7 research outputs found
The composition of phospholipid model bacterial membranes determines their endurance to secretory phospholipase A2 attack : the role of cardiolipin
Soil bacteria are decomposer organisms crucial for the biodegradation of organic pollutants, mineralization of dead organic matter and the turnover of biogenic elements. In their environment they are constantly exposed to membrane-lytic enzymes emitted to the soil by other microorganisms competing for the same niche. Therefore, the composition and structure of their membranes is of utmost importance for survival in the harsh environment. Although soil bacteria species can be Gram-negative or Gram-positive and their membranes differ significantly, they are formed by phospholipids belonging mainly to three classes: phosphatidylethanolamines (PE), phosphatidylglycerols (PG) and cardiolipins (CL). The correlation of the membrane phospholipid composition and its susceptibility to secretory membrane-lytic enzymes is widely unknown; thus, to shed light on these phenomena we applied the Langmuir monolayer technique to construct models of soil bacteria membranes differing in the mutual proportion of the main phospholipids. To characterize the systems we studied their elasticity, mesoscopic texture, 2D crystalline structure and discussed the thermodynamics of the interactions between their components. The model membranes were exposed to secretory phospholipase A2. It turned out that in spite of the structural similarities the model membranes differed significantly in their susceptibility to s-PLA2 attack. The membranes devoid of cardiolipin were completely degraded, whereas, these containing cardiolipin were much more resistant to the enzymatic hydrolysis. It also turned out that the sole presence of cardiolipin in the model membrane did not guarantee the membrane durability and that the interplay between cardiolipin and the zwitterionic phosphatidylethanolamine was here of crucial importance
Studies of the influence of selected heavy metals on self-organization of bacterial phospholipids
Celem niniejszej pracy by艂o zbadanie wp艂ywu wybranych metali ci臋偶kich na w艂a艣ciwo艣ci fizyczne monowarstw Langmuira utworzonych przez kardiolipin臋, stosowanych jako modele b艂on bakteryjnych. W pracy wykorzystano nast臋puj膮ce metale: Ca2+, Mg2+, Sr2+, Ba2+, Zn2+, Cd2+, Cs+, Ga3+, La3+. Badania zosta艂y przeprowadzone w obecno艣ci fizjologicznego st臋偶enia (0,15 M) NaCl. W cz臋艣ci literaturowej skupiono si臋 na sposobach usuwania metali ci臋偶kich ze 艣rodowiska, kr贸tko scharakteryzowano organizmy glebowe. Przedstawiono budow臋 b艂ony biologicznej, jej przyk艂adowe modele, w tym technik臋 monowarstw Langmuira. Przeprowadzone badania dowiod艂y oddzia艂ywania metali na w艂a艣ciwo艣ci fizyczne b艂ony bakteryjnej. Wykazano, 偶e obecno艣膰 fizjologicznego st臋偶enia (0,15 M) NaCl w subfazie zaburza uporz膮dkowanie cz膮steczek kardiolipiny w monowarstwie. Wap艅, ze wzgl臋du na silne oddzia艂ywanie z kardiolipin膮, silnie kondensuje monowarstw臋. Spo艣r贸d przebadanych dwuwarto艣ciowych metali ci臋偶kich, kadm wywiera podobne efekty jak wap艅 na uporz膮dkowanie TMCL. Jednak偶e najwi臋kszy efekt kondensuj膮cy obserwuje si臋 dla metali tr贸jwarto艣ciowych. Wizualizacja przy pomocy mikroskopii k膮ta Brewstera pozwoli艂a wykaza膰, 偶e badane metale zmieniaj膮 tekstur臋 monowarstw. Natomiast obliczony modu艂 艣ci艣liwo艣ci pozwoli艂 w bardziej ilo艣ciowy spos贸b opisa膰 efekty zwi膮zane z kondensacj膮, czy te偶 rozpr臋偶aniem si臋 monowarstw.The main objective of this BA thesis was to test the influence of selected heavy metals on the physical properties of cardiolipin Langmuir monolayers used as model bacterial membranes. The following metals were applied: Ca2+, Mg2+, Sr2+, Ba2+, Zn2+, Cd2+, Cs+, Ga3+ and La3+. The experiments were performed in the presence of a physiological concentration of NaCl (0.15 M). In the BA thesis the techniques of removing heavy metals from the environment, brief characterization of soil organisms are covered. Next, the structure of the biological membrane is outlined, and the membrane models utilized in science are referred. The results confirm the influence of heavy metals on the physical properties of the bacterial membrane. What is more, the presence of the physiological concentration of NaCl (0,15 M) in subphase distorts the organization of the cardiolipin molecules in the monolayer. Due to its strong interaction with cardiolipin, calcium substantially condensates the monolayer. Cadmium produces similar effects to calcium on the TMCL. The most substantial condensing effect was observed for the trivalent metals and a change in texture for all the used metals was observed through the visualization of the monolayer using Brewster angle microscopy. The calculated modules of compressibility allowed to more quantitatively characterize the condensation or expansion effects
Investigation of the interactions of phospholipase A2 with model membranes of soil bacteria and fungi - studies of the influence of membrane composition and presence of persistent organic pollutants on enzyme activity
Trwa艂e zanieczyszczenia organiczne (TZO) akumuluj膮ce si臋 w glebie stanowi膮 znaczne zagro偶enie dla bakterii i grzyb贸w glebowych, jako 偶e wbudowuj膮c si臋 do b艂on kom贸rkowych mog膮 zwi臋ksza膰 ich podatno艣膰 na aktywno艣膰 wydzielniczych enzym贸w znajduj膮cych si臋 w glebie. Celem niniejszej rozprawy by艂o zastosowanie fosfolipidowych monowarstw Langmuira jako modeli b艂on destruent贸w glebowych i przebadanie jak sk艂ad b艂ony oraz obecno艣膰 w niej TZO wp艂ywaj膮 na jej odporno艣膰 na dzia艂anie fosfolipazy A2 (PLA2). W cz臋艣ci literaturowej rozprawy zreferowano aktualn膮 wiedz臋 dotycz膮c膮 budowy b艂on kom贸rkowych, sposob贸w modelowania membran i zjawisk w nich zachodz膮cych oraz om贸wiono zalety i wady zastosowania monowarstw Langmuira jako modeli biomembran. W cz臋艣ci eksperymentalnej om贸wiono wszystkie rutynowe procedury eksperymentalne oraz scharakteryzowano zastosowane instrumenty badawcze. Przeprowadzone badania wykaza艂y, 偶e monowarstwy wielosk艂adnikowe symuluj膮ce b艂ony bakteryjne s膮 bardziej odporne na dzia艂anie PLA2 ni偶 jednosk艂adnikowe warstwy fosfolipidowe. Okaza艂o si臋, 偶e szczeg贸lnie odporne s膮 membrany z du偶ym udzia艂em kardiolipiny, a w szczeg贸lno艣ci te zawieraj膮ce jednocze艣nie kardiolipin臋 i fosfatydyloetanoloamin臋. Obecno艣膰 TZO w modelowych b艂onach zwi臋ksza艂a ich podatno艣膰 na aktywno艣膰 PLA2, przy czym wp艂yw tych zanieczyszcze艅 m贸g艂 by膰 niwelowany przez odpowiednio dobrany sk艂ad membran.Persistent organic pollutants (POP) accumulate in the soils and endanger the soil bacteria and fungi. They can be incorporated into the membranes and increase their susceptibility to secretory enzymes present in the soil. The aim of this thesis was the application of phospholipid Langmuir monolayers as the models of soil decomposer membranes and the investigation of the effect of the membrane composition and POP incorporation on the resistivity of the model membrane to the hydrolytic activity of phospholipase A2 (PLA2). In the bibliographic part the recent knowledge of the membrane structure, membrane modeling, membrane-related phenomena and the application of Langmuir monolayers as membrane models was referred. In the experimental part the routine experimental procedures and the applied scientific instruments were characterized. The studies proved that multicomponent monolayers mimicking bacterial membranes are more resistant to the action of PLA2 than one-component phospholipid monolayers. It turned out, that the monolayers with high cardiolipin content, especially these containing both cardiolipin and phosphatidylethanolamine, are especially resistant to PLA2 attack. The presence of POP in the model membranes increased their susceptibility to PLA2 degradation; however the effect of these pollutants could be limited by the proper phospholipid content of the membrane
"Nature or nurture" : how environmental factors influence the conformational memory of amyloid fibrils
Chiral recognition via a stereodynamic vanadium probe using the electronic circular dichroism effect in differential Raman scattering
Chiral recognition via a stereodynamic vanadium probe using the electronic circular dichroism effect in differential Raman scattering
Intermolecular interactions sensitive to chirality occur in many biological events. We report a complex formation between a versatile vanadium-based probe and a chiral co-ligand monitored via the combination of electronic circular dichroism (ECD) and Raman scattering. This "ECD-Raman" effect was discovered relatively recently and can be measured using a Raman optical activity (ROA) spectrometer. Simulated spectra based on experimental ECD and degree of circularity (DOC) values agree with the observed ones. Sensitive recognition of the chiral enantiopure co-ligand is thus enabled by a combination of resonance of the excitation light with the diastereoisomeric complex, co-ligand complexation, circular dichroism, and polarized Raman scattering from the achiral solvent. Relatively dilute solutions could be detected (10(-4) mol dm(-3)), about 1000x less than is necessary for conventional ROA detection of the pure co-ligand and comparable to concentrations needed for conventional ECD spectroscopy. The results thus show that differential ECD-Raman measurements can be conveniently used to monitor molecular interactions and molecular spectroscopic properties