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At least 487 records · Page 27Linked to original sources
PubMed1998

Fluorescence quenching and time-resolved fluorescence studies on Momordica charantia (bitter gourd) seed lectin.

Chemical modification studies implicated tryptophan (Trp) residues in the sugar binding activity of Momordica charantia lectin (MCL) [Mazumdar, T., Gaur, N. & Surolia, A. (1981) Eur. J. Biochem. 113, 463-470]. In the present study, the accessibility and environment of Trp residues in MCL were investigated by intrinsic fluorescence quenching and time-resolved fluorescence. The emission lamda max of native MCL in the absence as well as in the presence of 0.1 M lactose was around 335 nm, which shifted to 365 nm in the presence of 8 M urea, suggesting that the Trp residues which are predominantly buried in the hydrophobic core of the native lectin get exposed to the aqueous environment upon denaturation. At a quencher concentration of 0.5 M, the extent of quenching observed for the native MCL with acrylamide, I- and Cs+ was 46%, 17% and 12%, respectively. In the presence of 0.1 M lactose this quenching was smaller, suggesting that the sugar ligand provides a partial protection to the Trp residues. In time-resolved fluorescence measurements, the decay curves could be fitted well to a biexponential function with the estimated life times 0.92 ns and 4.64 ns for the native protein and 1.15 ns and 5.1 ns in the presence of 0.1 M lactose. All these results are consistent with the involvement of Trp residues in the sugar-binding activity of MCL.

Acrylamide↗
PubMedDate not supplied

Bitter pill.

Explore the source record for details and available documents.

Attitude↗
PubMed2005

A new bitter diterpenoid from Sarcodon scabrosus.

The new cyathane-type diterpenoid sarcodonin I was isolated from the fruiting bodies of the basidiomycete Sarcodon scabrosus. Its structure was determined on the basis of spectroscopic means, including 2D-NMR (HMBC, HMQC, ROESY, 1H, 1H-COSY).

Diterpenes↗
PubMed1996

Characterization of the enzymatic mechanism of gamma-momorcharin, a novel ribosome-inactivating protein with lower molecular weight of 11,500 purified from the seeds of bitter gourd (Momordica charantia).

The enzymatic mechanism of a small ribosome-inactivating protein, gamma-momorcharin, purified from the seeds of Momordica charantia, has been characterized. By SDS-polyacrylamide and electrospray ionization mass spectrometry, its molecular weight was measured to be 11,500 daltons which is much lower than other RIPs known to date. It can inhibit the protein synthesis in the rabbit reticulocyte cell-free system with ID50 of 55 nM. When rat liver ribosome was incubated with gamma-momorcharin, a diagnostic RNA fragment appeared on the gel after rRNAs were treated with acid aniline. Sequencing of the RNA fragment indicates that the action site of gamma-momorcharin in 28S ribosomal RNA of rat liver is at a specific adenosine (position 4324), which is in a highly conserved loop of 28S rRNA.

Dose-Response Relationship, Drug↗
PubMed1981

Biotransformation of aloenin, a bitter glucoside constituent of Aloe arborescens, by rats.

Aloenin has been established to be 4-methoxy-6-(2-beta-D-glucopyranosyloxy-4-hydroxy-6-methylphenyl)-2-pyrone; it shows an inhibitory activity for gastric juice secretion. Rats metabolized it to 4-methoxy-6-(2,4-dihydroxy-6-methylphenyl)-2-pyrone, 2,5-dimethyl-7-hydroxychromone and glucose, which were excreted in the feces and the urine. The distribution of the radioactivity originating from 14C-labeled aloenin was studied. The tracer found in the kidney and the liver reached 60% of the amount administered 24 h after feeding and decreased rapidly in the next 24 h.

Animals↗