Bilirubin degradation in methanol induced by continuous UV-B irradiation: a UHPLC--ESI-MS study.

Degradation of bilirubin in aerobic methanol solution by continuous UV-B irradiation has been investigated in this work. The purpose of this study was to shed more light on bilirubin interaction with the UV-B component of natural sunlight, since bilirubin is a very efficient UV-B absorber located in the skin epidermis. The degradation products have been detected and studied by a combined method of Ultra High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry (UHPLC-ESI-MS). Bilirubin, a toxic pigment which itself is a product of (hemoglobin) degradation in organisms, undergoes its own degradation under aerobic conditions of UV-B continuous irradiation (e.g. photooxidation) that can be partly self-sensitized. Two dipyrrolic structures have been identified as a result of the bilirubin degradation, not including the bilirubin derivative biliverdin whose increase in the irradiated system is synchronous with a time dynamics of bilirubin degradation. It appears that one of dipyrrolic products originates directly from bilirubin and biliverdin molecules, while the other one is probably connected to bilirubin self-sensitized degradation. The precursor role of biliverdin in the degradation process--related to the detected dipyrroles--has not been confirmed.

Single-center prospective, randomized analysis of conventional and eversion carotid endarterectomy.

AIM: Several studies, comparing early and long-term results of the conventional carotid endarterectomy (CEA) and eversion carotid endarterectomy (EEA), were conducted for past 10 years. Nevertheless, it still remaining difficult to choose optimal endarterectomy technique. Choice yet mainly depends of experience of attending surgeon. The aim of this study was the comparison early and long-term results of the EEA and CEA. METHODS: Randomly, 103 patients were operated on in the eversion, and 98 patients in the conventional technique; 97 (48.3%) patients were asymptomatic and 104 (51.7%) had symptomatic lesions. All patients underwent preoperative cervical duplex scanning and neurological examination. The surgical procedure was carried out under general anesthesia. In cases with retrograde blood pressure less than 20 mmHg shunt was used; 78.6% of all CEA were finished up with ''patch'' angioplasty and 21.4% by primary suture. The primary outcomes were perioperative and late mortality, perioperative and late central neurological complications, a long-term survival rate and late restenosis incidence. RESULTS: The mean follow-up was 38 months. Mortality and long-term survival rate were similar in compared groups. The perioperative central neurological complications incidence were comparable in study groups (3.9% vs 12.1% , odds ratio 3.45, 95% confidence interval 1.1-11.1; P=0.029). The late restenosis incidence was significantly lower in eversion group (0.0% vs 6.1%). CONCLUSION: EEA has an advantage over the conventional procedure. The authors recommend CEA in cases when retrograde pressure indicated the use of the intraluminal shunting.

Delayed fluorescence induction transients: mathematical modelling based on the chosen kinetic models.

The paper deals with mathematical modelling of the transients obtained by fitting of delayed fluorescence (DF) induction trace. The transients are in certain, doubtless connection with electrochemical gradient (ECG) formed across thylakoid membranes upon illumination. The fitting of the C and D transients by using consecutive model for first-order reactions (A --> B --> C) showed that they might play a role of the intermediate (B), according to scheme down bellow: ("A1 state")ECG (k1(C transient))--> C transient (k2(C transient))--> products, ("A2 state")ECG (k1(D transient))--> D transient (k2(D transient))--> products. The two ECG controlled "states" (A1 & A2) are not the same, which does not exclude some sort of proportionality. On the other hand, the E band, contributing mainly to the stationary level of DF induction trace, may be fitted by parallel model of at least two first-order reactions.

Temperature dependence of delayed fluorescence induction curve transients.

The temperature dependence of delayed millisecond fluorescence (DF) induction curve transients was investigated. The transients were obtained by keeping intact maize leaf segments in the dark for 30 to 300 s before illumination. The temperature dependence of DF induction revealed abrupt changes in activation energy of the recombination process. Those changes highly overcome the lowest energy barriers for certain types of chemical reactions, implying significant possible alterations in the DF mechanism itself. On the other hand, the particular transients responses expressed some specificities. Both the electrochemical gradient controlled changes, and the temperature induced changes contribute to it.

Relationship between quenching of variable fluorescence and thermal dissipation in isolated thylakoid membranes: similar terminology and mathematical treatments may be used.

Simultaneous measurements of chlorophyll fluorescence and thermal emission using photoacoustic spectroscopy have been done in isolated thylakoid membranes to study the relationship between the photochemical quenching of fluorescence (qPF) and energy storage measured in photoacoustic experiments. It is shown that energy storage can be interpreted as the photochemical quenching of a variable component of thermal dissipation termed qPH. The parameters qPF were similarly sensitive to light intensity as demonstrated by their half-saturation light intensity. However, the nonvariable part of thermal dissipation (Ho) represented a greater proportion of the maximal thermal dissipation yield in comparison with the corresponding non-variable component of fluorescence (Fo) as a result of the thermal energy losses occurring during electron transport. A residual qPH found when qPF was removed indicated the participation of cyclic photosystem I or photosystem II in the measured qPH. The participation of cyclic photosystem I was also suggested by a low constant K, representing the quasi equilibria between (re)oxidized and reduced photosystem II quinone acceptors as determined from the logarithmic plots of the hyperbolic relationship obtained between qPH and light intensity. It is finally concluded that the terminology and mathematical treatments used for fluorescence measurements can be applied to thermal dissipation.

Benzophenone-sensitized lipid peroxidation in linoleate micelles.

Benzophenone-photosensitized peroxidation in linoleic acid micelles (Type I reaction) has been investigated and quantum yields of both sensitizer photolysis and lipid peroxidation have been obtained. Benzophenone as well as its derivative, benzophenone-4'-heptyl-4-pentanoic acid (BHPA) have been utilized as sensitizers in this study. A quantum yield of 1.2 for hydroperoxide formation, compared with a benzophenone disappearance quantum yield of 0.41 (in the same linoleate micellar solution) was obtained; yields of 1.3 and 0.6 were found for comparable systems in which BHPA was the sensitizer. Although such data are consistent with the peroxidation mechanism of chain reaction, it is necessary to know the yields of initiating species to arrive at chain reaction lengths in these systems. Such yields have been determined by flash photolysis. The dependencies of sensitizer photolysis and hydroperoxide yields on linoleate concentration have also been determined in order to elucidate the effects of micelle formation or molecular organization on the peroxidative process. Additionally, for comparison in a saturated surfactant (lipid) system hydrogen abstraction was investigated by photolysis techniques in sodium dodecyl sulfate alone using these two sensitizers.

Hydrogen abstraction from lipids by triplet states of derivatized benzophenone photosensitizers.

Laser photolysis techniques have been used to characterize the reactivity of triplet state lipoidal benzophenone derivatives toward fatty acids and glycerides in benzene solution. The reactivities of benzophenone-4-heptyl-4'-pentanoic acid (BHPA) toward fatty acid compounds having different configurations of olefinic bonds have been determined. The rates of hydrogen abstraction are found to be lower when compared with similar measurements using benzophenone alone. However, the contribution of physical quenching of the triplet derivative by double bonds also appears to be slightly lower than that found with benzophenone itself. The hydrogen abstraction efficiencies of three other benzophenone derivatives toward linoleic acid in benzene have also been measured. For benzophenone incorporated into a fatty acid molecule, there is a limited relationship between structure and photoreactivity. Finally, these sensitizers have been incorporated into mixed SDS/linoleate micelles to determine the effects of molecular organization on photochemical behavior of the sensitizer and lipid.

Radical processes in lipids. Selectivity of hydrogen abstraction from lipids by benzophenone triplet.

Laser photolysis techniques have been used to measure the reactivity of benzophenone triplet (3BZP) toward various fatty acids and two glycerides in benzene solution. Eight compounds varying both in number and in the configuration of olefinic bonds have been examined. It has been found that the rate constant for hydrogen abstraction from these compounds by 3BZP may be related to the number of secondary, allylic and doubly allylic hydrogens in each molecule by the equation: kH = [0.023[H sec] + 0.112[H allylic] + 1.78[H doubly allylic]] x 10(7) M-1s-1