Enhancing the photostability of poly(phenylene ethynylene) for single particle studies.

Single molecule fluorescence (SMF) studies on conjugated polymers yield enhanced information on exciton dynamics and on the interplay between polymer conformation/morphology and photophysical behavior. SMF studies, however, demand good signal stability, excellent photostability, and high photon yields (a measure of both photostability and brightness) and thus the development of strategies to help conjugated polymers (CPs) meet these requirements is a topic of great interest. Here, we evaluate the effect of a number of triplet quencher additives on the photostability of a 49-mer long poly(phenylene-ethynylene) conjugated polymer bearing carboxylate side groups (PPE-CO2-49) that is deposited onto 100 nm diameter SiO2 nanoparticles (NPs). The additives tested include ascorbic acid (AA), ß-mercaptoethanol (BME), Ni2+, trolox (TX), and a trolox/trolox quinone mixture (TX/TQ), used either with or without an enzymatic oxygen scavenging system (glucose oxidase/catalase, GODCAT). Total internal reflection fluorescence microscopy (TIRFM) studies enabled the determination of the effect of the additives on the rates of photobleaching, the initial intensity, and the total photon output for hundreds of conjugated polymer coated SiO2 nanoparticles monitored in parallel. Addition of the antioxidant/triplet quenchers AA and TX led to a 3-8-fold increase in the number of photons collected as well as an enhancement of the initial emission intensity, consistent with an increase in the duty cycle attributed to the quenching of triplet states. Removal of oxygen led to an impressive 10-15-fold increase in the photostability relative to buffer, implicating reactive oxygen species (ROS) as an important agent in the photodegradation of PPE-CO2-49. Combining AA and TX with GODCAT had a deleterious rather than an additive effect, suggesting that an oxidizing agent is in fact necessary to rescue the polymer from reactive intermediates formed via reaction with AA/TX. ß-Mercaptoethanol and Ni2+ were not found to have useful properties toward the photostabilization of PPE-CO2-49. The results of this study provide suitable imaging conditions to conduct single molecule imaging experiments on conjugated polyelectrolytes.

meso-Acetoxymethyl BODIPY dyes for photodynamic therapy: improved photostability of singlet oxygen photosensitizers.

We report two BODIPY based photosensitizers (Br2BOAc and I2BOAc) featuring an acetoxymethyl substituent at the meso-position. These photosensitizers show improved photostability against singlet oxygen, when compared to a BODIPY photosensitizer lacking the acetoxymethyl group. Both compounds were evaluated for photodynamic therapy against HeLa cells and photodynamic inactivation against E. coli bacteria. We show that the compounds readily embed in the lipid membranes of HeLa cervical cancer cells and efficiently induced light-dependent apoptosis at nanomolar concentration. Also, both compounds showed a substantial degree of photoinactivation of E. coli bacteria when used at low micromolar concentrations.

Photophysical properties of fluorescent DNA-dyes bound to single- and double-stranded DNA in aqueous buffered solution.

The absorption and fluorescence spectra, fluorescence quantum yields, lifetimes and time-resolved fluorescence spectra are reported for nine different fluorescent DNA-dyes. The work was initiated in search of a quantitative method to detect the ratio of single-to-double stranded DNA (ssDNA/dsDNA) in solution based on the photophysics of dye-DNA complexes; the result is a comprehensive study providing a vast amount of information for users of DNA strains. The dyes examined were the bisbenzimide or indole-derived stains (Hoechst 33342, Hoechst 33258 and 4',6-diamidino-2-phenylindole), phenanthridinium stains (ethidium bromide and propidium iodide) and cyanine dyes (PicoGreen, YOYO-1 iodide, SYBR Green I and SYBR Gold). All were evaluated under the same experimental conditions in terms of ionic strength, pH and dye-DNA ratio. Among the photophysical properties evaluated only fluorescence lifetimes for the cyanine stilbene dyes allowed a convenient differentiation between ssDNA and dsDNA. The bisbenzimide dyes showed multiexponential decays when bound to either form of DNA, making lifetime-based analysis cumbersome with inherent errors. These dyes also presented biexponential decay when free in aqueous buffered solutions at different pH. A mechanism for their deactivation is proposed based on two different conformers decaying with different kinetics. The phenanthridinium dyes showed monoexponential decays with ssDNA and dsDNA, but there was no discrimination between them. High dye-DNA ratios (e.g. 1:1) resulted in multiexponential decays for cyanine dyes, resulting from energy transfer or self-quenching deactivation. Shifts in both absorption and fluorescence maxima for both ssDNA and dsDNA DNA-cyanine dye complexes were small. Broadening of dye-ssDNA absorption and fluorescence bands for the cyanine dyes relative to dye-dsDNA bands was detected and attributed to higher degrees of rotational freedom in the former.

Primary syphilis of the rectum--endoscopic and clinical features. Report of a case.

A 33-year-old man was admitted to our hospital for suspected rectal tumor. Endoscopy showed a rectal mass not typical of carcinoma, and histologic evaluation of biopsy specimens revealed granulomatous inflammation. Venereal Disease Research Laboratories (VDRL) and Treponema pallidum hemagglutination (TPHA) tests became positive during hospitalization, and dark-field examination was positive for Treponemas, thus allowing the diagnosis of chancre of the rectum. The clinical and endoscopic features of this case are described.

[An intervention policy for reducing noise pollution in urban areas]. / Politiche di intervento per il risanamento delle aree urbane rumorose.

The methodological methods for a reduction of the noise pollution in the urban areas, mainly, can be advised in 8 operative points: 1) reduction of the source's noise; 2) control of the traffic; 3) planning of the urban and regional development; 4) building's shelter against the noise; 5) compensation's and incentivation's interventions for the exposed people; 6) controls activity and restaining of the noise's sources; 7) scientific research; 8) health education. For executive motivations we must, necessarily, divide the intervention turned to a reduction of the noise's emissions caused by fixed source compared to the noise's emissions determined by motor or railway traffic (mobile sources). This operative criteria have been utilized recently (1988) from Italian Department of Ecology for a bill. The controls of fixed source are made by Public Health Services of U.S.L. (Local Sanitary Unit) assisted, in case, by multiarea country's districts. The regulations of traffic can be took in consideration, in short time, only in more simple problems, as the setting up of pedestrian island or the suspensions of the heavy traffic, etc. The traffic's regulation must care same general data: the halved of traffic's flow in same rilevation's point, involve a reduction of only 3 dBA of the sound pressure level previously measured; if the percentage of heavy traffic is higher than 10% of the traffic's flow, the first intervention must be the no thorough fare to heavy lorries. In general, then, the best way for the resolution of vehicular noise pollution is the noisy emission's control of the single vehicle, because only the regulation of traffic's flow doesn't suffice to realise a enough reduction of noise pollution. For the resolution of more complex problems is necessary a preliminary stage to study and to plan those before to can carry out a typology of intervention. This necessity is, of course, more expensive in time and money; in fact, the solution of the problem can be the building of a efficient subway network completed by car parks in the terminal stations. In alternation at this draft, we can pointed out, also, same compromise resolutions like the appoint areas to limited traffic in the town or the break of continuity of the bus-line in the town. The compensation or the incentivation to make defence works against noise is a very expensive way and, moreover, they don't solve the problem for all exposed people in a future.(ABSTRACT TRUNCATED AT 400 WORDS)

[Annoyance, disturbance and damage caused by noise and vibrations]. / Annoyance, disturbo e danno da rumore e da vibrazioni.

The pathogenic effects derived by the emission of noises and vibrations, essentially, are conditioned from three etiological factors. The first of those is the energetic level of the sound emission, whereas the second is the exposure time and the last is the spectral composition. We, making reference to sound source, can associate to the first etiological factors the influence of impulsive components present in the noise; whereas to the second the importance of the functional recovery time of auditory acuity and, at last, to the third etiological factors the annoyance caused by the superimposition of pure tone or of tight band noise, contained in 1/3 of octave. The specific effects, caused by the noise exposure, affect the auditory system (acoustic trauma, auditory weariness, noise deafness) and the vestibular system (vertigo, sickness, trouble of balance). Those effects are fortly dependent to the entity of the sound energy accepted in a calculated time interval (LEP), and after the end of noise expositions they aren't developed. The specific effects became permanent when the degeneration of the Corti's cells occurred. The noise deafness, in first time, impair the frequencies included between 3000 and 6000 Hz, particularly it concerns the thigh band of 4000 Hz. Those lesions happen after a prolonged exposition to LEP greater than 80-85 dBA, and its evolutions, usually, follow a succession of clinical stages that can be monitored through audiometric controls to allow the necessary preventive measures. The nonspecific effects, derived to the noise exposition can be divided in: 1) neuroendocrinologic and psychological effects; 2) psychosomatic effects; 3) psychosocial effects. The psychological effects (anxiety, depression, conflict condiction) are strictly related with neuroendocrinological responses to the sound impact, this, for the smaller entity of stimulation, is identical to locality reaction, on the contrary for more violent stimulations those determine and adaptative reaction (Selye syndrome) that consist in a excitement of the thalamus and pituitary gland, this determines a multiple endocrine hyperactivity followed from a inhibition period or, possibly, an adaptation period. The noise exposure determines, besides, same E.E.G. alterations and a reduction of walls' tone of the brain's arteries. The psychosomatic effects of the noise appear with emission greater than or equal to 70 dBA and these can be distinguished in: cardiovascular effects, gastrointestinal effects, respiratory effects, visual and genitals effects. The noise in these cases, mainly, acts as a risk's factors. The noise is, again, the cause of the arising of psychosocial effects. These can be classified as: interference on the transmission and understanding of the words, perfect healthy respect the efficiency and the learning capacity of the exposed subject, interference on the duration and quality of the sleep.(ABSTRACT TRUNCATED AT 400 WORDS)