Studies of the thiadiazine, taurolidine-I. Identification of the molecular species present in aqueous solutions by (1)H- and (13)C-NMR spectroscopy

The equilibria in deuterium oxide solutions of the diamine, 4,4'-methylenebis(tetrahydro-1,2,4-thiadiazine-1,1-dioxide), were studied using highfield (1)H- and (13)C-NMR with the aid of solutions of tetrahydro-2H-1,2,4-thiadiazine-1,1-dioxide (taurultam), its two N-methyl detivatives and methylene glycol. Comparison of the (1)H-NMR spectrum of taurolidine with the one obtained from a mixture of taurultam and methylene glycol indicated that the same equilibria exists in both these solutions. It was concluded that taurolidine, taurultam and its 4-hydroxymethyl adduct and methylene glycol are the major components present. To facilitate the interpretation of the (13)C-spectra, (13)C-enriched methylene glycol was added to solutions of taurultam. The (13)C-studies confirmed the (1)H-NMR study.

Some solution properties of pentagastrin and angiotensin: aggregation of pentagastrin

Pentagastrin and angiotensin have been studied in the presence and absence of urea by light-scattering, viscosity, dialysis, surface tension and other physicochemical techniques for evidence of peptide aggregation. Pentagastrin forms large linear, flexible aggregates (molecular weight 40 000) in phosphate buffer above a concentration of ∼0·1 g dl−1 and in solutions shows time-dependent flow behaviour. Angiotensin shows no evidence of aggregation beyond dimers. In 1m urea the pentagastrin is in the form of dimers.

Analysis of biogenic amines in the brain of the American cockroach (Periplaneta americana) by gas chromatography-negative ion chemical ionisation mass spectrometry

Biogenic amines in the brain of the American cockroach have been identified and quantified by an extraction-derivatisation procedure involving their reaction with ditrifluoromethylbenzoyl chloride (DTFMB) in the aqueous phase followed by extraction into an organic solvent, hydrolysis of phenolic esters and conversion of free hydroxyl groups to trimethylsilyl (TMS) ethers and subsequent analysis by gas chromatography-negative ion chemical ionisation mass spectrometry. The molecular ion of these DTFMB-TMS derivatives carried most of the ion current which made the method highly specific and gave a potential limit of detection below the picogram level. This method establishes unequivocally that the principal amines in cockroach brain are tyramine, p-octopamine, dopamine, 5-hydroxytryptamine and noradrenaline. In contrast to mammalian nervous tissue, the other positional isomers of octopamine, together with the isomeric synephrines, are absent.

Particle size stability of intralipid and mixed total parenteral nutrition mixtures

The determination of the particle size of Intralipid fat emulsions by the non-perturbing method of photon correlation spectroscopy has been extended to include particle size determination using the Coulter counter and optical microscopy. Although little increase in particle size in 3-litre bags containing total parenteral nutrition mixtures was observed with the methods involving large dilutions, creaming was observed and optical microscopy showed aggregation and some coalescence to have taken place. The problem of re-dispersion upon dilution of aggregated (but not coalesced) fat emulsions makes direct optical observation essential in assessing the stability and safety of such fat emulsion mixtures. The effect of electrolytes (NaCl and CaCl2) on creaming, particle size and electrophoretic mobility showed both minimum stability and minimum zeta potential at 3 X 10(-3) mol dm-3 CaCl2 and at 2.5 X 10(-1) mol dm-3 NaCl. Thus, these maximum levels for electrolytes in total parenteral mixtures are indicated.

NMR studies and GC analysis of the antibacterial agent taurolidine

The NMR spectrum of taurolidine in deuterium oxide was compared with spectra obtained from model experiments with amines and formaldehyde. Head-space analysis combined with capillary GC showed that there was less than 0.004% free formaldehyde present in 2% solutions of taurolidine. This value is comparable to the concentration of formaldehyde found when the taurolidine solutions were injected directly onto GC columns.

The preparation and properties of (+)- and (--)-guanoxan

(±)-2-Aminomethyl-1, 4-benzodioxan has been resolved into its optically active isomers: (+)- and (-)-guanoxan have been synthesized from these. The pharmacological effects of racemic-guanoxan and of the two optical isomers have been compared on the isolated central ear artery of the rabbit, on the pithed rat in which pressor responses were evoked by stimulation of the thoraco-lumbar sympathetic outflow, and on the pre- and post-ganglionically stimulated nictitating membrane of the cat. The two isomers were equipotent in producing adrenergic neuron blockade. Initial catecholamine release was weak in the cat, but occurred more powerfully in the rabbit ear artery and in the rat. Ability to produce this effect resided mainly with the (+)-isomer. α-Adrenoreceptor blocking activity was detectable in the rat and was produced mainly by the (+)-isomer suggesting that its stereochemical configuration corresponds to that of D-(-)-noradrenaline. Ganglion blockade was an unimportant action of the compounds, but both isomers possessed weak atropine-like activity in the rat.

The possible role of conformational isomerism in the biological actions of acetylcholine: spectral studies

Infrared studies of the NC-H stretching frequencies of selected trimethylammonium salts, including acetylcholine, were made in an attempt to obtain evidence that intramolecular NC-H—O hydrogen bonding is responsible for the existence in solution of a quasi-ring conformation for acetylcholine. Acetylcholine and related compounds were also examined by nuclear magnetic resonance spectroscopy. The carbonyl stretching frequencies of an homologous series of acetoxy alkyl sulphones were measured in dioxan solution to gain information on the effect of electron withdrawing substituents in the absence of intermolecular hydrogen bonding. The observed high ester carbonyl absorption frequency in acetylcholine may be interpreted in terms of the inductive effect from the onium nitrogen atom but the results are not incompatible with the existence of a quasi-ring conformation involving C-H—O hydrogen bonding between one of the N-methyl groups and the acetoxy oxygen atom.