In situ Interlamellar Production of Amide Based Functional Copolymer/Clay Nanocomposites

Functional amide based copolymer/clay nanocomposites were synthesized by in situ radical-initiated interlamellar copolymerization from acrylamide and citraconic anhydride monomers in the presence of organically modified montmorillonite (O-MMT) clay. To investigate...

A Fluorogenic Assay: Analysis of Chemical Modification of Lysine and Arginine to Control Proteolytic Activity of Trypsin

The chemical modification of amino acids plays an important role in the modulation of proteins or peptides and has useful applications in the activation and stabilization of enzymes, chemical biology, shotgun proteomics, and the production of peptide-based drugs. Although chemoselective modification of amino acids such as lysine and arginine via the insertion of respective chemical moieties as citraconic anhydride and phenyl glyoxal is important for achieving desired application objectives and has been extensively reported, the extent and chemoselectivity of the chemical modification of specific amino acids using specific chemical agents (blocking or modifying agents) has yet to be sufficiently clarified owing to a lack of suitable assay methodologies. In this study, we examined the utility of a fluorogenic assay method, based on a fluorogenic tripeptide substrate (FP-AA1-AA2-AA3) and the proteolytic enzyme trypsin, in determinations of the extent and chemoselectivity of the chemical modification of lysine or arginine. As substrates, we used two fluorogenic tripeptide probes, MeRho-Lys-Gly-Leu(Ac) (lysine-specific substrate) and MeRho-Arg-Gly-Leu(Ac) (arginine-specific substrate), which were designed, synthesized, and evaluated for chemoselective modification of specific amino acids (lysine and arginine) using the fluorogenic assay. The results are summarized in terms of half-maximal inhibitory concentrations (IC50) for the extent of modification and ratios of IC50 values (IC50arginine/IC50lysine and IC50lysine/IC50arginine) as a measure of the chemoselectivity of chemical modification for amino acids lysine and arginine. This novel fluorogenic assay was found to be rapid, precise, and reproducible for determinations of the extent and chemoselectivity of chemical modification.

Synthesis of Six and Seven-membered Heterocyclic Molecules Containing an Adamantyl Fragment and an X-ray Crystal Structure of (E)-N-(adamantan-1-yl)-1-(3-nitrophenyl)methanimine

Our work included a synthesis of three new imine derivatives—1,3-thiazinan-4-one, 1,3-oxazinan-6-one and 1,3-oxazepin-4,7-dione—which contained an adamantyl fragment. These were produced via the condensation of the Schiff`s base (E)-N-(adamantan-1-yl)-1-(3-aryl)methanimine with 3-mercaptopropanoic acid; 3-chloropropanoic acid; and maleic, citraconic anhydride, respectively. These new imines were prepared via the condensation of adamantan-1-ylamine and 3-nitro-, 3-bromobenzaldehyde in n-BuOH. We obtained a good yield of products. FTIR, 1H NMR spectroscopy and C.H.N.S analysis were used to diagnostic the products. The molecular structure of (E)-N-(adamantan-1-yl)-1-(3-nitrophenyl)methanimine was confirmed by X-ray crystallography analysis.

New adducts of turpentine and rosin with citraconic anhydride and itaconic acid

The reaction of pine gum rosin, turpentine and its components (α-pinene, ∆3-carene, α-terpinene) with citraconic anhydride and itaconic acid was investigated. It was shown that α-terpinene, in contrast to α-pinene and ∆3-carene, reacts with citraconic anhydride to give the unknown cycloaddition reaction product. Its structure was studied by the 2D NMR spectroscopy. Turpentine reacts with itaconic acid forming a complex mixture that contains esters of terpenic alcohols and itaconic acid. Reaction of rosin with citraconic anhydride was studied at 140–180 °С within 0.5–8 hrs in presence of catalytic amounts of H2SO4, MgCl2, AlCl3, FeCl3and new citraconopimaric adducts containing up to ~70 % of citraconopimaric acid as a mixture of two С15–CH3and С16–CH3isomers in equimolar ratio. The highest content of С15–CH3isomer of citraconopimaric acid (35.5–36.0 %) in the adducts was reached within 4–8 hrs at 180 °С in presence of 1–2 mass. % H2SO4. The reaction of rosin with citraconic anhydride at 140–160 °С leads to the formation of adduct containing up to 30–50 % of citraconopimaric acid isomers. The synthesized adducts may be used for production of composite materials for different applications (adhesives, polymer composite additives including rubber blends for tire production, components of grease-cooling liquids).

A new route to tricyclane sesquiterpenoids: total synthesis of α-ekasantalic acid

Chemical manipulation of the cycloadduct of citraconic anhydride and cyclopentadiene enables a new synthetic route to tricyclane sesquiterpenoids.

pH-Responsive 2-hydroxyethyl methacrylate/citraconic anhydride–modified collagen hydrogels as ciprofloxacin carriers for wound dressings

pH-Sensitive hydrogels of 2-hydroxyethyl methacrylate/citraconic anhydride–modified collagen were obtained by free radical copolymerization/crosslinking in the presence of ammonium persulfate/ N,N,N′, N′-tetramethylethylenediamine redox initiator system. Their pH-responsiveness was demonstrated by swelling behavior and ciprofloxacin release tests. Both unloaded and loaded hydrogels were characterized by Fourier transform infrared, scanning electron microscopy, and biocompatibility tests. The enzymatic degradation in the presence of Clostridium histolyticum mainly depends on initiator content. In vivo biocompatibility tests involving intraperitoneal hydrogels’ implantation in rats following the analysis by the granuloma test, leukocyte formula, immune parameters, and hepatic transaminases demonstrated their non-toxicity and biocompatibility with living tissues. The in vitro antimicrobial activity, in vivo biocompatibility, and in vitro biodegradability tests attest the possibility to use these new polymeric hydrogels with tailored properties as matrices for bioactive products in medical and pharmaceutical applications as wound care and targeting drug delivery systems. The ciprofloxacin release studies proved their potential as materials for wound dressings.