ABSTRACT
The preparation of sufficient amounts of high-quality samples is still the major bottleneck for the characterization of membrane proteins by in vitro approaches. The hydrophobic nature, the requirement for complicated transport and modification pathways, and the often observed negative effects on membrane properties are intrinsic features of membrane proteins that frequently cause significant problems in overexpression studies. Establishing efficient protocols for the production of functionally folded membrane proteins is therefore a challenging task, and numerous specific characteristics have to be considered. In addition, a variety of expression systems have been developed, and choice of appropriate techniques could strongly depend on the desired target membrane proteins as well as on their intended applications. The production of membrane proteins is a highly dynamic field and new or modified approaches are frequently emerging. The review will give an overview of currently established processes for the production of functionally folded membrane proteins.
Subject(s)
Cell-Free System , Gene Expression , Membrane Proteins/isolation & purification , Animals , Humans , Hydrophobic and Hydrophilic Interactions , Insecta/cytology , Membrane Proteins/genetics , Membrane Proteins/metabolism , Molecular Structure , Protein Conformation , Protein Folding , Protein Processing, Post-Translational , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/isolation & purification , Recombinant Fusion Proteins/metabolism , Yeasts/cytology , Yeasts/physiologyABSTRACT
Speech perception is a valuable tool for the assessment of auditory (re-)habilitation of children with hearing impairments. We tested 3 groups of prelingually deaf children. For the evaluation of speech recognition abilities the test of auditory perception of speech in children (TAPS) was used. Hearing aid fitted children of a school for hard of hearing and school of the deaf (n = 12 and n = 10, respectively) and cochlear implant users (n = 12) of the same age group were tested. A positive correlation of the speech perception abilities with the aided thresholds was found. Hearing aid fitted children of the school of hard of hearing with aided thresholds between 20 and 40 dB HL including 4000 Hz showed best results. Students of the same school with aided thresholds in the range of 45 to 70 dB HL performed comparable to the lesser cochlear implant users fitted with a single channel analogue system. Hearing aid fitted students of a school for the deaf with the same degree of hearing loss and amplification showed significantly poorer results.
Subject(s)
Cochlear Implants , Deafness/rehabilitation , Hearing Aids , Speech Discrimination Tests , Speech Reception Threshold Test , Auditory Threshold , Child , Combined Modality Therapy , Deafness/etiology , Education, Special , Equipment Design , Female , Humans , MaleABSTRACT
Abstract Peat profiles from the area of the Tunguska explosion epicentre indicate significant carbon and hydrogen isotopic effects which are clearly associated with the zone of the 1908 "catastrophe", and which cannot be attributed to any known terrestrial processes. We explain them with the presence of extraterrestrial matter similar to carbonaceous chondrites or, more probably, to cometary matter. Initial data on nitrogen content and its isotope composition are consistent with the assumption of acid rainfall following the passage and explosion of the Tunguska cosmic body, as is known to have occurred during the Cretaceous-Tertiary boundary.
ABSTRACT
Abstract Geological-sedimentological (grain size, micromorphology, varve correlation) and geochemical (stable isotopes: (18)O/(16)O,(13)C/(12)C) investigations with ice-dammed lake sediments of the Dehlitz-Leipzig varved clay enable to elucidate in detail the palaeosedimentologic and palaeoclimatic conditions in the surrounding of the Elsterian Scandinavian inland-ice sheet a relatively short time before its maximum extension in Central Europe took place. For the space of time between formation of the ice-dammed glacial lake and its run-over by Scandinavian inland-ice sheet the obtained results allow to distinguish at least four evolutionary phases. Regarding the palaeosedimentologic relations in the ice-dammed glacial lake these four phases are characterized by differences in the dynamics of sediment input, suspension density within the water body and existence/absence of stagnation events with syngenetic formation of carbonates under anoxic conditions. During the formation of glacial varves the obtained data seem to support the existence of small seasonal differences which can be due to very cold, long winter- and short, cool summer periods. In this way the time of the first Elsterian glacial maximum, reflected by the varved clays, can be classified as a typical glacial climatic period.
