Diterpenoids. XXI. 8-Oxo-14-norlabdanes

1969 ◽  
Vol 22 (8) ◽  
pp. 1681 ◽  
Author(s):  
RM Carman ◽  
DE Cowley ◽  
RA Marty
Keyword(s):  
Optical Rotation ◽  
Cotton Effect ◽  
Original Publication ◽  
Negative Cotton Effect

Structure and optical rotation are correlated for some 8-oxo-14- norlabdanes which all have a negative rotation at the sodium D line and a negative Cotton effect. A correlation of communic acid with agathic acid is shown to be correct in spite of some erroneous rotations in the original publication.

Outer-sphere interaction of (S)-asparagine and (S)-glutamine with [Co(NH3)6]3+ ion and its possible role in ligand substitution

1987 ◽  
Vol 52 (10) ◽  
pp. 2457-2459
Author(s):  
František Jursík
Keyword(s):  
Amino Acids ◽  
Transition Region ◽  
Alkaline Medium ◽  
Optical Activity ◽  
Substitution Reaction ◽  
Outer Sphere ◽  
Ligand Substitution ◽  
Cotton Effect ◽  
Negative Cotton Effect

Optical activity of the achiral cation [Co(NH3)6]3+ is induced both by (S)-AsnONa and (S)-GlnONa, as shown by a negative Cotton effect in the 1A1g → 1T1g transition region. An outer-sphere interaction by three-point attachment of the amides can explain the fact that substitution reaction of [Co(NH3)6]3+ with the mentioned amides in an alkaline medium is unusually slow as compared with other amino acids.

scholarly journals DETERMINATION OF THE POLARIZATION OPTICAL PROPERTIES OF THE AMYLOID-CONGO RED COMPLEX BY PHASE MODULATION MICROSPECTROPHOTOMETRY

1974 ◽  
Vol 22 (12) ◽  
pp. 1105-1112 ◽  
Author(s):  
DOUGLASS L. TAYLOR ◽  
ROBERT D. ALLEN ◽  
EARL P. BENDITT
Keyword(s):  
Circular Dichroism ◽  
Congo Red ◽  
Phase Modulation ◽  
Optical Rotation ◽  
Polarized Light ◽  
Visible Spectrum ◽  
Linear Dichroism ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Circular Dichroïsm

The polarization properties responsible for the classical "green birefringence" of the amyloid-Congo red complex have been determined by a new optical method, phase modulation microspectrophotometry. This method now makes possible the measurement of one optical property at a time (birefringence, optical rotation, linear dichroism and circular dichroism throughout the visible spectrum) in complex specimens in which visible contrast in polarized light is the result of a mixture of polarization effects. The green birefringence is explained by a combination of optical effects, the strongest of which are dispersion of birefringence and linear dichroism superimposed on the smaller effects of circular dichroism and optical rotatory dispersion. The interaction of the planar dye molecules with the amyloid protein induces an extrinsic Cotton effect.

Interaction of thiamin diphosphate with phosphorylated and dephosphorylated mammalian pyruvate dehydrogenase complex

2005 ◽  
Vol 386 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Xiaoqing Liu ◽  
Hans Bisswanger
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Tryptophan Fluorescence ◽  
Cotton Effect ◽  
Binding Studies ◽  
Thiamin Diphosphate ◽  
Allosteric Inhibitors ◽  
Intrinsic Tryptophan Fluorescence ◽  
Negative Cotton Effect ◽  
Dehydrogenase Complex

Abstract Kinetic and binding studies were carried out on substrate and cofactor interaction with the pyruvate dehydrogenase complex from bovine heart. Fluoropyruvate and pyruvamide, previously described as irreversible and allosteric inhibitors, respectively, are strong competitive inhibitors with respect to pyruvate. Binding of thiamin diphosphate was used to study differences between the active dephosphorylated and inactive phosphorylated enzyme states by spectroscopic methods. The change in both the intrinsic tryptophan fluorescence and the fluorescence of the 6-bromoacetyl-2-dimethylaminonaphthalene-labelled enzyme complex produced on addition of the cofactor showed similar binding behaviour for both enzyme forms, with slightly higher affinity for the phosphorylated form. Changes in the CD spectrum, especially the negative Cotton effect at 330 nm as a function of cofactor concentration, both in the absence and presence of pyruvate, also revealed no drastic differences between the two enzyme forms. Thus, inactivation of the enzyme activity of the pyruvate dehydrogenase complex is not caused by impeding the binding of substrate or cofactor.

Cobalt(III) Complexes of a Stereospecific Ligand Derived from (S)-Proline

1979 ◽  
Vol 32 (8) ◽  
pp. 1661 ◽  
Author(s):  
T Woon ◽  
MJ O'Conner
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Absolute Configuration ◽  
Cotton Effect ◽  
Low Energy ◽  
Spectral Measurements ◽  
Asymmetric Carbon Atom ◽  
Geometrical Isomers ◽  
Negative Cotton Effect ◽  
Asymmetric Carbon

The quadridentate ligand, (2S,2'S)-1,1'-(ethane-1,2-diyl)bis(pyrrolidine-2-carboxylic acid) dihydrochloride (H2pren,2HCl), has been derived from (S)-proline. The preparations of the cobalt(III) complexes Na [Co(pren)(CO3)],3H2O, [CO(pren)(H2O)2] ClO4,- 2H2O and [Co(pren)(H2O)Cl],1�5H2O are described. All exist as cis-α geometrical isomers. 13C N.M.R. and absorption spectral measurements confirm the cis-α arrangement. The complex cis-α- [Co(pren)(H2O)Cl],1�5H2O rapidly aquates with retention of configuration. The compounds having actual or near C2 symmetry exhibit a strong negative c.d. band under the 1A1g → 1T1g cubic absorption band which is due to the 1A1 →1E tetragonal component, consistent with the Δ absolute configuration imposed by the (S) configuration of the asymmetric carbon atom in the (S)-proline moiety. The o.r.d. spectrum of cis-α-Na [Co(pren)CO3],3H2O in aqueous solution has a negative Cotton effect at low energy as expected for the Δ absolute configuration.

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.

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.

The circular dichroism of a,b-unsaturated ketones. I. Circular dichroism in the singlet-singlet and singlet-triplet n «p* transitions of steroidal 4-en-3-ones

1980 ◽  
Vol 33 (10) ◽  
pp. 2189 ◽  
Author(s):  
AF Beecham ◽  
DJ Collins
Keyword(s):  
Circular Dichroism ◽  
Structure Analysis ◽  
Wavelength Range ◽  
Cotton Effect ◽  
Electronic Transitions ◽  
Positive Contribution ◽  
X Ray ◽  
Unsaturated Ketones ◽  
Negative Cotton Effect ◽  
Circular Dichroïsm

The circular dichroism from 22 steroidal 4-en-3-ones in cyclohexane solution has been recorded through the wavelength range 400-265 nm. It is shown that both the singlet-triplet and the singlet-singlet n → π* electronic transitions contribute. Through examination of evidence from c.d. and X-ray structure analysis, it is concluded that the conformation of the chromophore and its immediate environment remains constant under the conditions of measurement. In three of the 6β- substituted compounds the normal, highly structured, negative Cotton effect from the singlet-singlet n → π* transition is modified by positive c.d. with the same vibrational structuring. The origin of the positive contribution is discussed.

scholarly journals Kinetic Investigation on Tetrakis(4-Sulfonatophenyl)Porphyrin J-Aggregates Formation Catalyzed by Cationic Metallo-Porphyrins

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5742
Author(s):  
Ilaria Giuseppina Occhiuto ◽  
Roberto Zagami ◽  
Mariachiara Trapani ◽  
Maria Angela Castriciano ◽  
Andrea Romeo ◽  
...  
Keyword(s):  
Rate Constants ◽  
Cotton Effect ◽  
Resonance Light Scattering ◽  
Aggregation Kinetics ◽  
Extinction Time ◽  
Negative Cotton Effect ◽  
Metal Derivatives ◽  
J Aggregates ◽  
Derivatives Of

Under mild acidic conditions, various metal derivatives of tetrakis(4-N-methylpyridinium)porphyrin (gold(III), AuT4; cobalt(III), CoT4; manganese(III), MnT4 and zinc(II), ZnT4) catalytically promote the supramolecular assembling process of the diacid 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4) into J-aggregates. The aggregation kinetics have been treated according to a well-established model that involves the initial formation of a critical nucleus containing m porphyrin units, followed by autocatalytic growth, in which the rate evolves as a power of time. An analysis of the extinction time traces allows to obtain the rate constants for the auto-catalyzed pathway, kc, and the number of porphyrins involved in the initial seeding. The aggregation kinetics have been investigated at fixed H2TPPS4 concentration as a function of the added metal derivatives MT4. The derived rate constants, kc, obey a rate law that is first order in [MT4] and depend on the specific nature of the catalyst in the order AuT4 > CoT4 > MnT4 > ZnT4. Both resonance light scattering (RLS) intensity and extinction in the aggregated samples increase on increasing [MT4]. With the exception of AuT4, the final aggregated samples obtained at the highest catalyst concentration exhibit a negative Cotton effect in the J-band region, evidencing the occurrence of spontaneous symmetry breaking. The role of the nature of the metal derivative in terms of overall charge and presence of axial groups will be discussed.

scholarly journals CHANGE IN THE STRUCTURE OF SHOPE PAPILLOMA VIRUS-INDUCED ARGINASE ASSOCIATED WITH MUTATION OF THE VIRUS

1971 ◽  
Vol 134 (6) ◽  
pp. 1442-1452 ◽  
Author(s):  
Stanfield Rogers
Keyword(s):  
Genetic Information ◽  
Specific Activity ◽  
Specific Rotation ◽  
Cotton Effect ◽  
Polymerization Degree ◽  
Papilloma Virus ◽  
Negative Cotton Effect ◽  
Rotary Dispersion ◽  
Optical Rotary Dispersion ◽  
Shope Papilloma Virus

The change in the state of the virus-induced enzyme associated with a mutation in the virus provides additional evidence that the enzyme is synthesized from virus rather than rabbit genetic information. This change in structure results in differences in stability of polymerization, degree of optical rotary dispersion (ORD) specific rotation, change in elution characteristics from carboxymethyl cellulose, and a reduction in specific activity of the arginase. Liver arginase differs markedly in ORD characteristics from the virus-induced enzyme. In contrast to the virus-induced enzyme, it showed no negative Cotton effect at 233 nm until it was activated with manganese. Manganese had no influence on the ORD spectrum of virus-induced arginase. In addition, liver arginase is denatured by 4 M urea, while the virus-induced enzyme requires 10 M urea for denaturation.

Sign in / Sign up

Export Citation Format

Share Document