upon Tyne NEI 7RU As a result of methylation, benzoylation, and other chemical experiments, as well as of studies of the conversion into melanin of samples of dopamine specifically labelled with deuterium at each of the a-, p-, 2-, 5-, and 6-positions (separately), a preliminary outline structure is put forward to represent autoxidative dopamine-melanin. This melanin differs considerably from autoxidative dopa-melanin ; in particular, it is suggested that N-C polymeric linkages may be important, and that more uncyclised side chains are present than in dopa-melanin.

No abstract

The interactions of the three human embryonic haemoglobins with chloride ions have been investigated. Each of the three embryonic haemoglobins exhibits a unique pattern of oxygen-affinity-dependence on chloride ion concentration. Human embryonic haemoglobin Portland (zeta 2 gamma 2) is found to be completely insensitive to chloride ion concentration. Haemoglobin Gower I (zeta 2 gamma 2) shows a small concentration dependence, whilst haemoglobin Gower II (alpha 2 epsilon 2) exhibits a dependence approaching that of the adult protein. The degree of co-operativity for each protein is essentially chloride concentration independent. The chloride-dependent and -independent components of the alkaline Bohr effects have been measured for each of the embryonic haemoglobins and compared with that of the adult protein. Both the chloride-binding data and the Bohr effect have been analysed in terms of the recently developed allosteric model proposed by Perutz [Perutz, Fermi, Poyart, Pagnier and Kister (1993) J. Mol. Biol. 233, 536-545].

No abstract

The (&)-ketone (la) (1,3,4,6,7,11 b-hexahydro-9,l O-dimethoxybenzo[a]quinolizin-2-one) has been converted into racemic C(3)-bisnoremetine (IXa) via an N-(3,4-dimethoxyphenethyl) amide which was shown to have the same relative configuration as emetine a t C -l l b and C-2. The (-)-ketone (Ib) [3-methyl derivative of (la)],obtained by asymmetric transformation of the racemic compound, was converted into (-) -C(3)-noremetine (IXb). (-)-1',8a'-Secoemetine (XI) and the (-)-analogues (Xlla-d) have also been prepared. Only compounds (IXa), (IXb), and (XI) showed appreciable amoebicidal activity.