6 research outputs found
The potential role of strategic environmental assessment (SEA) in the development of sustainable energy policies, plans and programmes for Ghana
Ghana's Vision 2020 and the 1990 energy crises have influenced energy sector
policy. plan and programme reforms which in turn have affected development
actions. Since these strategic level development decisions have ecological, economic
and social ramifications, Strategic Environmental Assessment (SEA) has been seen
as an effective tool for aligning energy sector policies, plans and programmes with
sustainable development principles.
In formulating a theoretical perspective for the study, the two overarching theories,
which framed the research, were ecological rationality and institutions. Flowing
from these theories, the concepts of environmentalism, sustainable development,
SEA and energy policies. plans and programmes have been discussed within the
context of the West, Africa and Ghana. By the application of factor analysis. multiple
regression, path analysis, partial regression, reliability models and tests of proportion
(chi-square) in a quantitative analysis, the study tested key hypotheses and computed
reliability and validity coefficients where appropriate.
The study found that although energy sector SEA in Ghana is essential for promoting
sustainable energy policies, plans and programmes, it is not a sufficient condition for
the implementation of effective sustainable energy policies, plans and programmes
without the complement of other sector SEAs and constantly improving overall legal,
social, political, economic and institutional frameworks for Environmental Impact
Assessment (EIA) and SEA. The study confirms that context and philosophical
convergence provide a common denominator for designing sustainable energy
policies, plans and programmes across institutions in Ghana. Furthermore. the study
observed that although hierarchically structured institutions such as Ghana' s National
Development Planning Commission offers the best opportunity for the integration of
SEA into sectoraI policies, plans and programmes, less hierarchical institutions such
as Environmental Protection Agency (EPA) provided a plausible and tangible
framework for a joint action and implementation on the basis of equal partnership,
cooperation and participation. Within the West Africa sub-region, common needs
and mutual benefits, for programmes such as the West Africa Gas Pipeline Project,
provided a rallying ground for a common environmental. economic and energy
policy
Imaging and 3D reconstruction of membrane protein complexes by cryo-electron microscopy and single particle analysis
Cryo-electron microscopy (cryo-EM) in combination with single particle image processing and volume reconstruction is a powerful technology to obtain medium-resolution structures of large protein complexes, which are extremely difficult to crystallize and not amenable to NMR studies due to size limitation. Depending on the stability and stiffness as well as on the symmetry of the complex, three-dimensional reconstructions at a resolution of 10-30 ˚ can be achieved. In this range of resolution, we may not be able to answer A chemical questions at the level of atomic interactions, but we can gain detailed insight into the macromolecular architecture of large multi-subunit complexes and their mechanisms of action. In this thesis, several prevalently large membrane protein complexes of great physiological importance were examined by various electron microscopy techniques and single particle image analysis. The core part of my work consists in the imaging of a mammalian V-ATPase, frozen-hydrated in amorphous ice and of the completion of the first volume reconstruction of this type of enzyme, derived from cryo-EM images. This ubiquitous rotary motor is essential in every eukaryotic cell and is of high medical importance due to its implication in various diseases such as osteoporosis, skeletal cancer and kidney disorders. My contribution to the second and third paper concerns the volume reconstruction of two bacterial outer membrane pore complexes from cryo-EM images recorded by my colleague Mohamed Chami. PulD from Klebsiella oxytoca constitutes a massive translocating pore capable of transporting a fully folded cell surface protein PulA through the membrane. It is part of the Type II secretion system, which is common for Gram-negative bacteria. The second volume regards ClyA, a pore-forming heamolytic toxin of virulent Escherichia coli and Salmonella enterica strains that kill target cells by inserting pores into their membranes. To the last two papers, I contributed with cryo-negative stain imaging of the cell division protein DivIVA from Bacillus subtilis and with image processing of the micrographs displaying the siderophore receptor FrpB from Neisseria meningitidis
JPL entry vehicle design computer program users' manual
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Structure determination of membrane proteins by electron crystallography
A fundamental principle of life is the separation of environments into different compartments.
Prokaryotes shield their interior from the environment by a plasma membrane
and in some cases also by a cell wall. Eukaryotes refine this compartmentalization
by building different organelles for different parts of the cell metabolism. Nevertheless,
these different compartments are dependent on each other and are interconnected
by membrane proteins that transport specific nutrients, hormones, ions, water and
waste products across the membrane and facilitate signal transmission between different
compartments. Understanding the structure and function of membrane proteins
can therefore allow an enormous insight into the regulation of different metabolic pathways.
The electron microscope (EM) proved itself a great tool for studying membrane proteins,
offering the unique opportunity to image membrane proteins within a lipid bilayer
as close to the natural conditions as possible. Processing of images acquired by an electron
microscope poses a challenging task for both scientist and processing hardware.
Newly developed and optimized algorithms are needed to improve the image processing
to a level that allows atomic resolution to be achieved regularly.
Membrane proteins pose a difficult challenge for a structural biologist. To crystallize
membrane proteins into well ordered two dimensional (2D) or three dimensional (3D)
crystals is one of the most important prerequisites for structural analysis at the atomic
level, yet membrane proteins are notoriously difficult to crystallize.
One exception may be bacteriorhodopsin, which forms near-perfect crystals already
in its native membrane. This may explain the fact that the first 2D electron crystallographic
structure determined at 7 Å resolution by Henderson and Unwin[20][43] in
1975 was the structure of bacteriorhodopsin. In 1990 the structure of Br was determined
to atomic resolution by Henderson et al.[19], being the first atomic structure of
a membrane protein. The structure determination of Br was also the starting point
for the mrc program suite, which is widely used at the moment in the, albeit small,
2D electron crystallography community. Using the mrc software Kühlbrandt et al.[26]
solved the structure of the light-harvesting chlorophyll a/b-protein complex in 1994.
For recording the images they used the spot scan technique developed by Downing in
1991[9].
The first aquaporin water channel determined was aquaporin 1, resolved by Walz et
al. in 1997[45] at 6 Å resolution, and subsequently solved to atomic resolution by
Murata et al. in 2000[29]. Recently, several more aquaporin structures were determined
by 2D electron crystallographic methods, aquaporin-0 (AQP0) by Gonen et al. in
2004[14] at 3 Å and in 2005[13] at 1.9 Å and aquaporin-4 (AQP4) by Hiroaki et al.
in 2006[22]. Interestingly, AQP4 shows exactly the same monomer arrangement as
SoPIP2;1. The recent publications show that the trend goes from recording solely
images to the recording of diffraction data in combination with images or even to
recording diffraction data exclusively, and then using methods developed for x-ray
crystallography to obtain the phase information.
Given the fact that the software available for processing of 2D electron diffraction patterns
is less evolved than the one for processing images, and given this new development
of increased usage of diffraction patterns, it only makes sense to focus on implementing
new and improved programs for 2D electron diffraction processing.
In this work I would like to present the advances I achieved in the structural determination
of aquaporin 2, as well as my contribution to other projects, in particular the
structural investigations of SoPIP2;1 and KdgM. I will also explain the modified sample
preparation methods which made data recording at high tilt angles more reliable
and achieved an improvement in resolution of the measured data.
A second, equally important and detailed part of my thesis is the work invested in
improving and extending the image processing to a point where a user, not adept
in programming in several languages, can use it and produce good results. For this
I improved the functionality and performance at several points, including a strong
emphasis on user friendliness and ease of maintenance