Uridine as Photochemical Actinometer: Application to Led-Uv Flow Reactors

Abstract

Two LED-UV based photochemical flow reactors have been compared. One was a commercially available LED-UV flow reactor designed for water disinfection or sterilization and the other one was a home-made LED-UV flow reactor designed for analogous purposes. The photochemical performances of two mentioned flow reactors working both at about 275 nm were evaluated using uridine actinometry through the determination of the pseudo-first order kinetics rate constant of uridine photolysis and through the measurement of the incident light I absorbed by the actinometer solution. From these data, the energy released to the solution by the LED-UV sources was determined. Furthermore, a third LED-UV reactor working at 360 nm was evaluated with uridine actinometer. As expected in the latter case uridine was not photolyzed and the reactor was found unsuitable for water disinfection.

The effect of flanking bases on direct and triplet sensitized cyclobutane pyrimidine dimer formation in DNA depends on the dipyrimidine, wavelength and the photosensitizer

“…Irradiations were carried out on the 5′- [ 32 P]-labeled 149-mer or 79-mer DNA substrates and the indicated amount of photosensitizer (if used) in 20 μl of T4-pdg buffer (50 mM NaCl, 5 mM EDTA, 10 mM Tris–HCl buffer, pH 7.5 in a 1.5 ml polyethylene microfuge tube lying on its side in ice water. The UVC light source consisted of two UVC tubes (XX-15F, Spectroline) delivering ∼8.5 mW/cm 2 of 254 nm light at 1 cm, corresponding to 85 J/m 2 -s as determined by uridine actinometry in a quartz cuvette ( 58 ) and ∼65 J/m 2 -s in the microfuge tube. Broadband UVB (BB UVB, 275–400 nm, centered at 312 nm) irradiation was carried out with two UVB tubes (XX-15B, Spectroline) delivering ∼5.5 mW/cm 2 at 1 cm (55 J/m 2 -s) using a light meter.…”

Thermodynamic Driving Force in the Spontaneous Formation of Inorganic Nanoparticle Solutions

“…Here, we assume donor–acceptor interactions dominate and set the Gibbs energy of solvent-NP interactions equal to the Gibbs energy of donor-acceptor interactions, Δ g s–NP ≈ Δ G d–a , because we experimentally observe these interactions, and they are typically significantly stronger than other noncovalent interactions. We apply a = SbCl 5 as the standard acceptor due to the extensive data available . Δ g s–s is approximated as Gibbs energy of vaporization (Δ g s–s ≈ Δ G vap ), which is a measure of the strength of intermolecular interactions.…”

UV Resistance of Nucleosides—An Experimental Approach

“…Cataldo (2017) investigated the UV photolysis of uridine in water using UV absorption spectrophotometry . The study assumed a first-order reaction mechanism.…”

“…Cataldo (2017) investigated the UV photolysis of uridine in water using UV absorption spectrophotometry. 35 The study assumed a first order reaction mechanism. Decay rates were calculated by using a function of the form ln(I/I 0 ) = t•k, where t refers to the irradiation time, I refers to the intensity at time t, and I 0 refers to the initial intensity.…”