Optical Rotatory Dispersion. Its Application to Protein Conformation.
01 Jan 1962-pp 325-335
TL;DR: Optical rotation has been found to be one of the most convenient methods of following the denaturation of proteins and rotatory dispersion is capable of providing information on the folding of the polypeptide chain in proteins and the changes accompanying denaturation.
Abstract: Optical rotation has been found to be one of the most convenient methods of following the denaturation of proteins. Generally speaking denaturation can be defined as a process or sequence of processes in which the spatial arrangement of the polypeptide chains within the molecule is changed from that typical of the native protein to a more disordered arrangement (Kauzmann 1959). The terms “configuration”, “conformation” and “state of folding” are widely used for spatial arrangement. It is probably best to follow the suggestion of Blout (1960) and restrict the use of “configuration” to its original sense, i.e. the spatial arrangement around an asymmetric carbon atom, and to use “conformation” for the shape of the molecule in its entirety. The properties discussed in the previous Chapter i.e., viscosity, diffusion, sedimentation, and light scattering — can all furnish information on the overall shape of proteins or other macromolecules and changes in this shape with environment. Thus Doty, Bradbury and Holtzer (1956) were able to show using these methods, together with streaming birefringence, that poly-γ-benzyl-L-glutamate could exist in two conformations, the α-helix and the solvated randomly coiled form, depending on the solvent. The change from α-helix to random coil was accompanied by marked changes in the optical rotatory properties of the polypeptides. It is to be expected that an α-helical structure should contribute to the rotatory power of a polypeptide since helices are asymmetric and not superimposable on their mirror images. The work on polypeptides has shown that rotatory dispersion is capable of providing information on the folding of the polypeptide chain in proteins and the changes accompanying denaturation.
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TL;DR: The chapter reviews that the denaturation is a process in which the spatial arrangement of the polypeptide chains within the molecule is changed from that typical of the native protein to a more disordered arrangement.
Abstract: Publisher Summary This chapter explores that the changes that take place in the protein molecules during denaturation constitute one of the most interesting and complex classes of reactions that can be found either in nature or in the laboratory These reactions are important because of the information they can provide about the more intimate details of protein structure and function They are also significant because they challenge the chemist with a difficult area for the application of chemical principles The chapter reviews that the denaturation is a process in which the spatial arrangement of the polypeptide chains within the molecule is changed from that typical of the native protein to a more disordered arrangement The chapter also discusses the classification of protein structures: primary, secondary, and tertiary structures The primary structure is that expressed by the structural chemical formula and depends entirely on the chemical valence bonds that the classical organic chemist would write down for the protein molecule The secondary structure is the configuration of the polypeptide chain that results from the satisfaction of the hydrogen bonding potential between the peptide N-H and C=O groups The tertiary structure is the pattern according to which the secondary structures are packed together within the native protein molecule The term “denaturation” as used in this chapter is indented to include changes in both the secondary and tertiary structures
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TL;DR: In this paper, it was shown that for every transition in its individual residues, a helix has two transitions whose moments are respectively parallel and perpendicular to the screw axis, and that the largest contributions to the rotational strengths of these bands are equal and opposite in the two cases.
Abstract: It is shown that for every transition in its individual residues, a helix has two transitions whose moments are respectively parallel and perpendicular to the screw axis. The largest contributions to the rotational strengths of these bands are equal and opposite in the two cases. As a result, their net effect on the optical activity contains a term proportional to the interval between the two upper states. This term shows abnormal dispersion and its magnitude and sign are more easily interpreted than any other component of the rotatory power.
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