Towards synthetic adrenaline receptors--shape-selective adrenaline recognition in water

In spite of their key role in signal transduction, the mechanism of action of adrenergic receptors is still poorly understood. We have imitated the postulated binding pattern of the large membrane protein with a small, rationally designed synthetic host molecule. Experimental evidence is presented for the simultaneous operation of electrostatic attraction, hydrogen bonds, pi stacking, and hydrophobic interactions. By virtue of this combination of weak attractive forces, adrenaline derivatives in water are bound with high shape selectivity for the slim dopamine skeleton. We think that these findings support the postulated cooperative interplay of noncovalent interactions in the natural receptors. In addition, they provide access to a new type of adrenaline sensor. This may be the first step towards an artificial signal-transduction system.     

Towards synthetic adrenaline receptors

The macrocyclic bisphosphonate 2 forms complexes with amino alcohols, amines, and amino acid esters with high association constants in polar organic solvents. Exertion of solvophobic interactions inside the macrocyclic cavity in DMSO and methanol leads to specificity for guest molecules with hydrophobic moieties. Experimental evidence is presented for the insertion of the guest molecules' nonpolar groups into the macrocycle's hydrophobic cavity. NMR spectra of complexes with 2 in DMSO show a molecular imprint of the guest molecule; this gives information about its location inside the macrocycle. In aqueous solutions strong self-association of 2 occurs, which is explained by distinct structural similarities between 2 and micelle-forming phospholipids.     

A differential spectrofluorimetric determination of adrenaline and noradrenaline

A simple, sensitive method for the differential fluorimetric determination of 0.0I–1 μg/ml amounts of adrenaline and noradrenaline is proposed. Oxidation is best done with potassium hexacyanoferrate(III) at pH 6.8. The fluorescent derivatives of adrenaline and noradrenaline, and of noradrenaline alone, are stabilized respectively with alkaline ascorbate or with cysteine-thioglycolli acid mixture, and the fluorescence is measured at 409 and 520 nm respectively.     

肾上腺素盐酸盐和水的相互作用研究

使用核磁共振和电化学循环伏安法,对肾上腺素盐酸盐(AH)和水的相互作用进行了探讨.研究结果表明:AH不仅能和水分子形成分子间氢键,当浓度较大时,AH的苯环还可发生π-π堆积作用.此外,溶液pH对二者相互作用基本无影响.     

Kinetics of the autoxidation of adrenaline and [copper(II)(adrenaline)]2+ in alkaline aqueous and micellar media

The kinetics of autoxidation of adrenaline and [Cu(adrenaline)]²⁺ complex by dissolved oxygen in alkaline aqueous and micellar media has been studied. The reaction is initiated by the removal of amino-H⁺ protons of adrenaline by hydroxide ion, followed by cyclization. The values of (1/k _obs) for the autoxidation of both species were found to be linearly dependent upon 1/[OH^?]. The reaction follows a consecutive pathway in which the intermediate adrenochrome remains stable for few minutes, and then undergoes further reactions to yield adrenolutin and other products. The [Cu(adrenochrome)]⁺ complex is stable for a few hours. Studies on the effects of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) on the reactivity of both species revealed different behaviors. The micelles of CTAB catalyzed the rates of autoxidation for both species, whereas SDS micelles inhibited the autoxidation of adrenaline but catalyzed the rate of autoxidation of [Cu(adrenaline)]²⁺. Addition of the reactive counterion surfactant, cetyltrimethylammonium hydroxide (CTAOH) initially increased the rate constant with the increasing [CTAOH], until it reached a plateau for k _ψ ?[CTAOH]. Salts such as NaCl, NaBr, tetramethyl ammonium bromide, and tetraethyl ammonium bromide increased the rate when added at lower concentrations, but had negligible effect at higher concentrations. The results obtained in micellar media were treated according to Berezin’s Pseudophase Model. The various kinetic parameters for the reactions occurring in aqueous and in micellar media are reported.     

Determination of adrenaline and noradrenaline by resonance Raman spectrometry

Aminochromes of adrenaline and noradrenaline show resonance Raman scattering at 1480 and 1430 cm(-1) respectively, with Ar(+) excitation. Scattering intensity is a linear function of concentration. Detection limits are 1 x 10(-6)M. Both catecholamines can be determined in a single measurement.     

Cyclic adrenaline derivatives. Aryl-2-Piperidyl-Carbinols

A synthetic route; to 3,4-dihydroxyphenyl-(2-piperidyl)earbinols is described. These novel catecholamines may be regarded as derivatives of adrenaline containing a cyclic side-chain moiety. Their biological action appears to be more selective than that of adrenaline or isoprenaline and the more active of these compounds show promise as powerful bronchodilators with minimum cardiac effect.     

Determination of adrenaline by using inhibited Ru(bpy)3 electrochemiluminescence

Adrenaline was found to inhibit strongly the electrochemiluminescence (ECL) from the Ru(bpy)₃²⁺/tripropylamine system when a working Pt electrode was maintained at 1.05 V (versus Ag/AgCl) in pH 8.0 phosphate buffer. On this basis, a flow injection (FI) procedure with inhibited electrochemiluminescence detection has been developed for determination of adrenaline. The method exhibited a good reproducibility, sensitivity, and stability with a detection limit (signal-to-noise ratio = 3) of 7.0×10⁻⁹ mol l⁻¹ and dynamic concentration range of 2×10⁻⁸ to 1×10⁻⁴ mol l⁻¹. The relative standard deviation was 2.2% for 1.0×10⁻⁶ mol l⁻¹ adrenaline (n=11). The method was successfully applied to the determination of adrenaline in pharmaceutical samples. Moreover, ECL emission spectra, UV-Vis absorption spectra and cyclic voltammograms of Ru(bpy)₃²⁺/tripropylamine/adrenaline were studied. The inhibition mechanism has been proposed as the interaction of electrogenerated Ru(bpy)₃^2+* and the o-benzoquinone derivatives, adrenochrome and adrenalinequinone, at the electrode surface.     

酶催化动力学光度法测定肾上腺素

基于肾上腺素对血红蛋白酶催化体系的抑制作用, 建立了酶催化动力学光度法测定肾上腺素的新方法. 实验研究了体系的最佳条件及动力学行为, 测定的线性范围为4.5×10-7～1.4×10-5 mol/L, 方法检出限为5.2×10-8 mol/L. 对浓度为9.0×10-6 mol/L的肾上腺素进行11次平行测定的相对标准偏差为3.5%. 此方法可用于药剂中肾上腺素含量的测定.     

Fluorescence derivatization for trace determination of some alkaloids and adrenaline.

Derivatization with dans-Cl was studied for adrenaline, cephaeline, codeine, emetine, ephedrine and morphine. Titrimetry was used to study the derivatization step and to determine the ratios of reagent to reactant. Only codeine did not react. The other five compounds formed single derivatives with emission maximum wavelengths between 490 and 515 nm. Reactions were quantitative after 20 min at 45°C with a 6–7-fold excess of reagent. Fluorescence was measured after extraction into benzene. Detection limits between 0.12 and 0.44 $\text{nmole}\text{5 ml}$ were observed. The relative standard deviation at 2 $\text{nmole}\text{5 ml}$ was ±2%. Derivatives could be separated by t.l.c. to eliminate fluorescence or quenching interferences; fluorescence was then measured after elution of the spots. About a 7-fold lowering of the detection limit was achieved.     

Evaluation of GSH adducts of adrenaline in biological samples

The sustained high release of catecholamines to circulation is a deleterious condition that may induce toxicity, which seems to be partially related to the products formed by oxidation of catecholamines that can be further conjugated with glutathione (GSH). The aim of the present study was to develop a method for the determination of GSH adducts of adrenaline in biological samples. Two position isomers of the glutathion-S-yl-adrenaline were synthesized and characterized by HPLC using diode array, coulometric and mass detectors. A method for the extraction of these adducts from human plasma was also developed, based on adsorption to activated alumina, which showed adequate recoveries and proved to be crucial in removing interferences from plasma. The selectivity, precision and linearity of the method were all within the accepted values for these parameters. Furthermore, the sensitivity of this method allows the detection of adduct amounts that are within the range of the expected concentrations for these adducts under certain pathophysiological conditions and/or drug treatments. In conclusion, the development of this method allows the direct analysis of GSH adducts of adrenaline in human plasma, providing a valuable tool for the study of the catecholamine oxidation process and its related toxicity.     

Development of integrated chemiluminescence flow sensor for the determination of adrenaline and isoprenaline

A novel integrated chemiluminescence (CL) flow sensor for the determination of adrenaline and isoprenaline is developed based on the enhancing effect of analytes on CL emission of luminol oxidized by periodate in alkaline solution. The analytical reagents luminol and periodate are immobilized on anion exchange resins, respectively, and packed in a glass tube to construct a reagentless sensor. The proposed sensor allows the determination of adrenaline and isoprenaline over the range from 2.0×10⁻⁸ to 1.0×10⁻⁵ g ml⁻¹ and 2.0×10⁻⁷ to 5.0×10⁻⁵ g ml⁻¹, respectively. The detection limits are 7.0×10⁻⁹ g ml⁻¹ for adrenaline and 5.0×10⁻⁸ g ml⁻¹ for isoprenaline with a relative standard deviation of 1.7% for the 1.0×10⁻⁷ g ml⁻¹ adrenaline (n=11) and 2.1% for 1.0×10⁻⁶ g ml⁻¹ isoprenaline (n=11). The sample throughput was 60 samples h⁻¹. The sensor has been successfully applied to the determination of adrenaline and isoprenaline in pharmaceutical preparations.     

Study on the stability of adrenaline and on the determination of its acidity constants

In this work, the results are presented concerning the influence of time on the spectral behaviour of adrenaline (C(9)H(13)NO(3)) (AD) and of the determination of its acidity constants by means of spectrophotometry titrations and point-by-point analysis, using for the latter freshly prepared samples for each analysis at every single pH. As the catecholamines are sensitive to light, all samples were protected against it during the course of the experiments. Each method rendered four acidity constants corresponding each to the four acid protons belonging to the functional groups present in the molecule; for the point-by-point analysis the values found were: log beta(1) = 38.25 +/- 0.21, log beta(2) = 29.65 +/- 0.17, log beta (3) = 21.01 +/- 0.14, log beta(4) = 11.34 +/- 0.071.     

Kinetic determination of adrenaline,l-dopa and their mixtures with a stopped-flow spectrophotometric technique

Catecholamines (adrenaline and L-Dopa) can be determined by a stopped-flow spectrophotometric technique. For individual determinations, catecholamines are oxidized to the corresponding o-benzoquinones by hexachloroiridate(IV). Concentrations in the range 2·10^-4–2·10^-3 M can be determined with errors of about 2 %. For evaluation of mixtures, aminochromes are formed. The method allows a catecholamine concentration of about 5·10^-6 M to be determined in the presence of a ten-fold amount of another catecholamine, with a maximum error of about 10 %.