Cyclometallated platinum and iridium complexes with thiolate ligands, and novel bioimaging agents inspired by dynamic disulfide interchange reactions

The photoluminescence properties of cyclometallated second and third row transition metal complexes make them potential candidates for use in a range of applications such as triplet harvesting agents in OLEDS, as photosensitizers, and in solar cells. Also, the strong luminescence of these complexes gives them much potential for use in chemosensing applications and as bioimaging agents. This final topic is an area of increasing study as a result of the diverse and tuneable excited states of such molecules, and their advantages over conventional organic emitters such as reduced photobleaching and long luminescence lifetimes allowing time-resolved imaging to be performed. The synthesis of cyclometallated complexes of the type [Pt(N^C^N)Cl], [Ir(N^C)2(L)Cl], and [Ir(N^C^N)(N^X)Cl]n+ (where N^C^N and N^C are terdentate and bidentate cyclometallating aromatic ligands; L = monodentate pyridine ligand; X = heterocyclic N or cyclometallated aryl C; n = 0,1) is described and their reactions with thiolates are explored with the aim of producing new classes of thiol sensors. Thus, novel monometallic complexes of the type [Pt(N^C^N)(thiolate)] and [Ir(N^C^N)(N^C)(thiolate)] are reported as well as a novel series of dimers with the general structure [Ir(N^C)2(μ- thiolate)]2 and one example of a [Ir(N^C^N)(μ-thiolate)(thiolate)]2 dimer. The effect of the introduction of a thiolate ligand on the excited states of the Pt(N^C^N) complexes is also described. In addition, a series of luminescent compounds based on the dansyl group or iridium complexes are reported for use as bioimaging agents and their utility in cellular assays has been investigated. These probes incorporate molecular structures inspired by the ability of small molecules to mimic the activity of certain redox active proteins and hence have the potential to engage in disulfide exchange processes in vivo. These compounds have been shown to display acceptable uptake into cells without excessive cytotoxicity and have been used to obtain fluorescence microscopy images of live CHO cells

Technical Note: Could benzalkonium chloride be a suitable alternative to mercuric chloride for preservation of seawater samples?

Instrumental equipment unsuitable or unavailable for fieldwork as well as lack of ship space can necessitate the preservation of seawater samples prior to analysis in a shore-based laboratory. Mercuric chloride (HgCl2) is routinely used for such preservation, but its handling and subsequent disposal incur environmental risks and significant expense. There is therefore a strong motivation to find less hazardous alternatives. Benzalkonium chloride (BAC) has been used previously as microbial inhibitor for freshwater samples. Here, we assess the use of BAC for marine samples prior to the measurement of oxygen-to-argon (O2 / Ar) ratios, as used for the determination of biological net community production. BAC at a concentration of 50 mg dm−3 inhibited microbial activity for at least 3 days in samples tested with chlorophyll a (Chl a) concentrations up to 1 mg m−3. BAC concentrations of 100 and 200 mg dm−3 were no more effective than 50 mg dm−3 . With fewer risks to human health and the environment, and no requirement for expensive waste disposal, BAC could be a viable alternative to HgCl2 for short-term preservation of seawater samples, but is not a replacement for HgCl2 in the case of oxygen triple isotope analysis, which requires storage over weeks to months. In any event, further tests on a case-by-case basis should be undertaken if use of BAC was considered, since its inhibitory activity may depend on concentration and composition of the microbial community

Marine picoplankton size distribution and optical property contrasts throughout the Atlantic Ocean revealed using flow cytometry

Depth-resolved flow cytometric observations have been used to determine the size distribution and refractive index (RI) of picoplankton throughout the Atlantic Ocean. Prochlorococcus frequently showed double size distribution peaks centered on 0.75±0.25 and 1.75±0.25µm; the smallest peak diameters were ≤0.65µm in the equatorial upwelling with larger cells (∼0.95µm) in the surface layers of the tropical gyres. Synechococcus was strongly monodispersed: the smallest (∼1.5µm) and largest cells (∼2.25−2.50µm) were encountered in the lowest and highest abundance regions, respectively. Typical RI for Prochlorococcus was found to be ∼1.06, whereas for Synechococcus surface RI varied between 1.04–1.08 at high and low abundances, respectively

Literature From The Margins: a study on the relevance of zines

The scope of this research is to study the zine, which is a handmade booklet. The purpose is to reflect on what the zine is, discussing its format, reflecting on where it is inserted in the publishing market and what its cultural relevance is. This study is a theoretical and bibliographic research with a qualitative approach. We analyze three zines – Geração Beat, by Renato Alessandro dos Santos, O Ceifador de Privilégios, by Arthus Mehanna, and Libertemo-nos, by Melina Bassoli – in order to understand their format, the ways of production, where they are inserted, and their themes. Afterwards, we notice characteristics that contribute to the dissemination of culture and democratic values, thus becoming an object of great cultural relevance.Keywords: Zine. Marginal Literature. Publishing market

Isolation of viruses responsible for the demise of an Emiliania huxleyi bloom in the English Channel

This study used analytical flow cytometry (AFC) to monitor the abundance of phytoplankton, coccoliths, bacteria and viruses in a transect that crossed a high reflectance area in the western English Channel. The high reflectance area, observed by satellite, was caused by the demise of an Emiliania huxleyi bloom. Water samples were collected from depth profiles at four stations, one station outside and three stations inside the high reflectance area. Plots of transect data revealed very obvious differences between Station 1, outside, and Stations 2–4, inside the high reflectance area. Inside, concentrations of viruses were higher; E. huxleyi cells were lower; coccoliths were higher; bacteria were higher and virus:bacteria ratio was lower than at Station 1, outside the high reflectance area. This data can simply be interpreted as virus-induced lysis of E. huxleyi cells in the bloom causing large concentrations of coccoliths to detach, resulting in the high reflectance observed by satellite imagery. This interpretation was supported by the isolation of two viruses, EhV84 and EhV86, from the high reflectance area that lysed cultures of E. huxleyi host strain CCMP1516. Basic characterization revealed that they were lytic viruses approximately 170 nm–190 nm in diameter with an icosahedral symmetry. Taken together, transect and isolation data suggest that viruses were the major contributor to the demise of the E. huxleyi population in the high reflectance area. Close coupling between microalgae, bacteria and viruses contributed to a large organic carbon input. Consequent cycling influenced the succession of an E. huxleyi-dominated population to a more characteristic mixed summer phytoplankton community