Department of Chemistry
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Item Synthesis and evaluation of tripodal peptide analogues for cellular delivery of phosphopeptides(ACS, 2007-06-20) Kumar, AnilTripodal peptide analogues were designed on the basis of the phosphotyrosine binding pocket of the Src SH2 domain and assayed for their ability to bind to fluorescein-labeled phosphopeptides. Fluorescence polarization assays showed that a number of amphipathic linear peptide analogues (LPAs), such as LPA4, bind to fluorescein-labeled GpYEEI (F-GpYEEI). LPA4 was evaluated for potential application in cellular delivery of phosphopeptides. Fluorescence microimaging cellular uptake studies with fluorescein-attached LPA4 (F-LPA4) alone or with the mixture of LPA4 and F-GpYEEI in BT-20 cells showed dramatic increase of the fluorescence intensity in cytosol of cells, indicating that LPA4 can function as a delivery tool of F-GpYEEI across the cell membrane. Fluorescent flow cytometry studies showed the cellular uptake of F-LPA4 in an energy-independent pathway and confirmed the cellular uptake of F-GpYEEI in the presence of LPA4. These studies suggest that amphipathic tripodal peptide analogues, such as LPA4, can be used for cellular delivery of phosphopeptidesItem Cerium Triflate: An Efficient and Recyclable Catalyst for Chemoselective Thioacetalization of Carbonyl Compounds under Solvent-Free Conditions(CSIRO, 2009-08-26) Kumar, AnilA simple and efficient chemoselective thioacetalization of carbonyl compounds has been achieved using Ce(OTf)3 (10 mol-%) as a catalyst under solvent-free conditions. Advantages of the methodology include very short reaction times, excellent yields, the catalytic use of a water tolerant Lewis acid, and simple recovery and reuse of the catalyst.Item Fluorescence spectroscopic studies on substituted porphyrins in homogeneous solvents and cationic micellar medium(Elsiever, 2013-02) Kumar, Anil; Kumar, DalipSteady state and time-resolved fluorescence properties of porphyrin appended 1,3,4-oxadiazoles and thiazoles were described in homogeneous medium as well as in presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The electron withdrawing substituent on the porphyrin moiety in both the cases make a donor–spacer–acceptor type of intramolecular photoinduced electron transfer (PET) system resulting substantial quenching in porphyrin fluorescence due to partial energy migration towards the acceptor in the excited state. The increase in fluorescence yield as well as appreciable difference in fluorescence decay behavior in aqueous buffer solution of pH 4.2 from that in chloroform solution is believed due to partial protonation of the porphyrin ring. All the investigated systems show preferential binding into the interfacial region of the micellar sub-domain with varying degree of penetration depending on the nature of the substituent. Almost 2–4 fold increase in fluorescence yield for the probes is explained on the basis of restricted flexibility and corresponding decrease in total nonradiative rate inside the micellar interface layer.Item Cyclic Peptide–Selenium Nanoparticles as Drug Transporters(RSC, 2014) Kumar, AnilA cyclic peptide composed of five tryptophan, four arginine, and one cysteine [W5R4C] was synthesized. The peptide was evaluated for generating cyclic peptide-capped selenium nanoparticles (CP–SeNPs) in situ. A physical mixing of the cyclic peptide with SeO3–2 solution in water generated [W5R4C]–SeNPs via the combination of reducing and capping properties of amino acids in the peptide structure. Transmission electron microscopy (TEM) images showed that [W5R4C]–SeNPs were in the size range of 110–150 nm. Flow cytometry data revealed that a fluorescence-labeled phosphopeptide (F′-PEpYLGLD, where F′ = fluorescein) and an anticancer drug (F′-dasatinib) exhibited approximately 25- and 9-times higher cellular uptake in the presence of [W5R4C]–SeNPs than those of F′-PEpYLGLD and dasatinib alone in human leukemia (CCRF-CEM) cells after 2 h of incubation, respectively. Confocal microscopy also exhibited higher cellular delivery of F′-PEpYLGLD and F′-dasatinib in the presence of [W5R4C]–SeNPs compared to the parent fluorescence-labeled drug alone in human ovarian adenocarcinoma (SK-OV-3) cells after 2 h of incubation at 37 °C. The antiproliferative activities of several anticancer drugs doxorubicin, gemcitabine, clofarabine, etoposide, camptothecin, irinotecan, epirubicin, fludarabine, dasatinib, and paclitaxel were improved in the presence of [W5R4C]–SeNPs (50 μM) by 38%, 49%, 36%, 36%, 31%, 30%, 30%, 28%, 24%, and 17%, respectively, after 48 h incubation in SK-OV-3 cells. The results indicate that CP–SeNPs can be potentially used as nanosized delivery tools for negatively charged biomolecules and anticancer drugs.