Monthly Archives: September 2023

Rapid On‐Resin N‐Formylation of Peptides as One‐Pot Reaction

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Rapid On-Resin N-Formylation of Peptides as One-Pot Reaction

Fast but not furious. A rapid on-resin N-formylation protocol for peptides was developed using formic acid, acetic anhydride, pyridine, and DMF. This method is simple in execution and provides near quantitative yield independent of peptide length and sequence.


Abstract

N-formylation is a common pre- and post-translational modification of the N-terminus or the lysine side chain of peptides and proteins that plays a role in the initiation of immune responses, gene expression, or epigenetics. Despite its high biological relevance, protocols for the chemical N-formylation of synthetic peptides are scarce. The few available methods are elaborate in their execution and the yields are highly sequence-dependent. We present a rapid, easy-to-use one-pot procedure that runs at room temperature and can be used to formylate protected peptides at both the N-terminus and the lysine side chain on the resin in near-quantitative yields. Only insensitive, storage-stable standard chemicals – formic acid, acetic anhydride, pyridine and DMF – are used. Formylation works for both short and long peptides of up to 34 amino acids and over the spectrum of canonical amino acids.

Synthesis of Naphthalene‐ and Phenanthrene‐Fused Smaragdyrins and Their BF2 Complexes

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Synthesis of Naphthalene- and Phenanthrene-Fused Smaragdyrins and Their BF2 Complexes

Naphthalene- and phenanthrene-fused [22]smaragdyrins BF2 complexes and their [20]smaragdyrin free bases are synthesized by Suzuki-Miyaura coupling, Witting-type methoxymethylenation, methanesulfonic acid-catalyzed cyclization reaction, and demetalation. These fused [22]smaragdyrin BF2 complexes and [20]smaragdyrin free bases show decreased aromatic characters and antiaromatic characters, respectively. These fused compounds exhibit red-shifted and enhanced absorption bands in NIR region.


Abstract

Naphthalene- and phenanthrene-fused [22]smaragdyrin BF2-complexes were synthesized by 1) Suzuki-Miyaura coupling of β-brominated [22]smaragdyrin BF2 complexes with 2-formylarylboronates, 2) Witting-type methoxymethylenation of the formyl group, and 3) methanesulfonic acid-catalyzed cyclization reaction. Subsequently these BF2 complexes were deboronized and oxidized to the corresponding antiaromatic [20]smaragdyrin free bases. The installed fused structures led to decrease of the aromatic characters of the [22]smaragdyrin BF2 complexes and the antiaromatic characters of the [20]smaragdyrin free bases.

ZnGa2O4 : Cr3+@Calcium Phosphate Nanocomposite with Near‐Infrared Persistent Luminescence and High Stability

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ZnGa2O4 : Cr3+@Calcium Phosphate Nanocomposite with Near-Infrared Persistent Luminescence and High Stability

Shine bright: Persistent luminescent Cr-doped ZnGa2O4 (CZGO) is incorporated into an amorphous calcium phosphate (ACP) matrix. Annealing CZGO prior to ACP integration greatly improves its luminescence intensity and duration. Zn2+ redistribution from CZGO to ACP is identified, leading to the formation of Zn3(PO4)2 when immersed in water. The nanocomposite exhibits high stability under prolonged X-ray exposure.


Abstract

Persistent luminescence (PersL) is an optical phenomenon which allows for materials to emit luminescence after ceasing excitation. The long-lasting luminescence is ascribed to the presence of trap states, which can be exploited through the introduction of various dopants and post-synthesis treatment. In this study, ZnGa2O4 : Cr3+ (CZGO), one of the most widely investigated near-infrared-emitting PersL materials, is synthesized in the form of nanoparticles, and incorporated into amorphous calcium phosphate (ACP) to form a luminescent nanocomposite with drug attachment potential. The effects of annealing CZGO in the composite are comparatively studied alongside the composite that contains unannealed CZGO. We find that ACP with annealed CZGO exhibits much higher luminescence intensity and longer PersL duration. The formation of the nanocomposite also results in the redistribution of Zn, and its influence on the composite luminescence intensity and the long-term chemical stability are investigated.

One‐Carbon Homologation of α,β‐Unsaturated Aldehydes: Access to α‐Tertiary β,γ‐Unsaturated Aldehydes

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One-Carbon Homologation of α,β-Unsaturated Aldehydes: Access to α-Tertiary β,γ-Unsaturated Aldehydes

An efficient two-step no purification protocol for the synthesis of enolizable α-subtituted β,γ-unsaturated aldehydes is reported. The developed strategy involves two steps, epoxidation and Meinwald rearrangement, to result in a formal one-carbon homologation of α,β-unsaturated aldehydes enabling the insertion of a CHR unit.


Abstract

An efficient protocol for the synthesis of enolizable α-substituted β,γ-unsaturated aldehydes is reported. The developed strategy involves two steps, epoxidation and Meinwald rearrangement, to result in a one-carbon homologation of α,β-unsaturated aldehydes enabling the insertion of a CHR unit.

Dynamic Metal‐ligand Coordination for Fluorescence Color Regulation of Hydrazone‐based Bistable Photoswitches

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Dynamic Metal-ligand Coordination for Fluorescence Color Regulation of Hydrazone-based Bistable Photoswitches

We have successfully achieved dynamic manipulation of fluorescence color (540 nm to 607 nm) and intensity by altering the counterions of zinc complexes and switching the isomer from Z to E.


Abstract

Achieving effective manipulation of emission color in photoresponsive materials is crucial for various advanced photonic applications. In this study, we designed and synthesized a hydrazone compound 1, ethyl (Z)-2-(2-([2,2′:6′,2′′-terpyridin]-4′-yl)hydrazineylidene)-2-(4-(diphenylamino)phenyl)acetate, which possesses a push-pull structure incorporating triphenylamine and terpyridine. The emission intensity of compound 1 can be repeatedly switched “off” and “on” by irradiation with visible light and UV light, which induces the isomerization transition between the Z and E forms. In addition, compound 1 is capable of changing its emission wavelength from 540 nm to 607 nm through coordination with different zinc salts in toluene/CH2Cl2 mixture (v : v=1 : 1). Importantly, we have successfully achieved dynamic manipulation of fluorescence color and intensity by altering the counterions of zinc complexes and switching the isomer from Z to E. Moreover, both compound 1 and its zinc complexes demonstrate remarkable photoswitchable properties with different fluorescence colors in the thin films. Finally, these films with various fluorescence colors were used for the production of luminescent tags.

[Fe]‐Hydrogenase, Cofactor Biosynthesis and Engineering

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[Fe]-Hydrogenase, Cofactor Biosynthesis and Engineering

[Fe]-hydrogenase contains the FeGP cofactor as the prosthetic group for activation of H2. HcgA−G are involved in the biosynthesis of the cofactor. Most of the biosynthesis reactions were elucidated by structure-to-function analysis and in vitro biosynthesis. We describe the catalytic function of the Hcg proteins and the possibility of engineering of the FeGP cofactor in redesigned hydride-transfer enzymes.


Abstract

[Fe]-hydrogenase catalyzes the heterolytic cleavage of H2 and reversible hydride transfer to methenyl-tetrahydromethanopterin. The iron-guanylylpyridinol (FeGP) cofactor is the prosthetic group of this enzyme, in which mononuclear Fe(II) is ligated with a pyridinol and two CO ligands. The pyridinol ligand fixes the iron by an acyl carbon and a pyridinol nitrogen. Biosynthetic proteins for this cofactor are encoded in the hmd co-occurring (hcg) genes. The function of HcgB, HcgC, HcgD, HcgE, and HcgF was studied by using structure-to-function analysis, which is based on the crystal structure of the proteins and subsequent enzyme assays. Recently, we reported the catalytic properties of HcgA and HcgG, novel radical S-adenosyl methionine enzymes, by using an in vitro biosynthesis assay. Here, we review the properties of [Fe]-hydrogenase and the FeGP cofactor, and the biosynthesis of the FeGP cofactor. Finally, we discuss the expected engineering of [Fe]-hydrogenase and the FeGP cofactor.

Sequence‐Specific Relay Recognition of Multiple Anions: An Interplay between Proton Donors and Acceptors

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Ratiometric detection of analyte is highly deserving since the technique is free from background correction. This work reports the design and synthesis of a pyridine-end oligo p-phenylenevinylene (OPV) derivative, 1 and its application in ratiometric dual-mode (both colorimetric and fluorogenic) recognition of dual anions, bisulphate (LOD= 12.5 ppb) followed by fluoride (LOD= 18.2 ppb) by sequence-specific relay (SPR) technique. The colorless probe turns brown with addition of bisulphate and again becomes colorless with the sequential addition of fluoride ion. In addition to such naked-eye color change, interestingly the ratiometric spectroscopic signals are reversible and evidently, the probe is reusable for several cycles. Besides, in presence of bisulphate, the protonated probe molecules, owing to their larger amphiphilic characteristics, formed self-assembled nanostructures. In addition to colorimetric and fluorescent changes, 1H NMR titration and systematic DFT study evidently establish the underneath proton transfer mechanisms. Such reusable OPV-based chemosensor particularly with the capability of naked-eye recognition of dual anions using the SPR technique is seminal and possibly the first report in the literature.