Spacer length effects on in vitro imaging and surface accessibility of fluorescent inhibitors of prostate specific membrane antigen

Prostate-specific membrane antigen (PSMA), a type II transmembrane protein, has been becoming an active target for imaging and therapeutic applications for prostate cancer. Recently, the development of its various chemical inhibitor scaffolds has been explored to serve as carriers for therapeutic or diagnostic payloads targeted to PSMA-positive tumor cells. However, there have been few efforts to definitively determine the optimal length of linker between PSMA inhibitor cores and their payload molecules with regard to the affinity to PSMA and in vitro performance. In our present model study, three spacer-length varied fluorescent inhibitors (FAM-CTT-54, FAM-X-CTT-54 and FAM-PEG(8)-CTT-54) were synthesized, and further enzymatic inhibition studies displayed linker length-dependent changes in: inhibitory potency (IC(50)=0.41 nM, 0.35 nM, 1.93 nM), modes of binding (reversible, slowly reversible, irreversible), respectively. Furthermore, cell-labeling imaging revealed the spacer length-related change of fluorescence intensity (FAM-X-CTT-54>FAM-PEG(8)-CTT-54>FAM-CTT-54). These results suggest that selection of linkers and their lengths will be important considerations in the development of next-generation prostate tumor-targeted imaging probes and therapeutic agents that specifically home to PSMA on tumor cells.     

Differential adhesive properties of the surface of human blood flukesSchistosoma mansoni

While infecting a vertebrate host, blood flukes (Schistosoma mansoni) must continually resist adhesions by immune effector cells. However, the male and female schistosomes must adhere to one another in order to establish and maintain the sexual pairing process after 4 wk postinfection. Using a contact angle method, the relative adhesiveness of male and female parasites were determined. Results indicate that schistosomes restrict effector cell adhesion through developmental, sexual, and regional differences in adhesive properties.     

Involvement of IL-17A in the pathogenesis of DSS-induced colitis in mice

To investigate the etiological implication of IL-17A in inflammatory bowel disease (IBD), dextran sodium sulfate (DSS) was administered to the mice deficient for the IL-17A gene. They showed only faint manifestations of colitis, as revealed by body weight loss, shrinkage in the colon length, serum haptoglobin concentration, and disease activity index. Although the mortality rate of WT mice reached approximately 60%, more than 90% of the IL-17A KO mice survived the DSS treatment. Histological change was also marginal in the IL-17A KO intestine, in which epithelial damage and inflammatory infiltrates were not obvious and the myeloperoxidase activity elevated only slightly. G-CSF and MCP-1 were abundantly produced in WT mouse intestine, whereas the production of these chemokines was drastically hampered in IL-17A-null intestine. The present results show that IL-17A plays a pivotal role in the pathogenesis of DSS-induced colitis, while MCP-1 and G-CSF may be crucially involved in the IL-17A-induced inflammation.     

Dissecting CNBP, a zinc-finger protein required for neural crest development, in its structural and functional domains

Cellular nucleic-acid-binding protein (CNBP) plays an essential role in forebrain and craniofacial development by controlling cell proliferation and survival to mediate neural crest expansion. CNBP binds to single-stranded nucleic acids and displays nucleic acid chaperone activity in vitro. The CNBP family shows a conserved modular organization of seven Zn knuckles and an arginine-glycine-glycine (RGG) box between the first and second Zn knuckles. The participation of these structural motifs in CNBP biochemical activities has still not been addressed. Here, we describe the generation of CNBP mutants that dissect the protein into regions with structurally and functionally distinct properties. Mutagenesis approaches were followed to generate: (i) an amino acid replacement that disrupted the fifth Zn knuckle; (ii) N-terminal deletions that removed the first Zn knuckle and the RGG box, or the RGG box alone; and (iii) a C-terminal deletion that eliminated the three last Zn knuckles. Mutant proteins were overexpressed in Escherichia coli, purified, and used to analyze their biochemical features in vitro, or overexpressed in Xenopus laevis embryos to study their function in vivo during neural crest cell development. We found that the Zn knuckles are required, but not individually essential, for CNBP biochemical activities, whereas the RGG box is essential for RNA-protein binding and nucleic acid chaperone activity. Removal of the RGG box allowed CNBP to preserve a weak single-stranded-DNA-binding capability. A mutant mimicking the natural N-terminal proteolytic CNBP form behaved as the RGG-deleted mutant. By gain-of-function and loss-of-function experiments in Xenopus embryos, we confirmed the participation of CNBP in neural crest development, and we demonstrated that the CNBP mutants lacking the N-terminal region or the RGG box alone may act as dominant negatives in vivo. Based on these data, we speculate about the existence of a specific proteolytic mechanism for the regulation of CNBP biochemical activities during neural crest development.     

Fluorescent-fipronil: Design and synthesis of a stable conjugate

Fipronil is a phenyl pyrazole molecule widely used across the world as both insecticide and veterinary drug. The main goal of this work was to synthesize a fluorescently labeled fipronil derivative for cellular imaging without affecting its intrinsic properties. We selected fluorescein as fluorescent probe and we investigated different strategies for stable chemical ligation between both entities, such as thiourea and direct peptide bond. While thiourea bond displayed low stability, direct peptide bond was difficult to achieve due to problems of steric hindrance. The best result was obtained by conjugation using click chemistry, which allowed to obtain fipronil stably labeled with the fluorescent probe.     

Mechanisms involved in the biosynthesis of polysaccharides

The mechanisms for the biosynthesis of three polysaccharides are presented: (i) starch synthesized by starch synthase and adenosine diphospho glucose; (ii) dextran synthesized by Leuconostoc mesenteroides B-512FMC dextransucrase and sucrose; and (iii) Acetobacter xylinum cellulose synthesized by cellulose synthase, uridine diphospho glucose, and bactoprenol phosphate. All three enzymes were pulsed with substrates, containing ¹⁴C-glucose and chased with the same nonlabeled substrates. When the polysaccharides were isolated, reduced, and hydrolyzed, the pulsed reactions gave ¹⁴C-glucitol, which was significantly decreased in the chase reaction. These experiments definitively show that all three polysaccharides are biosynthesized by the addition of glucose to the reducing-ends of the growing polysaccharides and not by the addition to the nonreducing-ends of primers. Additional evidence indicates that glucose and the polysaccharides are covalently attached to the active-sites of the enzymes. A two catalytic-site insertion mechanism at one active-site is proposed for the biosyntheses. Two of the polysaccharides are α-linked glucans, starch and dextran, and cellulose is a β-linked glucan, known for several years to require a bactoprenol lipid phosphate intermediate. It is shown how this intermediate is involved in determining that β-linkages are synthesized. Other β-linked polysaccharides: bacterial cell wall peptidomurein, Salmonella O-antigen polysaccharide, and Xanthanomonas camprestris xanthan, are heteropolysaccharides, with the later two also being hetero-linked polysaccharides, with the β-linkage at the reducing-end of the repeating unit. All three require bactoprenol lipid phosphate intermediates and are biosynthesized by the addition of the repeating units to the reducing-end of a growing polysaccharide chain, with the formation of a β-linkage.     

A novel aldehyde dextran sulfonate matrix for affinity biosensors

Aldehyde dextran sulfonate (ADS), a modified oligosaccharide polymer, was used to prepare a new matrix structure for affinity biosensors. The principal difference between the ADS matrix and similar structures developed previously results from presence of two active functional groups in the matrix, namely, aldehyde and sulfonate. These groups perform two different functions in the matrix. The aldehyde group is responsible for covalent bonding in the biomaterials, and the negatively charged sulfonate group provides electrostatic attraction of the positively charged biomolecules. By varying the ratio between the aldehyde and sulfonate groups in the matrix, one can control contributions from the two binding modes (covalent and electrostatic). A number of oligosaccharides, such as simple dextran, aldehyde dextran (AD), aldehyde dextran sulfonate (ADS) and aldehyde ethylcellulose (AEC), were used for preparation of matrix structures. The properties of the obtained matrices were analysed and compared. Surface plasmon resonance (SPR) was used as the main technique to characterize the matrix structures.     

Studies on the synthesis and the antimicrobial and antioxidant activities of a novel class of fluorescein-based glycosides

Facile glycosylation of a fluorescein diol derivative with per-O-acetyl/benzoyl sugar derivatives using BF₃·Et₂O catalyst resulted in the formation of the expected glycosides in 54–66% yield. The biological screening of the glycosides against different microbes shows good inhibitory activity. The antioxidant activity of the fluorescein-based glycosides shows remarkable inhibition (IC₅₀ ∼80%).     

Diffusion barriers of tripartite sporopollenin microcapsules prepared from pine pollen

Tripartite sporopollenin microcapsules prepared from pine pollen (Pinus sylvestris L. and Pinus nigra Arnold) were analysed with respect to the permeability of the different strata of the exine which surround the gametophyte and form the sacci. The sexine at the surface of the sacci is highly permeable for polymer molecules and latex particles with a diameter of up to 200 nm, whereas the nexine covering the gametophyte is impermeable for dextran molecules, with a Stokes' radius > or =4 nm (Dextran T 70), and for the tetravalent anionic dye Evans Blue (Stokes' radius = 1.3 nm). The central capsules obtained by dissolution of the sporoplasts showed strictly membrane-controlled exchange of non-electrolytes, with half-equilibration times in the range of minutes (monosaccharides, oligosaccharides) to hours (dextran molecules with Stokes' radii up to 2.5 nm). The dependence of the permeability coefficients of the nexine for non-electrolytes on Stokes' radius or molecular weight shows that the aqueous pores through the nexine are inhomogeneous with respect to their size, and that most pores are too narrow for free diffusion of sugar molecules. To explain the barrier function of the nexine for Evans Blue, it is assumed that at least the larger pores, which enable slow permeation of dextran molecules, contain negative charges.