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31.
A deletion mutant that lacks the Psb30 protein, one of the small subunits of Photosystem II, was constructed in a Thermosynechococcus elongatus strain in which the D1 protein is expressed from the psbA3 gene (WT*). The ΔPsb30 mutant appears more susceptible to photodamage, has a cytochrome b559 that is converted into the low potential form, and probably also lacks the PsbY subunit. In the presence of an inhibitor of protein synthesis, the ?Psb30 lost more rapidly the water oxidation function than the WT* under the high light conditions. These results suggest that Psb30 contributes to structurally and functionally stabilise the Photosystem II complex in preventing the conversion of cytochrome b559 into the low potential form. Structural reasons for such effects are discussed. 相似文献
32.
Diazotization of primary aromatic amines with isoamyl nitrite in benzene at room temperature was studied employing EPR and spin trapping techniques. Nitrosodurene (ND). 2-methyl-2-nitrosopropane (MNP). and 5,5-dimethyl-pyrroline N-oxide (DMPO) were used as spin trapping agents. Aryl radicals were detected employing ND and MNP. Using DMPO as a spin trap most of the amines produced EPR spectra ascribed to adducts with aniline-type radicals (N-centred radicals). The assignments were verified using 15JN-labeled anilines. Similar spectra of DMPO adducts were recorded from amines treated with benzoyl peroxide or benzophenone plus UV. Possible mechanisms of formation of these adducts (radical trapping versus nucleophilic addition to DMPO followed by oxidation) during treatment of the amines with isoamyl nitrite are discussed. 相似文献
33.
Aryna V. Lado Alexander V. Piskunov Georgy K. Fukin Vladimir N. Ikorskii Vladimir K. Cherkasov 《Inorganica chimica acta》2005,358(15):4443-4450
Addition of 3,6-di-tert-butyl-o-benzoquinone (3,6-DBBQ) to SnCl2 in THF leads to the oxidation of Sn(II) to Sn(IV) with formation of catecholate complex (3,6-DBCat)SnCl2 · 2THF (1), where 3,6-DBCat is 3,6-di-tert-butyl-catecholate dianion. The reaction of 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone (IBQ-Pri) also proceeds on the oxidative-addition mechanism yielding bis-iminosemiquinonato species (ISQ-Pri)2SnCl2(2), where ISQ-Pri is anion-radical 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzosemiquinolate. The complexes have been characterized by IR, X-band EPR, 1H NMR (for 1) spectroscopy and magnetochemistry (for 2). X-ray analysis data show the distorted octahedral environment of tin(IV) for both complexes. Complex 1 is diamagnetic (ground state S = 0), while 2 has triplet ground state (S = 1, biradical). Catecholate complex 1 is able to be a spin trap for different organic radicals. 相似文献
34.
Two novel ion-pair complexes, [RBzIQl]+[Ni(mnt)2]− (mnt2− = maleonitriledithiolate, [RBzIQl]+ = 4-R-benzylisoquinolinium; R = H (1), Cl (2)) have been characterized structurally and magnetically. The anions and [BzIQl]+ cations of 1 form 1D column of alternating between cations and anions via π?π stacking interaction between Ni(mnt)2 plane and isoquinoline ring, and the Ni(mnt)2 anions between adjacent columns exist C?N, C?N, and N?N interaction. The anions and cations of 2 stack into well-segregated columns in the solid state; and the Ni(III) ions form a 1D zigzag chain in a Ni(mnt)2 column through intermolecular Ni?S, S?S, Ni?Ni or π?π interactions. The chain is uniform in 2 with the Ni?Ni distances of 3.784 Å. Magnetic susceptibility measurements for these complexes in the temperature range 1.8-300 K show that 1 exhibits antiferromagnetic coupling behavior, and 2 exhibits unusual magnetic phase transitions around 45 K. The overall magnetic behavior for 2 indicates the presence of antiferromagnetic interaction in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT). 相似文献
35.
Paul W. Weber Laurens E. Howle Mark M. Murray Joseph M. Corless 《Biophysical journal》2011,100(3):525
When radiolabeled precursors and autoradiography are used to investigate turnover of protein components in photoreceptive cone outer segments (COSs), the labeled components—primarily visual pigment molecules (opsins)—are diffusely distributed along the COS. To further assess this COS labeling pattern, we derive a simplified mass-transfer model for quantifying the contributions of advective and diffusive mechanisms to the distribution of opsins within COSs of the frog retina. Two opsin-containing regions of the COS are evaluated: the core axial array of disks and the plasmalemma. Numerical solutions of the mass-transfer model indicate three distinct stages of system evolution. In the first stage, plasmalemma diffusion is dominant. In the second stage, the plasmalemma density reaches a metastable state and transfer between the plasmalemma and disk region occurs, which is followed by an increase in density that is qualitatively similar for both regions. The final stage consists of both regions slowly evolving to the steady-state solution. Our results indicate that autoradiographic and cognate approaches for tracking labeled opsins in the COS cannot be effective methodologies for assessing new disk formation at the base of the COS. 相似文献
36.
María N. Barrachina Aurelio M. Sueiro Vanessa Casas Irene Izquierdo Lidia Hermida‐Nogueira Esteban Guitin Felipe F. Casanueva Joaquín Abin Montserrat Carrascal María Pardo ngel García 《Proteomics》2019,19(1-2)
Plasma‐derived extracellular vesicles (EVs) have been extensively described as putative biomarkers in different diseases. Interestingly, increased levels of EVs subpopulations are well known to associate with obesity. The goal of this study is to identify EVs‐derived biomarkers in plasma from obese patients in order to predict the development of pathological events associated with obesity. Samples are obtained from 22 obese patients and their lean‐matched controls are divided into two cohorts: one for a 2D fluorescence difference gel electrophoresis (2D‐DIGE)‐based study, and the other one for a label free LC–MS/MS‐based approach. EVs are isolated following a serial ultracentrifugation protocol. Twenty‐two and 23 differentially regulated features are detected from 2D‐DIGE and label free LC–MS/MS, respectively; most of them involve in the coagulation and complement cascades. Remarkably, there is an upregulation of complement C4, complement C3, and fibrinogen in obese patients following both approaches, the latter two also validated by 2D‐western‐blotting in an independent cohort. These results correlate with a proinflammatory and prothrombotic state of those individuals. On the other hand, a downregulation of adiponectin leading to an increased risk of suffering cardiovascular diseases has been shown. The results suggest the relevance of plasma‐derived‐EVs proteins as a source of potential biomarkers for the development of atherothrombotic events in obesity. 相似文献
37.
Membranes made from binary mixtures of egg sphingomyelin (ESM) and cholesterol were investigated using conventional and saturation-recovery
EPR observations of the 5-doxylstearic acid spin label (5-SASL). The effects of cholesterol on membrane order and the oxygen
transport parameter (bimolecular collision rate of molecular oxygen with the nitroxide spin label) were monitored at the depth
of the fifth carbon in fluid- and gel-phase ESM membranes. The saturation-recovery EPR discrimination by oxygen transport
(DOT) method allowed the discrimination of the liquid-ordered (l
o), liquid-disordered (l
d), and solid-ordered (s
o) phases because the bimolecular collision rates of the molecular oxygen with the nitroxide spin label differ in these phases.
Additionally, oxygen collision rates (the oxygen transport parameter) were obtained in coexisting phases without the need
for their separation, which provides information about the internal dynamics of each phase. The addition of cholesterol causes
a dramatic decrease in the oxygen transport parameter around the nitroxide moiety of 5-SASL in the l
o phase, which at 50 mol% cholesterol becomes ∼5 times smaller than in the pure ESM membrane in the l
d phase, and ∼2 times smaller than in the pure ESM membrane in the s
o phase. The overall change in the oxygen transport parameter is as large as ∼20-fold. Conventional EPR spectra show that 5-SASL
is maximally immobilized at the phase boundary between regions with coexisting l
d and l
o phases or s
o and l
o phases and the region with a single l
o phase. The obtained results all
owed for the construction of a phase diagram for the ESM-cholesterol membrane. 相似文献
38.
Bojan Kozlev?ar Ivan Leban Saša Petri?ek Jan Reedijk 《Inorganica chimica acta》2004,357(14):4220-4230
A series of compounds of formula [{Cu2(OOCCmH2m + 1)4(urea)}2] (m=5-11) have been characterized. X-ray structure analysis for the hexanoate compound reveals a new type of tetranuclear dicopper(II) tetracarboxylate, where the central coordination sphere in [{Cu2(OOCC5H11)4(urea)}2] is composed of two dinuclear dicopper tetracarboxylates, connected via two inter-dinuclear Cu-O coordination bonds at a distance 2.222(2) Å through the apical positions of two dimers. Urea molecules (Cu-O 2.114(2) Å) occupy both outside apical positions of the resulting tetranuclear units. A strong antiferromagnetic behaviour has been shown for [{Cu2(OOCC5H11)4(urea)}2] (−2J=261.4(4) cm−1), and compared with related isolated dinuclear and polymeric hexanoate compounds [Cu2(OOCC5H11)4(urea)2], [Cu2(OOCC5H11)4]n, respectively. Only small differences in the magnetic susceptibility have been found, while EPR spectroscopy showed significantly different results for all three hexanoate compounds, also with the dicopper tetracarboxylate central core and square-pyramidal CuO4O chromophores. A solid-to-solid phase transition for [{Cu2(OOCC5H11)4(urea)}2] was observed by magnetic measurement and analysed for the whole series [{Cu2(OOCCmH2m + 1)4(urea)}2] by TG, DTA, and variable temperature XRD studies. 相似文献
39.
The functional state of the Photosystem (PS) II complex in Arabidopsis psbR T-DNA insertion mutant was studied. The ΔPsbR thylakoids showed about 34% less oxygen evolution than WT, which correlates with the amounts of PSII estimated from YDox radical EPR signal. The increased time constant of the slow phase of flash fluorescence (FF)-relaxation and upshift in the peak position of the main TL-bands, both in the presence and in the absence of DCMU, confirmed that the S2QA− and S2QB− charge recombinations were stabilized in ΔPsbR thylakoids. Furthermore, the higher amount of dark oxidized Cyt-b559 and the increased proportion of fluorescence, which did not decay during the 100s time span of the measurement thus indicating higher amount of YD+QA− recombination, pointed to the donor side modifications in ΔPsbR. EPR measurements revealed that S1-to-S2-transition and S2-state multiline signal were not affected by mutation. The fast phase of the FF-relaxation in the absence of DCMU was significantly slowed down with concomitant decrease in the relative amplitude of this phase, indicating a modification in QA to QB electron transfer in ΔPsbR thylakoids. It is concluded that the lack of the PsbR protein modifies both the donor and the acceptor side of the PSII complex. 相似文献
40.
Direct and label‐free detection of the human growth hormone in urine by an ultrasensitive bimodal waveguide biosensor 下载免费PDF全文
Ana Belén González‐Guerrero Jesús Maldonado Stefania Dante Daniel Grajales Laura M. Lechuga 《Journal of biophotonics》2017,10(1):61-67
A label‐free interferometric transducer showing a theoretical detection limit for homogeneous sensing of 5 × 10–8 RIU, being equivalent to a protein mass coverage resolution of 2.8 fg mm–2, is used to develop a high sensitive biosensor for protein detection. The extreme sensitivity of this transducer combined with a selective bioreceptor layer enables the direct evaluation of the human growth hormone (hGH) in undiluted urine matrix in the 10 pg mL–1 range.