Artificial dimers of native actin: Preparation and properties in biological functions

With the aid of tartryl-bis--aminocaprylazide artificial dimers were produced from F actin from rabbit striated muscle. These derivatives will not polymerize by themselves but are able to copolymerize fully with native G actin. By modification of a single side chain per dimer, this copolymerization was completely inhibited. The dimers are able to activate subfragment I ATPase of myosin and bind to DNase I with inactivation of the enzyme in the same manner as native G actin. Within the dimer, one ADP is immobilized and will exchange against ATP extremely slowly. The dimers do not bind to the mushroom toxin phalloidin.     

Fanconi's anaemia: correlation of genetic complementation group with psoralen/UVA response

Summary The correlation found by Moustacchi (1987) between cellular response to a crosslinking challenge and genetic heterogeneity in Fanconi's anaemia is confirmed for an earlier set of complementation groups (Zakrzewski and Sperling 1980). This allows the matching of the two independently established complementation groupings and better characterization of their DNA repair-related biochemical properties.     

Two auditory filter systems determine the calling behavior of the fire-bellied toad: a behavioral and neurophysiological characterization

Summary Male fire-bellied toads,Bombina bombina, are stimulated into calling by conspecific mating calls. They tend to synchronize their activity with other calling individuals, which leads to antiphonal calling. Behavioral physiological experiments revealed the existence of two different auditory filter systems which influence this acoustic behavior. One filter system is tuned to the recognition of conspecific mating calls, the other is part of a circuit that controls an acoustic jamming avoidance reaction. The two filter systems differ in several properties: filter bandwidth, threshold, and time constant. Neurophysiological recordings in the midbrain and the thalamus show that the filter characteristics can be explained by the coding properties of auditory neurons in these two brain nuclei.     

Isolation of aClostridium thermocellum gene encoding a thermostable β-1, 3-glucanase (laminarinase)

Summary AClostridium thermocellum gene directing the synthesis of a thermostable -glucanase was localized on a 1.9-kb DNA fragment by subcloning intoEscherichia coli plasmid vectors. The enzyme was highly efficient in degrading glucans with alternating -1, 3- and -1,4-linkages such as lichenan and barley glucan. It was also active towards the -1, 3-glucan laminarin, but lacked activity on cellulosic substrates and -glucans. The enzyme was therefore classified as -1, 3-glucanase (laminarinase) and the corresponding gene was designatedlicA. With barley -glucan as substrate the enzyme had a pH optimum around pH 6.5 and a temperature optimum at 65°C. It was stable for several hours at 60°C in the absence of substrate.     

Structure and function of ferredoxin-NADP+-oxidoreductase

The redox-enzyme ferredoxin-NADP-oxidoreductase has been shown to be activated by light and inactivated in the dark. This review will summarize recent data concerning the biochemical characterization of the enzyme compared to its in-vivo activation. Further-more the mechanism of this activation process is discussed as a conformational change caused by the light-driven proton gradient.Abbreviations cyt cytochrome - fd ferredoxin - FNR1 large form of ferredoxin-NADP-oxidoreductase - FNRox oxidized FNR - FNRred reduced FNR - FNRs small form of FNR - FNRsq FNR-semiquinone     

Recovery of metals from acid waste water by Cyanidium caldarium

Summary Cyanidium caldarium grows in acid water obtained from a bacterial leaching procedure and the alga is capable of precipitating metals from the solution. This study demonstrates that changes in culture and oxidation-reduction conditions may result in a different bioaccumulation of metals.     

Partial purification and characterization of a cellular protein that binds to the SV40 core origin of DNA replication

A monkey cell factor that interacts specifically with double- and single-stranded DNA sequences in the early domain of the simian virus 40 (SV40) core origin of replication was identified using gel-retention assays. The protein was enriched over 1200-fold using ion-exchange and affinity chromatography on single-strand DNA cellulose. Binding of protein to mutant origin DNA restriction fragments was correlated with replication activity of the mutant DNAs. Exonuclease footprint experiments on single-stranded DNA revealed prominent pause sites in the early domain of the core origin. The results suggest that this cellular protein may be involved in SV40 DNA replication.     

Orientation of Dunnocks (Prunella modularis) at Sunset

To find out the relative importance of the geomagnetic and solar cues for the orientation at the time of sunset, dunnocks were tested outdoors during the spring migration periods of 1982 and 1983. Experimental magnetic fields were produced by Helmholtz coils. In the various magnetic conditions, the following results were obtained:

• 1 In the local geomagnetic field, the dunnocks oriented in a seasonally appropriate northerly direction.
• 2 In a magnetic field the north of which was shifted 120° clock-wise to ESE, the birds showed a corresponding shift in their orientation.
• 3 In a vertical magnetic field without meaningful directional information, birds previously tested in either the local geomagnetic field or the shifted magnetic field now displayed axially bimodal orientation, with the axes of the two groups differing.

These findings indicate that for migratory dunnocks, the magnetic field plays a dominant role in determining their orientation at the time of sunset, and that magnetic information may affect the dunnocks' response to other directional, presumably solar cues as well.