Luminescence of coelenterazine derivatives with C-8 extended electronic conjugation

Replacement of the methylene group at the C-8 position with an extended electronic conjugation is a new promising method to develop red-shifted coelenterazine derivatives. In this paper, we have described an oxygen-containing coelenterazine derivative with a significant red-shifted(63 nm)bioluminescence signal maximum relative to coelenterazine 400a(Deep Blue C~(TM), 1). In cell imaging, the sulfur-containing coelenterazine derivative displayed a significantly(1.77 ± 0.09;P≤0.01) higher luminescence signal compared to coelenterazine 400 a and the oxygen-containing coelenterazine derivative exhibited a slightly(0.74 ± 0.08; P≤0.05) lower luminescence signal. It is beneficial to understand further the underlying mechanisms of bioluminescence.     

Efficient synthesis and antioxidant activity of coelenterazine analogues

A convenient and highly convergent method for the synthesis of new imidazo[1,2-a]pyridine-based coelenterazine analogues is reported. The imidazo[1,2-a]pyridine core was constructed through a condensation between 2-aminopyridine analogues and arylglyoxals. Additionally, a new approach to the synthesis of benzylglyoxals was introduced. The imidazo[1,2-a]pyridines display moderate antioxidant activities at a low micromolar level in 2,2-diphenyl-1-picrylhydrazyl (DPPH).     

Bioluminescence activity of Latia luciferin analogues: replacement of the 2,6,6-trimethylcyclohexene ring onto the methyl-substituted phenyl groups

A series of Latia luciferin analogues having methyl-substituted phenyl groups instead of the natural 2,6,6-trimethylhexene ring was synthesized and their bioluminescence activity were measured. The Latia luciferase was found to be able to moderately recognize the appropriately methyl-substituted phenyl analogues with the same light production kinetics as that of natural luciferin.     

Synthesis of Latia luciferin benzoate analogues and their bioluminescent activity

The bioluminescent system of the univalve shell Latia neritoides exhibits a luciferin-luciferase reaction. We study the enol formate structure of Latia luciferin, which is expected to be important for luminescent activity. The Latia luciferin analogues with an enol substituted benzoate moiety were synthesized and their bioluminescent activity was measured. The Latia luciferin benzoate analogues delay emission for natural luciferin in bioluminescence, indicating that the Latia bioluminescent activity can be controlled by the design of the enol ester.     

QM/MM Investigations on the Bioluminescent Decomposition of Coelenterazine Dioxetanone in Obelin

The bioluminescent mechanism of colenterazine dioxetanone(CZD) in the photoprotein of Obelia(obelin) was investigated by the combined quantum and molecular mechanics(QM/MM) method at TD-DFT level, which involved the real protein environment in decomposition of 1,2-dioxetanones. The anionic decomposition of CZD in (CZD+H₂O)^- model can go through a charge transfer(CT) catalyzed asynchronous-concerted process, which can be elucidated by the gradual reversible CT initiated luminescence(GRCTIL) mechanism. The neutral CZD in (CZDH+H₂O) decomposes through an uncatalyzed non-CT biradical process. The anionic decomposition catalyzed by CT, in which the S₀/S₁ surface "double crossing" hence has ability to provide high quantum yield of singlet chemiexcitation is thus more possible in bioluminescence of photoprotein.     

Synthesis and electronic properties of hexylthiophene-octaethylporphyrin derivatives (HTh-OEP) connected with diacetylene linkage: substituent effect on the electronic structure of the extended HTh-OEP conjugation system

Octaethylporphyrin (OEP) was combined with 2-substituted 3-hexylthiophenes (HTh) by diacetylene linkage to afford the highly extended conjugation system (HTh-OEP). Their absorption spectral properties were examined, proving that the electronic structure of OEP is affected by the more electron-withdrawing substituents through the diacetylene linkage more dramatically. The substituent effect on the HTh-OEP conjugation system is much outstanding, as compared with that on the corresponding benzene system (Bzn-OEP).     

Effect of extended conjugation with a phenylethynyl group on the fluorescence properties of water-soluble arylboronic acids

Boronic acids that change fluorescence properties upon sugar binding are very important reporter units for the development of small molecule lectin mimics (boronolectins). Aimed at developing long wavelength fluorescent boronic acid reporter compounds, we have designed and synthesized a series of boronic acid analogs 2a-d with an extended π conjugation. Such designs are based on earlier fluorescent boronic acids that change fluorescence properties upon sugar binding. Compared with the corresponding parent chromophores, these new compounds with extended conjugations show longer excitation and emission wavelengths as designed. The patterns of fluorescence changes for the new compounds are also different from that of the corresponding parent compounds.     

给、吸电子基团对芳香共轭体系电子结构影响的密度泛函理论研究

采用密度泛函理论,在B3LYP／6—31G^＊方法水平上对8个连接有给、吸电子基团的芳香共轭体系的稳定性、偶极矩、静电荷分布和前线轨道能级进行了研究,并采用TD／DFT方法进一步研究了它们的电子光谱．结果表明a-1,b-1,c-1和d-2分子比它们的同分异构体要稳定;对于苯、呋喃、吡咯与乙烯形成的共轭体系,吸电子基团连接在乙烯一端,给电子基团连接在芳香环上使体系的偶极距增强,而吡啶则相反;前线轨道能级差较小的是吸电子基团连接在芳香环一端的体系,相应的分子最大吸收波长也较大．     

Study of the electronic structure of organogermanes with extended coordination sphere of germanium

The spatial and electronic structures of some organogermanes with extended coordination spheres of the metal were calculated using AMPAC and HYPER CHEM 4.0 program packages. Interatomic distances, bond angles, torsion angles, atomic charges, electron densities, bond orders, parameters of localized and canonical molecular orbitals,etc. were determined. The nature of the additional intramolecular O→Ge interaction in the molecules of these compounds was considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 383–387, March, 1998.     

Synthesis of granulatimide analogues bearing a maleimide instead of an imidazole heterocycle

A synthesis in a few steps of a new family of granulatimide analogues was performed. In the new compounds, the aromatic framework of granulatimide is modified by replacement of the imidazole unit by a maleimide moiety. The synthesis of a water-soluble analogue is also presented.     

Efficient synthesis of extended guanine analogues designed for recognition of an A·T inverted base pair in triple helix based-strategy

We report herein an efficient synthesis of new nucleosides N1, N2, and N3 as extended guanine analogues, derived from aminobenzimidazole and thymine or 5-substituted uracil. These nucleosides were devised for the recognition of an A·T inverted base pair by three hydrogen bonds, in triple helix-based technology.     

Classification of white wine aromas with an electronic nose

This paper reports the use of a tin dioxide multisensor array based electronic nose for recognition of 29 typical aromas in white wine. Headspace technique has been used to extract aroma of the wine. Multivariate analysis, including principal component analysis (PCA) as well as probabilistic neural networks (PNNs), has been used to identify the main aroma added to the wine. The results showed that in spite of the strong influence of ethanol and other majority compounds of wine, the system could discriminate correctly the aromatic compounds added to the wine with a minimum accuracy of 97.2%.     

New tricyclic geldanamycin analogues from an engineered strain of Streptomyces hygroscopicus JCM4427

Two tricyclic geldanamycin analogues, DHQ5 (1) and DHQ6 (2), were produced by a combinatorial mutant (AC15) contained a site-directed mutagenesis on the geldanamycin polyketide synthase (PKS) gene with inactivation of the post-PKS tailoring genes (gel7) of Streptomyces hygroscopicus JCM4427. The structural diversity of tricyclic geldanamycin analogues is due to the formation of unusual additional rings, which are formed by alkylation of the C-21 position by C-12 in DHQ5 (1) and by electrophilic addition of the C-15 hydroxyl group to the double bond (C-8-C-9), which leads to the migration of the double bond (to C-7-C-8) and the elimination of a carbamoyloxy group in DHQ6 (2).     

(E)-2-Benzylidenebenzocyclanones: Part VII. Investigation of the conjugation reaction of two cytotoxic cyclic chalcone analogues with glutathione: an HPLC–MS study

Abstract  

The non-enzyme-catalyzed reaction of reduced glutathione (GSH) with two tumor cell cytotoxic cyclic chalcone analogues was investigated by reversed-phase high-performance liquid chromatography (RP-HPLC). HPLC analysis of the reaction mixtures indicated the formation of two diastereomeric chalcone–GSH adducts in each case, whose structural assignments were supported by MALDI-TOF-MS and HPLC–MS with electrospray ionization (ESI) measurements. Such reactivity accounts for the previously observed effect of the two cyclic chalcone analogues on the in vivo cellular thiol level of Jurkat T cells.     

Synthesis of isogranulatimides A and B analogues possessing a 7-azaindole unit instead of an indole moiety

The synthesis of a new family of isogranulatimides analogues is described in which a 7-azaindole replaces the indole moiety. The key step is the photocyclization of the aza didemnimide intermediates which leads to two isomeric analogues of isogranulatimides A and B. A derivative bearing a carbohydrate part linked to the azaindole via a β-N-glycosidic bond was also prepared.     

Analysis of time-dependent conjugation of gold nanoparticles with an antiparkinsonian molecule by using curve resolution methods

In this work, the time-dependent conjugation process between a thiolated molecule (with anti-parkinsonian properties) and gold nanoparticles has been monitored and studied by the combined use of fast acquisition Ultra Violet–Visible (UV–Vis) spectra and the ability of Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) technique. From the highly informative kinetic profiles obtained it was possible to extract quantitative and qualitative information of the conjugation process which includes i) time-dependent concentration profiles and pure spectra of species involved on conjugation process, ii) estimation of molecule concentration necessary for the completeness of the conjugation reaction, iii) molecule footprint and iv) free energy of molecule adsorption.     

1,4-Dihydropicolinic acid derivatives: novel NADH analogues with an altered connectivity pattern

Sodium dithionite reduction of α-substituted N-alkylpyridinium salts (derived from picolinic acid derivatives) afforded the corresponding 1,4-dihydropyridines with a new substitution pattern, in which the electron-withdrawing group is at the α-position. These compounds promote biomimetic reductions and are hence considered functional NADH analogues.     

Furan derivatives of tellurium: Synthesis and structural comparison with the thiophene analogues

α-Bromo-2-acetylfuran adds oxidatively to elemental tellurium and aryltellurium(II) bromide at ambient temperature to afford (2-furoylmethyl)tellurium(IV) dibromides, (FuCOCH₂)₂TeBr₂ (1b) and Ar(FuCOCH₂)TeBr₂ (Fu = 2-C₄H₃O; Ar = 1-C₁₀H₇, 2b; 2,4,6-Me₃C₆H₂, 3b). The iodo analogues 1c-3c can be obtained by metathesis of the bromides with an alkali iodide. Condensation reactions of the parent methyl ketone with Te(IV) chlorides results in the corresponding chloro analogues, (FuCOCH₂)₂TeCl₂ (1a) and Ar(FuCOCH₂)TeCl₂ (2a, 3a and Ar = 4-MeOC₆H₄ (4a)). These diorganotellurium dihalides are reduced with aqueous bisulfite to diorganotellurides 1-3, which can be oxidized readily with dihalogens to the desired diorganotellurium(IV) dihalides. The tellurated furan derivative, bis(2-furyl)tellurium(II), Fu₂Te (5), obtained by detelluration of bis(2-furyl)ditelluride with electrolytic copper, gives crystalline bis(2-furyl)tellurium(IV) dichloride (5a) upon chlorination. Crystal structures of Te(IV) compounds 1a, 1b, 2a-4a, and the telluride 3 together with its thiophene analogue (2,4,6-Me₃C₆H₂)((2-C₄H₃S)COCH₂)Te, 6 have been studied. Among the Te(IV) compounds, the functionalized organic moiety, FuCOCH₂-, behaves as a (C, O) chelating ligand, resulting in a intramolecular 1,4-Te?O secondary bonding interaction. Such an interaction is absent in Te(II) compounds 3 and 6, though they differ in the conformation adopted by the organic ligand. The chalcogen atoms in the heteroaroyl moiety are trans in 3 but cis in 6 which also possesses intermolecular Te?O interaction in its lattice.