Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.

Summary DNA2, a helicase/nuclease family member, plays versatile roles in processing DNA intermediates during DNA replication and repair. Yeast Dna2 (yDna2) is essential in RNA primer removal during nuclear DNA replication and is important in repairing UV damage, base damage, and double-strand breaks. Our data demonstrate that, surprisingly, human DNA2 (hDNA2) does not localize to nuclei, as it lacks a nuclear localization signal equivalent to that present in yDna2. Instead, hDNA2 migrates to the mitochondria, interacts with mitochondrial DNA polymerase γ, and significantly stimulates polymerase activity. We further demonstrate that hDNA2 and flap endonuclease 1 synergistically process intermediate 5’ flap structures occurring in DNA replication and long-patch base excision repair (LP-BER) in mitochondria. Depletion of hDNA2 from a mitochondrial extract reduces its efficiency in RNA primer removal and LP-BER. Taken together, our studies illustrate an evolutionarily diversified role of hDNA2 in mitochondrial DNA replication and repair in a mammalian system.

Repair of oxidative DNA damage in mitochondria was thought limited to short-patch base excision repair (SP-BER) replacing a single nucleotide. However, certain oxidative lesions cannot be processed by SP-BER. Here we report that 2-deoxyribonolactone (dL), a major type of oxidized abasic site, inhibits replication by mitochondrial DNA (mtDNA) polymerase ␥ and interferes with SP-BER by covalently trapping polymerase ␥ during attempted dL excision. However, repair of dL was detected in human mitochondrial extracts, and we show that this repair is via long-patch BER (LP-BER) dependent on flap endonuclease 1 (FEN1), not previously known to be present in mitochondria. FEN1 was retained in protease-treated mitochondria and detected in mitochondrial nucleoids that contain known mitochondrial replication and transcription proteins.

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A major function of the acinar cells of the lacrimal gland is the production and stimulated release of tear proteins into ocular surface fluid. We investigate the participation of cytoplasmic dynein in carbachol-stimulated traffic to the apical plasma membrane in primary rabbit lacrimal acinar epithelial cells. Confocal fluorescence microscopy revealed a major carbachol-induced, microtubule-dependent recruitment of cytoplasmic dynein and the dynactin complex into the subapical region. Colocalization studies,sorbitol density gradient/phase partitioning analysis and microtubule-affinity purification of membranes showed that some dynein and dynactin complex were associated with VAMP2-enriched membranes. Adenovirus-mediated overexpression of p50/dynamitin inhibited the recruitment and colocalization of dynein, the dynactin complex and VAMP2 in the subapical region. Nocodazole treatment and p50/dynamitin overexpression also depleted subapical stores of rab3D in resting acini, suggesting that dynein activity was also involved in maintenance of rab3D-enriched secretory vesicles. These data implicate cytoplasmic dynein in stimulated traffic to the apical plasma membrane in these secretory epithelial cells.

Polymers have been widely used as piezoelectric materials in the form of films and bulk materials but there are limited publications on piezoelectric fibre structures. In this paper the process of preparing piezoelectric polyvinylidene fluoride (PVDF) fibres from granules by continuous melt extrusion and in-line poling is reported for the first time. The poling of PVDF fibres was carried out at an extension ratio of 4:1, a temperature of 80 •C and a high voltage of the order of 13 000 V on a 0.5 mm diameter fibre in a melt extruder. The entire process of making PVDF fibres from granules and poling them to make piezoelectric fibres was carried out in a continuous process using a customized melt extruder. The prepared piezoelectric fibres were then tested using an impact test rig to show the generation of voltage upon application of an impact load. PVDF granules, unpoled fibres and poled fibres were examined by Fourier transform infrared spectroscopy (FTIR) which showed the presence of β phase in the poled fibres. The ultimate tensile stress and strain, Young's modulus and microstructures of poled and unpoled fibres were investigated using a scanning electron microscope (SEM). Abstract. Polymers have been widely used as piezoelectric materials in the form of films and bulk materials but there are limited publications on piezoelectric fibre structures. In this paper the process of preparing piezoelectric Polyvinylidene Fluoride (PVDF) fibres from granules by continuous melt extrusion and in-line poling is reported for the first time. The poling of PVDF fibres was carried at an extension ratio of 4:1, temperature of 80 °C and high voltage of the order of 13000 V on a 0.5mm diameter fibre in a melt extruder. The entire process of making PVDF fibres from granules and poling them to make piezoelectric fibres was carried out in a continuous process using a customised melt extruder. The prepared piezoelectric fibres were then tested using an impact test rig to show the generation of voltage upon application of an impact load. PVDF granules, unpoled fibres and poled fibres were examined by Fourier Transform Infrared Spectroscopy (FTIR) which shows the presence of β phase in the poled fibres. The ultimate tensile stress and strain, Young's modulus and microstructures of poled and unpoled fibres were investigated using a scanning electron microscope (SEM).

Despite the wealth of information available on the biochemical functions and our recent findings of its roles in genome stability and cancer avoidance of the structure-specific flap endonuclease 1 (FEN1), its cellular compartmentalization and dynamics corresponding to its involvement in various DNA metabolic pathways are not yet elucidated. Several years ago, we demonstrated that FEN1 migrates into the nucleus in response to DNA damage and under certain cell cycle conditions. In the current paper, we found that FEN1 is superaccumulated in the nucleolus and plays a role in the resolution of stalled DNA replication forks formed at the sites of natural replication fork barriers. In response to UV irradiation and upon phosphorylation, FEN1 migrates to nuclear plasma to participate in the resolution of UV cross-links on DNA, most likely employing its concerted action of exonuclease and gap-dependent endonuclease activities. Based on yeast complementation experiments, the mutation of Ser 187 Asp, mimicking constant phosphorylation, excludes FEN1 from nucleolar accumulation. The replacement of Ser 187 by Ala, eliminating the only phosphorylation site, retains FEN1 in nucleoli. Both of the mutations cause UV sensitivity, impair cellular UV damage repair capacity, and decline overall cellular survivorship.Flap endonuclease 1 (FEN1) represents a unique class of structure-specific 5Ј nucleases that possess three distinct nuclease activities: FEN activity, nick-specific exonuclease (EXO) activity, and gap-dependent endonuclease (GEN) activity (18,37,56). Unlike endonucleases that recognize a specific DNA sequence, FEN1 recognizes a specific DNA structure, independent of the DNA sequence. Specifically, FEN1 recognizes a branched DNA structure consisting of a single unpaired 3Ј nucleotide (3Ј flap) overlapping with a variablelength region of 5Ј single-stranded DNA (5Ј flap) (27, 29). These "double-flap" or "overlap-flap" structures result from DNA polymerase and/or helicase activity that displaces damaged DNA or RNA primers, creating a 5Ј single-stranded DNA flap. The newly synthesized DNA and the displaced region compete for base pairing with the template strand, resulting in the formation of the double-flap structure (53). FEN1 cleaves this substrate precisely after the first base pair that precedes the 5Ј flap to remove the single-stranded DNA 5Ј flap and create a nicked DNA product ready for ligation (27,29,66). This FEN activity-driven reaction is most likely critical for RNA primer removal during the maturation of Okazaki fragments and long-patch DNA base excision repair (33,34,42,44). However, under the circumstances in which the ligase is not able to compete for the nick substrate, the FEN1 nuclease will transfer its reaction mode from FEN to EXO and continue to remove the nucleotides from the 5Ј end, generating a single-stranded region (gap) (2, 24). This gap is an ideal substrate for the newly discovered third activity of the FEN1 nuclease (GEN). The same nuclease is able to make another transition to nick the singl...

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