[en] Met⁵-enkephalin - a pentapeptide (Tyr-Gly-Gly-Phe-Met) - can exist in two possible folded arrangements with a rigid two-hydrogen-bonded network. In one arrangement, a Gly 2-Gly 3 β-bend is formed and in the other a Gly 3-Phe 4 β-bend. The two conformations are distinguished by the spatial relation of Tyr 1 and Phe 4: in the Gly 2-Gly 3 β-bend, Tyr 1 and Phe 4 can be brought close to each other while in the Gly 3-Phe 4 β-bend they are far apart the authors have utilized one-dimensional nuclear Overhauser effect (NOE) measurements between the ring protons of Tyr 1 and Phe 4 to determine their proximity. The NOE data clearly show that a pair of protons, one each from Tyr 1 and Phe 4, are as close as 3.3 A while other inter-proton distances are beyond 4.5 A. Therefore, the authors propose the presence of a Gly 2-Gly 3 β-bend for Met⁵-enkephalin in solution. The structure of Met⁵-enkephalin in solution is very similar to the single crystal structure of Leu⁵-enkephalin and tends to explain the biological activity data of several modified enkephalins. (Auth.)

[en] The synthesis of ³H-labelled Met-enkephalin and Tyr-D-Ala-Gly-Phe-Met-NH₂ (DALA) and ¹⁴C-labelled Substance P (SP) from previously described, fully protected intermediates is reported. The labelled peptides were prepared by methylation with (³H)- or (¹⁴C)methyl iodide of the sulphide anions formed on deprotection of the corresponding S-benzyl-homocysteine precursors with sodium in liquid ammonia. After purification by LC, the labelled peptides were obtained in radiochemical yields in the range of 9 to 24% with a radiochemical purity higher than 97%. The specific radioactivities of the ³H- and ¹⁴C- labelled products, corresponding to the labelled methyl iodides used, were 80 mCi/μmol and 60 μCi/μmol, respectively. (author)

[en] A convenient synthesis of [1-¹⁴C]acetylcholine iodide in two steps is described. β-Dimethylaminoethanol is acetylated with [1-¹⁴C]acetic anhydride and the ester β-dimethylaminoethyl [1-¹⁴C]acetate quaternised with methyl iodide to afford [1-¹⁴C]acetylcholine iodide in an overall material yield of 50-52% and radiochemical yield 18%. (author)

[en] A simple, rapid and reliable procedure is described to simultaneously concentrated and purify β-endorphin, leu-and met-enkephalins from small volumes of human and rat plasma before radioimmunoassay is performed. It uses C₁₈ Sep-Pak reverse phase cartridges. The effectiveness of different protease inhibitors in preventing degradation of opiates by plasma and different solvent systems for eluting opiates is also evaluated

[en] β-CD and CM-β-CD as chiral NMR shift agents were used to resolve the enantiomers of noradrenaline (NA). The stoichiometry of each complex formed between the CDs and the enantiomers of NA was found to be 1 : 1 through the continuous variation plots. The binding constants (K) of the complexes were determined from 1H NMR titration curves. This result indicated that both β-CD and CM-β-CD formed the complexes with the S (+)-NA more preferentially than its R(.)-enantiomer. The K values for the complexes with β-CD (KS(+) = 537 M^-1 and K_R(_-) = 516 M^-1) was larger than those with CM-β-CD (K_S(₊) = 435 M^-1 and K_R(_-) = 313 M^-1), however, enantioselectivity (α) of S(₊)- and R(-)-NA to CM-β-CD (α = 1.38) was larger than that to β-CD (α = 1.04), indicating that CM-β-CD was the better chiral NMR solvating agents for the recognition of the enantiomers of NA. Two dimensional rotating frame nuclear Overhauser enhancement spectroscopy (ROESY) experiments were also performed to explain the binding properties in terms of spatial fitting of the NA molecule into the macrocyclic cavities

[en] [³H]U-69593 is an opiate agonist that has been reported to bind in vitro with high affinity and selectivity to the kappa receptor subtype. The studies reported here were designed to determine the optimal conditions for labeling kappa receptors with [³H]U-69593 and to further characterize the binding site. The effects of temperature and NaCl on [³H]U-69593 binding were of particular interest because previous studies reported that [³H]ethylketocyclazocine ([³H]EKC) and [³H]bremazocine binding to kappa receptors was optimal at 4⁰C in the presence of NaCl. Those conditions were not found to be optimal for [³H]U-69593 binding. Although the pharmacological specificity and Bmax of [³H]U-69593 binding was similar at room temperature and at 4⁰C, the binding affinity was approximately three times lower at 4⁰C than at room temperature. In addition, NaCl had an effect on [³H]U-69593 binding that was opposite that on [³H]EKC binding at 4⁰C. These differences between [³H]U-69593 and [³H]EKC binding at 4⁰C were accentuated by a vast difference in the density of the binding sites and suggested that [³H]U-69593 might bind selectively to a kappa receptor subtype

[en] The binding affinity to the μ receptor of some opioids chemically related to morphine and some of their metabolites was examined in rat brain homogenates with ³H-DAMGO. The chemical group at position 6 of the molecule had little effect on binding. Decreasing the length of the alkyl group at position 3 decreased the K_i values (morphine < codeine < ethylmorphine < pholcodine). Analgesics with high clinical potency containing a methoxyl group at position 3 had relatively weak receptor binding, while their O-demethylated metabolites had much stronger binding. Many opioids may exert their pharmacological actions predominantly through metabolites

[en] Total lymphoid irradiation (TLI) has been reported to be effective in the immunosuppressive treatment of certain human and experimental autoimmune disorders. We have investigated the effects of TLI in Lewis rats with experimental autoimmune myasthenia gravis (EAMG) produced by immunization with purified torpedo acetylcholine receptor (AChR). The radiation is given in 17 divided fractions of 200 rad each, and nonlymphoid tissues are protected by lead shielding. This technique suppresses the immune system, while minimizing side effects, and permits the repopulation of the immune system by the patient's own bone marrow cells. Our results show that TLI treatment completely prevented the primary antibody response to immunization with torpedo AChR, it rapidly abolished the ongoing antibody response in established EAMG, and it suppressed the secondary (anamnestic) response to a boost of AChR. No EAMG animals died during TLI treatment, compared with six control animals that died of EAMG. TLI produces powerful and prompt immunosuppression and may eventually prove useful in the treatment of refractory human myasthenia gravis

[en] A spectro fluorometric method was developed for determination of brassinosteroids plant hormones based on the reaction between brassinolide and m-dansylaminophenylboronic acid. 90 μM of m-dansylaminophenylboronic acid solution was chosen as the optimal concentration of the reagent. The temperature of the reaction was 30 degree Celsius (room temperature) for 20 min duration in 5 mM phosphate buffer solution, pH 7. The excitation and emission wavelengths were 380 nm and 505 nm, respectively. Under optimal condition, linearity was found in the range 1-50 μM. Standard addition was used for the brassinosteroids determination in bio-extract samples, without any sample preparation. Limit of detection (3SD, n=10) of 0.24 μM and limit of quantitation (10SD, n=10) of 0.48 μM were obtained using sample blank with this standard addition method. Result was demonstrated to be a suitable semi-quantitative technique and was applied successfully for the determination of total brassinosteroids plant hormones equivalent to brassinolide. (author)

[en] Abstract only