2-Azidoethoxy derivatives of 2-aminocyclohexanecarboxylic acids (ACHC): interesting building blocks for the synthesis of cyclic β-peptide conjugates

Oligomers of cyclic-β-aminoacids possess a high resistance to peptidase-catalyzed hydrolysis and display a high intrinsic tendency to adopt regular secondary structures. These characteristics are attractive to develop new biologically active substances. However, cyclic-β-peptides often show limited solubility in water and cannot be conjugated to biologically relevant fragments, such as oligosaccharides, which are often essential for full biological activity of natural α-peptides. In this article, we report the synthesis of one trans- and one cis-2-aminocyclohexanecarboxylic acid (ACHC), both functionalized with a hydroxy group, to increase the solubility in water, and an azidoethoxy group to allow the synthesis of cyclic-β-peptide conjugates by a ‘click reaction’.     

Transformations of chromanol and tocopherol and synthesis of ascorbate conjugates

α-Tocopherol and as a model compound pentamethylchromanol could be transferred into simple and more complex 5a-ether derivatives including galactopyranose as well as ascorbic acid conjugates. Following elaboration of a glucopyranoside spacer element this could be used for tethering the vitamin E and the vitamin C components to give novel conjugates for subsequent biostudies concerning their proposed synergism of antioxidant properties in tissues.     

Laccase as a New Enzymatic Label for Enzyme Immunoassay

Abstract

A new immunochemical reagent is suggested containing as an enzyme marker laccase obtained from the cultural liquid of basidial fungi Coriolus hirsutus. The feasibility of immuno-laccase conjugates in different versions of immunoanalysis (sandwich, competitive and indirect enzyme immunoassay) was demonstrated. The assay based on antibodvlaccase conjugates is simpler than that employing antibody-peroxidase conjugates, since in the former case air oxygen is used as the second substrate of the enzymatic reaction.     

Design and synthesis of new carbohydrate-lithocholic acid conjugates linked via 1,2,3-triazole rings

In this work, we report the synthesis of a novel carbohydrate-lithocholic acid conjugate linked through of 1,2,3-triazole rings and its derivatives in good to excellent yields. The conjugate was synthesized via copper-catalyzed azide?alkyne cycloaddition (CuAAC) from methyl 4,6-O-benzylidene-2,3-di-O-propargyl-α-d-glucopyranoside and methyl 3-azidolithocholate. The structures of all new compounds were properly characterized by infrared (IR), high-resolution mass spectroscopy (HRMS) and one- and two-dimensional nuclear magnetic resonance (NMR).     

Synthesis of nucleoside-amino acid conjugates containing boranephosphate, boranephosphorothioate and boranephosphoramidate linkages

Conjugates of 3^′-azido-2^′,3^′-dideoxythymidine (AZT) and 2^′,3^′-didehydro-2^′,3^′-dideoxythymidine (D4T) with the hydroxyl group of tyrosine containing boranephosphate and boranephosphorothioate moieties were prepared via the oxathiaphospholane and dithiaphospholane methodology as a mixture of P-diastereomers. Their structures were confirmed by MS analysis and ¹H, ³¹P NMR spectroscopy. It has been shown that the boranephosphorothioate linkage is unstable under acidic conditions. The first nucleoside-alanine conjugates connected through a boranephosphoramidate linkage were also obtained.     

Oxathiaphospholane Approach to the Synthesis of Conjugates of Amino Acids Methyl Esters with Nucleosides

Based upon 1,3,2-oxathiaphospholane chemistry, 5'-O-derivatization of nucleosides with the O-methyl esters of amino acids was performed and corresponding conjugates were obtained in satisfactory yield.     

Conjugates of methyl 6-aminopenicillanate with biscatechol-hydroxamate chelators: synthesis and siderophoric activity

A synthesis of biscatechol-hydroxamate and triscatechol chelators and of conjugates of the former with methyl 6-aminopenicillanate is described. It is based on the multiple use of the ylide Ph₃PCCO as a C₂ building block in one-pot coupling reactions between aldehydes and alcohols or amines. These conjugates were actively internalized into siderophore-deficient Escherichia coli mutant H5596.     

Enzyme-Polymer-Conjugate-Based Pickering Emulsions for Cell-Free Expression and Cascade Biotransformation

In this study, we addressed the limitations of conventional enzyme-polymer-conjugate-based Pickering emulsions for interfacial biocatalysis, which traditionally suffer from nonspecific and uncontrollable conjugation positions that can impede catalytic performance. By introducing a non-canonical amino acid (ncAA) at a specific site on target enzymes, we enabled precise polymer-enzyme conjugation. These engineered conjugates then acted as biocatalytically active emulsifiers to stabilize Pickering emulsions, while encapsulating a cell-free protein synthesis (CFPS) system in the aqueous phase for targeted enzyme expression. The resulting cascade reaction system leveraged enzymes expressed in the aqueous phase and on the emulsion interface for optimized chemical biosynthesis. The use of the cell-free system eliminated the need for intact whole cells or purified enzymes, representing a significant advancement in biocatalysis. Remarkably, the integration of Pickering emulsion, precise enzyme-polymer conjugation, and CFPS resulted in a fivefold enhancement in catalytic performance as compared to traditional single-phase reactions. Therefore, our approach harnesses the combined strengths of advanced biochemical engineering techniques, offering an efficient and practical solution for the synthesis of value-added chemicals in various biocatalysis and biotransformation applications.     

Trimming Crystallizable Fragment (Fc) Glycans Enables the Direct Enzymatic Transfer of Biomacromolecules to Antibodies as Therapeutics**

Glycoengineering has provided powerful tools to construct site-specific antibody conjugates. However, only small-molecule payloads can be directly transferred to native or engineered antibodies using existing glycoengineering strategies. Herein, we demonstrate that reducing the complexity of crystallizable fragment (Fc) glycans could dramatically boost the chemoenzymatic modification of immunoglobulin G (IgG) via an engineered fucosyltransferase. In this platform, antibodies with Fc glycans engineered to a simple N-acetyllactosamine (LacNAc) disaccharide are successfully conjugated to biomacromolecules, such as oligonucleotides and nanobodies, in a single step within hours. Accordingly, we synthesized an antibody-conjugate-based anti-human epidermal growth factor receptor 2 (HER2)/ cluster of differentiation 3 (CD3) bispecific antibody and used it to selectively destroy patient-derived cancer organoids by reactivating endogenous T lymphocyte cells (T cells) inside the organoid. Our results highlight that this platform is a general approach to construct antibody-biomacromolecule conjugates with translational values.     

Improvement of surface plasmon resonance biosensor with magnetic beads via assembled polyelectrolyte layers

The conjugates of magnetic beads coupled with an antibody can be trapped on the Au film firmly due to the magnetic force for the immunoassay of a surface plasmon resonance (SPR) biosensor. However, this approach exhibits significant limitations in robustness and sensitivity due to incomplete dissociation of magnetic beads from the Au film. The incorporation of a polyelectrolyte film on the Au surface can prevent the magnetic beads from the direct contact with the Au film. The layer-by-layer assembly of polyelectrolyte was used as spacer between the gold surface and the magnetic bead. Different layers of polyelectrolyte can be assembled onto the Au film based on an electrostatic force between polycations and polyanions. After the polyelectrolyte film was fabricated on the Au film, the deposition of the magnetic beads was maintained effectively on the film, which favors the sensitivity of the biosensor and the regeneration of the sensing membrane. When the polyelectrolyte layers of (PAH/PSS)₃ were constructed on the Au film, the SPR biosensor with magnetic beads exhibited a satisfactory response to human IgG in the concentration range from 0.25 to 30.00 μg mL⁻¹, and the determination limit obtained is eight times lower than that obtained with (PAH/PSS)₁ layer.