Induced circular dichroism and chiral discrimination of racemates revisited: bilirubins as illustrative examples

Krois, Daniel; Lehner, Harald

doi:10.1039/p29950000489

Cited by 15 publications

(12 citation statements)

References 30 publications

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“…However, when BPA was added to a fixed concentration of OG (25 M) there is a progressive induction of (Ϫ) and (ϩ) CD at wavelengths 335 and 478 nm, respectively. This may be due to the induced asymmetry in the conformation of OG on binding to BPA (30,33). It may be noted that NMR results show that the conformation of OG changes significantly on binding with BPA.…”

Section: Resultsmentioning

confidence: 96%

Interaction of 7-Hydroxy-8-(phenylazo)1,3-naphthalenedisulfonate with Bovine Plasma Albumin

Patel

Srivastava

Phadke

1999

Journal of Biological Chemistry

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Sulfonated compounds have been used as biological staining reagents for some time. However, only recently it has been realized that some of these compounds can exhibit diverse biological activities (1-5) and hence are looked upon as potential pharmaceutical agents and important lead compounds (6 -8). The effectiveness of these compounds as pharmaceutical agents depends on their ability to reach and bind to the specific sites on the target proteins. Albumins are the principal proteins found in plasma contributing to the colloid osmotic pressure of the blood and also act as transport proteins for numerous endogenous and exogenous compounds (9). These have propensity to bind a wide variety of ligands. Because of this, albumins are assumed to function as transport protein and possibly serve as vehicles for regulating levels of drugs and metabolites in blood (10).The mode of interaction of various sulfonated azo compounds including 7-hydroxy-8-(phenylazo)1,3-naphthelenedisulfonate, commonly known as Orange G (OG) 1 (Fig. 1B) with amino acids such as Arg, Lys, and His has been reported (11). To the best of our knowledge, there is no report on the interaction of OG with any protein. Detailed knowledge of the OG-albumin interaction is relevant to the understanding of interaction of sulfonated azo dyes with enzymes and with specific binding proteins. We have therefore undertaken detailed investigations on the mode of interaction of OG and plasma protein called bovine plasma albumin (BPA).In this report, we have characterized BPA⅐OG complex using a variety of spectroscopic techniques such as nuclear magnetic resonance (NMR), circular dichroism (CD), fluorescence, etc. In addition, the conformation of BPA and of OG in BPA⅐OG complex is discussed. EXPERIMENTAL PROCEDURESMaterials-Bovine plasma albumin was purchased from Armour Pharmaceutical Co. and Orange G from Sigma. Concentration of BPA was determined using molecular mass of 66 kDa and A 279 ϭ 0.667 mg Ϫ1 ml cm Ϫ1 (12) and that of OG using ⑀ 478 ϭ 19900 M Ϫ1 cm Ϫ1. Other chemicals used were of AnalaR grade. 20 mM phosphate buffer, pH 7.2, was used. A mixture of acetate and phosphate (20 mM) was used to obtain pH in the range 4 -8.NMR-NMR measurements were carried out on a Varian Unity Plus 600-MHz spectrometer. Chemical shifts were measured with respect to sodium trimethylsilyl-propionate-2,2,3,3-d 4 . One-dimensional spectra were recorded with 16,000 data points, 6499-Hz spectral width, 64 transients, and a 2-s relaxation delay at 25°C. A 200-ms mixing time was used in the nuclear Overhauser effect spectroscopy (NOESY) (13) experiment. For 13 C-T 1 measurements, inversion recovery pulse sequence was incorporated in gradient enhanced heteronuclear single quantum coherence spectroscopy sequence (14). A relaxation time of 3 s was used. The 1 H spin lattice relaxation times (T 1 ) were measured using inversion recovery pulse sequence (15) using 12-s relaxation delay. The solvent resonance was suppressed by irradiation during relaxation delay and recovery time. T 1 was calc...

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Section: Resultsmentioning

confidence: 96%

Interaction of 7-Hydroxy-8-(phenylazo)1,3-naphthalenedisulfonate with Bovine Plasma Albumin

Patel

Srivastava

Phadke

1999

Journal of Biological Chemistry

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“…This approximation is generally feasible, although, if the enantiomeric excess is very modest, small chirooptical differences between the diasteromeric complexes come into play and may lead to no vanishing CD spectra also for racemic mixtures. The shape of such CD spectra may either be “normal,” as expected for the enantiomers, if the CD spectra of diastereomers differ only in magnitude, or more complex, if the spectra are shifted relative to each other34 (see below).…”

Section: Resultsmentioning

confidence: 99%

Deracemization of bilirubin as the marker of the chirality of micellar aggregates

et al. 2011

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The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities.

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“…We have chosen CD spectroscopy which is an established method in this area. 1, 20 The induced CD (ICD) observed in the BR absorption region of SA-BR complexes is due to an overpopulation of chiral, kinetically labile BR conformers. Equipopulation of enantiomeric BR species becomes invalidated by the discriminating influence of the surrounding protein.…”

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confidence: 99%

A circular dichroism (CD) study of the consecutive binding of serum albumin to bilirubin. Possible implications for the bilirubin level

Blaha¹,

Siam²,

Lehner³

1997

J. Chem. Soc., Perkin Trans. 2

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Binding studies on bovine serum albumin (BSA) with bilirubin (BR) have been performed under physiological conditions using circular dichroism (CD) and electronic absorption spectroscopy (UV-VIS). Analysis of data obtained from solutions at varying BSA/BR ratios (R), overall concentrations and pH suggests the coexistence of two similarly strong complexes with 1 : 1 stoichiometry (K ass,M ca. 1 × 10 7 dm 3 mol Ϫ1 ). Further binding to BSA affords associates for which a 2 : 1 stoichiometry (K ass,B ca. 5 × 10 4 dm 3 mol Ϫ1 , pH = 7.4) is proposed. Results indicate that these aggregates comprise the main transport form of BR under physiological conditions. The role of the differently compounded BSA-BR complexes for controlling the concentration of unbound BR in the plasma is discussed. Preliminary experiments performed on human serum albumin (HSA) are in line with an analogous complexing behaviour. ‡ For an interpretation of CD spectra in terms of conformation of the BR backbone see comments on p. 2122.

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Induced circular dichroism and chiral discrimination of racemates revisited: bilirubins as illustrative examples

Cited by 15 publications

References 30 publications

Interaction of 7-Hydroxy-8-(phenylazo)1,3-naphthalenedisulfonate with Bovine Plasma Albumin

Interaction of 7-Hydroxy-8-(phenylazo)1,3-naphthalenedisulfonate with Bovine Plasma Albumin

Deracemization of bilirubin as the marker of the chirality of micellar aggregates

A circular dichroism (CD) study of the consecutive binding of serum albumin to bilirubin. Possible implications for the bilirubin level

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