Molecular Architecture of Plant Thylakoids under Physiological and Light Stress Conditions: A Study of Lipid–Light-Harvesting Complex II Model Membranes

In this study, we analyzed multibilayer lipid-protein membranes composed of the photosynthetic light-harvesting complex II (LHCII; isolated from spinach [Spinacia oleracea]) and the plant lipids monogalcatosyldiacylglycerol and digalactosyldiacylglycerol. Two types of pigment-protein complexes were analyzed: those isolated from dark-adapted leaves (LHCII) and those from leaves preilluminated with high-intensity light (LHCII-HL). The LHCII-HL complexes were found to be partially phosphorylated and contained zeaxanthin. The results of the x-ray diffraction, infrared imaging microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed that lipid-LHCII membranes assemble into planar multibilayers, in contrast with the lipid-LHCII-HL membranes, which form less ordered structures. In both systems, the protein formed supramolecular structures. In the case of LHCII-HL, these structures spanned the multibilayer membranes and were perpendicular to the membrane plane, whereas in LHCII, the structures were lamellar and within the plane of the membranes. Lamellar aggregates of LHCII-HL have been shown, by fluorescence lifetime imaging microscopy, to be particularly active in excitation energy quenching. Both types of structures were stabilized by intermolecular hydrogen bonds. We conclude that the formation of trans-layer, rivet-like structures of LHCII is an important determinant underlying the spontaneous formation and stabilization of the thylakoid grana structures, since the lamellar aggregates are well suited to dissipate excess energy upon overexcitation.     

1-Methyl-3-nitropyridine: An Efficient Oxidant of NADH in Non-enzymatic and Enzyme-mediated Processes

It is shown that NADH can be effectively oxidized by 1-methyl-3-nitropyridine in non-enzymatic and enzyme-mediated processes. Mechanistic issues of these reactions are discussed. These processes seem to contribute to the observed cytotoxicity of 1-methyl-3-nitropyridine. A key role of 1-methyl-3-nitropyridinyl radical formed in the enzyme-mediated processes is emphasized.     

Damped sinusoidal function to model acute irradiation in radiotherapy patients

In the paper, we suggest a damped sinusoidal function be used to model a regenerative response of mucosa in time after the radiotherapy treatment. The medical history of 389 RT patients irradiated within the years 1994–2000 at the Radiotherapy Department, Cancer Center, Maria Sk?odowska-Curie Memorial Institute of Oncology, Gliwice, Poland, was taken into account. In the analyzed group of patients, the number of observations of a single patient ranged from 2 to 25 (mean = 8.3, median = 8) with severity determined by use of Dische's scores from 0 to 24 (mean = 7.4, median = 7). Statistical modeling of radiation-induced mucositis was performed for five groups of patients irradiated within the following radiotherapy schedules: CAIR, CB, Manchester, CHA–CHA, and Conventional. All of the regression parameters of the assumed model, i.e. amplitude, damping coefficient, angular frequency, phase of component, and offset, estimated in the analysis were statistically significant (p-value < 0.05) for the radiotherapy schedules. The model was validated using a non-oscillatory function. Following goodness-of-fit statistics, the damped sinusoidal function fits the data better than the non-oscillatory damped function. Model curves for harmonic characteristics with confidence intervals were plotted separately for each of the RT schedules and together in a combined design. The suggested model might be helpful in the numeric evaluation of the RT toxicity in the groups of patients under analysis as it allows for practical comparisons and treatment optimization. A statistical approach is also briefly described in the paper.     

Postsynthetic Transformations of Oligodeoxynucleotides Originated at 6-Methylthio-purine Site

Abstract

New route to oligodeoxynucleotides labeled with fluorescent luminarine was explored. Regioselective oxidation of 6-methylthio-purines to 6-methylsulphoxides reactive toward pyridine was achieved. Upon UV irradiation of 6-pyridinium-purines oligonucleotide cleavage instead of phototransformation to luminarine was observed.     

RNA Modified Uridines VI: Conformations of 3-[3-(S)-Amino-3-Carboxypropyl]Uridine (acp3U) from tRNA and 1-Methyl-3-[3-(S)-Amino-3-Carboxypropyl]Pseudouridine (m1acp3Ψ) from rRNA

Abstract

The conformation of chemically synthesized acp³U is 60& 3′-endo, gauche⁺, whereas that of m¹acp³Ψ is 60& 2′-endo, gauche⁺. We conclude that the difference in conformation probably imparts important local structures to their respective tRNA and rRNA.     

The Cytotoxicity of Anti-PAI-I Oligonucleotides and Their Conjugates

Abstract

The cytotoxicity of anti-PAI-5 hexadecanucleotides (phosphodiesters and phosphorothioates) and their conjugates with lipophilic alcohols was tested in EA.hy 926 hybrid endothelial cells. Some cytotoxicity was found for cholesteryl and bornyl conjugates at concentrations higher than those used for antisense inhibition experiments.     

Linkage Maps of Lowland and Upland Tetraploid Switchgrass Ecotypes

Switchgrass (Panicum virgatum L.) is a native perennial warm season (C₄) grass that has been identified as a promising species for bioenergy research and production. Consequently, biomass yield and feedstock quality improvements are high priorities for switchgrass research. The objective of this study was to develop a switchgrass genetic linkage map using a full-sib pseudo-testcross mapping population derived from a cross between two heterozygous genotypes selected from the lowland cultivar ‘Alamo’ (AP13) and the upland cultivar ‘Summer’ (VS16). The female parent (AP13) map consists of 515 loci in 18 linkage groups (LGs) and spans 1,733 cM. The male parent (VS16) map arranges 363 loci in 17 LGs and spans 1,508 cM. No obvious cause for the lack of one LG in VS16 could be identified. Comparative analyses between the AP13 and VS16 maps showed that the two major ecotypic classes of switchgrass have highly colinear maps with similar recombination rates, suggesting that chromosomal exchange between the two ecotypes should be able to occur freely. The AP13 and VS16 maps are also highly similar with respect to marker orders and recombination levels to previously published switchgrass maps. The genetic maps will be used to identify quantitative trait loci associated with biomass and quality traits. The AP13 genotype was used for the whole genome-sequencing project and the map will thus also provide a tool for the anchoring of the switchgrass genome assembly.     

Monte carlo study of the percolation in two-dimensional polymer systems

The structure of a two-dimensional film formed by adsorbed polymer chains was studied by means of Monte Carlo simulations. The polymer chains were represented by linear sequences of lattice beads and positions of these beads were restricted to vertices of a two-dimensional square lattice. Two different Monte Carlo methods were employed to determine the properties of the model system. The first was the random sequential adsorption (RSA) and the second one was based on Monte Carlo simulations with a Verdier-Stockmayer sampling algorithm. The methodology concerning the determination of the percolation thresholds for an infinite chain system was discussed. The influence of the chain length on both thresholds was presented and discussed. It was shown that the RSA method gave considerably lower thresholds for longer chains. This behavior can be explained by a different pool of chain conformations used in the calculations in both methods under consideration.