UV-VIS and CD-spectroscopic investigations of intermolecular interactions of bile pigments with small proteins

Summary The intermolecular complex formation of bilirubin and biliverdin with two proteins (basic pancreatic trypsin inhibitor and lysozyme) were studied by optical and chiroptical methods. Evidence for specific intermolecular interactions of biliverdin with both proteins was found. Bilirubin forms a soluble complex only with lysozyme.

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UV-VIS und CD-spektroskopische Untersuchungen intermolekularer Wechselwirkungen von Gallenpigmenten mit kleinen Proteinen

Zusammenfassung Die intermolekulare Komplexbildung von Bilirubin und Biliverdin mit zwei Proteinen (basischer pankreatischer Trypsininhibitor und Lysozym) wurden mittels optischer und chiroptischer Spektroskopie untersucht. Für Biliverdin konnten intermolekulare Wechselwirkungen mit beiden Proteinen nachgewiesen werden. Bilirubin bildet nur mit Lysozym einen löslichen Komplex.

     

Reactivity of pyrrole pigments. Part 10 MINDO/3 calculations on bile pigments

The applicability of the MINDO/3 method is evaluated for tetrapyrrolic bile pigments: geometries from already calculated dipyrrolic partial models have been used to reduce the calculation time. Net atomic charges and reactivity parameters obtained from the frontier orbital model, i.e. HOMO and LUMO distribution on the molecule, are reported for several conformations.

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Reaktivität von Pyrrolpigmenten, 10. Mitt. MINDO/3-Rechnungen von Gallenpigmenten

Zusammenfassung Es wird der Einsatz von MINDO/3 für tetrapyrrolische Gallenpigmente beschrieben. Um die Rechenzeit herabzusetzen, wurden geometrische Daten verwendet, die vorher für dipyrrolische Partialstrukturen ermittelt worden waren. Für mehrere Konformationen werden Ladungsdichten und Reaktivitätsparameter nach dem Frontier-Orbital-Modell, nämlich HOMO- und LUMO-Verteilung, berichtet.

     

Reactivity of pyrrole pigments. Part 9 MINDO/3 calculations on dipyrrolic partial models of bile pigments

The applicability of the MINDO/3 method is evaluated for calculations on dipyrrolic partial structures of bile pigments. It is shown that this method cannot be used for an accurate conformational analysis. However, when applying the frontier orbital model for reactivity parameters, a good picture of the HOMO and the LUMO distribution can be obtained in this type of molecules.

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Reaktivität von Pyrrolpigmenten, 9. Mitt. MINDO/3-Rechnungen von dipyrrolischen Partialmodellen von Gallenpigmenten

Zusammenfassung Es werden die Einsatzmöglichkeiten von MINDO/3 für den Fall dipyrrolischer Partialstrukturen der Gallenpigmente aufgezeigt. Die Methode ist für eine genaue Konformationsanalyse nicht geeignet. Unter Verwendung der Reaktionsparameter des Frontier-Orbital-Modells läßt sich jedoch ein gutes Bild der HOMO- und LUMO-Verteilung für diesen Verbindungstyp gewinnen.

     

Reactivity of pyrrole pigments,part 15: On the oxidation of bilirubins and biliverdins

Summary Characteristic oxidation reactions of bilin-1,19-diones (biliverdins) and biladien-ac-1,19-diones (bilirubins) were reinvestigated. These include bromine and iodine oxidation of biliverdin IX, bilirubin IX and their Zn(II) complexes, the reaction described by Siedel (1941) of mesobilirubin XIII dimethyl ester with nitric acid (Gmelin reaction) and Smith's oxidation (1977) of etiobiliverdin IV using Tl triacetate and Pb tetra-acetate. For some of these reaction products new structures were assigned on the basis of their spectrometric data. These structures agreed with the expected reactivity pattern of biliverdins and bilirubins.

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Reaktivität von Pyrrolpigmenten, 15 Mitt.: Über die Oxidation von Bilirubinen und Biliverdinen

Zusammenfassung Einige bekannte Oxydationen von Bilin-1,19-dionen (Biliverdinen) und Biladien-ac-dionen (Bilirubinen) wurden neuerlich untersucht, und zwar die Brom- und Jodoxydation von Biliverdin IX und Bilirubin IX sowie der entsprechenden Zn(II)-Komplexe, die Reaktion des Dimethylesters von Mesobilirubin XIII mit HNO₃ (Gmelinreaktion; Siedel 1941) und Smith's Oxydation von Etiobiliverdin IV mit Thaliumtriacetat und Bleitetraacetat. Für einige Reaktionsprodukte wurden aufgrund spektroskopischer Daten neue Strukturen-konsistent mit dem bekannten Reaktionsverhalten von Biliverdinen und Bilirubinen-formuliert.

     

胆红素的间接极谱测定

在Hg~(2+)(或Hg~+)-EDTA-磷酸钠缓冲溶液中,胆红素可被迅速氧化成浅绿色产物。该产物可在-0.83V(vs.SCE)左右产生一灵敏的极谱波,其导数波高与胆红素浓度在4×10~(-7)～6×10~(-6)mol/L范围内呈线性关系,因此该波可用于胆红素的间接测试。本文对胆红素的氧化机制和极谱波的性质进行了研究。发现胆红素被氧化成了胆绿素,而所产生的极谱波为一催化波。     

胆红素的间接光度测定

本文研究了在ｐＨ１０的氨－氯化铵溶液中铜对胆红素的催化氧化作用及其氧化产物胆绿素与铜形成络合物的性质。该络合物在３４０ｎｍ波长处有最大吸收，可用于对胆红素的间接光度测定。其线性范围为１．２×１０＾－６～３．０×１０＾－５ｍｏｌ／Ｌ。     

胆绿素还原酶电极及电位法测定胆红素的研究

本文研制了胆绿素还原酶电极,采用电位法测定胆红素。胆绿素还原酶以牛血清白蛋白和戊二醛固定化制成酶膜,覆盖在石墨电极上在辅酶Ⅰ存在下进行测定,铁氰离子作为电子传递介质。胆红素在空气存在下氧化为胆绿素,再以胆绿素还原酶电极进行检测。线性响应范围为1×10~(-6)-1×10~(-4)mol/L胆绿素(胆红素),酶膜寿命约60h。本法可在水溶液中测定胆红素。     

胆红素和胆绿素的电化学行为初探

本文用电化学方法和光谱方法对胆红素和胆绿素在磷酸钠溶液（ｐＨ１１．５）中的电化学行为进行了研究。发现胆红素在磷酸钠溶液中可在－０．２５Ｖ、－１．３２Ｖ和－１．４７Ｖ（ｖｓ．ＳＣＥ）左右产生三个阴极化波，在－０．２５Ｖ左右产生一阳极化波，其中－０．２５Ｖ左右处的一对波被证实为可逆波，由胆红素与汞（Ⅱ）配合物的氧化还原引起，而另外二波均为不可逆波，由胆红素内吡咯环的氧化还原产生。胆绿素可在－０．３４Ｖ和０．９８Ｖ左右产生极谱波，－０．３４Ｖ处波为胆绿素与汞（Ⅲ）配合物的氧化还原所致，－０．９８Ｖ处波为一催化波。胆红素和胆绿素产生的这些波均具有吸附波特性，可用于它们的分析测试。     

Reduction of aldehydes and ketones by sodium dithionite using viologens as electron transfer catalyst

It was found that aromatic aldehydes and ketones could be reduced smoothly at room temperature by sodium dithionite using viologen derivatives as an electron transfer catalyst to obtain the corresponding alcohols in good yields. Viologens (methyl viologen and polymer) acted catalytically and active species in the reduction were quinoid forms which were obtained by two-electron reduction of viologens.     

Reactivity of pyrrole pigments, 4. Part: Deuteration of 5-arylmethylene-3-pyrrolin-2-ones withd 1-trifluoroacetic acid

5-Arylmethylene-3,4-dimethyl-3-pyrrolin-2-ones on treatment withd ₁-trifluoroacetic acid (d ₁-TFA) undergo deuterium substitution at the carbon atom of the methylene bridge. This electrophilic substitution is related to similar deuteration reactions of verdins (bilatrienes-a,b,c). The results obtained can be interpreted by a free energy relationship, assuming that the field effect, becomes negligible by the influence ofTFA.     

Reactivity of pyrrole pigments. part 6: Electrochemical reduction of some s(1h)-pyrromethenones and 5-arylmethylene-3,4-dimethyl-3-pyrrolin-2-ones

The electrochemical reduction of some 5(1H)-pyrromethenones and 5-arylmethylene-3-pyrrolin-2-ones in imethylformamide (DMF) has been studied by polarography and by identification of their electrochemical reduction products. The reduction processes observed depend on the presence on the type of supporting electrolyte. LiClO₄ or tetraethyl ammonium perchlorate (TEAP) and, When TEAP is used, they also depend on the presence of Water. Polarographic curves show two monoelectronic diffusion Waves in anhydrous DMF both with LiCIO₄ and with TEAP. The reaction products from (Z)-3,4-dimethyl-5-[(4-methylphenyl)methylene]-3-pyrrolin-2-one and from (Z)-2-[(3,4-dimethyl-5-oxo-3-pyrrolin-2-yl)-methylene]-1H-pyrrole for the electrolysis at controlled potentials and under different experimental conditions have been isolated and identified.In all cases a stereoselective reductive dimerization occurs but, at second wave potentials, the reduction compounds corresponding to the hydrogenation of the exocyclic double bond are also formed. The electrolysis yields can be optimized in order to make the process synthetically useful.     

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

Bilirubin 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, medium-induced 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 repect 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 (single-photon-timing) techniques were used to supplement the stationary methods. The solution mixtures are composed of a (family of) helically coiled all-Z, 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 meterial 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.     

Reactivity of pyrrole pigments,XXI: Structure and reactivity of Cu(II) and Zn(II) bilindione chelates

Summary Several Mn, Cu, and Zn chelates of etiobiliverdin-IV-, mesobiliverdin-IX, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a neutral radical structure of the ligand; in CH₃OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV- in the solid state shows an intramolecular weak antiferromagnetic coupling d⁹Cu-to--radical (J=–23 cm^–1) and an intermolecular weak antiferromagnetic coupling -radical-to--radical (J=–45 cm^–1). The analogy of this magnetic behaviour to that of the cation radical of metalloporphyrins is discussed.

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Reaktivität von Pyrrolpigmenten, 21. Mitt.: Struktur und Reaktivität von Cu(II)- und Zn(II)-Chelaten von Bilindionen

Zusammenfassung Einige Mn, Cu and Zn Chelate von Etiobiliverdin-IV-, Mesobiliverdin-IX und seinem Dimethylester werden untersucht. Im Komplex koordiniert ein Metallatom (mit der Formalladung II) mit einem Neutralradikal des dreifach NH-deprotonierten Bilindions. Die Reaktivität des Komplexes gegenüber nukleophilen Lösungmitteln entspricht erwartungsgemäß dem eines neutralen -Radikals; in CH₃OH wird er zu Dimethoxybilipurpurin oxidiert. Bei Cu(II)-Etiobiliverdinat-IV beobachtet man im festen Zustand neben schwacher, antiferromagnetischer Kupplung zwischen d⁹Cu und -Radikal (J=–23 cm^–1) auch eine schwache, intermolekulare, antiferromagnetische Wechselwirkung zwischen zwei -Radikalen (J=–45 cm^–1). Dieses magnetische Verhalten wird dem des -Kationradikals von Metalloporphyrinen gegenübergestellt.

     

On the chemistry of pyrrole pigments,LXXXVII: The apomyoglobin heme pocket as a reaction vessel in bile pigment chemistry

Summary An apomyoglobin biliverdin complex was reduced to a bilirubin apomyoglobin complex with retention of the helix chirality of the chromophore. Chelation of the mesobiliverdin-XIII apomyoglobin complex with zinc ions in aqueous solution yielded an enantiomer of the corresponding derivative. These two systems document the possibility of using the heme pocket of apomyoglobin to execute stereospecific reactions. The chiroptical properties of the two product systems are discussed.

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Zur Chemie von Pyrrolpigmenten, 87. Mitt.: Die Häm-Tasche des Apomyoglobins als Reaktionsgefäß für die Chemie von Gallenfarbstoffen

Zusammenfassung Der Apomyoglobin-Biliverdin-Komplex wurde zum entsprechenden Apomyoglobin-Bilirubin-Komplex unter Retention der Helixkonfiguration des Chromophors reduziert. Chelierung des Apomyoglobin-Mesobiliverdin-XIII-Komplexes mit Zinkionen in wäßriger Lösung lieferte ein Enantiomer des entsprechenden Derivates. Diese beiden Systeme dokumentieren die Verwendbarkeit der Häm-Tasche des Apomyoglobins um stereospezifische Reaktionen durchzuführen. Die chiroptischen Eigenschaften der beiden Produktsysteme werden diskutiert.

     

Reactivity of pyrrole pigments,XX. On the structure of Cu(II) and Zn(II) tripyrrin-1-one chelates in solution

Summary The Cu(II) and Zn(II) chelates of 12,14-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one, 12,13-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one, and their sulfonate derivatives are studied. The chelates show the expected structure of an NH dideprotonated ligand chelating the metal ion. However, in the case of the Zn chelate of 12,14-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one the ligand is only monodeprotonated, and the lactam ring is tautomerized to a hydroximino function.

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Reaktivität von Pyrrolpigmenten, 20. Mitt. Über die Struktur von Cu(II)- und Zn(II)-Chelaten von Tripyrrin-1-onen in Lösung

Zusammenfassung Die Cu(II)- und Zn(II)-Chelate von 12,14-Dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-on, 12,13-Dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-on und ihrer Sulfonate wurden untersucht. Erwartungsgemäß findet man einen NH-dideprotonotierten Liganden im Chelat; im Zn-Complex von 12,14-Dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-on ist der Ligand nur einfach deprotoniert, und das Lactam ist zur Hydroximinogruppe tautomerisiert.

     

Exclusive 1-4 reduction of conjugated ketones by sodium dithionite

α - β unsaturated aldehyde and ketones were exclusively reduced to the corresponding saturated aldehyde and ketones by the use of sodium dithionite under phase- transfer catalysis conditions. Neither allylic nor saturated alcohols are formed.     

On the chemistry of pyrrole pigments,XCII: Syntheses of 1,2-bis-pyrrolylethanes

Summary 1,2-bis-Pyrrolylethanes are potential synthesis precursors ofb-homorubins. They were synthesized in two ways: by self coupling of a 5-halomethylpyrrole using VCl₃/LiAlH₄ or by the reduction of 1,2-bis-pyrrolylethenes using Mg-MeOH/Pd-C as catalyst. The yields were 30–40% for the first method and reached 80% for the second one.

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Zur Chemie von Pyrrolpigmenten, 92. Mitt.: Synthesen von 1,2-bis-Pyrrolylethanen

Zusammenfassung 1,2-bis-Pyrrolylethane als potentielle Synthesevorstufen vonb-Homorubinen konnten auf zwei Wegen synthetisiert werden. Beim ersten wurden 5-Halogenmethylpyrrole mit VCl₃/LiAlH₄ dimerisiert; der zweite Weg beruht auf der Reduktion von 1,2-bis-Pyrrolylethenen mit Mg-MeOH/Pd-C als Katalysator. Die Ausbeuten betrugen im ersten Fall um 30–40% und erreichten im zweiten Fall 80%.

     

Beiträge zur Chemie der Pyrrolpigmente, 47. Mitt.

Carrier mediated transport of bilirubin, biliverdin, their dimethylesters and aetiobiliverdin-IV- is measured using a variety of potential carriers like proteins, peptides, tensides and -cyclodextrin in a bulk membrane model. A strong dependence of the transport flux densities on structural details of the carriers as well as of the bile pigments themselves is observed.

     

Improvement and simplification of low-background silver staining of proteins by using sodium dithionite

High sensitivity and low background, the attractive characteristics of the procedure of Blum et al., Electrophoresis 1987, 8, 93-99, for silver staining of proteins in polyacrylamide gels have been improved by sensitizing the gels with sodium dithionite instead of sodium thiosulfate and by equilibration in water after fixation and prior to sensitization. These modifications decrease the background and allow for a longer development period, which in turn increases sensitivity and color contrast. In addition, the colors of the spots are shifted toward colder tones when compared with the original method.