The semi-synthetic derivatization and biosynthetic studies of lincosamide antibiotics have been reported due to their unique structures and remarkable biological activities. In this review, the structure and biological activity of lincosamides, and enzymatic study of lincosamides biosynthesis will be summarized.

Abstract

Lincosamides are naturally occurring antibiotics isolated from Streptomyces sp. Currently, lincomycin A and its semisynthetic analogue clindamycin are used as clinical drugs. Due to their unique structures and remarkable biological activities, derivatizations of lincosamides via semi-synthesis and biosynthetic studies have been reported. This review summarizes the structures and biological activities of lincosamides, and the recent studies of lincosamide biosynthetic enzymes.

Phosphorescent iridium(III) complexes are widely recognized for their unique properties in the excited triplet state, making them crucial for various applications including biological sensing and imaging. Most of these complexes display single phosphorescence emission from the lowest-lying triplet state after undergoing highly efficient intersystem crossing (ISC) and ultrafast internal conversion (IC) processes. However, in cases where these excited-state processes are restricted, the less common phenomenon of dual emission has been observed. This dual emission phenomenon presents an opportunity for developing biological probes and imaging agents with multiple emission bands of different wavelengths. Compared to intensity-based biosensing, where the existence and concentration of an analyte are indicated by the brightness of the probe, the emission profile response involves modifications in emission color. This enables quantification by utilizing the intensity ratio of different wavelengths, which is self-calibrating and unaffected by the probe concentration and excitation laser power. Moreover, dual-emissive probes have the potential to demonstrate distinct responses to multiple analytes at separate wavelengths, providing orthogonal detection capabilities. In this concept, we focus on iridium(III) complexes displaying fluorescence-phosphorescence or phosphorescence-phosphorescence dual emission, along with their applications as biological probes for sensing and imaging.

This review focuses on discussing natural products (NPs) that contain higher homologs of amino acids (homoAAs) in the structure as well as the proposed and characterized biosynthesis of these non-proteinogenic amino acids. Homologation of amino acids includes the insertion of a methylene group into its side chain. It is not a very common modification found in NP biosynthesis as approximately 450 homoAA-containing NPs have been isolated from four bacterial phyla (Cyanobacteria, Actinomycetota, Myxococcota, and Pseudomonadota), two fungal phyla (Ascomycota and Basidiomycota), and one animal phylum (Porifera), except for a few examples. Amino acids that are found to be homologated and incorporated in the NP structures include the following ten amino acids: alanine, arginine, cysteine, isoleucine, glutamic acid, leucine, phenylalanine, proline, serine, and tyrosine, where isoleucine, leucine, phenylalanine, and tyrosine share the comparable enzymatic pathway. Other amino acids have their individual homologation pathway (arginine, proline, and glutamic acid for bacteria), likely utilize the primary metabolic pathway (alanine and glutamic acid for fungi), or have not been reported (cysteine and serine). Despite its possible high potential in the drug discovery field, the biosynthesis of homologated amino acids has a large room to explore for future combinatorial biosynthesis and metabolic engineering purpose.

The 19-residue silaffin-R5 peptide has been widely studied for its ability to precipitate uniform SiO2 particles through mild temperature and pH pathways, in the absence of any organic solvents. There is consensus that post-translational modification (PTM) of side chains has a large impact on the biomineralization process. Thus, it is imperative to understand the precise mechanisms that dictate the formation of SiO2 from R5 peptide, including the effects of PTM on peptide aggregation and peptide-surface adsorption. In this work, we use molecular dynamics (MD) simulations to study the aggregation of R5 dimer with multiple PTMs, with the presence of different ions in solution. Since this system has strong interactions with deep metastable states, we use parallel bias metadynamics with partitioned families to efficiently sample the different states of the system. We find that peptide aggregation is a prerequisite for biomineralization. We observe that the electrostatic interactions are essential in the R5 dimer aggregation; for wild type R5 that only has positively charged residues, phosphate ions HPO42- in the solution form a bridge between two peptides and are essential for peptide aggregation.

The hydroxy groups of structurally-similar imidazoquinoline payloads are released with different rates from amine-carbamate self-immolative (SI) spacers, depending on the extent of C-α substitution. Unexpectedly, the 2° and 3° alcohol payloads are released with much faster rates than the 1° alcohol, which can be uncaged only by a hyper-reactive SI spacer.

Abstract

Self-immolative (SI) spacers are degradable chemical connectors widely used in prodrugs and drug conjugates to release pharmaceutical ingredients in response to specific stimuli. Amine-carbamate SI spacers are particularly versatile, as they have been used to release different hydroxy cargos, ranging from 2° and 3° alcohols to phenols and oximes. In this work, we describe the ability of three amine-carbamate SI spacers to release three structurally similar imidazoquinoline payloads, bearing either a 1°, a 2° or a 3° alcohol as the leaving group. While the spacers showed comparable efficacy at releasing the 2° and 3° alcohols, the liberation of the 1° alcohol was much slower, unveiling a counterintuitive trend in nucleophilic acyl substitutions. The release of the 1° alcohol payload was only possible using a SI spacer bearing a pyrrolidine ring and a tertiary amine handle, which opens the way to future applications in drug delivery systems.

Peptide nanostructures with tunable structural features, multifunctionality, biocompatibility and biomolecular recognition capacity enable development of targeted drug delivery tools for precision medicine applications. In this review article, we present various techniques employed for the synthesis and self-assembly of peptides into nanostructures, design strategies utilized to enhance their stability, drug-loading capacity, and controlled release, and applications in precision medicine.

Abstract

Peptide and protein nanostructures with tunable structural features, multifunctionality, biocompatibility and biomolecular recognition capacity enable development of efficient targeted drug delivery tools for precision medicine applications. In this review article, we present various techniques employed for the synthesis and self-assembly of peptides and proteins into nanostructures. We discuss design strategies utilized to enhance their stability, drug-loading capacity, and controlled release properties, in addition to the mechanisms by which peptide nanostructures interact with target cells, including receptor-mediated endocytosis and cell-penetrating capabilities. We also explore the potential of peptide and protein nanostructures for precision medicine, focusing on applications in personalized therapies and disease-specific targeting for diagnostics and therapeutics in diseases such as cancer.

Dipeptides of a new structure based on β-triazolalanines and (L)-α-amino acids were synthesized and optimal conditions were developed that ensure both chemical and optical purity of the final products. Molecular docking was carried out and possible intermolecular interactions of dipeptides with potential targets were established. Based on these studies, the analgesic property of chosen dipeptides was studied and it was found that some compounds possess revealed antinociceptive activity in the tail-flick test.

S-Adenosyl-l-methionine (SAM) is an important cosubstrate in various biochemical processes, including selective methyl transfer reactions. Simple methods for the (re)generation of SAM analogs could expand the chemistry accessible with SAM-dependent transferases and go beyond methylation chemistry. Here we present an efficient enzyme engineering strategy to synthesize different SAM analogs from “off-the-shelf” iodoalkanes through enzymatic alkylation of S-adenosyl-l-homocysteine (SAH). This was achieved by mutating multiple hydrophobic and structurally dynamic amino acids simultaneously. Combinatorial mutagenesis was guided by the natural amino acid diversity and generated a highly functional mutant library. This approach increased the speed as well as the scale of enzyme engineering by providing a panel of optimized enzymes with orders of magnitude higher activities for multiple substrates in just one round of enzyme engineering. The optimized enzymes exhibit catalytic efficiencies up to 31 M-1s-1, convert various iodoalkanes, including substrates bearing cyclopropyl or aromatic moieties, and catalyze S-alkylation of SAH with very high stereoselectivities (>99% de). We further report a high throughput chromatographic screening system for reliable and rapid SAM analog analysis. We believe that the methods and enzymes described herein will further advance the field of selective biocatalytic alkylation chemistry by enabling SAM analog regeneration with “off-the-shelf” reagents.

A porphyrin-BODIPY dyad (P-BDP) was obtained through covalent bonding, featuring a two-segment design comprising a light-harvesting antenna system connected to an energy acceptor unit. The absorption spectrum of P-BDP resulted from an overlap of the individual spectra of its constituent parts, with the fluorescence emission of the BODIPY unit experiencing significant quenching (96%) due to the presence of the porphyrin unit. Spectroscopic, computational, and redox investigations revealed a competition between photoinduced energy and electron transfer processes. The dyad demonstrated the capability to sensitize both singlet molecular oxygen and superoxide radical anions. Additionally, P-BDP effectively induced the photooxidation of L-tryptophan. In suspensions of Staphylococcus aureus cells, the dyad led to a reduction of over 3.5 log (99.99%) in cell survival following 30 min of irradiation with green light. Photodynamic inactivation caused by P-BDP was also extended to the individual bacterium level, focusing on bacterial cells adhered to a surface. This dyad successfully achieved the total elimination of the bacteria upon 20 min of irradiation. Therefore, P-BDP presents an interesting photosensitizing structure that takes advantage of the light-harvesting antenna properties of the BODIPY unit combined with porphyrin, offering potential to enhance photoinactivation of bacteria.

A Morita-Baylis-Hillman Adduct derivative bearing a triphenylamine moiety is capable of reacting with human serum albumin shifting its emission from the blue to the green-yellow, leading to green fluorescent albumin (GFA) derivatives, and enlarging the platform of probes for fluorescent-based detection techniques. The results of investigations on the biological properties suggest that GFA retains the ability of binding drug molecules.

Abstract

A Morita-Baylis-Hillman Adduct (MBHA) derivative bearing a triphenylamine moiety was found to react with human serum albumin (HSA) shifting its emission from the blue to the green-yellow thus leading to green fluorescent albumin (GFA) derivatives and enlarging the platform of probes for aggregation-induced fluorescent-based detection techniques. A possible interaction of MBHA derivative 7 with a lipophilic pocket within the HSA structure was suggested by docking studies. DLS experiments showed that the reaction with HSA induce a conformational change of the protein contributing to the aggregation process of GFA derivatives. The results of investigations on the biological properties suggested that GFA retained the ability of binding drug molecules such as warfarin and diazepam. Finally, cytotoxicity evaluation studies suggested that, although the MBHA derivative 7 at 0.1 μg/mL affected the percentage of cell viability in comparison to the negative control, it cannot be considered cytotoxic, whereas at all the other concentrations≥0.5 μg/mL resulted cytotoxic at different extent.