Amine-Reactive BODIPY Dye: Spectral Properties and Application for Protein Labeling

Grafting and controlled release of antimicrobial peptides from mesoporous silica

The grafting of antimicrobial peptides onto mesoporous silica particles and their controlled release using a green light-responsive linker, which enables tunable release-concentration-time profiles, is presented. The mesoporous silica surface is functionalized with antimicrobial peptides employing sequential functionalization steps, including the grafting of 3-[(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) as anchor, boron-dipyrromethene (BODIPY) as photosensitive linker, and C14R peptides as antimicrobial agents. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflectance infrared (ATR-IR) spectroscopy, and thermogravimetric analysis (TGA) validate the successful fabrication and functionalization of mesoporous silica. The ester-1,2,3-triazole-BODIPY demonstrates high sensitivity to green light and enables C14R antimicrobial peptide release with adjusted concentration-time profiles. Under the applied conditions up to 64 μg mL-1 were released within 40 minutes. The antimicrobial activity of the released C14R on Escherichia coli. BL21(DE3) is demonstrated. Overall, the use of the photosensitive linker not only provides a promising avenue for controlling the release of biomolecules and therapeutics but also opens up opportunities for the development of materials for targeted release in wound dressings, for example.

A two-photon fluorescent probe for highly selective detection of Cys over GSH and Hcy based on the Michael addition and transcyclization mechanism and its application in bioimaging and protein straining in SDS-PAGE

BACKGROUND

Cysteine (Cys), glutathione (GSH), and homocysteine (Hcy), as three major biothiols are involved in a variety of physiological processes and play a crucial role in plant growth. Abnormal levels of Cys can cause plants to fail to grow properly. To date, although a very large number of fluorescent probes have been reported for the detection of biothiols, very few of them can be used for the selective discrimination of Cys from GSH and Hcy due to their structural similarity, and only a few of them can be used for plant imaging.

RESULTS

Here, three fluorescent probes (o-/m-/p-TMA) based on TMN fluorophore and the ortho-/meta-/para-substituted maleimide recognition groups were constructed to investigate the selective response effect of Cys. Compared to the o-/m-TMA, p-TMA can selectively detect Cys over GSH and Hcy with a rapid response time (10 min) and a low detection limit (0.26 μM). The theoretical calculation confirmed that the intermediate p-TMA-Cys-int has shorter interatomic reaction distances (3.827 Å) compared to o-/m-TMA-Cys (5.533/5.287 Å), making it more suitable for further transcyclization reactions. Additionally, p-TMA has been employed for selective tracking of exogenous and endogenous Cys in Arabidopsis thaliana using both single-/two-photon fluorescence imaging. Furthermore, single cell walls produced obvious two-photon fluorescence signals, indicating that p-TMA can be used for high-concentration Cys analysis in single cells. Surprisingly, p-TMA can be used as a fluorescent dye for protein staining in SDS-PAGE with higher sensitivity (7.49 μg/mL) than classical Coomassie brilliant blue (14.11 μg/mL).

SIGNIFICANCE

The outstanding properties of p-TMA make it a promising multifunctional molecular tool for the highly selective detection of Cys over GSH and Hcy in various complex environments, including water solutions, zebrafish, and plants. Additionally, it has the potential to be developed as a fluorescent dye for a simple and fast SDS-PAGE fluorescence staining method.

BODIPY(aryl)iodonium salts in the efficient synthesis of diversely functionalized BODIPYs and selective detection of serum albumin

BODIPY(aryl)iodonium salts were readily accessible from the high-yielding reaction of BODIPY with iodoarenes or hydroxyl(tosyloxy)iodoarenes in the presence of m-CPBA. The prepared BODIPY(aryl)iodonium salts bearing substituents of varied electronic nature were utilized for the direct syntheses of thiocyanate, azide, amine and acrylate functionalized BODIPYs and β,β'-bis-BODIPYs. The regioselective syntheses of α-piperidinyl and β-piperidinyl substituted BODIPYs were achieved through the reaction of BODIPY(aryl)iodonium salts with piperidine in the absence and presence of copper(I). Expeditious and high yielding (79-82%) synthesis of β,β'-bis-BODIPYs was also developed through the palladium-catalyzed reductive coupling of the easily accessible BODIPY(aryl)iodonium salts. Some of the indole-appended BODIPYs and bis-BODIPYs displayed strong absorption in the visible region (∼610 nm). The BODIPY(aryl)iodonium salts also showed significant binding with serum albumin and were observed to be selective serum protein sensors with estimated limits of detection as low as 7 μg mL-1 in some cases.

Ultrashort Peptide Grafting on Mesoporous Films and Its Impact on Ionic Mesopore Accessibility

An approach for direct in-pore solid-phase ultrashort peptide synthesis on mesoporous films using the amino acids arginine, leucine, and glycine is presented. Although the number of grafted amino acids remains low, the ionic mesopore accessibility can be gradually adjusted. The addition of arginine in up to five reaction cycles leads to a progressive increase in positive mesopore charge density, which gradually increases the anionic mesopore accessibility at acidic pH. At basic pH, the remaining silanol groups at the pore wall still dominate counter-charged cation mesopore accessibility. Thus, specific peptide sequence design is demonstrated to be a sensitive tool for molecular transport control in nanoscale pores. Overall, the direct in-pore solid-phase ultrashort peptide synthesis on mesoporous films using the sequences of different amino acids opens up exciting opportunities for the development of innovative materials with precisely tailored properties and functions based on specific peptide sequence design.