1
|
Smith KP, Chakravarthy S, Rahi A, Chakraborty M, Vosberg KM, Tonelli M, Plach MG, Grigorescu AA, Curtis JE, Varma D. SAXS/MC studies of the mixed-folded protein Cdt1 reveal monomeric, folded over conformations. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.03.573975. [PMID: 38260441 PMCID: PMC10802334 DOI: 10.1101/2024.01.03.573975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Cdt1 is a protein critical for DNA replication licensing and is well-established to be a binding partner of the minichromosome maintenance (MCM) complex. Cdt1 has also been demonstrated to have an emerging, "moonlighting" role at the kinetochore via direct binding to microtubules and to the Ndc80 complex. However, it is not known how the structure and conformations of Cdt1 could allow for these multiple, completely unique sets of protein complexes. And while there exist multiple robust methods to study entirely folded or entirely unfolded proteins, structure-function studies of combined, mixed folded/disordered proteins remain challenging. It this work, we employ multiple orthogonal biophysical and computational techniques to provide a detailed structural characterization of human Cdt1 92-546. DSF and DSCD show both folded winged helix (WH) domains of Cdt1 are relatively unstable. CD and NMR show the N-terminal and the linker regions are intrinsically disordered. Using DLS and SEC-MALS, we show that Cdt1 is polydisperse, monomeric at high concentrations, and without any apparent inter-molecular self-association. SEC-SAXS of the monomer in solution enabled computational modeling of the protein in silico. Using the program SASSIE, we performed rigid body Monte Carlo simulations to generate a conformational ensemble. Using experimental SAXS data, we filtered for conformations which did and did not fit our data. We observe that neither fully extended nor extremely compact Cdt1 conformations are consistent with our SAXS data. The best fit models have the N-terminal and linker regions extended into solution and the two folded domains close to each other in apparent "folded over" conformations. The best fit Cdt1 conformations are consistent with a function as a scaffold protein which may be sterically blocked without the presence of binding partners. Our studies also provide a template for combining experimental and computational biophysical techniques to study mixed-folded proteins.
Collapse
Affiliation(s)
- Kyle P Smith
- Department of Cell & Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
- Present Address, Xylia Therapeutics, Waltham, MA, 02451, USA
| | - Srinivas Chakravarthy
- Biophysics Collaborative Access Team, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Amit Rahi
- Department of Cell & Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Manas Chakraborty
- Department of Cell & Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Kristen M Vosberg
- Department of Cell & Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison, Department of Biochemistry, University of Wisconsin, Madison, WI, 53706, USA
| | | | - Arabela A Grigorescu
- Keck Biophysics Facility, Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60201, USA
| | - Joseph E Curtis
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD, 20899, United States
| | - Dileep Varma
- Department of Cell & Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| |
Collapse
|
2
|
Chen J, Liu X, Chen J. Targeting Intrinsically Disordered Proteins through Dynamic Interactions. Biomolecules 2020; 10:E743. [PMID: 32403216 PMCID: PMC7277182 DOI: 10.3390/biom10050743] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/04/2020] [Accepted: 05/09/2020] [Indexed: 12/18/2022] Open
Abstract
Intrinsically disordered proteins (IDPs) are over-represented in major disease pathways and have attracted significant interest in understanding if and how they may be targeted using small molecules for therapeutic purposes. While most existing studies have focused on extending the traditional structure-centric drug design strategies and emphasized exploring pre-existing structure features of IDPs for specific binding, several examples have also emerged to suggest that small molecules could achieve specificity in binding IDPs and affect their function through dynamic and transient interactions. These dynamic interactions can modulate the disordered conformational ensemble and often lead to modest compaction to shield functionally important interaction sites. Much work remains to be done on further elucidation of the molecular basis of the dynamic small molecule-IDP interaction and determining how it can be exploited for targeting IDPs in practice. These efforts will rely critically on an integrated experimental and computational framework for disordered protein ensemble characterization. In particular, exciting advances have been made in recent years in enhanced sampling techniques, Graphic Processing Unit (GPU)-computing, and protein force field optimization, which have now allowed rigorous physics-based atomistic simulations to generate reliable structure ensembles for nontrivial IDPs of modest sizes. Such de novo atomistic simulations will play crucial roles in exploring the exciting opportunity of targeting IDPs through dynamic interactions.
Collapse
Affiliation(s)
- Jianlin Chen
- Department of Hematology, Taizhou Central Hospital (Taizhou University Hospital), Taizhou 318000, Zhejiang, China;
| | - Xiaorong Liu
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA;
| | - Jianhan Chen
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA;
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA
| |
Collapse
|
3
|
Abstract
Replicative DNA helicases are essential cellular enzymes that unwind duplex DNA in front of the replication fork during chromosomal DNA replication. Replicative helicases were discovered, beginning in the 1970s, in bacteria, bacteriophages, viruses, and eukarya, and, in the mid-1990s, in archaea. This year marks the 20th anniversary of the first report on the archaeal replicative helicase, the minichromosome maintenance (MCM) protein. This minireview summarizes 2 decades of work on the archaeal MCM.
Collapse
|
4
|
Howell SC, Qiu X, Curtis JE. Monte Carlo simulation algorithm for B-DNA. J Comput Chem 2018; 37:2553-63. [PMID: 27671358 DOI: 10.1002/jcc.24474] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 07/12/2016] [Accepted: 07/23/2016] [Indexed: 01/12/2023]
Abstract
Understanding the structure-function relationship of biomolecules containing DNA has motivated experiments aimed at determining molecular structure using methods such as small-angle X-ray and neutron scattering (SAXS and SANS). SAXS and SANS are useful for determining macromolecular shape in solution, a process which benefits by using atomistic models that reproduce the scattering data. The variety of algorithms available for creating and modifying model DNA structures lack the ability to rapidly modify all-atom models to generate structure ensembles. This article describes a Monte Carlo algorithm for simulating DNA, not with the goal of predicting an equilibrium structure, but rather to generate an ensemble of plausible structures which can be filtered using experimental results to identify a sub-ensemble of conformations that reproduce the solution scattering of DNA macromolecules. The algorithm generates an ensemble of atomic structures through an iterative cycle in which B-DNA is represented using a wormlike bead-rod model, new configurations are generated by sampling bend and twist moves, then atomic detail is recovered by back mapping from the final coarse-grained configuration. Using this algorithm on commodity computing hardware, one can rapidly generate an ensemble of atomic level models, each model representing a physically realistic configuration that could be further studied using molecular dynamics. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Steven C Howell
- Neutron Condensed Matter Science Group, NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899-8562
| | - Xiangyun Qiu
- Department of Physics, The George Washington University, Washington, District of Columbia, 20052
| | - Joseph E Curtis
- Neutron Condensed Matter Science Group, NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899-8562.
| |
Collapse
|
5
|
Haider MJ, Zhang HV, Sinha N, Fagan JA, Kiick KL, Saven JG, Pochan DJ. Self-assembly and soluble aggregate behavior of computationally designed coiled-coil peptide bundles. SOFT MATTER 2018; 14:5488-5496. [PMID: 29923575 PMCID: PMC6355460 DOI: 10.1039/c8sm00435h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Coiled-coil peptides have proven useful in a range of materials applications ranging from the formation of well-defined fibrils to responsive hydrogels. The ability to design from first principles their oligomerization and subsequent higher order assembly offers their expanded use in producing new materials. Toward these ends, homo-tetrameric, antiparallel, coiled-coil, peptide bundles have been designed computationally, synthesized via solid-phase methods, and their solution behavior characterized. Two different bundle-forming peptides were designed and examined. Within the targeted coiled coil structure, both bundles contained the same hydrophobic core residues. However, different exterior residues on the two different designs yielded sequences with different distributions of charged residues and two different expected isoelectric points of pI 4.4 and pI 10.5. Both coiled-coil bundles were extremely stable with respect to temperature (Tm > 80 C) and remained soluble in solution even at high (millimolar) peptide concentrations. The coiled-coil tetramer was confirmed to be the dominant species in solution by analytical sedimentation studies and by small-angle neutron scattering, where the scattering form factor is well represented by a cylinder model with the dimensions of the targeted coiled coil. At high concentrations (5-15 mM), evidence of interbundle structure was observed via neutron scattering. At these concentrations, the synthetic bundles form soluble aggregates, and interbundle distances can be determined via a structure factor fit to scattering data. The data support the successful design of robust coiled-coil bundles. Despite their different sequences, each sequence forms loosely associated but soluble aggregates of the bundles, suggesting similar dissociated states for each. The behavior of the dispersed bundles is similar to that observed for natural proteins.
Collapse
Affiliation(s)
- Michael J. Haider
- Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA. ,
| | - Huixi Violet Zhang
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
| | - Nairiti Sinha
- Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA. ,
| | - Jeffrey A. Fagan
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
| | - Kristi L. Kiick
- Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA. ,
| | - Jeffery G. Saven
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
| | - Darrin J. Pochan
- Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA. ,
| |
Collapse
|
6
|
Combined Monte Carlo/torsion-angle molecular dynamics for ensemble modeling of proteins, nucleic acids and carbohydrates. J Mol Graph Model 2017; 73:179-190. [DOI: 10.1016/j.jmgm.2017.02.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 01/19/2017] [Accepted: 02/17/2017] [Indexed: 11/18/2022]
|
7
|
Designing and Performing Biological Solution Small-Angle Neutron Scattering Contrast Variation Experiments on Multi-component Assemblies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1009:65-85. [DOI: 10.1007/978-981-10-6038-0_5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
|
8
|
Cordeiro TN, Herranz-Trillo F, Urbanek A, Estaña A, Cortés J, Sibille N, Bernadó P. Structural Characterization of Highly Flexible Proteins by Small-Angle Scattering. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1009:107-129. [DOI: 10.1007/978-981-10-6038-0_7] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
9
|
Jeffries CM, Graewert MA, Blanchet CE, Langley DB, Whitten AE, Svergun DI. Preparing monodisperse macromolecular samples for successful biological small-angle X-ray and neutron-scattering experiments. Nat Protoc 2016; 11:2122-2153. [PMID: 27711050 PMCID: PMC5402874 DOI: 10.1038/nprot.2016.113] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) are techniques used to extract structural parameters and determine the overall structures and shapes of biological macromolecules, complexes and assemblies in solution. The scattering intensities measured from a sample contain contributions from all atoms within the illuminated sample volume, including the solvent and buffer components, as well as the macromolecules of interest. To obtain structural information, it is essential to prepare an exactly matched solvent blank so that background scattering contributions can be accurately subtracted from the sample scattering to obtain the net scattering from the macromolecules in the sample. In addition, sample heterogeneity caused by contaminants, aggregates, mismatched solvents, radiation damage or other factors can severely influence and complicate data analysis, so it is essential that the samples be pure and monodisperse for the duration of the experiment. This protocol outlines the basic physics of SAXS and SANS, and it reveals how the underlying conceptual principles of the techniques ultimately 'translate' into practical laboratory guidance for the production of samples of sufficiently high quality for scattering experiments. The procedure describes how to prepare and characterize protein and nucleic acid samples for both SAXS and SANS using gel electrophoresis, size-exclusion chromatography (SEC) and light scattering. Also included are procedures that are specific to X-rays (in-line SEC-SAXS) and neutrons, specifically preparing samples for contrast matching or variation experiments and deuterium labeling of proteins.
Collapse
Affiliation(s)
- Cy M. Jeffries
- European Molecular Biology Laboratory (EMBL) Hamburg Outstation, c/o
DESY. Hamburg, 22603, Germany
| | - Melissa A. Graewert
- European Molecular Biology Laboratory (EMBL) Hamburg Outstation, c/o
DESY. Hamburg, 22603, Germany
| | - Clément E. Blanchet
- European Molecular Biology Laboratory (EMBL) Hamburg Outstation, c/o
DESY. Hamburg, 22603, Germany
| | - David B. Langley
- Victor Chang Cardiac Research and Garvan Institutes, Darlinghurst,
NSW, Australia
| | - Andrew E. Whitten
- Australian Nuclear Science and Technology Organisation, Lucas
Heights, NSW, Australia
| | - Dmitri I Svergun
- European Molecular Biology Laboratory (EMBL) Hamburg Outstation, c/o
DESY. Hamburg, 22603, Germany
| |
Collapse
|
10
|
Archaeal MCM Proteins as an Analog for the Eukaryotic Mcm2-7 Helicase to Reveal Essential Features of Structure and Function. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2015; 2015:305497. [PMID: 26539061 PMCID: PMC4619765 DOI: 10.1155/2015/305497] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 04/05/2015] [Indexed: 11/18/2022]
Abstract
In eukaryotes, the replicative helicase is the large multisubunit CMG complex consisting of the Mcm2–7 hexameric ring, Cdc45, and the tetrameric GINS complex. The Mcm2–7 ring assembles from six different, related proteins and forms the core of this complex. In archaea, a homologous MCM hexameric ring functions as the replicative helicase at the replication fork. Archaeal MCM proteins form thermostable homohexamers, facilitating their use as models of the eukaryotic Mcm2–7 helicase. Here we review archaeal MCM helicase structure and function and how the archaeal findings relate to the eukaryotic Mcm2–7 ring.
Collapse
|
11
|
Zaccai NR, Sandlin CW, Hoopes JT, Curtis JE, Fleming PJ, Fleming KG, Krueger S. Deuterium Labeling Together with Contrast Variation Small-Angle Neutron Scattering Suggests How Skp Captures and Releases Unfolded Outer Membrane Proteins. Methods Enzymol 2015; 566:159-210. [PMID: 26791979 PMCID: PMC4913355 DOI: 10.1016/bs.mie.2015.06.041] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In Gram-negative bacteria, the chaperone protein Skp forms specific and stable complexes with membrane proteins while they are transported across the periplasm to the outer membrane. The jellyfish-like architecture of Skp is similar to the eukaryotic and archaeal prefoldins and the mitochondrial Tim chaperones, that is the α-helical "tentacles" extend from a β-strand "body" to create an internal cavity. Contrast variation small-angle neutron scattering (SANS) experiments on Skp alone in solution and bound in two different complexes to unfolded outer membrane proteins (uOMPs), OmpA and OmpW, demonstrate that the helical tentacles of Skp bind their substrate in a clamp-like mechanism in a conformation similar to that previously observed in the apo crystal structure of Skp. Deuteration of the uOMP component combined with contrast variation analysis allowed the shapes of Skp and uOMP as well as the location of uOMP with respect to Skp to be determined in both complexes. This represents unique information that could not be obtained without deuterium labeling of the uOMPs. The data yield the first direct structural evidence that the α-helical Skp tentacles move closer together on binding its substrate and that the structure of Skp is different when binding different uOMPs. This work presents, by example, a tutorial on performing SANS experiments using both deuterium labeling and contrast variation, including SANS theory, sample preparation, data collection, sample quality validation, data analysis, and structure modeling.
Collapse
Affiliation(s)
- Nathan R Zaccai
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Clifford W Sandlin
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - James T Hoopes
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland, USA
| | - Joseph E Curtis
- National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Patrick J Fleming
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Karen G Fleming
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Susan Krueger
- National Institute of Standards and Technology, Gaithersburg, Maryland, USA.
| |
Collapse
|
12
|
Abstract
DNA replication is essential for all life forms. Although the process is fundamentally conserved in the three domains of life, bioinformatic, biochemical, structural, and genetic studies have demonstrated that the process and the proteins involved in archaeal DNA replication are more similar to those in eukaryal DNA replication than in bacterial DNA replication, but have some archaeal-specific features. The archaeal replication system, however, is not monolithic, and there are some differences in the replication process between different species. In this review, the current knowledge of the mechanisms governing DNA replication in Archaea is summarized. The general features of the replication process as well as some of the differences are discussed.
Collapse
Affiliation(s)
- Lori M Kelman
- Program in Biotechnology, Montgomery College, Germantown, Maryland 20876;
| | | |
Collapse
|
13
|
Li L, Wang L, Alexov E. On the energy components governing molecular recognition in the framework of continuum approaches. Front Mol Biosci 2015; 2:5. [PMID: 25988173 PMCID: PMC4429657 DOI: 10.3389/fmolb.2015.00005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 02/04/2015] [Indexed: 01/14/2023] Open
Abstract
Molecular recognition is a process that brings together several biological macromolecules to form a complex and one of the most important characteristics of the process is the binding free energy. Various approaches exist to model the binding free energy, provided the knowledge of the 3D structures of bound and unbound molecules. Among them, continuum approaches are quite appealing due to their computational efficiency while at the same time providing predictions with reasonable accuracy. Here we review recent developments in the field emphasizing on the importance of adopting adequate description of physical processes taking place upon the binding. In particular, we focus on the efforts aiming at capturing some of the atomistic details of the binding phenomena into the continuum framework. When possible, the energy components are reviewed independently of each other. However, it is pointed out that rigorous approaches should consider all energy contributions on the same footage. The two major schemes for utilizing the individual energy components to predict binding affinity are outlined as well.
Collapse
Affiliation(s)
- Lin Li
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University Clemson, SC, USA
| | - Lin Wang
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University Clemson, SC, USA
| | - Emil Alexov
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University Clemson, SC, USA
| |
Collapse
|
14
|
Krueger S, Shin JH, Curtis JE, Rubinson KA, Kelman Z. The solution structure of full-length dodecameric MCM by SANS and molecular modeling. Proteins 2014; 82:2364-74. [DOI: 10.1002/prot.24598] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/24/2014] [Accepted: 04/29/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Susan Krueger
- NIST Center for Neutron Research, National Institute of Standards and Technology; Gaithersburg Maryland 20899
| | - Jae-Ho Shin
- Division of Applied Biology and Chemistry, College of Agriculture and Life Sciences; Kyungpook National University; Daegu Republic of Korea
| | - Joseph E. Curtis
- NIST Center for Neutron Research, National Institute of Standards and Technology; Gaithersburg Maryland 20899
| | - Kenneth A. Rubinson
- NIST Center for Neutron Research, National Institute of Standards and Technology; Gaithersburg Maryland 20899
- Department of Biochemistry and Molecular Biology; Wright State University; Dayton Ohio 45435
| | - Zvi Kelman
- Biomolecular Measurement Division, National Institute of Standards and Technology; Gaithersburg Maryland 20899
- Institute for Bioscience and Biotechnology Research; Rockville Maryland 20850
| |
Collapse
|
15
|
Watson MC, Curtis JE. Rapid and accurate calculation of small-angle scattering profiles using the golden ratio. J Appl Crystallogr 2013. [DOI: 10.1107/s002188981301666x] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Calculating the scattering intensity of anN-atom system is a numerically exhaustingO(N2) task. A simple approximation technique that scales linearly with the number of atoms is presented. Using an exact expression for the scattering intensityI(q) at a given wavevectorq, the rotationally averaged intensityI(q) is computed by evaluatingI(q) in several scattering directions. The orientations of theqvectors are taken from a quasi-uniform spherical grid generated by the golden ratio. Using various biomolecules as examples, this technique is compared with an established multipole expansion method. For a given level of speed, the technique is more accurate than the multipole expansion for anisotropically shaped molecules, while comparable in accuracy for globular shapes. The processing time scales sub-linearly inNwhen the atoms are identical and lie on a lattice. The procedure is easily implemented and should accelerate the analysis of small-angle scattering data.
Collapse
|
16
|
Russo LC, Asega AF, Castro LM, Negraes PD, Cruz L, Gozzo FC, Ulrich H, Camargo ACM, Rioli V, Ferro ES. Natural intracellular peptides can modulate the interactions of mouse brain proteins and thimet oligopeptidase with 14-3-3ε and calmodulin. Proteomics 2012; 12:2641-55. [DOI: 10.1002/pmic.201200032] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 05/31/2012] [Accepted: 06/03/2012] [Indexed: 02/03/2023]
Affiliation(s)
- Lilian C. Russo
- Department of Cell Biology and Development; Biomedical Sciences Institute; University of São Paulo; São Paulo Brazil
| | - Amanda F. Asega
- Laboratory of Applied Toxinology (LETA); Butantan Institute; SP Brazil
| | - Leandro M. Castro
- Department of Cell Biology and Development; Biomedical Sciences Institute; University of São Paulo; São Paulo Brazil
| | - Priscilla D. Negraes
- Biochemistry Department; Chemistry Institute; University of São Paulo; São Paulo Brazil
| | - Lilian Cruz
- Department of Cell Biology and Development; Biomedical Sciences Institute; University of São Paulo; São Paulo Brazil
| | - Fabio C. Gozzo
- Chemistry Institute; Campinas State University; Campinas SP Brazil
| | - Henning Ulrich
- Biochemistry Department; Chemistry Institute; University of São Paulo; São Paulo Brazil
| | | | - Vanessa Rioli
- Laboratory of Applied Toxinology (LETA); Butantan Institute; SP Brazil
| | - Emer S. Ferro
- Department of Cell Biology and Development; Biomedical Sciences Institute; University of São Paulo; São Paulo Brazil
| |
Collapse
|