Facile synthesis of a cis-syn thymine dimer building block and its incorporation into oligodeoxynucleotides

The synthesis of a building block containing the photobiologically relevant cis-syn thymine cyclobutane photoproduct and its incorporation into oligonucleotides by the phosphoramidite-based solid-phase synthesis is reported. Compared to previous syntheses, this route is extremely short and allows such modified oligonucleotides to be easily available for biological studies.     

Cracking in polylactide spherulites

A polylactide of high optical purity was crystallized between 100 and 140 °C, in‐between two glass slides, and its morphology was investigated by polarizing optical microscopy, scanning electron microscopy, and atomic force microscopy, during subsequent heating and cooling cycles between ?15 °C and the crystallization temperature. It was found that dark circular rings show up on cooling on top of the spherulites and represent cracks of about 300 nm in width. This phenomenon is completely reversible, and the heating–cooling curves are centered at about 56 °C, which coincide with the T_g of polylactide. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3308–3315, 2005     

Preliminary report on detection of papillomaviruses types 6, 11, 16, and 18 in laryngeal benign and malignant lesions

Recently, clinicians have observed an increase in the incidence of laryngeal papilloma coincident with the rising incidence of venereal warts. The lesions occur in young adults of professional singing age. Different types of human papillomavirus (HPV) are presented. Gynecologic exam revealed cervical tumors, involving 18 HPV in benign and malignant lesions. Thirty patients with the following pathologic conditions were studied: 10 papillomas, 10 severe dysplasias, and 10 invasive cancers. All the lesions were located on the free edge of the vocal folds or the anterior commissure involving the epithelium. The results are as follows: 11 patients (33%) had virus infection, of which four had HPV 6 or HPV 11 on laryngeal papilloma, three had HPV 16 or HPV 18 on severe dysplasia, four had HPV 16 or HPV 18 on carcinoma; and 19 (66%) had no virus infection. Gynecologic research in this field is more advanced. However, this preliminary report raises interesting research questions in laryngology.     

Spasmodic dysphonia symptoms as initial presentation of amyotrophic lateral sclerosis

A patient initially diagnosed with adductor-type spasmodic dysphonia was referred for botulinum toxin (Botox) injections, but found on subsequent evaluation to have amyotrophic lateral sclerosis, and therefore Botox was not administered. This unique case underscores the need to delay botulinum toxin treatments in any patient with recent onset symptoms, and to obtain thorough motor speech and voice, otolaryngologic, and neurologic evaluation in all patients prior to consideration for injection.     

Aggregation behaviors of gemini nucleotide at the air-water interface and in solutions induced by adenine-uracil interaction

Cationic gemini surfactants having nucleotides as counterions (called nucleo-gemini hereafter) were synthesized and their aggregation behavior at air-water surfaces as well as in bulk solutions were studied. Fluid solutions of these nucleo-gemini surfactants show transitions to hydrogels upon addition of complementary nucleoside bases or other nucleo-gemini surfactants having complementary bases as counterions. The FTIR-ATR measurements show that the carboxylate groups of uridine form hydrogen bonds with the amine groups of adenosine. The aggregation behavior was also confirmed at the air-water interface by Brewster angle microscopy as well as surface pressure measurements; the monolayer of a gemini nucleotide was observed to undergo a transition to multilayers when nucleosides with complementary bases were added into the subphase. Isotherm curves of surface pressure monitored in parallel show a decrease in molecular area upon addition of such nucleosides.     

Porous materials show superhydrophobic to superhydrophilic switching

Switching between superhydrophobicity and superhydrophilicity in porous materials was predicted theoretically and demonstrated experimentally with the example of thermally induced contact angle change; tunability of this system was also demonstrated.     

Latex bead immobilisation in PDMS matrix for the detection of p53 gene point mutation and anti-HIV-1 capsid protein antibodies

Two diagnostic chemiluminescent biochips were developed for either the detection of p53 gene point mutation or the serological detection of anti-HIV-1 p24 capsid protein. Both biochips were composed of 24 microarrays of latex beads spots (4×4) (150 m in diameter, 800 m spacing) entrapped in a poly(dimethylsiloxane) elastomer (PDMS). The latex beads, bearing oligonucleotide sequences or capsid protein, were spotted with a conventional piezoelectric spotter and subsequently transferred at the PDMS interface. The electron microscopy observation of the biochips showed how homogeneous and well distributed the spots could be. Point mutation detection on the codon 273 of the p53 gene was performed on the basis of the melting temperature difference between the perfect match sequence and the one base pair mismatch sequence. The hybridisation of a 20-mer oligonucleotide form the codon 273 including a one base pair mutation in its sequence on a biochip arrayed with non-muted and the muted complementary sequences, enabled a clear discrimination at 56°C between muted and wild sequences. Moreover, the quantitative measurement of the amount of muted sequence in a sample was possible in the range 0.4–4 pmol. Serological measurement of anti-HIV-1 p24 capsid protein on the biochip, prepared with 1-m-diameter latex beads, enabled the detection of monoclonal antibodies in the range 1.55–775 ng mL^–1. Such a range could be lowered to 0.775 ng mL^–1 when using 50-nm-diameter beads, which generated a higher specific surface. The validation of the biochip for the detection of anti-HIV-1 capsid protein antibodies was performed in human sera from seropositive and seronegative patients. The positivity of the sera was easily discriminated at serum dilutions below 1:1,000.     

Segmentation under geometrical conditions using geodesic active contours and interpolation using level set methods

Let I: be a given bounded image function, where is an open and bounded domain which belongs to ⁿ. Let us consider n=2 for the purpose of illustration. Also, let S={x_i}_i be a finite set of given points. We would like to find a contour , such that is an object boundary interpolating the points from S. We combine the ideas of the geodesic active contour (cf. Caselles et al. [7,8]) and of interpolation of points (cf. Zhao et al. [40]) in a level set approach developed by Osher and Sethian [33]. We present modelling of the proposed method, both theoretical results (viscosity solution) and numerical results are given. AMS subject classification 49L25, 74G65, 68U10     

Effect of ambient pressure on the crystalline phase of nano TiO2 particles synthesized by a dc thermal plasma reactor

The synthesis of nanoparticles of titanium dioxide (TiO₂) with varying percentages of anatase and rutile phases is reported. This was achieved by controlling the operating pressure in a transferred-arc, direct current thermal plasma reactor in which titanium vapors are evaporated, and then exposed to ambient oxygen. The average particle size remained around 15 nm in each case. The crystalline structure of the as-synthesized nanoparticles of TiO₂ was studied with X-ray diffraction analysis; whereas the particle morphology was investigated with the help of transmission electron microscopy. The precursor species responsible for the growth of these nanoparticles was studied with the help of optical emission spectroscopy. As inferred from the X-ray diffraction analysis, the relative abundance of anatase TiO₂ was found to be dominant when synthesized at 760 Torr, and the same showed a decreasing trend with decreasing chamber pressure. The study also reveals that anatase TiO₂ is a more effective photocatalytic agent in degrading methylene blue by comparison to its rutile phase.