Indole-3-pyruvic acid as a potential luciferin

Indole-3-pyruvic acid luminesces in aerated dimethyl-sulfoxide solutions in the presence of potassium tert-butoxide. The chemiluminescence spectrum indicates the occurrence of multiple bands whose relative intensities change with time. This behaviour is connected with the presence of two forms of indole-pyruvic acid and with two different reactions, namely at the side chain giving indole-3-carboxaldehyde and at the indole nucleus giving ultimately a product of the N-formyl-kynurenine type.The results suggest that indole-pyruvate is a potential luciferin. This inference is strengthened by the fact that it can originate “in vivo” both indole-aldehyde and oxalate.The reaction at the indole nucleus is tentatively considered a model for tryptophan dioxygenase and related systems.     

A special issue of Biophysical Reviews dedicated to the 20th IUPAB (virtual) Congress “in” Foz do Iguaçu

The 20th IUPAB Congress took place online, together with the annual meetings of the Brazilian Biophysical Society and the Brazilian Society for Biochemistry and Molecular Biology, from the 4th to the 8th of October, 2021. The ten keynote lectures, 24 symposia, two poster sessions, and a series of technical seminars covered the full diversity of current biophysical research and its interfaces with other fields. The event had over 1000 attendees, with an excellent gender balance. Although the Americas dominated, there were also significant numbers of participants from Europe, Asia, and Africa.

The International Union of Pure and Applied Biophysics (IUPAB) came into existence in Stockholm in 1961 and has been a member of the International Science Council since 1966 (Solomon 1968). Its overall objectives aim to foster international collaboration in all aspects of biophysics and related areas and to catalyze the advancement of basic biophysical research as well as its many applications. Although IUPAB is active on many fronts, undeniably one of its showcase events is the IUPAB Congress, traditionally organized every three years in different locations worldwide. In 2021, the event was organized and run from Brazil, albeit for the very first time in a virtual format due to travel restrictions imposed by the COVID-19 pandemic. On this occasion, the Congress was organized in conjunction with the annual meetings of both the Brazilian Biophysical Society (SBBf, in its 45th edition) and the Brazilian Society for Biochemistry and Molecular Biology (SBBq, in its 50th edition). Even with the united forces of these well-established local societies, it turned out to be a bumpy ride to bring the event to fruition.Plans for the 20th Congress began in 2016, almost immediately after the decision to hold the event in Brazil, a cause championed by the then-president of the Brazilian Biophysical Society, Marcelo Morales. The original plans had the meeting to be held in the Cidade Maravilhosa (The Wonderful City) of Rio de Janeiro in October 2020. However, it soon became apparent that the political and economic difficulties that the State of Rio was facing at the time meant that it would be wise to search for an alternative venue. The previous experience of SBBq in organizing similar events in the city of Foz do Iguaçu, on the borders with Argentina and Paraguay, made this an obvious choice. Furthermore, the natural attraction of the spectacular Iguaçu waterfalls seemed to be an ideal compensation for Sugar Loaf Mountain, Copacabana beach, and the statue of Christ the Redeemer on Corcovado Mountain.Then came the pandemic. By mid-2020, it had become apparent that there were too many unknowns to make it possible to proceed with an in-person event in October of that year. It was decided to postpone the congress to 2021 but with a firm belief that things would be “back to normal.” Sweet delusion! As 2020 turned into 2021 and the severity and longevity of the pandemic became clearer and clearer (not to mention the abysmal performance of the Brazilian government in failing to rise to the challenge), the inevitable decision was taken to transform the event into an “on-line” congress. This was a first for both the local organizers and the IUPAB.The move to an online format immediately had an impact on the organization of the Young Scientist Program. This was initially envisaged to be a combination of formal and informal activities aimed at uniting about 40 early carrier scientists and post-docs for a couple of days prior to the main event in a stimulating atmosphere conducive to networking. Skillfully conceived, organized, and executed by Eneida de Paula (Campinas) and Eduardo Reis (São Paulo), this too had to be adapted to a “virtual reality.” The successful solution turned out to be a series of fortnightly thematic webinars, including a talk from a recognized authority in the field followed by three or four short presentations from the participants themselves (Table ​(Table1).1). The standard was extremely high and the YSP ended up being a highly effective warm-up to the congress itself. Furthermore, there was excellent geographical diversity among the participants with Europe, Africa, Asia, the Middle East, and both North and South America represented.Table 1Young Scientist Webinar Program

Visualisation and Quantitative Analysis of the Rodent Malaria Liver Stage by Real Time Imaging

The quantitative analysis of Plasmodium development in the liver in laboratory animals in cultured cells is hampered by low parasite infection rates and the complicated methods required to monitor intracellular development. As a consequence, this important phase of the parasite''s life cycle has been poorly studied compared to blood stages, for example in screening anti-malarial drugs. Here we report the use of a transgenic P. berghei parasite, PbGFP-Luc_con, expressing the bioluminescent reporter protein luciferase to visualize and quantify parasite development in liver cells both in culture and in live mice using real-time luminescence imaging. The reporter-parasite based quantification in cultured hepatocytes by real-time imaging or using a microplate reader correlates very well with established quantitative RT-PCR methods. For the first time the liver stage of Plasmodium is visualized in whole bodies of live mice and we were able to discriminate as few as 1–5 infected hepatocytes per liver in mice using 2D-imaging and to identify individual infected hepatocytes by 3D-imaging. The analysis of liver infections by whole body imaging shows a good correlation with quantitative RT-PCR analysis of extracted livers. The luminescence-based analysis of the effects of various drugs on in vitro hepatocyte infection shows that this method can effectively be used for in vitro screening of compounds targeting Plasmodium liver stages. Furthermore, by analysing the effect of primaquine and tafenoquine in vivo we demonstrate the applicability of real time imaging to assess parasite drug sensitivity in the liver. The simplicity and speed of quantitative analysis of liver-stage development by real-time imaging compared to the PCR methodologies, as well as the possibility to analyse liver development in live mice without surgery, opens up new possibilities for research on Plasmodium liver infections and for validating the effect of drugs and vaccines on the liver stage of Plasmodium.     

Development of tacrine clusters as positively cooperative systems for the inhibition of acetylcholinesterase

The synthesis of four tetra-tacrine clusters where the tacrine binding units are attached to a central scaffold via linkers of variable lengths is described. The multivalent inhibition potencies for the tacrine clusters were investigated for the inhibition of acetylcholinesterase. Two of the tacrine clusters displayed a small but significant multivalent inhibition potency in which the binding affinity of each of the tacrine binding units increased up to 3.2 times when they are connected to the central scaffold.     

Structure–function relationships of the peptide Paulistine: A novel toxin from the venom of the social wasp Polybia paulista

Background

The peptide Paulistine was isolated from the venom of wasp Polybia paulista. This peptide exists under a natural equilibrium between the forms: oxidised — with an intra-molecular disulphide bridge; and reduced — in which the thiol groups of the cysteine residues do not form the disulphide bridge. The biological activities of both forms of the peptide are unknown up to now.

Methods

Both forms of Paulistine were synthesised and the thiol groups of the reduced form were protected with the acetamidemethyl group [Acm-Paulistine] to prevent re-oxidation. The structure/activity relationships of the two forms were investigated, taking into account the importance of the disulphide bridge.

Results

Paulistine has a more compact structure, while Acm-Paulistine has a more expanded conformation. Bioassays reported that Paulistine caused hyperalgesia by interacting with the receptors of lipid mediators involved in the cyclooxygenase type II pathway, while Acm-Paullistine also caused hyperalgesia, but mediated by receptors involved in the participation of prostanoids in the cyclooxygenase type II pathway.

Conclusion

The acetamidemethylation of the thiol groups of cysteine residues caused small structural changes, which in turn may have affected some physicochemical properties of the Paulistine. Thus, the dissociation of the hyperalgesy from the edematogenic effect when the actions of Paulistine and Acm-Paulistine are compared to each other may be resulting from the influence of the introduction of Acm-group in the structure of Paulistine.

General significance

The peptides Paulistine and Acm-Paulistine may be used as interesting tools to investigate the mechanisms of pain and inflammation in future studies.