Jung Sook Kang

A new antibacterial dioxopiperazine alkaloid related to gliotoxin from a marine isolate of the fungus Pseudallescheria

A new antibacterial dioxopiperazine, dehydroxybisdethiobis(methylthio)gliotoxin (1), and the previously described bisdethiobis(methylthio)gliotoxin (2) and gliotoxin (3), have been isolated from the broth of a marine-derived fungus of the genus Pseudallescheria. The structure and absolute stereochemistry of the new compound was assigned on the basis of NMR and CD experiments. Compounds 1~3 exhibit potent antibacterial activity against the methicillin-resistant and multidrug-resistant Staphylococcus aureus with MIC values of 31.2, 31.2, and 1.0 µg/ml, respectively. Compound 3 also exhibited a significant radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC50 value of 5.2 µM.

Chlorohydroaspyrones A and B, antibacterial aspyrone derivatives from the marine-derived fungus Exophiala sp.

Chlorohydroaspyrones A (1) and B (2), antibacterial aspyrone derivatives, and the previously described aspyrone (3), asperlactone (4), and penicillic acid (5) have been isolated from the broth of a marine isolate of the fungus Exophiala. The structure and absolute stereochemistry of the compounds were determined on the basis of the physicochemical data analysis and chemical reactions. Compounds 1 and 2 exhibited a mild antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus, and multidrug-resistant S. aureus. The MIC values of each strain are as follows: compound 1 showed 62.5 microg/mL for S. aureus and 125 microg/mL for methicillin-resistant S. aureus and multidrug-resistant S. aureus, and compound 2, 62.5 microg/mL for S. aureus and methicillin-resistant S. aureus and 125 microg/mL for multidrug-resistant S. aureus.

Circumdatin I, a New Ultraviolet-A Protecting Benzodiazepine Alkaloid from a Marine Isolate of the Fungus Exophiala

AbstractA new ultraviolet-A (UV-A) protecting benzodiazepine alkaloid, circumdatin I (1), along with the previously described circumdatin C (2) and circumdatin G (3), have been isolated from the mycelium of a marine-derived fungus of the genus Exophiala. The structures of the three circumdatins were assigned on the basis of physicochemical evidence. The absolute stereochemistry of 1 was determined by comparison of optical rotation and CD experiments with those of 2 and 3.

Enhanced Emission Induced by FRET from a Long- Lifetime, Low Quantum Yield Donor to a Long- Wavelength, High Quantum Yield Acceptor

We report observation of high quantum yield, long-lifetime fluorescence from a red dye BO-PRO-3 excited by resonance energy transfer (RET). The acceptor fluorescence was highly enhanced upon binding to the donor-labeled DNA. A ruthenium complex (Ru) was chosen as a donor in this system because of its long fluorescence lifetime. Both donor and acceptor were non-covalently bound to DNA. Emission from the donor-acceptor system (DA) at wavelengths exceeding 600 nm still preserves the long-lifetime component of the Ru donor, retaining average fluorescence lifetimes in the range of 30–50 ns. Despite the low quantum yield of the Ru donor in the absence of acceptor, its overall quantum yield of the DA pair was increased by energy transfer to the higher quantum yield acceptor BO-PRO-3. The wavelength-integrated intensity of donor and acceptor bound to DNA was many-fold greater than the intensity of the donor and acceptor separately bound to DNA. The origin of this effect is due to an efficient energy transfer from the donor, competing with non-radiative depopulation of the donor excited state. The distinctive features of DA complexes can be used in the development of a new class of engineered luminophores that display both long lifetime and long-wavelength emission. Similar DA complexes can be applied as proximity indicators, exhibiting strong fluorescence of adjacently located donors and acceptors over the relatively weak fluorescence of separated donors and acceptors.

A Radical Scavenging Farnesylhydroquinone from a Marine-Derived Fungus Penicillium sp.

Farnesylhydroquinone (1) has been isolated from the mycelium of a marine-derived fungus of the genusPenicillium. The structure of the compound (1) has been elucidated by spectral method. The compound1 exhibits potent radical scavenging activity (IC5012.5 μM) against the DPPH.

Induced production of bromomethylchlamydosporols A and B from the marine-derived fungus Fusarium tricinctum.

The addition of CaBr(2) to the fermentation of a marine-derived Fusarium tricinctum resulted in production of halogenated chlamydosporol analogues. Two new antimicrobial halogenated pyranopyranones, bromomethylchlamydosporols A (1) and B (2), and two known compounds, chlamydosporol (an inseparable epimeric mixture of 7R:7S = 1:1 from (1)H NMR data) (3) and fusarielin A (4), were isolated from the culture. The structures of 1 and 2 were assigned through a combination of spectroscopic data analyses. Compounds 1-4 exhibited mild antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus, and multidrug-resistant S. aureus. The MIC values of each strain were as follows: compounds 1 and 2 showed an MIC of 15.6 μg/mL against S. aureus, methicillin-resistant S. aureus, and multidrug-resistant S. aureus, and compounds 3 and 4 exhibited an MIC of 31.5 μg/mL against S. aureus and methicillin-resistant S. aureus and 62.5 μg/mL against multidrug-resistant S. aureus.

The effect of ethanol on lateral and rotational mobility of plasma membrane vesicles isolated from cultured mar 18.5 hybridoma cells

Intramolecular excimer formation of 1,3-di(1-pyrenyl)propane (Py-3-Py) and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) were used to evaluate the effect of ethanol on the rate and range of the lateral mobility and the range of the rotational mobility of bulk bilayer structures of the plasma membrane vesicles (ATCC-PMV) isolated from cultured hybridoma cells (ATCC TIB 216). In a concentration-dependent manner, ethanol increased the excimer to monomer fluorescence intensity ratio (I′/I) of Py-3-Py in the ATCC-PMV and decreased the anisotropy (r), limiting anisotropy (r∞) and order parameter (S) of DPH in the ATCC-PMV. This indicates that ethanol increased both the lateral and rotational mobility of the probes in the ATCC-PMV. Selective quenching of DPH by trinitrophenyl groups was utilized to examine the range of transbilayer asymmetric rotational diffusion of the ATCC-PMV. The anisotropy (r), limiting anisotropy (r∞) and order parameter (S) of DPH in the inner monolayer were 0.024, 0.032, and 0.069, respectively, greater than calculated for the outer monolayer of the ATCC-PMV. Selective quenching of DPH by trinitrophenyl groups was also used to examine the transbilayer asymmetric effects of ethanol on the range of the rotational mobility of the ATCC-PMV. Ethanol had a greater increasing effect on the range of the rotational mobility of the outer monolayer as compared to the inner monolayer of the ATCC-PMV. It has been proven that ethanol exhibits a selective rather than nonselective fluidizing effect within the transbilayer domains of the ATCC-PMV.

Induced Production of Halogenated Diphenyl Ethers from the Marine-Derived Fungus Penicillium chrysogenum

Manipulation of the fermentation of the marine‐derived fungus Penicillium chrysogenum by addition of CaBr2 resulted in induced production of bromodiphenyl ether analogs. Two new free‐radical‐scavenging polybrominated diphenyl ethers, 1 and 2, and three known diphenyl ethers, 3,3′‐dihydroxy‐5,5′‐dimethyldiphenyl ether (3), and an inseparable mixture of violacerol‐I (4) and violacerol‐II (5) were isolated. The structures of the two new polybromodiphenyl ethers 1 and 2 were assigned by combined spectroscopic‐data analysis, including deuterium‐induced isotope effect. Compounds 1–3, and a mixture of 4 and 5 exhibited radical‐scavenging activities against 1,1‐diphenyl‐2‐picrylhydrazyl with IC50 values of 18, 15, 42, and 6u2005μM, respectively. With the exception of 3, the compounds were, therefore, more active than the positive control, ascorbic acid (IC50 20u2005μM).

New production of haloquinones, bromochlorogentisylquinones A and B, by a halide salt from a marine isolate of the fungus Phoma herbarum

New production of haloquinones, bromochlorogentisylquinones A and B, by a halide salt from a marine isolate of the fungus Phoma herbarum

DNA dynamics: a fluorescence resonance energy transfer study using a long-lifetime metal-ligand complex.

Fluorescent probes bound to DNA typically display nanosecond decay times and reveal only nanosecond motions. We extend the time range of measurable DNA dynamics using [Ru(bpy)2(dppz)]2+ (bpy=2,2’-bipyridine, dppz=dipyrido[3,2-a:2’,3’-c]phenazine) (RuBD) which displays a mean lifetime near 90 ns. To test the usefulness of RuBD as a probe for diffusive processes in calf thymus DNA, we compared the efficiencies of fluorescence resonance energy transfer (FRET) using three donors which display lifetimes near 5 ns for acridine orange (AO), 22 ns for ethidium bromide (EB) and 92 ns for RuBD, with nile blue (NB) as the acceptor. The Förster distances for AO-NB, EB-NB and RuBD-NB donor-acceptor pairs were 42.3, 52.3, and 30.6 A, respectively. All three donors showed dramatic decreases in fluorescence intensities and more rapid intensity decays with increasing NB concentrations. The intensity decays of AO and EB in the presence of varying concentrations of NB were satisfactorily described by the one-dimensional FRET model without diffusion (Blumen and Manz, 1979). In the case of the long-lifetime donor RuBD, the experimental phase and modulation somewhat deviated from the recovered values computed from this model. The recovered NB concentrations and FRET efficiencies from the model were slightly larger than the expected values, however, the recovered and expected values did not show a significant difference. Thus, it is suggested that the lifetime of RuBD is too short to measure diffusive processes in calf thymus DNA.