| 1. |
- Walker, DA, et al.
(författare)
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Spatial and temporal patterns of greenness on the Yamal Peninsula, Russia : interactions of ecological and social factors affecting the Arctic normalized difference vegetation index
- 2009
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 4:4, s. 045004-
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Forskningsöversikt (refereegranskat)abstract
- The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia. We assess the effects of climate change, gas-field development, reindeer grazing and permafrost degradation. In contrast to the case for Arctic North America, there has not been a significant trend in summer temperature or NDVI, and much of the pattern of NDVI in this region is due to disturbances. There has been a 37% change in early-summer coastal sea-ice concentration, a 4% increase in summer land temperatures and a 7% change in the average time-integrated NDVI over the length of the satellite observations. Gas-field infrastructure is not currently extensive enough to affect regional NDVI patterns. The effect of reindeer is difficult to quantitatively assess because of the lack of control areas where reindeer are excluded. Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing. We present a diagram that summarizes the social and ecological factors that influence Arctic NDVI. The NDVI should be viewed as a powerful monitoring tool that integrates the cumulative effect of a multitude of factors affecting Arctic land-cover change.
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| 2. |
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| 3. |
- Fedorov, V. A., et al.
(författare)
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Update on Performance Analysis of Different Computational Architectures : Molecular Dynamics in Application to Protein-Protein Interactions
- 2020
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Ingår i: Supercomputing Frontiers and Innovations. - : South Ural State University, Publishing Center. - 2409-6008 .- 2313-8734. ; 7:4, s. 62-67
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics has proved itself as a powerful computer simulation method to study dynamics, conformational changes, and interactions of biological macromolecules and their complexes. In order to achieve the best performance and efficiency, it is crucial to benchmark various hardware platforms for the simulations of realistic biomolecular systems with different size and timescale. Here, we compare performance and scalability of a number of commercially available computing architectures using all-atom and coarse-grained molecular dynamics simulations of water and the Ndc80-microtubule protein complex in the GROMACS-2019.4 package. We report typical single-node performance of various combinations of modern CPUs and GPUs, as well as multiple-node performance of the “Lomonosov-2” supercomputer. These data can be used as the practical guidelines for choosing optimal hardware for molecular dynamics simulations.
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| 4. |
- Gołowicz, D., et al.
(författare)
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Fast time-resolved NMR with non-uniform sampling
- 2020
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Ingår i: Progress in Nuclear Magnetic Resonance Spectroscopy. - : Elsevier BV. - 0079-6565. ; 116, s. 40-55
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Tidskriftsartikel (refereegranskat)abstract
- NMR spectroscopy is a versatile tool for studying time-dependent processes: chemical reactions, phase transitions or macromolecular structure changes. However, time-resolved NMR is usually based on the simplest among available techniques – one-dimensional spectra serving as “snapshots” of the studied process. One of the reasons is that multidimensional experiments are very time-expensive due to costly sampling of evolution time space. In this review we summarize efforts to alleviate the problem of limited applicability of multidimensional NMR in time-resolved studies. We focus on techniques based on sparse or non-uniform sampling (NUS), which lead to experimental time reduction by omitting a significant part of the data during measurement and reconstructing it mathematically, adopting certain assumptions about the spectrum. NUS spectra are faster to acquire than conventional ones and thus better suited to the role of “snapshots”, but still suffer from non-stationarity of the signal i.e. amplitude and frequency variations within a dataset. We discuss in detail how these instabilities affect the spectra, and what are the optimal ways of sampling the non-stationary FID signal. Finally, we discuss related areas of NMR where serial experiments are exploited and how they can benefit from the same NUS-based approaches. © 2019 Elsevier B.V.
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| 5. |
- Jaravine, Victor, 1966, et al.
(författare)
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Hyper-dimensional NMR spectroscopy with nonlinear sampling
- 2008
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Ingår i: Journal of the American Chemical Society. ; 130:12, s. 3927-3936
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Tidskriftsartikel (refereegranskat)abstract
- An approach is described for joint interleaved recording, real-time processing, and analysis of NMR data sets. The method employs multidimensional decomposition to find common information in a set of conventional triple-resonance spectra recorded in the nonlinear sampling mode, and builds a model of hyperdimensional (HD) spectrum. While preserving sensitivity per unit of measurement time and allowing for maximal spectral resolution, the approach reduces data collection time on average by 2 orders of magnitude compared to the conventional method. The 7-10 dimensional HD spectrum, which is represented as a set of deconvoluted 1D vectors, is easy to handle and amenable for automated analysis. The method is exemplified by automated assignment for two protein systems of low and high spectral complexity: ubiquitin (globular, 8 kDa) and cyt (naturally disordered, 13 kDa). The collection and backbone assignment of the data sets are achieved in real time after approximately 1 and 10 h, respectively. The approach removes the most critical time bottlenecks in data acquisition and analysis. Thus, it can significantly increase the value of NMR spectroscopy in structural biology, for example, in high-throughput structural genomics applications.
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| 6. |
- Karamanos, T. K., et al.
(författare)
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A Population Shift between Sparsely Populated Folding Intermediates Determines Amyloidogenicity
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 138:19, s. 6271-6280
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Tidskriftsartikel (refereegranskat)abstract
- The balance between protein folding and misfolding is a crucial determinant of amyloid assembly. Transient intermediates that are sparsely populated during protein folding have been identified as key players in amyloid aggregation. However, due to their ephemeral nature, structural characterization of these species remains challenging. Here, using the power of nonuniformly sampled NMR methods we investigate the folding pathway of amyloidogenic and nonamyloidogenic variants of beta(2)-microglobulin (beta(2)m) in atomic detail. Despite folding via common intermediate states, we show that the decreased population of the aggregation-prone I-Trans state and population of a less stable, more dynamic species ablate amyloid formation by increasing the energy barrier for amyloid assembly. The results show that subtle changes in conformational dynamics can have a dramatic effect in determining whether a protein is amyloidogenic, without perturbation of the mechanism of protein folding.
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| 7. |
- Tikole, S., et al.
(författare)
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Effects of NMR Spectral Resolution on Protein Structure Calculation
- 2013
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- Adequate digital resolution and signal sensitivity are two critical factors for protein structure determinations by solution NMR spectroscopy. The prime objective for obtaining high digital resolution is to resolve peak overlap, especially in NOESY spectra with thousands of signals where the signal analysis needs to be performed on a large scale. Achieving maximum digital resolution is usually limited by the practically available measurement time. We developed a method utilizing non-uniform sampling for balancing digital resolution and signal sensitivity, and performed a large-scale analysis of the effect of the digital resolution on the accuracy of the resulting protein structures. Structure calculations were performed as a function of digital resolution for about 400 proteins with molecular sizes ranging between 5 and 33 kDa. The structural accuracy was assessed by atomic coordinate RMSD values from the reference structures of the proteins. In addition, we monitored also the number of assigned NOESY cross peaks, the average signal sensitivity, and the chemical shift spectral overlap. We show that high resolution is equally important for proteins of every molecular size. The chemical shift spectral overlap depends strongly on the corresponding spectral digital resolution. Thus, knowing the extent of overlap can be a predictor of the resulting structural accuracy. Our results show that for every molecular size a minimal digital resolution, corresponding to the natural linewidth, needs to be achieved for obtaining the highest accuracy possible for the given protein size using state-of-the-art automated NOESY assignment and structure calculation methods.
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