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Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives. Molecules 2023; 28:molecules28062564. [PMID: 36985535 PMCID: PMC10054127 DOI: 10.3390/molecules28062564] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 03/06/2023] [Accepted: 03/08/2023] [Indexed: 03/14/2023] Open
Abstract
In this work we review research activities on a few of the most relevant structural aspects of bilirubin (BR) and biliverdin (BV). Special attention is paid to the exocyclic C=C bonds being in mostly Z rather than E configurations, and to the overall conformation being essentially different for BR and BV due to the presence or absence of the double C=C bond at C-10. In both cases, racemic mixtures of each compound of either M or P configuration are present in achiral solutions; however, imbalance between the two configurations may be easily achieved. In particular, results based on chiroptical spectroscopies, both electronic and vibrational circular dichroism (ECD and VCD) methods, are presented for chirally derivatized BR and BV molecules. Finally, we review deracemization experiments monitored with ECD data from our lab for BR in the presence of serum albumin and anesthetic compounds.
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2
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Ghidinelli S, Abbate S, Boiadjiev SE, Lightner DA, Longhi G. l-Stercobilin-HCl and d-Urobilin-HCl. Analysis of Their Chiroptical and Conformational Properties by VCD, ECD, and CPL Experiments and MD and DFT Calculations. J Phys Chem B 2018; 122:12351-12362. [DOI: 10.1021/acs.jpcb.8b07954] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Simone Ghidinelli
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Sergio Abbate
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Stefan E. Boiadjiev
- Department of Chemistry and Biochemistry, Medical University-Pleven, 1 St. Kl. Ohridski Str., 5800 Pleven, Bulgaria
| | - David A. Lightner
- Department of Chemistry, University of Nevada, Reno, 1664 North Virginia Street, Reno, 89557-0020 Nevada, United States
| | - Giovanna Longhi
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy
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Zsila F, Juhász T, Bősze S, Horváti K, Beke-Somfai T. Hemin and bile pigments are the secondary structure regulators of intrinsically disordered antimicrobial peptides. Chirality 2017; 30:195-205. [PMID: 29110341 DOI: 10.1002/chir.22784] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 10/06/2017] [Accepted: 10/09/2017] [Indexed: 01/10/2023]
Abstract
The interaction of protoporphyrin compounds of human origin with the major bee venom component melittin (26 a.a., Z +6) and its hybrid derivative (CM15, 15 a.a., Z +6) were studied by a combination of various spectroscopic methods. Throughout a two-state, concentration-dependent process, hemin and its metabolites (biliverdin, bilirubin, bilirubin ditaurate) increase the parallel β-sheet content of the natively unfolded melittin, suggesting the oligomerization of the peptide chains. In contrast, α-helix promoting effect was observed with the also disordered but more cationic CM15. According to fluorescence quenching experiments, the sole Trp residue of melittin is the key player during the binding, in the vicinity of which the first pigment molecule is accommodated presumably making indole-porphyrin π-π stacking interaction. As circular dichroism titration data suggest, cooperative association of additional ligands subsequently occurs, resulting in multimeric complexes with an apparent dissociation constant ranged from 20 to 65 μM. Spectroscopic measurements conducted with the bilirubin catabolite urobilin and stercobilin refer to the requirement of intact dipyrrinone moieties for inducing secondary structure transformations. The binding topography of porphyrin rings on a model parallel β-sheet motif was evaluated by absorption spectroscopy and computational modeling showing a slipped-cofacial binding mode responsible for the red shift and hypochromism of the Soret band. Our results may aid to recognize porphyrin-responsive binding motifs of biologically relevant, intrinsically disordered peptides and proteins, where transient conformations play a vital role in their functions.
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Affiliation(s)
- Ferenc Zsila
- Biomolecular Self-Assembly Group, Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Tünde Juhász
- Biomolecular Self-Assembly Group, Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Szilvia Bősze
- MTA-ELTE Research Group of Peptide Chemistry, Hungarian Academy of Sciences, Eötvös Loránd University, Budapest, Hungary
| | - Kata Horváti
- MTA-ELTE Research Group of Peptide Chemistry, Hungarian Academy of Sciences, Eötvös Loránd University, Budapest, Hungary
| | - Tamás Beke-Somfai
- Biomolecular Self-Assembly Group, Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
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Ghidinelli S, Longhi G, Mazzeo G, Abbate S, Boiadjiev SE, Lightner DA. On the aggregation of bilirubinoids in solution as evidenced by VCD and ECD spectroscopy and DFT calculations. Chirality 2017; 30:19-28. [PMID: 29083054 DOI: 10.1002/chir.22776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 09/20/2017] [Accepted: 10/01/2017] [Indexed: 11/11/2022]
Abstract
Vibrational and electronic circular dichroism (VCD and ECD) spectra of 3 optically active bilirubin analogs with propionic acid groups replaced by (1) 1-(S)-methylpropyl groups, (2) 3-acetoxy-1-(S)-methylpropyl groups, and (3) 1-(S)-2-(R)-dimethyl-2-(methoxycarbonyl)ethyl groups have been recorded at different concentrations in chloroform. The aliphatic chains attached to C-8 and C-12 of the 3 chosen mesobilirubins were modified so as to possess no OH group. The variation of the VCD spectra with concentration is consistent with the formation of dimers at high concentration. Density functional theory and time-dependent density functional theory calculations on monomeric and dimeric forms support such a conclusion. Comparing with previous VCD (ECD) and IR (UV) studies of other mesobilirubin molecules, it is concluded that here, the key feature for aggregation is the missing OH groups on the propionic acid chains. The latter, in synergy with the polar groups of lactam moieties, appear to be involved in intramolecular phenomena and thus favor monomeric forms. Investigation of ECD and UV spectra of the same compounds in mixed DMSO/chloroform solutions provide further clues to the proposed picture.
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Affiliation(s)
- Simone Ghidinelli
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Brescia, Italy
| | - Giovanna Longhi
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Brescia, Italy
| | - Giuseppe Mazzeo
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Brescia, Italy
| | - Sergio Abbate
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Brescia, Italy
| | - Stefan E Boiadjiev
- Department of Chemistry and Biochemistry, Medical University-Pleven, Pleven, Bulgaria
| | - David A Lightner
- Department of Chemistry, University of Nevada, Reno, Nevada, USA
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5
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Novotná P, Králík F, Urbanová M. Chiral recognition of bilirubin and biliverdin in liposomes and micelles. Biophys Chem 2015; 205:41-50. [PMID: 26071845 DOI: 10.1016/j.bpc.2015.06.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 05/30/2015] [Accepted: 06/01/2015] [Indexed: 11/25/2022]
Abstract
The structural formula of biologically important chiral pigments bilirubin and biliverdin differs only by one double bond. We showed that this results in dissimilar interactions with two models of membranes: cationic liposomes composed of 3β-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol and zwitterionic micelles from 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). While the liposomes recognized the P-form of bilirubin, the micelles recognized its M-form. Both recognized the P-form of biliverdin. Our study also comprised ternary systems consisting of the pigments, model membranes and serum albumin (human and bovine). Bilirubin preferentially interacted with the albumins even in the presence of the liposomes. On the other hand, biliverdin preferred the liposomes. Remarkably, the presence of CHAPS completely changed the biliverdin binding to the protein. Because our study was oriented on different chiral interactions, a chiroptical method of electronic circular dichroism was chosen as the principal method to study our systems. As complementary methods, UV-vis absorption and fluorescence emission were used.
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Affiliation(s)
- Pavlína Novotná
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic
| | - František Králík
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic
| | - Marie Urbanová
- Department of Physics and Measurements, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
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Novotná P, Urbanová M. Bilirubin, model membranes and serum albumin interaction: The influence of fatty acids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1331-40. [DOI: 10.1016/j.bbamem.2015.02.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 01/31/2015] [Accepted: 02/25/2015] [Indexed: 01/08/2023]
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Novotná P, Goncharova I, Urbanová M. Mutual structural effect of bilirubin and model membranes by vibrational circular dichroism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:831-41. [DOI: 10.1016/j.bbamem.2013.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 12/07/2013] [Accepted: 12/09/2013] [Indexed: 12/20/2022]
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Mölzer C, Huber H, Steyrer A, Ziesel GV, Wallner M, Goncharova I, Orlov S, Urbanová M, Ahlfors CE, Vítek L, Bulmer AC, Wagner KH. Interaction between TNFone and tetrapyrroles may account for their anti-genotoxic effects — a novel mechanism for DNA-protection. J PORPHYR PHTHALOCYA 2013. [DOI: 10.1142/s1088424613500995] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Bilirubin, the principal and biologically most relevant bile pigment was, until recently, considered a waste product of haem catabolism. However, current data suggest that bile pigments possess biological potential, related to their antioxidant and anti-mutagenic effects. In this context, it is now assumed that bile pigments and their derivatives exert these effects via multiple mechanisms, including discrete anti-oxidative and physico-chemical interactive effects. The major scientific focus so far has concentrated on the compounds' antioxidant action, and mechanistic investigations of possible mutagen-tetrapyrrole interaction are lacking. Therefore we tested structurally related bile pigments/derivatives (bilirubin/-ditaurate/-dimethyl ester, biliverdin/-dimethyl ester, urobilin, stercobilin and protoporphyrin) for anti-genotoxicity in the Salmonella reverse mutation assay (strains TA98, TA102), together with the synthetic mutagen 2,4,7-trinitro-9H-fluoren-9-one (TNFone). To explore possible structural interactions, molecular systems of chlorin e6 porphyrin/bilirubin/biliverdin with TNFone were assayed using circular dichroism. These data consistently revealed, at suprastoichiometric concentrations, that tetrapyrroles interact with TNFone. Addition of TNFone to chlorin e6 porphyrin, bilirubin-albumin and biliverdin-albumin led to a marked change in pigment spectra, providing evidence for tight tetrapyrrole-mutagen interaction. This conclusion was also supported by substantial, TNFone-induced decrease of bilirubin oxidation in the bilirubin-albumin system. This outcome was reflected in a bacterial model, in which most tetrapyrroles and especially protoporphyrin, significantly attenuated TNFone-induced mutagenesis. These data indicate that aromatic, tetrapyrrolic molecules interact with TNFone, providing a novel mechanism to suggest the anti-mutagenic effects of bile pigments in vivo are related to their physico-chemical interaction with genotoxins.
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Affiliation(s)
- Christine Mölzer
- University of Vienna, Faculty of Life Sciences, Department of Nutritional Sciences, Althanstraße 14, 1090 Vienna, Austria
| | - Hedwig Huber
- University of Vienna, Faculty of Life Sciences, Department of Nutritional Sciences, Althanstraße 14, 1090 Vienna, Austria
| | - Andrea Steyrer
- University of Vienna, Faculty of Life Sciences, Department of Nutritional Sciences, Althanstraße 14, 1090 Vienna, Austria
| | - Gesa V. Ziesel
- University of Vienna, Faculty of Life Sciences, Department of Nutritional Sciences, Althanstraße 14, 1090 Vienna, Austria
| | - Marlies Wallner
- University of Vienna, Faculty of Life Sciences, Department of Nutritional Sciences, Althanstraße 14, 1090 Vienna, Austria
| | - Iryna Goncharova
- Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic
| | - Sergey Orlov
- Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic
| | - Marie Urbanová
- Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic
| | - Charles E. Ahlfors
- Stanford University, School of Medicine, 750 Welch Road, Suite 212, Palo Alto, CA 94304, USA
| | - Libor Vítek
- Institute of Medical Biochemistry and Laboratory Diagnostics and 4th Department of Internal Medicine, 1st Faculty of Medicine, Charles University in Prague, Kateřinská 32, 121 08 Prague 2, Czech Republic
| | - Andrew C. Bulmer
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University (Gold Coast Campus), Australia, 4222, Australia
| | - Karl-Heinz Wagner
- University of Vienna, Faculty of Life Sciences, Department of Nutritional Sciences, Althanstraße 14, 1090 Vienna, Austria
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University (Gold Coast Campus), Australia, 4222, Australia
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Novotná J, Goncharova I, Urbanová M. Guanosine assemblies: newly used matrices for chiroptical studies on biliverdin. Supramol Chem 2013. [DOI: 10.1080/10610278.2013.814774] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Jana Novotná
- Department of Analytical Chemistry, Institute of Chemical Technology, Prague, Prague 6, Czech Republic
| | - Iryna Goncharova
- Department of Analytical Chemistry, Institute of Chemical Technology, Prague, Prague 6, Czech Republic
| | - Marie Urbanová
- Department of Physics and Measurements, Institute of Chemical Technology, Prague, Prague 6, Czech Republic
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The location of the high- and low-affinity bilirubin-binding sites on serum albumin: ligand-competition analysis investigated by circular dichroism. Biophys Chem 2013; 180-181:55-65. [PMID: 23838624 DOI: 10.1016/j.bpc.2013.06.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 05/28/2013] [Accepted: 06/04/2013] [Indexed: 12/20/2022]
Abstract
The locations of three bilirubin (BR)-binding sites with different affinities were identified as subdomains IB, IIA and IIIA for five mammalian serum albumins (SAs): human (HSA), bovine (BSA), rat, (RSA), rabbit (RbSA) and sheep (SSA). The stereoselectivity of a high-affinity BR-binding site was identified in the BR/SA=1/1 system by circular dichroism (CD) spectroscopy, the sites with low affinity to BR were analyzed using difference CD. Site-specific ligand-competition experiments with ibuprofen (marker for subdomain IIIA) and hemin (marker for subdomain IB) did not reveal any changes for the BR/SA=1/1 system and showed a decrease of the bound BR at BR/SA=3/1. Both sites were identified as sites with low affinity to BR. The correlation between stereoselectivity and the arrangement of Arg-Lys residues indicated similarity between the BR-binding sites in subdomain IIIA for all of the SAs studied. Subdomain IB in HSA, BSA, SSA and RbSA has P-stereoselectivity while in RSA it has M-selectivity toward BR. A ligand-competition experiment with gossypol shows a decrease of the CD signal of bound BR for the BR/SA=1/1 system as well as for BR/SA=3/1. Subdomain IIA was assigned as a high-affinity BR-binding site. The P-stereoselectivity of this site in HSA (and RSA, RbSA) was caused by the right-hand localization of charged residues R257/R218-R222, whereas the left-hand orientation of R257/R218-R199 led to the M-stereoselectivity of the primary binding site in BSA (and SSA).
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11
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Goncharova I, Orlov S, Urbanová M. Chiroptical properties of bilirubin-serum albumin binding sites. Chirality 2013; 25:257-63. [PMID: 23460297 DOI: 10.1002/chir.22143] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 11/14/2012] [Indexed: 11/06/2022]
Abstract
Although the interactions between bilirubin and serum albumin are among the most studied serum albumin-ligand interactions, the binding-site location and the participation of bilirubin-serum albumin complexes in pathological and physiological processes are under debate. In this article, we have benefited from the chiral structure of bilirubin and used CD spectroscopy to characterize the structure of bilirubin bound to human and bovine serum albumins. We determined that in a phosphate buffer at pH 7.8 there are three binding sites in both human and bovine serum albumins. While the primary binding sites in human and bovine serum albumins bind bilirubin with P- and M-helical conformations, respectively, the secondary binding sites in both albumins bind bilirubin in the P-helical conformation. We have shown that the bonding of bilirubin to the serum albumin matrix is a more favorable process than the self-association of bilirubin under the studied conditions, with a maximum of three bound bilirubins per serum albumin molecule. Although bilirubin bound to the primary binding site has attracted the most attention, the presented results have documented the impact of the secondary binding sites which are relevant in the displacement reactions between BR and drugs and in the phenomena where bilirubin plays antioxidant, antimutagenic, and anti-inflammatory roles.
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Affiliation(s)
- Iryna Goncharova
- Department of Analytical Chemistry, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic
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12
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Abbate S, Lebon F, Longhi G, Boiadjiev SE, Lightner DA. Vibrational and Electronic Circular Dichroism of Dimethyl Mesobilirubins-XIIIα. J Phys Chem B 2012; 116:5628-36. [DOI: 10.1021/jp3013255] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sergio Abbate
- Dipartimento
di Scienze Biomediche
e Biotecnologie, Università di Brescia, 25123 Brescia, Italy
| | - France Lebon
- Dipartimento
di Scienze Biomediche
e Biotecnologie, Università di Brescia, 25123 Brescia, Italy
| | - Giovanna Longhi
- Dipartimento
di Scienze Biomediche
e Biotecnologie, Università di Brescia, 25123 Brescia, Italy
| | - Stefan E. Boiadjiev
- Department of Chemistry and
Biochemistry, Medical University-Pleven, 1 St. Kliment Ohridski Street, 5800 Pleven, Bulgaria
| | - David A. Lightner
- Department of Chemistry, University of Nevada, Reno, Nevada 89557-0020, United
States
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Urbanová M. Bioinspired interactions studied by vibrational circular dichroism. Chirality 2010; 21 Suppl 1:E215-30. [PMID: 19937957 DOI: 10.1002/chir.20803] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vibrational circular dichroism (VCD) spectra are reliable indicators of the spatial structure of chiral molecules. The specific and characteristic feature of vibrational spectroscopy, and therefore also of VCD, where the energy of some vibrational modes is predominantly focused to a specific part of the molecule, enables monitoring both the structure of the molecule dissolved in different solvents and under different physicochemical conditions and molecular interactions. This minireview deals with recent contributions covering structural information on the bioinspired interactions obtained by means of VCD, especially in the following areas: interaction of DNA with biomolecules and biogenic metals, guanine tetramers and quadruplexes, biointeractions of bile pigments, and polypeptide and protein interactions with other biomolecules.
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Affiliation(s)
- Marie Urbanová
- Department of Physics and Measurements, Institute of Chemical Technology, Prague, Czech Republic.
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14
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Vibrational and electronic circular dichroism study of bile pigments: Complexes of bilirubin and biliverdin with metals. Anal Biochem 2009; 392:28-36. [DOI: 10.1016/j.ab.2009.05.040] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 05/21/2009] [Accepted: 05/23/2009] [Indexed: 11/18/2022]
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Goncharova I, Urbanová M. Stereoselective bile pigment binding to polypeptides and albumins: a circular dichroism study. Anal Bioanal Chem 2008; 392:1355-65. [PMID: 18946665 DOI: 10.1007/s00216-008-2427-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 09/10/2008] [Accepted: 09/19/2008] [Indexed: 10/21/2022]
Abstract
Stereoselective recognition of bilirubin and biliverdin by poly(L-lysine) (PLL), poly(D-lysine) (PDL), and poly(L-arginine) (PLA) and their micelles with dodecanoate ions (C(12)) at different pH has been studied using a combination of vibrational and electronic circular dichroism. Biliverdin has been found to be more sensitive to pH in its complexes with the polypeptides. In acidic media in the complexes with PLL-C(12) and PDL-C(12) the conformation becomes more closed than the characteristic one found at physiological pH. Partial flattening and chiral self-association of bilirubin molecules takes place at higher concentrations with PLL and PDL. For both pigments, inversions of the ECD signals are observed in the systems with PLA at pH > or = 8.5. This study was carried out in order to clarify the role of Lys and Arg residues in pigment binding to serum albumin. The circular dichroism spectra obtained for bilirubin bound to different mammalian serum albumins have been compared with the homology within the IIA principal ligand-binding structural domains. Analysis suggests that the chiroptical properties of the pigment in the complexes with serum albumins depend on the location of Lys and/or Arg at positions 222 and 199 in the binding site.
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Affiliation(s)
- Iryna Goncharova
- Department of Analytical Chemistry, Institute of Chemical Technology, Prague, Technická 5, 166 28, Prague 6, Czech Republic
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