Time filter

Source Type

Bock L.V.,Max Planck Institute for Biophysical Chemistry | Blau C.,Max Planck Institute for Biophysical Chemistry | Schroder G.F.,Julich Research Center | Schroder G.F.,Heinrich Heine University Dusseldorf | And 7 more authors.
Nature Structural and Molecular Biology | Year: 2013

During protein synthesis, tRNAs move from the ribosome's aminoacyl to peptidyl to exit sites. Here we investigate conformational motions during spontaneous translocation, using molecular dynamics simulations of 13 intermediate-translocation-state models obtained by combining Escherichia coli ribosome crystal structures with cryo-EM data. Resolving fast transitions between states, we find that tRNA motions govern the transition rates within the pre- and post-translocation states. Intersubunit rotations and L1-stalk motion exhibit fast intrinsic submicrosecond dynamics. The L1 stalk drives the tRNA from the peptidyl site and links intersubunit rotation to translocation. Displacement of tRNAs is controlled by 'sliding' and 'stepping' mechanisms involving conserved L16, L5 and L1 residues, thus ensuring binding to the ribosome despite large-scale tRNA movement. Our results complement structural data with a time axis, intrinsic transition rates and molecular forces, revealing correlated functional motions inaccessible by other means. © 2013 Nature America, Inc. All rights reserved. Source

Langley G.,Humane Society International | Austin C.P.,U.S. National Institutes of Health | Balapure A.K.,CSIR - Central Electrochemical Research Institute | Birnbaum L.S.,U.S. National Institutes of Health | And 15 more authors.
Environmental Health Perspectives | Year: 2015

Biomedical developments in the 21st century provide an unprecedented opportunity to gain a dynamic systems-level and human-specific understanding of the causes and pathophysiologies of disease. This understanding is a vital need, in view of continuing failures in health research, drug discovery, and clinical translation. The full potential of advanced approaches may not be achieved within a 20th-century conceptual framework dominated by animal models. Novel technologies are being integrated into environmental health research and are also applicable to disease research, but these advances need a new medical research and drug discovery paradigm to gain maximal benefits. We suggest a new conceptual framework that repurposes the 21st-century transition underway in toxicology. Human disease should be conceived as resulting from integrated extrinsic and intrinsic causes, with research focused on modern human-specific models to understand disease pathways at multiple biological levels that are analogous to adverse outcome pathways in toxicology. Systems biology tools should be used to integrate and interpret data about disease causation and pathophysiology. Such an approach promises progress in overcoming the current roadblocks to understanding human disease and successful drug discovery and translation. A discourse should begin now to identify and consider the many challenges and questions that need to be solved. © 2015, Public Health Services, US Dept of Health and Human Services. All rights reserved. Source

Marx U.,TissUse GmbH | Andersson T.B.,Astrazeneca | Andersson T.B.,Karolinska Institutet | Bahinski A.,Wyss Institute for Biologically Inspired Engineering | And 33 more authors.
Altex | Year: 2016

The recent advent of microphysiological systems-microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro-promises to enable a global paradigm shift in drug development. An extraordinary US government initiative and various dedicated research programs in Europe and Asia recently have led to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis will model various disease stages and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus replacing the use of laboratory animal models. Here, thirty-six experts from academia, industry and regulatory bodies present the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies as well as various national and international programs are highlighted. Finally, a roadmap into the future towards more predictive and regulatory-accepted substance testing on a global scale is outlined. Source

Wagner I.,TU Berlin | Materne E.-M.,TU Berlin | Brincker S.,TU Berlin | Sussbier U.,TU Berlin | And 9 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2013

Current in vitro and animal tests for drug development are failing to emulate the systemic organ complexity of the human body and, therefore, to accurately predict drug toxicity. In this study, we present a multi-organ-chip capable of maintaining 3D tissues derived from cell lines, primary cells and biopsies of various human organs. We designed a multi-organ-chip with co-cultures of human artificial liver microtissues and skin biopsies, each a 1/100000 of the biomass of their original human organ counterparts, and have successfully proven its long-term performance. The system supports two different culture modes: i) tissue exposed to the fluid flow, or ii) tissue shielded from the underlying fluid flow by standard Transwell® cultures. Crosstalk between the two tissues was observed in 14-day co-cultures exposed to fluid flow. Applying the same culture mode, liver microtissues showed sensitivity at different molecular levels to the toxic substance troglitazone during a 6-day exposure. Finally, an astonishingly stable long-term performance of the Transwell®-based co-cultures could be observed over a 28-day period. This mode facilitates exposure of skin at the air-liquid interface. Thus, we provide here a potential new tool for systemic substance testing. © The Royal Society of Chemistry 2013. Source

Materne E.-M.,TU Berlin | Ramme A.P.,TU Berlin | Terrasso A.P.,Institute Biologia Experimental e Tecnologica | Terrasso A.P.,New University of Lisbon | And 11 more authors.
Journal of Biotechnology | Year: 2015

Current in vitro and animal tests for drug development are failing to emulate the systemic organ complexity of the human body and, therefore, often do not accurately predict drug toxicity, leading to high attrition rates in clinical studies (. Paul et al., 2010). The phylogenetic distance between humans and laboratory animals is enormous, this affects the transferability of animal data on the efficacy of neuroprotective drugs. Therefore, many neuroprotective treatments that have shown promise in animals have not been successful when transferred to humans (. Dragunow, 2008; Gibbons and Dragunow, 2010). We present a multi-organ chip capable of maintaining 3D tissues derived from various cell sources in a combined media circuit which bridges the gap in systemic and human tests. A steady state co-culture of human artificial liver microtissues and human neurospheres exposed to fluid flow over two weeks in the multi-organ chip has successfully proven its long-term performance. Daily lactate dehydrogenase activity measurements of the medium and immunofluorescence end-point staining proved the viability of the tissues and the maintenance of differentiated cellular phenotypes. Moreover, the lactate production and glucose consumption values of the tissues cultured indicated that a stable steady-state was achieved after 6 days of co-cultivation. The neurospheres remained differentiated neurons over the two-week cultivation in the multi-organ chip, proven by qPCR and immunofluorescence of the neuronal markers βIII-tubulin and microtubule-associated protein-2. Additionally, a two-week toxicity assay with a repeated substance exposure to the neurotoxic 2,5-hexanedione in two different concentrations induced high apoptosis within the neurospheres and liver microtissues, as shown by a strong increase of lactate dehydrogenase activity in the medium. The principal finding of the exposure of the co-culture to 2,5-hexanedione was that not only toxicity profiles of two different doses could be discriminated, but also that the co-cultures were more sensitive to the substance compared to respective single-tissue cultures in the multi-organ-chip. Thus, we provide here a new in vitro tool which might be utilized to predict the safety and efficacy of substances in clinical studies more accurately in the future. © 2015 Elsevier B.V. Source

Discover hidden collaborations