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11	Časově rozlišená fluorescence ve výzkumu kapalných a kondenzovaných systémů na bázi biopolymer-tenzid. / Time-resolved fluorescence study of liquid and condensed systems based on biopolymer-surfactant interactions. Černá, Ladislava January 2014 (has links) This thesis studies properties of hydrogel, which arises on the basis of electrostatic and hydrophobic interactions between hyaluronan chain and micelles of cationic surfactant. A native sodium hyaluronan at molecular weight 750–1 000 kDa and a cationic surfactant CTAB (cetyltrimethylammonium bromide) were used. This hydrogel was assessed as a material for drug delivery systems. The hydrogels were made by mixing 200mM CTAB with 0.5% hyaluronan, both dissolved in 0.15M aqueous solution of NaCl simulating physiological solution. Methods used in this study were steady-state and time-resolved fluorescence spectroscopy, more accurately time-resolved emission spectra (TRES) and deconvolution of steady-state emission spectra of a whole sample by means of parameters gained from fluorescence intensity decays at a set of wavelenghts. Selected systems were investigated by three fluorescent probes, prodan, laurdan and rhodamine 6G. The first two mentioned probes were in hydrogel localized only within micelles in three different microenvironments. Rhodamine 6G pointed out that in hydrogel the aqueous environment is significantly restricted in comparison to purely micellar solution. In addition, rhodamine informed about less available micelle surfaces, caused by hyaluronan chains occupation. There were no interactions between the probes and hyaluronan chains. Freshly made hydrogels showed almost the same results as after a week of maturation under its supernatant.
12	Investigating and Modeling Possible Mechanisms by Which Healthy Cell Membranes Become Resistant to Hydrolysis by Secretory Phospholipase A2 Nelson, Jennifer 15 July 2008 (has links) (PDF) Secretory phospholipase A2 (sPLA2) behaves differently toward the membranes of healthy cells compared to those of damaged or dying cells. The enzyme catalyzes rapid and sustained hydrolysis of compromised cells consistent with a simple catalytic mechanism. In contrast, when healthy cells are incubated with sPLA2, they become resistant to hydrolytic attack as manifest by three unusual observations: First, hydrolysis is transient and represents only a small fraction of the total membrane phospholipid content. Second, subsequent addition of sPLA2 fails to generate additional product. Third, the apparent potency of the enzyme to cause the membrane to be refractory is much greater than the potency for catalyzing hydrolysis. The mechanism responsible for this resistance has not yet been identified. Using Monte Carlo and direct analytical methods, we have developed a model capable of explaining all three of these observations. The model requires two salient elements: only a small pool of phospholipids in the healthy cell membrane is available for catalysis by sPLA2, and hydrolyzed phospholipids are re-acylated and restored very slowly to the accessible pool. The requirement for initial hydrolysis (as opposed to the simple physical presence of the enzyme as previously thought) was confirmed experimentally. Additional evidence has shown that the membrane does not remain permanently in its resistant state. Over time, the membrane resets to its original state. The model also predicts that total substrate, reacylation rate, and the return rate of phospholipids to the membrane should all be constant as enzyme concentration is varied. This prediction was tested by quantitative analysis of hydrolysis time courses at varied enzyme concentrations. Experiments with fluorescent probes, merocyanine 540 and laurdan suggest, that resistance may also involve physical changes to the membrane beyond the kinetic mechanisms hypothesized in the model. secretory phospholipase a2 resistance merocyanine 540 laurdan cell membrane Cell and Developmental Biology Physiology
13	Synthesis of Bacterial Glycerophospholipids for Biomembrane Model Studies: A Means to Advanced Biofuels Adulley, Felix 01 December 2023 (has links) (PDF) To reduce reliance on fossil fuels, sustainable biofuels are being pursued, especially advanced biofuels like 1-butanol that have higher energy content and greater compatibility with existing infrastructure than ethanol. A persistent challenge is the yield-limiting toxicity of biofuels and process solvents, such as tetrahydrofuran, to the microbes that ferment biomass into biofuel. The cell membrane is a focal point of toxicity, and understanding how it interacts with fuels and solvents is key to improving yield. Phospholipid bilayers are the core of biomembranes, and model biomembranes of defined composition provide the ideal platform for biophysical studies. To this end, glycerophospholipids characteristic of Bacillus subtilis, a model producer organism, were synthesized. Two fatty acids (iso- and anteisopentadecanoic acids) characteristic of Bacilli were synthesized and incorporated into representative phosphatidic acid, phosphatidylethanolamine and phosphatidylglycerol lipids. The validated synthetic approach opens the door to future studies on the interaction of biofuels and solvents with biomembranes. phospholipids cell membrane laurdan fluorescence membrane fluidity biofuel Bacillus subtilis Biochemistry Organic Chemistry
14	Possible Molecular Mechanism to Account for Wavelength Dependence of Equilibration Rates of Patman and Laurdan in Phosphatidylcholine Bilayers Franchino, Hannabeth A. 12 May 2011 (has links) (PDF) Patman is a fluorescent membrane probe related to Laurdan. The structural distinctions between the two probes are the lengths of the aliphatic tails (eleven carbons in Laurdan and fifteen in Patman) and the presence of a trimethylammonium group on Patman that produces a positively-charged head. Preliminary studies exploring Patman as a probe to detect membrane properties during apoptosis revealed that the fluorescence intensity of two edges of the emission spectrum (435 and 500 nm) stabilizes at different rates as the probe binds to the cell membrane. To test whether these differences represent dissimilarities in probe binding to ordered and disordered domains, experiments were conducted to monitor Patman equilibration with bilayers composed of various mixtures of saturated and unsaturated phosphatidylcholines at temperatures above, at, and below the main thermotropic phase transition. In general, Patman equilibrated more rapidly with bilayers in the liquid-disordered phase than in the solid-ordered phase. With solid phase membranes, the fluorescence stabilized faster at 500 nm than at 435 nm. Similar, yet more subtle, results occurred in the lipid disordered phase. In contrast, the situation was reversed at the phase transition temperature; equilibration was faster at 435 nm than at 500 nm. To determine whether these results reflected specific properties of Patman, the experiments were repeated with Laurdan, and several distinctions were observed. First, equilibration with solid phase lipids was faster than for Patman and not different from equilibration with the fluid phase. Second, differences in rates between the two wavelengths were less than with Patman for solid phase membranes but greater than with Patman for melted bilayers. Third, at the phase transition temperature, the difference in equilibration rates was the opposite of the result obtained with Patman. Computer simulations were used to assist with interpretation of these results. The data suggest that both probes bind superficially to the membrane before incorporating among the lipid molecules. Once within the membrane, Patman localizes to at least two distinct depths within the bilayer. Probe molecules in the shallow, more hydrated position favor 500 nm emission and those occupying a deeper, dehydrated position emit primarily at 435 nm. Laurdan's equilibration additionally represents movement of the probe between leaflets and multiple bilayers. Patman Laurdan equilibration wavelength membrane bilayer dynamics solid phase liquid phase phase transition Cell and Developmental Biology Physiology
15	Studium mikroviskozity membránových systémů na bázi iontových amfifilních párů / Study of microviscosity of membrane systems based on ionic amphiphilic pairs Moslerová, Lenka January 2021 (has links) In this master ‘s thesis, catanionic vesicles formed by the pseudo-double-chain complex CTA – DS were investigated from the point of view of microviscosity. Samplesand of cationic vesicles contained 23, 43 and 53 mol. % of cholesterol and the double-chain surfactant DODAC. Cationic vesicles were prepared for visual observation, their stability was determined by DLS and the prepared system was further investigated. Microviscosity was determined from fluorescence anisotropy. To study the outer part of the membrane, laurdan fluorescent probes were used whereas diphenylhexatriene was used for the inner part of the membrane. This method has been proven to be suitable because it reflects the conditions of the membrane. Moreover, a 1,3-bispyrenylpropane probe forming intramolecular excimers was used to study the microviscosity in the vesicle bilayer. The dicyanovinyljulolidine (DCVJ) probe was applied in the case of the molecular rotor technique. It has been shown that in the case of the DCVJ probe, the molecular rotor technique is practically unusable, due to the fact that the probe has a low quantum yield at low temperatures. Also, the excimer formation of P3P probes does not lead to the expected results. The cationic vesicles do not seem to support this formation, as they are too closely related. This type of probe can be used for the selected system with some restrictions.
16	Studium kvality hydrofobních domén ve fázově separovaných hydrogelech / Studying the quality of hydrophobic domains in the phase separated hydrogels Burešová, Natálie January 2018 (has links) The thesis deals with the study of hydrophobic domains in phase separated hydrogels. Two types of polyelectrolytes (hyaluronan, dextran) and oppositely charged surfactants (carbethopendecinium bromide, sodium dodecylsulphate ) are used. Phase separated hydrogels are formed by electrostatic interactions. The target of the thesis is to study the polarity of environment in phase separated hydrogeles by fluorescence spectroscopy. Fluorescence measurements is performed by using pyrene, Nile red and laurdane as fluorescence probes. All probes are sensitive to the polarity of the environment. The results showed that probes can be expected in the polar environment of hydrogels.
17	Studium membránových vlastností liposomálních systémů pomocí fluorescenční spektroskopie / Study of membrane properties of liposomal systems using fluorescence spectroscopy Zbořilová, Hana January 2021 (has links) The presented diploma thesis is focused on the preparation, characterization and study of membrane properties of liposomal systems which were composed of the neutral phosphatidylcholine (DPPC), cholesterol, negatively charged phosphatidylglycerol (DPPG), polyethylenglycol bounded to phosphatidylethanolamine (PEG5000–PE) and polycation N,N,N-trimethylchitosan (TMC). The influence of individual components and their concentrations on the average particle size, zeta potential and changes in the outer and inner part of the bilayer was investigated. In this matter, methods of dynamic and electrophoretic light scattering and fluorescence spectroscopy with the application of laurdan and DPH probes were used. Based on the above-mentioned parameters, concentrations of components that most suitably influence properties of liposomes in terms of the intended application were selected for the definite complex. It was managed to prepare a liposomal complex stealth liposome–N,N,N-trimethylchitosan, which, due to the optimized composition, could have suitable attributes as a drug delivery system for inhalation administration of biologically active substances.
18	Solvatationsdynamik an biologischen Grenzschichten / Solvation dynamics at biological interfaces Seidel, Marco Thomas 05 November 2003 (has links) No description available. 540 Chemie Mathematics and Computer Science Femtochemie Femtobiologie Laserspektroskopie Zeitkorreliertes Einzelphotonenzählen Fluoreszenzkonversionsspektroskopie Photon-Echo-Spektroskopie Peakshift Ultraschnelle Dynamik Strukturelle Relaxation Solvatation Stokes-Shift Wasser Wassernanotröpfchen inverse Mizellen Membranen Lipid-Vesikel AOT DMPC HIDCI Laurdan TICT femtochemistry femtobiology laser spectroscopy time-correlated single photon counting fluorescence up-conversion photon-echo spectroscopy peakshift ultrafast dynamics structural relaxation solvation Stokes-shift water water nano-droplets reverse micelles membranes lipid vesicles AOT DMPC HIDCI laurdan TICT 35.16 35.21 35.25 35.78 RRQ 000: Laser-Spektroskopie {Physik} SIL 000: Laser-Chemie {Strahlungschemie} SMG 000: Lösungen {Chemie} WCE 000: Photobiologie {Biophysik} WHC 100: Zellmembranen Zelloberfläche Zellwand intrazelluläre Membranen {Cytologie}

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