Search results

1

Energy up-conversion in dilute polyfluorene solutions

100%

Kuehne A., Mackintosh A., Armstrong D., Pethrick R.

Open Chemistry

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2007

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vol. 5

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issue 4

923-930

EN

Poly(9,9-dioctylfluorene) (PFO) shows highly efficient blue emission with photo excitation occurring between 340–400 nm. Here we show that PFO can in dilute solution emit at a wavelength well below that at which it is being exited. This, we propose is related to an energy transfer from conjugated parts of the polymer chain into more localised states which then emit at a lower wavelength. These localised states can be considered as defects in the conjugation of the polymer or as chain ends. These may produce quasi monomer or quasi dimer species within the chain, which will have a HOMO-LUMO gap of higher energy than the conjugated polymer. These then fluoresce at the lower wavelength; essentially causing, by energy transfer, a process of energy up-conversion. [...]

2

Quantification of 5-methyl-2'-deoxycytidine in the DNA

100%

Giel-Pietraszuk M., Insińska-Rak M., Golczak A., Sikorski M., Barciszewska M., Barciszewski J.

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2015

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vol. 62

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issue 2

281-286

EN

Methylation at position 5 of cytosine (Cyt) at the CpG sequences leading to formation of 5-methyl-cytosine (m5Cyt) is an important element of epigenetic regulation of gene expression. Modification of the normal methylation pattern, unique to each organism, leads to the development of pathological processes and diseases, including cancer. Therefore, quantification of the DNA methylation and analysis of changes in the methylation pattern is very important from a practical point of view and can be used for diagnostic purposes, as well as monitoring of the treatment progress. In this paper we present a new method for quantification of 5-methyl-2'deoxycytidine (m5C) in the DNA. The technique is based on conversion of m5C into fluorescent 3,N4-etheno-5-methyl-2'deoxycytidine (εm5C) and its identification by reversed-phase high-performance liquid chromatography (RP-HPLC). The assay was used to evaluate m5C concentration in DNA of calf thymus and peripheral blood of cows bred under different conditions. This approach can be applied for measuring of 5-methylcytosine in cellular DNA from different cells and tissues.

3

Spectral properties of phthalocyanines incorporated into resting and stimulated human peripheral blood cells.

100%

Waszkowiak A., Frąckowiak D., Wiktorowicz K., Miyake J.

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2002

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vol. 49

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issue 3

633-641

EN

Human peripheral blood cells stimulated by phytohemagglutinin (which serve as a model of cancerous cells) and resting cells were incubated in dimethyl sulfoxide solutions of various phthalocyanines. In order to diminish the influence of atmospheric oxygen the cells were embedded in a polymer (polyvinyl alcohol) film. Fluorescence spectra of the samples were measured over two regions of excitation wavelengths: at 405 nm (predominant absorption of the cell material) and in the regions of strong absorption of phthalocyanines (at about 605 nm and 337 nm). The intrinsic emission of cell material became changed as a result both of cells' stimulation and of incubation of cells in dye solution. In most cases the stimulated cells when stained by dye exhibited higher long wavelength fluorescence intensity than resting cells. This suggests higher efficiency of dye incorporation into cancerous cells than into healthy cells. The absorption spectra of samples were also measured. The spectra of various phthalocyanines in incubation solvent, in polymer and in the cells embedded in polymer, were compared. The comparison of properties of the cells stimulated for different time periods enabled to establish the conditions of stimulation creating a population of cells incorporating a large number of sensitizing molecules.

4

Fluorescence spectroscopy of semiconductor CdTe nanocrystals: preparation effect on photostability

100%

Bujak Ł., Olejnik M., Litvin R., Piątkowski D., Kotov N., Mackowski S.

Open Physics

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2011

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vol. 9

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issue 2

287-292

EN

We report on continuous-wave and time-resolved fluorescence spectroscopy studies of CdTe water-soluble nanocrystals at room temperature. For nanocrystals spread directly on the substrate we observe large variation both in fluorescence maximum energy and fluorescence lifetime. We attribute this to the influence of the surface of the nanocrystals on the stability of excitations in the nanocrystals. As the fluorescence lifetime of the nanocrystals is monitored, we find it increases with time from 6 to 18 ns and then saturates. Placing the nanocrystals in a polymer matrix remarkably improves the photostability and all the above-mentioned effects are diminished. Upon mixing the nanocrystals with gold spherical nanoparticles we observe a decrease of the fluorescence intensity due to efficient energy transfer to the nanoparticles.

5

Comparison of Methods in Studies of Cell Death Mechanisms

100%

Borkowska A., Nowakowski M., Miszczyk J., Lipiec E., Wiltowska-Zuber J., Rawojć K., Kwiatek W.

Acta Physica Polonica A

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2018

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vol. 133

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issue 2

263-266

EN

While studying the influence of ionizing radiation or certain chemical agents on cells, it is crucial to not only determine cytotoxicity, but also to follow cell death mechanisms. There are different methods to screen processes of cell death and still very important question remains unanswered about differences in results that could be caused by various experimental steps in procedures. Based on literature review two protocols of cell death determination were compared. First protocol regarded collecting cells floating in medium before trypsinization and following centrifugation of them. In the second protocol floating cells were discarded and attached ones were stained and fixed. In all experiments three different untreated cell lines (A172, DU145 as cancer cell lines and in comparison, fibroblasts (FB CCL 110), as a non- cancerous cell line) were used to test applied protocols. Cells were cultured and death processes were examined at different time points up to 120 h. Compared protocols showed statistically significant differences, especially in terms of necrosis, which was higher when included floating cells from culture medium and then centrifuging them. Therefore, presented results show importance of choosing a valid experimental procedure in case of evaluating cells viability and types of cell death pathways quantitatively.

6

Structural factors influencing the reaction rates of 4-aryloxy-7-nitrobenzofurazans with amino acids

100%

Bem M., Vasilescu M., Caproiu M., Draghici C., Beteringhe A., Constantinescu T., Banciu M., Balaban A.

Open Chemistry

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2004

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vol. 2

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issue 4

672-685

EN

An interesting observation was made when studying the SNAr reaction between several 4-aryloxy-7-nitrobenzofurazans (2) and several amino acids leading to the apparition of detectable fluorescence from the substitution products3. Acidic amino acids reacted very slowly=while basic amino acids react fastest with2 having an unsubstituted phenyl or a 4-formyl-phenyl Ar group. Amongst neutral amino acids, proline reacts fastest at room temperature after 100 min. With2 having a methoxy-subtituted Ar group.

7

Ca2+differently affects hydrophobic properties of guanylyl cyclase-activating proteins (GCAPs) and recoverin.

100%

Gorczyca W. A., Kobiałka M., Kuropatwa M., Kurowska E.

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2003

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vol. 50

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issue 2

367-376

EN

Guanylyl cyclase-activating proteins (GCAPs) and recoverin are retina-specific Ca2+-binding proteins involved in phototransduction. We provide here evidence that in spite of structural similarities GCAPs and recoverin differently change their overall hydrophobic properties in response to Ca2+. Using native bovine GCAP1, GCAP2 and recoverin we show that: i) the Ca2+-dependent binding of recoverin to Phenyl-Sepharose is distinct from such interactions of GCAPs; ii) fluorescence intensity of 1-anilinonaphthalene-8-sulfonate (ANS) is markedly higher at high [Ca2+]gfree (10 μM) than at low [Ca2+]free (10 nM) in the presence of recoverin, while an opposing effect is observed in the presence of GCAPs; iii) fluorescence resonance energy transfer from tryptophane residues to ANS is more efficient at high [Ca2+]free in recoverin and at low [Ca2+]free in GCAP2. Such different changes of hydrophobicity evoked by Ca2+ appear to be the precondition for possible mechanisms by which GCAPs and recoverin control the activities of their target enzymes.

8

Synthesis and Characterization of an Efficient New Liquid Laser Dye Material - Chalcone (DMAPPP)

88%

Elzupir A., Ibnaouf K., Idriss H., Ibrahem M., Prasad S., Alrajhi M., AlSalhi M., Alaamer A.

Acta Physica Polonica A

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2018

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vol. 133

|

issue 1

121-125

EN

This paper comprises the synthesis and characterization of 3-(4-(dimethylamino)phenyl)-1-phenyl-(2E)-propen-1-one (DMAPPP) and its application as a new laser medium. The absorption and fluorescence spectra of DMAPPP under different solvents and concentrations have been investigated. The amplified spontaneous emission performance of DMAPPP under various concentrations, organic solvents and pump pulse energies of Nd:YAG laser (355 nm) was also studied. The amplified spontaneous emission spectra of DMAPPP in solution were compared with a conventional laser dye of coumarin 503, under the same identical conditions. The gain and the fluorescence quantum yield of DMAPPP were determined. The most important features are: (1) DMAPPP has an excellent photochemical stability, (2) the amplified spontaneous emission from the DMAPPP was tuned in the wavelength region between 515 and 548 nm. This could be the first detailed paper on laser properties of DMAPPP.

9

Preliminary studies of phthalocyanine sensitizers incorporated into human leukemia cells from two cell-lines.

88%

Wiktorowicz K., Cofta J., Dudkowiak A., Waszkowiak A., Frąckowiak D.

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vol. 51

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issue 3

703-710

EN

Three phthalocyanine dyes-sensitizers were incorporated into two types of human T leukemia cells from two cell-lines: CCRF and MOLT 4. The efficiency of the dye incorporation into cells and photochemical properties of stained cells were investigated using fluorescence spectroscopy. The dyes exhibited different properties in each of the two cell-lines. Small differences in cell membrane properties have a strong influence on the efficiency of dye incorporation and on the course of photodynamic reaction. It is suggested that, for a given patient, an optimal dye-sensitizer should be established before photodynamic treatment.

10

Insight into the kinetics and the mode of the interaction between smooth muscle calponin and F-actin.

88%

Kołakowski J., Dąbrowska R.

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2002

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vol. 49

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issue 2

471-479

EN

Kinetics of the smooth muscle calponin-F-actin interaction was studied by stopped- flow measurements of light scattering and fluorescence intensity of pyrene-labelled F-actin. The intensity and character of the changes in light scattering, and thus the mode of calponin binding to actin filaments leading to changes in their shape and bundling, depend on the molar ratio of the two proteins. Parallel measurements of pyrene-fluorescence quenching upon calponin binding revealed that intrinsic conformational changes in actin filaments are delayed relative to the binding process and are not markedly influenced by the mode of calponin binding. Bundling of actin filaments by calponin was not correlated with fluorescence changes and thus with alterations in the structure of actin filaments.

11

Application of a carbazole derivative as a spectroscopic fluorescent probe for real time monitoring of cationic photopolymerization

88%

Ortyl J., Galica M., Popielarz R., Bogdał D.

Polish Journal of Chemical Technology

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2014

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vol. 16

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issue 1

75-80

EN

The performance of 1-(9-ethylcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione (1) as a fluorescent probe for the monitoring of cationic photopolymerization processes by Fluorescence Probe Technique (FPT) has been evaluated in comparison with the response of 7-diethylamino-4-methylcoumarin (Coumarin 1) (2). Triethylene glycol divinyl ether and diphenyliodonium hexafluorophosphate were used as an example monomer and a cationic photoinitiator respectively. It has been found that the probe 1 withstands the cationic polymerization conditions and provides correct probe response. 1-(9-ethylcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione shifts its fluorescence spectrum with progress of cationic photopolymerization of the monomer, which enables the monitoring of the polymerization progress using the fluorescence intensity ratio measured at two different wavelengths as the progress indicator. By comparing the behavior of 1 and 2, it has been documented that the fluorescence spectrum of probe 1 shows a spectacular hypsochromic shift (Δλ = 33 nm) upon the monomer polymerization, while the shift of 2 is three times smaller (Δλ = 11 nm). Moreover, the sensitivity of probe 1 is more than 2.5-times higher than that of any other probes suitable for monitoring cationic polymerization processes, reported previously. Therefore, application of the carbazole derivative (1) as a new probe for the monitoring of the crosslinking process of coatings cured by cationic photopolymerization has been proposed.

12

The phenomenon of fluorescence in immunosensors

88%

Kłos-Witkowska A.

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2016

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vol. 63

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issue 2

215-221

EN

The phenomenon of fluorescence in immunosensors is described in this paper. Both structure and characteristics of biosensors and immunosensors are presented. Types of immunosensors and the response of bioreceptor layers to the reaction with analytes as well as measurements of electrochemical, piezoelectric and optical parameters in immunosensors are also presented. In addition, detection techniques used in studies of optical immunosensors based on light-matter interactions (absorbance, reflectance, dispersion, emission) such as: UV/VIS spectroscopy, reflectometric interference spectroscopy (RIfs), surface plasmon resonance (SPR), optical waveguide light-mode spectroscopy (OWLS), fluorescence spectroscopy. The phenomenon of fluorescence in immunosensors and standard configurations of immunoreactions between an antigen and an antibody (direct, competitive, sandwich, displacement) is described. Fluorescence parameters taken into account in analyses and fluorescence detection techniques used in research of immunosensors are presented. Examples of immunosensor applications are given.

13

Simultaneous velocity measurement of phases in a liquid-gas system

88%

Musoski R., Stelmach J.

Chemical and Process Engineering

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2017

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vol. 38

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issue 4

14

Fluorescence decay time distribution analysis of cyclic enkephalin analogues; Influence of solvent and Leu configuration in position 5 on conformation

88%

Malicka J., Ganzynkowicz R., Groth M., Czaplewski C., Karolczak J., Liwo A., Wiczk W.

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2001

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vol. 48

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issue 1

95-102

EN

Lifetime distribution analysis were performed to study the influence of Leu configuration in position 5 on changes of the peptide chain of cyclic analogues of enkephalins containing a fluorescence donor and acceptor in different solvents. The configuration change of Leu5 in all the analogues of enkephalins studied which contain donor-acceptor pairs has no apparent influence on Trp lifetime distributions. In contrast, there is a significant solvent effect on the shape of lifetime distribution.

15

Salivary aldehyde dehydrogenase - temporal and population variability, correlations with drinking and smoking habits and activity towards aldehydes contained in food

75%

Giebułtowicz J., Dziadek M., Wroczyński P., Woźnicka K., Wojno B., Pietrzak M., Wierzchowski J.

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2010

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vol. 57

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issue 3

361-368

EN

Fluorimetric method based on oxidation of the fluorogenic 6-methoxy-2-naphthaldehyde was applied to evaluate temporal and population variability of the specific activity of salivary aldehyde dehydrogenase (ALDH) and the degree of its inactivation in healthy human population. Analyzed was also its dependence on drinking and smoking habits, coffee consumption, and its sensitivity to N-acetylcysteine. Both the specific activity of salivary ALDH and the degree of its inactivation were highly variable during the day, with the highest activities recorded in the morning hours. The activities were also highly variable both intra- and interpersonally, and negatively correlated with age, and this correlation was stronger for the subgroup of volunteers declaring abstinence from alcohol and tobacco. Moderately positive correlations of salivary ALDH specific activity with alcohol consumption and tobacco smoking were also recorded (rs ~0.27; p=0.004 and rs =0.30; p=0.001, respectively). Moderate coffee consumption correlated positively with the inactivation of salivary ALDH, particularly in the subgroup of non-drinking and non-smoking volunteers. It was found that mechanical stimulation of the saliva flow increases the specific activity of salivary ALDH. The specific activity of the salivary ALDH was strongly and positively correlated with that of superoxide dismutase, and somewhat less with salivary peroxidase. The antioxidant-containing drug N-acetylcysteine increased activity of salivary ALDH presumably by preventing its inactivation in the oral cavity. Some food-related aldehydes, mainly cinnamic aldehyde and anisaldehyde, were excellent substrates of the salivary ALDH3A1 enzyme, while alkenals, particularly those with short chain, were characterized by lower affinity towards this enzyme but high catalytic constants. The protective role of salivary ALDH against aldehydes in food and those found in the cigarette smoke is discussed, as well as its participation in diminishing the effects of alcohol- and smoking-related oxidative stress.

16

Thermodynamics of specific protein-RNA interactions.

75%

Stolarski R.

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2003

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vol. 50

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issue 2

297-318

EN

Description of the recognition specificity between proteins and nucleic acids at the level of molecular interactions is one of the most challenging tasks in biophysics. It is key to understanding the course and control of gene expression and to the application of the thus acquired knowledge in chemotherapy. This review presents experimental results of thermodynamic studies and a discussion of the role of thermodynamics in formation and stability of functional protein-RNA complexes, with a special attention to the interactions involving mRNA 5' cap and cap-binding proteins in the initiation of protein biosynthesis in the eukaryotic cell. A theoretical framework for analysis of the thermodynamic parameters of protein-nucleic acid association is also briefly surveyed. Overshadowed by more spectacular achievements in structural studies, the thermodynamic investigations are of equal importance for full comprehension of biopolymers' activity in a quantitative way. In this regard, thermodynamics gives a direct insight into the energetic and entropic characteristics of complex macromolecular systems in their natural environment, aqueous solution, and thus complements the structural view derived from X-ray crystallography and multidimensional NMR. Further development of the thermodynamic approach toward interpretation of recognition and binding specificity in terms of molecular biophysics requires more profound contribution from statistical mechanics.

17

Fluorescence optical analysis method for assessing homogeneity of granular mixtures

75%

Matuszek D. B., Królczyk J. B., Matuszek D. B., Królczyk J. B.

Metrology and Measurement Systems

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2021

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vol. 28

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issue 1

Refine search results

Energy up-conversion in dilute polyfluorene solutions

Quantification of 5-methyl-2'-deoxycytidine in the DNA

Spectral properties of phthalocyanines incorporated into resting and stimulated human peripheral blood cells.

Fluorescence spectroscopy of semiconductor CdTe nanocrystals: preparation effect on photostability

Comparison of Methods in Studies of Cell Death Mechanisms

Structural factors influencing the reaction rates of 4-aryloxy-7-nitrobenzofurazans with amino acids

Ca2+differently affects hydrophobic properties of guanylyl cyclase-activating proteins (GCAPs) and recoverin.

Synthesis and Characterization of an Efficient New Liquid Laser Dye Material - Chalcone (DMAPPP)

Preliminary studies of phthalocyanine sensitizers incorporated into human leukemia cells from two cell-lines.

Insight into the kinetics and the mode of the interaction between smooth muscle calponin and F-actin.

Application of a carbazole derivative as a spectroscopic fluorescent probe for real time monitoring of cationic photopolymerization

The phenomenon of fluorescence in immunosensors

Simultaneous velocity measurement of phases in a liquid-gas system

Fluorescence decay time distribution analysis of cyclic enkephalin analogues; Influence of solvent and Leu configuration in position 5 on conformation

Salivary aldehyde dehydrogenase - temporal and population variability, correlations with drinking and smoking habits and activity towards aldehydes contained in food

Thermodynamics of specific protein-RNA interactions.

Fluorescence optical analysis method for assessing homogeneity of granular mixtures