Biomedical subjects

S Paliwal

Publications and source records attributed to S Paliwal.

4 recordsLinked to original sources

PubMed2005

Induction of cancer-specific cytotoxicity towards human prostate and skin cells using quercetin and ultrasound.

Bioflavonoids, such as quercetin, have recently emerged as a new class of chemotherapeutic drugs for the treatment of various cancer types, but are marred by their low potency and poor selectivity. We report that a short application of low-frequency ultrasound selectively sensitises prostate and skin cancer cells against quercetin. Pretreatment of cells with ultrasound (20 kHz, 2 W cm(-2), 60 s) selectively induced cytotoxicity in skin and prostate cancer cells, while having minimal effect on corresponding normal cell lines. About 90% of the viable skin cancer cell population was lost within 48 h after ultrasound-quercetin (50 microM) treatment. Ultrasound reduced the LC50 of quercetin for skin cancer cells by almost 80-fold, while showing no effect on LC50 for nonmalignant skin cells.

Humans↗

PubMed1996

A novel 70-kDa Triton X-114-soluble antigen of Plasmodium falciparum that contains interspecies-conserved epitopes.

In order to identify novel conserved integral membrane and other membrane-associated proteins of Plasmodium falciparum, lambda gt11-P. falciparum DNA library phages were immunoscreened with convalescent-phase mouse sera and rabbit antiserum against Triton X-114-soluble proteins of P. falciparum. One recombinant phage clone, L857, reacted with both of the antibody probes. Insert DNA (857 bp long) in L857 was 69% dA+dT rich and hybridized to a fragment of 1800 bp from mung bean nuclease-digested P. falciparum genomic DNA. The cloned parasite DNA did not show notable sequence homology with any known protein gene. The L857-encoded polypeptide, p34 (M(r) 34 kDa) was expressed in bacteria, fused to glutathione S-transferase (GST). The fusion peptide, GST-p34 (M(r) 62 kDa), was recognized by immune serum against Triton X-114-soluble antigens of P. falciparum and was reactive with anti-P. falciparum, anti-Plasmodium yoelii, and anti-GST sera. Rabbit antiserum raised against the fusion peptide recognized a 70-kDa protein from lysates of P. falciparum cells and a putative homologous 100-kDa protein from lysates of P. yoelii. The rabbit serum anti-fusion peptide antibodies bound to acetone-fixed P. falciparum-infected erythrocytes and, in immunofluorescent antibody tests, produced a punctate pattern of fluorescence suggesting that the 70-kDa native protein is associated with an apical organelle of the parasite.

Amino Acid Sequence↗

PubMed1993

Disulfide bond assignments and secondary structure analysis of human and murine interleukin 10.

Interleukin 10 (IL-10), which was first discovered by its ability to inhibit the synthesis of various cytokines, most notably gamma interferon, from Th1 helper cells, displays pleiotropic immunoregulatory properties. Human and murine IL-10 have a high amino acid sequence identity (ca. 73%) which includes the conservation of all four cysteine residues in human IL-10 and the first four out of five cysteine residues for murine IL-10. Chemical analysis was used to determine that both recombinant human and recombinant murine IL-10 contain two disulfide bonds. The disulfide pairs for each were determined by mass spectrometric and reversed-phase HPLC analysis of trypsin-derived polypeptide fragments. The disulfide bond assignments for both species were similar in that the first cysteine residue in the sequence paired with the third and the second paired with the fourth. The fifth cysteine in murine IL-10 was determined by chemical modification to be unpaired. Far-UV circular dichroism analysis indicated that the secondary structure of recombinant human and murine IL-10 are composed of ca. 60% alpha-helix. Reduction of the disulfide bonds structurally destabilized the protein and led to a structure containing only 53% alpha-helix. The reduced protein displayed no in vitro biological activity in a mast cell proliferation assay. These studies indicate that IL-10 is a highly alpha-helical protein containing two disulfide bonds, either one or both of which are critical for its structure and function. In addition, these properties suggest that this interesting cytokine may belong to the alpha helical cytokine class of hematopoietic ligands.

Amino Acid Sequence↗

PubMed1989

A simple and sensitive spectrophotometric method for the quantitative determination of solid supported amino groups.

A simple and sensitive method for the quantitative determination of free amino groups on solid support is described. This approach is a modification of Ngo's [(1986) J. Biochem. Biophys. Methods 12, 349-354] method reported earlier. The method is based on the reaction of the solid support with an excess of 5'-O-(4,4'-dimethoxytrityl)-thymidine-3'-O-(2,4-dinitrophenyl) succinate (DTDS) in the presence of a catalytic amount of 4-dimethylaminopyridine. After removing the excess reagent, solid support is treated with perchloric acid to release 4,4'-dimethoxytrityl cation into the solution. The released 4,4'-dimethoxytrityl cation, which has a strong absorption at 498 nm (epsilon 498 = 70,000), is then determined spectrophotometrically. A comparative study of DTDS, N-succinimidyl-3-(2-pyridyldithio)propionate and 4,4-dimethoxytrityl chloride is also included. The method was found to be very useful to determine those amino groups which are available for functionalization of solid supports, especially, monitoring the functionalization of solid supports for affinity chromatography and synthesis of biopolymers.

Amines↗