Charge separation and recombination dynamics in Sn/Pb cocktail perovskite solar cells were clarified.

Norfloxacin (NFLX) caused induction of prophages VT1 and VT2 of enterohemorrhagic Escherichia coli O157 at subinhibitory concentrations. In time course experiments, we observed the following sequential events: upon induction, the phage genomes underwent multiplication; the amount of stx genes increased; and subsequently, large quantities of toxins VT1 and VT2 were produced. Further studies showed that the molecular mechanism of prophage induction is closely related to the RecA system since the prophage VT2 was not induced with NFLX in a recA mutant strain.

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The DNA-dependent protein kinase (DNA-PK) is a trimeric enzyme consisting of a 460-kDa catalytic subunit (DNA-PKcs) and a heterodimeric regulatory complex called Ku, which is comprised of 70 (Ku70) and 86 (Ku80) kDa subunits. Mutations that affect the expression of the catalytic or Ku80 subunits of DNA-PK disrupt both V(D)J recombination and DNA double-stranded break repair pathways. In this report, we show that two previously uncharacterized rodent cell lines that are defective in DNA double-stranded break repair express catalytically inactive DNA-PK. The DNA-PKcs from the DNA double-stranded break repair mutant cell lines IRS-20 and SX-9 assembles on double-stranded DNA but fails to function as a protein kinase. In addition to the kinase defect, the abundance of the DNA-PKcs from both of these cell lines is reduced relative to wild-type controls. These results suggest that the DNA-PKcs gene from each of these cell lines contains mutations that inactivate the enzymatic activity and the expression or stability of the gene product. These data further strengthen the hypothesis that DNA-PK-mediated protein phosphorylation is a necessary component of the DNA double-stranded break repair pathway.The rejoining of double-stranded DNA breaks induced by ionizing radiation or occurring as intermediates of V(D)J recombination is performed via a biochemical pathway that includes the DNA-dependent protein kinase holoenzyme. DNA-PK 1 is a trimeric complex consisting of a DNA-binding component made up of the 70 and 86 kd subunits of the Ku autoantigen (1, 2) and a catalytic subunit of approximately 460 kDa (3). Cells from the x-ray-sensitive complementation group (xrs)-7, which includes the severe combined immunodeficiency (scid) mouse and the Chinese hamster ovary (CHO) V3 cell line, exhibit reduced expression of the DNA-PKcs, lack measurable DNA-stimulated kinase activity, and are defective for DNA double-stranded break repair and V(D)J recombination (4 -6). Similarly, cells from the xrs-6 complementation group, which contain mutations that reduce the expression of the Ku80 subunit of DNA-PK, exhibit losses of Ku-specific DNA-ending binding activity (7-9) DNA-PK kinase activity (10) and are also defective for DNA double-stranded break repair and V(D)J recombination (11-13).Molecular analysis of these DNA-repair mutant cells indicates that DNA-PK is required for the rejoining of doublestranded DNA breaks, but the mechanism by which DNA-PK functions in this process has yet to be elucidated. DNA-PK is a serine and threonine protein kinase that is activated by doublestranded DNA containing single-stranded to double-stranded transitions, such as DNA-ends, nicks, gaps, and stem-loop structures (14). In vitro, the Ku and catalytic subunits of DNA-PK assemble in a DNA-dependent manner (15), and the DNA-bound holoenzyme preferentially phosphorylates substrates that are bound to the same DNA molecule (1, 16). DNA-PK has been shown to phosphorylate a broad range of proteins in vitro, most of which are DNA-binding proteins (17), includi...

The acid sites associated with the external surface of zeolite particles are responsible for undesirable consecutive reactions, such as isomerization, alkylation, and oligomerization, resulting in a lower selectivity to a target product; therefore, the selective modification (deactivation) of the external surface of zeolite particles has been an important issue in zeolite science. Here, a new method for surface deactivation of zeolite catalyst was tested via a mechanochemical approach using powder composer. Postsynthetic mechanochemical treatment of ZSM-5 zeolite causes a selective deactivation of catalytically active sites existing only on the external surface, as a potentially useful catalyst for highly selective production of p-xylene.

In enterohemorrhagic Escherichia coli, Shiga toxin is produced by lysogenic prophages. We have isolated the prophage VT2-Sa that is responsible for production of Shiga toxin type 2 protein, and determined the complete nucleotide sequence of this phage DNA. The entire DNA sequence consisted of 60,942 bp, exhibiting marked similarity to the 933W phage genome. However, several differences were observed in the immunity and replication regions, where cI, cII, cIII, N, cro, O, and P genes were present: Predicted amino acid sequences of N, cI, cro, O and P in the VT2-Sa genome did not show significant similarity to the counterparts of the 933W genome; however its cI showed higher similarity to lambda. Furthermore, O and P closely resembled those of phage HK022. These observations suggest that the various degrees of homology observed in the immunity and replication regions of VT2-Sa could have resulted from frequent recombination events among the lambdoid phages, and that these regions play a key role as a functional unit for phage propagation in competition with other lambdoid phages.

Zeolites with high external surface area allow diffusing reactants greater access to catalytically active sites, which has lead to interest in the preparation of nano-zeolites. In this study, a top-down approach has been used, first milling the zeolite to produce a fine powder. This technique can cause destruction of the outer portion of the zeolite framework, which deactivates the catalyst. To remedy this, the damaged part was removed using an alkaline solution after bead milling treatment. As a result, the designed zeolite powder yielded almost twice the amount of benzene compared with the raw zeolite when cumene was cracking into benzene and propylene.

The presence of selectable genetic markers in long-term human lymphoblast cultures would facilitate cell hybridization experiments on the biosynthesis of immunoglobulins, as well as other studies. This work reports the induction with ethylmethane sulfonate of 6-thioguanine -resistant, phosphoribosyltransferase -deficient mutants in a lymphoblast line from a patient with infectious mononucleosis. These cells were unusually sensitive, with a Do value of 28 sg of ethylmethane sulfonate per ml; the sensitivity curve followed a biphasic pattern suggesting the presence of 3% resistant cells. Ethylmethane sulfonate increased the frequency of mutants resistant to 6-thioguanine over 100-fold, to about 2 X 10-4; nitrosoguanidine was less effective. Almost all the mutants contained considerably less than 1% of the hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) activity of wild-type cells. The mutation did not appear to result from loss of an X chromosome.