THE EFFECT OF pH ON THE FLUORESCENCE OF COMPLEXES OF HUMAN SERUM ALBUMIN AND BOVINE SERUM ALBUMIN WITH BILIRUBIN

Lee, J. J.; Gillispie, Gregory D.

doi:10.1111/j.1751-1097.1981.tb05486.x

Cited by 17 publications

(1 citation statement)

References 23 publications

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“…The binding affinity of several drugs is highly sensitive to the B-N equilibrium [2][3][4][5][6][7][8][9][10][11][12]. Wilting et al [2,3] first reported that the bindings of warfarin and diazepam to HSA were affected by the B-N transition.…”

Section: Introductionmentioning

confidence: 99%

1H NMR study of low-affinity binding of ibuprofen to human serum albumin at different pH

Liu

2000

Appl. Magn. Reson.

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H nuclear magnetic resonance (NMR) chemical shift, relaxation and diffusion coefficient measurements were carried out to study the influence of pH (from 8.0 to 6.1) on the low-affinity binding of ibuprofen (IBP), a nonsteroidal anti-inflammatory drug, to human serum albumin (HSA). The study demonstrated that the binding affinity of IBP to HSA increases when the solution is lowered below the physiological values. The increased binding capacity of IBP to HSA at lower pH is attributed to an increase in the number of (likely hydrophobic) low-affinity binding sites, made available upon HSA base-to-neutral conformation transition. With a fast reversible and site-independent binding model, the number of binding sites of the IBP-HSA complex, calculated from the relaxation data, was 15±2 at pH 8.0 to 22±1 at pH 6.8.

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Section: Introductionmentioning

confidence: 99%

1H NMR study of low-affinity binding of ibuprofen to human serum albumin at different pH

Liu

2000

Appl. Magn. Reson.

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Konformationsanalyse, Photophysik und Photochemie der Gallenpigmente; Bilirubin‐ und Biliverdindimethylester und verwandte lineare Tetrapyrrole

1983

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Professor Giinther 0. Schenck zum 70. Geburtstag gewidmetDas Verhalten der Dimethylester von Bilirubin und Biliverdin (BRE bzw. BVE) und verwandter h e a r e r Tetrapyrrole im elektronischen Grund-und Anregungszustand ist mit photochemischen und spektroskopischen Methoden -Absorption, Fluoreszenz, Fluoreszenzanregung, mediuminduziertem Circulardichroismus und magnetischer Protonenresonanzuntersucht worden. Beide Tetrapyrroltypen bilden in sehr verdiinnten Losungen Gemische von topologischen Isomeren. Bei den Bilirubinen wird die Heterogenitat der Losungen hauptsachlich auf zwei Konformere rnit unterschiedlicher iiiumlicher Anordnung der A/Bund C/D-Pyrromethenonteile zueinander zuriickgefuhrt. Die spektralen Eigenschaften des einen Konformers entsprechen jenen des isolierten Pyrromethenon-Grundchromophors, wiihrend diejenigen des anderen eine elektronische Kopplung der beiden vermutlich in ,,Fahiegel"-Anordnung gehaltenen Teilchromophore widerspiegelt. Drehungen um die Einfachbindungen C-5-C-6 und C-14-C-15 beteiligen sich parallel zu den photochemischen Kanillen (E+Z-Isomerisierung und Lumirubinbildung) an der strahlungslosen Desaktivierung des angeregten Singulettzustandes. Die weniger bewegliche ,,Falzziegel"-Komponente wird zusatzlich durch Prozesse desaktiviert, die durch Wasserstoffbriicken ausge18st werden. Bei den um zwei H-Atome tirmeren Biliverdinen sind die Verhaltnisse bedeutend komplexer. Um detailliertere Einsicht in die Mechanismen der strahlungslosen Desaktivierung der Anregungszusthde zu gewinnen, wurden die stationiiren Methoden durch zeitaufgeloste Methoden wie optoakustische Spektroskopie und ultraschnelle Absorptions-(Pump-Probe) und Fluoreszenz-Detektionstechniken (Single-Photon-Timing) erganzt. Die Usung enthtilt eine (Gruppe von) helical gekriimmte(n) all-2,all-syn-Spezies sowie Konformere mit gestreckter Anordnung der Ringe B und C um C-10 (E-anti, E-syn und Z-anti). Zwei angeregte Singulettzustande mit Picosekunden-Lebenszeiten sind einer oder zwei gekriimmten Grundzustandsformen zuzuordnen, und zwei bemerkenswert langlebige Nanosekunden-Zustinde entsprechen jeweils einer der gestreckten Grundzustandsformen. Zu den Ursachen der strahlungslosen Desaktivierung der Picosekunden-Zustande zahlen Drehungen um CC-Einfachbindungen und beim kiirzerlebigen Zustand zusatzlich auch die intramolekulare Protonverschiebung zwischen den B/C-Stickstoffatomen. Auch die 2d E-Photoisomerisierung ist ein wichtiger Desaktivierungskanal. Sie liefert selektiv ein gestrecktes Isomer (10E-anti), das bei Raumtemperatur thermisch das gekriimmte Ausgangsmaterial zuriickbildet. Bei Erhitzen oder Ultraschallbehandlung kann sich ein thermisch auch bei Raumtemperatur stabiles gestrecktes Isomer (1 OE-syn) bilden. Diese Form wandelt sich praktisch vollstiindig in Aggregate (vermutlich Dimere) um, und zwar bei Konzentrationen, bei denen die gekriimmte Komponente noch anscheinend unverindert monomer vorliegt.

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Solution Conformations, Photophysics, and Photochemistry of Bile Pigments; Bilirubin and Biliverdin, Dimethyl Esters and Related Linear Tetrapyrroles

Braslavsky

Holzwarth

Schaffner

1983

Angew. Chem. Int. Ed. Engl.

106

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Dedicated to Professor Giinther 0. Schenck on the occasion of his 70th birthdayBilirubin and biliverdin dimethyl esters (BRE and BVE, respectively) and related linear tetrapyrroles have been studied using a combination of photochemical and spectroscopic techniques, the latter including absorption, fluorescence, fluorescence excitation, mediuminduced circular dichroism, and proton magnetic resonance. Both types of tetrapyrroles form mixtures of different topological isomers in very dilute solutions. In the case of the bilirubins the heterogeneity of the solutions is caused by two coexisting conformers with different orientations of the A/B and C/D pyrromethenone moieties with respect to each other. The spectral properties of one conformer resemble the isolated parent pyrromethenone, whereas those of the other result from electronic coupling of the two subchromophores presumably held in a "ridge tile"-like orientation. C-C rotations at the C-5 and C-15 bridges substantially compete in both components with the photochemical channels (E+Z isomerization and lumirubin formation) for the radiationless deactivation of the excited singlet state. The more rigid "ridge tile" component additionally undergoes hydrogen bond-mediated deactivation, and it photoisomerizes more efficiently. The situation is markedly more complex with the biliverdins. In order to obtain a more detailed insight into the mechanisms of the radiationless excited-state processes, time-resolved optoacoustic spectroscopy and ultrafast absorption (pump-probe) and fluorescence detection (singlephoton-timing) techniques were used to supplement the stationary methods. The solution mixtures are composed of a (family of) helically coiled all-2,all-syn species, and of species differing from the former by stretched arrangements of the rings B and C around the central C-10 bridge (E-anti, E-syn, and Z-anti). Two excited singlet states with picosecond lifetimes are attributed to either one or two coiled ground-state forms, and two remarkably long-lived nanosecond excited states arise each from a stretched ground state. The radiationless deactivation of the shorter-lived of the picosecond states is brought about by ultrafast intramolecular proton transfer between the B/C nitrogen atoms, in addition to the C-C rotational modes operative in both. Z-+E photoisomerization is also an appreciable deactivation channel of excited biliverdin dimethyl ester. It is confined to the central C-10 double bond and selectively affords a stretched isomer (10E-anti), which thermally reforms the coiled starting material at room temperature via a sequence of tautomerization and C-C rotation. Heating or ultrasonic treatment can reverse this sequence and drive it farther to populate another stretched isomer (10E-syn) which is thermally stable at room temperature. This stretched form aggregates (presumably to dimers) already at concentrations at which the coiled species still appears to be fully monomeric.

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THE EFFECT OF pH ON THE FLUORESCENCE OF COMPLEXES OF HUMAN SERUM ALBUMIN AND BOVINE SERUM ALBUMIN WITH BILIRUBIN

Cited by 17 publications

References 23 publications

1H NMR study of low-affinity binding of ibuprofen to human serum albumin at different pH

1H NMR study of low-affinity binding of ibuprofen to human serum albumin at different pH

Konformationsanalyse, Photophysik und Photochemie der Gallenpigmente; Bilirubin‐ und Biliverdindimethylester und verwandte lineare Tetrapyrrole

Solution Conformations, Photophysics, and Photochemistry of Bile Pigments; Bilirubin and Biliverdin, Dimethyl Esters and Related Linear Tetrapyrroles

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