Structural Analysis of Respirasomes in Electron Transfer Pathway of Acidithiobacillus ferrooxidans: A Computer-Aided Molecular Designing Study

Acidithiobacillus ferrooxidans obtains its metabolic energy by reducing extracellular ferrous iron with either downhill or uphill electron transfer pathway. The downhill electron transfer pathway has been substantially explored in recent years to underpin the mechanism of iron respiration but, there exists a wide gap in our present understanding on how these proteins are organized as a supercomplex and what sort of atomic level interactions governs their stability in the iron respiratory chain. In the present study, we aimed at unraveling the structural basis of supermolecular association of respirasomes using protein threading, protein-protein docking, and molecular dynamics (MD) simulation protocols. Our results revealed that Phe312 of outer membrane cytochrome c plays a crucial role in diffusing electrons from heme C group to Asp73 of rusticyanin. In line with the previous experimental results, His143 of rusticyanin was found to have a stable interaction with Glu121 of periplasmic cytochrome c4. Cytochrome c4 interacts with subunit B of cytochrome c oxidase through Lys146 and Thr148 of the conserved hydrophobic/aromatic motif 145-WKWTFSY-151 to attain stability during simulation. Phe468 of cytochrome c oxidase was found indispensable for stabilizing heme aa3 during MD simulation. Taken together, we conclude that the molecular interactions of charged and hydrophobic amino acids present on the surface of each respirasome form a hypothetical electron wire in the iron respiratory supercomplex of A. ferrooxidans.

Heterocyclic Aromatic Amines Heterocomplexation with Biologically Active Aromatic Compounds and Its Possible Role in Chemoprevention

Food-borne heterocyclic aromatic amines (HCAs) are known mutagens and carcinogens present especially in Western population diet, which contains large amount of meat and its products. HCAs are capable of interacting with DNA directly through the formation of covalent adducts, however this process requires biological activation in liver, mainly by cytochrome P450 enzymes. This process may produce mutations and in consequence may contribute to the development of cancer. However, there are many studies showing that several biologically active aromatic compounds (BACs) may protect against genotoxic effects of HCAs. Direct interactions and noncovalent heterocomplexes formation may be one of the most important mechanisms of such protection. This work describes several BACs present in human diet, which are capable of molecular complexes formation with HCAs and protect cells as well as whole organisms against HCAs action.

The Skeletal Muscle Impedancemetric Characteristics as a Marker for Detection of Functional State of Organism

Previously it has been shown that cell hydration is a universal and extrasensitive marker for different environmental mediums and functional state of tissue and organism. The comparative study of cell hydration of different organs (brain cortex, liver, and skeletal muscle) at various experimental conditions (microstress, pathology, and different poisons) was realized. It was shown that among tissues of different organs muscle hydration is more sensitive to any change of functional state of organism and environmental medium. The study of correlation between tissue muscle hydration and double-frequency measurement impedance method indicated that the differences between muscle reactive conductivity measured at high frequency (HF) and low frequency (LF) could be an adequate marker for detection of muscle hydration. The animal poisoning, stress, and pathology-induced tissue hydration were accompanied by increase in . The observed close correlation between time-dependent tissue hydration and in different environmental mediums can be a marker for detection of postmortal period as well as for characterizing environmental medium of the corpse.

Incoherent Neutron Spin-Echo Spectroscopy as an Option to Study Long-Range Lipid Diffusion

Diffusion is the fundamental mechanism for lipids and other molecules to move in a membrane. It is an important process to consider in modelling the formation of membrane structures, such as rafts. Lipid diffusion is mainly studied by two different techniques: incoherent neutron scattering and fluorescence microscopy. Both techniques access distinctly different length scales. While neutron scattering measures diffusion over about 3 lipid diameters, microscopic techniques access motions of lipids over micrometer distances. The diffusion constants which are determined by these two methods often differ by about an order of magnitude, with the neutrons usually seeing a faster lipid diffusion. Different theories are used to describe lipid diffusion in the two experiments. In order to close the “gap” between these two techniques, we propose to study lipid diffusion at mesoscopic length scales using a neutron spin-echo (NSE) spectrometer. We have conducted an experiment in highly oriented, solid supported lipid bilayers to prove the feasibility of performing incoherent NSE on biological samples. Lateral lipid diffusion was measured in a fluid phase model membrane system at a length scale of 12 Å. Using the high-energy resolution of the NSE technique, we find evidence for two dynamic processes.

Fragmentation of Plasmid DNA Produced by Gamma Radiation: A Theoretical Approach

Breaks in DNA, resulting in fragmented parts, can be produced by ionizing radiation which, in turn, is the starting point in the search for novel physical aspects of DNA strands. Double-strand breaks in particular cause disruption of the DNA strand, splitting it into several fragments. In order to study effects produced by radiation in plasmid DNA, a new simple mechanical model for this molecule is proposed. In this model, a Morse-like potential and a high-LET component are used to describe the DNA-radiation interaction. Two power laws, used to fit results of the model, suggest that, firstly, distribution of fragment size is nonextensive and, secondly, that a transition phase is present in the DNA fragment distribution pattern.

Effect of Anderson Localization on Auger Destruction of DNA

The effect of Anderson localization in DNA on the Auger destruction by the Coulombic explosion at ionized radiation has been theoretically discussed in the present work. The theory of Auger destruction of DNA has been modified taking into account the localized and delocalized electron states in DNA owing to the correlated disorder in a sequence of nucleotides. According to the modified theoretical model of Auger destruction, the dominant ratio of delocalized states to localized states in exon compared to intron results in stronger radiation resistance of exons to ionized irradiation causing the Auger-cascade process than the radiation resistance of introns.

Particle Adhesion Measurements on Insect Wing Membranes Using Atomic Force Microscopy

Many insects have evolved refined self-cleaning membrane structuring to contend with an environment that presents a range of potential contaminates. Contamination has the potential to reduce or interfere with the primary functioning of the wing membrane or affect other wing cuticle properties, (for example, antireflection). Insects will typically encounter a variety of air-borne contaminants which include plant matter and soil fragments. Insects with relatively long or large wings may be especially susceptible to fouling due to the high-wing surface area and reduced ability to clean their extremities. In this study we have investigated the adhesion of particles (pollens and hydrophilic silica spheres) to wing membranes of the super/hydrophobic cicada (Thopha sessiliba), butterfly (Eurema hecabe), and the hydrophilic wing of flower wasp (Scolia soror). The adhesional forces with both hydrophobic insects was significantly lower for all particle types than the hydrophilic insect species studied.

Multiple Orientation Circuits Converging on the Pd7 Cells in Tritonia diomedea

Magnetoreception is a sophisticated orientation mechanism, involving a magnetoreceptor connected to the nervous system with signal amplification. The mollusk Tritonia diomedea is a good model to investigate the behavioral and neural responses to the magnetic field. The mollusk inhibits all unnecessary activities and focuses on an available cue during orientation. Although Pd7 cells are inhibited by magnetic pathway, it was excited by another stimulus, water streams plus food odor. Two sensory pathways connected to Pd7 through the same or different circuits were tested. The action potential activity through Pd7 was compared in these different stimulations. The changes in Pd7 activity indicate a response of enhanced electrical activity to water streams plus food odor stimulus, and Pd7 activity can be excited by at least one of these stimuli. These results indicate an inverse relationship between magnetic orientation and feeding.

Hydration Water Freezing in Single Supported Lipid Bilayers

We present a high-temperature and high-energy resolution neutron scattering investigation of hydration water freezing in single supported lipid bilayers. Single supported lipid bilayers provide a well-defined biological interface to study hydration water dynamics and coupling to membrane degrees of freedom. Nanosecond molecular motions of membrane and hydration water were studied in the temperature range 240 K < T < 290 K in slow heating and cooling cycles using coherent and incoherent elastic neutron scattering on a backscattering spectrometer. Several freezing and melting transitions were observed. From the length scale dependence of the elastic scattering, these transitions could be assigned to freezing and melting of hydration water dynamics, diffusive lipid, and lipid acyl-tail dynamics. Coupling was investigated by comparing the different freezing and melting temperatures. While it is often speculated that membrane and hydration water dynamics are strongly coupled, we find that membrane and hydration water dynamics are at least partially decoupled in single bilayers.