Spectrographic Contributions to Lignin Chemistry. IX. Absorption Properties of Some 4-Hydroxyphenyl, Guaiacyl, and 4-Hydroxy-3,5-dimethoxyphenyl Type Model Compounds for Hardwood Lignins.

Aulin-Erdtman, Gunhild; Sandén, Roland; Krogh-Moe, J.; Schwieter, Ulrich; Paasiv́irta, Jaakko

doi:10.3891/acta.chem.scand.22-1187

Cited by 72 publications

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“…1H NMR spectra unambiguously show that, :.fter irradiation of trans-p-coumaric acid with UV light, trans-cis isomerization occurs, as was previously demonstrated for this and other cinnamic acid derivatives [17][18][19]. Fig.…”

Section: Photo-isomerization Of Pcoumaric Acid In Aqueous Solutionsupporting

confidence: 66%

“…12 ILA. On-cohmm detection was performed at 284 and 265 nm, the wavelengths of maximal absorbance of trans-and c/s-p-coumaric acid, respectively [17].…”

Section: I'~mentioning

confidence: 99%

“…2B cannot directly be calculated from the ratio of the peak area of each isomer, because of their ,,~dely different extinction coefficients in the UV region. The molar extinction coefficient at 284 nm is significantly lower for the cis isomer, as compared to trans-p-coumaric acid [17]. Using the proper extinction coefficients, the ratio of the two isomers, as present in the mixture analyzed in the experi- ment shown in Fig.…”

Section: Photo-isomerization Of Pcoumaric Acid In Aqueous Solutionmentioning

confidence: 99%

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Evidence for trans‐cis isomerization of the p‐coumaric acid chromophore as the photochemical basis of the photocycle of photoactive yellow protein

et al. 1996

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Analysis of the chromophore p-coumaric acid, extracted from the ground state and the long-lived blue-shifted photocycle intermediate of photoactive yellow protein, shows that the chromophore is reversibly converted from the trans to the cis configuration, while progressing through the photocycle. The detection of the trans and ¢is isomers was carried out by high performance capillary zone electrophoresis and further substantiated by tH NMR spectroscopy. The data presented here establish the photo.isomerization of the vinyl double bond in the chromophore as the photochemical basis for the photocycle of photoactive yellow protein, a euhacterlal photosensory protein. A similar isomerization process occurs in the structurally very different sensory rhodopsins, offering an explanatimJ for the strong spectroscopic similarities between photoactive yellow protein and the sensory rhodopsins. This is the first demonstration of light-induced isomerization of a chromophore double bond as the photochemical basis for photosensing in the domain of Bacteria.

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Section: Photo-isomerization Of Pcoumaric Acid In Aqueous Solutionsupporting

confidence: 66%

“…12 ILA. On-cohmm detection was performed at 284 and 265 nm, the wavelengths of maximal absorbance of trans-and c/s-p-coumaric acid, respectively [17].…”

Section: I'~mentioning

confidence: 99%

Section: Photo-isomerization Of Pcoumaric Acid In Aqueous Solutionmentioning

confidence: 99%

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Evidence for trans‐cis isomerization of the p‐coumaric acid chromophore as the photochemical basis of the photocycle of photoactive yellow protein

et al. 1996

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“…A decrease in pH spontaneously transforms PYP to a blue-shifted state, resembling pB (1). 2 Free pCA in aqueous solvents and at neutral pH absorbs maximally at 284 nm (20); however, within the chromophorebinding pocket in the apoprotein, the absorption of the chromophore is strongly red-shifted (to 446 nm). Three contributions to this shift have been identified (6,7,19): (i) formation of the thiol ester bond between pCA and Cys-69, (ii) deprotonation of the chromophore (21), and (iii) specific protein-chromophore interactions.…”

Section: ϫ3mentioning

confidence: 99%

Spectral Tuning, Fluorescence, and Photoactivity in Hybrids of Photoactive Yellow Protein, Reconstituted with Native or Modified Chromophores

Kroon¹,

Hoff²,

Fennema

et al. 1996

Journal of Biological Chemistry

100

133

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Photoactive yellow proteins (PYPs) constitute a new class of eubacterial photoreceptors, containing a deprotonated thiol ester-linked 4-hydroxycinnamic acid chromophore. Interactions with the protein dramatically change the (photo)chemical properties of this cofactor. Here we describe the reconstitution of apoPYP with anhydrides of various chromophore analogues. The resulting hybrid PYPs, their acid-denatured states, and corresponding model compounds were characterized with respect to their absorption spectrum, pK for chromophore deprotonation, fluorescence quantum yield, and Stokes shift. Three factors contributing to the tuning of the absorption of the hybrid PYPs were quantified: (i) thiol ester bond formation, (ii) chromophore deprotonation, and (iii) specific chromophore-protein interactions. Analogues lacking the 4-hydroxy substituent lack both contributions (chromophore deprotonation and specific chromophore-protein interactions), confirming the importance of this substituent in optical tuning of PYP. Hydroxy and methoxy substituents in the 3-and/or 5-position do not disrupt strong interactions with the protein but increase their pK for protonation and the fluorescence quantum yield. Both deprotonation and binding to apoPYP strongly decrease the Stokes shift of chromophore fluorescence. Therefore, coupling of the chromophore to the apoprotein not only reduces the energy gap between its ground and excited state but also the extent of reorganization between these two states. Two of the PYP hybrids show photoactivity comparable with native PYP, although with retarded recovery of the initial state.

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“…The UV-Vis spectra of original and fractionated lignocresols from spruce had a sharp band only at 280 nm, and hardly shoulder or band at longer wavelengths which exist in MWL. 15,16 These indicate selective and effective grafting of p-cresol at reactive sites in the side chains, leading to the disappearance of conjugated systems in the molecular. 15 But the UV-Vis spectra of low molecular weight fraction (Fr-5) of birch lignocresol had slightly higher absorbance at wavelengths longer than 300 nm, compared with high and middle molecular weight fractions.…”

Section: Ft-ir and Uv-vis Spectra Of Fractionated Lignocresolsmentioning

confidence: 99%

Polymer Structure of Lignophenol I —Structure and Function of Fractionated Lignophenol—

Mikame

Funaoka

2006

Polym J

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ABSTRACT:A polymer structure and function of lignophenol was examined by various structural analysis of lignophenols fractionated with preparative SEC. The base unit of lignophenol is 1,1-bis (aryl) propane-2-O-aryl ether unit in all the molecular weight areas by NMR analysis. But the amounts of combined cresol and phenolic hydroxyl groups were increased with decreasing molecular weight of fractionated lignophenols. The protein-adsorbing capacities and thermoplastic property of fractionated lignophenols differed with the molecular weights.[doi:10.1295/polymj.PJ2005142] KEY WORDS Lignin / Fractionation / Molecular Weight / Polymer Structure / Phase-separation System / Lignophenol / Lignin is the most abundant natural polymer next to cellulose and exists in plant cell walls as one of the major constituents. However, in contrast to the importance and potential of lignin in nature, lignin-based products have scarcely been in human life. This strange phenomenon is due to complicated structure and reactivity of lignin. Lignin is biosynthesized via random radical coupling of p-hydroxycinnamyl alcohols, which is initiated by enzymatic one-electron oxidation of phenolic hydroxyl groups.1,2 Thus lignin has a variety of inter-unit linkage and an amorphous three-dimensional network polymer.3,4 Furthermore, complicated modifications of the lignin structure are caused through isolation process from the cell wall. Presently kraft lignin which is the most abundant commercial lignin can be produced mainly as byproducts in kraft pulping process. However the lignin from kraft pulping process are burned for the production of energy for pulping process, so they are not utilized as raw materials for chemicals. In order to utilize the kraft lignin as more valuable materials, the conversion of kraft lignin to functional polymers has been attempted by many researchers, 5-8 but any industrial use of the lignin has not been accomplished. Therefore it is difficult to change highly modified lignin into functional polymers.Recently lignin-based functional polymer (lignophenols) has originally been designed and their synthesis process from native lignin (original lignin in wood) has been developed. 9 This process includes the phase-separation reaction system composed of phenol derivatives and concentrated acid. In the process, native lignin was modified by selectively grafting phenol derivatives to benzyl position, the most reactive sites, to give lignophenols that remain the original interunit linkage of lignin and have high phenolic content (Scheme 1).The lignophenols have several unique functions, for example lignophenols indicate an apparent solidliquid transformation at ca. 130 C in hardwood and at ca. 170 C in softwood, and high immobilization capability for proteins (enzyme). 10,11 In this study, the correlation between these unique functions of lignophenols and polymer structures were investigated. EXPERIMENTAL Wood and Lignin PreparationsAir-dried wood samples were ground to pass an 80 mesh screen and extracted with ethanol-benzene (...

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Spectrographic Contributions to Lignin Chemistry. IX. Absorption Properties of Some 4-Hydroxyphenyl, Guaiacyl, and 4-Hydroxy-3,5-dimethoxyphenyl Type Model Compounds for Hardwood Lignins.

Cited by 72 publications

References 0 publications

Evidence for trans‐cis isomerization of the p‐coumaric acid chromophore as the photochemical basis of the photocycle of photoactive yellow protein

Evidence for trans‐cis isomerization of the p‐coumaric acid chromophore as the photochemical basis of the photocycle of photoactive yellow protein

Spectral Tuning, Fluorescence, and Photoactivity in Hybrids of Photoactive Yellow Protein, Reconstituted with Native or Modified Chromophores

Polymer Structure of Lignophenol I —Structure and Function of Fractionated Lignophenol—

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