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Repair of DNA double-strand breaks by the non-homologous end-joining pathway is initiated by the binding of Ku to DNA ends. Multiple Ku proteins load onto linear DNAs in vitro. However, in cells, Ku loading is limited to ∼1–2 molecules per DNA end. The mechanisms enforcing this limit are currently unclear. Here, we show that the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs), but not its protein kinase activity, is required to prevent excessive Ku entry into chromatin. Ku accumulation is further restricted by two mechanisms: a neddylation/FBXL12-dependent process that actively removes loaded Ku molecules throughout the cell cycle and a CtIP/ATM-dependent mechanism that operates in S phase. Finally, we demonstrate that the misregulation of Ku loading leads to impaired transcription in the vicinity of DNA ends. Together, our data shed light on the multiple mechanisms operating to prevent Ku from invading chromatin and interfering with other DNA transactions.

The Ku70–Ku80 (Ku) heterodimer binds rapidly and tightly to the ends of DNA double-strand breaks and recruits factors of the non-homologous end-joining (NHEJ) repair pathway through molecular interactions that remain unclear. We have determined crystal structures of the Ku-binding motifs (KBM) of the NHEJ proteins APLF (A-KBM) and XLF (X-KBM) bound to a Ku–DNA complex. The two KBM motifs bind remote sites of the Ku80 α/β domain. The X-KBM occupies an internal pocket formed by an unprecedented large outward rotation of the Ku80 α/β domain. We observe independent recruitment of the APLF-interacting protein XRCC4 and of XLF to laser-irradiated sites via binding of A- and X-KBMs, respectively, to Ku80. Finally, we show that mutation of the X-KBM and A-KBM binding sites in Ku80 compromises both the efficiency and accuracy of end joining and cellular radiosensitivity. A- and X-KBMs may represent two initial anchor points to build the intricate interaction network required for NHEJ.

Nicotinium Nitrate Monohydrate (NNM) was grown by slow evaporation method. The arrangment of the molecules and hydrogen bonding intractionsin the grown crystal were analyzed using single crystal XRD. The structure, functional groups (vibrational analysis) and electronic properties (Mulliken and HOMO-LUMO analysis) were calculated by the density functional theory (DFT)/B3LYP/wB97XD method using 6–311++G(d,p) basis set. Also, the binding energy and the effect of basis set superposition error (BSSE) on the ring motifs have been investigated. The intermolecular interactions and charge delocalization density of NNM crystal have been analyzed using NBO 3.1 program. The strength of intermolecular interaction was further analyzed by 3D Hirshfeld surface analysis using fingerprint plot. Improved solubility of the title crystal NNM shows an enhanced physio-chemical activity compared to pure vitamin B3 (Nicotinic acid). The antibacterial activity of NNM crystal increased against Staphylococcus aureusa gram-positive bacteria when compared with pure nicotinic acid.

In order to confirm the vibrational assignments, the density functional hypothesis has been used for 6-amino-3-bromo-2-methylpyridine (6A3B2MP). The entire energy distribution is used to materialize the several vibrational modes of 6A3B2MP (TED). The DFT/B3LYP approach is used to examine the molecular optimum limits and electronic characteristics of 6A3B2MP. Investigations have been made into the molecular orbital, Fukui function analysis, natural bond orbital (NBO), and molecular electrostatic potential (MEP) characteristics of 6A3B2MP. Theoretical studies have focused on the UV–vis spectra with different solvents. According to the outcomes of the molecular docking technique, the 6A3B2MP is docked with two target proteins, which is crucial for the emergence of cancer. Therefore, this research paves the door for the development of medicines that are specially formulated.

Stable sols or gels with SrBi2Nb2O9composition were obtained from mixtures of niobium ethoxide, bismuth and strontium 2-ethylhexanoates. SrBi2Nb2O9thin films were prepared by spin-coating a stable precursor solution on Si/SiO2/TiO2/Pt substrates. Randomly oriented 0.3 µm-thick crack-free films were obtained after 10 successive depositions and an heat-treatment of 2 hours at 700°C. Crystallisation occurs at about 550 °C and a pure SrBi2NB2O9phase is obtained at 600°C. P-E hysteresis loops have confirmed the ferroelectric behaviour of the films : they show a remanent polarisation of 2.5 µC/cm2. No fatigue was observed up to 109full switching.

Aiming to identify novel phosphorylation sites in response to DNA double-strand breaks (DSB) inducers, we have isolated a phosphorylation site on KU70. Unexpectedly, a rabbit antiserum raised against this site cross-reacted with a 120 kDa protein in cells treated by DNA DSB inducers. We identified this protein as SAF-A/hnRNP U, an abundant and essential nuclear protein containing regions binding DNA or RNA. The phosphorylation site was mapped at S59 position in a sequence context favoring a "S-hydrophobic" consensus model for DNA-PK phosphorylation site in vivo. This site was exclusively phosphorylated by DNA-PK in response to DNA DSB inducers. In addition, the extent and duration of this phosphorylation was in inverse correlation with the capacity of the cells to repair DSB by nonhomologous end joining. These results bring a new link between the hnRNP family and the DNA damage response. Additionaly, the mapped phospho-site on SAF-A might serve as a potential bio-marker for DNA-PK activity in academic studies and clinical analyses of DNA-PK activators or inhibitors.

Care planning was an integral part of the SA HealthPlus Coordinated Care trial. This paper reports on the usefulness of care planning as a reminder system to GPs and patients in ensuring that chronically ill patients received planned services. Two thousand and seventy one (2071) intervention patients and 1317 control patients were eligible for the study. Data were collected from all sources recording the delivery of medical services, and the percentage of intervention and control patients receiving the service was compared. Two planned services - lipids tests and bowel cancer screening - were used in the analyses. A higher percentage of intervention patients than control patients received the lipid test and the bowel cancer screening test. Care planning has proved a useful means of increasing the delivery of at least two best practice services to a needy group of people with chronic illnesses.

Association of the DNA end-binding Ku70/Ku80 heterodimer with the 460-kDa serine/threonine kinase catalytic subunit forms the DNA-dependent protein kinase (DNA-PK) that is required for double-strand break repair by non-homologous recombination in mammalian cells. Recently, we have proposed a model in which the kinase activity is required for translocation of the DNA end-binding subunit Ku along the DNA helix when DNA-PK assembles on DNA ends. Here, we have questioned the consequences of Ku entry into DNA on local DNA processes by using human nuclear cell extracts incubated in the presence of linearized plasmid DNA. As two model processes, we have chosen nucleotide excision repair (NER) of UVC DNA lesions and transcription from viral promoters. We show that although NER efficiency is strongly reduced on linear DNA, it can be fully restored in the presence of DNA-PK inhibitors. Simultaneously, the amount of NER proteins bound to the UVC-damaged linear DNA is increased and the amount of Ku bound to the same DNA molecules is decreased. Similarly, the poor transcription efficiency exhibited by viral promoters on linear DNA is enhanced in the presence of DNA-PK inhibitor concentrations that prevent Ku entry into the DNA substrate molecule. The present results show that DNA-PK catalytic activity can regulate DNA transactions including transcription in the vicinity of double-strand breaks by controlling Ku entry into DNA.

The joint lattice-dynamical model study of the vibrational and elastic properties of paratellurite (α-TeO2) and tellurite (β-TeO2) has been conducted. Emphasis was laid on the crystal chemistry aspects of Raman spectra of these lattices. Results were used to interpret the Raman spectra of two new polymorphs (γ and δ) of tellurium dioxide, and to clarify their relationships with the spectrum of pure TeO2glass.

cis-Dichlorodiammineplatinum(II) (CDDP; cisplatin) is commonly used in combination with ionizing radiation (IR) in the treatment of various malignancies. In vitro, many observations suggest that acquisition of CDDP resistance in cell lines confers cross-resistance to IR, but the molecular mechanisms involved have not been well documented yet. We report here the selection and characterization of a murine CDDP-resistant L1210 cell line (L1210/3R) that exhibits cross-resistance to IR because of an increased capacity to repair double-strand breaks compared with parental cells (L1210/P). In resistant cells, electrophoretic mobility shift assays revealed an increased DNA-end binding activity that could be ascribed, by supershifting the retardation complexes with antibodies, to the autoantigen Ku. The heterodimeric Ku protein, composed of 86-kDa (Ku80) and 70-kDa (Ku70) subunits, is the DNA-targeting component of DNA-dependent protein kinase (DNA-PK), which plays a critical role in mammalian DNA double-strand breaks repair. The increased Ku-binding activity in resistant cells was associated with an overexpression affecting specifically the Ku80 subunit. These data strongly suggest that the increase in Ku activity is responsible for the phenotype of cross-resistance to IR. In addition, these observations, along with previous results from DNA-PK- mutant cells, provide evidence in favor of a role of Ku/DNA-PK in resistance to CDDP. These results suggest that Ku activity may be an important molecular target in cancer therapy at the crossroad between cellular responses to CDDP and IR.

The large nonstoichiometric domain, observed in the La4Ti3O12-rich part of the La4Ti3O12–BaTiO3system, has been shown to correspond to a continuous series of cation-deficient perovskite-related (Ba,La)nTin−δO3n(n≥4δ) microphases. The crystal structures of these microphases have been analyzed by electron diffraction and high-resolution electron microscopy. They can be described as coherent intergrowths of P-perovskite-like blocks La4Ti3O12and Q-perovskite-like blocks BaLa4Ti4O15, respectively, constitutive of the simple basic terms n=4 and n=5 of the previously identified (Ba,La)nTin−1O3nseries. The corresponding BaQLa4(P+Q)Ti3P+4QO12P+15Qmicrophases can thus be denoted by 4P5Qin a compact form. In fact, only the 4P51intergrowth sequences have been observed. Eight of these are clearly shown by direct imaging. No intergrowth terms were observed for compositions ranging from BaLa4Ti4O15(n=5) to Ba2La4Ti5O18(n=6). The ability of the system to develop coherent intergrowths has been discussed in the light of information provided by an accurate analysis of crystal structures of the basic members of the series: La4Ti3O12(n=4), BaLa4Ti4O15(n=5), and Ba2La4Ti5O18(n=6).

We have previously reported that the incision efficiency of the nucleotide excision repair (NER) reaction measured in vitro with cell-free human protein extracts was reduced by up to 80% on a linearized damaged plasmid DNA substrate when compared to supercoiled damaged DNA. The inhibition stemed from the presence of the DNA-end binding Ku70/Ku80 heterodimer which is the regulatory subunit of the DNA-dependent protein kinase (DNA-PK). Here, the origin of the repair inhibition was assessed by a new in vitro assay in which circular or linear plasmid DNA, damaged or undamaged, was quantitatively adsorbed on sensitized microplate wells. The binding of two NER proteins, XPA and p62-TFIIH, indispensable for the incision step of the reaction, was quantified either directly in an ELISA-like reaction in the wells with specific antibodies or in Western blotting experiments on the DNA-bound fraction. We report a dramatic inhibition of XPA and p62-TFIIH association with UVC photoproducts on linear DNA. XPA and p62-TFIIH binding to DNA damage was regained when the reaction was performed with extracts lacking Ku activity (extracts from xrs6 rodent cells) whereas addition of purified human Ku complex to these extracts restored the inhibition. Despite the fact that DNA-PK was active during the NER reaction, the mechanism of inhibition relied on the sole Ku complex, since mutant protein extracts lacking the catalytic DNA-PK subunit (extracts from the human M059J glioma cells) exhibited a strong binding inhibition of XPA and p62-TFIIH proteins on linear damaged DNA, identical to the inhibition observed with the DNA-PK+ control extracts (from M059K cells).

The relationships between structure and nonlinear optical response at 1.5 μm in thallium(I) tellurite glasses are investigated. Usually in tellurite glasses, the introduction of a modifier ion changes the basic structural TeO4disphenoid entity progressively into a TeO3trigonal bipyramid via an intermediate TeO3+1polyhedron. This evolution leads to a decrease of the nonlinear refractive index n2. Nevertheless, if a modifier ion such as Tl+also has an ns2lone electron pair, n2increases although the same structural evolution is observed around the tellurium atoms. This result is related to the hyperpolarizability of the thallium oxygen entities, which has been evidenced by the structural study of both thallium(I) tellurite crystals and glasses of the same compositions. With this solid state chemistry approach, the highest non-linear refractive index measured at 1.5 μm (n2=9.10−19m2/W) and reported in oxide glasses has been obtained.

The DNA-dependent protein kinase (DNA-PK) is required for double-strand break repair in mammalian cells. DNA-PK contains the heterodimer Ku and a 460-kDa serine/threonine kinase catalytic subunit (p460). Ku binds in vitro to DNA termini or other discontinuities in the DNA helix and is able to enter the DNA molecule by an ATP-independent process. It is clear from in vitro experiments that Ku stimulates the recruitment to DNA of p460 and activates the kinase activity toward DNA-binding protein substrates in the vicinity. Here, we have examined in human nuclear cell extracts the influence of the kinase catalytic activity on Ku binding to DNA. We demonstrate that, although Ku can enter DNA from free ends in the absence of p460 subunit, the kinase activity is required for Ku translocation along the DNA helix when the whole Ku/p460 assembles on DNA termini. When the kinase activity is impaired, DNA-PK including Ku and p460 is blocked at DNA ends and prevents their processing by either DNA polymerization, degradation, or ligation. The control of Ku entry into DNA by DNA-PK catalytic activity potentially represents an important regulation of DNA transactions at DNA termini.

The TeO2-rich part of the TeO2-Nb2O5 system has been investigated by temperature programmed X-ray diffraction and differential scanning calorimetry. Three invariant equilibria have been observed: one eutectic reaction (8 mol% NbO2.5, TE=690±5 °C, LE TeO2+Nb2Te4O13), one peritectic reaction (incongruent melting, at 766±5 °C, of the Nb2Te4O13 compound) and one congruent melting reaction (congruent melting, at 810±5 °C, of the Nb2Te3O11 compound). A large glass-forming domain has been evidenced (0 to 25 mol% NbO2.5). The thermal behaviour of these glasses has been followed. The glass transition, crystallization temperatures and the nature of crystalline phases formed have been determined.

The crystal structure of Bi2W2O9 has been solved by single crystal X-ray diffraction data analysis and refined to R=0.046 for 991 independent reflections. Bi2W2O9 crystallizes with orthorhombic symmetry, Pna21 space group, Z=4, a=5.440(1), b=5.413(1), c=23.740(5) Å. The model previously proposed by Watanabe et al., i.e. Bi2O2 layers interleaved with ReO3-like slabs of W2O7, has been confirmed. The distortion of the W2O7 octahedral network has been analysed and compared to that observed in homologous Aurivillius phases.

A structural study of a potassium-substituted cordierite with K0.5Mg2Al4.5Si4.5O18 formula was performed between 20 and 825° C using a time-of-flight powder neutron diffraction technique, on sintered samples obtained by glass crystallization. The thermal evolution of this compound is essentially of the same nature as for pure hexagonal cordierite, but is very dependent on the presence of potassium atoms within the channels. The very low value of the thermal expansion coefficient ( between 20 and 825° C) results from an opposite evolution of thea andc lattice parameters which may be explained in terms of a reorganization and a regularization of (Al, Si)O4 and MgO6 polyhedra. It strongly depends on the Al/Si ordering degree.

The crystal structure of the rhombohedral (R3̄m) Bi0.75Sr0.25O1.375phase has been determined at room and high temperature using single crystal neutron diffraction. It can be described at all temperatures as the regular repetition of three fluorite-like sheets shifted with respect to one another by a vector μ = 2 (a/3 + b/3 + c/3) and thus separated by an intersheet space free of anions. Interstitial anions partially occupy delocalized sites in the vicinity of the unsubstituted interface Bi-layers and are responsible for the high ionic conductivity of this phase. They are mainly located on the fluorite-like sheet side of this Bi-layer at room temperature. At high temperature, they partly migrate to the opposite side, i.e., the intersheet side, a phenomenon which results in the β2⇒ β1transition and a sudden increase of the conductivity. In light of these and previous results the different behavior of various alkaline earth-doped rhombehedral phases (Ca, Sr, Ba) and of the La-doped homologue is analyzed and rationalized.

Bi4Ti3O12thin films were obtained by the sol-gel method. The precursor solution was prepared by allowing the two metallic alkoxides, Bi(OC2H4OCH3)3and Ti(OC2H4OCH3)4, to react in 2-methoxy-ethanol to form the mixed alkoxide. This stable sol was deposited by spin-coating onto platinized silicon substrates. X-Ray diffraction patterns indicate that the perovskite initial crystallization temperature is 460°C for powder samples and it ranges between 400 and 500°C, for thin films, as a function of the number of coating layers. Dense, smooth and crack free thin films with grain sizes ranging from 20 nm to 500 nm are obtained, depending on the number of coating layers and on the post-deposition temperature annealing.

Three different precursor materials giving rise to contrasted nanostructures, xerogels, aerogels and precipitates, are prepared by a sol gel route in the Zrn-propoxide—acetylacetone—water—n-propanol system. Clear homogeneous gels are made by using a proper amount of acetylacetone and water. The gels are dried either by conventional processing (xerogels) or by supercritical evacuation of alcoholic solvent (aerogels). The complexation ratio (R= [acetylacetone]/[Zr(OR)4]) is the main parameter controlling the size of ZrO2primary particles. WhenR= 0 , precipitates are obtained. Xerogels, aerogels and precipitates are characterized and their textures are compared through small angle X-ray scattering measurements. The fractal structure of gels is destroyed by conventional drying and is preserved in aerogels. On the other hand precipitates are described as homogeneous agglomerates of very small primary units. The first crystallization steps are studied by transmission electron microscopy and X-ray diffraction experiments. The contribution of crystallite size and microstrain effects are investigated by Rietveld whole pattern fitting. The crystallization of precipitate powders starts at the agglomerate scale with large crystal like distorted lattices.

Te2O3F2crystallizes with the triclinic symmetry (space groupP-1) and the unit cell parametersa= 515.3(1) pm,b= 625.7(1) pm,c= 688.8(1) pm, α = 98.71(1)°, β = 110.31(1)°, γ = 92.72(1)°,Z= 2. Its structure was solved and refined toRvaluesR1= 0.024 and wR2= 0.059 on the basis of 699 independent reflections recorded on a single crystal with an automatic four-circle diffractometer. The two Te atoms are, respectively, fourfold and fivefold coordinated and their lone pairEis stereochemically active. The bond valence calculation shows a perfect O/F order. The Te(1)O3FEand Te(2)O4FEpolyhedra form, by sharing O–O edges, bipolyhedral units with a very short Te–Te distance (319 pm). These units, by sharing corners, constitute independent sheets parallel tox0y. All the F atoms are nonbridging and orientated, together with the lone pairsE, toward the interlayer space. The structural relationships with the α-TeO2structure have been evidenced and analyzed.

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A great number of anion-excess fluorite-related phases MX2+y correspond to ordered distributions, within a fluorite matrix, of the same M6X14 columnar cluster generated by the insertion at the centre of six primitive cubes MX8 of an extra zigzag row of anions. They can therefore be formulated as Mm+6X2m+14 (0 ≤ m < ∞) or more generally as Mm′X2m′+2 (m′ = m+6). It has been shown that, among all these structures, some, in which the clusters are systematically aligned and directly connected along rows perpendicular to the densified anion layers, are classical vernier structures formulated as MnX2n+1 (n = m′/2 = integer). Some are new vernier structures that can be called shifted vernier structures since the M6X14 clusters are shifted, from one densified plane to the other, by a vector →T = p(→aF + →bF)/2 (p = integer) and for which non-integer values of n are possible. Bi7O5F11 constitutes the first isolated member (n = 3.5, m' = 7) of this new structural series. Some others are completely different structures like the K2NbF7 compound.

Zusammenfassung: Fr dynamische Untersuchungen von Getrieben bentigt man die harmonische Analyse ihrer kinetischen Energie. Als Sonderfall der ebenen, viergliedrigen Kurbelgetriebe werden hier die Harmonischen der kinetischen Energie der exzentrischen Schubkurbel untersucht. Es zeigt sich, da die cos-Koeffizienten der kinetischen Energie von Koppel und Schubglied sich durch relativ einfache Ausdrcke wiedergeben lassen. Demgegenber knnen fr die sin-Koeffizienten der kinetischen Energie des Schubgliedes keine geschlossenen Ausdrcke angegeben werden. Aber dafr wird eine brauchbare Nherung entwickelt. Vier behandelte Beispiele zeigen die Abstufungen der Harmonischen (n=2, n=3, n=1). Die hheren Harmonischen sind vernachlssigbar klein.

The nonstoichiometric phase region occurring between Bi₂TeO₅ and Bi₂Te₂O₇ has been studied by electron microscopy and diffraction. The electron diffraction patterns are interpreted in terms of a shift lattice. The complexity of the phase region is defined by a constant value of the parameter ɛ equal to ⅔ and a smooth variation of the parameter β from 24.7 to 9.9 as both composition and temperature of preparation varied. The microstructures of the materials giving rise to these diffraction patterns are presented and discussed in terms of shift lattices, intergrowths, and modulated structures. Copyright 1995, 1999 Academic Press

The electrical properties of the BiPbO2F conductor were examined by means of impedance spectroscopy and de polarization techniques. Fluorine was shown to be the main mobile species. Crystal structure investigations were performed using X-ray single crystal and neutron powder diffractions. Cations are localized in the 2d site of the A−La2O3type structure while anions are distributed over the 1a, 2c, 6i and 6h positions of the P3ml space group. According to the fluorine location confirmed by a 19F NMR experiment, a fluorine migration mechanism is proposed.

Nucleotide excision repair (NER) was measured in human cell extracts incubated with either supercoiled or linearized damaged plasmid DNA as repair substrate. NER, as quantified by the extent of repair synthesis activity, was reduced by up to 80% in the case of linearized plasmid DNA when compared with supercoiled DNA. An excess of undamaged linearized plasmid in the repair mixture did not interfere with DNA repair synthesis activity on a supercoiled damaged plasmid, indicating a cis-acting inhibiting effect. In contrast, gaps on circular or linearized plasmids were filled in identically by the DNA polymerases operating in the extracts. When the extent of damage-dependent incision activity was measured, a approximately 70% reduction of repair incision activity by human cell extract was observed on linearized damaged plasmids. Recessed, protruding, or blunt ends were similarly inhibitory. NER activity was partly restored when the extracts were preincubated with autoimmune human sera containing antibodies against the nuclear DNA end-binding heterodimer Ku. In addition, the inhibition of repair activity on linear damaged plasmids was released in extracts from rodent cells deficient in Ku activity but not in extracts from murine scid cells devoid of Ku-associated DNA-dependent kinase activity.

Nucleotide excision repair (NER) was measured in human cell extracts incubated with either supercoiled or linearized damaged plasmid DNA as repair substrate. NER, as quantified by the extent of repair synthesis activity, was reduced by up to 80% in the case of linearized plasmid DNA when compared with supercoiled DNA. An excess of undamaged linearized plasmid in the repair mixture did not interfere with DNA repair synthesis activity on a supercoiled damaged plasmid, indicating a cis-acting inhibiting effect.

ABSTRACTDNA damage recognition by basal transcription factors follows different mechanisms. Using transcription-competition, nitrocellulose filter binding, and DNase I footprinting assays, we show that, although the general transcription factor TFIIH is able to target any kind of lesion which can be repaired by the nucleotide excision repair pathway, TATA binding protein (TBP)-TFIID is more selective in damage recognition. Only genotoxic agents which are able to induce kinked DNA structures similar to the one for the TATA box in its TBP complex are recognized. Indeed, DNase I footprinting patterns reveal that TBP protects equally 4 nucleotides upstream and 6 nucleotides downstream from the A-T (at position −29 of the noncoding strand) of the adenovirus major late promoter and from the G-G of a cisplatin-induced 1,2-d(GpG) cross-link. Together, our results may partially explain differences in transcription inhibition rates following DNA damage.

Incorporation of a low concentration of cetyltrimethylammonium bromide (CTAB) in the running electrolyte is shown to dynamically coat the silica capillary and to reverse the direction of electroosmotic flow. The CTAB coating prevented interaction of proteins with the capillary surface and enabled sharp peaks to be obtained in the electropherograms. A systematic study of experimental parameters demonstrated the importance of selecting a suitable buffer electrolyte and an appropriate pH. Excellent separations were obtained for five proteins, three enkephalins, and six dipeptides with an efficiency of approximately 500,000 theoretical plates per meter. The method developed is very simple to perform and was found to give excellent reproducibility.

Heating of NH₄BiF₄ at 285°C under dry ammonia yields Bi₃NF₆ via the intermediate products NH₄Bi₃F₁₀ and BiF₃. Bi₃NF₆ is an air-sensitive grey powder decomposing under dry NH₃ at 350°C to form Bi metal. It crystallizes in the orthorhombic space group Pbcm, with a = 581.74(2), b = 570.18(2), c = 1851.13(5) pm, Z = 4. The structure was determined by X-ray and neutron powder diffraction data. Bi₃NF₆ belongs to the family of vernier phases M_nX_2n+1, and represents the first member of the series with n = 3. The two-symmetry independent Bi atoms exhibit coordination numbers of eight. Copyright 1995, 1999 Academic Press

DNA-dependent protein kinase (DNA-PK), a member of the phosphatidyl-inositol (PI)3-kinase family, is involved in the repair of DNA double-strand breaks. Its regulatory subunit, Ku, binds to DNA and recruits the kinase catalytic subunit (DNA-PKcs). We show here a new role of DNA-PK in the modulation of the process of nucleotide excision repair (NER) in vivo since, as compared with their respective parental cell lines, DNA-PK mutants (scid , V-3 and xrs 6 cells) exhibit sensitivity to UV-C irradiation (2.0- to 2.5-fold) and cisplatin ( approximately 3- to 4-fold) associated with a decreased activity (40-55%) of unscheduled DNA synthesis after UV-C irradiation. Moreover, we observed that wortmannin sensitized parental cells in vivo when combined with either cisplatin or UV-C light, but had no effect on the DNA-PKcs deficient scid cells. Despite a lower repair synthesis activity (approximately 2-fold) measured in vitro with nuclear cell extracts from DNA-PK mutants, a direct involvement of DNA-PK in the NER reaction in vitro has not been observed. This study establishes a regulatory function of DNA-PK in the NER process in vivo but rules out a physical role of the complex in the repair machinery at the site of the DNA lesion.

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29Si magic angle spinning-nuclear magnetic resonance study of three samples of potassium-substituted hexagonal cordierites with KxMg2Al4+xSi5−xO18formula (x=0.25, 0.50, 1) has allowed the determination, in each case, of the distribution of aluminium and silicon atoms among the tetrahedral framework sites. It has been shown that the excess of aluminium compensating for the insertion of potassium within the hexagonal channels is accommodated by only the T(2) sites of the six-membered rings. A short-range order, which decreases with increasing potassium content, has been evidenced, in agreement with the results from the Rietveld refinement of neutron diffraction data.

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