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PubMed2003

Conformational transitions and aggregation in poly(dA)-poly(dT) system induced by Na+ and Mg2+ ions.

Effects of Mg(2+) ions on thermally induced conformational transitions in the synthetic poly(dA).poly(dT) and poly(dA).2poly(dT) were studied in the buffered solutions (pH 6.9), containing 0.1 or 1M NaCl at polynucleotide concentration of 0.1-0.3mM (in nucleic bases). The experiments consist of measurements of the UV absorption and intensity of conventional visible static light scattering. The diagram of conformational transitions in the poly(dA)-poly(dT)-Mg(2+) system was constructed on a basis of experimental data obtained. Anomalously strong light scattering, like critical opalescence, has been revealed at 0.1M NaCl and [Mg(2+)]>/=20mM in the melting range of both polynucleotides, which eventually disappeared after the completion of polymer strands separation. The effect presumably is caused by a fluctuation process of polymer strands complexing which arises at a certain concentration of Mg(2+) ions.

Ions↗
PubMed2002

Centromere proteins Cenpa, Cenpb, and Bub3 interact with poly(ADP-ribose) polymerase-1 protein and are poly(ADP-ribosyl)ated.

Poly(ADP-ribose) polymerase-1 (PARP-1) is activated by DNA strand breaks during cellular genotoxic stress response and catalyzes poly(ADP-ribosyl)ation of acceptor proteins. These acceptor proteins include those involved in modulation of chromatin structure, DNA synthesis, DNA repair, transcription, and cell cycle control. Thus, PARP-1 is believed to play a pivotal role in maintaining genome integrity through modulation of protein-protein and protein-DNA interactions. We previously described the association of PARP-1 with normal mammalian centromeres and human neocentromeres by affinity purification and immunofluorescence. Here we investigated the interaction of this protein with, and poly(ADP-ribosyl)ation of, three constitutive centromere proteins, Cenpa, Cenpb, and Cenpc, and a spindle checkpoint protein, Bub3. Immunoprecipitation and Western blot analyses demonstrate that Cenpa, Cenpb, and Bub3, but not Cenpc, interacted with PARP-1, and are poly(ADP-ribosyl)ated following induction of DNA damage. The results suggest a role of PARP-1 in centromere assembly/disassembly and checkpoint control. Demonstration of PARP-1-binding and poly(ADP-ribosyl)ation in three of the four proteins tested further suggests that many more centromere proteins may behave similarly and implicates PARP-1 as an important regulator of diverse centromere function.

Amino Acid Motifs↗
PubMed1998

High speed separation of DNA fragments by capillary electrophoresis in poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock polymer.

The high speed separation of DNA fragments by using a triblock copolymer, 25% w/v F127 (PEO99PPO69PEO99 with PEO and PPO denoting polyethylene oxide and polypropylene oxide, respectively) which is easy to handle and does not need coating of the quartz capillary, has been investigated. Two ways to decrease the run time are presented: one is to shorten the effective capillary length and the other to increase the electric field strength. In a short capillary, the sieving ability of the separation medium versus the initial band width, and the band width spreading as a function of distance traveled dominate the resolution; at high electric field strength, Joule heating could deteriorate the separation. By taking both effects into account, the phi X174/HaeIII digest could be separated within 100 s by using an 8 mm effective length, 50 microns diameter capillary operating at 300 V/cm.

Bacteriophage phi X 174↗
PubMed1997

Temperature Study of Sound Velocity and Volume-Related Specific Thermodynamic Properties of Aqueous Solutions of Poly(ethylene oxide)-Poly(propylene oxide) -Poly (ethylene oxide) Triblock Copolymers.

A comprehensive study of sound velocity and apparent specific volume, and adiabatic compressibility and expansibility thermodynamic properties of aqueous solutions of a number of POE-POP-POE triblock copolymers has been carried out in the temperature range 10-45 degreesC. Three series of the above block copolymers were studied: one having similar relative molar masses but different POP/POE mass ratios (F38, P103, P85); another having the same POP/POE mass ratio but different relative molar masses (L64, P84, P104 and F38, F68, F108); and a series in which the copolymers have the same absolute POP content but different relative molar masses (P103, P104, P108). An abrupt transition in the temperature dependence of the volumetric and sound velocity properties occurs in the temperature range 10-45 degreesC for many of the copolymers. This is due to the self-aggregation of the copolymers. The results of this study show that the relative molar mass, POP/POE mass ratio and POP content of the copolymers are factors that play a role in the self-aggregation of these systems. The extensive study of the sound velocity property of these systems extends and confirms the few previous reports that it is a sensitive macroscopic probe of the onset of self-aggregation processes in these systems. The apparent specific volume data of the copolymers has been used to test current models of these aggregates. The results show that the POP core contains some water. Copyright 1997 Academic Press.

Journal Article↗