The hydrogen bonds are formed between the carbonyl oxygen and the amine hydrogen of amino acid in adjacent strands in a polypeptide, which means that the hydrogen bonds are inter-stand. β-sheet regions are more extended than an α-helix, and the distance between adjacent amino acids is 3.5 Å. A section of polypeptide with residues in the beta-conformation is refered to as a beta-strand and these strands can associate by main chain hydrogen bonding interactions to form a beta sheet. In a beta-sheet two or more polypeptide chains run alongside each other and are linked in a regular manner by hydrogen bonds between the main chain C=O and N-H groups. Therefore all hydrogen bonds in a beta-sheet are between different segments of polypeptide. This contrasts with the alpha-helix where ... Alpha helix definition, the rodlike spatial configuration of many protein molecules in which the polypeptide backbone is stabilized by hydrogen bonds between amino acids in successive helical turns. Within a β sheet, as within an α-helix, all possible backbone hydrogen bonds are formed.In both parallel and antiparallel β sheet, the side groups along each strand alternate above and below the sheet, while side groups opposite one another on neighboring strands extend to the same side of the sheet and are quite close together. α-Helix Conformation. The α-helix is a right-handed helix with the peptide bonds located on the inside and the side chains extending outward. It is stabilized by the regular formation of hydrogen bonds parallel to the axis of the helix; they are formed between the amino and carbonyl groups of every fourth peptide bond.

It does this by changing some of the alpha helices, which are more common in normal cells, to beta sheets, which are more common in prions. The alpha helix consists of 3.6 residues per turn. All hydrogen bonds face in the same direction. If two or more alpha helices come together, they become a tertiary structure. (Ex. The hydrogen bonds are formed between the carbonyl oxygen and the amine hydrogen of amino acid in adjacent strands in a polypeptide, which means that the hydrogen bonds are inter-stand. β-sheet regions are more extended than an α-helix, and the distance between adjacent amino acids is 3.5 Å.

bonds) between the carbonyl oxygen and amide hydrogens within the alpha helix and between beta sheets. The alpha helix and the beta sheet are the only conformations whose dihedral angles fall within the allowed values of φ & ψ as determined by the Ramachandran diagram and allow for favorable hydrogen bond formation. The alpha helix has torsion angles of φ = -570 and ψ= -470: parallel beta sheets have angles of Hydrogen bonds in beta sheets are on average 0.1 Angstrom shorter than those found in alpha helices (Baker & Hubbard, 1984). Figure 8. The protein thioredoxin (2TRX.PDB) contains a five-stranded beta sheet comprised of three parallel strands and three antiparallel strands. The nature of the hydrogen bonds is the same as for an alpha helix - that is, the imino group of one peptide bond bonded to the carbonyl group of another peptide bond. The two peptide bonds involved can be between amino acids far apart in the primary sequence but brought together in the overall folding of the polypeptide. Alpha helix definition, the rodlike spatial configuration of many protein molecules in which the polypeptide backbone is stabilized by hydrogen bonds between amino acids in successive helical turns. Helix-capping motifs are specific patterns of hydrogen bonding and hydrophobic interactions found at or near the ends of helices in both proteins and peptides. In an alpha-helix, the first four >N-H groups and last four >C=O groups necessarily lack intrahelical hydrogen bonds.

alpha helix structure. coiled- right handed coil stabilized by hydrogen bonds between the carbonyl oxygen of one aa and the N-H hydrogen atom of another aa located 4 aa from it in the primary structure. -strong and able to stretch and recoil (telephone) -the side chains project outward from the axis of the helix. In structures that have beta sheets and alpha helices, one common fold is a single beta sheet that is sandwiched by layers of alpha helices on either side (for example Carboxypeptidase A). When an alpha helix runs along the surface of the protein, one side of it will show polar side chains (solvent accessible) while the other side will show non ... Hydrogen bonds in beta sheets are on average 0.1 Angstrom shorter than those found in alpha helices (Baker & Hubbard, 1984). Figure 8. The protein thioredoxin (2TRX.PDB) contains a five-stranded beta sheet comprised of three parallel strands and three antiparallel strands.

forms of beta sheet. The difference is in the relative direction of neighboring strands and in the way they hydrogen bond. Either way, just as an alpha helix, a beta sheet satisfies all hydrogen bonds of a peptide backbone. The only hydrogen bonds left un-bonded are those at the edges of the sheet. Post by Sam Zanone on September 18, 2014. Professor Hovasapian: Out of curiosity, could you possibly elaborate on 3D Structures of Proteins? The Alpha Helix and Beta Sheet explanations are perfect, but our homework continually refers back to peptide chains, asking about which bonds join together to form Hydrogen bonds. Alpha-helices and beta-sheets are the two key secondary structure elements found in proteins (visit the Protein Structural Levels tutorial for more information on secondary structure). Alpha-Helices Alpha-helices are formed by hydrogen bonding amino acids via their carbonly carbons and amide protons. The Alpha Helix Is a Coiled Structure Stabilized by Intrachain Hydrogen Bonds In evaluating potential structures, Pauling and Corey considered which conformations of peptides were sterically allowed and which most fully exploited the hydrogen-bonding capacity of the backbone NH and CO groups. The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-spiral conformation (i.e. helix) in which every backbone N−H group donates a hydrogen bond to the backbone C=O group of the amino acid located three or four residues earlier along the protein sequence. associated with the plane rotation about the N--Cα bond. Ψ characterizes the conformation of the peptide plane at the carboxyl end of the Cα atom – this angle is associated with the peptide plane rotation about the Cα--C’ bond. (2) (5 pts) What groups are connected by the hydrogen bonds in the α-helix and in the β-sheet? bonds) between the carbonyl oxygen and amide hydrogens within the alpha helix and between beta sheets. The alpha helix and the beta sheet are the only conformations whose dihedral angles fall within the allowed values of φ & ψ as determined by the Ramachandran diagram and allow for favorable hydrogen bond formation. The alpha helix has torsion angles of φ = -570 and ψ= -470: parallel beta sheets have angles of

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In the alpha-helix structure, the polypeptide curls longitudinally by the action of hydrogen bonds forming a spiral, or helix. In the beta-sheet conformation, the protein is more distended and the hydrogen bonds form a zig-zag-shaped proteinstructure called B-strand. Many assembled beta-strands make a beta-sheet. A section of polypeptide with residues in the beta-conformation is refered to as a beta-strand and these strands can associate by main chain hydrogen bonding interactions to form a beta sheet. In a beta-sheet two or more polypeptide chains run alongside each other and are linked in a regular manner by hydrogen bonds between the main chain C=O and N-H groups. Therefore all hydrogen bonds in a beta-sheet are between different segments of polypeptide. This contrasts with the alpha-helix where ... Beta sheets consist of beta strands (also β-strand) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation. Beta-Sheets Although beta-sheets also contain hydrogen bonds between residues, the bonds in beta sheets are interstrand rather than intrastrand as in the case of a helix. In beta sheets hydrogen bonds exist between the residues of two separate beta strands. In beta-strands the phi and psi angles are about -150 and 150 degrees respectively. The most common secondary structures are alpha helices and beta sheets. Other helices, such as the 3 10 helix and π helix, are calculated to have energetically favorable hydrogen-bonding patterns but are rarely observed in natural proteins except at the ends of α helices due to unfavorable backbone packing in the center of the helix. The most common secondary structures are alpha helices and beta sheets. Other helices, such as the 3 10 helix and π helix, are calculated to have energetically favorable hydrogen-bonding patterns but are rarely observed in natural proteins except at the ends of α helices due to unfavorable backbone packing in the center of the helix.

Hydrogen bonds in alpha helix and beta sheet conformation

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associated with the plane rotation about the N--Cα bond. Ψ characterizes the conformation of the peptide plane at the carboxyl end of the Cα atom – this angle is associated with the peptide plane rotation about the Cα--C’ bond. (2) (5 pts) What groups are connected by the hydrogen bonds in the α-helix and in the β-sheet? The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-spiral conformation (i.e. helix) in which every backbone N−H group donates a hydrogen bond to the backbone C=O group of the amino acid located three or four residues earlier along the protein sequence. forms of beta sheet. The difference is in the relative direction of neighboring strands and in the way they hydrogen bond. Either way, just as an alpha helix, a beta sheet satisfies all hydrogen bonds of a peptide backbone. The only hydrogen bonds left un-bonded are those at the edges of the sheet. Beta sheets consist of beta strands (also β-strand) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation.