The marine carbonate system along the northern Antarctic Peninsula: current knowledge and future perspectives.

Among the regions of the Southern Ocean, the northern Antarctic Peninsula (NAP) has emerged as a hotspot of climate change investigation. Nonetheless, studies have indicated issues and knowledge gaps that must be addressed to expand the understanding of the carbonate system in the region. Therefore, we focused on identifying current knowledge about sea-air CO2 fluxes (FCO2), anthropogenic carbon (Cant) and ocean acidification along NAP and provide a better comprehension of the key physical processes controlling the carbonate system. Regarding physical dynamics, we discuss the role of water masses formation, climate modes, upwelling and intrusions of Circumpolar Deep Water, and mesoscale processes. For FCO2, we show that the summer season corresponds to a strong sink in coastal areas, leading to CO2 uptake that is greater than or equal to that of the open ocean. We highlight that the prevalence of summer studies prevents comprehending processes occurring throughout the year and the net annual CO2 balance in the region. Thus, temporal investigations are necessary to determine natural environmental fluctuations and to distinguish natural variability from anthropogenically driven changes. We emphasize the importance of more studies regarding Cant uptake rate, accumulation, and export to global oceans.

Venomic and pharmacological activity of Acanthoscurria paulensis (Theraphosidae) spider venom.

In the present study we conducted proteomic and pharmacological characterizations of the venom extracted from the Brazilian tarantula Acanthoscurria paulensis, and evaluated the cardiotoxicity of its two main fractions. The molecular masses of the venom components were identified by mass spectrometry (MALDI-TOF-MS) after chromatographic separation (HPLC). The lethal dose (LD(50)) was determined in mice. Nociceptive behavior was evaluated by intradermal injection in mice and the edematogenic activity by the rat hind-paw assay. Cardiotoxic activity was evaluated on in situ frog heart and on isolated frog ventricle strip. From 60 chromatographic fractions, 97 distinct components were identified, with molecular masses between 601.4 and 21,932.3 Da. A trimodal molecular mass distribution was observed: 30% of the components within 500-1999 Da, 38% within 3500-5999 Da and 21% within 6500-7999 Da. The LD(50) in mice was 25.4 ± 2.4 µg/g and the effects observed were hypoactivity, anuria, constipation, dyspnea and prostration until death, which occurred at higher doses. Despite presenting a dose-dependent edematogenic activity in the rat hind-paw assay, the venom had no nociceptive activity in mice. Additionally, the venom induced a rapid blockage of electrical activity and subsequent diastolic arrest on in situ frog heart preparation, which was inhibited by pretreatment with atropine. In the electrically driven frog ventricle strip, the whole venom and its low molecular mass fraction, but not the proteic one, induced a negative inotropic effect that was also inhibited by atropine. These results suggest that despite low toxicity, A. paulensis venom can induce severe physiological disturbances in mice.

Partial characterization of a novel amphibian hemoglobin as a model for graduate student investigation on peptide chemistry, mass spectrometry, and atomic force microscopy.

Graduate students in chemistry, and in biological and biomedical fields must learn the fundamentals and practices of peptide and protein chemistry as early as possible. A project-oriented approach was conducted by first-year M.Sc and Ph.D students in biological sciences. A blind glass slide containing a cellular smear and an aqueous cellular extract were offered to the students. Qualitative and quantitative cell morphological parameters were analyzed by atomic force microscopy. The fractionation of the aqueous extract was conducted by reversed-phase chromatography followed by analysis of the isolated and partially purified proteins and peptides by mass spectrometry (MS). The proteins were treated by peptidases and the obtained peptide fragments were sequenced by de novo MS/MS, together with peptides already present in the extract. The most abundant protein fractions were identified as the alpha and beta chains of hemoglobin from an amphibian of the Leptodactylus genera. Two of the peptides sequenced by the students were synthesized by the solid-phase methodology, one of those being obtained by the split-and-pool library synthesis method. Thus, the students were able to learn some advanced principles and practices of protein chemistry and bionanotechnology in a 6-weeks project-oriented approach.