Influence of subunit structure on the oligomerization state of light harvesting complexes: a free energy calculation study

Light harvesting complexes 2 (LH2) from Rhodospirillum (Rs.) molischianum and Rhodopseudomonas (Rps.) acidophila form ring complexes out of eight or nine identical subunits, respectively. Here, we investigate computationally what factors govern the different ring sizes. Starting from the crystal structure geometries, we embed two subunits of each species into their native lipid-bilayer/water environment. Using molecular dynamics simulations with umbrella sampling and steered molecular dynamics, we probe the free energy profiles along two reaction coordinates, the angle and the distance between two subunits. We find that two subunits prefer to arrange at distinctly different angles, depending on the species, at about 42.5 deg for Rs. molischianum and at about 38.5 deg for Rps. acidophila, which is likely to be an important factor contributing to the assembly into different ring sizes. Our calculations suggest a key role of surface contacts within the transmembrane domain in constraining these angles, whereas the strongest interactions stabilizing the subunit dimers are found in the C-, and to a lesser extent, N-terminal domains. The presented computational approach provides a promising starting point to investigate the factors contributing to the assembly of protein complexes, in particular if combined with modeling of genetic variants.Comment: 28 pages, 7 figures, LaTeX2e - requires elsart.cls (included), submitted to Chemical Physic

The native architecture of a photosynthetic membrane

In photosynthesis, the harvesting of solar energy and its subsequent conversion into a stable charge separation are dependent upon an interconnected macromolecular network of membrane-associated chlorophyll–protein complexes. Although the detailed structure of each complex has been determined, the size and organization of this network are unknown. Here we show the use of atomic force microscopy to directly reveal a native bacterial photosynthetic membrane. This first view of any multi-component membrane shows the relative positions and associations of the photosynthetic complexes and reveals crucial new features of the organization of the network: we found that the membrane is divided into specialized domains each with a different network organization and in which one type of complex predominates. Two types of organization were found for the peripheral light-harvesting LH2 complex. In the first, groups of 10–20 molecules of LH2 form light-capture domains that interconnect linear arrays of dimers of core reaction centre (RC)–light-harvesting 1 (RC–LH1–PufX) complexes; in the second they were found outside these arrays in larger clusters. The LH1 complex is ideally positioned to function as an energy collection hub, temporarily storing it before transfer to the RC where photochemistry occurs: the elegant economy of the photosynthetic membrane is demonstrated by the close packing of these linear arrays, which are often only separated by narrow 'energy conduits' of LH2 just two or three complexes wide

Exchange Risk Hedging When Carrying Out Exchange Operations

The article analyses the problems caused by the establishment of a floating market exchange rate regime in the Republic of Belarus. The liberalization of the currency market makes it necessary to use the strategies of risk hedging due to unfavorable changes in the exchange rate dynamics

The role of the state in the formation of a qualitative level of human capital in the Republic of Belarus

The article considers the theoretical aspects of the "human resource" concept, analyzes the approach to the formation of the human capital of the labour resources, the role of the state in the formation of the human capital of the workers

Ecologization of the Economy: Foreign Aspect

The article considers the experience of developed countries in the field of ecologization the economy and specific actions aimed at protecting the environment, the results of a successful environmental policy pursued by the European Union in recent years, the influence of environmental taxation to stimulate work with alternative energy sources

Friedrich Nietzsche’s poetry in the context of the culture at the turn of the XIX–XX centuries

This article examines the poetic legacy of Friedrich Nietzsche in the context of the culture of the turn of the nineteenth and twentieth centuries. Lyric poetry reacts quickly and vividly to the changes in the cultural consciousness of the era. With the help of literary and culturological analysis it is shown how the main worldview concepts of the fin de siècle are reflected in the Nietzsche’s poetry. It is presented both as a paraphrase to his philosophy and as an independent creative element that captured the «spirit of the time».В статье рассматривается поэтическое наследие Фридриха Ницше в контексте культуры рубежа XIX–XX веков. Лирическая поэзия быстро и ярко реагирует на изменения в культурном сознании эпохи. При помощи литературоведческого и культурологического анализа показано, как основные мировоззренческие концепты fin de siècle нашли свое отражение в поэзии Ницше. Она представляется и как парафраз к его философии, и как самостоятельная творческий элемент, уловивший «дух времени»

The role of the state in the formation of a qualitative level of human capital in the Republic of Belarus

The article considers the theoretical aspects of the "human resource" concept, analyzes the approach to the formation of the human capital of the labour resources, the role of the state in the formation of the human capital of the workers

Exchange Risk Hedging When Carrying Out Exchange Operations

The article analyses the problems caused by the establishment of a floating market exchange rate regime in the Republic of Belarus. The liberalization of the currency market makes it necessary to use the strategies of risk hedging due to unfavorable changes in the exchange rate dynamics

Overall energy conversion efficiency of a photosynthetic vesicle

The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytbc1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82. ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%–5% of full sunlight is calculated to be 0.12–0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination

Self-assembled monolayer of light-harvesting core complexes of photosynthetic bacteria on an amino-terminated ITO electrode

Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopseudomonas palustris were successfully self-assembled on an ITO electrode modified with 3-aminopropyltriethoxysilane. Near infra-red (NIR) absorption, fluorescence, and IR spectra of these LH1-RC complexes indicated that these LH1-RC complexes on the electrode were stable on the electrode. An efficient energy transfer and photocurrent responses of these LH1-RC complexes on the electrode were observed upon illumination of the LH1 complex at 880 nm