Simultaneous Two-Photon Activation of Type-I Photodynamic Therapy Agents

The excitation and emission properties of several psoralen derivatives are compared using conventional single-photon excitation and simultaneous two-photon excitation (TPE). Two-photon excitation is effected using the output of a mode-locked titanium: sapphire laser, the near infrared output of which is used to promote non-resonant TPE directly. Specifically, the excitation spectra and excited-state properties of 8-methoxypsoralen and 4′-aminomethyl-4,5,8-trimethylpsoralen are shown to be equivalent using both modes of excitation. Further, in vitro feasibility of two-photon photodynamic therapy (PDT) is demonstrated using Salmonella typhimurium. Two-photon excitation may be beneficial in the practice of PDT because it would allow replacement of visible or UV excitation light with highly penetrating, nondamag-ing near infrared light and could provide a means for improving localization of therapy. Comparison of possible laser excitation sources for PDT reveals the titanium: sapphire laser to be exceptionally well suited for nonlinear excitation of PDT agents in biological systems due to its extremely short pulse width and high repetition rate that together provide efficient PDT activation and greatly reduced potential for biological damage     

Conductance of aqueous NaCl solutions at pressures up to 2000 atm

Electrical conductance measurements are reported for aqueous NaCl solutions at 25°C as a function of concentration up to 0.02M and pressures up to 2000 atm. The data were analyzed with the Fuoss-Hsia-Fernandez-Prini (FHFP) equation. The standard error of fit, , varies from 0.04 at 1 atm to 0.10 at 2000 atm. The increase of with pressure arises from increasing non-randomness in the distribution of errors about the FHFP equation suggesting that modifications in the theory are necessary. The pressure dependence of _O for NaCl and KCl is nearly identical.Contribution of the Scripps Institution of Oceanography, New Series     

Investigation of bicyclic thioketones as triggers for liquid crystal optical switches

The axially chiral bicyclic thioketones 11 and 15 were prepared and investigated for suitability as chiroptical triggers in a liquid crystal optical switch. Irradiation of partially resolved 15 with unpolarized light leads to its conversion to the racemic form (photoracemization). However, irradiation of racemic thioketones 11 and 15 with circularly polarized light does not lead to detectable photoresolution. The lack of photoresolution was traced to inefficiency in intramolecular, through-bond triplet energy transfer. These thioketones are not suitable for use as phototriggers.     

210Pb/210Po isotope generator

As a continuation of previous work (Kmak et al. in J Radioanal Nucl Chem 314:985–989, 2017), an isotope generator column based on the ²¹⁰Pb decay chain has been made to produce highly radiopure ²¹⁰Po. Two replicate studies were performed on AG 50Wx8 columns with an average yield of 90.4 ± 1.9%. ²¹⁰Pb breakthrough was seen at the 6 month elution for both generators.

     

Characterization of a Nudix hydrolase from <Emphasis Type="Italic">Deinococcus radiodurans</Emphasis> with a marked specificity for (deoxy)ribonucleoside 5'-diphosphates

Background  

Nudix hydrolases form a protein family whose function is to hydrolyse intracellular nucleotides and so regulate their levels and eliminate potentially toxic derivatives. The genome of the radioresistant bacterium Deinococcus radiodurans encodes 25 nudix hydrolases, an unexpectedly large number. These may contribute to radioresistance by removing mutagenic oxidised and otherwise damaged nucleotides. Characterisation of these hydrolases is necessary to understand the reason for their presence. Here, we report the cloning and characterisation of the DR0975 gene product, a nudix hydrolase that appears to be unique to this organism.     

Fully automated micro- and nanoscale one- or two-dimensional high-performance liquid chromatography system for liquid chromatography-mass spectrometry compatible with non-volatile salts for ion exchange chromatography

A one- or two-dimensional high performance liquid chromatography system for electrospray ionization mass spectrometers has been developed that is optimized for ion exchange and reversed phase separations. A unique and simple valve configuration permits the use of a variety of non-volatile salts; ammonium sulfate was used in an example of strong cation exchange separations. The system was designed and evaluated for both micro- and nanoflow chromatography. The peptide detection limit was approximately 100 fmol for micro- and 20 fmol for nanoflow, demonstrating the concentration and mass sensitivity improvements expected with nanoelectrospray ionization. The 1D/2D-HPLC MS system is fully automated for routine peptide analyses, compatible with direct injection of proteolytic digests, and exhibits chromatographic reproducibility and sensitivity. Software permits operator selection of either a 1D or 2D configuration with corresponding system parameters as required for individual samples. The hardware elements and resulting performance are described in this paper.     

ADRIAMYCIN RESISTANCE IN CHINESE HAMSTER FIBROBLASTS FOLLOWING OXIDATIVE STRESS INDUCED BY PHOTODYNAMIC THERAPY

Photodynamic therapy (PDT) generates reactive oxygen species that are responsible for the initial cytotoxic events produced by this treatment. An extended (16 h) porphyrin incubation prior to light irradiation increased expression of the 75, 78 and 94 kDa glucose-regulated stress proteins (GRP), as well as the cognate form of the 70 kDa heat shock protein. However, these stress proteins were not induced following isoeffective PDT doses using a short (1 h) porphyrin incubation protocol. In the current study, Chinese hamster fibroblasts were used to examine sensitivity to adjunctive PDT and adriamycin as previous reports indicate a correlation between stress protein synthesis and a decrease in adriamycin cytotoxicity. Treatments that either induced GRP ( i.e . PDT with an extended porphyrin incubation or exposure to the calcium ionophore A23187) or did not induce GRP ( i.e . PDT with a short porphyrin incubation or UV irradiation) were followed at increasing time intervals with a 1 h adriamycin incubation. A time-dependent decrease in adriamycin cytotoxicity was observed when cells were first exposed to either of the PDT protocols or to A23187. Alterations in intracellular drug levels did not account for the change in adriamycin sensitivity. Likewise, intracellular glutathione concentrations and antioxidant enzyme activities were not significantly altered following PDT or A23187. Parameters associated with altered adriamycin sensitivity included a decrease in the percentage of S phase cells following PDT and A23187 as well as a depletion of intracellular ATP after PDT using the extended porphyrin incubation. These results demonstrate that PDT can be added to the growing list of diverse stresses producing transient resistance to adriamycin and that stress protein induction is not universally associated with all oxidative treatments inducing this resistance.     

Synthesis and characterization of linear high molecular weight poly(amino-s-triazine)s

A two-phase polycondensation reaction was used to prepare high molecular weight linear poly-(amino-s-triazine)s from aminodichloro-s-triazines and diamines. These polymers contain a high concentration of melamine-type units in the polymer backbone. Molded specimens exhibited good mechanical properties and resistance to organic solvents. Dimethyl substitution at the exocyclic amino group led to a significant reduction in indentation resistance, strength, and modulus.     

Synthesis,characterisation and ferric ion complexation studies of chelating probes for oxidative stress

The ferric ion binding characteristics of a novel chelating probe for detecting reactive oxygen and nitrogen species are reported. The probe comprises a polyaminocarboxylic acid chelator (EDTA) conjugated with aromatic amino acids. The probe (i) complexes redox-active and non-redox active metal ions and (ii) differentiates between different reactive oxygen/nitrogen species based upon the reaction products with same. The ferric ion binding characteristics were measured using species distribution and electronic absorption spectroscopic investigations. Over the physiological pH range a favoured one to one complex exists.     

Mechanisms of intrinsic bioremediation of gas condensate hydrocarbons in saturated soil

Applied Biochemistry and Biotechnology - The addition of gas condensate hydrocarbons to saturated soil from a gas production site stimulated sulfate reduction under anaerobic and oxygen-limiting...