- Tunable induced circular dichroism in gels
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The ICD phenomenon has drawn a lot of attention in recent years in applicable fields such as chiral sensing and chiroptical devices. In this work, we first gaze at the issues of thin spin-coated films not being able to deliver consistent ICD signals. A hypothesis of the underlying problem is proposed through a brief elucidation of the spin-coating process. To confirm and eliminate the uncontrollable dynamic factors with spin coating, we then dedicate our efforts to develop a new gel system based on chiral L-/D-N′,N′-Dibenzoyl-cystine. Achiral dye molecules are intercalated in a DBC gel through a “one-step” preparation procedure. Compared to the former spin-coating system, significantly improved reproducibility of the new gel system is demonstrated. Besides, the ICD signals can be customized in a broad spectral range (wavelength tunability) by substituting dye molecules. Finally, we discuss the potential applications of this interesting system.
- Boekhoven, Job,Brandt, Viktoria Katharina,Fehn, Natalie,Heiz, Ueli,Kartouzian, Aras,Stasi, Michele,Xue, Yu
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- Dynamic covalent chemistry in aqueous solution by photoinduced radical disulfide metathesis
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Photoinduced radical disulfide metathesis (PRDM) is a dynamic covalent reaction that requires UV light to induce the homolytic cleavage of the disulfide bond, thus offering the opportunity to construct dynamic covalent systems that are dormant and can be photo-Activated on demand. In this work, we showcase how PRDM can be utilized in aqueous solution and demonstrate its potential by generating a UV responsive hydrogel from an asymmetrical disulfide precursor.
- Klepel, Florian,Ravoo, Bart Jan
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supporting information
p. 3840 - 3842
(2017/07/11)
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- Chemical interaction between polyphenols and a cysteinyl thiol under radical oxidation conditions
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Chemical interaction between polyphenols and thiols was investigated under radical oxidation conditions using a model cysteinyl thiol derivative, N-benzoylcysteine methyl ester. The radical oxidation was carried out with a stoichiometric amount of 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the decreases in the amounts of polyphenols and the thiol were measured by HPLC analysis. Cross-coupling products between various polyphenols and the thiol were examined by LC-MS in reactions that showed decreases in both the polyphenols and the thiol. The LC-MS results indicated that three phenolic acid esters (methyl caffeate, methyl dihydrocaffeate, and methyl protocatechuate) and six flavonoids (kaempferol, myricetin, luteolin, morin, taxifolin, and catechin) gave corresponding thiol adducts, whereas three polyphenols (methyl ferulate, methyl sinapate, and quercetin) gave only dimers or simple oxidation products without thiol substituents. Thiol adducts of the structurally related compounds methyl caffeate and methyl dihydrocaffeate were isolated, and their chemical structures were determined by NMR analysis. The mechanism for the thiol addition was discussed on the basis of the structures of the products.
- Fujimoto, Aya,Masuda, Toshiya
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experimental part
p. 5142 - 5151
(2012/10/07)
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- Chelate oxorhenium to assemble new integrin antagonists
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Assembly of independent chemical modules through oxorhenium coordination by a NS2 + S chelation motif was applied to the synthesis of RGD (Arg-Gly-Asp) analogs. Modules were assembled through oxorhenium chelation to give a series of 18 metal complexes in good yields and satisfactory purities. Screening of these oxorhenium coordinates as antagonists of integrins αVβ3, αIIbβ3 and αVβ5 led to the identification of 3 bioactive compounds that exhibit submicromolar affinities for the 3 integrins. Preliminary studies showed that the corresponding oxotechnetium complexes are stable in mice plasma and therefore could be proposed for the molecular imaging of pathologies that overexpress integrins αVβ3 and αVβ5.
- Le Gal, Julien,Gonera, Marta,Lelait, Marie-Anne,Servent, Denis,Dugave, Christophe
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body text
p. 880 - 886
(2012/03/26)
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- Dynamic combinatorial mass spectrometry leads to metallo-β-lactamase inhibitors
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The use of protein ESI mass spectrometry under non-denaturing conditions to analyze a dynamic combinatorial library of thiols/disulfides with the BcII metallo-β-lactamase enabled the rapid identification of an inhibitor with a Ki of 1 μM. The study exemplifies the utility of protein-MS for screening dynamic mixtures of potential enzyme-inhibitors.
- Liénard, Beno?t M. R.,Hüting, Rebekka,Lassaux, Patricia,Galleni, Moreno,Frère, Jean-Marie,Schofield, Christopher J.
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p. 684 - 688
(2008/09/18)
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- Anatomy of a gel. Amino acid derivatives that rigidify water at submillimolar concentrations
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On the basis of suggestive X-ray data, 14 aroyl L-cystine derivatives were designed, synthesized, and examined for their ability to gelate water. Several members of this amino acid family are remarkably effective aqueous gelators (the best being one that can rigidify aqueous solutions at 0.25 mM, ca. 0.01%, in less than 30 s!). A few of the analogues separate from water as crystals, indicating a close relationship between gelation and crystallization. All effective gelators self-assemble into fibrous structures that entrain the solvent in the capillary spaces among them. Hydrogen-bonding sites on the compounds that might stabilize the fibers were identified from specific substitutions that replace a hydrogen donor with a methyl group, enhance the hydrogen-accepting ability of a carbonyl oxygen, or promote the hydrogen-donating ability of an amide proton. The structural variations were characterized via minimal gelation concentrations and times, X-ray crystallography, light and electron microscopy, rheology, and calorimetry. The multiple techniques, applied to the diverse compounds, allowed an extensive search into the basis of gelation. It was learned, for example, that the compound with the lowest minimum gelator concentration and time also has one of the weakest gels (i.e., it has a low elastic modulus). This is attributed to kinetic effects that perturb the length of the fibers. It was also argued that π/π stacking, the carboxyl carbonyl (but not the carboxyl proton), and solubility factors all contribute to the stability of a fiber. Polymorphism also plays a role. Rheological studies at different temperatures show that certain gels are stable to a 1-Hz, 3-Pa oscillating shear stress at temperatures as high as 90 °C. Other gels have a 'catastrophic' break at lower temperatures. Calorimetric data indicate a smooth transition from gel to sol as the temperature is increased. These and other issues are discussed in this 'anatomy' of a gel.
- Menger,Caran
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p. 11679 - 11691
(2007/10/03)
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