Dialysis of small samples in agarose gels

Isolation and characterization of microsatellites in the lichen Buellia frigida (Physciaceae), an Antarctic endemic

PREMISE OF THE STUDY

Microsatellite markers were characterized for an Antarctic endemic, Buellia frigida, to investigate population structure and origin of Antarctic lichens.

METHODS AND RESULTS

Five primer sets were characterized. All loci were polymorphic with eight to 16 alleles per locus in a sample of 59 lichens.

CONCLUSIONS

The microsatellite markers potentially provide insight into population structure and gene flow of B. frigida.

Remarkable stability of the proton translocating F1FO-ATP synthase from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1

For functional characterization, we isolated the F1FO-ATP synthase of the thermophilic cyanobacterium Thermosynechococcus elongatus. Because of the high content of phycobilisomes, a combination of dye-ligand chromatography and anion exchange chromatography was necessary to yield highly pure ATP synthase. All nine single F1FO subunits were identified by mass spectrometry. Western blotting revealed the SDS stable oligomer of subunits c in T. elongatus. In contrast to the mass archived in the database (10,141 Da), MALDI-TOF-MS revealed a mass of the subunit c monomer of only 8238 Da. A notable feature of the ATP synthase was its ability to synthesize ATP in a wide temperature range and its stability against chaotropic reagents. After reconstitution of F1FO into liposomes, ATP synthesis energized by an applied electrochemical proton gradient demonstrated functional integrity. The highest ATP synthesis rate was determined at the natural growth temperature of 55 degrees C, but even at 95 degrees C ATP production occurred. In contrast to other prokaryotic and eukaryotic ATP synthases which can be disassembled with Coomassie dye into the membrane integral and the hydrophilic part, the F1FO-ATP synthase possessed a particular stability. Also with the chaotropic reagents sodium bromide and guanidine thiocyanate, significantly harsher conditions were required for disassembly of the thermophilic ATP synthase.

About the specificity of photoinduced affinity labeling of Escherichia coli ribosomes by dihydrorosaramicin, a macrolide related to erythromycin

Photoactivation of the [3H]dihydrorosaramicin chromophore at a wavelength above 300 nm allows the covalent attachment of the macrolide antibiotic to the bacterial ribosome. Bidimensional electrophoresis shows that the radioactivity is mainly associated with proteins L1, L5, L6, L15, L18, L19, S1, S3, S4, S5 and S9. When photoincorporation of the drug is conducted in the presence of puromycin as effector of [3H]dihydrorosaramicin-binding sites, a decrease in the labeling of most proteins is observed, except for L18 and L19, which are radiolabeled to a larger extent. These results allow us to speculate that L18 and L19 belong to the high-affinity binding site of rosaramicin antibiotic.

The development of a microimmunoadsorbent assay and a microdialysis method for the evaluation of immunoadsorbent efficiency and antibody quantitation

A microimmunoadsorbent assay which provides for the quantitative elution and recovery of active antibody from immunoaffinity columns has been developed. We have also designed a microdialysis chamber which permits the dialysis of sample volumes from 50 to 500 microliters and allows quantitative recovery of macromolecular compounds. These techniques permit the rapid evaluation of a large number of eluants and immunoadsorbents in a short period of time. The microimmunoadsorbent assay coupled with the microdialysis method has been used to evaluate the efficacy of different anti-isopentenyl adenosine immunoadsorbents under various elution conditions. In the present study the best eluants for immunoaffinity purification of anti-N6-(delta 2-isopentenyl)adenosine antibody contained 15% pyridine in a sodium phosphate buffer or 4 M imidazole-HCl at pH 10.0.

Site-specific analysis of drug interactions and damage in DNA using sequencing techniques

DNA-sequencing techniques can be adapted to provide powerful analytical tools for pinpointing the sites at which DNA is modified by either radiations or chemicals. Base modifications, covalent adducts, crosslinks, and noncovalent binding can all be detected. This review outlines the adaptions of the Maxam-Gilbert and Sanger dideoxy sequencing techniques which make such studies possible. Practical aspects and limitations of the various methods are given. Assays which test the ability of DNA polymerase to bypass damage and misincorporate bases are also discussed. It is concluded that these techniques constitute the most powerful method currently available for the study of sequence-specific DNA interactions.

Studies on the replication of Escherichia coli phage lambda DNA. I. The kinetics of DNA replication and requirements for the generation of rolling circles

Escherichia coli phage lambda DNA has been isolated from infected bacteria using a new technique by which virtually all phage DNA is recovered. Isolated DNA is examined by electron microscopy. Addition of phi X174 RF1 molecules as a counting standard enables us to determine the average number of lambda DNA molecules present in an infected cell. In this study, we have followed the kinetics of lambda DNA replication and examined rolling circle replication. The most important findings are the following: (1) Rolling circle replication is initiated at roughly the same time as is theta replication, indicating that the rolling circle is not solely a late-replicating form. (2) theta replication stops at about 16 min after infection. (3) Early in infection the number of DNA molecules per cell doubles every 2-3 min until theta replication stops, at which point most DNA synthesis consists of growth of the tails of about three rolling circles per cell. (4) Neither the timing of rolling circle replication nor the number of molecules is affected by the activity of the lambda red genes. (5). The red genes are responsible for the production of oligomeric circles late in infection.