Side view of an α-helix of alanine residues in atomic detail. Two hydrogen bonds to the same peptide group are highlighted in magenta; the oxygen-hydrogen distance is 2.08 Å (208 pm). The protein chain runs upwards, i.e., its N-terminus is at the bottom and its C-terminus at the top of the figure. Note that the sidechains point slightly downwards, i.e., towards the N-terminus.

A common motif in the secondary structure of proteins, the alpha helix (α-helix) is a right-handed coiled conformation, resembling a spring, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier ( hydrogen bonding). (See also helix.) Image File history File links Download high-resolution version (801x1188, 176 KB) Close-up sideview of a stick model of an alpha helix of poly-alanine using the dihedral angles φ=-60° and ψ=-45° and the Engh&Huber bond geometry. ... Image File history File links Download high-resolution version (801x1188, 176 KB) Close-up sideview of a stick model of an alpha helix of poly-alanine using the dihedral angles φ=-60° and ψ=-45° and the Engh&Huber bond geometry. ... Alanine (Ala, A) also 2-aminopropanoic acid is a non-essential α-amino acid. ... Properties For other meanings of Atom, see Atom (disambiguation). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A representation of the 3D structure of the myoglobin protein. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... For other uses, see Spring. ... In chemistry, especially in organic chemistry and biochemistry, an amino group is an ammonia-like functional group. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... This article is about the class of chemicals. ... A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ...

Historical development

In the early 1930s, William Astbury showed that there were drastic changes in the X-ray fiber diffraction of moist wool or hair fibers upon significant stretching. The data suggested that the unstretched fibers had a coiled molecular structure with a characteristic repeat of ~5.1 Å (= 0.51 nm). Astbury proposed that (1) the unstretched protein molecules formed a helix (which he called the α-form); and (2) the stretching caused the helix to uncoil, forming an extended state (which he called the β-form). Although incorrect in their details, Astbury's models of these forms were correct in essence and correspond to modern elements of secondary structure, the α-helix and the β-strand (Astbury's nomenclature was kept), which were developed by Linus Pauling, Robert Corey and Herman Branson in 1951 (see below). Hans Neurath was the first to show that Astbury's models could not be correct in detail, because they involved clashes of atoms.^[1] Interestingly, Neurath's paper and Astbury's data inspired H. S. Taylor,^[2] Maurice Huggins^[3] and Bragg and collaborators^[4] to propose models of keratin that resemble the modern α-helix. William Astbury (1898-1961) was an English biochemist who made X-ray diffraction studies of nucleic acid in 1937. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Fiber diffraction is a scattering technique in which molecular structure is determined from scattering data (usually of X-rays or electrons) from filaments composed of a regular array of molecules distinguished by a single direction (the fiber axis). ... A representation of the 3D structure of the myoglobin protein. ... Linus Carl Pauling (February 28, 1901 – August 19, 1994) was an American quantum chemist and biochemist. ... Robert Corey (August 19, 1897 – April 23, 1971) is a little known scientist, mostly known for his helping Linus Pauling discover the α-helix and the β-sheet in the spring of 1951. ... Herman Russell Branson (August 14, 1914 - June 7, 1995) was an African American physicist, best known for his research on protein structure. ... Hans Neurath (1909- 12 April 2002) was an early protein scientist. ... Hugh Stott Taylor (6 February 1890 - 17 April 1974) was an English chemist primarily interested in catalysis. ... Maurice Loyal Huggins (19 September 1897- 17 December 1981) was a scientist who independently conceived the idea of hydrogen bonding and who was an early advocate for their role in stabilizing protein secondary structure. ... Sir William Lawrence Bragg CH, FRS, (31 March 1890 – 1 July 1971) was an Australian physicist who shared the Nobel Prize in Physics in 1915 with his father Sir William Henry Bragg. ...

Two key developments in the modeling of the modern α-helix were (1) the correct bond geometry, thanks to the crystal structure determinations of amino acids and peptides and Pauling's prediction of planar peptide bonds; and (2) the relinquishing of the assumption of an integral number of residues per turn of the helix. The pivotal moment came in January 1948, when Pauling caught a cold and went to bed. Being bored, he drew a polypeptide chain of roughly correct dimensions on a strip of paper and folded it into a helix, being careful to maintain the planar peptide bonds. After a few attempts, he produced a model with physically plausible hydrogen bonds. Pauling then worked with Corey and Branson to confirm his model before publication.^[5] Crystallography (from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ... This article is about the class of chemicals. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ...

Structure

Geometry and hydrogen bonding

Top view of the same helix shown above. Four carbonyl groups are pointing upwards towards the viewer, spaced roughly 100° apart on the circle, corresponding to 3.6 amino-acid residues per turn of the helix.

The amino acids in an α helix are arranged in a right-handed helical structure, 5.4 Å (= 0.54 nm) wide. Each amino acid corresponds to a 100° turn in the helix (i.e., the helix has 3.6 residues per turn), and a translation of 1.5 Å (= 0.15 nm) along the helical axis. Most importantly, the N-H group of an amino acid forms a hydrogen bond with the C=O group of the amino acid four residues earlier; this repeated hydrogen bonding defines an α-helix. Similar structures include the 3₁₀ helix ( hydrogen bonding) and the π-helix ( hydrogen bonding). These alternative helices are relatively rare, although the 3₁₀ helix is often found at the ends of α-helices, "closing" them off. Transient helices (sometimes called δ-helices) have also been reported as intermediates in molecular dynamics simulations of α-helical folding. Image File history File links Alpha_helix_neg60_neg45_topview. ... Image File history File links Alpha_helix_neg60_neg45_topview. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... This article is about the class of chemicals. ... A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... Molecular dynamics (MD) is a form of computer simulation wherein atoms and molecules are allowed to interact for a period of time under known laws of physics, giving a view of the motion of the atoms. ...

Residues in α-helices typically adopt backbone (φ, ψ) dihedral angles around (-60°, -45°). More generally, they adopt dihedral angles such that the ψ dihedral angle of one residue and the φ dihedral angle of the next residue sum to roughly -105°. Consequently, α-helical dihedral angles generally fall on a diagonal stripe on the Ramachandran plot (of slope -1), ranging from (-90°, -15°) to (-35°, -70°). For comparison, the sum of the dihedral angles for a 3₁₀ helix is roughly -75°, whereas that for the π-helix is roughly -130°. The general formula for the rotation angle Ω per residue of any polypeptide helix with trans isomers is given by the equation^{[citation needed]} In Aerospace engineering, the dihedral is the angle that the two wings make with each other. ... In Aerospace engineering, the dihedral is the angle that the two wings make with each other. ... In Aerospace engineering, the dihedral is the angle that the two wings make with each other. ... A Ramachandran plot generated from the protein PCNA, a human DNA clamp protein that is composed of both beta sheets and alpha helices (PDB ID 1AXC). ...

The α-helix is tightly packed; there is almost no free space within the helix. The amino-acid side chains are on the outside of the helix, and point roughly "downwards" (i.e., towards the N-terminus), like the branches of an evergreen tree (Christmas tree effect). This directionality is sometimes used in preliminary, low-resolution electron-density maps to determine the direction of the protein backbone. For other uses, see Christmas tree (disambiguation). ...

Definition of the helical axis

Several definitions of the helical axis have been proposed, of which the Sugeta-Miyazawa definition is the simplest and most general. These definitions are equivalent if every residue of the helix has exactly the same bond geometry and dihedral angles. However, the definitions exhibit different sensitivities to fluctuations in these parameters.

Stability

Helices observed in proteins can range from four to over forty residues long, but a typical helix contains about ten amino acids (about three turns). Short polypeptides generally do not exhibit much alpha helical structure in solution, since the entropic cost associated with the folding of the polypeptide chain is not compensated by sufficiently many stabilizing interactions. The backbone hydrogen bonds of α-helices are generally considered slightly weaker than those found in β-sheets, and are readily attacked by the ambient water molecules. However, in more hydrophobic environments such as the plasma membrane, or in the presence of co-solvents such as trifluoroethanol (TFE), oligopeptides readily adopt stable α-helical structure. Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... For other uses, see: information entropy (in information theory) and entropy (disambiguation). ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... Diagram of β-pleated sheet with H-bonding between protein strands The β sheet (also β-pleated sheet) is the second form of regular secondary structure in proteins — the first is the alpha helix — consisting of beta strands connected laterally by three or more hydrogen bonds, forming a generally twisted, pleated sheet. ... Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... 2,2,2-Trifluoroethanol (TFE) or trifluoroethyl alcohol is a trifluoro substituted alcohol. ...

Experimental determination

Since the α-helix is defined by its hydrogen bonds, the most reliable experimental methods for determining an α-helix involve an atomic-resolution structure provided by X-ray crystallography or NMR spectroscopy. In some cases, the individual hydrogen bonds can be observed directly as a small scalar coupling in NMR. X-ray crystallography, also known as single-crystal X-ray diffraction, is the oldest and most common crystallographic method for determining the structure of molecules. ... Pacific Northwest National Laboratorys high magnetic field (800 MHz) NMR spectrometer being loaded with a sample. ...

There are several lower-resolution methods for assigning general helical structure. The NMR chemical shifts (particularly of the C^α, C^β and C' atoms) and residual dipolar couplings are often characteristic of helices. The far-UV (170-250 nm) circular dichroism spectrum of helices is also idiosyncratic, exhibiting a pronounced double minimum at ~208 nm and ~222 nm. Infrared spectroscopy is rarely used, since the α-helical spectrum resembles that for random coil (although these might be discerned by, e.g., hydrogen-deuterium exchange). Finally, cryo electron microscopy is now capable of discerning individual α-helices within a protein, although their assignment to residues is still an active area of research. Pacific Northwest National Laboratorys high magnetic field (800 MHz) NMR spectrometer being loaded with a sample. ... In nuclear magnetic resonance (NMR), the chemical shift describes the dependence of nuclear magnetic energy levels on the electronic environment in a molecule. ... The residual dipolar coupling between two spins in a molecule occurs if the molecules in solution exhibit a partial alignment leading to an incomplete averaging of spatially anisotropic dipolar couplings. ... Circular dichroism (CD) is a form of spectroscopy based on the differential absorption of left- and right-handed circularly polarized light. ... For other uses, see Infrared (disambiguation). ... Illustration of a 3-dimensional polypeptide A random coil is a polymer conformation where the monomer subunits are oriented randomly while still being bonded to adjacent units. ... Hydrogen-deuterium exchange (also called H-D or H/D exchange) is a chemical reaction in which a covalently bonded hydrogen atom is replaced by a deuterium atom, or vice versa. ... The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons rather than light to scatter off material, magnifying at levels up to 500,000 times. ...

Long homopolymers of amino acids often form helices (if soluble). Such long, isolated helices can also be detected by other methods, such as dielectric relaxation, flow birefringence and measurements of its diffusion constant. Strictly speaking, these methods only detect the characteristic prolate (long cigar-like) hydrodynamic shape of a helix, or its large dipole moment. In physics, dielectric relaxation refers to the relaxation reponse of a dielectric medium to an external field of microwave frequencies. ... In biochemistry, flow birefringence is a hydrodynamic technique for measuring the rotational diffusion constants (or, equivalently, the rotational drag coefficients]]. The birefringence of a solution sandwiched between two concentric cylinders is measured as a function of the difference in rotational speed between the iner and outer cylinders. ... Ficks laws of diffusion describe diffusion, and define the diffusion coefficient D. // History Ficks laws of diffusion were derived by Adolf Fick in the year 1855. ... A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ... Dipole moment refers to the quality of a system to behave like a dipole. ...

Amino-acid propensities

Different amino-acid sequences have different propensities for forming α-helical structure. Methionine, alanine, leucine, glutamate, and lysine ("MALEK" in the amino-acid 1-letter codes) all have especially high helix-forming propensities, whereas proline, glycine, tyrosine and serine have poor helix-forming propensities. Proline tends to break or kink helices because it cannot donate an amide hydrogen bond (having no amide hydrogen), and because its sidechain interferes sterically; its ring structure also restricts its backbone φ dihedral angle to the vicinity of -70°, which is less common in α-helices. However, proline is often seen as the first residue of a helix, presumably due to its structural rigidity. At the other extreme, glycine also tends to disrupt helices because its high conformational flexibility makes it entropically expensive to adopt the relatively constrained α-helical structure. Methionine is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CH2SCH3. ... Alanine (Ala, A) also 2-aminopropanoic acid is a non-essential α-amino acid. ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... Glutamate is the anion of glutamic acid. ... Lysine is one of the 20 amino acids normally found in proteins. ... This article is about the class of chemicals. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... For the plant, see Glycine (plant). ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... In Aerospace engineering, the dihedral is the angle that the two wings make with each other. ... For the plant, see Glycine (plant). ...

Dipole moment

A helix has an overall dipole moment caused by the aggregate effect of all the individual dipoles from the carbonyl groups of the peptide bond pointing along the helix axis. This can lead to destabilization of the helix through entropic effects. As a result, α helices are often capped at the N-terminal end by a negatively charged amino acid, such as glutamic acid, in order to neutralize this helix dipole. Less common (and less effective) is C-terminal capping with a positively charged amino acid, such as lysine. The N-terminal positive charge is commonly used to bind negatively charged ligands such as phosphate groups, which is especially effective because the backbone amides can serve as hydrogen bond donors. Dipole moment refers to the quality of a system to behave like a dipole. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... This article is about the class of chemicals. ... Glutamic acid (Glu, E), is the protonated form of glutamate (the anion). ... Lysine is one of the 20 amino acids normally found in proteins. ...

Larger-scale assemblies

Myoglobin, the first protein whose structure was solved by X-ray crystallography, is made up of about 70% α helix, with the rest being loops or disordered regions. In classifying proteins by their dominant fold, the Structural Classification of Proteins database maintains a category specifically for all-α proteins. An X-ray diffraction image for the protein myoglobin. ... Crystallography (from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ...

Coiled-coil α helices are highly stable forms in which two or more helices wrap around each other in a "supercoil" structure. Coiled coils contain a highly characteristic sequence motif known as a heptad repeat, in which the motif repeats itself every seven residues along the sequence. The first and especially the fourth residues (known as the a and h positions) are almost always hydrophobic (the fourth residue is typically leucine) and pack together in the interior of the helix bundle. The fifth and seventh residues (the e and g positions) generally have opposing charges and form a salt bridge stabilized by electrostatic interactions. Fibrous proteins such as keratin and myosin often adopt coiled-coil structures, as do several dimerizing proteins. A pair of coiled-coils - a four-helix bundle - is a very common structural motif in proteins. For example, it occurs in human growth hormone and several varieties of cytochrome. The Rop protein, which promotes plasmid replication in bacteria, is an interesting case in which a single polypeptide forms a coiled-coil and two monomers assemble to form a four-helix bundle. A coiled coil is a structural motif found in many proteins. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... Electrostatics is the branch of physics that deals with the force exerted by a static (i. ... Fibrous proteins, also called scleroproteins, are long filamentous protein molecules that form one of the two main classes of tertiary structure protein (the other being globular proteins). ... A helix bundle is a small protein fold composed of three or four alpha helices and held together by nonlocal hydrophobic interactions. ... Growth hormone (GH) or somatotropin (STH) is a protein hormone which stimulates growth and cell reproduction in humans and other animals. ... Cytochromes are generally membrane-bound proteins that contain heme groups and carry out electron transport or catalyse reductive/oxidative reactions. ...

The amino acids that make up a particular helix can be plotted on a helical wheel, a representation that illustrates the orientations of the constituent amino acids. Often in globular proteins, as well as in specialized structures such as coiled-coils and leucine zippers, an alpha helix will exhibit two "faces" - one containing predominantly hydrophobic amino acids oriented toward the interior of the protein, in the hydrophobic core, and one containing predominantly polar amino acids oriented toward the solvent-exposed surface of the protein. An example of an amino acid sequence plotted on a helical wheel. ... 3-dimensional structure of hemoglobin, a globular protein. ... Overhead view, or helical wheel diagram, of a leucine zipper, where d represent amino acid leucine , arranged with other amino acids on two parallel alpha helices. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... The hydrophobic effect is the property that nonpolar molecules like to self-associate in the presence of aqueous solution. ... A commonly-used example of a polar compound is water (H2O). ... For other uses, see Solvent (disambiguation). ...

Functional roles

α helices have particular significance in DNA binding motifs, including helix-turn-helix motifs, leucine zipper motifs and zinc finger motifs. This is because of the convenient structural fact that the diameter of the α helix is 1.2 nanometres, the same as the width of the major groove in B-form DNA. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... The λ repressor of bacteriophage lambda employs a helix-turn-helix to bind DNA. In proteins, the helix-turn-helix (HTH) is a major structural motif capable of binding DNA. It is composed of two α helices joined by a short strand of amino acids and is found in many... Overhead view, or helical wheel diagram, of a leucine zipper, where d represent amino acid leucine , arranged with other amino acids on two parallel alpha helices. ... Cartoon representation of the protein Zif268 (blue) containing three zinc fingers in complex with DNA (orange). ... This article is about the unit of length. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ...

Helix-coil transition

Homopolymers of amino-acids (such as poly-lysine) can adopt α-helical structure at low temperature that is "melted out" at high temperatures. This helix-coil transition was once thought to be analogous to protein denaturation. The statistical mechanics of this transition can be modeled using an elegant transfer matrix method, characterized by two parameters: the propensity to initiate a helix and the propensity to extend a helix. Lysine (abbreviated as Lys or K)[1] is an α-amino acid with the chemical formula HO2CCH(NH2)(CH2)4NH2. ... Irreversible egg protein denaturation and loss of solubility, caused by the high temperature (while cooking it) Denaturation is the alteration of a protein or nucleic acids shape through some form of external stress (for example, by applying heat, acid or alkali), in such a way that it will no... Statistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force. ... The transfer matrix is a formulation in terms of a matrix of the two-scale equation, which characterizes refinable functions. ...

The α-helix in fine art

At least two artists have made explicit reference to the α-helix in their work, Julie Newdoll in painting and Julian Voss-Andreae in sculpture.

Bay-Area artist Julie Newdoll, who holds a degree in Microbiology, and a minor in art, has specialized in paintings inspired by microscopic images and molecules since 1990. Her painting "Rise of the Alpha Helix" (2003) features human figures arranged in an α helical arrangement. According to the artist, "the flowers reflect the various types of sidechains that each amino acid holds out to the world".

Julian Voss-Andreae's Alpha Helix for Linus Pauling (2004), powder coated steel, height 10' (3 m). The sculpture stands in front of Pauling's childhood home on 3945 SE Hawthorne Boulevard in Portland (Ore., USA).

Julian Voss-Andreae is a German-born sculptor with degrees in experimental physics and sculpture. Since 2001 Voss-Andreae creates "protein sculptures"^[6] based on protein structure with the α-helix being one of his preferred objects. Voss-Andreae has made α-helix sculptures from diverse materials including bamboo and whole trees. A monument Voss-Andreae created in 2004 to celebrate the memory of Linus Pauling, the discoverer of the α-helix, is fashioned from a large steel beam rearranged in the structure of the α-helix. The 10' (3 m) tall, bright-red sculpture stands in front of Pauling's childhood home in Portland, Oregon. Image File history File links Size of this preview: 414 × 600 pixelsFull resolution (530 × 768 pixels, file size: 175 KB, MIME type: image/jpeg) Artist: Julian Voss-Andreae Shown sculpture: Alpha Helix for Linus Pauling (2004), height 10 (3 m), powder-coated steel, location: 3945 SE Hawthorne Blvd, Portland, OR... Image File history File links Size of this preview: 414 × 600 pixelsFull resolution (530 × 768 pixels, file size: 175 KB, MIME type: image/jpeg) Artist: Julian Voss-Andreae Shown sculpture: Alpha Helix for Linus Pauling (2004), height 10 (3 m), powder-coated steel, location: 3945 SE Hawthorne Blvd, Portland, OR... Linus Carl Pauling (February 28, 1901 – August 19, 1994) was an American quantum chemist and biochemist. ... Nickname: Location of Portland in Multnomah County and the state of Oregon Coordinates: , Country State Counties Multnomah County Incorporated February 8, 1851 Government  - Mayor Tom Potter[1]  - Commissioners Sam Adams Randy Leonard Dan Saltzman Erik Sten  - Auditor Gary Blackmer Area  - Total 376. ...

See also

• Folding (chemistry)
• β sheet
• collagen helix
• poly-Pro helix
• secondary structure
• tertiary structure
• Davydov soliton

Crystal structure of a foldamer reported by Lehn and coworkers in Helv. ... Diagram of β-pleated sheet with H-bonding between protein strands The β sheet (also β-pleated sheet) is the second form of regular secondary structure in proteins — the first is the alpha helix — consisting of beta strands connected laterally by three or more hydrogen bonds, forming a generally twisted, pleated sheet. ... In collagen, the collagen helix is a major shape in quaternery structure. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... A representation of the 3D structure of the myoglobin protein. ... In biochemistry and chemistry, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates. ... Side view of an α-helix of alanine residues in atomic detail. ...

References and footnotes

Hans Neurath (1909- 12 April 2002) was an early protein scientist. ... Hugh Stott Taylor (6 February 1890 - 17 April 1974) was an English chemist primarily interested in catalysis. ... Maurice Loyal Huggins (19 September 1897- 17 December 1981) was a scientist who independently conceived the idea of hydrogen bonding and who was an early advocate for their role in stabilizing protein secondary structure. ... Sir William Lawrence Bragg CH, FRS, (31 March 1890 – 1 July 1971) was an Australian physicist who shared the Nobel Prize in Physics in 1915 with his father Sir William Henry Bragg. ... This article or section does not cite its references or sources. ... Max Ferdinand Perutz, OM (May 19, 1914 – February 6, 2002) was an Austrian-British molecular biologist. ... Linus Carl Pauling (February 28, 1901 – August 19, 1994) was an American quantum chemist and biochemist. ... Robert Corey (August 19, 1897 – April 23, 1971) is a little known scientist, mostly known for his helping Linus Pauling discover the α-helix and the β-sheet in the spring of 1951. ... Herman Russell Branson (August 14, 1914 - June 7, 1995) was an African American physicist, best known for his research on protein structure. ...

Additional references

• Carl Branden and John Tooze. 1999. Introduction to Protein Structure 2nd ed. Garland Publishing: New York, NY.

• David Eisenberg, "The discovery of the α-helix and β-sheet, the principal structural features of proteins". Proceedings of the National Academy of Sciences USA. (2003). 100:11207-11210. http://www.pnas.org/cgi/content/full/100/20/11207

• John Kendrew et al. 1960. The structure of myoglobin: a three-dimensional Fourier synthesis and 2Â resolution. Nature 185: 422-7.

• Astbury WT and Woods HJ. (1931) "The Molecular Weights of Proteins", Nature, 127, 663-665.

• Astbury WT and Street A. (1931) "X-ray studies of the structures of hair, wool and related fibres. I. General", Trans. R. Soc. Lond., A230, 75-101.

• Astbury WT. (1933) "Some Problems in the X-ray Analysis of the Structure of Animal Hairs and Other Protein Fibers", Trans. Faraday Soc., 29, 193-211.

• Astbury WT and Woods HJ. (1934) "X-ray studies of the structures of hair, wool and related fibres. II. The molecular structure and elastic properties of hair keratin", Trans. R. Soc. Lond., A232, 333-394.

• Astbury WT and Sisson WA. (1935) "X-ray studies of the structures of hair, wool and related fibres. III. The configuration of the keratin molecule and its orientation in the biological cell", Proc. R. Soc. Lond., A150, 533-551.

• Neurath H. (1940) "Intramolecular folding of polypeptide chains in relation to protein structure", J. Phys. Chem., 44, 296-305.

• Taylor HS. (1942) "Large molecules through atomic spectacles", Proc. Am. Philos. Soc., 85, 1-12.

• Huggins M. (1943) "The structure of fibrous proteins", Chem. Rev., 32, 195-218.

• Bragg L, Kendrew JC and Perutz MF. (1950) "Polypeptide chain configurations in crystalline proteins", Proc. Roy. Soc., A203, 321.

• Pauling L, Corey RB and Branson HR. (1951) "The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain", Proc. Nat. Acad. Sci. Wash., 37, 205.

• Sugeta H and Miyazawa T. (1967) "General Method for Calculating Helical Parameters of Polymer Chains from Bond Lengths, Bond Angles, and Internal-Rotation Angles", Biopolymers, 5, 673-679.

• Wada A. (1976) "The α-helix as an electric macro-dipole", Adv. Biophys., 9, 1-63.

• Chothia C, Levitt M and Richardson D. (1977) "Structure of proteins:Packing of α-helices and pleated sheets", Proceedings of the National Academy of Science USA, 74, 4130-4134.

• Chothia C, Levitt M and Richardson D. (1981) "Helix to Helix Packing in Proteins", Journal of Molecular Biology, 145, 215-250.

• Hol WGJ. (1985) "The role of the α-helix dipole in protein function and structure", Prog. Biophys. Mol. Biol., 45, 149-195.

• Barlow DJ and Thornton JM. (1988) "Helix Geometry in Proteins", J. Mol. Biol., 201, 601-619.

• Murzin AG and Finkelstein AV. (1988) "General architecture of the α-helical globule", Journal of Molecular Biology, 204, 749-769.

The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences. ...

External links

• Interactive model of an α-helix
• Animated details of α-helix
• Artist Julie Newdoll's website
• Artist Julian Voss-Andreae's website