Antiproliferative effect of T/Tn specific Artocarpus lakoocha agglutinin (ALA) on human leukemic cells (Jurkat, U937, K562) and their imaging by QD-ALA nanoconjugate

T/Tn specificity of Artocarpus lakoocha agglutinin (ALA), isolated from the seeds of A. lakoocha (Moraceae) fruit and a heterodimer (16 kD and 12 kD) of molecular mass 28 kD, was further confirmed by SPR analysis using T/Tn glycan containing mammalian glycoproteins. N-terminal amino acid sequence analysis of ALA showed homology at 15, 19-21, 24-27, and 29 residues with other lectin members of Moraceae family viz., Artocarpus integrifolia (jacalin) lectin, Artocarpus hirsuta lectin, and Maclura pomifera agglutinin. It is mitogenic to human PBMC and the maximum proliferation was observed at 1 ng/ml. It showed an antiproliferative effect on leukemic cells, with the highest effect toward Jurkat cells (IC50 13.15 ng/ml). Synthesized CdS quantum dot-ALA nanoconjugate was employed to detect the expression of T/Tn glycans on Jurkat, U937, and K562 leukemic cells surfaces as well as normal lymphocytes by fluorescence microscopy. No green fluorescence was observed with normal lymphocytes indicating that T/Tn determinants, which are recognized as human tumor associated structures were cryptic on normal lymphocyte surfaces, whereas intense green fluorescent dots appeared during imaging of leukemic cells, where such determinants were present in unmasked form. The above results indicated that QD-ALA nanoconjugate is an efficient fluorescent marker for identification of leukemic cell lines that gives rise to high quality images

Mechanistic Investigation of the Inhibition of Aβ42 Assembly and Neurotoxicity by Aβ42 C-terminal Fragments

Oligomeric forms of amyloid β-protein (Aβ) are key neurotoxins in Alzheimer’s disease (AD). Previously, we found that C-terminal fragments (CTFs) of Aβ42 interfered with assembly of full-length Aβ42 and inhibited Aβ42-induced toxicity. To decipher the mechanism(s) by which CTFs affect Aβ42 assembly and neurotoxicity, here, we investigated the interaction between Aβ42 and CTFs using photoinduced cross-linking and dynamic light scattering. The results demonstrate that distinct parameters control CTF inhibition of Aβ42 assembly and Aβ42-induced toxicity. Inhibition of Aβ42-induced toxicity was found to correlate with stabilization of oligomers with a hydrodynamic radius (R[subscript H]) of 8−12 nm and attenuation of formation of oligomers with an R[subscript H] of 20−60 nm. In contrast, inhibition of Aβ42 paranucleus formation correlated with CTF solubility and the degree to which CTFs formed amyloid fibrils themselves but did not correlate with inhibition of Aβ42-induced toxicity. Our findings provide important insight into the mechanisms by which different CTFs inhibit the toxic effect of Aβ42 and suggest that stabilization of nontoxic Aβ42 oligomers is a promising strategy for designing inhibitors of Aβ42 neurotoxicity.National Institute on Aging (Grant AG027818

Nature Chem

Numerous essential biomolecular processes require the recognition of DNA surface features by proteins. Molecules mimicking these features could potentially act as decoys and interfere with pharmacologically or therapeutically relevant protein-DNA interactions. Although naturally occurring DNA-mimicking proteins have been described, synthetic tunable molecules that mimic the charge surface of double-stranded DNA are not known. Here, we report the design, synthesis and structural characterization of aromatic oligoamides that fold into single helical conformations and display a double helical array of negatively charged residues in positions that match the phosphate moieties in B-DNA. These molecules were able to inhibit several enzymes possessing non-sequence-selective DNA-binding properties, including topoisomerase 1 and HIV-1 integrase, presumably through specific foldamer-protein interactions, whereas sequence-selective enzymes were not inhibited. Such modular and synthetically accessible DNA mimics provide a versatile platform to design novel inhibitors of protein-DNA interactions

Amyloid beta Protein and Alzheimer's Disease: When Computer Simulations Complement Experimental Studies

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