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  • 1
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    Structure of a core fragment of glycoprotein H from pseudorabies virus in complex with antibody [Microbiology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-01-04
    Description: Compared with many well-studied enveloped viruses, herpesviruses use a more sophisticated molecular machinery to induce fusion of viral and cellular membranes during cell invasion. This essential function is carried out by glycoprotein B (gB), a class III viral fusion protein, together with the heterodimer of glycoproteins H and L (gH/gL). In pseudorabies virus (PrV), a porcine herpesvirus, it was shown that gH/gL can be substituted by a chimeric fusion protein gDgH, containing the receptor binding domain (RBD) of glycoprotein D fused to a truncated version of gH lacking its N-terminal domain. We report here the 2.1-Å resolution structure of the core fragment of gH present in this chimera, bound to the Fab fragment of a PrV gH-specific monoclonal antibody. The structure strongly complements the information derived from the recently reported structure of gH/gL from herpes simplex virus type 2 (HSV-2). Together with the structure of Epstein-Barr virus (EBV) gH/gL reported in parallel, it provides insight into potentially functional conserved structural features. One feature is the presence of a syntaxin motif, and the other is an extended “flap” masking a conserved hydrophobic patch in the C-terminal domain, which is closest to the viral membrane. The negative electrostatic surface potential of this domain suggests repulsive interactions with the lipid heads. The structure indicates the possible unmasking of an extended hydrophobic patch by movement of the flap during a receptor-triggered conformational change of gH, exposing a hydrophobic surface to interact with the viral membrane during the fusion process.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 2
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    Crystal structure of the RNA-dependent RNA polymerase from influenza C virus (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-10-28
    Description: Negative-sense RNA viruses, such as influenza, encode large, multidomain RNA-dependent RNA polymerases that can both transcribe and replicate the viral RNA genome. In influenza virus, the polymerase (FluPol) is composed of three polypeptides: PB1, PB2 and PA/P3. PB1 houses the polymerase active site, whereas PB2 and PA/P3 contain, respectively, cap-binding and endonuclease domains required for transcription initiation by cap-snatching. Replication occurs through de novo initiation and involves a complementary RNA intermediate. Currently available structures of the influenza A and B virus polymerases include promoter RNA (the 5' and 3' termini of viral genome segments), showing FluPol in transcription pre-initiation states. Here we report the structure of apo-FluPol from an influenza C virus, solved by X-ray crystallography to 3.9 A, revealing a new 'closed' conformation. The apo-FluPol forms a compact particle with PB1 at its centre, capped on one face by PB2 and clamped between the two globular domains of P3. Notably, this structure is radically different from those of promoter-bound FluPols. The endonuclease domain of P3 and the domains within the carboxy-terminal two-thirds of PB2 are completely rearranged. The cap-binding site is occluded by PB2, resulting in a conformation that is incompatible with transcription initiation. Thus, our structure captures FluPol in a closed, transcription pre-activation state. This reveals the conformation of newly made apo-FluPol in an infected cell, but may also apply to FluPol in the context of a non-transcribing ribonucleoprotein complex. Comparison of the apo-FluPol structure with those of promoter-bound FluPols allows us to propose a mechanism for FluPol activation. Our study demonstrates the remarkable flexibility of influenza virus RNA polymerase, and aids our understanding of the mechanisms controlling transcription and genome replication.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hengrung, Narin -- El Omari, Kamel -- Serna Martin, Itziar -- Vreede, Frank T -- Cusack, Stephen -- Rambo, Robert P -- Vonrhein, Clemens -- Bricogne, Gerard -- Stuart, David I -- Grimes, Jonathan M -- Fodor, Ervin -- 075491/Z/04/Wellcome Trust/United Kingdom -- 092931/Z/10/Z/Wellcome Trust/United Kingdom -- G1000099/Medical Research Council/United Kingdom -- G1100138/Medical Research Council/United Kingdom -- MR/K000241/1/Medical Research Council/United Kingdom -- England -- Nature. 2015 Nov 5;527(7576):114-7. doi: 10.1038/nature15525. Epub 2015 Oct 26.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK. ; Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, University of Oxford, Oxford OX3 7BN, UK. ; European Molecular Biology Laboratory, Grenoble Outstation and University Grenoble Alpes-Centre National de la Recherche Scientifique-EMBL Unit of Virus Host-Cell Interactions, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France. ; Diamond Light Source Ltd, Harwell Science &Innovation Campus, Didcot OX11 0DE, UK. ; Global Phasing Ltd, Sheraton House, Castle Park, Cambridge CB3 0AX, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26503046" target="_blank"〉PubMed〈/a〉
    Keywords: Apoenzymes/chemistry/metabolism ; Binding Sites ; Crystallography, X-Ray ; Endonucleases/chemistry/metabolism ; Enzyme Activation ; Influenzavirus C/*enzymology ; Models, Molecular ; Peptide Chain Initiation, Translational ; Promoter Regions, Genetic/genetics ; Protein Binding ; Protein Structure, Tertiary ; Protein Subunits/chemistry/metabolism ; RNA Caps/metabolism ; RNA Replicase/*chemistry/metabolism ; RNA, Viral/biosynthesis/metabolism ; Ribonucleoproteins/chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Glycoprotein organization of Chikungunya virus particles revealed by X-ray crystallography (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-12-03
    Description: Chikungunya virus (CHIKV) is an emerging mosquito-borne alphavirus that has caused widespread outbreaks of debilitating human disease in the past five years. CHIKV invasion of susceptible cells is mediated by two viral glycoproteins, E1 and E2, which carry the main antigenic determinants and form an icosahedral shell at the virion surface. Glycoprotein E2, derived from furin cleavage of the p62 precursor into E3 and E2, is responsible for receptor binding, and E1 for membrane fusion. In the context of a concerted multidisciplinary effort to understand the biology of CHIKV, here we report the crystal structures of the precursor p62-E1 heterodimer and of the mature E3-E2-E1 glycoprotein complexes. The resulting atomic models allow the synthesis of a wealth of genetic, biochemical, immunological and electron microscopy data accumulated over the years on alphaviruses in general. This combination yields a detailed picture of the functional architecture of the 25 MDa alphavirus surface glycoprotein shell. Together with the accompanying report on the structure of the Sindbis virus E2-E1 heterodimer at acidic pH (ref. 3), this work also provides new insight into the acid-triggered conformational change on the virus particle and its inbuilt inhibition mechanism in the immature complex.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Voss, James E -- Vaney, Marie-Christine -- Duquerroy, Stephane -- Vonrhein, Clemens -- Girard-Blanc, Christine -- Crublet, Elodie -- Thompson, Andrew -- Bricogne, Gerard -- Rey, Felix A -- England -- Nature. 2010 Dec 2;468(7324):709-12. doi: 10.1038/nature09555.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut Pasteur, Departement de Virologie, Unite de Virologie Structurale, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21124458" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Chikungunya virus/*chemistry ; Cryoelectron Microscopy ; Crystallography, X-Ray ; Drosophila melanogaster ; Hydrogen-Ion Concentration ; Membrane Glycoproteins/*chemistry ; Models, Molecular ; Multiprotein Complexes/chemistry ; Protein Multimerization ; Protein Precursors/chemistry ; Protein Structure, Quaternary ; Viral Envelope Proteins/*chemistry ; Viral Fusion Proteins/chemistry ; Virion/*chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
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    Crystal structure of a nucleocapsid-like nucleoprotein-RNA complex of respiratory syncytial virus (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-12-08
    Description: The respiratory syncytial virus (RSV) is an important human pathogen, yet neither a vaccine nor effective therapies are available to treat infection. To help elucidate the replication mechanism of this RNA virus, we determined the three-dimensional (3D) crystal structure at 3.3 A resolution of a decameric, annular ribonucleoprotein complex of the RSV nucleoprotein (N) bound to RNA. This complex mimics one turn of the viral helical nucleocapsid complex, which serves as template for viral RNA synthesis. The RNA wraps around the protein ring, with seven nucleotides contacting each N subunit, alternating rows of four and three stacked bases that are exposed and buried within a protein groove, respectively. Combined with electron microscopy data, this structure provides a detailed model for the RSV nucleocapsid, in which the bases are accessible for readout by the viral polymerase. Furthermore, the nucleoprotein structure highlights possible key sites for drug targeting.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tawar, Rajiv G -- Duquerroy, Stephane -- Vonrhein, Clemens -- Varela, Paloma F -- Damier-Piolle, Laurence -- Castagne, Nathalie -- MacLellan, Kirsty -- Bedouelle, Hugues -- Bricogne, Gerard -- Bhella, David -- Eleouet, Jean-Francois -- Rey, Felix A -- New York, N.Y. -- Science. 2009 Nov 27;326(5957):1279-83. doi: 10.1126/science.1177634.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut Pasteur, Unite de Virologie Structurale, Departement de Virologie and CNRS Unite de Recherche Associee (URA) 3015, 25 Rue du Dr Roux, 75724 Paris Cedex 15, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19965480" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Binding Sites ; Cryoelectron Microscopy ; Crystallography, X-Ray ; Image Processing, Computer-Assisted ; Models, Molecular ; Molecular Sequence Data ; Nucleic Acid Conformation ; Nucleocapsid Proteins/*chemistry/metabolism ; Protein Structure, Secondary ; Protein Structure, Tertiary ; Protein Subunits/chemistry/metabolism ; RNA, Viral/*chemistry/metabolism ; Respiratory Syncytial Viruses/*chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
    Electronic Resource
    Electronic Resource
    Entropy maximization constrained by solvent flatness: a new method for macromolecular phase extension and map improvement (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 193-212 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A practical generally applicable procedure for exponential modeling to maximum likelihood of macromolecular data sets constrained by a moderately large basis set of reliable phases and a molecular envelope is described, based on the computer program MICE [Bricogne & Gilmore (1990). Acta Cryst. A46, 284–297]. Procedures were first tested with simulated data sets. Exact and randomly perturbed amplitudes and phases were generated, together with a known envelope for solvent-free protein and for protein in an electron-dense crystal mother liquor typical of many real protein crystals. These experiments established useful guidelines and values for various parameters. Tests with basis sets chosen from the largest amplitudes indicate that exponential models with considerable correct extrapolated phase and amplitude information can be constructed from as few as 16% of the total number of reflections, with mean phase errors of about 30°, at resolution limits of either 5 or 3 Å. When the shape of the solvent channels in macromolecular crystals is known, it offers an important additional source of information. MICE was, therefore, adapted to average the density outside the molecular boundary defined by an input envelope. This flattening process imposes a uniform density distribution in solvent-filled channels as an additional constraint on the exponential model and is analogous to the treatment of solvent in conventional solvent flattening. Experimental data for cytidine deaminase, a structure recently solved by making extensive use of conventional solvent flattening, provides an example of the performance of maximum-entropy methods in a real situation and a compelling comparison of this method to standard procedures. Exponential models of the electron density constrained by the most reliable phases obtained by multiple isomorphous replacement with anomalous scattering (MIRAS) (figure of merit 〉 0.7, representing 34% of the total number of reflections) and by the envelope give rise to centroid electron-density maps which are quantitatively superior by numerous statistical criteria to conventionally solvent-flattened density. Similarity of these maps to the 2Fobs − Fcalc map calculated with phases obtained after crystallographic refinement of the model implies that maximum-entropy extrapolation provides better phases for the remaining 66% of the reflections than the original centroid MIRAS distributions. Importantly, the solvent-flattened electron density, although it did permit interpretation of the map which was not readily accomplished with the MIRAS map, contains substantial errors. It is proposed that errors of this sort may account for previously noted deficiencies of the solvent-flattening method [Fenderson, Herriott & Adman (1990). J. Appl. Cryst. 23, 115–131] and for the occasional tendency of incorrect interpretations to be `locked in' by crystallographic refinement [Brändén & Jones (1990). Nature (London), 343, 687–689, and references cited therein]. Solvent flattening with combined maximization of entropy and likelihood represents a phase-refinement path independent of atomic models, using the experimental amplitudes and the most reliable phases. It should, therefore, become a valuable and generally useful procedure in macromolecular crystal structure determination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992008540
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  • 6
    Electronic Resource
    Electronic Resource
    Direct phase determination for the molecular envelope of tryptophanyl-tRNA synthetase from Bacillus stearothermophilus by X-ray contrast variation (1990)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 57-68 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Monoclinic crystals of Bacillus stearothermophilus tryptophanyl-tRNA synthetase grown in the presence of substrate trytophan (space group P21) display evidence of a low-resolution trigonal space group (P321). The origin and averaging transformations for the local 32 point group of this unusually clear sixfold non-crystallographic symmetry may be inferred without prior estimation of the electron density. This local symmetry was exploited in conjunction with solvent density contrast variation to determine the shape of the molecular envelope. X-ray intensities measured from crystals equilibrated in mother liquors of three different electron densities were used to estimate three parameters for each reflection: the modulus of the envelope transform, |Gh]; and components, Xh and Yh, relative to Gh, of the structure-factor vector for the transform of intramolecular density fluctuations. The moduli {|Gh|} behave somewhat like structure-factor amplitudes from small-molecule crystals, and estimation of their unknown phases was successfully carried out by statistical direct methods. Reflections to 18 Å resolution, which obey rather well the symmetry of space group P321, were merged to produce an asymmetric unit in that space group. |Gh| values for the 34 strongest of these were phased using the small-molecule direct-methods package MITHRIL [Gilmore (1984). J. Appl Cryst. 17, 42-46]. The best phase set was expanded back to the P21 lattice and negative density was truncated to generate initial phases for all reflections to 18 Å resolution. Phase refinement by iterative imposition of the local 32 symmetry produced an envelope with convincing features consistent with known properties of the enzyme. The envelope implies that the tryptophanyl-tRNA synthetase dimer is an elongated structure with an axial ratio of about 4: 1, in which the monomers have two distinct domains of unequal size. The smaller of these occurs at the dimer interface, and resembles the nucleotide binding portion of the tyrosyl-tRNA synthetase. It may therefore contain the amino-terminal one hundred or so residues, including all three cysteines, previously suggested to comprise a nucleotide-binding domain in the tryptophanyl enzyme. A purely crystallographic test of the overall features of this envelope was carried out by transporting it to a tetragonal crystal form of the same protein in which the asymmetric unit is a monomer. The small domain fits snugly inside three mercury and one gold heavy-atom binding sites for this crystal form; and symmetry-related molecules provide excellent, but very different, lattice contacts in nearly all directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389009682
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  • 7
    Electronic Resource
    Electronic Resource
    Methods and programs for direct-space exploitation of geometric redundancies (1976)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 32 (1976), S. 832-847 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Phases can be determined for geometrically redundant amplitudes by iteration of the following procedure: compute an electron density map from the currently available phases; average the electron densities of all the crystallographically independent molecules; rebuild the crystal(s) from this averaged subunit, setting the density outside the molecular boundaries to its average value; obtain phase information from the resulting structure, and combine it with that given by isomorphous replacement to produce the phases to be used in the next iteration. This algorithm converges very rapidly, and has proved to be a powerful tool in the solution of two large unknown protein structures. This paper describes the computational techniques developed to implement it, which include a swift and general method for real-space averaging of electron density maps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739476001691
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  • 8
    Electronic Resource
    Electronic Resource
    Direct phase determination by entropy maximization and likelihood ranking: status report and perspectives (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 37-60 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new multisolution phasing method based on entropy maximization and likelihood ranking, proposed for the specific purpose of extending probabilistic direct methods to the field of macromolecules, has been implemented in two different computer programs and applied to a wide variety of problems. The latter comprise the determination of small crystal structures from X-ray diffraction data obtained from single crystals or from powders, and from electron diffraction data partially phased by image processing of electron micrographs, the ab initio generation and ranking of phase sets for small proteins; and the improvement of poor quality phases for a larger protein at medium resolution under constraint of solvent flatness. These applications show that the primary goal of this new method – namely increasing the accuracy and sensitivity of probabilistic phase indications compared with conventional direct methods – has been achieved. The main components of the method are (1) a tree-directed search through a space of trial phase sets; (2) the saddle-point method for calculating joint probabilities of structure factors, using entropy maximization; (3) likelihood-based scores to rank trial phase sets and prune the search tree; (4) efficient schemes, based on error-correcting codes, for sampling trial phase sets; (5) a statistical analysis of the scores for automatically selecting reliable phase indications. They have been implemented to varying degrees of completeness in a computer program (BUSTER) and tested on two small structures as well as on the small protein crambin. The main obstructions to successful ab initio phasing in the latter case seem to reside in the accumulation of phase sampling errors and in the lack of a properly defined molecular envelope, both of which can be remedied within the methods proposed. A review of the Bayesian statistical theory encompassing all phasing procedures, proposed earlier as an extension of the initial theory, shows that the techniques now available in BUSTER bring closer a number of major enhancements of standard macromolecular phasing techniques, namely isomorphous replacement, molecular replacement, solvent flattening and non-crystallographic symmetry averaging. The gradual implementation of the successive stages of this `Bayesian programme' should lead to an increasingly integrated, effective and dependable phasing procedure for macromolecular structure determination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992010400
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  • 9
    Electronic Resource
    Electronic Resource
    Geometric sources of redundancy in intensity data and their use for phase determination (1974)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 30 (1974), S. 395-405 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Linear equations are derived in direct space, which express the relation between the electron densities of crystals built from the same molecule, but with different lattices or several identical subunits in their asymmetric units. They are shown to be equivalent to the most general 'molecular-replacement' phase equations in reciprocal space. The solution of these phase equations by the method of successive projections is discussed. This algorithm, best implemented in direct space by averaging operations, is shown to be convergent for over-determined problems, and to be equivalent to a least-squares solution of the phase equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739474010722
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  • 10
    Electronic Resource
    Electronic Resource
    Maximum entropy and the foundations of direct methods (1984)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 40 (1984), S. 410-445 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A revision of the classical statistical methods of phase determination is presented which widens their theoretical foundations and consolidates their practical implementation, thus bringing about a major increase of their power. In a brief introductory survey (§ 1), the basic concepts and mathematical techniques of direct methods are analysed. Closer scrutiny (§ 2) reveals that severe inadequacies still impair the effectiveness of these methods. The asymptotic character of the series used to approximate joint distributions of structure factors demands that great caution be exercised to guarantee their accuracy, and this requirement can only be fulfilled if they are used within a multisolution algorithm in which the prior distribution of atoms is constantly updated so as to incorporate at every stage all the phase information assumed to that point. Further limitations follow from the traditional practice of approximating joint distributions by products of marginal distributions of single invariants. A scheme for simultaneously overcoming both difficulties is then proposed. The pivotal element of this scheme is a device, based on Jaynes's maximum-entropy principle, for exploiting the prior knowledge of some structure factors in the construction of the joint distributions of others conditional to that knowledge. Jaynes's maximum-entropy formalism is presented and systematically applied to the construction of the requisite non-uniform prior distributions of atoms in § 3. The problem of effectively approximating conditional distributions of very large numbers of structure factors is solved in § 4 by a novel technique of 'maximum-entropy inversion' of Karle-Hauptman matrices, and the result obtained is shown to generalize the most sophisticated probabilistic formulae hitherto obtained. This procedure is proved in § 5 to coincide with an enhancement of the standard method of asymptotic expansions by means of Daniels's saddlepoint approximation. Its relationship to determinantal methods is investigated in § 6. A numerical algorithm for implementing these ideas is presented in § 7, together with an application to data from the small protein Crambin, and a unified strategy for its use ab initio is described and discussed in § 8. It is concluded that the phase-determination strategy proposed here will expedite the realization of the full potential of probabilistic direct methods, and is likely to bring macromolecular structures within their reach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767384000866
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