CONFORMATIONAL STUDIES ON SYNTHETIC POLY-α-AMINO ACIDS: THE HELICAL SENSE OF POLY-L-TRYPTOPHAN: OPTICAL ROTATORY DISPERSION STUDIES

1965 ◽  
Vol 43 (5) ◽  
pp. 1588-1598 ◽  
Author(s):  
Gerald D. Fasman ◽  
Margarete Landsberg ◽  
Manuel Buchwald
Keyword(s):  
Wavelength Range ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Helical Conformation ◽  
Optical Rotatory ◽  
Negative Cotton Effect ◽  
Cotton Effects ◽  
The Right ◽  
Tryptophanyl Residue

The synthesis of high molecular weight (100 000 to 200 000) polymers and copolymers of L-tryptophan and γ-benzyl-L-glutamate is reported. The optical rotatory dispersion (o.r.d.) of these polypeptides is recorded in the wavelength range 540–320 mμ and the b0 values of the Moffitt equation, using λ0 = 212ν, are listed. Poly-L-tryptophan has a b0 value of +570 in dimethylformamide (DMF). A linear relationship exists between this value, b0 values of copolymers of various ratios of L-tryptophan and γ-benzyl-L-glutamate, and the value of− 670 found for poly-γ-benzyl-L-glutamate. The o.r.d. curve of a poly-L-tryptophan film, in the 330–200 mμ wavelength range, reveals two positive Cotton effects in the 270–290 mμ region and a large negative Cotton effect at 233 mμ. Thus, despite the positive b0 value, these data prove that poly-L-tryptophan, in DMF, has the right-handed helical conformation. Hypochromicity was found for the tryptophanyl residue in the helical polypeptide. The rotatory contribution of chromophores, such as tryptophan or coenzymes, when bound asymmetrically to a protein, can be very significant, and caution is advised in the interpretation of such o.r.d. curves.

Some features of the optical rotatory dispersion spectrum of the α-lytic protease of Sorangium sp.

1969 ◽  
Vol 47 (3) ◽  
pp. 317-321 ◽  
Author(s):  
G. M. Paterson ◽  
D. R. Whitaker
Keyword(s):  
Optical Rotation ◽  
Substrate Binding ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Kinetic Properties ◽  
Optical Rotatory ◽  
Cotton Effects ◽  
Ph Dependent

A study of the kinetic properties of the α-lytic protease of Sorangium sp. indicated that substrate-binding by the enzyme was not pH dependent. In agreement with this indication of a pH-insensitive conformation, the optical rotation of the enzyme between pH 5 and 10.5 is not pH dependent. The optical rotatory dispersion spectrum above 220 mμ shows a main Cotton effect with a trough at 230 mμ and small but well-marked Cotton effects between 260 and 300 mμ. The reduced, mean residue rotation at the trough of the main Cotton effect was estimated to be −1650 ± 80° cm2/dmole; the Moffitt–Yang parameter b0 for rotations above 325 mμ is approximately zero. These values suggest that the enzyme has virtually no α-helices.

Optical Rotatory Dispersion and Circular Dichroism Studies on Ocular Lens Proteins

1971 ◽  
Vol 49 (4) ◽  
pp. 426-430 ◽  
Author(s):  
Howard A. Jones ◽  
Sidney Lerman
Keyword(s):  
Circular Dichroism ◽  
Electronic Absorption Spectra ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Helical Conformation ◽  
Optical Rotatory ◽  
Ocular Lens ◽  
Cotton Effects ◽  
Beta Structure ◽  
Circular Dichroïsm

A study has been made of the circular birefringence and circular dichroism of alpha and gamma crystallins obtained from dogfish lenses. The Cotton effects in the optical rotatory dispersion and circular dichroism spectra are correlated with maxima in the electronic absorption spectra. On the basis largely of this correlation, the transitions which give rise to the Cotton effects have been assigned to various chromophores. It is concluded that the secondary structure of these proteins is made up of beta structure and the unordered conformation. Little or no α-helical conformation seems to be present.

The Effect of Ligand Binding on the Optical Rotatory Dispersion of Lactoperoxidase

1971 ◽  
Vol 49 (6) ◽  
pp. 666-670 ◽  
Author(s):  
R. James Maguire ◽  
H. Brian Dunford
Keyword(s):  
Protein Conformation ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Heme Group ◽  
Negative Cotton Effect ◽  
Fluoride Complexes ◽  
Protein Moiety ◽  
Soret Region

The optical rotatory dispersion of lactoperoxidase and its cyanide and fluoride complexes was studied over the spectral region 210–500 nm, and that of the azide complex from 350–450 nm. Results of the measurements of the reduced mean rotation at 233 nm lead to the conclusion that there are no significant changes in gross protein conformation upon the binding of these ligands to lactoperoxidase. Lactoperoxidase was estimated to have 17% α-helical character at pH 7.0. Results of studies in the Soret region indicate that lactoperoxidase, unlike horseradish peroxidase, hemoglobin, and myoglobin, exhibits a negative Cotton effect as do its cyanide, azide, and fluoride complexes. The binding of these ligands apparently causes an alteration of the geometry of the heme group with respect to the protein moiety.

An optical rotatory dispersion study on fibrinogen and some of its derivatives

1968 ◽  
Vol 46 (6) ◽  
pp. 617-620 ◽  
Author(s):  
William D. McCubbin ◽  
Cyril M. Kay
Keyword(s):  
Tertiary Structure ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Tryptic Digestion ◽  
Optical Rotatory ◽  
Molecular Rearrangement ◽  
The Core ◽  
Helical Content ◽  
Cotton Effects ◽  
Fibrinogen Molecule

Visible and ultraviolet optical rotatory dispersion measurements were carried out on native fibrinogen and some of its derivatives. The latter include: (1) desialicized fibrinogen, (2) a large fragment of the fibrinogen molecule produced by short tryptic digestion, (3) fibrin monomer, and (4) intermediate fibrin polymers produced by the controlled thrombin proteolysis of fibrinogen. The α-helical content of native fibrinogen was deduced as 32%, and empirical calculations suggest that there is about 14% β-structure in the molecule. Sialic acid plays no significant role in the maintenance of the secondary and tertiary structure of the native molecule. No major conformational change is associated with the thrombin proteolysis of fibrinogen, although a small increase in helical content (~5%) accompanies the staggered overlap association of fibrin monomers. The "core" resulting from the controlled tryptic digestion of fibrinogen undergoes a molecular rearrangement relative to the native molecule, such that it possesses a lower α-helical content (24%) and a higher β-form value (23%). In addition, some of the additional tyrosines in the core become encompassed in regions of greater asymmetry to give rise to small aromatic Cotton effects centered around 285 mμ.

Alkaloids of Lycopodiumlucidulum Michx. Structure and properties of alkaloid L.23

1969 ◽  
Vol 47 (3) ◽  
pp. 449-455 ◽  
Author(s):  
W. A. Ayer ◽  
B. Altenkirk ◽  
R. H. Burnell ◽  
M. Moinas
Keyword(s):  
Absolute Configuration ◽  
Cotton Effect ◽  
Ultraviolet Spectrum ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Structure And Properties ◽  
The Absolute ◽  
Related Compounds ◽  
Circular Dichroic

The minor alkaloids present among the strong bases of Lycopodiumlucidulum have been reinvestigated. Manske and Marion's alkaloid L.23 has been shown to be epimeric with lycodoline at C-12 and the nitrogen. A correlation between the two alkaloids has been achieved. The presence of a σ-coupled p interaction in the ultraviolet spectrum of lycopodine, lycodoline, and related compounds is described. A Cotton effect due to this chromophore has been detected by means of circular dichroism. The optical rotatory dispersion and circular dichroic properties of lycopodine, 12-epilycopodine, lycodoline, and alkaloid L.23 are discussed in terms of the absolute configuration assigned to these alkaloids.

Sign in / Sign up

Export Citation Format

Share Document