Biophysics

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Biophysics Projects[edit]

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Welcome to the Biophysics Project and the Department of Biophysics![edit]

Soliton Wave animation by Dr. Danko Georgiev
Biophysics Course


Département de Biophysique[edit]

  • "Cette discipline aboutit à l'utilisation de moyens modernes d'investigation qualitatifs et quantitatifs en Biologie comme en Médecine, ainsi que, dans cette dernière, à des moyens thérapeutiques à partir de l'utilisation notamment des ondes et radiations."

"La biophysique est l'étude des phénomènes physiques intervenant chez les êtres vivants."

Faculté de Biologie

Département de Biologie Moléculaire[edit]

"La biologie moléculaire est une discipline scientifique au croisement de la génétique, de la biochimie et de la physique, dont l'objet est la compréhension des mécanismes de fonctionnement de la cellule au niveau moléculaire. La biochimie est la discipline scientifique qui étudie les réactions chimiques ayant lieu au sein des cellules."

Languages: (en),(fr), (ro)[edit]

DNA Double-Helix

"Biophysics is the study of physical phenomena that occur in living beings"... , but without a definition of Life, or of the "living", the subject of Biophysics would remain only vaguely pointing at functional organisms. Determining what Life is also remains, therefore, in the domain of Biophysics--specifically of Mathematical biophysics or Relational Biology. In other words, one is asking:
What are the fundamental relations among the components and processes, and also <relations> among relations occurring in an organism that distinguish the latter from a simple or complex physical system, such as a crystal, a stone, a machine or automaton, a robot, a computer, and so on ?
A related question is that of the underlying operational logics of an organism (which is not Boolean, and it is not perhaps even a quantum logic), and of its defining axioms.
Welcome!

Hello and Welcome to Wikiversity Biophysics! You can contact us with questions at the colloquium or me personally when you need help. Please remember to sign and date your finished comments when participating in discussions. The signature icon Insert-signature.png above the edit window makes it simple. All users are expected to abide by our Privacy, Civility, and the Terms of Use policies while at Wikiversity.

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You do not need to be an educator to edit. You only need to be bold to contribute and to experiment with the sandbox or your userpage. See you around Wikiversity! --~~~~

Welcome to an International Biophysics Course ![edit]

  • Lecture notes can be now obtained in: English (en), French (fr) and Romanian (ro), (ISO 691-1) languages.
  • New instructors or students may add, however, more languages-- among those already approved by the Wikiversity for such educational and research web site projects.
  • The addition to this website of specialized expert new lectures or lecture notes or web links to Lecture notes and other Biophysics or Crystallography departments-- that fit in with the announced Syllabus-- is encouraged and appreciated.
  • For questions regarding Ph.D. review questions in Crystallography see also Doctoral review questions in Crystallography
  • DNA Double-helix Molecular Model

Syllabus[edit]

  • Protein and Nucleic Acid Structure and Dynamics:

Up-to-date descriptions of the background, methods and techniques of protein crystallography, including the mathematical concepts and tools needed to understand X-ray and neutron diffraction, as well as 2D-FT NMR determination of molecular structure in solution. (See also a simple introduction to Proton (H-1) NMR (fr))

Protein crystallography is a multidisciplinary area of research that overlaps in part with several subfields of biochemistry, structural molecular biology, bioinformatics, biophysics, biochemistry and organic chemistry.
XRD Structure Determination Steps

Lecture 15:Examples of crystal lattices: fcc, bcc, diamond; Miller indices of crystal lattice planes.

A- and B- DNA X-ray Diffraction Patterns compared
  • Mathematical Foundations of Biophysics:
    • Computational biophysics: Molecular Dynamics and computer simulation techniques (e.g., Monte Carlo)
    • Mathematical Foundations of Quantum Biophysics and Quantum Biochemistry
    • Harmonic analysis in Medical Diagnostic Imaging and Patient image processing, contrast enhancement or reconstruction
    • Modelling cells and multicellular organisms
    • Biotopology and Algebraic Topology applications to Mathematical Biophysics
    • Relational Networks and Categories of Metabolic-Replication Systems
    • Relational Biology applications to understanding Aging and Metabolic Disorders


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Wikiversity Topic:Photosynthesis
The Lessons in the
Photosynthetic Mechanisms ORIENTATION
  • Photosynthesis in the Biosphere
  • Simple photosynthesis overview.svg



  • Syllabus of an International Course on Photosynthesis
Overall Chemical Reactions for Plant Photosynthesis
    • Structure and Dynamics of Photosynthetic Membranes
    • Quantum mechanisms of photosynthetic water oxidation in algae and higher plants
    • Mechanisms of PS I photosystem
    • Manganese and calcium ion role(s) in photosynthetic water oxidation
    • The Oxygen Evolving Complex: Structure and Function
    • FCS applications to Photosynthesis
    • Single Molecule Detection and Femtosecond Laser Spectroscopy studies of Photosynthesis
    • High-field and 2D-NMR investigations of Photosynthetic Mechanisms
    • FT-NIR Spectroscopy and Hyper-spectral/Chemical Imaging of Photosynthetic Cells and Functional Chloroplasts

Learning materials and introductory articles[edit]

Carbon Fixation and Photorespiration in Plants
  1. w:C4 carbon fixation: trace experiments with radioactive labels
  2. Quantum physics aspects of w:Photosynthesis
  3. Photosynthetic systems: w:PSI and w:PSII coupling
  4. w:aquaporin
  5. Specific w:chloride channels
  6. w:Hydronium ion
  7. Specific w:Hydronium ion
  8. Beta counting
    1. w:Regulation of metabolic pathways
  9. Specific inhibitors of photosynthesis, such as hydroxylamine (NH2OH) and uncouplers
    1. Gas chromatography and mass spectrometry
    2. Gamma counting
    3. w:Enzyme assays
    4. w:Micronutrients
      1. Manganese ions' role(s) in photosynthesis
        1. Neutron activation analysis of Mn contents in purified, active thylakoid (photosynthetic) membranes and PSII-particles
    5. w:Enzymes
    6. Krebs' cycle
    7. w:Pyruvate decarboxylation
    8. The ATP cycle and its coupling to photosynthetic processes
    9. w:Oxidative phosphorilation
    10. w:Calvin Cycle
    11. Dickens-Horecker cycle
    12. Hexose interconversions
    13. w:Neoglucogenesis
    14. w:Glycogenesis
    15. w:Glycogenolysis
    16. w:Cori cycle
    17. w:fatty acids
    18. Essential fatty acids
      1. poly-unsaturated fatty acids (w:PUFA);
      2. w:eicosanoids: w:prostaglandins, w:thromboxanes, w:prostacyclin and w:leukotrienes.
    19. The w:lipid bilayer, item, and transport across the bilayer through pores, channels, etc.
    20. w:PCR

Selected Examples[edit]

Solutions of the Bessel differential equation.
  1. Bessel functions arise in many mathematical models such as those for vibrating surfaces. Such functions also occur in the analysis of X-ray Diffraction patterns of helical molecules such as certain proteins and also nucleic acids (DNAs, RNAs.)

"When mathematically analyzing a vibrating drum the boundary conditions lead to solutions that are harmonic functions. When using cylindrical coordinates, the solutions are sines, cosines or Bessel functions (in the radial direction)".


Notes[edit]


  • Presentation = Présentation sur Protéines

"Protéine, macromolécule composée d'acides aminés reliés par des liaisons peptidiques, présente chez les organismes vivants et essentielle à leur fonctionnement. Découvertes en 1838, les protéines sont le principal composant des cellules, représentant plus de 50 p. 100 de leur poids sec. Le mot protéine vient du grec proteios qui signifie « premier ».

La forme des protéines est très variable : elle va des longues fibres présentes dans les tissus conjonctifs et les cheveux aux globules compacts et solubles capables de traverser la membrane des cellules. Les protéines sont des macromolécules dont le poids moléculaire varie de quelques milliers à plus d'un million d'unités. Elles sont spécifiques à chaque espèce vivante et à chaque organe. On estime qu'il existe environ trente mille protéines différentes chez l'Homme, dont 2 p. 100 seulement ont été décrites. Les protéines servent à construire et à entretenir les cellules, et leur dégradation chimique fournit de l'énergie, produisant près de 4 kilocalories par gramme (voir Métabolisme).

Outre leur rôle dans la croissance et l'entretien des cellules, les protéines sont également responsables de la contraction des muscles. Les enzymes digestives sont des protéines, de même que l'insuline et la plupart des autres hormones, ainsi que les anticorps du système immunitaire et l'hémoglobine. Les chromosomes, qui transmettent toutes les caractéristiques héréditaires sous forme de gènes, sont constitués d'acides nucléiques et de protéines (histones)."

Course textbooks[edit]

Things remaining to do-Short list[edit]

  1. Continue and expand lectures
  2. New Instructor involvement in biophysics courses
  3. Web links to biophysics and protein structure syllabi at several universities
  4. Add other resources (such as: Structure and Genomic Databases, Image libraries and galleries, Library links, and so on.
  5. Develop student Enrollment and student Help pages

See also[edit]

                      • ==Lectures (en), (fr),(ro)==

Leçons par thèmes = Lectures by subject[edit]

  • Données de physique utilisées en biologie [Modifier]

Leçons par niveau = Lectures by level[edit]

  • Novice Niveau 0 à 2 Débutant Niveau 2 à 5 Intermédiaire Niveau 6 à 9
  • Avancé Niveau 10 à 12
    • Données de physique utilisées en biologie
  • Expert Niveau 13 à 15
    • Ondes et optique géométrique
  • Perfectionnement Niveau 16 à 18
    • Modèle:2--Microspéctroscopie et Analyse Biochimique des Images d'Embryon. Modifier!

Instructors[edit]

If you have knowledge in this field, please post your name here to answer questions from students.

Short list of course consultants and instructors:[edit]

  • User:Bci21- Instructor & Professor-Professeur
  • Biophysik
  • Y
  • Z

Molecular Models of DNA[edit]

Purified DNA precipitated in a water jug
Animated 3D-wire model of DNA
While this purified DNA precipitated in a water jug (left) appears to be a formless mass, nucleic acids actually possess intricate structure at the nanoscale (right).

Molecular models of DNA structures are representations of the molecular geometry and topology of Deoxyribonucleic acid (DNA) molecules using one of several means, with the aim of simplifying and presenting the essential, physical and chemical, properties of DNA molecular structures either in vivo or in vitro. These representations include closely packed spheres (CPK models) made of plastic, metal wires for 'skeletal models', graphic computations and animations by computers, artistic rendering. Computer molecular models also allow animations and molecular dynamics simulations that are very important for understanding how DNA functions in vivo.

The more advanced, computer-based molecular models of DNA involve molecular dynamics simulations as well as quantum mechanical computations of vibro-rotations, delocalized molecular orbitals (MOs), electric dipole moments, hydrogen-bonding, and so on. DNA molecular dynamics modeling involves simulations of DNA molecular geometry and topology changes with time as a result of both intra- and inter- molecular interactions of DNA. Whereas molecular models of Deoxyribonucleic acid (DNA) molecules such as closely packed spheres (CPK models) made of plastic or metal wires for 'skeletal models' are useful representations of static DNA structures, their usefulness is very limited for representing complex DNA dynamics. Computer molecular modeling allows both animations and molecular dynamics simulations that are very important for understanding how DNA functions in vivo.

History[edit]

The A-DNA double-helix molecular model of Crick and Watson (consistent with their X-ray data) for which they received a Nobel prize together with M.H.F. Wilkins.

Template:Single strand DNA discovery

Template:Further2

From the very early stages of structural studies of DNA by X-ray diffraction and biochemical means, molecular models such as the Watson-Crick double-helix model were successfully employed to solve the 'puzzle' of DNA structure, and also find how the latter relates to its key functions in living cells. The first high quality X-ray diffraction patterns of A-DNA were reported by Rosalind Franklin and Raymond Gosling in 1953.[1] The first calculations of the Fourier transform of an atomic helix were reported one year earlier by Cochran, Crick and Vand,[2] and were followed in 1953 by the computation of the Fourier transform of a coiled-coil by Crick.[3]

Structural information is generated from X-ray diffraction studies of oriented DNA fibers with the help of molecular models of DNA that are combined with crystallographic and mathematical analysis of the X-ray patterns.

The first reports of a double-helix molecular model of B-DNA structure were made by Watson and Crick in 1953.[4][5] Last-but-not-least, Maurice F. Wilkins, A. Stokes and H.R. Wilson, reported the first X-ray patterns of in vivo B-DNA in partially oriented salmon sperm heads.[6]

The development of the first correct double-helix molecular model of DNA by Crick and Watson may not have been possible without the biochemical evidence for the nucleotide base-pairing ([A---T]; [C---G]), or Chargaff's rules.[7][8][9][10][11][12] Although such initial studies of DNA structures with the help of molecular models were essentially static, their consequences for explaining the in vivo functions of DNA were significant in the areas of protein biosynthesis and the quasi-universality of the genetic code. Epigenetic transformation studies of DNA in vivo were however much slower to develop in spite of their importance for embryology, morphogenesis and cancer research. Such chemical dynamics and biochemical reactions of DNA are much more complex than the molecular dynamics of DNA physical interactions with water, ions and proteins/enzymes in living cells.

Importance[edit]

Template:Further2

An old standing dynamic problem is how DNA "self-replication" takes place in living cells that should involve transient uncoiling of supercoiled DNA fibers. Although DNA consists of relatively rigid, very large elongated biopolymer molecules called "fibers" or chains (that are made of repeating nucleotide units of four basic types, attached to deoxyribose and phosphate groups), its molecular structure in vivo undergoes dynamic configuration changes that involve dynamically attached water molecules and ions. Supercoiling, packing with histones in chromosome structures, and other such supramolecular aspects also involve in vivo DNA topology which is even more complex than DNA molecular geometry, thus turning molecular modeling of DNA into an especially challenging problem for both molecular biologists and biotechnologists. Like other large molecules and biopolymers, DNA often exists in multiple stable geometries (that is, it exhibits conformational isomerism) and configurational, quantum states which are close to each other in energy on the potential energy surface of the DNA molecule.

Such varying molecular geometries can also be computed, at least in principle, by employing ab initio quantum chemistry methods that can attain high accuracy for small molecules, although claims that acceptable accuracy can be also achieved for polynuclelotides, as well as DNA conformations, were recently made on the basis of VCD spectral data. Such quantum geometries define an important class of ab initio molecular models of DNA whose exploration has barely started especially in connection with results obtained by VCD in solutions. More detailed comparisons with such ab initio quantum computations are in principle obtainable through 2D-FT NMR spectroscopy and relaxation studies of polynucleotide solutions or specifically labeled DNA, as for example with deuterium labels.

In an interesting twist of roles, the DNA molecule itself was proposed to be utilized for quantum computing. Both DNA nanostructures as well as DNA 'computing' biochips have been built.

Fundamental concepts[edit]

DNA chemical structure
DNA three-dimensional model
At left, the chemical structure of DNA showing the base-pairing. This depiction of a DNA duplex lacks information about the molecule's three-dimensional structure, at right.

The chemical structure of DNA is insufficient to understand the complexity of the 3D structures of DNA. On the other hand, animated molecular models allow one to visually explore the three-dimensional (3D) structure of DNA. The DNA model shown (far right) is a space-filling, or CPK, model of the DNA double-helix. Animated molecular models, such as the wire, or skeletal, type shown at the top of this article, allow one to visually explore the three-dimensional (3D) structure of DNA. Another type of DNA model is the space-filling, or CPK, model.

The hydrogen bonding dynamics and proton exchange is very different by many orders of magnitude between the two systems of fully hydrated DNA and water molecules in ice. Thus, the DNA dynamics is complex, involving nanosecond and several tens of picosecond time scales, whereas that of liquid ice is on the picosecond time scale, and that of proton exchange in ice is on the millisecond time scale. The proton exchange rates in DNA and attached proteins may vary from picosecond to nanosecond, minutes or years, depending on the exact locations of the exchanged protons in the large biopolymers.

A simple harmonic oscillator 'vibration' is only an oversimplified dynamic representation of the longitudinal vibrations of the DNA intertwined helices which were found to be anharmonic rather than harmonic as often assumed in quantum dynamic simulations of DNA.

±===DNA structure===

The structure of DNA shows a variety of forms, both double-stranded and single-stranded. The mechanical properties of DNA, which are directly related to its structure, are a significant problem for cells. Every process which binds or reads DNA is able to use or modify the mechanical properties of DNA for purposes of recognition, packaging and modification. The extreme length (a chromosome may contain a 10 cm long DNA strand), relative rigidity and helical structure of DNA has led to the evolution of histones and of enzymes such as topoisomerases and helicases to manage a cell's DNA. The properties of DNA are closely related to its molecular structure and sequence, particularly the weakness of the hydrogen bonds and electronic interactions that hold strands of DNA together compared to the strength of the bonds within each strand. 86.165.181.158 (discuss) 12:35, 10 May 2014 (UTC) Experimental techniques which can directly measure the mechanical properties of DNA are relatively new, and high-resolution visualization in solution is often difficult. Nevertheless, scientists have uncovered large amount of data on the mechanical properties of this polymer, and the implications of DNA's mechanical properties on cellular processes is a topic of active current research.

The DNA found in many cells can be macroscopic in length - a few centimetres long for each human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. In eukaryotes this is carried by spool-like proteins known as histones, around which DNA winds. It is the further compaction of this DNA-protein complex which produces the well known mitotic eukaryotic chromosomes.

Alternate non-double-helical models have been proposed for the in vivo structure of DNA, such as in plasmids and chromatin.[13][14] Such "side-by-side" models of DNA were proposed early in the history of molecular biology, but these were set aside in favor of the double-helical model due to X-ray crystallography of DNA duplexes and later the nucleosome core particle, as well as the discovery of topoisomerases, and these non-double-helical models are not currently accepted by the mainstream scientific community.[15]

DNA structure determination using molecular modeling and DNA X-ray patterns[edit]

major steps involved in X-ray crystallography of biomolecules
DNA X-ray patterns
Left, the major steps involved in DNA structure determination by X-ray crystallography showing the important role played by molecular models of DNA structure in this iterative process. Right, an image of actual A- and B- DNA X-ray patterns obtained from oriented and hydrated DNA fibers (courtesy of Dr. Herbert R. Wilson, FRS- see refs. list).

After DNA has been separated and purified by standard biochemical techniques one has a sample in a jar much like in the figure at the top of this article. Below are the main steps involved in generating structural information from X-ray diffraction studies of oriented DNA fibers that are drawn from the hydrated DNA sample with the help of molecular models of DNA that are combined with crystallographic and mathematical analysis of the X-ray patterns.

Paracrystalline lattice models of B-DNA structures[edit]

Silica glass is another example of a material which is organized into a paracrystalline lattice.

A paracrystalline lattice, or paracrystal, is a molecular or atomic lattice with significant amounts (e.g., larger than a few percent) of partial disordering of molecular arrangements. Limiting cases of the paracrystal model are nanostructures, such as glasses, liquids, etc., that may possess only local ordering and no global order. A simple example of a paracrystalline lattice is shown in the following figure for a silica glass:

Liquid crystals also have paracrystalline rather than w:crystalline structures.

Highly hydrated B-DNA occurs naturally in living cells in such a paracrystalline state, which is a dynamic one in spite of the relatively rigid DNA double-helix stabilized by parallel hydrogen bonds between the nucleotide base-pairs in the two complementary, helical DNA chains (see figures). For simplicity most DNA molecular models omit both water and ions dynamically bound to B-DNA, and are thus less useful for understanding the dynamic behaviors of B-DNA in vivo. The physical and mathematical analysis of X-ray[16][17] and spectroscopic data for paracrystalline B-DNA is therefore much more complicated than that of crystalline, A-DNA X-ray diffraction patterns. The paracrystal model is also important for DNA technological applications such as DNA nanotechnology. Novel techniques that combine X-ray diffraction of DNA with X-ray microscopy in hydrated living cells are now also being developed.[18]

Genomic and biotechnology applications of DNA molecular modeling[edit]

Molecular models are useful in the design of structures for DNA nanotechnology. Here, individual DNA tiles (model at left) self-assemble into a highly ordered DNA 2D-nanogrid (AFM image at right).

There are various uses of DNA molecular modeling in Genomics and Biotechnology research applications, from DNA repair to PCR and DNA nanostructures. Two-dimensional DNA junction arrays have been visualized by Atomic force microscopy.[19]

DNA molecular modeling has various uses in genomics and biotechnology, with research applications ranging from DNA repair to PCR and DNA nanostructures. These include computer molecular models of molecules as varied as RNA polymerase, an E. coli, bacterial DNA primase template suggesting very complex dynamics at the interfaces between the enzymes and the DNA template, and molecular models of the mutagenic, chemical interaction of potent carcinogen molecules with DNA. These are all represented in the gallery below.

Technological application include a DNA biochip and DNA nanostructures designed for DNA computing and other dynamic applications of DNA nanotechnology.[20][21][22][23][24][25] The image at right is of self-assembled DNA nanostructures. The DNA “tile” structure in this image consists of four branched junctions oriented at 90° angles. Each tile consists of nine DNA oligonucleotides as shown; such tiles serve as the primary “building block” for the assembly of the DNA nanogrids shown in the AFM micrograph.

Quadruplex DNA may be involved in certain cancers.[26][27] Images of quadruplex DNA are in the gallery below.

Gallery of DNA models[edit]

See also[edit]


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External links for the International Biophysics Course[edit]

  • Basics
    1. The International System of Units, item
    2. Nomenclature of organic chemistry,item,
    3. w:Logarithms
    4. w:Nuclides
    5. w:Radioactive decay
    6. w:gas laws, Gases and Gas Laws
    7. w:Partial pressure and w:mole fraction
    8. w:Osmosis
    9. w:Diffusion
    10. pH, pKa's and titration
    11. Buffers
  • Biomolecules -- Structures, classification and properties of:
    1. w:Nucleic acids
    2. w:Amino acids
    3. w:Protein
    4. w:Carbohydrate
    5. w:Lipid
  • Laboratory and Analytical Methods
    1. Simple (glass) laboratory equipment and how to use it
    2. Laboratory safety
    3. w:Size exclusion chromatography
    4. UV-VIS Spectrometry
    5. Centrifugation and w:Ultracentrifugation
    6. w:Electrophoresis
    7. w:Chromatography
    • Amino acids
      1. w:Decarboxylation
      2. w:Transamination
      3. General amino acid synthesis
      4. General amino acid catabolism
      5. Special amino acid metabolism
      6. Amino acid interconversion
      7. w:Urea cycle, item
      8. Gamma-glutamyl cycle
      9. Associated: w:Gout,w:Maple syrup disease
    • Proteins
      1. In vivo nucleic acids synthesis
      2. Nucleic acid degradation, pyrimidine and purine catabolism
      3. w:Peptide bond
      4. In vivo protein synthesis

References[edit]

  1. Franklin, R.E., Gosling, R.G. (6 March 1953). "The Structure of Sodium Thymonucleate Fibres I. The Influence of Water Content". Acta Cryst. 6 (8): 673. doi:10.1107/S0365110X53001939. 
    Franklin, R.E., Gosling, R.G. (6 March 1953). "The Structure of Sodium Thymonucleate Fibres II. The Cylindrically Symmetrical Patterson Function". Acta Cryst. 6 (8): 678. doi:10.1107/S0365110X53001940. 
  2. Cochran, W., Crick, F.H.C., Vand V. (1952). "The Structure of Synthetic Polypeptides. 1. The Transform of Atoms on a Helix". Acta Cryst. 5 (5): 581–6. doi:10.1107/S0365110X52001635. 
  3. Crick, F.H.C. (1953a). "The Fourier Transform of a Coiled-Coil". Acta Cryst. 6 (8–9): 685–9. doi:10.1107/S0365110X53001952. 
  4. Watson, James D., Crick, Francis H.C. (25 April 1953). "A structure for Deoxyribose Nucleic Acid" (PDF). Nature 171 (4356): 737–8. doi:10.1038/171737a0. PMID 13054692. http://www.nature.com/nature/dna50/watsoncrick.pdf. , .
  5. Watson, J.D; Crick F.H.C. (1953b). "The Structure of DNA". Cold Spring Harbor Symposia on Quantitative Biology 18: 123–31. PMID 13168976. 
  6. Wilkins M.H.F., A.R. Stokes A.R. & Wilson, H.R. (1953). "Molecular Structure of Deoxypentose Nucleic Acids" (PDF). Nature 171 (4356): 738–40. doi:10.1038/171738a0. PMID 13054693. http://www.nature.com/nature/dna50/wilkins.pdf. 
  7. Elson D, Chargaff E (1952). "On the deoxyribonucleic acid content of sea urchin gametes". Experientia 8 (4): 143–5. doi:10.1007/BF02170221. PMID 14945441. 
  8. Chargaff E, Lipshitz R, Green C (1952). "Composition of the deoxypentose nucleic acids of four genera of sea-urchin". J Biol Chem 195 (1): 155–160. PMID 14938364. 
  9. Chargaff E, Lipshitz R, Green C, Hodes ME (1951). "The composition of the deoxyribonucleic acid of salmon sperm". J Biol Chem 192 (1): 223–230. PMID 14917668. 
  10. Chargaff E (1951). "Some recent studies on the composition and structure of nucleic acids". J Cell Physiol Suppl 38 (Suppl). 
  11. Magasanik B, Vischer E, Doniger R, Elson D, Chargaff E (1950). "The separation and estimation of ribonucleotides in minute quantities". J Biol Chem 186 (1): 37–50. PMID 14778802. 
  12. Chargaff E (1950). "Chemical specificity of nucleic acids and mechanism of their enzymatic degradation". Experientia 6 (6): 201–9. doi:10.1007/BF02173653. PMID 15421335. 
  13. Wu, Richard; Te Wu, Tai (1996). "A novel intact circular dsDNA supercoil". Bulletin of Mathematical Biology 58 (6): 1171–85. doi:10.1007/BF02458388. PMID 8953261. 
  14. Delmonte, Clive (2009). "Reflections on the Secondary Structure of DNA and Other Biopolymers". Journal of Chemistry, Biochemistry, and Molecular Biology (Scientific Journals International) 1 (1). http://www.scientificjournals.org/journals2009/j_of_chemistry1_2009.htm. Retrieved 1 October 2011. 
  15. Gautham, N. (25 May 2004). "Response to "Variety in DNA secondary structure"". Current Science 86 (10): 1352–1353. http://cs-test.ias.ac.in/cs/Downloads/article_37537.pdf. Retrieved 25 May 2012. "However, the discovery of topoisomerases took "the sting" out of the topological objection to the plectonaemic double helix. A major challenge for the role assigned to topoisomerases is that they are unnecessary to fulfil that role. The strands of double helical DNA have long been known to separate rapidly in aqueous urea and in non-aqueous solvents in the total absence of topoisomerases and in the total absence of any protein whatsoever. The more recent solution of the single crystal X-ray structure of the nucleosome core particle showed nearly 150 base pairs of the DNA (i.e. about 15 complete turns), with a structure that is in all essential respects the same as the Watson–Crick model. (However, the computer algorithm then in use was built around the presumption that all structural solutions would be double helical.)" 
  16. Hosemann R., Bagchi R.N., Direct analysis of diffraction by matter, North-Holland Publs., Amsterdam – New York, 1962.
  17. Baianu, I.C. (1978). "X-ray scattering by partially disordered membrane systems". Acta Cryst. A34 (5): 751–3. doi:10.1107/S0567739478001540. 
  18. Yamamoto Y, Shinohara K (October 2002). "Application of X-ray microscopy in analysis of living hydrated cells". Anat. Rec. 269 (5): 217–23. doi:10.1002/ar.10166. PMID 12379938. 
  19. Mao, Chengde; Sun, Weiqiong & Seeman, Nadrian C. (16 June 1999). "Designed Two-Dimensional DNA Holliday Junction Arrays Visualized by Atomic Force Microscopy". Journal of the American Chemical Society 121 (23): 5437–43. doi:10.1021/ja9900398. 
  20. Robinson, Bruche H.; Seeman, Nadrian C. (August 1987). "The Design of a Biochip: A Self-Assembling Molecular-Scale Memory Device". Protein Engineering 1 (4): 295–300. doi:10.1093/protein/1.4.295. ISSN 0269-2139. PMID 3508280.  Link
  21. Rothemund, Paul W. K.; Ekani-Nkodo, Axel; Papadakis, Nick; Kumar, Ashish; Fygenson, Deborah Kuchnir & Winfree, Erik (22 December 2004). "Design and Characterization of Programmable DNA Nanotubes". Journal of the American Chemical Society 126 (50): 16344–52. doi:10.1021/ja044319l. PMID 15600335. 
  22. Keren, K.; Kinneret Keren, Rotem S. Berman, Evgeny Buchstab, Uri Sivan, Erez Braun (November 2003). "DNA-Templated Carbon Nanotube Field-Effect Transistor". Science 302 (6549): 1380–2. doi:10.1126/science.1091022. PMID 14631035. http://www.sciencemag.org/cgi/content/abstract/sci;302/5649/1380. 
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Further reading[edit]

  • Applications of Novel Techniques to Health Foods, Medical and Agricultural Biotechnology.(June 2004) I. C. Baianu, P. R. Lozano, V. I. Prisecaru and H. C. Lin., q-bio/0406047.
  • F. Bessel, Untersuchung des Theils der planetarischen Störungen, Berlin Abhandlungen (1824), article 14.
  • Sir Lawrence Bragg, FRS. The Crystalline State, A General survey. London: G. Bells and Sons, Ltd., vols. 1 and 2., 1966., 2024 pages.
  • Cantor, C. R. and Schimmel, P.R. Biophysical Chemistry, Parts I and II., San Franscisco: W.H. Freeman and Co. 1980. 1,800 pages.
  • Voet, D. and J.G. Voet. Biochemistry, 2nd Edn., New York, Toronto, Singapore: John Wiley & Sons, Inc., 1995, ISBN 0-471-58651-X., 1361 pages.
  • Watson, G. N. A Treatise on the Theory of Bessel Functions., (1995) Cambridge University Press. ISBN 0-521-48391-3.
  • Watson, James D. Molecular Biology of the Gene. New York and Amsterdam: W.A. Benjamin, Inc. 1965., 494 pages.
  • Wentworth, W.E. Physical Chemistry. A short course., Malden ( Mass.): Blackwell Science, Inc. 2000.
  • Herbert R. Wilson, FRS. Diffraction of X-rays by proteins, Nucleic Acids and Viruses., London: Edward Arnold (Publishers) Ltd. 1966.
  • Kurt Wuthrich. NMR of Proteins and Nucleic Acids., New York, Brisbane,Chicester, Toronto, Singapore: J. Wiley & Sons. 1986., 292 pages.
  • Hallin PF, David Ussery D (2004). "CBS Genome Atlas Database: A dynamic storage for bioinformatic results and DNA sequence data". Bioinformatics 20 (18): 3682–6. doi:10.1093/bioinformatics/bth423. PMID 15256401. 
  • Zhang CT, Zhang R, Ou HY (2003). "The Z curve database: a graphic representation of genome sequences". Bioinformatics 19 (5): 593-599. [1] PMID 12651717

External links[edit]

Databases for DNA molecular models and sequences[edit]

X-ray diffraction

Neutron scattering

X-ray microscopy

Electron microscopy

NMR databases

Genomic and structural databases

Atomic force microscopy

Template:Nucleic acids


References[edit]

Virtual Labs[edit]

Virtual Molecular Biology and Biophysics laboratories
Ion Trap in a Mass Spectrometer

(Schéma d'un analyseur de type trappe ionique (pièges à ions) 3D et trajectoire des ions, en spectrométrie de mass).

NMR spectrometer
COSY 2D-NMR Spectrum
2D-FT (N)MRI Imager
Triple Quadropole Mass Spectrometer
Synchrotron SOLEIL facility near Paris
ISIS Pulsed neutron facility hall
SLAC Synchrotron entrance near Stanford, CA
SLAC Detector

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