Kinetic study of the photochemical changes of (ZZ)-bilirubin IX α bound to human serum albumin. Demonstration of (EZ)-bilirubin IX α as an intermediate in photochemical changes from (ZZ)-bilirubin IX α to (EZ)-cyclobilirubin IX α

The present study was performed to elucidate why the photochemical reaction of (ZZ)-bilirubin bound to human serum albumin is singularly selective, and only one of the two (EZ)- and (ZE)-bilirubins, the (ZE)-isomer, is produced. In a kinetic study of the photochemical reaction in vitro, the sum of the relative rate constants of photochemical transformation of (EZ)-bilirubin into both (EZ)-cyclobilirubin and (ZZ)-bilirubin, with a significant preference for the former, was proved to be considerably larger than that of the transformation of (ZZ)-bilirubin into (EZ)-bilirubin. Therefore only one of the geometrical isomers, namely (ZE)-bilirubin, is apparently formed. It was concluded that (EZ)-bilirubin photochemically undergoes (EZ)-cyclization, i.e. structural photoisomerization, while bound to its high-affinity site on human serum albumin, and is an intermediate in the transformation of (ZZ)-bilirubin into (EZ)-cyclobilirubin.

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Comparison of kinetic study of the photochemical changes of (ZZ)-bilirubin IXα bound to human serum albumin with that bound to rat serum albumin

Biochemical Journal ◽

10.1042/bj2300561 ◽

1985 ◽

Vol 230 (3) ◽

pp. 561-567 ◽

Cited By ~ 9

Author(s):

S Onishi ◽

S Itoh ◽

T Yamakawa ◽

K Isobe ◽

M Manabe ◽

...

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Rate Constants ◽

Relative Rate ◽

Rat Serum ◽

Relative Rate Constants ◽

Rat Serum Albumin

It has been stated by McDonagh, Palma & Lightner [(1982) J. Am. Chem. Soc. 104, 6867-6871] that complexing of bilirubin with serum albumin has a marked species-dependent influence on bilirubin photoisomerization in vitro and in vivo. Therefore the kinetics for the quantitatively important reaction: (Formula: see text) of the photochemical interconversion between bilirubin and its photoisomers bound to human or rat serum albumin in aqueous solution, assayed by h.p.l.c., was used to elucidate the observed species-dependent difference. The relative rate constants for bilirubin bound to human serum albumin, except for k4, the rate of interconversion from (ZZ)-bilirubin into (EZ)-bilirubin, proved to be considerably larger than those for bilirubin bound to rat serum albumin. In accordance with these rate constants, the formation of photoisomers of bilirubin bound to human serum albumin, except for (EZ)-bilirubin, is very rapid and much greater than that for bilirubin bound to rat serum albumin.

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Wavelength-dependence of the relative rate constants for the main geometric and structural photoisomerization of bilirubin IX α bound to human serum albumin. Demonstration of green light at 510 nm as the most effective wavelength in photochemical changes from (ZZ)-bilirubin IX α to (EZ)-cyclobilirubin IX α via (EZ)-bilirubin

Biochemical Journal ◽

10.1042/bj2360023 ◽

1986 ◽

Vol 236 (1) ◽

pp. 23-29 ◽

Cited By ~ 36

Author(s):

S Onishi ◽

S Itoh ◽

K Isobe

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Light Source ◽

Rate Constants ◽

Relative Rate ◽

Green Light ◽

Wavelength Dependence ◽

Relative Rate Constants

The kinetics for the quantitatively important reaction: (Formula: see text) that is, the photochemical interconversion between bilirubin and its geometric and structural photoisomers bound to human serum albumin in aqueous solution when various wavelengths of monochromatic light were used, were assayed by h.p.l.c. In order to clarify the wavelength-dependence of the relative rate constants in the individual steps, a light-source with a half-bandwidth of 10 nm was used at increments of 20 nm, in the range from 410 nm to 550 nm. We describe for the first time studies on the wavelength-dependence of rate constants in geometric and structural photoisomerization reactions in vitro of (ZZ)-bilirubin or (EZ)-bilirubin bound to human serum albumin, especially the relative rate constants of cyclization of (EZ)-bilirubin into (EZ)-cyclobilirubin. Because studies in vitro have demonstrated that the wavelengths from 350 to 450 nm are mutagenic, the results obtained indicated that the safest and ideal light-source for phototherapy is green light of 510 nm, which keeps (ZE)-bilirubin concentrations as low as possible, as shown by a maximal value of k2 at 510 nm and a relatively low value of k1 at 510 nm. This light-source still ensures the substantial absorption of (ZZ)-bilirubin, which is the precursor of (EZ)-bilirubin, the intermediate in (EZ)-cyclobilirubin formation and, furthermore, as shown by the maximal value of k5 and a considerable value of k4 at 510 nm, promotes the cyclization of (EZ)-bilirubin derived from (ZZ)-bilirubin even though k3 at 510 nm also shows a peak value.

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Study on the interaction of ertugliflozin with human serum albumin in vitro by multispectroscopic methods, molecular docking, and molecular dynamics simulation

Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy ◽

10.1016/j.saa.2019.04.047 ◽

2019 ◽

Vol 219 ◽

pp. 83-90 ◽

Cited By ~ 14

Author(s):

Wenjing Wang ◽

Na Gan ◽

Qiaomei Sun ◽

Di Wu ◽

Ruixue Gan ◽

...

Keyword(s):

Molecular Dynamics ◽

Molecular Docking ◽

Molecular Dynamics Simulation ◽

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Dynamics Simulation

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Nof2206Probing the interaction of memantine, an important Alzheimer's drug, with human serum albumin: In silico and In vitro approach

Journal of Molecular Liquids ◽

10.1016/j.molliq.2021.116888 ◽

2021 ◽

pp. 116888

Author(s):

Fahad A. Alhumaydhi ◽

Mohammad Abdullah Aljasir ◽

Abdullah S.M. Aljohani ◽

Suliman A. Alsagaby ◽

Ameen S.S. Alwashmi ◽

...

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

In Silico

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Synthesis and In Vitro Assessment of pH-Sensitive Human Serum Albumin Conjugates of Pirarubicin

Pharmaceuticals ◽

10.3390/ph14010022 ◽

2020 ◽

Vol 14 (1) ◽

pp. 22

Author(s):

Kenji Tsukigawa ◽

Shuhei Imoto ◽

Keishi Yamasaki ◽

Koji Nishi ◽

Toshihiko Tsutsumi ◽

...

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Coupling Reaction ◽

Synthetic Polymer ◽

Ph Sensitive ◽

Acidic Ph ◽

Polymer Conjugate ◽

Acidic Conditions

In a previous study, we reported on the development of a synthetic polymer conjugate of pirarubicin (THP) that was formed via an acid-labile hydrazone bond between the polymer and the THP. However, the synthetic polymer itself was non-biodegradable, which could lead to unexpected adverse effects. Human serum albumin (HSA), which has a high biocompatibility and good biodegradability, is also a potent carrier for delivering antitumor drugs. The objective of this study was to develop pH-sensitive HSA conjugates of THP (HSA-THP), and investigate the release of THP and the cytotoxicity under acidic conditions in vitro for further clinical development. HSA-THP was synthesized by conjugating maleimide hydrazone derivatives of THP with poly-thiolated HSA using 2-iminothiolane, via a thiol-maleimide coupling reaction. We synthesized two types of HSA-THP that contained different amounts of THP (HSA-THP2 and HSA-THP4). Free THP was released from both of the HSA conjugates more rapidly at an acidic pH, and the rates of release for HSA-THP2 and HSA-THP4 were similar. Moreover, both HSA-THPs exhibited a higher cytotoxicity at acidic pH than at neutral pH, which is consistent with the effective liberation of free THP under acidic conditions. These findings suggest that these types of HSA-THPs are promising candidates for further development.

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