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Sökning: WFRF:(Murtola Teemu)

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1.
  • Abraham, Mark James, 1977-, et al. (författare)
  • GROMACS: High performance molecular simulations through multi-level parallelism from laptops to supercomputers
  • 2015
  • Ingår i: SoftwareX. - : Elsevier. - 2352-7110. ; 1-2, s. 19-25
  • Tidskriftsartikel (refereegranskat)abstract
    • GROMACS is one of the most widely used open-source and free software codes in chemistry, used primarily for dynamical simulations of biomolecules. It provides a rich set of calculation types, preparation and analysis tools. Several advanced techniques for free-energy calculations are supported. In version 5, it reaches new performance heights, through several new and enhanced parallelization algorithms. These work on every level; SIMD registers inside cores, multithreading, heterogeneous CPU–GPU acceleration, state-of-the-art 3D domain decomposition, and ensemble-level parallelization through built-in replica exchange and the separate Copernicus framework. The latest best-in-class compressed trajectory storage format is supported.
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2.
  • Assel, Melissa, et al. (författare)
  • A Four-kallikrein Panel and β-Microseminoprotein in Predicting High-grade Prostate Cancer on Biopsy : An Independent Replication from the Finnish Section of the European Randomized Study of Screening for Prostate Cancer
  • Ingår i: European Urology Focus. - : Elsevier. - 2405-4569. ; 5:4, s. 561-567
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: A panel of four kallikrein markers (total, free, and intact prostate-specific antigen [PSA] and human kallikrein-related peptidase 2 [hK2]) improves predictive accuracy for Gleason score ≥7 (high-grade) prostate cancer among men biopsied for elevated PSA. A four-kallikrein panel model was originally developed and validated by the Dutch center of the European Randomized Study of Screening for Prostate Cancer (ERSPC). The kallikrein panel is now commercially available as 4Kscore™. Objective: To assess whether these findings could be replicated among participants in the Finnish section of ERSPC (FinRSPC) and whether β-microseminoprotein (MSP), a candidate prostate cancer biomarker, adds predictive value. Design, setting, and participants: Among 4861 biopsied screening-positive participants in the first three screening rounds of FinRSPC, a case-control subset was selected that included 1632 biopsy-positive cases matched by age at biopsy to biopsy-negative controls. Outcome measurements and statistical analysis: The predictive accuracy of prespecified prediction models was compared with biopsy outcomes. Results and limitations: Among men with PSA of 4.0-25. ng/ml, 1111 had prostate cancer, 318 of whom had high-grade disease. Total PSA and age predicted high-grade cancer with an area under the curve of 0.648 (95% confidence interval [CI] 0.614-0.681) and the four-kallikrein panel increased discrimination to 0.746 (95% CI 0.717-0.774). Adding MSP to the four-kallikrein panel led to a significant (Wald test; p = 0.015) but small increase (0.003) in discrimination. Limitations include a risk of verification bias among men with PSA of 3.0-3.99. ng/ml and the absence of digital rectal examination results. Conclusions: These findings provide additional evidence that kallikrein markers can be used to inform biopsy decision-making. Further studies are needed to define the role of MSP. Patient summary: Four kallikrein markers and β-microseminoprotein in blood improve discrimination of high-grade prostate cancer at biopsy in men with elevated prostate-specific antigen. Four kallikrein markers and β-microseminoprotein (MSP) in blood improve discrimination of high-grade cancer at biopsy in men with elevated prostate-specific antigen. These kallikrein markers can be used to inform biopsy decision-making. Further studies are needed to define the role of MSP.
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  • Murtola, Teemu, et al. (författare)
  • Low density lipoprotein : structure, dynamics, and interactions of apoB-100 with lipids
  • 2011
  • Ingår i: Soft Matter. - 1744-683X .- 1744-6848. ; 7:18, s. 8135-8141
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-density lipoprotein (LDL) transports cholesterol in the bloodstream and plays an important role in the development of cardiovascular diseases, in particular atherosclerosis. Despite its importance to health, the structure of LDL is not known in detail. This is worrying since the lack of LDL's structural information makes it more difficult to understand its function. In this work, we have combined experimental and theoretical data to construct LDL models comprised of the apoB-100 protein wrapped around a lipid droplet of about 20 nm in size. The models are considered by near-atomistic multi-microsecond simulations to unravel structural as well as dynamical properties of LDL, with particular attention paid to lipids and their interactions with the protein. We find that the distribution and the ordering of the lipids in the LDL particle are rather complex. The previously proposed 2- and 3- layer models turn out to be inadequate to describe the properties of the lipid droplet. At the surface of LDL, apoB-100 is found to interact favorably with cholesterol and its esters. The interactions of apoB-100 with core molecules, in particular cholesteryl esters, are rather frequent and arise from hydrophobic amino acids interacting with the ring of cholesteryl esters, and also in part from the rather loose packing of lipids at the surface of the lipoparticle. The loose packing may foster the function of transfer proteins, which transport lipids between lipoproteins. Finally, the comparison of the several apoB-100 models in our study suggests that the properties of lipids in LDL are rather insensitive to the conformation of apoB-100. Altogether, the findings pave the way for further studies of LDL to better understand the central steps in the emergence of atherosclerosis.
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5.
  • Niemelä, Perttu S., et al. (författare)
  • Membrane proteins diffuse as dynamic complexes with lipids
  • 2010
  • Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 132:22, s. 7574-5
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe how membrane proteins diffuse laterally in the membrane plane together with the lipids surrounding them. We find a number of intriguing phenomena. The lateral displacements of the protein and the lipids are strongly correlated, as the protein and the neighboring lipids form a dynamical protein-lipid complex, consisting of approximately 50-100 lipids. The diffusion of the lipids in the complex is much slower compared to the rest of the lipids. We also find a strong directional correlation between the movements of the protein and the lipids in its vicinity. The results imply that in crowded membrane environments there are no "free" lipids, as they are all influenced by the protein structure and dynamics. Our results indicate that, in studies of cell membranes, protein and lipid dynamics have to be considered together.
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6.
  • Wennberg, Christian L., et al. (författare)
  • Direct-Space Corrections Enable Fast and Accurate Lorentz-Berthelot Combination Rule Lennard-Jones Lattice Summation
  • 2015
  • Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 11:12, s. 5737-5746
  • Tidskriftsartikel (refereegranskat)abstract
    • Long-range lattice summation techniques such as the particle-mesh Ewald (PME) algorithm for electrostatics have been revolutionary to the precision and accuracy of molecular simulations in general. Despite the performance penalty associated with lattice summation electrostatics, few biomolecular simulations today are performed without it. There are increasingly strong arguments for moving in the same direction for Lennard-Jones (LJ) interactions, and by using geometric approximations of the combination rules in reciprocal space, we have been able to make a very high-performance implementation available in GROMACS. Here, we present a new way to correct for these approximations to achieve exact treatment of Lorentz-Berthelot combination rules within the cutoff, and only a very small approximation error remains outside the cutoff (a part that would be completely ignored without LJ-PME). This not only improves accuracy by almost an order of magnitude but also achieves absolute biomolecular simulation performance that is an order of magnitude faster than any other available lattice summation technique for LJ interactions. The implementation includes both CPU and GPU acceleration, and its combination with improved scaling LJ-PME simulations now provides performance close to the truncated potential methods in GROMACS but with much higher accuracy.
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8.
  • Wennberg, Christian L., et al. (författare)
  • Lennard-Jones Lattice Summation in Bilayer Simulations Has Critical Effects on Surface Tension and Lipid Properties
  • 2013
  • Ingår i: Journal of Chemical Theory and Computation. - 1549-9618 .- 1549-9626. ; 9:8, s. 3527-3537
  • Tidskriftsartikel (refereegranskat)abstract
    • The accuracy of electrostatic interactions in molecular dynamics advanced tremendously with the introduction of particle-mesh Ewald (PME) summation almost 20 years ago. Lattice summation electrostatics is now the de facto standard for most types of biomolecular simulations, and in particular, for lipid bilayers, it has been a critical improvement due to the large charges typically present in zwitterionic lipid headgroups. In contrast, Lennard-Jones interactions have continued to be handled with increasingly longer cutoffs, partly because few alternatives have been available despite significant difficulties in tuning cutoffs and parameters to reproduce lipid properties. Here, we present a new Lennard-Jones PME implementation applied to lipid bilayers. We confirm that long-range contributions are well approximated by dispersion corrections in simple systems such as pentadecane (which makes parameters transferable), but for inhomogeneous and anisotropic systems such as lipid bilayers there are large effects on surface tension, resulting in up to 5.5% deviations in area per lipid and order parameters-far larger than many differences for which reparameterization has been attempted. We further propose an approximation for combination rules in reciprocal space that significantly reduces the computational cost of Lennard-Jones PME and makes accurate treatment of all nonbonded interactions competitive with simulations employing long cutoffs. These results could potentially have broad impact on important applications such as membrane proteins and free energy calculations.
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