Daunomycin binding to detergent micelles: A model system for evaluating the hydrophobic contribution to drug-DNA interactions

The interaction of daunomycin with sodium dodecyl sulfate and Triton X-100 micelles was investigated as a model for the hydrophobic contribution to the free energy of DNA intercalation reactions. Measurements of visible absorbance, fluorescence lifetime, steady-state fluorescence emission intensity, and fluorescence anisotropy indicate that the anthraquinone ring partitions into the hydrophobic micelle interior. Fluorescence quenching experiments using both steady-state and lifetime measurements demonstrate reduced accessibility of daunomycin in sodium dodecyl sulfate micelles to the anionic quencher iodide and to the neutral quencher acrylamide. Quenching of daunomycin fluorescence by iodide in Triton X-100 micelles was similar to that seen with free daunomycin. Studies of the energetics of the interaction of daunomycin with micelles by fluorescence and absorbance titration methods and by isothermal titration calorimetry in the presence of excess micelles revealed that association with sodium dodecyl sulfate and Triton X-100 micelles is driven by a large negative enthalpy. Association of the drug with both types of micelles also has a favorable entropic contribution, which is larger in magnitude for Triton X-100 micelles than for sodium dodecyl sulfate micelles.

Drug-human serum albumin binding studied by capillary electrophoresis with electrochemiluminescence detection

A new technique for investigating drug-protein binding was developed employing capillary electrophoresis (CE) coupled with tris(2,2'-bipyridyl) ruthenium(II) [Ru(bPY)(3)(2+)] electrochemiluminescence (ECL) (CE-ECL) detection after equilibrium dialysis. Three basic drugs, namely pridinol, procyclidine and its analogue trihexyphenidyl, were successfully separated by capillary zone electrophoresis with end-column Ru(bPY)(3)(2+) ECL detection. The relative drug binding to human serum albumin (HSA) for each single drug as well'as for the three drugs binding simultaneously was calculated. It was found that the three antiparkinsonian drugs compete for the same binding site on HSA. This work demonstrated that Ru(bPY)(3)(2+) CE-ECL can be a suitable technique for studying drug-protein binding.

Biodegradable electrospun fibers for drug delivery

The influences of surfactants and medical drugs on the diameter size and uniformity of electrospun poly(L-lactic acid) (PLLA) fibers were examined by adding various surfactants (cationic, anionic, and nonionic) and typical drugs into the PLLA solution. Significant diameter reduction and uniformity improvement were observed. It was shown that the drugs were capsulated inside of the fibers and the drug release in the presence of proteinase K followed nearly zero-order kinetics due to the degradation of the PLLA fibers. Such ultrafine fiber mats containing drugs may find clinical applications in the future.

Benthic foraminiferal distribution in surface sediments along continental slope of the southern Okinawa Trough: dependance on water masses and food supply

Benthic foraminiferal analysis of 29 samples in surface sediments from the southern Okinawa Trough is carried out. The results indicate that benthic foraminiferal abundance decreases rapidly with increasing water depth. Percentage frequencies of agglutinated foraminifera further confirm the modem shallow carbonate lysocline in the southern Okinawa Trough. From continental shelf edge to the bottom of Okinawa Trough, benthic foraminiferal fauna in the surface sediments can be divided into 5 assemblages: (1) Continental shelf break assemblage, dominated by Cibicides pseudoungerianus, corresponds to subsurface water mass of the Kuroshio Current; (2) upper continental slope assemblage, dominated by Cassidulina carinata, Globocassidulina subglobosa, corresponds to intermediate water mass of the Kuroshio Current; (3) intermediate continental slope assemblage, dominated by Uvigerina hispida, corresponds to the Okinawa Trough deep water mass above the carbonate lysocline; (4), lower continental slope - trough bottom assemblage, dominated by Pullenia bulloides, Epistominella exigua and Cibicidoides hyalinus, corresponds to deep water mass of the Okinawa Trough; and (5) trough bottom agglutinated assemblage, dominated by Rhabdammina spp., Bathysiphon flavidus, corresponds to I strongly dissolved environment of the trough bottom. The benthic foraminiferal fauna in the southern Okinawa Trough are controlled jointly by water masses and food supply. Water temperature, oxygen concentration and carbonate dissolution of the water masses are important controlling factors especially for the continental shelf break and trough bottom assemblages. The food supply also plays an important role in these benthic foraminiferal assemblages along the western slope. of the Okinawa Trough. Both the abundance and the 5 assemblages of benthic foraminifera correspond well to the organic matter supply along the continental slope and a lateral transport of TSM (total suspended matter) and POC (particulate organic carbon) from the shelf break to the deep water is also an important food supply for benthic fauna in this region.

The combined effects of temperature and food supply on Calanus sinicus in the southern Yellow Sea in summer

The effects of temperature and food availability on the life history strategy of the planktonic copepod Calanus sinicus in the southern Yellow Sea in summer were studied in this paper. The fifth copepodite stage (CV) dominates the population in the central part of the southern Yellow Sea, where the Yellow Sea Cold Water Mass (YSCWM) occurs below the thermocline. Incubation experiments were conducted on CV C. sinicus caught from the YSCWM to examine the effects of temperature and food availability. Temperature at the surface (27degreesC) is lethal to CVs regardless of food availability. At the temperature in the middle of the thermocline (18degreesC), survival time of the specimens depends on food availability, being similar to20 days in treatments without extra food supply. At the temperature in the YSCWM (9degreesC), most animals survive at the end of 27 day incubation even in treatments without food supply. Developmental rate of CVs at 9degreesC without extra food supply is extremely low. The increase of either temperature or food supply promotes the developmental rate of CVs. According to these results, the surface layers with high temperature and low food abundance are detrimental for the survival and reproduction of C. sinicus. Low temperature and low food availability in the YSCWM help CV to maintain a much lower developmental rate and higher survival rate. The ecological trait of C. sinicus in the southern Yellow Sea in summer cannot be sufficiently explained solely by the effects of temperature.

Independence of alpine meadow plants from soil organic matter for nitrogen supply: evidence from stable nitrogen isotopes

Stable nitrogen isotope signatures of major sources of mineral nitrogen ( mineralization of soil organic nitrogen, biological N-2 fixation by legumes, annual precipitation and plant litter decomposition) were measured to relatively define their individual contribution to grass assimilation at the Haibei Alpine Meadow Ecosystem, Qinghai, China. The results indicated that delta N-15 values (- 2.40 parts per thousand to 0.97 parts per thousand) of all grasses were much lower than those of soil organic matter (3.4 +/- 0.18 parts per thousand) and mineral nitrogen ( ammonium and nitrate together,7.8 +/- 0.57 parts per thousand). Based on the patterns of stable nitrogen isotopes, soil organic matter (3.4 +/- 0.18 parts per thousand), biological N-2 fixation (0 parts per thousand), and precipitation (- 6.34 +/- 0.24 parts per thousand) only contributed to a small fraction of nitrogen requirements of grasses, but plant litter decomposition (- 1.31 +/- 1.01 parts per thousand) accounted for 67%.

Determination of five pharmacologically active compounds extracted from Rhodiola for natural product drug discovery with HPLC-APCI-MS

A rapid and sensitive liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS) assay for the determination of five pharmacologically active compounds (PAC) extracted from the traditional Chinese medicine, Rhodiola , namely salidroside, tyrosol, rhodionin, gallic acid, and ethyl gallate has been developed. In this method, PAC could be baseline separated and detected with DAD at 275 nm. The validation of the method, including sensitivity, linearity, repeatability, and recovery, was examined. The linear calibration curves were acquired with correlation coefficient >0.999 and the limits of detection LOD (at a signal-to-noise ratio=3:1) were between 0.058 and 1.500 mu mol/L. It was found, that the amounts of PAC varied with different species of Rhodiola . The established method is rapid and reproducible for the separation of five natural pharmacologically active compounds from extracts of Rhodiola with satisfactory results.

Analysis of five pharmacologically active compounds from Rhodiola for natural product drug discovery with capillary electrophoresis

A rapid capillary electrophoresis method for the separation of five natural pharmacologically active compounds from extracted Rhodiola, namely salidroside, tyrosol, rhodionin, gallic acid and ethyl gallate has been developed. The separation of five natural pharmacologically active compounds was carried out in a fused-silica capillary with 14 mM boric acid, 30 mM SDS and 2.5% acetonitrile, adjusted to pH 10.7 with NaOH. Applied potential was 21 kV. The temperature of the capillary was maintained at 25 degreesC by the instrument thermostating system, with the correlation coefficients of 0.9805-0.9989 for migration time, and relative standards of < 3.52% for peak areas. The established method is rapid and reproducible for the separation of five natural pharmacologically compounds from extracts of Rhodiola with satisfactory results.

Drug-protein interaction studied by technique of microdialysis combined with high performance liquid chromatography

Drug-protein binding is an important process in determining the activity and fate of a pharmaceutical agent once it has entered the body. This review examines the method of microdialysis combined with high-performance liquid chromatography (HPLC) that has been developed;by ours to study such interactions, in which the microdialysis was applied to sample the free drug in the mixed solution of drug with protein, and HPLC to quantify the concentration of free drug in the microdialysate. This technique has successfully been used for determining various types of binding interactions between the low affinity drugs, high affinity drugs and enantiomers to HSA. For the case of competitive binding of two drugs to a protein in solution, a displacement equation has been derived and examined with four nonsteroidal anti-inflammatory drugs and HSA as model drugs and protein, respectively. Microdialysis with HPLC was adopted to determine simultaneously the free solute and displacing agent in drug-protein solutions. The method is able to locate the binding site and determine affinity constants even up to 10(7) L/mol accurately.

Study of interaction between drug enantiomers and serum albumin by capillary electrophoresis

The interaction between drugs and human serum albumin (HSA) was investigated by capillary electrophoresis (CE). It involves stereoselectivity, drug displacement and synergism effects. Under protein-drug binding equilibrium, the unbound concentrations of drug enantiomers were measured by frontal analysis (FA). The stereoselectivity of verapamil (VER) binding to HSA was proved by the different free fractions of two enantiomers. In physiological pH (7.4, ionic strength 0.17 phosphate buffer) when 300 mu M (+/-) VER were equilibrated with 500 mu M HSA, the concentration of unbound S-VER was about 1.7 times its antipode. The binding constants of two enantiomers, KR-VER and KS-VER, were 2670 and 850 M-1, respectively. However, no obvious stereoselective binding of propranolol (PRO) to HSA was observed. Trimethyl-beta-cyclodextrin (45 mM) was used as a chiral selector in pH 2.5 phosphate buffer. Several drug systems were studied by the method. When ibuprofen (IBU) was added into VER-HSA solution. R-VER was partially displaced while S-VER was not displaced at all. A binding synergism effect between bupivacaine (BUP) and verapamil was observed and further study suggested that verapamil and bupivacaine occupy different binding site of HSA (site II and site III, respectively).

Application of liquid pre-column capillary electrophoresis technique to the study of interaction between drug enantiomers and human serum albumin

Based on the chiral separation of several basic drugs, dimetindene, tetryzoline, theodrenaline and verapamil, the liquid pre-column capillary electrophoresis (LPC-CE) technique was established. It was used to determine free concentrations of drug enantiomers in mixed solutions with human serum albumin (HSA). To prevent HSA entering the CE chiral separation zone, the mobility differences between HSA and drugs under a specific pH condition were employed in the LPC. Thus, the detection confusion caused by protein was totally avoided. Further study of binding constants determination and protein binding competitions was carried out. The study proves that the LPC technique could be used for complex media, particularly the matrix of protein coexisting with a variety of drugs.