Dynamics of the excited state of the primary electron donor in reaction centers of Rhodopseudomonas viridis as revealed by hole burning at 1.7K. Different conformational states

The spectra of absorbance changes (delta A) due to the formation of P+Q- (P, primary electron donor, Q, primary quinone acceptor) at 1.7K in Rhodopseudomonas viridis reaction centers (RCs) excited at 1014 nm has been shown to include, besides a progression of broad (170-190 cm-1) Gaussian vibronic bands separated by 150 cm-1, a 'narrow' structure near 1014 nm which can be simulated by a Lorentian zero-phonon hole (ZPH) and Lorentian one-mode (26.8 cm-1) phonon wings. The widths of ZPH of approximately 17 cm-1 for delta A reflecting the formation of P+Q- decaying in the ms time domain and of 6.8 +/- 0.4 cm-1 for P+Q- decaying in the min time domain at 1.7K, seems to correspond to different conformations of RCs with a relaxation time of P* of approximately 0.6 ps (in agreement with measurements in this time domain) and 1.6 +/- 0.1 ps, respectively. The comparison of the spectra of delta A in the region of the BL band for slow (min) and fast (ms) decaying components suggests a different mutual arrangement of P and BL for different conformations of RCs. It is assumed that the broad and narrow structures of the P band reflect the transitions to two configurations with different P-protein interactions. 'Narrow' structure of delta A spectrum with essentially the same phonon wings and ZPH (width of 3.8 +/- 0.4 cm-1) was observed within the P band when HL was photoreduced at 1.7K.     

Impacts of cage culture on physico-chemical and bacteriological water quality in Lake Volta,Ghana

The effects of cage fish farming on physico-chemical and bacteriological water quality in Lake Volta, Ghana, were investigated in 2013–2014. Farmed and unfarmed (control) areas of the lake were selected for monitoring. Nutrients, temperature, dissolved oxygen, conductivity, turbidity, pH, total coliforms, Pseudomonas and Vibrio spp. in the water were monitored monthly. Analyses of the water samples were carried out according to standard procedures. Physico-chemical quality of the water in both farm and control sites were within ranges typical of minimally impacted water and did not vary significantly between the two contrasting sites. The bacteriological analysis, however, revealed contamination of the lake water by fish farming. The bacterial counts at the farmed sites were significantly higher (p < 0.05) than those of the control sites, with figures at the farmed sites ranging from 132 to 1 708 cfu 100 ml?1 for total coliforms, 514 to 5 170 cfu 100 ml?1 Pseudomonas spp. and 14 to 516 cfu 100 ml?1 for Vibrio spp. The results suggested that cage fish farming has increased bacterial loads in the lake water, but has had minimal impact on its physico-chemical quality.     

Nuclear wavepacket motion between P and P(+)B(A)(-) potential surfaces with subsequent electron transfer to H(A) in bacterial reaction centers. 1. Room temperature

Formation and coherent propagation of nuclear wavepackets on potential energy surfaces of the excited state of the primary electron donor P and of the charge transfer states P(+)B(A)(-) and P(+)H(A)(-) were studied in native and pheophytin-modified Rhodobacter sphaeroides R-26 reaction centers (RCs) induced by 25 fs excitation (where B(A) and H(A) are the primary and secondary electron acceptors, respectively). The processes were monitored by measuring coherent oscillations in kinetics of the time evolution of the stimulated emission band of P at 935 nm, of the absorption band of B(A)(-) at 1020 nm, and of the bleaching band of H(A) at 760 nm. It was found that the nuclear wavepacket motion on the 130-140 cm(-1) surface of P is directly induced by light absorption in P. When the wavepacket approaches the intersection between P and P(+)B(A)(-) surfaces at 120 and 380 fs delays, the formation of intermediate mixed-state emitting light at 935 nm (P) and absorbing light at 1020 nm (P(+)B(A)(-)) takes place. At the latter time, the wavepacket is transferred to the 32 cm(-1) mode which can belong to the P hypersurface effectively transferring the wavepacket to the P(+)B(A)(-) surface or can represent a diabatic surface which is formed by the states P and P(+)B(A)(-). The wavepacket motion on the P(+)B(A)(-) surface or on the P(+)B(A)(-) part of the mixing surface is accompanied by irreversible electron transfer to H(A). This process is monitored by the kinetics of 1020 nm band development and 760 nm band bleaching (delayed with respect to 1020 nm band development) which both have the enhanced 32 cm(-1) mode in Fourier transform (FT) spectra. The mechanism of wavepacket transfer from the 130-140 cm(-1) to the 32 cm(-1) mode is discussed.     

Nuclear wave packet motion between P* and P(+)B(A)(-) potential surfaces with a subsequent electron transfer to H(A) in bacterial reaction centers at 90 K. Electron transfer pathway

In Rhodobacter sphaeroides R-26 reaction centers (RCs) the nuclear wave packet induced by 25 fs excitation at 90 K moves on the primary electron donor P* potential energy hypersurface with initial frequency at approximately 130 cm(-1) (monitored by stimulated emission measurement). At the long-wavelength side of P* stimulated emission at 935 nm the wave packet is transferred to the surface with P(+)B(A)(-) character at 120, 380, 1.2 fs, etc. delays (monitored by measurement of the primary electron acceptor B(A)(-) band at 1020 nm). However, only beginning from 380 fs delay and later the relative stabilization of the state P(+)B(A)(-) is observed. This is accompanied by the electron transfer to bacteriopheophytin H(A) (monitored by H(A) band measurement at 760 nm). The most active mode of 32 cm(-1) in the electron transfer and its overtones up to the seventh were found in the Fourier transform spectrum of the oscillatory part of the kinetics of the P* stimulated emission and of the P(+)B(A)(-) and P(+)H(A)(-) formation. This mode and its overtones are apparently populated via the 130 cm(-1) vibrational mode. The deuteration of the sample shifts the fundamental frequency (32 cm(-1)) and all overtones by the same factor of approximately 1.3. This mode and its overtones are suppressed by a factor of approximately 4.7 in the dry film of RCs. The results obtained indicate that the 32 cm(-1) mode might be related to a rotation of hydrogen-containing groups (possibly the water molecule) participating in the modulation of the primary electron transfer from P* to B(A)(-) in at least 35% of RCs. The Brookhaven Protein Data Bank (1PRC) displays the water molecule located at the position HOH302 between His M200 (axial ligand for P(B)) and the oxygen of ring V of B(A) which might be a part (approximately 35%) of the molecular pathway for electron transfer from P* to B(A).     

A New Pathway of Photoinactivation of Photosystem II. Irreversible Photoreduction of Pheophytin Causes Loss of Photochemical Activity of Isolated D1–D2–Cytochrome b559 Complex

A new pathway of photoinactivation of photosystem II (PS II) connected with irreversible photoaccumulation of reduced pheophytin (Ph) in isolated D1–D2–cytochrome b ₅₅₉ complexes of reaction center (RC) of PS II was discovered. The inhibitory effects of white light illumination on photochemical activity of D1–D2–cytochrome b ₅₅₉ complexes of RCs of photosystem II, isolated from pea chloroplasts, have been compared under anaerobic conditions in the absence and in the presence of sodium dithionite, electron transfer from which to the oxidized primary electron donor P680⁺ results in the photoaccumulation of anion-radical of the primary electron acceptor, PH. In both cases, prolonged illumination (1-5 min, 120 W/m²) led to a pronounced loss of the photochemical activity as it was monitored by measuring the amplitude of the reversible photoinduced absorbance changes at 682 nm related to the photoreduction of Ph. The extent of the photoinactivation depended on the illumination time and pH of the medium. At pH 8.0, the presence of dithionite during photoinactivation brought about a protective effect compared to that in a control sample. In contrast, lowering pH to 6.0 increased the sensitivity to photoinactivation in the dithionite containing samples. For 5 min irradiation, the photochemical activity in the absence and in the presence of dithionite decreased by 35 and 72%, respectively (this was accompanied by an irreversible bleaching of the pheophytin Q_x absorption band at 542 nm). Degradation of the D1 and D2 proteins was not observed under these conditions. A subsequent addition of an electron acceptor, potassium ferricyanide, to the illuminated samples restored neither the amplitude of the signal at 682 nm nor absorption at 542 nm. It is suggested that at pH < 7.0 the photoaccumulated PH is irreversibly converted into a secondary, most probably protonated form, that does not lead to destruction of the RCs but prevents the photoformation of the primary radical pair [P680⁺PH]. A possible application of this effect to photoinactivation of PS II in vivo is discussed.     

Serious adverse events following treatment with ivermectin for onchocerciasis control: a review of reported cases

This paper presents a summary of reported cases of Serious Adverse Events (SAEs) following treatment with Mectizan^® (ivermectin, Merck, Sharpe &; Dohme) in onchocerciasis mass treatment programs from January 1, 1989 to December 31, 2001 through a passive surveillance system. A total of 207 SAE cases were reported out of approximately 165 million reported treatments delivered during the period under review, giving rise to a cumulative incidence of 1 reported SAE per 800,000 reported treatments. The mean age was 40 years and 70% of the cases were males. The mean time between ivermectin intake and onset of illness was 1 day. For 57% of the cases (n = 118), that was their first exposure to ivermectin. The majority of cases were reported from Cameroon (n = 176; 85%) with peaks in the incidence of SAE reporting in 1989–1991 and 1994–1995 when the program expanded to ivermectin-naïve populations. Fifty-five percent of the cases from Cameroon (i.e. 97 out of 176 cases) were encephalopathic and were reported from the central-southern region of the country; two-thirds of these cases were 'probable' or 'possible' cases of Loa loa encephalopathy temporally related to ivermectin treatment. Reporting bias may explain some but not all of the differences in SAE reporting between the 34 onchocerciasis-endemic countries that have, or have had, mass treatment programs. Further research is needed to understand the apparent clustering of encephalopathy cases in central-southern Cameroon since L. loa infection alone probably does not explain the increased incidence of this type of SAE from this region.     

Mechanism of charge separation and their stabilization in bacterial reaction centers

The nuclear wavepacket formed by 20-fs excitation on the P* potential energy surface in native and mutant (YM210W and YM210L) reaction centers of Rhodobacter (Rb.) sphaeroides and Chloroflexus (C.) aurantiacus RCs was found to be reversibly transferred to the P+BA- surface at 120, 380, and 640-fs delays (monitored by measurements of BA- absorption at 1020-1028 nm). The reaction centers of YM210W(L) mutant show the most simple pattern of fs oscillations with a period of 230 fs in stimulated emission from P* and in the product P+BA-. The mechanisms of the electron transfer pathway between P* and BA and of the stabilization of the state P+BA- in bacterial reaction centers are discussed.     

Targeting CoV-2 spike RBD and ACE-2 interaction with flavonoids of Anatolian propolis by in silico and in vitro studies in terms of possible COVID-19 therapeutics

Propolis is a multi-functional bee product rich in polyphenols. In this study, the inhibitory effect of Anatolian propolis against SARS-coronavirus-2 (SARS-CoV-2) was investigated in vitro and in silico. Raw and commercial propolis samples were used, and both samples were found to be rich in caffeic acid, p-coumaric acid, ferulic acid, t-cinnamic acid, hesperetin, chrysin, pinocembrin, and caffeic acid phenethyl ester (CAPE) at HPLC-UV analysis. Ethanolic propolis extracts (EPE) were used in the ELISA screening test against the spike S1 protein (SARS-CoV-2): ACE-2 interaction for in vitro study. The binding energy values of these polyphenols to the SARS-CoV-2 spike and ACE-2 protein were calculated separately with a molecular docking study using the AutoDock 4.2.6 program. In addition, the pharmacokinetics and drug-likeness properties of these eight polyphenols were calculated according to the SwissADME tool. The binding energy value of pinocembrin was highest in both receptors, followed by chrysin, CAPE, and hesperetin. Based on the in silico modeling and ADME (absorption, distribution, metabolism, and excretion) behaviors of the eight polyphenols, the compounds exhibited the potential ability to act effectively as novel drugs. The findings of both studies showed that propolis has a high inhibitory potential against the Covid-19 virus. However, further studies are now needed.     

The Effects of Dietary Selenium and Vitamin E and their Combination on the Fatty Acids of Erythrocytes,Bone Marrow and Spleen Tissue Lipids of Lambs

The object was to determine the influence of dietary vitamin E, selenium and their combination on the fatty acid con-tent of erythrocytes, bone marrow and spleen lipids of Akkaraman lambs. After supplementation for 15 days, the amount of all fatty acids was slightly higher (p < 0·05) in the vitamin E as compared to the control group, whereas the amount of longer fatty acids was significantly higher (p < 0·01, p < 0·001) in the selenium and combination groups. On the thirtieth day, the amount of all fatty acids was slightly high (p < 0·5) in all the supplemented groups in comparison with the control group. In the bone marrow lipids, the amount of longer fatty acids was decreased (p < 0·05, p < 0·01, p < 0·001) in the vitamin E and combination groups as compared to the control. Although the amount of some fatty acids was high (p < 0·05, p < 0·01) in the selenium group compared to the control, linoleic (18:2), linolenic (18:3) and the polyunsaturated fatty acids (PUFA) were lower (p < 0·05, p < 0·001). In the spleen lipids, the amount of longer fatty acids was slightly decreased (p < 0·05) in the vitamin E group as compared with the control; however the amount of longer fatty acids was significantly higher (p < 0·05, p < 0·01) in the selenium and combination groups in comparison to the control group. Thus dietary supplementation with selenium was more effective than dietary vitamin E supplementation in altering the fatty acid content of the erythrocyte, bone marrow and spleen lipids. © 1997 John Wiley & Sons, Ltd.