Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 1 December 1975

1976 ◽  
Vol 192 (1109) ◽  
pp. 371-391
Keyword(s):  
Molecular Biology ◽  
Coiled Coil ◽  
Helical Structure ◽  
X Ray Diffraction ◽  
Helical Structures ◽  
X Ray ◽  
Double Helical Structure ◽  
Leading Role ◽  
Replication Scheme ◽  
Related Proteins

The Copley Medal is awarded to Dr F. H. C. Crick, F. R. S. In 1953 Crick and Watson proposed the double-helical model for DNA, in which the bases are arranged in complementary pairs so that the molecule is capable of self-replication and is thus the essential carrier of genetic information in living cells. This proposal was based on an inspired interpretation of the results of X-ray diffraction analysis of DNA carried out by Wilkins, Franklin and their collaborators, and on the chemical analyses of Chargaff and others. The replication scheme inherent in the double-helical structure of DNA made it possible for the first time to discuss the mechanism of heredity in molecular terms; it has been the most fruitful concept in the whole of biology during the past 25 years, and has been the basis for the explosive development of molecular biology. Besides his part in this dramatic discovery, Crick played a very important part in increasing our understanding of the way in which the genetic message is carried on DNA (the ‘coding’ problem), and of the mechanisms by which it is translated into specific sequences of amino acids in the proteins synthesized by the cell. He has also continued to play a leading rôle in many other aspects of molecular biology, and has made important contributions to X-ray studies of crystalline proteins, fibrous proteins and viruses. These include the theory of diffraction from helical structures, the coiled-coil model of α-keratin and related proteins, the structure of collagen, and the theoretical basis of the construction of ‘spherical’ viruses. More recently, Crick has had an important influence on work in the fields of development and of chromosome structure.

Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 1 December 1975

1976 ◽  
Vol 348 (1653) ◽  
pp. 153-173
Keyword(s):  
Molecular Biology ◽  
Coiled Coil ◽  
Helical Structure ◽  
X Ray Diffraction ◽  
Helical Structures ◽  
X Ray ◽  
Double Helical Structure ◽  
Leading Role ◽  
Replication Scheme ◽  
Related Proteins

The Copley Medal is awarded to Dr F. H. C. Crick, F. R. S. In 1953 Crick and Watson proposed the double-helical model for DNA, in which the bases are arranged in complementary pairs so that the molecule is capable of self-replication and is thus the essential carrier of genetic information in living cells. This proposal was based on an inspired interpretation of the results of X-ray diffraction analysis of DNA carried out by Wilkins, Franklin and their collaborators, and on the chemical analyses of Chargaff and others. The replication scheme inherent in the double-helical structure of DNA made it possible for the first time to discuss the mechanism of heredity in molecular terms; it has been the most fruitful concept in the whole of biology during the past 25 years, and has been the basis for the explosive development of molecular biology. Besides his part in this dramatic discovery, Crick played a very important part in increasing our understanding of the way in which the genetic message is carried on DNA (the ‘coding’ problem), and of the mechanisms by which it is translated into specific sequences of amino acids in the proteins synthesized by the cell. He has also continued to play a leading rôle in many other aspects of molecular biology, and has made important contributions to X-ray studies of crystalline proteins, fibrous proteins and viruses. These include the theory of diffraction from helical structures, the coiled-coil model of α-keratin and related proteins, the structure of collagen, and the theoretical basis of the construction of ‘spherical’ viruses. More recently, Crick has had an important influence on work in the fields of development and of chromosome structure.

Diffuse scattering in protein crystallography

1995 ◽  
Vol 28 (2) ◽  
pp. 131-169 ◽  
Author(s):  
Jean-Pierre Benoit ◽  
Jean Doucet
Keyword(s):  
Molecular Biology ◽  
Active Site ◽  
Diffuse Scattering ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Physico Chemical ◽  
Chemical Conditions ◽  
Functional Mechanisms

The understanding of flexibility and deformability in proteins is one of the current major challenges of structural molecular biology. The knowledge of the average atomic positions of three-dimensional folding of proteins, which is obtained either by X-ray diffraction or n.m.r. spectroscopy, is generally not sufficient to explain their functional mechanisms. Very often it is necessary to consider the existence of other concerted atomic motions as, for example, in the well-known case of the CO molecule fixation at the active site of myoglobin which requires the concerted displacement of a large number of atoms in order to open a channel down to this site. This opening, which depends on the physico-chemical conditions, plays the role of a regulator in the biochemical reactions (Janin & Wodak, 1983; Tainer et al. 1984; Westhof et al. 1984; Ormos et al. 1988).

Preparation and Characterization of Helical Structure ZnS by Solvothermal Method

2011 ◽  
Vol 233-235 ◽  
pp. 1954-1957
Author(s):  
Xiao Yan Yan ◽  
Zhi Qiang Wei ◽  
Li Gang Liu ◽  
Xiao Juan Wu ◽  
Ge Zhang
Keyword(s):  
Electron Microscopy ◽  
Solvothermal Method ◽  
Helical Structure ◽  
Sodium Sulphide ◽  
X Ray Diffraction ◽  
Hexagonal Crystal ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron

Helical structure ZnS were successfully prepared via solvothermal method by the reaction of zinc acetate and sodium sulphide. The composition, morphology, and microstructure of the sample were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), the corresponding selected area electron diffraction (SAED) and X-ray energy spectrum (EDS). The experiment results show that the sample is 1-D hexagonal crystal ZnS and grows along the [002] direction, and is helical structure, with lengths in the range of 100-200 nm, the diameter about 5-15 nm, and pitch about 20nm.

scholarly journals Linking Temperature, Cation Concentration and Water Activity for the B to Z Conformational Transition in DNA

2018 ◽  
Author(s):  
Jaime M. Ferreira ◽  
Richard D. Sheardy
Keyword(s):  
Water Activity ◽  
Electrostatic Interactions ◽  
Conformational Transition ◽  
Helical Structure ◽  
Titration Calorimetry ◽  
Heat Capacity Change ◽  
Helical Structures ◽  
Double Helical Structure ◽  
Surface Areas ◽  
High Concentrations

High concentrations of Na+ or [Co(NH3)6]3+ can induce the B to Z conformational transition in alternating (dC-dG) oligo and polynucleotides. The use of short DNA oligomers (dC-dG)4 and (dm5C-dG)4 as models can allow a thermodynamic characterization of the transition. Both form right handed double helical structures (B-DNA) in standard phosphate buffer with 115 mM Na+ at 25 oC. However, at 2.0 M Na+ or 200 mM [Co(NH3)6]3+, (dm5C-dG)4 assumes a left handed double helical structure (Z-DNA) while the unmethylated (dC-dG)4 analogue remains right handed under those conditions. We have previously demonstrated that the enthalpy of the transition at 25 oC for either inducer can be determined using isothermal titration calorimetry (ITC) [Ferreira, J. M. & Sheardy, R. D., Biophys. J. 2006, 91, 1–7]. Here, ITC is used to investigate the linkages between temperature, water activity and DNA conformation. We found that the determined enthalpy for each titration varied linearly with temperature allowing determination of the heat capacity change (DCp) between the initial and final states. As expected, the DCp values were dependent upon the cation (i.e. Na+ vs [Co(NH3)6]3+) as well as the sequence of the DNA oligomer (i. e., methylated vs unmethylated). Osmotic stress experiments were carried out to determine the gain or loss of water by the oligomer induced by the titration. The results are discussed in terms of solvent accessible surface areas, electrostatic interactions and the role of water.

Electron diffraction of helical structures

1992 ◽  
Vol 50 (1) ◽  
pp. 518-519
Author(s):  
T. Ruiz ◽  
R. Diaz ◽  
J-L. Ranck ◽  
D.L.D. Caspar ◽  
D.J. DeRosier
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Helical Structure ◽  
Lipid Monolayer ◽  
Electron Diffraction Data ◽  
Helical Structures ◽  
Protein Aggregate ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Diffraction Patterns

Electron microscopy has advantages over X-ray diffraction for the study of helical structures. For X-ray studies, one needs large well oriented samples which are difficult to obtain. Only one helical structure, TMV, has been solved by conventional X-ray analysis using multiple isomorphous replacement. In contrast, one requires single particles or small rafts for studies by electron microscopy. We are attempting to use a combination of imaging and electron diffraction data to analyze helical structures at 9-10 Å resolution in order to visualize α-helices. To obtain electron diffraction patterns we produced well-ordered domains (∽ 1-3 μm in diameter) for diffraction work. Several methods succeeded in aligning helical particles : the lipid monolayer technique, mica sandwiching and unidirectional blotting. The lipid monolayer technique proved to be the best for high resolution work. The three samples under study (flagellar filaments from Salmonella typhimurium, TMV and TMV stacked disk protein aggregate) gave electron diffraction patterns out to ∽10 Å resolution.

Differential height characteristics of plasmid and G-wire DNA as determined by AFM

1994 ◽  
Vol 52 ◽  
pp. 1052-1053
Author(s):  
T. C. Marsh ◽  
J. Vesenka ◽  
E. Henderson
Keyword(s):  
Plasmid Dna ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Helical Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dimension One

Atomic-Force Microscopy (AFM) has become an effective tool in the three dimensional characterization of biological systems and is capable of Angstrom sensitivity in the vertical dimension. One unresolved dilemma is that the observed height (diameter) of B-DNA being about 10Å, is less than half its x-ray diffraction value. In this paper we attempt to determine the source of this discrepancy by comparing plasmid DNA co-deposited with a novel form of DNA called “G-wires” (Figure 1). G-wires are formed by G-rich sequences. They are composed of G-4 DNA, a quadruple helical structure. X-ray data of G-4 DNA gives a diameter of 27Å, comparable to that expected for B-DNA (20 to 25Å). In the AFM these structures have a significantly greater height (av. = 22 Å) compared to double stranded (av. = 7 Å) or supercoiled B-DNA (av. = 14 Å) (Figure 2). Thus, the apparent height of nucleic acids in the AFM is dependent upon their innate structural characteristics.

scholarly journals Linking Temperature, Cation Concentration and Water Activity for the B to Z Conformational Transition in DNA

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1806 ◽  
Author(s):  
Jaime Ferreira ◽  
Richard Sheardy
Keyword(s):  
Water Activity ◽  
Electrostatic Interactions ◽  
Conformational Transition ◽  
Helical Structure ◽  
Titration Calorimetry ◽  
Heat Capacity Change ◽  
Helical Structures ◽  
Double Helical Structure ◽  
Surface Areas ◽  
High Concentrations

High concentrations of Na+ or [Co(NH3)6]3+ can induce the B to Z conformational transition in alternating (dC-dG) oligo and polynucleotides. The use of short DNA oligomers (dC-dG)4 and (dm5C-dG)4 as models can allow a thermodynamic characterization of the transition. Both form right handed double helical structures (B-DNA) in standard phosphate buffer with 115 mM Na+ at 25 °C. However, at 2.0 M Na+ or 200 μM [Co(NH3)6]3+, (dm5C-dG)4 assumes a left handed double helical structure (Z-DNA) while the unmethylated (dC-dG)4 analogue remains right handed under those conditions. We have previously demonstrated that the enthalpy of the transition at 25 °C for either inducer can be determined using isothermal titration calorimetry (ITC). Here, ITC is used to investigate the linkages between temperature, water activity and DNA conformation. We found that the determined enthalpy for each titration varied linearly with temperature allowing determination of the heat capacity change (ΔCp) between the initial and final states. As expected, the ΔCp values were dependent upon the cation (i.e., Na+ vs. [Co(NH3)6]3+) as well as the sequence of the DNA oligomer (i.e., methylated vs. unmethylated). Osmotic stress experiments were carried out to determine the gain or loss of water by the oligomer induced by the titration. The results are discussed in terms of solvent accessible surface areas, electrostatic interactions and the role of water.

The helical structure of the β -1, 3-linked xylan in some siphoneous green algae

1969 ◽  
Vol 173 (1031) ◽  
pp. 209-221 ◽  
Keyword(s):  
Green Algae ◽  
Cell Walls ◽  
Model Building ◽  
Hexagonal Lattice ◽  
Bound Water ◽  
Helical Structure ◽  
Polymer Chains ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fixed Orientation

An account is given of the conformation of a β -1, 3-linked xylan which is the structural poly-saccharide in some siphoneous green algae. The cell walls from Penicillus dumetosus were studied by X -ray diffraction, infra-red absorption and model building. The structure consists of three xylan polymer chains intertwining to form a three-strand helix with symmetry sr. Each helix has six xylose residues per turn in a pitch of approximately 18 Å. A novel type of inter-chain bonding has been proposed which consists of a cyclic triad of hydrogen bonds formed between the O 2 atoms, one from each individual chain. Computations show that the molecules are in fixed orientation in a hexagonal lattice. The calculations favour right-handed helices and there is evidence of stoichiometrically bound water on the surface of the molecule.

Peterhouse, The Royal Society and molecular biology

2000 ◽  
Vol 54 (3) ◽  
pp. 369-385 ◽  
Author(s):  
J. M. Thomas
Keyword(s):  
Molecular Biology ◽  
Royal Society ◽  
Rockefeller Foundation ◽  
Natural Sciences ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Subject ◽  
Warren Weaver

The term molecular biology was coined by Warren Weaver, a mathematician who was head of the natural sciences section of the Rockefeller Foundation, in his report to the president of the Foundation in 1938. The origins of the subject may be located in various places or periods, but Sir Peter Medawar used to argue that it was Sir William Bragg and W.T. Astbury at the Davy Faraday Laboratory in London who began it, when they investigated the structures of materials such as silk, wool and hair by X–ray diffraction. Others say that J.D. Bernal was the progenitor. Peterhouse, a Cambridge college, was a hothouse of the subject.

Intermediate filament structure

1985 ◽  
Vol 5 (7) ◽  
pp. 573-579 ◽  
Author(s):  
R. D. B. Fraser ◽  
T. P. MacRae
Keyword(s):  
Intermediate Filament ◽  
Linear Density ◽  
Lattice Mismatch ◽  
Coiled Coil ◽  
X Ray Diffraction ◽  
Present Communication ◽  
Detailed Model ◽  
X Ray ◽  
Filament Structure ◽  
Oriented Parallel

In a previous communication (Biosci. Rep. 3, 517–525, 1993) we described quantitative X-ray diffraction studies of α-keratin which were shown to be consistent with the presence of finite arrays of repeating units, successive arrays being set down at axial intervals of 470 Å. In addition the axial interval between repeating units in an array was shown to be 197.9 Å. It was suggested that this could most readily be explained by supposing that a surfacelattice was present which contained a dislocation along a helical path with unit height h = 470 Å and unit twist |t| = 49.1°. The number of repeating units was shown to be in the range 7–9. With 7 repeats the mismatch of the lattice along the dislocation is small and this choice was used to develop a detailed model for the filament. Subsequent studies of molecular interactions have shown however that the coiled-coil rope segments in the rod domain of the molecule are most probably oriented parallel to the dislocation, and so minimization of lattice mismatch may be less important than originally supposed. In the present communication it is shown that the choice of 8, rather than 7, for the number of repeating units yields a model which is more compatible with estimates of the linear density and also provides the basis for a general model for polymorphism in intermediate filament lattices.

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