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At least 289 records · Page 16Linked to original sources

PubMed1985

Trichotoxin A40. Purification by counter-current distribution and sequencing of isolated fragments.

The isolation of the membrane-modifying polypeptide antibiotics from the mycelium of Trichoderma viride 5242 was optimized via extraction with dichloromethane and chromatography on Sephadex LH-20. The components trichotoxin A40 and A50 were separated from each other and purified by multiplicative counter-current distribution. The sequence of proteinase-resistant trichotoxin A40 was determined by combined gas chromatography and mass spectrometry of three isolated N-acetylated dodecapeptides and two N-prolylhexapeptides obtained after selective trifluoroacetolysis. Including amino acid exchanges due to natural microheterogeneity, the sequence is Ac-Aib-Gly(LAla)-Aib-LLeu-Aib-LGln-Aib-Aib-Aib(LAla )-LAla-Aib-Aib-LPro-LLeu -Aib-DIva(Aib)-LGlu-LValol. In contrast to the eicosapeptide alamethicin, trichotoxin A40 contains only 18 residues, with a higher proportion of alpha-aminoisobutyric acid (Aib), C-terminal L-valinol (Vol), one D-isovaline (Iva) and no proline at the N-terminal part.

Amino Acid Sequence↗

PubMed1976

Hydrophobic affinity partition of spinach chloroplasts in aqueous two-phase systems.

The surface properties of spinach chloroplasts, both of intact chloroplasts with surrounding envelope and broken chloroplasts consisting of the inner lamellar system, have been studied by partitioning them between two aqueous phases, especially using counter-current distribution technique. The two-phase system consists of poly(ethyleneglycol), dextran and water. The two polymers are enriched in opposite phases and by binding deoxycholate or palmitate to one of the polymers the affinity of chloroplasts for the corresponding phase is strongly enhanced. The partition of the two classes of chloroplasts, however, is not affected to the same degree and the affinity of the chloroplast envelope for deoxycholate and palmitate is stronger than that of the lamellar system. This has been correlated to the chemical composition of the two types of membranes. By studying the effect of salts on the partition it has been found that the lamellar system bears a larger number of negative charges as compared to the envelope of the intact chloroplast.

Binding Sites↗

PubMed1994

Revealing surface changes associated with maturation of ram spermatozoa by centrifugal counter-current distribution in an aqueous two-phase system.

Centrifugal counter-current distribution (CCCD) in an aqueous two-phase system was used to detect changes associated with maturation of ejaculated ram spermatozoa. Spermatozoa obtained from three successive ejaculates of rams maintained in abstinence for one, two and three days were fractionated by CCCD. The results show that these ejaculates are relatively enriched in a cell population which presents a very high enhanced affinity to the lower dextran-rich phase. This cell population is not associated with loss of acrosomal integrity. In addition, it tends to disappear with longer abstinence periods, or after successive ejaculations at the same abstinence period, strongly suggesting that it is composed of immature cells. Therefore, phase partitioning can detect surface changes accompanying sperm maturation and offers a new possibility for sperm quality analysis.

Animals↗

PubMed1989

Partition coefficients of low-molecular-weight volatile chemicals in various liquids and tissues.

Partition coefficients are required for developing physiologically based pharmacokinetic models used to assess the uptake, distribution, tabolism, and elimination of volatile chemicals in mammals. A gas-phase vial equilibration technique is presented for determining the liquid:air and tissue:air partition coefficients for low-molecular-weight volatile chemicals. This technique was developed from two previously described medium:air methods, relied solely on measurement of chemical concentration in the gas phase, and, compared to earlier work, extends the range of chemicals and tissues examined. Partition coefficients were determined with 0.9% saline, olive oil, and blood, liver, muscle, and fat tissues from rats for 55 compounds. Human blood:air coefficients were determined for 36 compounds and several blood:air values were also determined in the mouse and for one compound in the hamster. An approach is described for predicting the tissue solubilities of untested compounds based on oil:air and saline:air coefficients using regression analyses. A similar approach is used to model fat:air coefficients in terms of oil:air values and to model human blood: air coefficients in terms of rat blood:air coefficients.

Adipose Tissue↗

PubMed1980

The seminal excretion, plasma elimination, tissue distribution and metabolism of naltrexone in the rabbit.

The pharmacokinetics, tissue distribution and metabolism of naltrexone were studied in male New Zealand White rabbits. After an i.v. bolus, the plasma half-life of naltrexone between 30 min and 3 hr was 55 +/- 5 min and 53 +/- 3 min for 1 and 5 mg/kg doses of naltrexone . HCl, respectively. The drug concentration in the semen reached a maximum value between 15 and 30 min after the injection. At 120 min, the semen/plasma drug concentration ratio was 14 and 11 for the 1 and 5 mg/kg doses, respectively. Three minutes after injection, 95% of the drug had left the plasma. After 5 min, the conjugate levels exceeded the free drug levels in the plasma suggesting rapid glucuronidation of the drug. The concentrations of naltrexone and 6-beta-naltrexol were measured in different tissues 90 min after injection. Most of the tissues had drug concentrations which exceeded the concurrent plasma concentration. The highest concentrations were observed in the submaxillary gland. Relatively high amounts of 6-beta-naltrexol were found in the brain, fat, spleen, heart, testis, kidney and urine. The principle urinary metabolite was the glucuronide of naltrexone. Minor metabolites identified in urine treated with Glusulase were 6-beta-naltrexol and N-dealkylated naltrexone.

Animals↗

PubMed1988

Partitioning behavior of erythrocytes in aqueous two-phase systems containing hydroxypropyl starch and polyethylene glycol.

The partitioning behavior of erythrocytes in Reppal PES 200 (a hydroxypropyl starch produced by Reppe Glykos AB, Växjö, Sweden)-polyethylene glycol (PEG) and in dextran (Dx)-PEG aqueous phase systems made isotonic with phosphate is similar in a number of ways: (i) There is a correlation between the relative electrophoretic mobilities and partition ratios, P, of red blood cells from different species; (ii) The cell P is reduced when, at constant polymer concentrations, phosphate is systematically replaced by sodium chloride (with the total concentration isotonic); (iii) The cell P is increased with reduced polymer concentrations (decreased interfacial tensions); (iv) Treatment of erythrocytes with neuraminidase results in a reduced P value; (v) Rat red cells of different ages can be fractionated by counter-current distribution; and (vi) Differences between red blood cells from genetically distinct rats or between humans can be detected. Aquaphase (a hydroxypropyl starch marketed by Perstorp AB, Lund, Sweden) has been tested as in ii-iv above with analogous results. The partitioning behavior of erythrocytes in PES-PEG and Dx-PEG aqueous phase systems containing sodium chloride differs in a number of ways: (vii) The correlation, apparent in Dx-PEG systems, between the P value of red blood cells from different species and the ratio of their membrane poly- to monounsaturated fatty acids is absent in PES-PEG systems. It is replaced by a correlation as in i; (viii) The increase in P value in Dx-PEG observed from red blood cells after treatment with neuraminidase is replaced by a decrease in P value in PES-PEG or Aquaphase-PEG systems. We conclude that PES (and Aquaphase) can be substitutes for dextran in cell partitioning studies when charge-sensitive phases are used (e.g., those containing phosphate) while separations based on properties reflected by Dx-PEG systems containing sodium chloride are not duplicated by PES-PEG (and probably not by Aquaphase-PEG). The hydroxypropyl starch-PEG systems containing sodium chloride, unlike the analogous Dx-PEG systems, have a significant electrostatic potential difference between the phases.

Aging↗

PubMed1982