Bioconjugation of a Near-Infrared DNA-Stabilized Silver Nanocluster to Peptides and Human Insulin by Copper-Free Click Chemistry.

DNA-stabilized silver nanoclusters (DNA-AgNCs) are biocompatible emitters with intriguing properties. However, they have not been extensively used for bioimaging applications due to the lack of structural information and hence predictable conjugation strategies. Here, a copper-free click chemistry method for linking a well-characterized DNA-AgNC to molecules of interest is presented. Three different peptides and a small protein, human insulin, were tested as labeling targets. The conjugation to the target compounds was verified by MS, HPLC, and time-resolved anisotropy measurements. Moreover, the spectroscopic properties of DNA-AgNCs were found to be unaffected by the linking reactions. For DNA-AgNC-conjugated human insulin, fluorescence imaging studies were performed on Chinese hamster ovary (CHO) cells overexpressing human insulin receptor B (hIR-B). The specific staining of the CHO cell membranes demonstrates that DNA-AgNCs are great candidates for bioimaging applications, and the proposed linking strategy is easy to implement when the DNA-AgNC structure is known.

Ca2+-Responsive Glyco-insulin.

Chemical modification of peptides and proteins, such as PEGylation and lipidation, creates conjugates with new properties. However, they are typically not dynamic or stimuli-responsive. Self-assembly controlled by a stimulus will allow adjusting properties directly. Here, we report that conjugates of oligogalacturonic acids (OGAs), isolated from plant-derived pectin, are Ca2+-responsive. We report the conjugation of OGA to human insulin (HI) to create new glyco-insulins. In addition, we coupled OGA to model peptides. We studied their self-assembly by dynamic light scattering, small-angle X-ray scattering, and circular dichroism, which showed that the self-assembly to form nanostructures depended on the length of the OGA sequence and Zn2+ and Ca2+ concentrations. Subcutaneous administration of OGA12-HI with Zn2+ showed a stable decrease in blood glucose over a longer period of time compared to HI, despite the lower receptor binding affinity.

Amyloid-ß Inspired Short Peptide Amphiphile Facilitates Synthesis of Silver Nanoparticles as Potential Antibacterial Agents.

An amyloid-ß inspired biocompatible short peptide amphiphile (sPA) molecule was used for controlled and targeted delivery of bioactive silver nanoparticles via transforming sPA nanostructures. Such sPA-AgNPs hybrid structures can be further used to develop antibacterial materials to combat emerging bacterial resistance. Due to the excellent antibacterial activity of silver, the growth of clinically relevant bacteria was inhibited in the presence of AgNPs-sPA hybrids. Bacterial tests demonstrated that the high biocompatibility and low cytotoxicity of the designed sPA allow it to work as a model drug delivery agent. It therefore shows great potential in locally addressing bacterial infections. The results of our study suggest that these nanodevices have the potential to trap and then engage in the facile delivery of their chemical payload at the target site, thereby working as potential delivery materials. This system has potential therapeutic value for the treatment of microbiota triggered progression of neurodegenerative diseases.

High-Performance Reversed-Phase Flash Chromatography Purification of Peptides and Chemically Modified Insulins.

Preparative reversed-phase HPLC is the established method for the purification of peptides, but has significant limitations. We systematically investigated the use of high-performance reversed-phase flash chromatography (HPFC) to rapidly purify laboratory-scale quantities of crude, synthetic peptides and chemically modified insulins. We demonstrated these methods for a diverse set of peptides, including short, medium, and long peptides. Depending on the purity profile of the peptide, HPFC can be used either as the sole purification method, or as a pre-purification method prior to final HPLC purification. Furthermore, HPFC is suitable for the purification of peptides that are not fully in solution. We provide guidelines for the HPFC of synthetic peptides and small proteins, including the choice of columns, eluents, and gradients. We believe that HPFC is a valuable alternative to HPLC purification of peptides and small proteins.

Novel Phenoxazinones as potent agonist of PPAR-α: design, synthesis, molecular docking and in vivo studies.

BACKGROUND: The use of statin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor for the treatment of dyslipidemia has been associated with dose limiting hepatoxicity, mytotoxicity and tolerability due to myalgias thereby necessitating the synthesis of new drug candidates for the treatment of lipid disorder. METHODS: The reaction of appropriate benzenesulphonamide with substituted phenoxazinone in the presence of phenylboronic acid gave the targeted compounds. The molecular docking study were carried out using autodock tool against peroxisome proliferator activated receptor alpha. The in vivo lipid profile were assayed using conventional methods. The kidney and liver function test were carried out to assess the effect of the derivatives on the organs. The LD50 of the most active derivatives were determined using mice. RESULTS: The targeted compounds were successfully synthesized in excellent yields and characterized using spectroscopic techniques. The results of the molecular docking experiment showed that they were good stimulant of peroxisome proliferator activated receptor alpha. Compound 9f showed activity at Ki of 2.8 nM and binding energy of 12.6 kcal/mol. All the compounds tested reduced triglyceride, total cholesterol, low density lipoprotein cholesterol and very low density lipoprotein cholesterol level in the mice model. Some of the reported compounds also increased high density lipoprotein cholesterol level in the mice. The compounds did not have appreciable effect on the kidney and liver of the mice used. The LD50 showed that the novel compounds have improved toxicity profile. CONCLUSION: The synthesis of fifteen new derivatives of carboxamides bearing phenoxazinone and sulphonamide were successful. The compounds possessed comparable activity to gemfibrozil. The reported compounds had better toxicity profile than gemfibrozil and could serve as a replacement for the statins and fibrate class of lipid agents.

Synthesis of proline derived benzenesulfonamides: A potent anti-Trypanosoma brucei gambiense agent.

Thousands of death in Africa and other developing nations are still attributed to trypanosomiasis. Excessive sleep has been associated with increased inflammation. We report herein, the synthesis, antitrypanosomal and anti-inflammatory activities of eight new carboxamide derivatives bearing substituted benzenesulfonamides. The base promoted reactions of l-proline and L-4-hydroxyproline with substituted benzenesulfonyl chlorides gave the benzenesulfonamides (11a-h) in excellent yields. Boric acid mediated amidation of the benzenesulfonamides (11a-h) and p-aminobenzoic acid (12) gave the new carboxamides (13a-h) in excellent yields. The new carboxamides were tested for their antitrypanosomal and anti-inflammatory activities against Trypanosome brucei gambiense and inhibition of carrageenan-induced rat paw edema. Compound 13f was the most potent antitrypanosomal agent with an IC50 value of 2 nM as against 5 nM for melarsoprol; whereas compound 13a was the most potent anti-inflammatory agent with percentage inhibition of carrageenan-induced rat paw edema of 58, 60, 67 and 84% after 0.5 h, 1 h, 2 h and 3 h administration respectively. The structure-activity relationship study revealed that substitution at the para position in the benzenesulfonamide ring increased both the antitrypanosomal and anti-inflammatory activities. The 4-hydroxyprolines (13a-d) showed higher anti-inflammatory activity than the prolines (13e-h). In contrast, the prolines (13e-h) had higher antitrypanosomal activities than the 4-hydroxyprolines. The link between excessive sleep and inflammation makes the report of this class of compounds possessing both antitrypanosomal and anti-inflammatory activity worthwhile. The pharmacokinetic studies showed that the compounds would not pose oral bioavailability, transport and permeability problems.