Alpha helix protein structure

Figure 3-2 Secondary Structures of Proteins, (A) Alpha Helix, (B) Antiparallel Sheet...

A few scanning dispersive VCD instruments are still in use for biological applications in the mid-IR region [46,47]. In 2009, a newly designed and optimized dispersive VCD instrument was reported [47]. A collection of spectra for peptides and proteins having different dominant secondary structures (alpha-helix, beta-sheet, and random coil) measured with this new instrument showed substantially improved signal-to-noise (S/N) ratios as compared with the earlier version. The instrument provides protein VCD spectra for the amide I region that are of comparable or better quality than those obtained with a standard commercial FTIR-VCD spectrometer [47]. 

Fibrous proteins Globular proteins Alpha-amino acids Side chains Dipeptide Peptide linkage Polypeptide Primary structure Secondary structure Alpha-helix Pleated sheet Tertiary structure Disulfide linkage Denaturation Enzymes... 

The domain of a protein is determined by its secondary structure. There are four main types of domain structures alpha-helix, beta sheet, beta-turn, and random coil. 

Indicate whether each statement is true or false, (a) The sequence of amino acids in a protein, from the amine end to the acid end, is called the primary structure of the protein, (b) Alpha helix and beta sheet structures are examples of quaternary protein structure, (c) It is impossible for more than one protein to bind to another and make a higher order structure. 

The secondary structure is created by hydrogen bonds between the carbonyl group of one amino acid with the amine group of another. This structure manifests itself as an alpha helix or in a beta sheet. Within one protein, both alpha helixes and beta sheets can occur. 

The method of x-ray diffraction by crystals has been used to determine the detailed structures of a number of globular proteins. The alpha helix and the two pleated sheets have been found to be the main types of secondary structure in these proteins. The location of the catalytically active region of an enzyme can be discovered by the x-ray study of crystals of the enzyme combined with an inhibitor. 

Alpha farnesene, structure of, 207 Alpha helix (protein), 1038 Alpha-keratin, molecular model of, 1039... 

Segrest MP et al The amphipathic alpha-helix A multifunctional structural motif in plasma lipoproteins. Adv Protein Chem... 

The essential distinction between the approaches used to formulate and evaluate proteins, compared with conventional low molecular weight drugs, lies in the need to maintain several levels of protein structure and the unique chemical and physical properties that these higher-order structures convey. Proteins are condensation polymers of amino acids, joined by peptide bonds. The levels of protein architecture are typically described in terms of the four orders of structure [23,24] depicted in Fig. 2. The primary structure refers to the sequence of amino acids and the location of any disulfide bonds. Secondary structure is derived from the steric relations of amino acid residues that are close to one another. The alpha-helix and beta-pleated sheet are examples of periodic secondary structure. Tertiary... 

The N-terminal domain of the OCP is an orthogonal alpha-helical bundle, subdivided into two four-helix bundles (Figure 1.3a and c). These subdomains are composed of discontinuous segments of the polypeptide chain (gray and white in Figure 1.3c). To date, the OCP N-terminal domain is the only known protein structure with this particular fold (Pfam 09150). The hydroxyl terminus of the 3 -hydroxyechinenone is nestled between the two bundles. The C-terminal domain (dark... 

Figure 11.4 The structural hierarchy in proteins, (a) A segment of primary structure (b) secondary structure illustrated as a segment of alpha helix (c) tertiary structure in which helices are interspersed with coils, and (d) quaternary structure. (Illustration, Irving Geis/Geis Archive Trust. Copyright Howard Hughes Medical Institute. Reproduced with permission.)...

Alpha helix one form of secondary structure in proteins in which the polypeptide chain forms a helix having 3.6 amino acid residues per turn. 

Secondary structure those protein structures that result from hydrogen bond formation between the amino and carbonyl groups of peptide bonds. The most important ones are the alpha helix and beta sheets. 

The alpha helix and beta sheets are two types of secondary structures exhibited by polypeptides and proteins. (Rae Dejur)... 

FIGURE 2.2 The alpha (a) helix, showing the pattern of intrachain hydrogen bonds that stabilize the structure, and the radial extension of amino acid side chains from the helix axis. (Adapted from Richardson, J.S. [1981]. The anatomy and taxonomy of protein structure. Advances in Protein Chemistry, 34, 167—339, copyright 1981, with permission from Elsevier Science.)... 

The structure of proteins determines their function and can be described on four levels, illustrated on page 447. The primary structure is the sequence of amino acids in the polypeptide chain. The secondary structure describes how various short portions of a chain are either wrapped into a coil called an alpha helix or folded into a thin pleated sheet. The tertiary structure is the way in which an entire polypeptide chain may either twist into a long fiber or bend into a globular clump. The quaternary structure describes how separate proteins may join to form one larger complex. Each level of structure is determined by the level before it, which means that ultimately it is the sequence of amino acids that creates the overall protein shape. Fhis final shape is maintained both by chemical bonds and by weaker molecular attractions between amino acid side groups. 

The primary stucture of a protein is simply the sequence of amino acids within that protein. These linked amino acids can either curl into an alpha helix or crisscross to form pleated sheets, which are examples of secondary protein structures. The protein chain of amino acids is typically quite long, such that it may have regions of alpha helices and regions of pleated sheets. The larger structure of the protein that includes all the various contours of the whole protein is the tertiary structure. In some instances, two or more tertiary structures will come together to form an even larger complex known as the quaternary structure. 

The alpha helix represents the second major structural element of soluble proteins108 128 and is also found in many fibrous proteins, including those of muscle... 

Figure 25-11 Peptide chain of a protein coiled to form a right-handed alpha helix. Configuration of the helix is maintained by hydrogen bonds, shown as vertical dotted (or solid) lines. The helix on the left shows the detailed atom structure of the peptide chain. The helix on the right is a schematic representation without structural detail. 

Secondary Structure of Proteins The secondary structure of a protein is how the polypeptide chain is twisted. There are two common types of secondary structure the alpha helix and the beta pleated sheet. 

Figure 3.3 The alpha helix is one of the most common secondary structure patterns. Pictured here are (a) the molecular structure of the alpha helix and (b) a protein consisting of several spiraling alpha helices.

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