The bacteriorhodopsin proton pump: effect of crosslinkings of lysine residues

All six available lysine residues in bacteriorhodopsin were amidinated with dimethyl-3,3'-dithiobispropionimidate, which is a crosslinking agent. The photocycle was studied by measuring light absorption and electric signals. The data show an essential change in the photocycle: instead of single components, the rise of the signal due to the M intermediate can be decomposed into two components, and the decay into three. The life-times and the intensities of these components and in general the proton pumping activity of bacteriorhodopsin depend only negligibly upon pH. Changes upon removing the crosslinks are not significantly different from those in the crosslinked samples. The lysine residues therefore may not be considered of primary importance in proton translocation.     

Effect of primycin on some electric properties of the frog skeletal muscle

The effect of primycin, a guanidine-type antibiotic was studied on the electric properties and 42K+ uptake of the frog sartorius and semitendinosus muscle. Both in normal and choline chloride Ringer solution, primycin evoked a concentration and time dependent depolarization of the surface membrane of the muscle. This depolarization was significantly increased by Na ions. Primycin treatment was shown to evoke a dose-dependent decrease of the depolarization induced by 20 mM K+-Ringer. When the muscles were incubated in a Ringer solution containing choline chloride, during an incubation period of 30 min the uptake of 42K+ was decreased to 12% upon the exposure to 5 x 10(-6) mol primycin as compared to the control value. As the primycin-induced depolarization increased, the shape and amplitude of the action potentials elicited by square-wave electric impulses were altered and decreased, respectively. In sodium isaethionate Ringer 1--2 x 10(-6) M primycin induced a slow depolarization resulting in firing potentials. The results suggest that primycin depolarizes the surface membrane exclusively through the blockade of the resting K+ channels, the other phenomena being the results of this depolarizing effect.     

Continuous-flow solid-phase synthesis of potential antigenic peptides of hepatitis B virus

The synthesis of three hepatitis B surface antigens derived from S and pre-S proteins (adw S(140-147), [Tyr148] adw S(139-148), and adw pre-S(120-145)) has been accomplished by the continuous flow Fmoc-polyamide solid phase method. The use of different scavengers and trimethylsilyl bromide (TMSBr) in trifluoroacetic acid as deprotecting procedures is discussed.     

Production, crystallization, and preliminary X-ray analysis of rabbit skeletal muscle troponin complex consisting of troponin C and fragment (1-47) of troponin I.

Troponin is a ternary protein complex consisting of subunits TnC. TnI, and TnT, and plays a key role in calcium regulation of the skeletal and cardiac muscle contraction. In the present study, a partial complex (CI47) was prepared from Escherichia coli-expressed rabbit skeletal muscle TnC and fragment 1-47 of TnI, which is obtained by chemical cleavage of an E. coli-expressed mutant of rabbit skeletal muscle TnI. Within the ternary troponin complex, CI47 is thought to form a core that is resistant to proteolytic digestion, and the interaction within CI47 likely maintains the integrity of the troponin complex. Complex CI47 was crystallized in the presence of sodium citrate. The addition of trehalose improved the diffraction pattern of the crystals substantially. The crystal lattice belongs to the space group P3(1)(2)21, with unit cell dimensions a = b = 48.2 A, c = 162 A. The asymmetric unit presumably contains one CI47 complex. Soaking with p-chloromercuribenzenesulfonate (PCMBS) resulted in loss of isomorphism, but enhanced the quality of the crystals. The crystals diffracted up to 2.3 A resolution, with completeness of 91% and R(merge) = 6.4%. The crystals of PCMBS-derivative should be suitable for X-ray studies using the multiple-wavelength anomalous diffraction technique. This is the first step for elucidating the structure of the full troponin complex.     

Colonization and extinction of land planarians (Platyhelminthes,Tricladida) in a Brazilian Atlantic Forest regrowth remnant

Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two initially most abundant species, which are native to the study site, Notogynaphallia ernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed in lab conditions. Júlio Pedroni: Granted by CNPQ–Brazil.     

Body Size,Growth and Life Span: Implications for the Polewards Range Shift of Octopus tetricus in South-Eastern Australia

Understanding the response of any species to climate change can be challenging. However, in short-lived species the faster turnover of generations may facilitate the examination of responses associated with longer-term environmental change. Octopus tetricus, a commercially important species, has undergone a recent polewards range shift in the coastal waters of south-eastern Australia, thought to be associated with the southerly extension of the warm East Australian Current. At the cooler temperatures of a polewards distribution limit, growth of a species could be slower, potentially leading to a bigger body size and resulting in a slower population turnover, affecting population viability at the extreme of the distribution. Growth rates, body size, and life span of O. tetricus were examined at the leading edge of a polewards range shift in Tasmanian waters (40°S and 147°E) throughout 2011. Octopus tetricus had a relatively small body size and short lifespan of approximately 11 months that, despite cooler temperatures, would allow a high rate of population turnover and may facilitate the population increase necessary for successful establishment in the new extended area of the range. Temperature, food availability and gender appear to influence growth rate. Individuals that hatched during cooler and more productive conditions, but grew during warming conditions, exhibited faster growth rates and reached smaller body sizes than individuals that hatched into warmer waters but grew during cooling conditions. This study suggests that fast growth, small body size and associated rapid population turnover may facilitate the range shift of O. tetricus into Tasmanian waters.     

Mucosal layers and related nerve fibres in non-chagasic and chagasic human colon—a quantitative immunohistochemical study

Chagasic megacolon is accompanied by extensive myenteric and, simultaneously, moderate submucosal neuron loss. Here, we examined changes of the innervation pattern of the lamina propria (LP) and muscularis mucosae (MM). Two alternating sets of cryosections were taken from seven non-chagasic colonic and seven chagasic megacolonic specimens (the latter included both the dilated megacolonic and the non-dilated transitional oral and anal zones) and were immunohistochemically triple-stained for smooth-muscle actin (SMA), synaptophysin (SYN) and glial acid protein S100 and, alternatively, for SMA, vasoactive intestinal peptide (VIP) and somatostatin (SOM). Subsequent image analysis and statistical evaluation of nervous tissue profile areas revealed that, in LP, the most extreme differences (i.e. increase in thickness or decrease in nerve, glia and muscle tissue profile area, respectively) compared with control values occurred in the dilated megacolonic zone itself. In contrast, the most extreme differences in the MM were in the anal-to-megacolonic zone (except the profile area of muscle tissue, which was lowest in the megacolonic zone). This parallels our previous results in the external muscle coat. A partial and selective survival of VIP-immunoreactive in contrast to SOM-immunoreactive nerve fibres was observed in both mucosal layers investigated. Thus, VIPergic nerve elements might be crucial for the maintenance of the mucosal barrier. The differential changes of neural tissue parameters in LP and MM might reflect a multifactorial rather than a pure neurogenic development of megacolon in chronic Chagas’ disease.