Strategies for functionalization of recombinant spider silk

The use of silk-based materials for medical and biotechnological applications has been investigated for many years, with particular progress the last fifteen years. Extensive research has been conducted on silk derived from the silkworm Bombyx mori, but lately the evolvement in recombinant production has made mimics of spider silk proteins increasingly available. Revealed characteristics of silk such as biocompatibility, biodegradability and mechanical strength are features highly desirable in materials for medical purpose. This, in combination with techniques for functionalization (addition of new functions), incentivize further development of silk into highly sophisticated materials useful for advanced applications. The main objective of this thesis has been to investigate novel strategies for functionalization of the recombinant spider silk protein 4RepCT. Two distinct approaches were used, coating and genetic fusion. We showed that coating of silk with polyelectrolytes could be employed to make the fibers electrically conductive as well as fluorescent. Parameters affecting the coating efficiency were investigated, and pH was shown to play an important role. Genetic engineering was employed to fuse 4RepCT with moderately sized protein domains with inherent binding affinities for IgG, albumin and biotin, respectively. We found that the designed silk fusion proteins could self-assemble into silk-like fibers with preserved affinity of the added domains to bind their intended targets. Moreover, we could also demonstrate a general principle for presentation of biomolecules on IgG-binding spider silk by applying a two-step procedure, exemplified by presentation of VEGF via an anti-VEGF antibody bound to IgG-binding silk. We also showed a proof-of-principle for 4RepCT materials with catalytic activity by genetic linkage of an enzyme. To investigate potential use of other heterologous hosts for increased production of functionalized silk fusion proteins, the methylotrophic yeast Pichia pastoris was evaluated. We demonstrated expression and secretion of an IgG-binding silk fusion protein in P. pastoris, although the protein was subjected to degradation as well as glycosylation

CMBPol Mission Concept Study: Foreground Science Knowledge and Prospects

We report on our knowledge of Galactic foregrounds, as well as on how a CMB satellite mission aiming at detecting a primordial B-mode signal (CMBPol) will contribute to improving it. We review the observational and analysis techniques used to constrain the structure of the Galactic magnetic field, whose presence is responsible for the polarization of Galactic emissions. Although our current understanding of the magnetized interstellar medium is somewhat limited, dramatic improvements in our knowledge of its properties are expected by the time CMBPol flies. Thanks to high resolution and high sensitivity instruments observing the whole sky at frequencies between 30 GHz and 850 GHz, CMBPol will not only improve this picture by observing the synchrotron emission from our galaxy, but also help constrain dust models. Polarized emission from interstellar dust indeed dominates over any other signal in CMBPol's highest frequency channels. Observations at these wavelengths, combined with ground-based studies of starlight polarization, will therefore enable us to improve our understanding of dust properties and of the mechanism(s) responsible for the alignment of dust grains with the Galactic magnetic field. CMBPol will also shed new light on observations that are presently not well understood. Morphological studies of anomalous dust and synchrotron emissions will indeed constrain their natures and properties, while searching for fluctuations in the emission from heliospheric dust will test our understanding of the circumheliospheric interstellar medium. Finally, acquiring more information on the properties of extra-Galactic sources will be necessary in order to maximize the cosmological constraints extracted from CMBPol's observations of CMB lensing. (abridged)Comment: 43 pages, 7 figures, 2 table

Constraining models of the large scale Galactic magnetic field with WMAP5 polarization data and extragalactic Rotation Measure sources

We introduce a method to quantify the quality-of-fit between data and observables depending on the large scale Galactic magnetic field. We combine WMAP5 polarized synchrotron data and Rotation Measures of extragalactic sources in a joint analysis to obtain best fit parameters and confidence levels for GMF models common in the literature. None of the existing models provide a good fit in both the disk and halo regions, and in many instances best-fit parameters are quite different than the original values. We note that probing a very large parameter space is necessary to avoid false likelihood maxima. The thermal and relativistic electron densities are critical for determining the GMF from the observables but they are not well constrained. We show that some characteristics of the electron densities can already be constrained using our method and with future data it may be possible to carry out a self-consistent analysis in which models of the GMF and electron densities are simultaneously optimized.Comment: 27 pages, 13 figures. Accepted for publication in JCAP; arXiv version updated to include minor revision

Foreground Science Knowledge and Prospects

Detecting “B‐mode” (i.e., divergence free) polarization in the Cosmic Microwave Background (CMB) would open a new window on the very early Universe. However, the polarized microwave sky is dominated by polarized Galactic dust and synchrotron emissions, which may hinder our ability to test inflationary predictions. In this paper, we report on our knowledge of these “Galactic foregrounds,” as well as on how a CMB satellite mission aiming at detecting a primordial B‐mode signal (“CMBPol”) will contribute to improving it. We review the observational and analysis techniques used to constrain the structure of the Galactic magnetic field, whose presence is responsible for the polarization of Galactic emissions. Although our current understanding of the magnetized interstellar medium is somewhat limited, dramatic improvements in our knowledge of its properties are expected by the time CMBPol flies. Thanks to high resolution and high sensitivity instruments observing the whole sky at frequencies between 30 GHz and 850 GHz, CMBPol will not only improve this picture by observing the synchrotron emission from our galaxy, but also help constrain dust models. Polarized emission form interstellar dust indeed dominates over any other signal in CMBol’s highest frequency channels. Observations at these wavelengths, combined with ground‐based studies of starlight polarization, will therefore enable us to improve our understanding of dust properties and of the mechanism(s) responsible for the alignment of dust grains with the Galactic magnetic field. CMBPol will also shed new light on observations that are presently not well understood. Morphological studies of anomalous dust and synchrotron emissions will indeed constrain their natures and properties, while searching for fluctuations in the emission from heliospheric dust will test our understanding of the circumheliospheric interstellar medium. Finally, acquiring more information on the properties of extra‐Galactic sources will be necessary in order to maximaize the cosmological constrainsts extracted from CMBPol’s observations of CMB lensing

EMERALD and EMIT—worldwide computer aided education and training packages in medical physics

This paper describes the development of two web based education and training packages EMERALD and EMIT designed to meet the training needs of professional medical physicists. The program has been developed over a number of years by collaboration between hospitals and universities across Europe. The program concentrates on assisting competence development in five initial areas: diagnostic radiology; nuclear medicine; magnetic resonance tomography; ultrasound; and radiotherapy. Each of the topic areas includes around 50 training tasks in five hypertext workbooks, supplemented by a topical image database. The training materials have been extensively refereed during the development phase and are now in use in 65 countries across the globe. Initial evaluation has shown that the material enhances the training experience and produces a more consistent output