Acetylcholine receptor binding properties and ion permeability response after covalent attachment of the local anaesthetic quinacrine

Membrane vesicles rich in nicotinic acetylcholine receptor prepared from Torpedo californica electric tissue have been irreversibly modified with quinacrine mustard, an alkylating derivative of the local anaesthetic quinacrine. The reaction blocked the ion channel regulated by the acetylcholine receptor. Acetylcholine still bound to the modified membrane vesicles with K_D approx. 10^?8. The number of binding sites was reduced by up to 50%. Stopped-flow experiments showed that in contrast to what had been found with reversibly binding quinacrine no fluorescence changes caused by energy transfer from the irradiated protein to the fluorescent local anaesthetic occurred after addition of agonist. This indicates that the conformational changes associated with the activation of the ion channel are blocked by the covalent reaction with quinacrine mustard. Analysis of the membrane vesicles by SDS-polyacrylamide gel electrophoresis showed that all polypeptide chains assumed to be part of the receptor complex had reacted with the mustard. Even small components, probably lipids, migrating with the dye front, showed fluorescence.     

Terpenoids of the essential oil from Molopospermum peloponnesiacum roots

The investigation of the essential oil from Molopospermum peloponnesiacum roots afforded, in addition to some well known terpenoids, two aromatic aldehydes, which were found for the first time as volatile oil components. Their structures were elucidated by spectroscopic methods. The formation of these aldehydes during steam distillation from unstable precursors is discussed.     

Shell size variation of the planktonic foraminifer Neogloboquadrina pachyderma sin. in the Norwegian–Greenland Sea during the last 1.3 Myrs: implications for paleoceanographic reconstructions

We present measurements of the maximum diameter of the planktonic foraminifer Neogloboquadrina pachyderma sin. from six sediment cores (Ocean Drilling Program sites 643, 644, 907, 909, 985 and 987) from the Norwegian–Greenland Sea. Our data show a distinct net increase in mean shell size of N. pachyderma sin. at all sites during the last 1.3 Ma, with largest shell sizes reached after 0.4 Ma. External factors such as glacial–interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of N. pachyderma sin. We consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of N. pachyderma sin. to the cold water environment after 1.1–1.0 Ma. Probably, the Mid Pleistocene climate shift and the associated change of amplitude and frequency of glacial–interglacial fluctuations have triggered the evolution of this planktonic foraminifer. Oxygen and carbon stable isotope analyses of different shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis. For paleoceanographic reconstructions, the evolutionary adaptation of Neogloboquadrina pachyderma sin. to the cold water habitat has significant implications. Carbonate sedimentation in highest latitudes is highly dependent on the presence of this species. In the Norwegian–Greenland Sea, carbonate-poor intervals before 1.1 Ma are, therefore, not necessarily related to severe glacial conditions. They are probably attributed to the absence of this not yet polar-adapted species. Further, transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could, therefore, contain a large range of errors if they were applied to samples older than 1.1–1.0 Myrs.     

Production of poly-D(-)-3-hydroxybutyrate and poly-D(-)-3-hydroxyvalerate by strains ofAlcaligenes latus

Alcaligenes latus strains can accumulate poly-D(-)-3-hydroxybutyrate (PHB) up to about 85% of cell dry weight. The abilities to store poly-D(-)-3-hydroxyvalerate (PHV) of three strains ofA. latus were investigated. With Na-propionate as PHV precursor, strainA. latusDSM 1122 had better PHV accumulation ability than strainsA. latusDSM 1123 and 1124. StrainA. latus DSM 1123 could store PHV when Na-valerate but not Na-propionate served as the PHV precursor. PHB and PHV accumulation byA. latus DSM 1124 rapidly increased when propionic acid and acetic acid were together added to the fermentor. This increase was not obtained in the culture shaker flask and fermentor growing the same strain when Na-propionate alone served as a PHV precursor.