-MS/MS rarely fit the pure least square regression model, especially for large concentration intervals. The response function of the MS instrument is corrected by weighted regression models or logarithms. The choice of a response linearization method is based on results produced through back-interpolation of experimental data and/or evaluation of correlation coefficients. Two bioequivalence studies carried out for pharmaceutical formulations containing metformin gave us the opportunity to appreciate the impact of the MS response linearization method (logarithm and 1/x weighted linear regression) on method quality characteristics. The sample preparation was based on protein precipitation with acetonitrile. Chromatographic separation was achieved on a Zorbax CN column (mobile phase acetonitrile and aqueous 10 m m ammonium acetate solution, pH 3.5). Tandem MS detection was performed on a triple quadrupole spectrometer equipped with an electrospray source, operated under positive-ion mode. The method was validated and used for evaluation of the bioequivalence of formulations containing 500 and 1000 mg metformin. The 500 mg metformin study used logarithms for linearization of the detector response, while the 1000 mg metformin study was based on 1/x linear weighted regression. Data resulting from validations and studies completion were compared with evaluate the impact of the response linearization on the method quality characteristics.     

The influence of precursor’s composition and concentration on cadmium doped TiO<Subscript>2</Subscript> film

The purpose of this article is to emphasize that new nanomaterials offer a number of attractive alternatives for solar energy use in wastewater photocatalysis. The wastewater from the textile industry contains dyes and heavy metals. Thin films of cadmium doped TiO₂ (Cd-TiO₂) were coated by a doctor blade using TiO₂ Degussa P25 and cadmium precursor (cadmium nitrate). The photocatalytic efficiency of cadmium doped TiO₂ is strongly influenced by crystal structure, particle size, particle morphology, porosity and doping. The pore size distribution and the roughness analysis have been studied by the atomic force microscopy (AFM) of the thin films. The photocatalytic activity of the samples was tested in Methyl orange and Methylene blue photodegradation. Cadmium doped TiO₂ catalyst does not significantly decrease the efficiency of photodegradation processes, and, in some situations, improves dye photodegradation.