Optical rotatory dispersion studies. CXIX. Effect of ring heteroatomms on the Cotton effect of cyclohexanones

1973 ◽  
Vol 95 (11) ◽  
pp. 3678-3686 ◽  
Author(s):  
Michael M. Cook ◽  
Carl. Djerassi
Keyword(s):  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory

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.

Analysis of Cotton-effect distribution of optical rotatory dispersion for polypeptides in solution

1970 ◽  
Vol 7 (1) ◽  
pp. 8-16 ◽  
Author(s):  
S. Sugai ◽  
K. Nitta ◽  
M. Ishikawa
Keyword(s):  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory

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.

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.

scholarly journals Oligonucleotide studies. Optical rotatory dispersion of five homodinucleotides

1969 ◽  
Vol 113 (5) ◽  
pp. 843-851 ◽  
Author(s):  
Yasuo Inoue ◽  
Kimihiko Satoh
Keyword(s):  
Ionic Strength ◽  
Salt Concentration ◽  
Equilibrium Mixture ◽  
Cotton Effect ◽  
Phosphate Group ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Ionization State ◽  
Terminal Phosphate Group

1. The optical rotatory dispersion (ORD) of five homodinucleotides, ApAp(3′), CpCp(3′), GpGp(3′), IpIp(3′) and UpUp(3′) (where A, C, G, I and U represent adenosine, cytidine, guanosine, inosine and uridine respectively, and p to the left of a nucleoside symbol indicates a 5′-phosphate and to the right it indicates a 3′-phosphate), were measured as a function of pH, ionic strength and Mg2+ concentration. 2. The ORD titrations of ApAp(3′) and CpCp(3′), which were made by measuring the ORD curves at closely spaced pH intervals, exhibit a maximum at approx. pH5·0 and 5·7 for ApAp(3′) and CpCp(3′) respectively in the profile of the magnitude of the first Cotton effect versus pH. The results indicate that the conformational rigidity of these dinucleotides depends on the ionization state of a 3′-terminal phosphate group. 3. ApAp(3′) was shown to exist as an approximately 1:1 equilibrium mixture of the two major ionic species represented by Ap(−1)Ap(−1) and Ap(−1)Ap(−2) at pH6·16, whereas at pH7·5 it exists exclusively as a form of Ap(−1)Ap(−2). 4. To ascertain the effects of the presence of a terminal phosphate group and of the ionization of the secondary phosphate on the conformation of adenylate dimer, we measured the ORD of ApA, ApAp(3′)CH3 and ApAp(2′). The rotatory power of the first Cotton effect in the above series of dinucleotides decreased at 20° in the order ApA> ApAp(3′)CH3≈ApAp(3′)(−1)> ApAp(2′) at pH7> ApAp(3′) at pH7. 5. The pH–rotation profiles were also obtained for ApAp(2′), CpCp(2′) and UpUp(3′), but no corresponding maximum was observed. Although simple nearest-neighbour calculations based on the ORD data of IpIp(3′) and 5′-IMP account for the observed ORD spectrum of polyinosinic acid at low salt concentration, there were large discrepancies between calculated and experimental results of the polyguanylic acid ORD even at low ionic strength. 6. The extent to which the amplitude of the Cotton effects of IpIp(3′) increases with salt concentration, especially by the addition of Mg2+, was much greater than that observed for ApAp(3′). The implication of such salt effects on the ORD is considered.

Optical rotatory dispersion and circular dichroism of diastereoisomers. I. The ephedrines and chloramphenicols

1969 ◽  
Vol 47 (11) ◽  
pp. 1957-1963 ◽  
Author(s):  
L. A. Mitscher ◽  
F. Kautz ◽  
J. LaPidus
Keyword(s):  
Circular Dichroism ◽  
Absorption Band ◽  
Absolute Configuration ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Apparent Correlation ◽  
Circular Dichroïsm ◽  
Erroneous Assignment

Optical rotatory dispersion (o.r.d.) and circular dichroism measurements are reported for all four diastereoisomers in both the ephedrine and chloramphenicol series. The Cotton effect associated with the 1Lb absorption band is a reliable guide to absolute configuration in both series whereas the 1La band is not. Circular dichroism measurements are preferred as the 1La band dominates the o.r.d. curves to such an extent that erroneous assignment is quite possible. An attempt to relate the sign and intensity of the 1Lb Cotton effect with rotamer population failed due to lack of apparent correlation.

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.

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