Copper(II) complexes with the first-generation quinolone antibacterial agent norfloxacin containing a nitrogen donor heterocyclic ligand 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) were prepared and characterized by IR, EPR spectra, molar conductivity, and elemental analyses. The experimental data suggest that norfloxacin was coordinated to copper(II) through the carboxylato and ketone oxygen atoms. The interaction of the copper(II) complexes with bovine serum albumin (BSA) and human serum albumin (HSA) was investigated using fluorescence quenching of the tryptophan residues and copper(II) EPR spectroscopy. The results of fluorescence titration revealed that copper(II) complexes have a moderate ability to quench the intrinsic fluorescence of the albumins through a static quenching mechanism. EPR experiments showed that BSA and HSA Cu(II) sites compete with NOR for Cu(II)-bipy and Cu(II)-phen to form protein mixed-ligand complexes. Copper(II) complexes, together with the corresponding ligands, were evaluated for their trypanocidal activity in vitro against Trypanosoma cruzi, the causative agent of Chagas disease. The tests performed using bloodstream trypomastigotes showed that the Cu(II)-N-donor precursors and the metal complexes were more active than the free fluoroquinolone.

Context. Extraterrestrial materials, such as meteorites and interplanetary dust particles, provide constraints on the formation and evolution of organic matter in the young solar system. Micrometeorites represent the dominant source of extraterrestrial matter at the Earth's surface, some of them originating from large heliocentric distances. Recent analyses of ultracarbonaceous micrometeorites recovered from Antarctica (UCAMMs) reveal an unusually nitrogen-rich organic matter. Such nitrogen-rich carbonaceous material could be formed in a N 2 -rich environment, at very low temperature, triggered by energetic processes. Aims. Several formation scenarios have been proposed for the formation of the N-rich organic matter observed in UCAMMs. We experimentally evaluate the scenario involving high energy irradiation of icy bodies subsurface orbiting at large heliocentric distances. Methods. The effect of Galactic cosmic ray (GCR) irradiation of ices containing N 2 and CH 4 was studied in the laboratory. The N 2 -CH 4 (90:10 and 98:2) ice mixtures were irradiated at 14 K by 44 MeV Ni 11+ and 160 MeV Ar 15+ swift heavy ion beams. The evolution of the samples was monitored using in-situ Fourier transform infrared spectroscopy. The evolution of the initial ice molecules and new species formed were followed as a function of projectile fluence. After irradiation, the target was annealed to room temperature. The solid residue of the whole process left after ice sublimation was characterized in-situ by infrared spectroscopy, and the elemental composition was measured ex-situ. Results. The infrared bands that appear during irradiation allow us to identify molecules and radicals (HCN, CN − , NH 3 , ...). The infrared spectra of the solid residues measured at room temperature show similarities with that of UCAMMs. The results point towards the efficient production of a poly-HCN-like residue from the irradiation of N 2 -CH 4 rich surfaces of icy bodies. The room temperature residue provides a viable precursor for the N-rich organic matter found in UCAMMs.

The presence of nucleobases in carbonaceous meteorites on Earth is an indication of the existence of this class of molecules in outer space. However, space is permeated by ionizing radiation, which can have damaging effects on these molecules. Adenine is a purine nucleobase that amalgamates important biomolecules such as DNA, RNA, and ATP. Adenine has a unique importance in biochemistry and therefore life. The aim of this work was to study the effects of cosmic ray analogues on solid adenine and estimate its survival when exposed to corpuscular radiation. Adenine films were irradiated at GANIL (Caen, France) and GSI (Darmstadt, Germany) by 820 MeV Kr, 190 MeV Ca, 92 MeV Xe, and 12 MeV C ion beams at low temperature. The evolution of adenine molecules under heavy ion irradiation was studied by IR absorption spectroscopy as a function of projectile fluence. It was found that the adenine destruction cross section (σ) follows an electronic stopping power (S) power law under the form: CS; C is a constant, and the exponential n is a dimensionless quantity. Using the equation above to fit our results, we determined σ = 4 × 10 S, with S in kiloelectronvolts per micrometer (keV μm). New IR absorption bands arise under irradiation of adenine and can be attributed to HCN, CN, CHN, CHCN, and (CH)CNC. These findings may help to understand the stability and chemistry related to complex organic molecules in space. The half-life of solid adenine exposed to the simulated interstellar medium cosmic ray flux was estimated as (10 ± 8) × 10 years. Key Words: Heavy ions-Infrared spectroscopy-Astrochemistry-Cosmic rays-Nucleobases-Adenine. Astrobiology 17, 298-308.

Water ice exists on many objects in space. The most abundant icy species, among them water, are present in the icy satellites of the outer Solar System giant planets. The nuclei of comets, which are mainly composed of water ice, give another example of its abundance. In the interstellar medium (ISM), ice mantles, formed by molecular species sticking on dust grains, consist mainly of water ice. All these objects are exposed to ionizing radiation like ions, UV photons, and electrons. Sputtering of atoms, molecules, ions, and radicals from icy surfaces may populate and maintain exospheres of icy objects in the Solar System. In other respects, ionized hydrides such as OH+, H2O+, and H3O+ have been detected in the gas phase in star-forming regions. Interactions with cosmic rays could be an additional explanation to the current models for the formation of those species. In fact, laboratory simulations showed that the main components of the sputtered ionic species from water ice are oxygen hydrides. In this work, water ice targets were irradiated at several temperatures (10–200 K) by 90 keV O6+ ions, yielding an electronic stopping power of about 12 eV/Å, when the nuclear stopping power is comparable to the electronic stopping power. Sputtering of secondary ions after bombardment of the ice target was analyzed by time-of-flight mass spectrometry (TOF-SIMS). Besides hydrogen ions (H+, H2 +, H3 +), also O+, O2+, OH+, (H2O)+, and clusters of (H2O) n H+ with n = 1–8 are emitted. Our results show a progressive yield decrease with increasing temperature of all of the detected species. This is related to the structure of the ice: the ionic sputtering yield for crystalline ice is much lower than for an amorphous ice. For instance, amorphous ice at 10 K exhibits a yield of the order of 2 × 10–6 secondary (H2O) n H+ hydride ions/projectile (with n = 1–8). As the temperature is increasing toward the phase transition to crystalline ice, the yields decrease by about one order of magnitude.

Ices are omnipresent in cold regions in space on, e.g., comets, dust grains, transneptunian objects, surfaces of planets and their satellites. The dominant molecule in such ices is water, but also other small molecules or even complex organic molecules (COMs) may be present. Ionizing radiation (UV photons, electrons, ions from cosmic rays or solar wind) induces several physico-chemical processes such as radiolysis. The fragmentation of initial molecules followed by chemical reactions between radicals may lead to formation of new molecules. Furthermore, also implanted projectiles can contribute to chemistry by forming new molecular species. Other observed effects include structural changes (compaction, amorphization) and desorption (sputtering) of particles from the surface. At CIMAP (Caen, France), using the different beam lines of the GANIL facility, and at GSI (Darmstadt, Germany), the interaction of swift highly charged heavy ions with astrophysical ices has been studied in a wide projectile energy range from keV to GeV. Here, two examples of our studies on astrophysical and astrochemical applications will be discussed in detail: 1) the synthesis of COMs under irradiation of ices made of small molecules, and 2) radiosensitivity of COMs such as pyridine, glycine and adenine, both for isolated molecules in the gas phase and in condensed phase. Special emphasis is given on pyridine and pyridine in water matrix.

Radiolysis of biomolecules by fast ions has interest in medical applications and astrobiology. The radiolysis of solid D-valine (0.2–2 μm thick) was performed at room temperature by 1.5 MeV H+, He+, N+, and 230 MeV S15+ ion beams. The samples were prepared by spraying/dropping valine-water-ethanol solution on ZnSe substrate. Radiolysis was monitored by infrared spectroscopy (FTIR) through the evolution of the intensity of the valine infrared 2900, 1329, 1271, 948, and 716 cm−1 bands as a function of projectile fluence. At the end of sample irradiation, residues (tholins) presenting a brownish color are observed. The dependence of the apparent (sputtering + radiolysis) destruction cross section, σd, on the beam stopping power in valine is found to follow the power law σd = aSen, with n close to 1. Thus, σd is approximately proportional to the absorbed dose. Destruction rates due to the main galactic cosmic ray species are calculated, yielding a million year half-life for solid valine in space. Data obtained in this work aim a better understanding on the radioresistance of complex organic molecules and formation of radioproducts.

The interaction of the antimicrobial drug norfloxacin (NFX) with anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) micelles was studied using the intrinsic spectroscopic properties of NFX to obtain association constants and molecular modifications. Nonionic Tween(®) 20 micelles were also investigated, but the spectroscopic properties of NFX did not detect interactions with these micelles, and quenching by iodide suggested a weak association constant around 47 M(-1). For SDS and CTAB, UV-Vis absorption spectroscopy, steady-state and time-resolved fluorometry were monitored as a function of surfactant concentration ranging from the premicellar to micellar region. It was found that cationic (pH 4.0) and zwitterionic NFX (pH 7.4) associate with SDS micelles, with binding constants equal to 5.4 × 10(3) and 1.7 × 10(3) M(-1), respectively. Premicellar interaction slightly decreases the critical micelle concentration of SDS. Association of anionic NFX (pH 10.6) is very weak. The fluorescence spectrum and lifetime showed that SDS-associated NFX is cationic and that the heterocycle penetrates the interfacial environment of decreased polarity. Cationic CTAB micelles do not bind cationic NFX, and the association constant with zwitterionic NFX is two orders of magnitude lower than that of SDS micelles. From a pharmacological point of view, it is important that at neutral pH, NFX presented a two orders of magnitude higher affinity for anionic than for cationic sites, and did not interact significantly with nonionic or zwitterionic micelle interfaces.

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